WO2022184266A1

WO2022184266A1 - A sensor

Info

Publication number: WO2022184266A1
Application number: PCT/EP2021/055585
Authority: WO
Inventors: Mikko Turunen; Petri JÄRVINEN; Pekka Iso-Ketola
Original assignee: Forciot Oy
Priority date: 2021-03-05
Filing date: 2021-03-05
Publication date: 2022-09-09

Abstract

The invention relates to a sensor arrangement comprising a first stretchable sensing element (301) and a stretchable electrically conductive wiring (400), which are able to stretch at least 5 %. The sensor arrangement further comprises an electronic arrangement (120) electrically coupled to the first stretchable sensing element (301) via the stretchable electrically conductive wiring (400), which electronic arrangement (120) is configured to obtain a first signal from the first stretchable sensing element (301). The sensor arrangement further comprises an illumination arrangement comprising a light source (10), wherein at least part of light from the light source (10) is guided via and/or through at least one layer of the sensor from the light source (10) on to a first surface of the sensor in order to illuminate at least part of the first surface of the sensor. The invention further relates to a product comprising a sensor arrangement.

Description

A SENSOR

Technical field

The invention relates to sensors. The invention relates to an arrangement compris ing a sensor. The invention relates to a product comprising a sensor. The invention relates to a use of a sensor.

Background

Interest in well-being as well as safety and comfort has increased. This has resulted in many personal devices having a human-machine interface (HMI).

Personal monitoring devices may have sensors. Such sensors can be embedded, for example, in clothing, furniture and vehicles. In such sensors there are several interrelated problems. For example, measurements of an electrode should not affect the measurement result of another electrode. Furthermore, it would be beneficial that multiple measurements could be measured in parallel, i.e. simultaneously or substantially simultaneously. Furthermore, the sensor should be installable for dif ferent surfaces. Still further, the sensor should be mechanically reliable, and easy to use.

Summary

It is an aim of the present invention to provide an improved sensor arrangement. Further, it is an aim of the present invention to provide a product comprising a sensor arrangement attached to said product.

Aspects of the invention are characterized by what is stated in the independent claims. Preferred embodiments are disclosed in the dependent claims. These and other embodiments are disclosed in the description and figures.

The novel sensor arrangement may provide an improved illumination solution for stretchable and/or deformable sensors. Illumination solutions have been very chal lenging for stretchable and deformable sensors. Conventionally, it has been chal lenging to obtain reliable measuring data from stretchable (and particularly from de formable) sensors. Further, reliability of measurements may be compromised if some materials of a stretchable and/or deformable sensor are changed for illumina tion solution. Thus, it has been very challenging to provide an illumination solution for stretchable and/or deformable sensors, and still have reliable measurements. Further, typically, illumination solutions for rigid sensors may not work with stretch able and/or deformable sensor due to challenging features of the stretchable and/or deformable sensors.

The sensor may be a touch sensor. The sensor may be a force sensor. The sensor may be a touch and force sensor.

The sensor should be able to measure, reliable, even if the sensor has the illumina tion solution within the sensor arrangement. If the sensor has a deformable layer, such as a foam layer, an illumination solution may become even more challenging than an illumination solution for other kind of sensors.

This application may particularly relate sensors comprising an illumination arrange ment. Thus, the sensor arrangement may further comprise the illumination arrange ment providing a light and a light guide in order to form a visible illuminated symbol by using light.

The novel solution may have several technical effects. First, easiness of an instal lation of the sensor may be substantially improved when the sensor provides the means for forming a visible illuminated symbol. In this embodiment, the light source and means for providing symbols do not need to be placed so accurate on an instal lation surface, because the needed accuracy may be obtained by merely installing the sensor onto a surface. This may have several advantages as an installation of a stretchable and/or deformable sensor may be a quite challenging procedure.

If part of means for forming a symbol are fixed on the installing surface, and the stretchable and/or deformable sensor is to be installed e.g. exactly below said part of means for forming a symbol, the installing procedure might become too challeng ing for an installer. Thus, advantageously, the sensor arrangement provides means for forming a visible illuminated symbol in order to improve easiness of installation the stretchable and/or deformable sensor having the illumination solution. Further, in this embodiment, visible illuminated symbol may stay on a predetermined place, even during a usage of the soft stretchable and/or deformable sensor. Moreover, an illuminated symbol formed by the sensor arrangement may, in use, have the same location in relation to a measuring area (all the time). Thus, reliability of measure ments may stay at a high level, even if the sensor is not fixed to a top surface in an unmovable way but the top surface is able to move (in relation to measurement area) a little bit over a time.

In an embodiment, a light mask forming a symbol can be e.g. printed on a surface of the sensor. In an advantageous embodiment, light mask comprises and/or is made of a conductive material. The light mask may form e.g. at least part of an electrically permeable and/or conductive layer. In an embodiment, the light mask is formed by printing the light mask at a manufacturing step wherein electrically con ductive printable areas are formed.

In an embodiment, one or more than one electrically permeable and/or conductive area of the sensor works as a light mask. Thus, in this embodiment, a separate light mask may not be needed, but said area(s) of the sensor may further form the light mask, or at least part of the light mask.

The novel sensor may be used in vehicles. Further, the novel sensor may be used in furniture, and/or for other products.

The novel sensor arrangement may comprise a sensor suitable to be attached to a curved surface, the sensor arrangement comprising a first stretchable sensing ele ment, e.g. an electrode, and a stretchable electrically conductive wiring. The first stretchable sensing element may be able to stretch at least 5 % at a temperature of 20°C without breaking, and the stretchable electrically conductive wiring may be able to stretch at least 5 % at a temperature of 20°C without breaking. The sensor arrangement can further comprise an electronic arrangement electrically coupled to the first stretchable sensing element via the stretchable electrically conductive wir ing, which electronic arrangement can be configured to obtain a first signal from the first stretchable sensing element. The sensor can further comprise an illumination arrangement comprising a light source. At least part of light from the light source can be guided via and/or through at least one layer of the sensor from the light source on to a first surface of the sensor in order to illuminate at least part of the first surface of the sensor.

The sensor can be configured to form said first signal due to a touch of a user on the illuminated visible symbol. A product can comprise a sensor arrangement attached to said product, wherein the sensor can comprise a first stretchable sensing element, and a stretchable elec trically conductive wiring. The first stretchable sensing element can be able to stretch at least 5 % at a temperature of 20°C without breaking. Further, the stretch able electrically conductive wiring can be able to stretch at least 5 % at a tempera ture of 20°C without breaking. Said sensor arrangement of the product can further comprise an electronic arrangement electrically coupled to the first stretchable sens ing element via the stretchable electrically conductive wiring, which electronic ar rangement can be configured to obtain a first signal from the first stretchable sensing element. The sensor arrangement of the product can further comprise an illumina tion arrangement comprising a light source, wherein at least part of light from the light source is guided via and/or through at least one layer of the sensor from the light source on to a first surface of the sensor in order to illuminate at least part of a surface of the product, thereby forming a visible illuminated symbol on the surface of the product.

The sensor may comprise one or more layers that are stretchable and elastic stretchability improves deformability of the sensor. Further, the sensor may be formed from layers, hence, it may be manufactured easily and cost efficiently, e.g. without an expensive 3D mold. Moreover, thanks to the stretchability of the sensor, the sensor comprising or consisting of layer(s) may be installed on a curved surface. Further, the sensor may measure reliably while installed e.g. on a curved surface. Moreover, thanks to the stretchability of the sensor, the sensor comprising or con sisting of layers may be installed on a changeable surface, and measure reliably therein. The changeable surface may be e.g. a surface of a furniture or a vehicle.

Further, the stretchable sensing element(s) can be attached to at least one stretch able layer. The stretchable sensing element is preferably an electrode.

The light from the light source can be guided from a side of the sensor on to the first surface of the sensor. Alternatively, or in addition, the light from the light source can be guided from a second side of the sensor through the sensor onto the first surface of the sensor.

At least one stretchable sensing element may be an electrode. Preferably, each stretchable sensing element is an electrode. The sensor may comprise a light mask. The light mask is preferably a stretchable light mask which is able to stretch at least 5 % at a temperature of 20°C.

The sensor may comprise a flexible and stretchable layer, which is able to stretch at least 5 % at a temperature of 20°C without breaking. Alternatively or in addition, the sensor may comprise an elastic, deformable layer having a Young’s modulus of at least 0.01 MPa and a first yield strain at least 10 per cent at a temperature of 20°C. The sensor may comprise a layer which a flexible and stretchable, elastic deformable layer. The sensor may comprise an electrically permeable and/or con ductive layer.

Any and each of the above mentioned layers may comprise

- One or more than one translucent area, and/or

- One or more than one transparent area, and/or

- prisms.

Therefore, the sensor may have at least one transparent area having a transparency value in a range between 10% and 98%.

The sensor may have at least one translucent area having a transparency value in a range between 10% and 98%, wherein more than 10% of the light deviates from the incident beam by at least 2.5 degrees, when passing through at least material layer of the sensor.

The transparent and/or translucent area(s) may be configured to work as a light guide. In an embodiment, translucent area(s) may be used in order to decrease number of light sources, as the translucent area may scatter light evenly to a surface of the sensor.

The sensor may comprise a first elastic, deformable layer, which layer may be a transparent and/or translucent layer, or have one or more transparent and/or trans lucent areas. Further, the sensor may comprise a flexible and stretchable layer, which layer may be a transparent and/or translucent layer, or have one or more transparent and/or translucent areas. Still further, the sensor may comprise a first electrically permeable and/or conductive layer, which layer may be a transparent and/or translucent layer, or have one or more transparent and/or translucent areas. The sensor may also comprise one or more other layers comprising transparent and/or translucent areas. For example, the sensor can comprise a second elastic, deformable layer, which layer may be a transparent and/or translucent layer, or have one or more transparent and/or translucent areas.

At least part of the light from the light source can be configured to go through said at least one transparent and/or translucent area.

In an advantageous embodiment, the sensor comprises a transparent and/or trans lucent adhesive. Thus, it is possible to improve transparency of the sensor while providing reliable means for attaching layers.

The first stretchable sensing element may comprise a transparent area and/or a translucent area.

The sensor may comprise a first elastic, deformable layer, which layer may comprise prisms. Further, the sensor may comprise a flexible and stretchable layer, which layer may comprise prisms. Still further, the sensor may comprise a first electrically permeable and/or conductive layer, which layer may comprise prisms.

The sensor may comprise at least one layer comprising perforations and/or open ings. More preferably, the sensor comprises at least one layer comprising integrated prisms and/or transparent areas and/or translucent areas.

The stretchable electrically conductive wiring may comprise e.g. a conductive ink. The first stretchable sensing element may comprise or may be made of a non-trans- parent conductive ink.

The stretchable electrically conductive wiring may comprise one or more transpar ent and/or translucent areas having a transparency in a range between 10% and 98%.

The sensor may be a force sensor, or a touch sensor, or force and touch sensor.

The sensor may comprise a light guide, and a measuring area of the sensor may be adjacent to the light guide. Alternatively, a measuring area of the sensor overlaps the light guide. Alternatively, or in addition, the measuring area of the sensor is at least partly on the light guide.

The light source may comprise at least one LED, and/or at least one display.

In an advantageous embodiment, the sensor is one of the following:

- a capacitive sensor,

- a resistive sensor, or

- a piezoresistive sensor.

Most preferably, the sensor may be the capacitive sensor.

The sensor arrangement may further comprise:

- analyzing means configured to determine a calibrated value based on the obtained first signal and assembly compensation coefficients, which assem bly compensation coefficients are based on

- material compensation coefficients, and

- at least one other measured signal of the sensor, which said at least one other measured signal was measured in an installing position when no object to be measured had an effect on the sensor.

The sensor arrangement my comprise a temperature sensor, and the material com pensation coefficients may include an effect of temperature on the first signal. Al ternatively, or in addition, the sensor arrangement comprises a moisture sensor, and the material compensation coefficients include an effect of moisture on the first signal of the sensor.

The material compensation coefficients may include

- an effect of material(s) of the sensor on the first signal of the sensor and/or

- an effect of a structure of the sensor on the first signal of the sensor.

The analyzing means may further be configured to

- obtain said first signal when no object to be measured has an effect on the sensor,

- compare said first signal to at least one other signal stored to a memory, which said at least one other signal was obtained when the sensor was in stalled to the current surface, and - determine whether the installing surface in which the sensor is positioned is still in suitable condition based on a difference between the first signal and the stored signal.

The sensor arrangement may be configured to

- determine material compensation coefficients (181 ) on a planar surface, and/or

- use the material compensation coefficients stored to a memory.

In an embodiment,

- the sensor arrangement is configured to determine the assembly compensa tion coefficients in an installing position of the sensor when no object to be measured has an effect on the sensor, and/or

- the assembly compensation coefficients are stored to memory of the elec tronic arrangement.

The sensor may further comprise a second stretchable sensing element arranged a first distance apart from the first stretchable sensing element, wherein the electronic arrangement is further coupled to the second stretchable sensing element via the wiring, and configured to obtain a second signal from the second stretchable sens ing element.

In an advantageous embodiment, the sensor is shaped, or at least capable of being shaped into

- a double curved form and/or

- a curved form, without breaking, and without plastic deformation

In an embodiment, the sensor comprises

- elastic, deformable layer and

- stretchable layer in such a way that the stretchable layer, the stretchable electrode(s), and the elec trically conductive wiring are left on a same side of the elastic deformable layer.

In an embodiment, the sensor comprises an insulating layer and the sensor fur ther comprises the electrically permeable and/or conductive layer, and the electronic arrangement is preferably electrically coupled to the electrically permeable and/or conductive layer.

The sensor arrangement may be attached to its position, for example,

- mechanically, and/or

- by using an adhesive.

Advantageously, but not necessarily, each stretchable sensing element is a stretch able electrode.

Advantageously, the product is a vehicle, for example a car.

The sensor may be used, e.g., for Human-Machine Interface (HMI) for touch and/or pressure sensor - based operation of a vehicle’s functions.

Thanks to the novel sensor, light can be guided via or through one or more layers of the sensor.

If the sensor comprises the transparent and/or translucent areas, it may not need to have holes or a photoconductor for illuminating a surface of the sensor. Said one or more transparent and/or translucent areas may not merely pass the light through the transparent and/or translucent area(s) but at least one transparent and/or trans lucent area may work as a light guide by distributing light from the light source to a particular area that requires illumination for indicating a certain area on a surface of the sensor. The one or more transparent and/or translucent areas may form, for example, one or more lines, and/or one or more symbols on the surface of the sen sor. Alternatively, or in addition, the sensor may comprise prisms.

Further, the sensor may comprise a top layer which comprises one or more non transparent areas in order to form a light mask.

The light mask together with the light guide of the sensor may form symbol(s), line(s), letter(s) and other indicating area(s) on a surface of the sensor for a user of the sensor.

The novel solution can also be used to determine whether the installing surface in which the sensor is positioned is still in suitable condition. In this case, the analyzing means can be configured to obtain at least one signal from the sensing element(s) when no object to be measured has an effect on the sensor. Said signal(s) can be compared to at least one other signal stored to a memory, which said stored signal was obtained when the sensor was installed to the current surface. Further, the dif ference between the measured signal and the stored signal can be used to deter mine whether the installing surface in which the sensor is positioned is still in suita ble condition.

The sensor arrangement can comprise a sensor suitable to be attached to a curved surface so that the sensor is able to indicate a certain area on a surface of the sensor. The sensor is preferably able to bend between a planar shape and a curved shape without breaking.

In an embodiment, the sensor may comprise

- a first layer,

- a first stretchable sensing element attached to the first layer, and

- a stretchable electrically conductive wiring.

