GB2602973A

GB2602973A - A deformable sensing layer and methods

Info

Publication number: GB2602973A
Application number: GB2100748.9A
Authority: GB
Inventors: Richardson Liam; Sebastian Tobon Conde Juan
Original assignee: Hyve Dynamics Holdings Ltd
Current assignee: Hyve Dynamics Holdings Ltd
Priority date: 2021-01-20
Filing date: 2021-01-20
Publication date: 2022-07-27
Anticipated expiration: 2041-01-20
Also published as: GB202100748D0; GB2602973B

Abstract

The invention relates to a deformable sensing layer comprising an array of variable impedance sensors 12 disposed on or in a deformable substrate in a substantially grid-like pattern having rows and columns, wherein each variable impedance sensor includes a first electrode connected by a conductor line 16 and a switch 18 to the first electrode of at least one variable impedance sensor on the same row and a second electrode which is connected by a conductor line 17 to the second electrode of at least one variable impedance sensor on the same column, wherein each variable impedance sensor 12 in the grid of variable impedance sensors is individually measurable by controlling the state of each switch 18 and which row and column receives an excitation signal. The invention may also comprise a method of selecting which sensor in the array of sensor is selected and a method of collecting data using the deformable sensing layer. Also disclosed is the use of the deformable sensing layer to collect data relating to fluid flow over an object.

Description

A DEFORMABLE SENSING LAYER AND METHODS

The present invention relates to a deformable sensing layer and particularly but not exclusively to a deformable sensing layer with an array of sensors which can be individually measured. The present invention also relates to a method of individually measuring an array of sensors in a deformable sensing layer and a method of collecting data using a deformable sensing layer with an array of sensors.

BACKGROUND TO THE INVENTION

Flexible and/or stretchable sensors are a recent development and are an area of great interest within research. These types of sensors usually consist of an array of individual sensors and are commonly used in 2-dimensional pressure sensing, that is to say they measure a force acting over an area by taking readings over that area. Mechanisms used for sensing can vary, but include electrical resistance such as US6912759, capacitance such as Bakhoum E G et al, "Capacitive pressure sensor with very large dynamic range", IEEE Transactions on Components and Packaging technologies 33.1 (2009) 83, and piezoelectricity.

Existing stretchable and/or flexible sensor arrays can be of limited use when precise readings are required because neighbouring sensors can reduce resolution by introducing noise within the readings.

Multi-touch sensing has become important with the increased use of touchscreen or similar input technologies. For example, US20090322700 describes a complex technical arrangement which uses a resistive sensing mechanism to detect two simultaneous touches. The variation in electrical resistance of a single sensor in a grid may be small, which makes it difficult to have a high degree of location accuracy because variation in the resistance of neighbouring sensors may interfere. This may be compounded when multiple points of pressure are applied.

In another example, US6825833 describes a system and method for locating a touch on a capacitive touch screen. With this, and similar capacitive technologies, the ability to detect multiple touches reduces the ability to read variable pressure levels.

Another technique known as electrical impedance tomography uses a flexible and/or stretchable sensor to create a pressure map. However, unlike other flexible and/or stretchable sensors the array of point sensors on the sensing surface is replaced with current carrying and voltage sensing electrodes attached to a flexible conductive medium, such as that discussed in Yao A et al "A pressure mapping imaging device based on electrical impedance tomography of conductive fabrics" Sensor Review (2012). This technology is versatile but the resolution of the pressure images decreases as the volume of the measured medium increases.

It is an object of the present invention to reduce or substantially obviate the aforementioned problems.

STATEMENT OF INVENTION

According to a first aspect of the present invention there is provided a deformable sensing layer comprising an array of variable impedance sensors disposed on or in a deformable substrate in a substantially grid-like pattern having rows and columns, wherein each variable impedance sensor includes a first electrode connected by a conductor line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode which is connected by a conductor line to the second electrode of at least one variable impedance sensor on the same column, wherein each variable impedance sensor in the grid of variable impedance sensors is individually measurable by controlling the state of each switch and which row and column receives an excitation signal.

By providing a deformable sensing layer, or a deformable sensing device comprising the deformable sensing layer, for measuring an environmental condition such as pressure, temperature, strain, flexing or bending it is possible to perform variable impedance mapping over a large uneven surface. By selectively controlling which sensor in the array is measured it is possible to improve resolution of the measured variable.

The disclosed deformable sensing layer also can be used to improve multitouch 25 sensing.

Each switch may be individually controllable to change its state. Each switch may be controllable as part of a subset of switches to change their states collectively. Each switch along a row may be controlled together as a subset of switches.