The electronic arrangement may be configured to send an output signal (S_out), the output signal (So_ut) being indicative of the first signal and/or the calibrated value of the first signal.

At least one layer of the sensor can have a Young’s modulus at least 0.01 MPa and a first yield strain at least 10 per cent at a temperature of 20°C. Said layer can com prise one or more transparent and/or translucent areas having a transparency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably in a range between 55% and 98%, and most preferably in a range be tween 70% and 98%.

The sensor may comprise at least one of:

- an elastic, deformable layer,

- an electrically permeable and/or conductive layer, and

- a flexible and stretchable layer.

The sensor can comprise an illumination arrangement wherein light is configured to go through the transparent and/or translucent area(s) of at least one layer. One or more transparent and/or translucent areas may work as a light guide by distributing light from the light source to a particular area that requires illumination for indicating a certain point on a surface of the sensor.

At least part of the light can be configured to go through the sensor from the light source on to the surface of the sensor.

The light source may comprise

- one or more than one LED, and/or

- one or more than one display.

The stretchable electrically conductive wiring can comprise one or more transparent and/or translucent area having a transparency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably between 55% and 98%, and most preferably in a range between 70% and 98%, wherein light is con figured to go through one or more transparent and/or translucent areas of the wiring.

The first stretchable sensing element can be made of a non-transparent, conductive ink. Alternatively, the first stretchable sensing element can comprise transparent and/or translucent, conductive material.

The sensor can comprise a flexible and stretchable layer comprising one or more transparent and/or translucent areas having a transparency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably between 55% and 98%, and most preferably in a range between 70% and 98%, wherein light is configured to go through one or more transparent and/or translucent areas of the flexible and stretchable layer.

The sensor can further comprise a first electrically permeable and/or conductive layer comprising one or more transparent and/or translucent areas having a trans parency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably between 55% and 98%, and most preferably in a range be tween 70% and 98%, wherein light is configured to go through one or more trans parent and/or translucent areas of the first electrically permeable and/or conductive layer.

The sensor arrangement can comprise analyzing means configured to determine a calibrated value based on assembly compensation coefficients and a signal measured by the sensor. The assembly compensation coefficients can be based on material compensation coefficients, and at least one measured signal in an installing position of the sensor when no object to be measured has an effect on the sensor.

The sensor may further comprise a second stretchable sensing element arranged a first distance (di_, di ,301 ,302) apart from the first stretchable sensing element, wherein the electronic arrangement is further coupled to the second stretchable sensing el ement via the wiring, and configured to obtain a second signal from the second stretchable sensing element. The second stretchable sensing element may com prise non-transparent conductive ink. The second stretchable sensing element may comprise transparent and/or translucent, conductive material(s).

The analyzing means may comprise a processor, and the electronic arrangement may further comprise transmitting means, such as a wireless component, and op tionally at least one memory component.

The electronic arrangement may comprise an electronic chip electrically coupled to the first sensing element, and the analyzing means may be positioned in the elec tronic chip.

The sensor arrangement may be configured to determine filtered values from the obtained signals, and the determination of the calibrated value(s) may be based on the filtered values.

The sensor arrangement can be attached to its position mechanically and/or by us ing e.g. an adhesive. In an embodiment, the sensor arrangement is attached to its position removably.

The sensor may comprise an electronic arrangement comprising a circuit board, preferably a flexible circuit board. The circuit board may be electrically coupled to the first sensing element. At least one electronic chip may be attached to the circuit board.

The sensor, or at least most of the sensor may be flexible, stretchable, and con formable. The novel solution makes it possible to have reliable solution on a com plex surface. Moreover, easiness of manufacturing process may be improved, as the novel sensor may be manufactured as a planar layered structure. Further, the novel solution makes it possible to indicate a certain point on a surface of the sensor by using an illumination arrangement. The illumination arrangement may be used to form symbol(s), line(s) and/or other area(s) on the surface of the sensor. Brief description of the drawings

In the following, the present invention will be described in more detail with reference to the appended drawings, in which

Figs 1 a-h show, in a side view, examples of a part of a sensor arrangement,

Figs 2 shows an example of a part of a sensor arrangement,

3a-b illustrate examples of operating principles of a system comprising the sensor,

Fig 4 shows, in a side view, an example of a part of a sensor arrangement,

Fig. 5a illustrates examples of measurement ranges on a planar surface,

Fig. 5b illustrates examples of measurement ranges on a non-planar surface after conformable installation, if the sensor is not reliable calibrated,

Fig. 6a illustrates an example of material compensation coefficients,

Fig. 6b illustrates an example of the material compensation coefficients and a third curve,

Fig. 6c illustrates an example of assembly compensation coefficients,

Fig. 7a illustrates an example of uncalibrated measurements,

Fig. 7b illustrates an example of material compensation coefficients,

Fig. 7c illustrates an example of calibrated measurements on a planar surface,

Fig. 8a illustrates an example of measurements after installation on a non-pla- nar surface, before a calibration,

Fig. 8b illustrates an example of assembly compensation coefficients, and

Fig. 8c illustrates an example of measurements after assembly compensation, and

Figs 9, 10a-c, and 11a-b

Illustrate some examples of a sensor.

In the figures, the direction Sz indicates a direction of a thickness of the sensor structure. The directions Sx and Sy are perpendicular to each other and to Sz. The figures illustrate the sensor in substantially planar form but, since the sensor is stretchable and/or deformable, it may be shaped to another form. Therefore, the directions Sx, Sy, and Sz may depend on location, when the sensor is not planar. Detailed description

The following reference numbers are used in this application:

10 light source,

100 sensor,

101 first side of the sensor, i.e. , surface side of the sensor,

102 second side of the sensor, i.e., bottom side of the sensor,

103 side of the sensor,

110 transparent and/or translucent area(s), and/or other illuminating means for guiding light,

111 illuminating means for guiding light, e.g. integrated prisms,

112 light mask for forming a symbol,

120 electronic arrangement,

130Afirst elastic, deformable layer,

130Bsecond elastic, deformable layer,

140 first electrically permeable and/or conductive layer,

142 second electrically permeable and/or conductive layer,

150 elastic and stretchable layer,

181 material compensation coefficients,

182 assembly compensation coefficients,

183 third reference values, third curve,

200 a flexible and stretchable layer,

201 top layer,

300 sensing element(s), e.g. stretchable electrode(s),

301 first sensing element, e.g. first stretchable electrode,

302 second sensing element, e.g. second stretchable electrode,

300, 301, 302, 304, 311, 315, 316, 321, 322 sensing element, such as stretchable electrode,

400 electrically conductive wiring, e.g. conductive ink,

401 first electrically conductive wire,

402 second electrically conductive wire,

400, 401,402, 404 electrically conductive wire,

500 external unit, such as an external control unit or a cloud service unit,

510 electronic chip, such as a microchip, 550 external control unit,

570 cloud service unit, and

700 circuit board, e.g. flexible circuit board. Figures show some embodiments for a sensor comprising illumination arrangement.

In an embodiment, the sensor may comprise transparent and/or translucent area(s). Further, one or more layers may be made of transparent and/or translucent mate rials). Alternatively, or in addition, the sensor may comprise e.g. integrated prisms. Thus, a light guide may be formed for the sensor. The light guide may be used to form symbol(s) and/or line(s) and/or point(s) on the surface of the sensor.

In this application “a sensor” refers to a device which produce an electrical signal corresponding to changes in inputs. The sensor may be activated, for example, by a touch. The term “sensor” particularly refers to a sensor, which can be attached to a curved object and be shaped according to the surface of the object.

In this application, the term “sensing element” may refer to any kind of sensing ele ment usable for measurements. The sensing element is preferably an electrode.

The sensor may be attachable, for example, to a curved surface and to a double curved surface, i.e. , to a surface that curves in two directions. Thus, the sensor may be shaped according to the intended application. The term “an illumination arrangement” may refer to a solution comprising a light source. Thanks to the illumination arrangement, an area on a surface of the sensor may be illuminated. Thus, a certain area forming e.g. symbol(s) and/or line(s) may be shown on the surface of the sensor and/or a product comprising the sensor. Advantageously, the illumination arrangement of the sensor comprises a light source. The illumination arrangement may further comprise a light guide comprising one or more layers comprising

- one or more than one transparent area, and/or

- one or more than one translucent area, and/or

- one or more than one prism. Thus, the illumination arrangement may comprise a light guide in the sensor. The light source may comprise one or more than one LED (light emitting diodes) and/or one or more than one display.

The illumination arrangement is preferably a stretchable illumination solution, wherein said one or more transparent and/or translucent areas are stretchable.

The sensor can be conformable. The term “conformable” refers to material that is at least flexible and stretchable and preferably also compressible.

In this application, the term “flexible” means that a planar flexible material or a planar flexible structure can be bent to a radius of curvature, which said radius of curvature is 5 times a thickness of said flexible material, without breaking the material at a temperature of 20°C. Moreover, the flexible material can be thereafter turned back to the planar form at a temperature of 20°C without breaking the material; or it may spontaneously turn back to planar form without breaking.

The sensor may comprise one or more layers comprising one or more flexible trans parent and/or translucent areas. Further, the sensor may comprise one or more conformable transparent and/or translucent areas. Alternatively or in addition, the sensor may comprise one or more conformable layers comprising prisms.

In this application, the term “stretchable” means that the stretchable material or ob ject can be stretched, at a temperature of 20°C, at least 5% without breaking, pref erably at least 10% in a reversible manner without breaking. In particular, a layer of stretchable material may be stretched, at a temperature of 20°C, by at least 5%, preferably at least 10 % in a reversible manner a direction that is perpendicular to the direction of thickness of the layer. The reversibility of the stretching is preferably spontaneous, i.e. elastic.

Therefore, the sensor may comprise one or more layers comprising one or more stretchable transparent and/or translucent areas. Alternatively or in addition, the sensor may comprise one or more stretchable layers comprising prisms.

In this application the term “compressible” means that the compressible material (or the compressible layer or another object) can be compressed, at a temperature of 20°C, by at least 10 % in a reversible manner. In particular, compressible material can be compressed by at least 10 % in a reversible manner in the direction of thick ness of the layer. The reversibility of the compression is spontaneous, i.e. elastic. A Young’s modulus of a compressible layer may be less than 1 GPa.

The sensor may comprise one or more layers comprising one or more compressible transparent and/or translucent areas. Alternatively or in addition, the sensor may comprise one or more compressible layers comprising prisms.

In this application the term “material compensation coefficients 181” refers to cali bration coefficients that can be used to characterize materials and/or a structure of the sensor. The material compensation coefficients can include an effect of temper ature and/or moisture on the measured signals of the sensor. The material compen sation coefficients can be used to obtain calibrated values from signals of the sensor on a planar surface. Preferably, the material compensation coefficients are used to form assembly compensation coefficients, which assembly compensation coeffi cients can be used to obtain calibrated values from signals of the sensor, not only on a planar surface, but also on a non-planar surface. The material compensation coefficients can be stored to memory of the sensor arrangement, for example, dur ing a manufacturing process of the sensor. In an embodiment, the material compen sation coefficients are formed or calibrated after the manufacturing process of the sensor. Thus, the term “material compensation coefficients” can also refer to mate rial compensation coefficients which are formed and/or calibrated after the manu facturing process of the sensor.

In this application the term “assembly compensation coefficients 182” refers to cali bration coefficients that can be used to calibrate a measured signal. The assembly compensation coefficients typically use the material compensation coefficients to obtain reliable data. Thus, a calibration process of the sensor does not need to be done on different temperatures and/or moistures etc., because the effect of those on the signals is typically within the material compensation coefficients. Thus, the calibration process of the sensor to obtain the assembly compensation coefficients may be done within a second. Furthermore, thanks to the novel sensor, values of interest can be reliable measured after the fast calibration process.

The terms transparency and translucency may not be used as synonyms, but they may have different meanings. Translucency may refer to solutions wherein light can go through a material, but e.g. a symbol below a translucency material may not be easily readable. Transparency may refer to solutions wherein light can go through a material so that a symbol, such as a letter on a display, may be readable through the material.

In this application, the term “transparent area” refers to an area having a transpar ency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably in a range between 65% and 98%, or in a range between 80% and 98%, and most preferably equal to or more than 90% and equal to or less than 98%, measured according to standard ASTM D1746-15. The higher is the transpar ency value of the transparent area, the easier the light can go through said area. Therefore, a light source, such as LED(s), may have lower energy consumption when the transparent area(s) have higher transparency values. Further, a symbol, such as a letter on a display, may be readable through the material. Preferably, in the transparent area, equal to or less than 10% of light from the light source that pass through a layer deviates from the incident beam by equal to or more than 2.5 degrees. This may have a technical effect of providing clear transparent material, hence, e.g. a display below the material might be readable.

In this application, the term “translucent area” refers to an area having a transpar ency in a range between 10% and 98%, preferably in a range between 40% and 98%, more preferably in a range between 65% and 98%, or in a range between 80% and 98%, and most preferably equal to or more than 90% and equal to or less than 98%, measured according to standard ASTM D1746-15. Therefore, a light source, such as LED(s), may have lower energy consumption when the translucent area(s) have higher transparency values. Further, preferably, in the translucent area, more than 10% of light deviates from the incident beam by at least 2.5 degrees when passing through at least one material layer of the sensor. This may have a technical effect of providing an improved, evenly distributed lightning on a surface of a prod uct. For example, a foam may be used to obtain material having said angle. Flow- ever, due to said angle, e.g. a display below the material might not be easily read able. This feature might be measured according to standard ASTM D1003-13.

In order to obtain predetermined transparency and/or translucency level for the sen sor, the sensor may comprise e.g. optical clear adhesive(s) OCA.

In this application, the term “light mask” refers to an area which at least reduces an amount of light that is able to go through said area. The light mask may be a non- transparent and/or non-translucent area of the sensor. The light mask may form a part of a top surface of the sensor.

The illumination arrangement may comprise:

- one or more than one layer comprising o one or more transparent and/or translucent areas, and/or o prisms,

- one or more than one layer comprising areas forming a light mask, and

- one or more light sources, such as led(s) and/or displays,

The sensor is preferably conformable and/or comprises at least one conformable layer. The sensor may comprise at least two conformable layers, e.g. at least one conformable layer as a substrate and at least one conformable layer for a sensing element and/or wiring. Thus, the sensor can be easily installed to a curved surface.

A planar conformable layer may be flexible as indicated above and stretchable in a direction of the plane of the planar conformable layer; and preferably also compress ible in the direction of its thickness as detailed above.

One or more conformable layers may comprise one or more transparent and/or translucent areas and/or prisms. A planar conformable layer can typically be ar ranged to conform a surface of a hemisphere of a sphere having a radius of 10 cm (or less) at a temperature of 20°C without breaking. Typically, a planar conformable layer can be arranged to conform a surface of a hemisphere having a radius of 10 cm (or less) at a temperature of 20°C without introducing significant plastic (i.e. irreversible) deformations to the material. Herein the term “significant” means that, when arranged on the hemisphere, the elastic strain of the conformable material is greater than the plastic strain thereof.

For example Figures 1a-h, 2 and 4 disclose examples of a sensor, or a part of the sensor. Figures 3a-b disclose examples of operating principles of a system com prising the sensor. Figures 5a-b disclose examples of measurement areas of sens ing elements on a planar surface (Fig. 5a) and on non-planar surface (Fig. 5b). Fig ures 6a-8c disclose some examples of coefficients and measurements. Figures 7a and 8a illustrate some examples of uncalibrated measurements, Figures 7b and 8b illustrate some examples of coefficients, and Figures 7c and 8c illustrate some examples after a calibration of the sensor. Fig. 9, Figs 10a-c, and Figs 11a-b illus trate examples of a sensor arrangement.

The sensor may comprise

- one or more layers comprising one or more transparent and/or translucent areas, and/or

- one or more layers comprising perforations, and/or

- one or more layers comprising prisms.

The sensor may comprise one or more layers comprising one or more transparent and/or translucent areas, such as 1 to 4 layers comprising transparent and/or trans lucent area(s). The sensor may comprise equal to or more than 1 layer comprising transparent and/or translucent area(s), more preferably equal to or more than 2 lay ers comprising transparent and/or translucent area(s), and most preferably equal to or more than 3 layers comprising transparent and/or translucent area(s). Further, the sensor may comprise equal to or less than 6 layers comprising transparent and/or translucent area(s), more preferably equal to or less than 5 layers comprising transparent and/or translucent areas, and most preferably equal to or less than 4 layers comprising transparent and/or translucent areas.

The transparent and/or translucent area(s) may form e.g. line(s) or point(s) indicat ing certain area(s) on the sensor. The transparent and/or translucent area(s) may be used to obtain reliable sensor having an illumination arrangement.

In addition or alternatively to the transparent and/or translucent areas, the sensor may comprise other means for the light guide, such as a layer comprising prisms. Thanks to the prisms, it may be possible to obtain a reliable sensor having an illu mination arrangement. In an advantageous embodiment, a layer comprising prims is between a top layer of the sensor and the stretchable sensing element(s) 300 of the layer.

The prisms may be particularly suitable for sensor arrangements wherein at least one light source is on the side of the sensor. The transparent and/or translucent areas may be particularly suitable for sensor arrangements wherein at least one light source is on the second side of the sensor, i.e. , below the sensor. Further, the light mask 112 may be used to form e.g. line(s) or point(s) indicating certain area(s) on the sensor. The light mask may comprise e.g. ink on a first surface 101 of the sensor.

In an embodiment, a sensor having material compensation coefficients on its memory may be installable to many different kinds of surfaces. The sensor can be against and/or attached to a second surface, i.e. , in its installing position. The sensor 100 may be secured in its installing position removably or permanently with a me chanical support. In addition, or alternatively, the securing can be provided by using an adhesive. Further, the illumination arrangement may be used to provide e.g. line(s) or point(s) indicating certain area(s) on the sensor.

If the sensor is removably attached to a first surface, the sensor 100 may be rein stalled to another object, even if said another object has a differently shaped sur face. Thus, the sensor can be re-installable, for example, from a curved surface to a double curved surface. In this case, the sensor 100 is preferably installed with a mechanical support, without permanent adhesive(s).

In an embodiment, the sensor 100 comprises

- at least one stretchable sensing element 300, and

- electrically conductive wiring 400, and

- optionally, a first layer 130A, 130B, 150, 200, 140, 142.

The sensor 100 can comprise a first sensing element 301 coupled to a first electri cally conductive wire 401. The sensing element 300 may form a part of the wiring 400. The first sensing element 301 and/or at least part of the first electrically con ductive wire may be made of a transparent and/or translucent material. Thus, it is possible to provide a sensor with complex indicating areas.

In an embodiment, at least one sensing element 300 may comprise, or it may be made of, a transparent and/or translucent material. The sensing element(s) may comprise or consist of a transparent and/or translucent, stretchable, conductive ma terial. The sensing element may comprise or consist of PEDOT:PSS (i.e. poly(3,4- ethylenedioxythiophene) polystyrene sulfonate). Alternatively, the sensing element(s) can be made of a material(s) selected of a group comprising or consisting of: conductive ink, Graphene, and nanosilver wire ink. These materials may be non-transparent or transparent materials.

The wiring 400, in particular the first wire 401 thereof, is preferably flexible and stretchable in the meaning discussed above for these terms. Preferably, also the first sensing element 301 is flexible and stretchable in the meaning discussed above for these terms. The wiring 400 may be arranged as a part of an electrically conduc tive multilayer structure.

The wiring 400, in particular the first wire 401 thereof, may comprise or it may be made of transparent and/or translucent material. Particularly, the wiring may com prise or consist of a transparent and/or translucent, stretchable, conductive material. The wiring may comprise or consist of PEDOT:PSS (i.e. poly(3,4-ethylenedioxythi- ophene) polystyrene sulfonate).

The sensor 100 can be used in such environments, wherein their shape is subject to change. In addition, or alternatively, the sensor can be used on complex surface, such as on a double curved surface. The sensor 100 can comprise indicating area(s) as shown e.g. in Figs. 10a-11 b.

The wiring 400, i.e., the wire(s) 401 , 401 , 403 can be manufactured e.g. by using such additive manufacturing techniques that produce stretchable conductive wir ings, such as printing. In the alternative, the wiring 400 can be laminated onto a layer of material. The wiring 400 can be manufactured (e.g. printed or laminated) onto a flexible and stretchable layer 200. In the alternative, the wiring 400 may be manufactured (e.g. printed or laminated) onto another layer, such as an elastic layer 130A, 130B, 150.

To obtain reliable electric sensor, particularly force sensor, the sensor may comprise elastic layer(s) 130A, 130B, 150, and/or the flexible and stretchable layer(s) 200, which may be electrically insulating layer(s). At least in the case of a capacitive op erational principle, the flexible and stretchable layer 200 is preferably electrically insulating.

In an embodiment, the electronic arrangement comprises a circuit board 700, such as a flexible circuit board. The circuit board 700 of the electronic arrangement 120 can be connected to the first electrically conductive wire 401 using suitable joining technique, such as crimp connection or conductive adhesive, such as anisotropic conductive adhesive (ACF). Conductive adhesives may be used to form mechani cally reliable electrically conductive joints.

The sensor 100 may comprise a flexible and stretchable protective layer. The pro tective layer may protect at least a part of the wiring 400. Moreover, in other parts, the protective layer may be attached to another layer. In an embodiment, the wiring 400 can be arranged in between the substrate layer 200, 150, 130A, 130B, and flexible and stretchable protective layer.

The sensor 100 may comprise a second electrically conductive wire 402. Preferably the second sensing element 302 is also flexible and stretchable in the meaning dis cussed for these terms.

The first stretchable sensing element 301 and/or the second stretchable sensing element 302 can be attached to the flexible and stretchable layer 200, if used. Al ternatively, the first stretchable sensing element 301 and/or the second stretchable sensing element 302 can be attached to the elastic layer 130A, 130B, 150, if used. The individual stretchable sensing elements are referred to by the references 301 , 302, 303, ... ; while the stretchable sensing elements in general are referred to by the reference 300. The stretchable electrode(s) 300 is/are electrically conductive electrode(s).

Throughout this description, the term “electrically conductive”, referring to the elec trically conductive structure, layer, electrode, sensing element, wiring and material, refers to a resistivity (i.e. specific electrical resistance) of less than 10 Qm, more preferably less than 5 Qm at the temperature of 20°C. Preferably, an electrically conductive material as well as an electrically conductive layer has a resistivity of at most 1 Qm, measured at a temperature of 20°C and at an internal elastic strain of 0 %; i.e. without compression or tension, i.e. at rest.

The sensor 100 may comprise a second sensing element 302. If the sensor 100 comprises the second sensing element 302, the second sensing element can be arranged a distance apart from the first sensing element 301 . As an example, the second sensing element 302 may be arranged at least 0.5 mm apart from the first sensing element 301. The sensor can comprise, for example, from 1 to 100 sensing elements, such as electrodes, or from 10 to 50 sensing elements, e.g. electrodes. The preferable number of sensing elements depend, for example, on a structure of the sensor, and an installation surface of the sensor, and an illumination arrange ment of the sensor.

Thus, in order to electrically insulate the stretchable sensing elements 300 from each other, the first stretchable sensing element 301 can be arranged a distance di apart from the second stretchable sensing element 302. As is conventional, a dis tance di between first and second electrodes and a distance d-ij_j between elec trodes i and j refer to the distance between closest points of the two electrodes, i.e. the smallest distance in between the two electrodes. Each stretchable electrode i (301 , 302, 303, ... , 315, 316) can be located a distance d-ij_j apart from each other stretchable electrode j (316, 301 , 302, 303, ... , 315).

In a preferred embodiment, each two closest electrodes are reasonably close to each other. More specifically, in an embodiment, the maximum distance di_,j,jm® be tween each closest electrode is at most 15 mm, preferably at most 10 mm, and most preferably equal or less than 5 mm. The maximum can be found by considering each electrode i subsequently. This ensures that most of a surface having the elec trodes is covered by electrodes, which may improve the accuracy of measurements.

In an advantageous embodiment, the minimum of the distances d-ij_j between two closest electrodes is at least 1 mm, preferably at least 2 mm. Such a minimum dis tance improves the separation of the stretchable electrodes. As a result, disturb ances during measurements can be diminished. In an embodiment, the improved separation can result in less capacitive coupling between the electrodes.

The sensor 100 can comprise equal to or more than fifteen stretchable sensing ele ments, such as electrodes 300 attached to a layer 150, 130A, 130B, 200 of the sensor, preferably to the flexible and stretchable layer 200. This may improve the accuracy of measurements.

As for the stretchability of the stretchable sensing elements 300, the stretchable sensing elements 300 may have a second yield strain s_y,3oo that is, in an embodi ment, at least 10 per cent. This value has been found to be sufficiently high for a sensor in many applications. This value has been found to be sufficiently high from the point of view of mechanical reliability of the stretchable sensing elements 300, since typical deformations are less than this value. In the alternative, the second yield strain s_y,3oo may be at least 20 per cent or at least 30 per cent. Therefore, the sensing element 300 can be used with a sensor that will be installed on a difficult kind of installation surface. In the alternative, the second yield strain s_y,3oo may be at least 30 per cent Therefore, the sensing element 300 can be used with a sensor that will be installed on a very difficult kind of installation surface.

The flexible and stretchable layer 200, if used, may have a reasonably large first yield strain s_y,2oo. In an embodiment, the first yield strain s_y,2oo is at least 10 per cent. This value has been found to be sufficiently high for the sensor in many applications. This value has been found to be sufficiently high also from the point of view of me chanical reliability of the flexible and stretchable layer 200, since typical defor mations are less than this value. In the alternative, the first yield strain s_y,2oo may be at least 20 per cent. Therefore, the flexible and stretchable layer can be used with a sensor that will be installed on a difficult kind of installation surface. In the alterna tive, the first yield strain s_y,2oo may be at least 30 per cent. Therefore, the flexible and stretchable layer can be used with a sensor that will be installed on a very diffi cult kind of installation surface. Typically, the second yield strain s_y,3oo of the stretch able sensing elements 300 is less than the first yield strain s_y,2oo of the flexible and stretchable layer 200.

In addition, the flexible and stretchable layer 200, if used, is preferably electrically insulating. Throughout this description, the term “electrically insulating”, referring to a material, surface, structure, or layer, refers to a resistivity (i.e. specific electrical resistance) of more than 100 Qm at the temperature of 20°C.

The flexible and stretchable layer 200 may be a part of an illumination arrangement of the sensor indicating certain area(s), such line(s) and/or letter(s) and/or other symbol(s) on the sensor. The flexible and stretchable layer may form at least part of a light guide of the sensor. The flexible and stretchable layer 200 may comprise transparent and/or translucent area(s). Still further, the flexible and stretchable layer 200 may be a transparent and/or translucent layer. In an advantageous embodi ment, the flexible and stretchable layer 200 comprises prisms. In an embodiment, the flexible and stretchable layer has perforated areas.

The stretchable sensing element 300 can be configured to detect changes in an area substantially the same as the area of the sensing element. Thus, the effective area from which such a stretchable sensing element is configured to measure, can be equal or substantially equal to the area of the stretchable sensing element 301 itself. Herein the area refers to the area of the cross section of the stretchable sens ing element onto a plane having a surface normal that is parallel to the direction of thickness of the sensor 100.

At least one stretchable sensing element 300, preferably all stretchable sensing el ements 300 of the sensor 100, can be made from conductive ink, hence, the stretch able sensing element(s) can be reasonably homogeneous. Alternatively, at least one stretchable sensing element can be made of conductive, stretchable, transpar ent and/or translucent material. Thus, the at least one stretchable sensing element may form a part of the illumination arrangement of the sensor.

In an embodiment, at least one stretchable sensing element 300, preferably all stretchable sensing elements 300, is/are made from electrically conductive fabric or fibres. Conductive ink, as well as conductive fabric, typically comprises electrically conductive particles, such as flakes or nanoparticles, attached to each other. Thus, in an embodiment, at least the first stretchable sensing element 301 , preferably all sensing elements 300, comprise(s) electrically conductive particles, such as flakes or nanoparticles, attached to each other in an electrically conductive manner. In a preferable embodiment, the electrically conductive particles comprise at least one of carbon (including, but not limited to graphene and carbon nanotubes), copper, silver, and gold. In an embodiment, the first sensing element 301 comprises electri cally conductive polymer-based material, preferably at least one of polyaniline, a polyvinyl (e.g. polyvinyl alcohol or polyvinyl chloride), and PEDOT:PSS (i.e. poly(3,4-ethylenedioxythiophene) polystyrene sulfonate).

At least one stretchable sensing element 300, preferably all stretchable sensing el ements 300, of the sensor may be made from stretchable conductive ink. The stretchable conductive ink may be selected from a group comprising or consisting of:

- copper,

- silver,

- carbon

- graphene,

- nano silver (copper) wire,

- carbon nanotube ink CNT, and - gold.

The stretchable sensing element(s) 300 may be e.g. sewed to on otherwise non- conductive layer, such as a flexible and stretchable layer 200. Thus, the stretchable sensing element 300 may be made as a mesh of conductive yarns, such as metal- coated polyamide or polyester. It is noted that also such a stretchable sensing ele ment is configured to detect the changes, such as capacitance, in an area that is substantially the same as the area limited by the outer edge of the stretchable sens ing element. Thus, the effective area from which such a stretchable sensing element can be configured to measure, may be equal to the area limited by the outer edge of the stretchable sensing element 301 ; even if the area of the conductive yarns may be less. As an alternative to sewing, a sensing element having the shape of a mesh can be printed with conductive ink. As evident, in both types of sensing elements, the effective area of the stretchable sensing element is typically equal to the area limited by the outer edge of the stretchable sensing element 301.

What has been said about the material of the first sensing element 301 applies, in an embodiment, to all sensing elements including the second sensing element 302. What has been said about the material of the first sensing element 301 applies, in an embodiment, to the first wire 401. What has been said about the material of the first sensing element 301 applies, in an embodiment, to the second wire 402, and preferably to all wires 400.

The first sensing element 301 is preferably able to stretch at least 5 % without break- ing. In addition, the first wire 401 is preferably able to stretch at least 5 % without breaking. Thus, the sensor having said sensing element and wire can be installable on a curved surface, i.e. , the first sensing element and the first wire are not breaking on the curved surface. In addition, the second sensing element 302 and the second wire 402, as well as all other sensing elements and wires, are preferably able to stretch at least 5 % without breaking. Thus, the sensor can be installable on a dou ble curved surface, i.e., said sensing elements and wires are not breaking on the double curved surface.

If the sensor is to be installed on a difficult surface, the light mask is preferably at- tached on to a surface of the sensor. Otherwise installation procedure of the sensor might become very challenging. Furthermore, the sensor preferably has a light guide in the sensor for guiding light from a light source to the light mask. Wires 400 can be connected to the sensing elements 300 by using conductive ad hesive^). Thus, the wires can be connected to the sensing elements in a reliable way. As an alternative to the conductive adhesive, wires 400 may be arranged (e.g. printed) directly on the same substrate as the sensing elements. By printing the wires, the sensor arrangement may be efficiently manufactured.