By controlling the states of switches either individually or collectively it is possible to control the route of the excitation signal. Collectively controlling the states of the switches along a row simplifies the arrangement.

The switches may be deformable switches. The switches may be transistors. The switches may be deformable transistors. The transistors may be thin film transistors or MOSFET transistors. The switches may be electrically controllable switches. The switches may be controllable automatically, for example they may be controllable so as to scan in a pattern.

The measurement frequency of the sensor array may be at least 1 kHz. That is to say a complete scan of the sensor array happens at a frequency of 1kHz. Other measurement frequencies are possible.

Each row may also include a conductive line providing an input or output for the excitation signal. Each column may also include a conductive line providing an output or input for the excitation signal. The conductive lines providing the input and output may be disposed around a portion of the periphery of the array of sensors.

Additional conductive lines may be provided to control the switches.

The deformable substrate may be a deformable laminate structure. The deformable laminate structure may include a first sheet or lamina and a second sheet or lamina.

The variable impedance sensors may be disposed between the first sheet or laminate and the second sheet or laminate.

The first electrodes of the variable impedance sensors may be disposed on or in the first sheet or laminate. The second electrodes of the variable impedance sensors may be disposed on or in the second sheet or laminate.

An intermediary sheet or laminate or microstructure may be disposed between the first and second sheets or laminates. The microstructure may be a plurality of pillars.

The first sheet or laminate may be spaced from the second sheet or laminate. Alternatively, the first sheet or laminate may be substantially in contact with the second sheet or laminate.

The thickness of the deformable substrate, or the deformable sensing layer, may be in the range of 0.1mm to 1.5mm, preferably 0.25mm to 1mm.

The deformable substrate may be an elastomeric material. The substrate may be at least one of lightweight, flexible, stretchable, inert, non-toxic and non-flammable.

The deformable substrate may be a material which is flexible and/or stretchable when exposed to temperatures within the range of at least -70C to 200C.

The variable impedance sensors may be deformable sensors. The variable impedance sensors may be capacitive sensors.

The variable impedance sensors may be resistive sensors.

Each sensor in the array of variable impedance sensors may be sensitive to either temperature, pressure or strain.

The variable impedance sensors may comprise a mixture of electrically conductive and non-conductive particles. The electrical properties of the sensors, namely the nominal resistance and sensitivity of the sensor, may be defined by the concentrations of the conductive and non-conductive particles At least two deformable sensing layers may be arranged in a stack. Each layer in the stack may either sense the same physical phenomenon or a different physical phenomenon or a mix. For example, a first layer may be sensitive to pressure, a second layer may be sensitive to temperature and a third layer may be sensitive to strain.

VVhen arranged in a stack, various components of the sensors and conductive lines may share the same deformable substrate. For example, when there are two layers stacked together, a laminate structure of three laminates may be provided. The middle laminate may have the second electrodes of one array of sensors and the conductive lines connecting said second electrodes on one side while the first electrodes of another array of sensors as well as the switches, conductive lines and conductive traces are on the other side.

Each sensor in the array of sensors on one layer may be substantially aligned with a sensor in the array of sensors in another layer. That is to say that each array of sensors in the stack are aligned so that they overlap or sit on the same axis.

By providing a stacked arrangement it is possible to measure multiple environmental characteristics in the same location. Taking aerodynamic applications as an example, a stacked layers means it is possible to measure multiple environmental characteristics within the area of the layers, such as pressure over the layers, temperature and strain on the surface the layers are attached.

A stacked arrangement where the arrays of sensors measures the same environmental condition can improve the resolution.

The conductive lines may be conductive ink. The electrodes may be conductive ink. The conductive lines and/or electrodes may be carbon fibre nanotubes. The conductive lines may be any suitable material which has the substantially the same electrical properties when stretched or deformed.

According to a second aspect of the present invention there is provided a method of controlling which sensor(s) in an array of sensors is measured. The method comprises the steps of providing at least one deformable sensing layer having an array of variable impedance sensors disposed on or in a deformable substrate in a grid-like pattern with rows and columns, each variable impedance sensor having a first electrode connected by a conductive line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode connected by a conductive line to the second electrode of at least one variable impedance senor in the same column, and selectively measuring at least one sensor in the array of variable impedance sensors by controlling the state of the switches and which rows and columns receive an excitation signal.

VVhen there are stacked sensing layers, each layer may be measured independently.

When there are stacked sensing layers, each layer may be measured collectively. That is to say that measurements may be taken from sensors in each layer which correspond.