As discussed above, in an embodiment, at least a part of the wiring 400 can be arranged in between the flexible and stretchable layer 200 and the elastic and de formable layer 130A, 130B, 150. Furthermore, some adhesive may also be arranged in between the flexible and stretchable layer 200 and the elastic and deformable layer 130A, 130B, 150 in order to join the layers together.

In an embodiment, wiring for the sensing elements is arranged on a flexible foil. In an embodiment, the sensor 100 comprises a flexible foil having a fourth Young’s modulus; and electrically conductive wiring 400 attached to the flexible foil. The first Young’s modulus of the flexible and stretchable layer 200 can be less than the fourth Young’s modulus. In this way, the flexible foil resists deformations more than the flexible and stretchable layer 200. However, the flexible foil is not necessary (nor always advantageous) for the sensor.

The wiring 400 comprises at least one wire 401 , more preferably at least 5 wires and most preferably equal to or more than ten wires 401 , 402, 403. The wires 401 , 402, 403 are preferably electrically insulated from each other. Moreover, the wiring is preferably coupled in an electrically conductive manner to the stretchable sensing element(s) 300. The wiring 400 may comprise transparent and/or translucent areas, which may be part of the light guide.

Therefore, at least a part of the electrically conductive wiring 400 can be coupled to the first stretchable sensing element 301 in an electrically conductive manner; and at least a part of the electrically conductive wiring 400 can be coupled to the second stretchable sensing element 302 in an electrically conductive manner.

One wire 401 , 402, 403 may be coupled in an electrically conductive manner to only one stretchable sensing element 301 ,302. This is to improve the spatial resolution of the sensor, i.e. each stretchable sensing element can be used to measure, for example a force or pressure, at the location of substantially only the stretchable sensing element. The first wire 401 may connect the first sensing element 301 to the electronic ar rangement 120. The first sensing element 301 is preferably arranged onto the flexi ble and stretchable layer 200. Alternatively, it can be arranged, for example, onto the elastic deformable layer 130A, 130B, 150. The flexible and stretchable layer 200 and/or the elastic deformable layer may form at least a part of the light guide. Thus, it/they may comprise e.g. transparent and/or translucent area(s), and/or prisms.

The sensor 100 may comprise insulating layer(s) and electrically permeable and/or conductive layer(s) 140, 142. The electrically permeable and/or conductive layer(s) 140, 142 may form at least part of the light guide. Thus, it/they may comprise e.g. transparent and/or translucent area(s), and/or prisms. The different layers may be attached to each other with adhesive as known per se. However, for clarity, adhe sive is not shown in the figures. The adhesive may be, or comprise, transparent and/or translucent adhesive.

The illumination solution of the sensor may comprise lines and/or symbols formed by the light guide and light mask of the sensor together with a light source 19.

As discussed, the sensor 100 may comprise at least one insulating layer. The elas tic, deformable layer 130A, 130B, as well as the flexible and stretchable layer 200 can be the insulating layer(s). Further, as discussed, the elastic, deformable layer 130A, 130B, as well as the flexible and stretchable layer 200 may form at least part of the light guide. The sensor 100 may comprise a first layer 130A, 150 and a second layer 130B, 200, the first layer and the second layer being insulating layers which are arranged such that the sensing element layer 300 is arranged in between the first and second insulating layers in the direction of thickness of the thickness of the sensor structure 100. Furthermore, the sensor may comprise a third insulation layer. Electrical contacts to the sensing elements in use might cause malfunction of the sensor arrangement. Thus, a purpose of the insulating layer can be to electrically insulate the sensing element(s) 301 , 302 from environment. In an embodiment, a purpose of the of the insulating layer is to electrically insulate the sensing element(s) 301 , 302, in order to form a capacitance in between the first sensing element 301 and the top of the elastic and deformable layer, such as a conductive layer on the elastic and deformable layer.

As for suitable materials for the insulating layers, a purpose of the insulating layers is to electrically insulate. Therefore, a resistivity of a material of the insulating layer(s), for example the flexible and stretchable layer 200, and a material of other insulating layer(s) (if present) may be at least 10 Qm, more preferably at least 50 Qm at a temperature of 20°C. Preferably, a resistivity of the flexible and stretchable layer 200 and/or other insulating layer(s) is at least 100 Qm at a temperature of 20°C.

Referring to Figs 1a to c, the sensor 100 may comprise an elastic and stretchable layer 150. The elastic and stretchable layer 150 can comprise an elastic, deformable layer 130A and/or a flexible and stretchable layer 200. The flexible and stretchable layer 200 can also be elastic at least to some extent. The elastic and deformable layer 130A is typically compressible.

The sensor may comprise a first electrically permeable and/or conductive layer 140. The electrically permeable and/or conductive layer 140, 142, related in particular to the permeability of the layer, can pass an electric field through the electrically per meable layer. Further, the electrically permeable and/or conductive layer 140, re lated in particular to the conductivity of the layer, can form a capacitance in between the sensing element and the electrically permeable and/or conductive layer itself. The first electrically permeable and/or conductive layer 140 may serve as a ground sensing element. In an embodiment, the electrically permeable and/or conductive layer 140, 142 is used to increase the capacitance of the first sensing element when compared to situation without said layer.

As discussed above, the sensor arrangement may further comprise an electronic arrangement 120. The electronic arrangement 120 can be electrically coupled to the first sensing element 301 in order to measure a value of interest of the first sensing element 301. The electronic arrangement 120 can be coupled to the first sensing element 301 via the first wire 401 . The first wire 401 may be seen as part of the electronic arrangement 120 and/or as part of the sensor 100.

In an embodiment, the electronic arrangement 120 is electrically coupled to the elec trically permeable and/or conductive layer 140,142 in order to measure e.g. capac itance of the first sensing element 301 relative to the electrically permeable and/or conductive layer 140, 142. A common potential, e.g. a ground potential, may be conducted to the electrically permeable and/or conductive layer at least when meas uring the capacitance of the first sensing element 301 relative to the conductive layer 140, 142. Flowever, the electronic arrangement 120 need not be electrically coupled to the electrically permeable and conductive layer 140,142. Furthermore, the sensor 100 does not need to have said electrically permeable and conductive layer 140, 142.

The sensor 100 may comprise at least one stretchable sensing element 300 at tached to the flexible and stretchable layer 200 or to the elastic, deformable layer 130A, 130B. Preferably, at least most of the sensor 100 is stretchable and elastic.

The flexible and stretchable layer 200 may be arranged in between a stretchable sensing element 300, 301 , 302 and the elastic layer 130A, 130B, 150. In some ap plications, the sensor is more comfortable to use, provided that the elastic deform able layer 130A,130B is directly in contact with the flexible and stretchable layer 200, i.e. the stretchable sensing elements 300 are not arranged in between the elas tic deformable layer 130A and the flexible and stretchable layer 200.

In an embodiment, the flexible and stretchable layer 200, the first and second stretchable sensing elements 301 , 302, and the electrically conductive wiring 400 can be left on a same side of the elastic, deformable layer 130A. This helps the manufacturability of the sensor 100.

In an embodiment, the flexible and stretchable layer 200 is arranged in between two sensing element layers (shown in Fig 1d). In this embodiment, the flexible and stretchable layer preferably forms at least a part of the light guide.

The Young’s modulus of the elastic, deformable layer 130A, 130B, if used, should be reasonably small. Flowever, many materials that are soft and/or have a small Young’s modulus are known to creep. Creep, on the other hand is not preferred, since the permanent compression of the elastic deformable layer 130A, 130B would affect the measurement results.

To ensure reasonable deformations in use, for example for a double curved surface, the elastic deformable layer 130A, 130B has a third Young’s modulus Y130A. For example, the material of the layer 130A, 130B may be selected such that the layer 130A, 130B is compressed, in typical use, about 1 to 15 %; and up to 30 %. Natu rally, the compression depends on the pressure, which need not be spatially or tem porally uniform. Typical pressures may be of the order of 2 kPa to 1000 kPa. Thus, the third Young’s modulus Y130_A may be e.g. at most 15 MPa, preferably equal to or less than 5 MPa. In addition, third Young’s modulus Yi30_A may be e.g. at least 0.01 MPa, preferably equal to or more than 0.2 MPa. A large strain (resulting from a small Young’s modulus) could make the material of the elastic deformable layer 130A to creep in use. This could deteriorate measurements in the long term. Moreover, a small strain (resulting from a large Young’s modulus) is hard to measure.

Thus, a Young’s modulus of the elastic, deformable layer(s) 130A, 130B, if used, is/are preferably from 0.01 MPa to 15 MPa, preferably from 0.1 MPa to 5 MPa. A Young’s modulus in tension may differ from the Young’s modulus in compression.

A material of the compressible layer, if used, has preferably a yield strain of at least 5 per cent, more preferably at least 10 per cent. This ensures that the material can be sufficiently compressed in use.

The first elastic, deformable layer 130A and/or the second elastic, deformable layer may be made by using foaming agents, e.g. thermoplastic micropheres or gases. Thanks to the foaming agents, mechanical properties of said layer(s), such as com pression set, can be improved. Further, these may have an effect on translucency of the sensor.

In an embodiment, the sensor comprises the first elastic, deformable layer 130A and/or the second elastic, deformable layer, which is/are preferably closed cell foaming thermoplastic elastomers, preferably based on polyurethane and/or silicone and/or polyester and/or polyethylene resin. Thus, mechanical properties of said layer(s), such as compression set, can be improved. Further, these may have an effect on translucency of the sensor. The first elastic, deformable layer 130A and/or the second elastic, deformable layer 130B may comprise at least one of polyure thane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodime- thylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienesty- rene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, sty- rene-ethylene-butylene-styrene and thermoplastic elastomeric gel. Said polyure thane is preferably thermoplastic polyurethane. In an embodiment, the total amount of said material(s) is at least 50 wt.%, more preferably at least 70 wt.-% of the first deformable layer.

Preferably, a thickness ti30_A of the elastic, deformable layer 130A, 130B, if used, is equal to or more than 0.1 mm, more preferably equal to or more than 0.2 mm and most preferably equal to or more than 0.3 mm. Further, a thickness ti30_A of the elas tic, deformable layer 130A, 130B may be equal to or less than 1.5 mm, more pref erably equal to or less than 1.0 mm, and most preferably equal to or less than 0.8 mm. Thanks to said thickness of the elastic, deformable layer 130A, 130B a force detection sensitivity may be improved. Further, an internal structure of the sensor may be improved so that e.g. 3D stretchability of the sensor may be improved.

The first elastic, deformable layer 130A , if used, may form at least part of the light guide of the sensor. The first elastic, deformable layer 130A may be a transparent and/or translucent layer. Alternatively, the first elastic, deformable layer 130A can be partially transparent and/or translucent, i.e. , the layer can have at least one trans parent and/or translucent area. Alternatively or in addition, the first elastic, deform able layer 130A may comprise prisms. In an embodiment, the first elastic, deforma ble layer 130A has perforated areas. Flowever, perforations may, in some cases, affect a reliability of measurements.

Further, the flexible and stretchable layer 200, if used, may form at least part of the light guide of the sensor. The flexible and stretchable layer may be a transparent and/or translucent layer. Alternatively, the flexible and stretchable layer 200 may be partially transparent and/or translucent, i.e., the layer can have at least one trans parent and/or translucent area. Alternatively or in addition, the flexible and stretch able layer 200 may comprise prisms. In an embodiment, the flexible and stretchable layer 200 has perforated areas. Flowever, perforations may, in some cases, affect a reliability of measurements.

Still further, the second elastic, deformable layer 130B, if used, may form at least part of the light guide of the sensor. The second elastic, deformable layer 130B may be a transparent and/or translucent layer. Alternatively, the second elastic, deform able layer 130B may be partially transparent and/or translucent, i.e. the layer can have at least one transparent and/or translucent area. Alternatively or in addition, the second elastic, deformable layer 130B may comprise prisms. In an embodiment, the second elastic, deformable layer 130B has perforated areas. Flowever, perfora tions may, in some cases, affect a reliability of measurements.

Therefore, the sensor may comprise the first elastic, deformable layer 130A, which may form at least part of the light guide. Alternatively or in addition, the sensor may comprise the flexible and stretchable layer 200, which may form at least part of the light guide.

Still further, the sensor may comprise the electrically permeable and/or conductive layer(s) 140, 142, which may form at least part of the light guide.

Further, the sensor may comprise a light mask. The light mask, or at least part of the light mask, is preferably formed on a surface of the sensor in order to a form clear symbol on the surface of the sensor. Alternatively, or in addition, at least part of the light mask may be formed on a surface of a product comprising the sensor in order to a form clear symbol on the surface of the product. The light mask is prefer ably a stretchable light mask.

Therefore, thanks to the light mask, an easiness of a manufacturing process of a sensor comprising the illumination solution providing information for a user, such as indicating a certain point on a surface of the sensor, may be improved. Further, an easiness of an installation process of the sensor may be improved.

The higher is the transparency value of the transparent and/or translucent area, the easier the light can go through said area. Therefore, if the transparent and/or trans lucent areas are used, a light source of the sensor may have lowered energy con sumption. Alternatively, or in addition, prisms can be used to form light guide having lowered energy consumption.

The cork or other non-transparent and/or translucent material may not be preferred material for transparent and/or translucent layer(s). Flowever, if non-transparent ma terials), such as the cork, is used in the transparent and/or translucent layer/area/point, a micro perforation or thinning of the material may be needed for the predetermined transparency. Flowever, perforations may, in some cases, affect a reliability of measurements. Further, usage of non-transparent materials may in crease energy consumption of the sensor comprising the illumination solution.

In an embodiment, if the elastic, deformable layer(s) 130A, 130B and/or the flexible and stretchable layer 200 and/or the electrically permeable and/or conductive layer(s) 140, 142 comprise both,

- transparent and/or translucent area(s), and

- non-transparent area(s), the non-transparent material may be used at least for said non-transparent area(s). For the transparent and/or translucent area(s), the non-transparent material might be used e.g. with perforation or thinning of the material. However, preferably, trans parent and/or translucent material is used for transparent and/or translucent areas.

In an advantageous embodiment, transparent and/or translucent areas are not merely passing light through said area(s) but said areas may work as a light guide by distributing light from a light source to a particular area of the sensor that requires illumination e.g. for indicating a certain point on a surface of the sensor.

If the deformable layer(s) 130A, 130B comprise(s) one or more transparent and/or translucent areas, transparency the said areas can be from 10% to 98%, preferably in a range between 40% and 98%, more preferably in a range between 55% and 98%, and most preferably in a range between 70% and 98%.

Further, If the flexible and stretchable layer 200 comprises one or more transparent and/or translucent areas, transparency of said areas can be from 10% to 98%, pref erably in a range between 40% and 98%, more preferably in a range between 55% and 98%, and most preferably in a range between 70% and 98%.

If the electrically permeable and/or conductive layer(s) 140, 142 comprise(s) one or more transparent and/or translucent areas, transparency of said areas can be from 10% to 98%, preferably in a range between 40% and 98%, more preferably in a range between 55% and 98%, and most preferably in a range between 70% and 98%.

By forming the sensor so that the sensor has transparent and/or translucent area(s), it is possible to provide an improved illumination solution providing an information for a user of the sensor.

As discussed, light may efficiently go through said transparent and/or translucent areas, and/or areas having prisms. Thus, the sensor may not need to have holes or a photoconductor for illuminating a surface of the layer. Further, the transparent and/or translucent area(s) as well as areas comprising prisms may not merely pass the light through the area(s) but said area(s) may work as a light guide by distributing light from the light source to a particular area that requires illumination for indicating a certain point on a surface of the sensor. In this application, the illumination arrangement is preferably a stretchable illumina tion arrangement.

In an advantageous embodiment, the stretchable illumination arrangement com prises at least one of, and preferably all of:

- a light source,

- a light guide in the sensor, and

- a light mask.

The sensor may be a force sensor. Figs 10a-c discloses an example of a deformable force sensor comprising the illumination arrangement for indicating a certain point on a surface.

As illustrated in Figs 11 a-b, it is possible to provide several areas showing infor mation to a user by using the novel solution. In this example, the symbol F as well as the surrounding lines are pointed out from the surface of the sensor 100 by using the illumination arrangement.

A challenge with surrounding transparent and/or translucent lines (shown in Figs 11 a-b) may be to hide the wiring 400 so that the wires cannot be seen by the user. Therefore, the sensor may comprise one or more transparent and/or translucent conductive polymers, such as PEDOT PSS (i.e. poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), which transparent and/or translucent conductive polymer(s) may form at least part of the wiring 400. Thanks to the transparent and/or translucent conductive polymer, the wiring 400 can be hided from a user, even in case of several transparent and/or translucent lines as shown in Figs 11a-b. Thus, the sensor may be easy to use when the certain area is indicated without any noncontinuous areas within the line(s) and/or symbol(s) on the surface of the sensor.

The sensor 100 may be a pressure sensor. The sensor 100 may be, e.g., a touch sensor.

In the sensor, a capacitance of a sensing element may change by movement of the touching object (e.g. a finger of a user). For providing information to a user, for example for indicating a certain point on a surface, a light guide may be used together with a light mask (shown in Figs 10a-c and 11a-b).

Thus, in an embodiment, a stretchable ink may cover a suitable area of the trans parent and/or translucent material to obtain a predetermined symbol on the surface of the sensor. In a preferable embodiment, the stretchable ink is selected from a group consisting of

- copper,

- silver,

- carbon

- graphene,

- nano silver (copper) wire,

- carbon nanotube ink CNT, and

- gold, more preferably from the following group:

- copper,

- silver, and

- gold.

The stretchable ink, if used, is preferably printable. The stretchable ink may form, e.g. at least part of the top layer 201 of the sensor.

In this specification, the term “non-transparent material” refers to a material having a transparency of less than 1 lux. The non-transparent material may comprise at least one material selected from the following group:

- cork,

- leather,

- synthetic leather (artificial leather),

- sustainable leather,

- alcantara,

- stretchable ink,

- non-transparent plastic,

- non-transparent thermoplastic materials, such as polycarbonate, or polyme thyl methacrylate,

- non-woven fabric,

- woven fabric, - biocomposites comprising bioplastic and cellulose-based fibers, and

- wood.

The above-listed materials may be used e.g. to form predetermined symbols on the first surface of the sensor.

The sensor may comprise the top layer 201 , which top layer 201 may form at least part of the light guide. Fig.4 illustrates an embodiment comprising the top layer 201.

The top layer 201 of the sensor may form the light guide, or at least part of the light guide. The top layer may be one of the mentioned layers (the elastic, deformable layer, the electrically permeable and/or conductive layer, or the flexible and stretch able layer) so that said layer is forming the first surface of the sensor, or the top layer may be a separate layer e.g. on any of the above mentioned layers.

As discussed, in an advantageous embodiment, the sensor 100 comprises the flex ible and stretchable layer 200. The layer 200 is stretchable in order for it to adapt, in use, to a needed shape. For example, the flexible and stretchable layer 200, in use, may stretch to conform with the dynamic shape of an installation surface. For reasonably easy stretching, the flexible and stretchable layer 200 (i.e. the material of the stretchable layer) has preferably a relatively small first Young’s modulus Y200. Preferably, the flexible and stretchable layer 200 is flexible in the aforementioned sense. Moreover, preferably, a Young’s modulus of the flexible and stretchable layer 200 is at least 0.01 MPa and equal to or less than 10 GPa, preferably equal to or less than 5.0 GPa. Thus, the sensor can be used in many different kinds of applica tions.

In an embodiment, the sensor further comprises the elastic deformable layer 130A, 130B, and in order to have deformations within the sensor 100 concentrated mainly in the elastic deformable layer 130A, 130B, the third Young’s modulus Y130A of the first elastic, deformable layer 130A, 130B can be smaller than a first Young’s mod ulus Y200 of the flexible and stretchable layer 200. This improves the measurement accuracy, as the locations of the compressions are better controlled.

The flexible and stretchable layer 200, if used, may be made of suitable polymer film. The flexible and stretchable layer 200 may be made of suitable fabric. The flexible and stretchable layer 200 may comprise polyimide, polyethylene naph- thalate, polyethylene terephthalate, polyetheretherketone, thermoplastic polyurethane), polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, poly- borodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadi- enestyrene, styrene-ethylene-butylene-styrene ethylene propylene rubber, neo prene, cork, latex, natural rubber, siloxane polymer (such as silicone), and/or ther moplastic elastomeric gel. Preferably, the total amount of said material(s) is at least 50 wt.%, more preferably at least 70 wt.-% of stretchable layer. Therefore, the flex ible and stretchable layer 200 may act as a flexible insulator. The flexible and stretchable layer 200 may comprise one or more transparent and/or translucent ar eas. Advantageously, the flexible and stretchable layer 200 comprises at least one prism.

In an embodiment, the flexible and stretchable layer 200 comprises a polymer film, such as a film of thermoplastic polyurethane (TPU) or thermosetting resin, e.g. cured epoxy resin. The total amount of said material(s) may be e.g. at least 50 wt.% of stretchable layer. Thus, the flexible and stretchable layer 200 may act as a flexible insulator and it may be easy to manufacture.

The thermoplastic polyurethane (TPU), if used, may comprise polyester-based TPU and/or polyether-based TPU. In an embodiment, the flexible and stretchable layer 200 comprises fabric, e.g. polyamide (such as nylon) or polyester. The flexible and stretchable layer 200 may comprise said fabric and said film. Preferably, the total amount of the material(s) is at least 50 wt.%, more preferably at least 70 wt.-% of the flexible and stretchable layer 200.

In an embodiment, the flexible and stretchable layer 200 comprises the thermo plastic polyurethane TPU and the stretchable sensing elements 300 are made from conductive ink. In an embodiment, the flexible and stretchable layer 200 comprises non-conductive fabric in between the stretchable sensing elements 300, and the stretchable sensing elements 300, or at least some thereof, may have been made using conductive fabric, such as polyamide or polyester that is coated by a metal, such as silver. In the alternative or in addition, conductive ink may be used in com bination with fabrics to form the stretchable sensing elements 300 or at least some thereof.

The elastic and stretchable layer 150, if used, can serve for the purposes of both the flexible and stretchable layer 200 and the first elastic, deformable layer 130A (see Figs 1a-1c). The elastic and stretchable layer 150 may comprise one or more transparent and/or translucent areas. The elastic and stretchable layer may be a transparent and/or translucent layer. The elastic and stretchable layer may comprise prisms. The properties of the elastic deformable layer 130A, in particular the Young’s modulus thereof, may apply also the elastic and stretchable layer 150. Thus, the Young’s modulus Y150 of the elastic and stretchable layer 150 may be within the limits discussed in this application for the elastic, deformable layer 130A. Still further, what will be said about the thickness ti30_A or the direction of the thick ness ti30_A of the elastic, deformable layer 130A may apply to the thickness tiso of the elastic stretchable layer 150 and the direction of the thickness tiso.

The elastic deformable layer 130A, 130B, 150, if used, can have a perforating and/or holes that extend in the direction of the thickness ti3o of the elastic deformable layer 130A, 130B, 150 (not shown in Figures). Such holes in effect make the material softer. Thus, by having the holes, it is possible to use a harder material and/or a material with a higher Young’s modulus. Such a material typically creeps signifi cantly less than softer materials. The effect of the holes is to reduce the area of that part of the elastic deformable layer 130A, 130B that comprises the deformable solid material. Further, light may go through the holes. Thus, such holes may have an effect on transparency and, particularly, on translucency of the sensor.

If the elastic, deformable layer 130A, 130B has the holes, the total cross-sectional area of the holes constitutes preferably at least 5 %, more preferably at least 10 % of the cross-sectional area of the elastic deformable layer 130A, 130B. Such a ma terial typically creeps significantly less than softer materials. Flerein the cross sec tion refers to a cross section on a plane that has a surface normal that is parallel to the direction of thickness. Moreover, the total cross-sectional area of the holes refers to the sum of the cross-sectional areas of the individual holes. Still further, the cross- sectional area of the elastic deformable layer 130A, 130B refers to the area of a section limited by the outer boundary of the elastic deformable layer 130A.

In an embodiment, at least some of the holes extend from a first side of the elastic, deformable layer 130A, 130B, through the elastic, deformable layer 130A, 130B, to a second side of the elastic deformable layer 130A, 130B. In addition to softening, such through-holes may improve ventilation of the sensor 100. In case the sensor 100 comprises the additional elastic deformable layer 130B, in an embodiment, at least some holes extend from a first side of the second elastic deformable layer 130B, through the second elastic deformable layer 130B, to a second side of the second elastic deformable layer 130B. In an embodiment, the holes extend in the direction of the thickness of the elastic and stretchable layer 150. The holes may extend from one side of the elastic and stretchable layer 150 to the opposite side of the elastic and stretchable layer 150 in the direction of the thickness of the elastic and stretchable layer 150. Such holes may be used to control translucency of the sensor.

The holes can be used engineer the local effective hardness of the elastic deform able layer 130A, 130B. By using holes, a region can be made softer than another region, even if the same material is used in both regions. Correspondingly, in areas, where the load (e.g. force or pressure) is known to be small, a lot of holes can be made to soften the material a lot. A lot of holes refer to the total cross-sectional area of the holes in proportion to the corresponding region of the deformable layer 130A. By increasing the size and/or number of the holes, the material can be made softer. The engineering of the softness may be more effective when the number of holes is significant. For example, the number of holes may be at least ten or at least fifty. However, it should be noted that holes may have an effect on measurements as well as on illumination arrangement.

The sensor 100 may comprise multiple sensing elements (see Figs 2a). Preferably, the sensing elements are arranged in such a way that a value of interest is measur able using all sensing elements simultaneously. In particular, in an embodiment, the sensing elements cover most of the cross-sectional area of the sensor, such as at least 50% or at least 80% of the cross-sectional area. In an advantageous embodi ment, a capacitance is measurable by the sensor 100 by using all or substantially all sensing elements simultaneously over the whole cross-sectional area covered by the sensing elements.

The first sensing element 301 may form at least a part of the wiring 400. In this case, at least a part of the first sensing element 301 is preferably arranged on the same side of a substrate, such as the flexible and stretchable layer 200, as the wiring 400. In such a case, preferably the (whole) first sensing element 301 is arranged on the same side of the substrate as the wiring 400. In case the elastic, deformable layer 130A is used and the first sensing element forms a part of the wiring 400, preferably at least a part of the first sensing element 301 is arranged in between the flexible and stretchable layer 200 and the elastic, deformable layer 130A. In such a case, preferably the (whole) first sensing element 301 is arranged in between the flexible and stretchable layer 200 and the elastic, deformable layer 130A.

In an embodiment, the sensing element(s) 300 define measurement areas. Within a measurement area, at least one sensing element 300 is arranged. The measure ment area defined by the sensing element is the area, from which values, e.g. ca pacitance, are configured to be measured by the sensing element. Sensing ele ments of two different measurement areas are not preferably in a galvanic contact with each other.

In a preferable embodiment, the measurement area comprising the first primary sensing element 301 does not partially overlap with the measurement area compris ing the first secondary sensing element 321 in the direction Sz of the thickness of sensor 100. There may be some overlap between the sensing elements, but prefer ably, the amount of overlap with the measurement areas is small.

In the alternative, large one of the overlapping measurement areas may comprise the whole of the smaller measurement area. In an embodiment, the sensor is a ca pacitive sensor. Then, when the capacitances are measured, preferably relative to at least one electrically permeable and/or conductive layer 140, 142, the capaci tance of the non-overlapping part can be computed from the measurements. The capacitances of the smaller sensing element and larger electrode may be measured e.g. subsequently, and the capacitance of the non-overlapping part can be com puted by subtraction.

As discussed above, the sensor arrangement comprises the sensor 100 and the electronic arrangement 120. Thus, it is possible to collect data from the sensor 100 and analyze and/or transmit the collected data by using the electronic arrangement 120.

The electronic arrangement 120 can be configured to obtain a signal indicating a value of interest from the sensor 100.

The electronic arrangement 120 may comprise,

- means for obtaining data (signals) from the sensor,

- optionally analyzing means,

- optionally transmitting means, such as a wireless component, and - a power supply.

The electronic arrangement 120 may comprise a processor, which can be config ured to process data coming from the sensor. The processor can be configured to analyze data based on signals of the sensor. For example, the processor can be programmed to calculate values representative of a value of interest.

The electronic arrangement 120 may comprise a memory. Thus, the electronic ar rangement 120 can store the values of parameters and calculations. Therefore, the electronic arrangement 120 can be configured to store the measurement results to the memory of the electronic arrangement 120. This allows for analyzing the meas urement data by using the electronic arrangement 120.

The electronic arrangement 120 may comprise an electronic chip 510 that is config- ured to convert capacitance(s) to digital form. Such chips are commonly known as a capacitance to digital converters (CDC). Thus, in an embodiment, the controller comprises a capacitance to digital converter.

Transmitting means of the electronic arrangement 120 may comprise a component for transmitting and, optionally, receiving data.

The transmitting means may be based on a wireless technology, such as

- Radio Frequency Identification (RFID),

- BT (Bluetooth), - Wireless Local Access Network (WLAN),

- Near Field Communication (NFC),

- Cellular systems 4G, or

- Cellular systems 5G but it may alternatively be based on any other wireless technologies.

Alternatively, instead of the wireless technologies, the transmitting means may be based on

- USB

- Ethernet - CAN

- LIN,

- MOST - FlexRay, or

- UART technology. Thus, in case of the wireless technology, the electronic arrangement 120 can com prise an antenna to provide wireless connectivity, and a communication insert, such as a communication circuit to perform communication via the antenna. The antenna can be incorporated in a communications circuit, or it may be separate from but in electric connection to the communications circuit. The communication insert can be coupled to a processor of the sensor, which can be linked to a transmitter further connected to an antenna.

Preferably, the transmitting means, i.e. , the transmitter, is configured to transmit value(s) based on the measurements of the sensor.

The electronic arrangement 120 of the sensor may be configured to transmit ob tained values, for example calibrated values, to an external unit 550 and/or to a cloud service unit 570. Thus, the electronic arrangement 120 of the sensor can cause that the obtained values are transmitted outside of the sensor 100.

In an embodiment, the electronic arrangement 120 comprises a circuit board 700, electrically coupled to the first sensing element 301; and an electronic chip 510 at tached to the circuit board 700. The electronic arrangement 120 of the sensor 100 may comprise one or more electronic chips 510, such as microchips. Thus, sensor 100 can comprise at least one circuit board 700 attached to the wiring 400 in an electrically conductive manner, and electrically coupled to the first sensing element 301. The circuit board is preferably a flexible circuit board. The flexible circuit board can improve deformability of the sensor. However, in another embodiment, the cir cuit board is only partly flexible. Further, the circuit board may not be flexible at all.

As for suitable materials for the circuit board 700, particularly for the flexible circuit board, these include polyimide, polyethylene naphthalate, polyethylene tereph- thalate, and polyetheretherketone. In an embodiment, the flexible circuit board 700 comprises material selected from a group consisting of these materials. Most pref- erably, the flexible circuit board comprises polyimide and/or polyethylene tereph- thalate. The flexibility of the flexible circuit board 700 is also a result of the board 700 being relatively thin. In an embodiment, a thickness of the flexible circuit board 700 is less than 1 mm, such as equal to or less than 0.5 mm or less than 0.4 mm.

In addition, the circuit board 700 may comprises electrically conductive wiring. An electric conductivity of the wiring of the circuit board 700 may be at least 1 S/m at a temperature of 20°C.

The electronic arrangement 120, when coupled to the sensor 100, may be config ured to measure the value of interest of at least one of the stretchable sensing ele ments 300, preferably each one of the stretchable sensing elements separately. In an advantageous embodiment, the electronic arrangement 120 is configured to measure the capacitance of each one of the stretchable sensing elements 300 sep arately.

The electronic arrangement 120 may comprise a data storage, such as at least one memory component. Alternatively, or in addition, the processor of the electronic ar rangement 120 may comprise memory. Thus, the electronic arrangement 120 can be configured to store the measurement results to a memory of the sensor arrange ment. This allows for analyzing the measurement data at least after measurements. The values representative of the value of interest can be calculated in the electronic arrangement 120 of the sensor.

The sensor may consume energy when its measuring and/or analyzing and/or trans mitting data and/or using the light source, such as LED(s). The sensor can comprise a power source, preferably an electric power source, such as a battery, to provide electricity for powering the functionality of the sensor 100.

The power source may be e.g. configured to transform mechanical and/or chemical energy to electric energy. As an alternative or in addition, the electric source may comprise a component configured convert magnetic energy into electricity. As an alternative or in addition, the electric source may comprise high-capacitance capac itor (e.g. a super capacitor) storing electric energy as such. Such a high-capacitance capacitor can be charged e.g. inductively or electrically with a component transform ing magnetic or mechanical energy, respectively, to electricity. Furthermore, the power source may comprise an energy harvesting device, such as a piezoelectric energy harvesting device, thermoelectric harvesting device, or a triboelectric energy harvesting device, which device may comprise a battery and/or a capacitor as one of its elements.

Preferably, the power source is a battery configured to provide electricity by con verting chemical energy into electricity. Therefore, it is possible to achieve simple and cost-effective solution. Preferably, the battery is rechargeable.

In an embodiment, data from the sensor 100 is not analyzed in connection to the sensor arrangement, in order to save energy consumption of the sensor arrange ment. In another embodiment, it is not necessary to save energy consumption of the sensor arrangement, hence, the data from the sensor 100 is preferably analyzed, at least partly, in connection to the sensor arrangement.

The transmitting means may be used to send at least some measured parameters from the sensor arrangement to the external control unit 550 or directly to a cloud service unit 570. The transmitting means may be configured to send the data to the external control unit 550 near the sensor arrangement in order to save energy. In an embodiment, an antenna may be arranged to wirelessly transmit information from the electronic arrangement 120 to a receiving device, e.g. the external control unit 550, located at a distance from the sensor. The values representative of the value of interest can be calculated in the external control unit 550 or cloud service unit 570. Thus, it is possible to save energy of the sensor arrangement. Alternatively, the values representative of the value of interest can be calculated in connection to the sensor arrangement, preferably by using the electronic chip 510, and optionally transmitted to the cloud service unit or to the external control unit 550. Thus, the cloud service unit 570 can make it possible for individuals to collect data and anal ysis the collected data in real-time, anywhere.

If the sensor arrangement comprises the circuit board 700, such as the flexible cir cuit board 700, it may be electrically coupled to the first sensing element 301 . More over, the electronic chip 510 can be attached to the circuit board 700 and configured to measure value, such as capacitance of the first sensing element. The electronic arrangement 120 can be configured to send the measurement results to an external control unit 550, for example by using an electronic chip 510. Therefore, the elec tronic chip 510 may be configured to send a signal Sin to an external control unit 550, or to a cloud service unit 570. Then, the external control unit 550 or the cloud service unit 570 may receive the signal Sin and determine following steps. The signal Sin may be sent via a wire or wirelessly. In an embodiment, the electronic arrange ment 120 is configured to send the data wirelessly. This allows for analyzing the measurement data in real time.

The external control unit 550 can be, for example, a mobile phone, a tablet, or a personal computer (such as a laptop computer). The external control unit can com prise a processor, a memory data storage unit (i.e. , a memory) for values, such as parameters and calculations, and a computer code to be executed by the processor, and a user interface having, for example, an operator display, and a keyboard (not shown in the Figures). The operator display can provide status information and warnings. The external control unit 550 can further comprise a sensor interface for receiving the outputs from the sensor. There can also be a power supply for supply ing power for the operation of the external control unit 550.

For communication purposes, the external control unit 550 may be equipped with a communication interface, which may be able to communicate with some other de vices, e.g. a cloud service unit, via short range and/or long-range communication connection. Thus, the external control unit 550 can be configured to communicate with a service provider, such as a mobile phone network.

The memory data storage unit of the external control unit 550 can store the values of parameters and calculations. Therefore, the external control unit 550 can be con figured to store the measurement results to a memory of the external control unit. This allows for analyzing the measurement data by using the external control unit 550.

In an embodiment, the electronic arrangement 120 stores at least the material com pensation coefficients 181 , hence, it is possible to calibrate the sensor easily, relia ble, and fast, by simply obtaining measurement results on the current surface, to obtain assembly compensation coefficients 182.

The memory of the electronic arrangement 120 may also store said assembly com pensation coefficients 182. Thus, it can be possible to calibrate the measured val ues easily, reliable, and fast.

The memory of the electronic arrangement 120 and/or the memory of the external control unit 550, may maintain history data at least for a predetermined time. Furthermore, the memory can be used, not only for storing the data, but also for storing computer code to be executed by the processor of the external control unit 550 and/or the electronic arrangement 120.

The computer code may use the material compensation coefficients 181 in order to obtain the assembly compensation coefficients 182. Thus, it is possible to calibrate the sensor on non-planar surfaces easily and fast. Calibration of the sensor on non- planar surfaces could be very slow and difficult operation without said material com pensation coefficients 181 comprising typically a function that includes an effect of temperature on the signals of the sensor as well as behavior of the sensor on planar surfaces.

The computer code may use the assembly compensation coefficients 182 in order to obtain calibrated values from measured signals. Thus, it is possible to obtain re liable data from non-planar surfaces.

The external control unit 550 may have a receiver or a receiver-transmitter, posi tioned to receive the digital data such as signals Sin transmitted by the transmitter of the sensor arrangement. When the external control unit 550 is used, a computer program may run on the external control unit 550. Such a computer program, when run on the external control unit 550, can be configured to cause the external control unit 550 to receive a signal Sin.

In an embodiment, a computer program, when run on the external control unit 550, is configured to cause the external control unit 550 to receive such raw signal S,_n that is indicative of a value measured by the sensor 100. Further, the computer pro gram, when run on the external control unit 550, can be configured to cause the external control unit 550 to determine a calibrated value from the signal Sin.

Alternatively, or in addition, the electronic arrangement 120 can have a receiver or a receiver-transmitter, positioned to receive the digital data. In addition, the elec tronic arrangement 120 can have a computer code which can be configured to cause the electronic arrangement 120 to determine a calibrated value from a raw value.

The measured value may be a value of a voltage, capacitance, resistance, or a current, if the value of the first sensing element is sent as an analogue signal. Preferably, the value is a digital value of the interest. Thus, the electronic arrange ment 120 is preferably configured to convert the measured signal to a digital signal.

Typically, measurements include noise. Therefore, even if there is not object in a vicinity of the sensor 100, a signal measured therefrom may not be constant. Thus, the signal is preferably filtered. Thus, in an embodiment, the effect of noise is re moved by filtering the data.

The electronic arrangement 120 and/or a system comprising the electronic arrange ment may be configured to determine material compensation coefficients 181. The material compensation coefficients can be determined for one sensor and, after ward, used for all similar sensors. The material compensation coefficients 181 can be determined, for example, for different temperatures and/or moistures. Further, the material compensation coefficients can be stored to a memory of the sensor, for example, during a manufacturing process of the sensor. Thus, it is not necessary to redetermine the material compensation coefficients 181 separately for each manu factured sensor. However, the material compensation coefficients can be calibrated, if wanted, for each manufactured sensor after the manufacturing process of said sensor.

Thus, as discussed, the material compensation coefficients 181 may need not to be determined separately for each of the sensors, but the material compensation coef ficients 181 can be determined once and afterward, when manufacturing sensors, the material compensation coefficients 181 can be stored to the memory of the sen sor.

The material compensation coefficients 181 may be used, for example, to determine assembly compensation coefficients 182 of the sensor on its current surface.

The electronic arrangement 120 and/or the external unit 550 may be configured to determine a calibrated value from a measured raw value. The calibrated value of the sensor can be determined based on the assembly compensation coefficients 182.

In an embodiment, the sensor arrangement and/or a system comprising the sensor arrangement can be configured to:

- obtain raw values (signals) by using the sensor 100, - optionally, determine filtered values from the raw values (signals),

- determine a calibrated value based on

- the raw values and/or filtered values, and

- the material compensation coefficients 181 and/or the assembly compensation coefficients 182

- optionally check the reliability of the data, for example by comparing the cal ibrated value with previously measured values.

Further, the electronic arrangement 120 and/or a system comprising the electronic arrangement may be configured to determine third reference values, i.e., a third curve 183, indicative of signals on installing position of the sensor 100, i.e., after installation of the sensor to a current surface (See Figs 5b, 6b and 8a) before recal ibration of the sensor. The current surface may be e.g. planar, curved, or double curved surface.

Further, the electronic arrangement 120 and/or a system comprising the electronic arrangement can be configured to determine assembly compensation coefficients (See Fig. 8b). The assembly compensation coefficients 182 are based on the ma terial compensation coefficients 181 , which are calibrated for the current form of the sensor.

The third reference values 183 indicating measured values before re-calibration (see Figs 6b and 8a) may be used together with the material compensation coeffi cients 181 to form assembly compensation coefficients 182 (see Fig. 8b). The as sembly compensation coefficients 182 can be used to determine calibrated values from signals of the sensor. Thus, the assembly compensation coefficients can be used to get calibrated measurement results, even when the sensor 100 is on a non- planar surface.

In an embodiment, the system comprising

- the sensor and

- the electronic arrangement 120 preferably comprising the electronic chip 510, and optionally the external unit 550, 570 may be configured to determine assembly compensation coefficients 182 for inter pretation of the measurement values. Furthermore, the system may be configured to determine corrected (calibrated) values from the raw signals or filtered signals based on the assembly compensation coefficients 182.

The external unit 550, 570 and/or the electronic arrangement 120 of the sensor may be configured to determine the calibrated values 182.

The external unit 550, 570, such as the external control unit 550 or the cloud service unit 570, and/or the electronic arrangement 120 of the sensor, may be configured to send an output signal S₀ut comprising the calibrated values. Correspondingly, the computer program, when run on the external unit 550, 570, and/or on the electronic arrangement 120 of the sensor, may be configured to generate such an output sig nal Sout that is indicative of the calibrated values.

The material compensation coefficients 181 may be stored on a memory, or they may be determined at a planar surface. The material compensation coefficients 181 can be used for determining the assembly compensation coefficients 182 simply by measuring at least one measurement by the sensor on its current position, without major calibration efforts. The assembly compensation coefficients can be used to determine calibrated values from signals of the sensor.

The assembly compensation coefficients 182 may be determined in installing posi tion of the sensor, i.e. , after an installation process of the sensor 100. An example of measurement ranges on a planar surface are generally illustrated in Fig. 5a and on non-planar surface without the calibration in Fig. 5b.

The determination of the material compensation coefficients 181 may comprise the following steps:

- measuring signals (outputs from sensing elements) of the sensor 100 on a planar surface,

- determining material compensation coefficients 181 , based on the measured signals.

In an embodiment, the sensor arrangement measures a temperature during the measurements. Furthermore, the material compensation coefficients 181 preferably include an effect of a temperature on the signals. Thus, the calibrated values can be reliable determined even if the assembly compensation coefficients 182 are formed fast, i.e., by using only the current temperature. The determination of the assembly compensation coefficients 182 may comprise, for example, the following steps: i) measuring signal(s) (output(s) from sensing element(s)) of the sensor 100 after installing the sensor on a surface, ii) determining values indicating that no object to be measured has an effect on the sensor on the surface, iii) comparing the measured signals to the material compensation coefficients 181 , iv) determining the assembly compensation coefficients 182 based on the ma terial compensation coefficients and the measured signals.

The method for determining a value of interest may comprise the following step:

- measuring at least one signal (output(s) from sensing element(s)) of the sen sor 100,

- optionally, transmitting at least some values based on the measured signals,

- comparing the signals and/or values determined from the signals to the as sembly compensation coefficients 182, and

- determining calibrated value(s) based on the measured signal(s) and the as sembly compensation coefficients 182.

As discussed above, the material compensation coefficients 181 may represent sig nals of the sensor on a planar surface (See fig. 5a, 6a). Thus, the material compen sation coefficients 181 may be calculated as a function of the electric values on a planar surface. The material compensation coefficients 181 may use a temperature as a variable. Thus, the measurement results can be improved.

The data showing the material compensation coefficients 181 may be stored to a memory of the electronic arrangement and/or external unit 550, 570. Thus, the ma terial compensation coefficients 181 can be determined only once, stored to a memory, and used when needed.

In an embodiment, the assembly compensation coefficients 182 can be calculated as a function of the electric values on an installing surface in which the sensor is positioned. The installing surface, in which the sensor is positioned, can be non- planar. The non-planar surface can be a curved or a double curved surface. The data showing the material compensation coefficients and/or the assembly compen sation coefficients 182 can be stored to a memory of the electronic arrangement and/or external unit 550, 570. Thus, the assembly compensation coefficients 182 may be calculated only once for each installation position, stored to a memory, and used when needed.

The electronic arrangement 120 and/or the external unit 550, 570 may be configured to determine the material compensation coefficients 181 and/or the assembly com pensation coefficients 182, wherein the assembly compensation coefficients 182 may be determined based on the material compensation coefficients, and signals measured on the second surface (i.e. , on the installing position of the sensor).

The system may comprise:

- means for collecting data from the sensor(s),

- a memory comprising the material compensation coefficients, and the assembly compensation coefficients 182,

- means for analyzing the collected data to form calibrated data based on the collected data and the assembly compensation coefficients.

In an embodiment, comparison of values can be done in the electronic arrangement 120. In an embodiment, the comparison is done in the external unit 550. Thus, the calibration, i.e. determination of calibrated value(s) based on reference values and measurement signals, may take place e.g. in the external unit 550, 570. The external unit 550, 570 may be configured to send an output signal S₀ut comprising the cali brated value. In addition, or alternatively, the electronic arrangement 120 may be configured to send an output signal Sin comprising the calibrated value.

The signal Sin, S₀ut may be indicative of a calibrated value(s) and/or material com pensation coefficients 181 and/or assembly compensation coefficients 182. Further more, the signal Sin may be indicative of uncalibrated, measured signal(s).

The assembly compensation coefficients 182 may be determined after installation process of the sensor, i.e., when the sensor is in its installation position. If the sensor is installed on a planar surface, the assembly compensation coefficients 182 may all be 1 . Therefore, only the material compensation coefficients might have an effect on the calibrated values if the sensor is installed on a planar surface. However, the sensor is also installable on a non-planar surface. Thus, the assembly compensation coefficients 182 may be needed for a reliable data. The measured signals can be applied with the assembly compensation coefficients 182 to deter mine forces affecting to the sensor in its installing position.

The installing position typically has an effect on the signals of the sensor. Thus, the signals of the sensor may show different values on different surfaces even when no object is affecting the sensor (See Figs 5a-b). The assembly compensation coeffi cients 182 represent coefficients needed for the signals in installing position of the sensor, on the current surface. If the sensor 100 is installed to another surface, or is in another form on the current surface, new assembly compensation coefficients can (and typically should be) determined.

As discussed above, the sensor 100 may be configured to provide signals. The electronic arrangement 120 can be configured to read signals of the sensor 100. The system may be configured to

- determine material compensation coefficients on a planar surface, and/or to use the material compensation coefficients stored to a memory, and/or

- determine assembly compensation coefficients 182 in an installing position of the sensor, and/or to use the assembly compensation coefficients stored to a memory, and/or

- determine a calibrated value from the read signals by using the assembly compensation coefficients.

The material compensation coefficients 181 are preferably determined before first installation of the sensor 100.

The assembly compensation coefficients 182 are preferably determined for each installing position of the sensor, or each time a form of the sensor changes.

In accordance with an embodiment, at least some of data collected from the sensor is saved in order to form history data. This history data can be analyzed and/or compared, for example, to the material compensation coefficients. Alternatively, or in addition, this history data can be analyzed and/or compared to the assembly com pensation coefficients. Alternatively, or in addition, this history data may be analyzed and/or compared to new measurement signals. Thus, it is possible to determine, for example, if the in stallation surface is changing. Thus, the sensor can be used to determine a need for a maintenance of the object, onto which the sensor is installed. Therefore, the sensor can be configured to notice a need for a maintenance of an object in which the sensor is positioned.

Thus, the system may be configured to compare at least one uncalibrated value based on at least one new measurement to at least one other uncalibrated value stored to memory, which said at least one other uncalibrated value was preferably obtained right after the sensor was installed to the current surface.

The difference between the at least one new value and the at least one stored value may be used to determine whether the installing surface in which the sensor is po sitioned is still in suitable condition. Then, the system can be configured to display whether the installing surface in which the sensor is positioned is still in suitable condition.

Optionally, the collected data, or at least some of the collected data is shown to a user using a local display. The external unit 550, 570 may be configured to display a value of interest, such as a pressure and/or force e.g. for a user.

The electronic arrangement 120 of the sensor 100 can be fixedly positioned close to the first sensing element 301. The electronic arrangement 120 may serve as a reading device. Such an arrangement enables reliable interaction between the first sensing element and the electronic arrangement 120.

As discussed, the sensor 100 can comprise transmitting means for transferring at least some of the measured data (the outputs of the sensor 100) to, for example, an external control unit 550.

In an embodiment, the electronic arrangement 120 is configured to receive data from another sensor. Moreover, in an embodiment, the electronic arrangement 120 is configured to send such data to another external control unit. In this way, multiple sensors can send measurement data via other sensors, for example, to the external control unit 550. In an embodiment, the external unit 550, 570 is configured to receive data from multiple sensors, for example, from at least 3 sensors.

The sensor may comprise the elastic, deformable layer 130A, 130B. At least this elastic, deformable layer 130A, 130B is deformable, i.e. it can deform in use. As a result, the measured values of a sensing element 300 may change. This change can be used for measurements. Furthermore, this change can be used to calibrate the sensor by determining the assembly compensation coefficients 182.

The shape of the sensor 100 (in use) may be, for example, planar, curved, or double curved. Moreover, its shape may be different from the shape when stored. For ex ample, the sensor 100 can be stored in a planar form and, in use, the shape may conform to the shape of the surface in which the sensor is positioned.

In an embodiment, the sensor 100 may comprise a top layer 201 . A thickness of the top layer may be e.g. at least 0.1 mm, preferably as at least 0.3 mm. In this case, at least a part of the first wire 401 , and the elastic layer(s) 150, 130A, 130B may be arranged on a same side of the top layer. The top layer may be finished e.g. for visual appearance of the sensor and/or for improved comfort of use. Preferably, the top layer is made of textile (synthetic or natural). In an embodiment, the top layer comprises fibrous material. In an embodiment, the top layer comprises woven fi brous material. The top layer may comprise one or more non-transparent areas. Further, the top layer may comprise one or more transparent and/or translucent ar eas and/or at least one hole.

In some applications, the reliability of the sensor 100 may be improved by applying a bottom layer. In this embodiment, a thickness of the bottom layer may be e.g. at least 0.1 mm, such as at least 0.5 mm. When the bottom layer is attached to the first wire 401 , optionally via other parts of a multilayer structure, also the bottom layer provides for mechanical support for the wire 401 , and in this way improves reliability. At least a part of the first wire 401 can be arranged in between the elastic layer 130A, 130B, 150 and the bottom layer in the direction Sz of the thickness Sz of the sensor. The material of the bottom layer may be selected according to needs. In case the bottom layer needs to be conformable and/or configured to be compressed in use, the material of the bottom layer may be selected from the group consisting of polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, poly- borodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene- butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel. However, for example, in case it suffices that the bottom layer is flexible, also a material selected from the group consisting of polyimide, polyethylene naphthalate, polyethylene terephthalate, and polyether- etherketone can be used.

As discussed above, the sensor may comprise at least one layer, for example 2 - 10 layers. The sensor may comprise, for example,

- 1 to 6 insulating layers,

- 1 or 2 electrode layers 300, and

- 0 to 3 electrically permeable and/or conductive layers.

Preferably, at least some of said layers are transparent and/or translucent layers and/or comprise one or more transparent and/or translucent areas.

In an embodiment, a system comprising

- the sensor having the above-mentioned number of layers, and

- the computer code using the assembly compensation coefficients 182 in order to obtain calibrated values from measured signals can be used to obtain reliable data from non-planar surfaces.

For example, a structure comprising at least 3 insulating layers and 2 electrode lay ers may be used to measure pressure more accurately than e.g. the structure having only one electrode layer. However, the layered sensor structure having many layers is more complex than a sensor comprising only some layers, whereby it would be more expensive to manufacture.

In an embodiment, if the sensor 100 comprises two electrically permeable and/or conductive layers 140, 142, an insulating layer may be arranged in between each of the electrically permeable and/or conductive layers 142 and electrodes 321 , 322. Thus, an insulating layer may be arranged in between the first electrically permeable and/or conductive layer 140 and the electrodes 301 , 302 and between the second electrically permeable and/or conductive layer 142 and the electrodes 301 , 302.

As for the material of the first electrically permeable and/or conductive layer 140, the first electrically permeable and/or conductive layer 140 may comprise at least one of

- electrically conducting material made from conductive ink, - electrically conductive fabric, and

- electrically conductive polymer, such as a film made of the polymer, which electrically conductive polymer may comprise transparent and/or translucent material used for transparent and/or translucent area(s). These materials can be used to obtain an improved sensor.

In an embodiment, conductive polymer-based material may serve as the material for the conductive area(s), such as electrically permeable and conductive layer 140, 142. Such conductive polymer-based material typically comprises conductive parti- cles, such as flakes or nanoparticles, attached to each other in an electrically con ductive manner. In an embodiment, the electrically conductive particles comprise metal (e.g. copper, aluminum, silver, gold) or carbon (including, but not limited to graphene and carbon nanotubes). In addition, conductive polymer-based materials include polyaniline, a polyvinyl (e.g. polyvinyl alcohol or polyvinyl chloride), and PEDOT:PSS (i.e. poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), which may be used as the material for the conductive area(s). Said materials may be par ticularly advantageous for the properties of the sensor.

The first electrically permeable and/or conductive layer 140, if used, may comprise one or more transparent and/or translucent areas, hence, the first electrically per meable and/or conductive layer 140 may comprise transparent and/or translucent material, such as the PEDOT:PSS (i.e. poly(3,4-ethylenedioxythiophene) polysty rene sulfonate). The conductive area(s) may be formed of conductive lines, filaments, or yarns cross ing each other, whereby non-conductive area(s) may be arranged in between the conductive lines, filaments, or yarns. The electrically permeable and conductive layer 140, 142 may be a woven layer (i.e. fabric) made of conductive yarn. Such conductive fabric includes the yarns as the conductive areas and non-conductive areas in between the yarns. Said materials may be particularly advantageous for the properties of the sensor.

The first electrically permeable and/or conductive layer 140, if used, may be uni formly conductive, e.g. by using conductive ink or paste a uniform amount on a uni- form surface. The conductive ink may also form the non-transparent area(s) of the sensor comprising one or more transparent and/or translucent areas. In the alternative, the first electrically permeable and/or conductive layer 140, if used, may be a mesh of conductive yarns, e.g. made using conductive ink or paste or filaments. In an embodiment, at least a part of the first electrically permeable and/or conductive layer 140 is made from a conductive ink. In an embodiment the first electrically permeable and/or conductive layer 140 comprises electrically con ductive fabric. In an embodiment, the first electrically permeable and/or conductive layer 140 comprises electrically conductive polymer. Preferably, the first electrically permeable and/or conductive layer 140 is uniformly conductive. This may improve the reliability of the sensor.

What has been said about the material of the first electrically permeable and/or con ductive layer 140 applies to the material of the second electrically permeable and/or conductive layer 142.

The sensor 100 may comprise stretchable electrodes. The sensor may comprise a layer or layers that is/are stretchable and/or deformable. The stretchability and the deformability can improve an installability of the sensor. The sensor may further comprise one or more layers, which may comprise one or more transparent and/or translucent area(s) and/or prisms. The transparent and/or translucent area(s) may be used to obtain an illumination solution providing information to a user. Preferably, the transparent and/or translucent area(s) and/or prisms are a part of an illumination arrangement of the sensor.

In an embodiment shown in Figure 1 d , the sensor has a quite complex structure. Int this embodiment, the layer 200 may comprise e.g. prisms. The sensor may com prise a first electrically permeable and/or conductive layer 140 and a second elec trically permeable and/or conductive layer 142. For proper functionality, the second electrically permeable and/or conductive layer 142 may overlap in the direction of thickness of the sensor with [i] the whole area of the first primary electrode 301 , [ii] the whole area of the second primary electrode 302, [iii] the whole area of the first secondary electrode 321 , and [iv] the whole area of the second secondary electrode 322. When the sensor comprises the electrically permeable and/or conductive layer(s) 140, 142 and further electrodes, the second electrically permeable and/or conductive layer 142 preferably overlaps in the direction of thickness of the sensor with all the electrodes. In an embodiment, the first secondary electrode 321 may be arranged in a direction of thickness Sz of the sensor 100 in between the second electrically permeable and/or conductive layer 142 and the flexible and stretchable layer 200. Moreover, a part of second elastic deformable layer 130B can be arranged in between the first secondary electrode 321 and the second electrically permeable and/or conductive layer 142. More specifically, a part of second elastic deformable layer 130B can be arranged

[A] in between the first primary electrode 301 and the second electrically permeable and/or conductive layer 142 and

[B] in between the first secondary electrode 321 and the second electrically perme able and/or conductive layer 142.

The primary electrode(s) 301 , 302 and the secondary electrode(s) 321 , 322 can be left in between the second electrically permeable and/or conductive layer 142 and the first elastic deformable layer 130A in the direction Sz of the thickness of the sensor 100. Also, the wirings 400 can be left in between the second electrically per meable and/or conductive layer 142 and the first deformable layer 130A in the di rection Sz of the thickness of the sensor 100.

Advantageously, the sensor is a capacitive sensor. Alternatively, the sensor may be e.g. a resistive sensor, or a piezoresistive sensor. Working principles of these sen sors are known to a skilled person. The novel sensor may be particularly advanta geous when said sensor is one of said sensors.

Therefore, the sensor can be a capacitive sensor; hence, it can be configured to sense variations of capacitance and provide an output representative of the varia tions. The sensor can be a capacitive sensor suitable to be positioned on double curved surfaces. The capacitive sensor can be, for example, a force and/or pressure sensor.

Typically, a capacitance of an electrode 300 relative to its surroundings changes, when an object is moved close to or away from the electrode. A second electrode (layer) is not necessarily needed, but two electrodes can be used for improved ac curacy in such a way that material in between the electrodes can be compressed in use. When multiple electrodes are used at different locations, multiple local pres sures can be determined at different locations. In touch sensors, the touching object (e.g. finger of a user) has a different dielectric constant than e.g. air. Thus, a capac itance of an electrode typically changes by movement of the touching object. In an embodiment, the sensor 100 comprises

- the second elastic deformable layer 130B and the second electrically perme able and/or conductive layer 142, and

- the first deformable layer 130A and the first electrically permeable and/or conductive layer 140.

The second electrically permeable and/or conductive layer 142 is preferably ar ranged on a first side of the elastic, deformable layer 130B and the first secondary electrode 321 is arranged on a second, opposite, side of the elastic, deformable layer 130B. In an embodiment, the electrodes 300 and at least a part of the wirings 400 are arranged on the second, opposite, side of the second elastic, deformable layer 130B. Correspondingly, a part of the second elastic, deformable layer 130B is left in between the second electrically permeable and/or conductive layer 142 and the first secondary electrode 321 in the direction Sz of the thickness of the sensor 100. Both the two electrically permeable and/or conductive layers 140, 142 and the two elastic, deformable layers 130A, 130B can improve the accuracy of capacitive measurements. In addition, the flexible and stretchable layer 200 in between the two elastic, deformable layers can simplify the manufacturing process. Furthermore, the mutual arrangement of electrodes and wiring can improve measurement accuracy, particularly for force, and without compromising reliability. Large electrodes (i.e. large coverage of electrodes) may be needed when the force is measured, since the force is an integral of pressure over the surface on which the force acts on. Thus, the pressure needs to be known at substantially all locations within the sensor to accurately determine the force.

The sensor may comprise dummy wires and/or ground electrodes. In this case, to improve the structure of the sensor, the shape of a dummy wire can be substantially similar to a shape of a wire adjacent thereto.

In accordance with an embodiment, the system comprises

- analyzing means for analyzing data collected from the sensor in order to de termine a force and/or pressure and/or another value of interest based on the collected data and the assembly compensation coefficients 182.

In capacitive sensors, the capacitance of an electrode is measured. The capaci tance can be measured relative to surroundings or relative to another electrode, such a ground electrode. In general there are three working principles: (1 ) the dielectric material close to the electrode (e.g. in between two electrodes) changes, which changes the capacitance; and/or (2) the distance between two electrodes changes, which changes the capacitance in between these electrodes; and/or (3) an area of an electrode changes or a mutual area between two electrode changes, which changes the capacitance of the electrode (e.g. relative to another electrode or surroundings). The mutual area may change e.g. under shear load. These prin ciples are known to a skilled person.

With the sensor structure as discussed above, it can be possible to measure a ca pacitance of a stretchable sensing element 300 relative to something. The capaci tance can be measured relative to another sensing element 300. The sensing ele ment may be an electrode, and e.g. all other stretchable electrodes 300 may form a common ground, relative to which the capacitance may be measured. Thus, subse quently, the capacitance of all the stretchable electrodes 300 can be measured. This, however, decreases the sampling rate. It is also possible to measure capaci tance relative to surroundings. This, however, may not give accurate results.

For example, force and/or pressure can be measured by using the capacitive sen sor. Thus, the electronic arrangement 120 may be an integral part of the sensor 100 for capacitively detecting force and/or pressure. Thus, the sensor can be configured to sense variations of capacitance and provide an output representative of a pres sure and/or force.

If the sensor 100 comprises two electrically permeable and/or conductive layers 140,142, the system may be configured to measure the capacitances from at least the whole area of the first primary electrode 301 , the whole area of the second primary electrode 302, the whole area of the first secondary electrode 321 , and the whole area of the second secondary electrode 322 relative to both the first and second electrically permeable and/or conductive layers 140,142.

In an embodiment, wherein the sensor comprises at least one electrically permeable and/or conductive layer 140,142; the electronic arrangement 120 may be configured to measure:

- the capacitance from the whole area of the first primary electrode 301 relative to the electrically permeable and/or conductive layer (or layers) at one in stance of time; - the capacitance from the whole area of the second primary electrode 302 relative to the electrically permeable and/or conductive layer (or layers) at one instance of time;

- the capacitance from the whole area of the first secondary electrode 321 rel ative to the electrically permeable and/or conductive layer (or layers) at one instance of time; and

- the capacitance from the whole area of the second secondary electrode 322 relative to the electrically permeable and/or conductive layer (or layers) at one instance of time.

These instances of times may be the same or they may be different.

The elastic, deformable layer 130A, 130B, 150 may be arranged in between the electrodes 300 and the first electrically permeable and/or conductive layer 140.

The first electrically permeable and/or conductive layer 140 may serve as a ground electrode, relative to which the capacitance of each of the stretchable electrodes 300 is measured. In such a configuration, the compression of the deformable layer 130A, 130B,150 affects the distance between two electrodes. As known to a skilled person, the capacitance of such a capacitor formed by said two electrodes is in versely proportional to the distance between the electrodes. By measuring the ca pacitance, the distance between the electrodes can be calculated. From the dis tance, the strain within the elastic layer 150,130A can be determined. Since the material of the elastic layer 150,130A is known, the strain defines the stress (i.e. pressure) within the elastic layer 150, 130A. In this way, pressure at each stretcha ble electrode can be determined. Moreover, since the effective area of the stretch able electrode is known, the force affecting at that stretchable electrode can be de termined. Finally, provided that the electrodes cover substantially the whole cross- sectional area of the sensor, the total force can be measured, when the assembly compensation coefficients, relating to a shape of a surface of the installing position of the sensor, are known.

The sensor 100 can be configured to sense pressure and/or force acting in a direc tion having a component in the direction Sz of the thickness of sensor 100. Corre spondingly, a thickness of at least elastic, deformable layer (e.g. 130A or 130B) can be configured to decrease under pressure. The sensor 100 can be relatively thin. That is, the thickness is less than the smaller of length and width. In some applications, such as pressure sensing applications, the thickness tioo of the sensor can be e.g. from 1 mm to 5 mm, in order to optimize measurement accuracy. In some other applications, such as touch based HMI, the thickness t-ioo of the sensor is preferably from 0.05 mm to 1.0 mm, in order to opti mized thinness and conform ability of the sensor. Further, in some other applications, such as a strain gauge, the thickness t-iooof the sensor can be e.g. from 0.02 mm to 0.5 mm for optimizing thinness and decreasing manufacturing cost of the sensor.

Generally, for example in a force sensor, substantially all the measurement area should be covered by the electrodes used for measurements, while for example in a pressure sensor is suffices to provide electrodes used for measurements only to such areas, where the pressure is to be measured. In order to be able to measure the force (i.e. total force) in addition to pressure (i.e. local pressure), preferably sub stantially all the measurement area should be covered with the stretchable elec trodes 300. Thus, the aforementioned distance di may advantageously be small. On the other hand, if the distance di is too small, neighboring electrodes 300 may capacitively couple to each other, which may disturb the measurements.

Generally, in the sensors 100 configured to sense pressure and/or force, a thickness of the flexible and stretchable layer may be e.g. up to 5 mm. In an embodiment, a thickness of the flexible and stretchable layer 200 that does not act as a compress ible layer may be e.g. less 1 mm, such as less than 0.5 mm, e.g. from 20 pm to 1 mm or from 50 pm to 0.5 mm.

In order to have reasonable deformations, a thickness of the elastic, deformable layer(s) 130A, 130B may be from 0.05 mm to 5 mm, more preferably from 0.3 mm to 4 mm, and most preferably from 0.5 mm to 2 mm.

In the sensors 100 configured to sense pressure and/or force, a thickness of the elastic, deformable layer(s) 130A, 130B in order to have reasonable deformations, may be at least 0.05 mm, preferably at least 0.3 mm such as at least 0.5 mm.

Each one of the stretchable electrodes 300 can be arranged some distance d-ij_j apart from all other ones of the stretchable electrodes 300. The number of stretch able electrodes electrically insulated from each other by said distance d-ij_j typically correlates with the spatial accuracy of the sensor. The more electrodes 300 are used, the better the spatial accuracy. In a preferred embodiment, the number of stretchable electrodes is at least twenty, such as between 20 and 50.

Preferably, the first wire 401 connects only the first electrode 301 to the electronic arrangement 120 and the second wire 402 connects only the second electrode 302 to the electronic arrangement 120. This has the effect that, for example, the capac itances of the first and second electrode 301 , 302 can be measured without multi plexing, which improves the temporal accuracy of the measurements. Thus, prefer ably, the electrode layer 300 comprises a second electrode 302 and a second wire 402 attached to the second electrode 302. This has the effect that the spatial accu racy of the capacitive measurements is improved. However, the capacitance may also be determined by multiplexing.

The first elastic, deformable layer 130A, if used, can be configured to be com pressed and deform under pressure in use. In particular, if the sensor is deformable and flexible, the flexibility allows for measurements of a pressure distribution with a high spatial accuracy, provided that a sufficient number of electrodes is used. The high number of individual electrodes may also improve the temporal accuracy, as indicated above.

The sensor 100 may be deformable due to material selections and a reasonably thin layered structure. The shape and/or the thickness of the sensor 100 can be adapted to the shape of the installing surface in which the sensor is positioned. Therefore, the sensor is particularly suitable for use on a curved surface. In an advantageous embodiment, the sensor 100 is suitable to be attached on double curved surfaces. Thus, particularly in use, the sensor 100 needs not to be planar.

Such a sensor can be used in various application including, but not limited to, vehi cles and furniture. Thus, the installing surface in which the sensor is positioned can be, for example, a double curved surface of a vehicle. Furthermore, the sensor may be used in smart furniture, and objects inside a vehicle. For example, if the installing surface is a surface of a vehicle, the illumination solution can be used to indicate a certain area and/or a symbol in which a touch of a user may have an effect.

The sensor 100 can be best suited for applications, wherein a stretchable illumina tion arrangement can be used to indicate a certain area and/or a symbol on a sur face of the sensor. Humidity or water may affect the measurement results. In particular, if the moisture come close to sensing elements, particularly electrodes, the moisture may affect the measurements a lot. Therefore, in an embodiment, the material compensation co efficients 181 include an information of an effect of moisture on the signals of the sensor.

Further, a temperature may affect the measurement results. Thus, in an embodi ment the material compensation coefficients 181 preferably include an effect of tem perature on the signals of the sensor.

Furthermore, the material compensation coefficients 181 may include information from

- stress vs. strain, and/or

- temperature vs. strain, and/or

- strain vs. resistance, and/or

- creep over time.

Thus, it is possible to obtain very reliable measurement results.

Thanks to the present invention, the illumination arrangement can be used to indi cate a certain area and/or a symbol on a surface of the sensor in which a touch of a user may have an effect. Further, a value of interest, such as a pressure and/or force, can be monitored on complex surfaces, such as double curved surfaces and surfaces which deform in use.

Example 1

Several touch / force sensors each comprising prisms, and/or transparent areas and/or translucent areas, and a light mask, were manufactured. The transparent and/or translucent areas and/or prisms together with a stretchable ink and a light source provided the illumination solution. Some of the sensors had a separate top layer. For example, the top layers shown in Figs 10b-c comprised 68 % polyamide and 32 % elastane (EA), grammage being 220 g/m²

The manufactured sensors having the illumination arrangement according to this specification gave reliable measuring results also from curved and double curved surfaces. The invention is not limited solely to the examples presented in Figures and the above description, but it may be modified within the scope of the appended claims.

Claims

1. A sensor arrangement comprising a sensor suitable to be attached to a curved surface, wherein the sensor arrangement comprises a first stretchable sensing element (301 ), and a stretchable electrically conductive wiring (400), wherein

- the first stretchable sensing element (301) is able to stretch at least 5 % at a temperature of 20°C without breaking, and - the stretchable electrically conductive wiring (400) is able to stretch at least 5

% at a temperature of 20°C without breaking, wherein the sensor arrangement further comprises an electronic arrangement (120) electrically coupled to the first stretchable sensing element (301 ) via the stretchable electrically conductive wiring (400), which electronic arrangement (120) is config- ured to obtain a first signal from the first stretchable sensing element (301 ), wherein the sensor arrangement further comprises an illumination arrangement comprising a light source (10), wherein at least part of light from the light source (10) is guided via and/or through at least one layer of the sensor from the light source (10) on to a first surface of the sensor in order to illuminate at least part of the first surface of the sensor.

2. A product comprising a sensor arrangement attached to said product, wherein the sensor comprises a first stretchable sensing element (301), and a stretchable electrically conductive wiring (400), wherein

- the first stretchable sensing element (301 ) is able to stretch at least 5 % at a temperature of 20°C without breaking, and

- the stretchable electrically conductive wiring (400) is able to stretch at least 5 % at a temperature of 20°C without breaking, wherein the sensor arrangement further comprises an electronic arrangement (120) electrically coupled to the first stretchable sensing element (301 ) via the stretchable electrically conductive wiring (400), which electronic arrangement (120) is config ured to obtain a first signal from the first stretchable sensing element (301), wherein the sensor arrangement further comprises an illumination arrangement comprising a light source (10), wherein at least part of light from the light source (10) is guided via and/or through at least one layer of the sensor from the light source (10) on to a first surface of the sensor in order to illuminate at least part of a surface of the product, thereby forming a visible illuminated symbol on the surface of the product.

3. The product or the sensor arrangement according to any of the preceding claims comprising a light mask (112), preferably a stretchable light mask which is able to stretch at least 5 % at a temperature of 20°C.

4. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises a flexible and stretchable layer (200), which is able to stretch at least 5 % at a temperature of 20°C without breaking.

5. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises an elastic, deformable layer (130A, 130B) having a Young’s modulus of at least 0.01 MPa and a first yield strain at least 10 per cent at a temperature of 20°C.

6. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises at least one layer comprising integrated prisms.

7. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises at least one layer comprising perforations and/or openings.

8. The product or the sensor arrangement according to any of the preceding claims, wherein the stretchable electrically conductive wiring (400) comprises a con ductive ink.

9. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises an electrically permeable and/or conductive layer (140, 142).

10. The product or the sensor arrangement according to any of the preceding claims, wherein the light from the light source is guided from a side of the sensor on to the first surface of the sensor.

11 . The product or the sensor arrangement according to any of the preceding claims, wherein the light from the light source is guided from a second side of the sensor through the sensor onto the first surface of the sensor.

12. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor is a force sensor.

13. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor is a touch sensor.

14. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises a transparent and/or translucent adhesive.

15. The product or the sensor arrangement according to any of the preceding claims, wherein the first stretchable sensing element (301 ) comprises a transparent and/or translucent area.

16. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor is configured to form said first signal due to a touch of a user on the illuminated visible symbol.

17. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises

- at least one transparent area having a transparency value in a range between 10% and 98%, and/or

- at least one translucent area having a transparency value in a range between 10% and 98%, wherein more than 10% of light deviates from the incident beam by at least 2.5 degrees when passing through at least one material layer of the sensor.

18. The product or the sensor arrangement according to claim 17, wherein at least part of the light from the light source is configured to go through said at least one transparent and/or translucent area.

19. The sensor arrangement according to any of the preceding claims 17 to 18, wherein said transparent and/or translucent area is configured to work as a light guide.

20. The product or the sensor arrangement according to any of the preceding claims, wherein a measuring area of the sensor is adjacent to a/the light guide.

21. The product or the sensor arrangement according to any of the preceding claims 1 to 19, wherein a measuring area of the sensor overlaps a/the light guide.

22. The product or the sensor arrangement according to any of the preceding claims, wherein a/the measuring area of the sensor is at least partly on a/the light guide.

23. The product or the sensor arrangement according to any of the preceding claims, wherein the light source (10) comprises at least one LED.

24. The product or the sensor arrangement according to any of the preceding claims, wherein the light source (10) comprises at least one display.

25. The product or the sensor arrangement according to any of the preceding claims, wherein the stretchable electrically conductive wiring (400) comprises one or more transparent and/or translucent areas having a transparency in a range be tween 10% and 98%.

26. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor is one of the following:

- a capacitive sensor,

- a resistive sensor, or

- a piezoresistive sensor.

27. The product or the sensor arrangement according to any of the preceding claims, wherein the first stretchable sensing element (301) comprises or is made of a non-transparent conductive ink.

28. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor arrangement further comprises:

- analyzing means configured to determine a calibrated value based on the obtained first signal and assembly compensation coefficients, which assem bly compensation coefficients are based on material compensation coefficients, and - at least one other measured signal of the sensor, which said at least one other measured signal was measured in an installing position when no object to be measured had an effect on the sensor.

29. The product or the sensor arrangement according to claim 28, wherein

- the sensor arrangement comprises a temperature sensor, and the material compensation coefficients include an effect of temperature on the first signal, and/or

- the sensor arrangement comprises a moisture sensor, and the material com pensation coefficients include an effect of moisture on the first signal of the sensor.

30. The product or the sensor arrangement according to any of the preceding claims 28 to 29, wherein the material compensation coefficients include - an effect of material(s) of the sensor on the first signal of the sensor and/or

- an effect of a structure of the sensor on the first signal of the sensor.

31 . The product or the sensor arrangement according to any of the preceding claims 28 to 30, wherein the analyzing means are further configured to - obtain said first signal when no object to be measured has an effect on the sensor,

32. The product or the sensor arrangement according to any of the preceding claims 28 to 31 , wherein the sensor arrangement is configured to

- use the material compensation coefficients stored to a memory.

33. The product or the sensor arrangement according to any of the preceding claims 28 to 32 wherein - the sensor arrangement is configured to determine the assembly compensa tion coefficients (182) in an installing position of the sensor when no object to be measured has an effect on the sensor, and/or

- the assembly compensation coefficients (182) are stored to memory of the electronic arrangement (120).

34. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor further comprises a second stretchable sensing element (302) arranged a first distance apart from the first stretchable sensing element (301 ), wherein the electronic arrangement (120) is further coupled to the second stretcha ble sensing element (302) via the wiring (400), and configured to obtain a second signal from the second stretchable sensing element (302).

35. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor is capable of being shaped into

- a double curved form and/or

- a curved form, without breaking.

36. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor comprises

- elastic, deformable layer (130A, 130B) and

- stretchable layer (200) in such a way that the stretchable layer (200), the stretchable electrode(s) (300, 301 , 302), and the electrically conductive wiring (400) are left on a same side of the elas tic deformable layer (130A).

37. The product or the sensor arrangement according to any of the preceding claims, wherein

- the sensor comprises an insulating layer and the sensor further comprises an/the electrically permeable and/or conductive layer (140, 142), and

- the electronic arrangement (120) is preferably electrically coupled to the elec trically permeable and/or conductive layer (140, 142).

38. The product or the sensor arrangement according to any of the preceding claims, wherein the sensor arrangement is attached to its position

- mechanically, and/or - by using an adhesive.

39. The product or the sensor arrangement according to any of the preceding claims, wherein each stretchable sensing element is a stretchable electrode.

40. The product according to any of the preceding claims 2 to 39, wherein the product is a vehicle.

41. A use of the sensor according to any of the preceding claims for Human-Ma- chine Interface (HMI) for touch and/or pressure sensor - based operation of a vehi cle’s functions.