According to a third aspect of the present invention there is provided a method of collecting data related to fluid flow over an object. The method comprises the steps of providing at least one deformable sensing layer having an array of variable impedance sensors disposed on or in a deformable substrate in a grid-like pattern with rows and columns, each variable impedance sensor having a first electrode connected by a conductive line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode connected by a conductive line to the second electrode of at least one variable impedance senor in the same column, attaching the deformable sensing layer to an area of an object, subjecting the object to a fluid flow, selecting at least one sensor in the array of variable impedance sensors to measure by controlling the state of the switches and which column and row receives an excitation signal, and recording, from the deformable sensing layer, data indicative of at least pressure over the surface of the deformable sensing layer proximate the selected sensor(s).

When there are stacked sensing layers, each layer may be measured independently.

Wien there are stacked sensing layers, each layer may be measured collectively. That is to say that measurements may be taken from sensors in each layer which correspond.

The sensing layer of the second or third aspects of the invention may be the sensing layer of the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which: Figure 1 shows an exploded schematic view of a deformable sensing layer according to an embodiment of the present invention; Figure 2 shows an exploded perspective view of the deformable sensing layer according to Figure 1; Figure 3 shows schematic view of the deformable sensing layer in Figure 1 without deformable substrate; Figure 4 shows a schematic view of the deformable sensing layer in Figure 1 where a central sensor receives the excitation signal; Figure 5 shows a schematic view of the deformable sensing layer in Figure 1 where an outer sensor receives the excitation signal; and Figure 6 shows an exploded schematic view of a deforrnable sensing device according to an embodiment the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figures 1 and 2, a deformable sensing layer is generally indicated at 10.

In the current embodiment, nine variable impedance sensors 12 are set out in a grid-like pattern to form a sensor array with three rows and columns, however, there may be any number of sensor sets out in any number of rows and columns.

The array of sensors is disposed on or in a deformable substrate, in the current embodiment this comprises two sheets of deformable material 14a, 14b, such as an elastomeric material. Each sensor has a first electrode 13a disposed on one sheet and a second electrode 13b disposed on the other.

First electrodes 13a of each sensor in a row are electrically connected together through conductor lines 16 and switches 18. The first electrode 13a, conductor lines 16 and switches 18 are disposed on or in the first sheet 14a. A second electrode 13b of each sensor in a column are electrically connected by a conductor lines 17. The second electrode 13b and conductor lines 17 are disposed on the second sheet 14b.

Further conductor lines 20 for the rows and columns are provided at two sides of the deformable layer at the boundary of the sensor array, the conductor lines 20 for the columns are provided on the second sheet 14b and the conductor lines 20 for the rows are provided on the first sheet 14a.

Conductive paths 22 for carrying control signals to the switches 18 are disposed on or in the first sheet 14a. In the current embodiment, all the switches 18 on a row are connected so that they collectively change state, i.e. they all receive the same control signal.

The electrodes 13a, 13b in each sensor 12 may be spaced apart, for example by a dielectric material. This arrangement can provide a capacitive sensing mechanism.

Figures 3, 4 and 5 shows the arrangement of sensors 12, conductor lines 16, 17, 20, switches 18 and conductive paths 22 without the deformable substrate.

A method of selecting which sensor 12 in the array of sensors is measured by controlling the flow of current through the array will now be discussed with reference to Figures 4 and 5.

In Figure 4, a measurement of the central sensor R is desired. To select the central sensor R the state of all the switches 18a on the same row, i.e. the central row, are turned to an ON state by transmitting a DC control signal through conductive paths 22a. In the ON state the switches 18a have a very low electrical resistance. The switches 18b on the remaining rows are in an OFF state in which there is a very high electrical resistance. In other embodiments, the DC control signal can be used to set the switches 18b to the OFF state.

High or low voltages are applied to central row and central column through further conductor lines 20a, 20b. This can be done before or after the state of the switches has been controlled. The excitation signal enters the array through conductor line 20a on the central row and exits through the conductor line 20b on the central column. The path of the signal is represented by i and passes through the central sensor R. Voltage measurements are taken from the conductor lines 20a, 20b. Change in the impedance of the central sensor R will be recorded in a change of voltage measurement. The change in impedance may be a result of pressure changing the geometry between the electrodes. For example, if the sensors in the array of sensors are capacitive sensors, the change in distance between the two electrodes of the central sensor will produce a change in capacitance, which can be measured by passing an AC current and detecting voltage change.

In Figure 5, a measurement of the lower right sensor 12b is desired. In a similar approach discussed in relation to Figure 3, all the switches 18a on the same row, i.e. the bottom row, are turned to an ON state by a control signal through the relevant conductive paths 22a. The switches 18b on the remaining rows are in an OFF state. A voltage is applied either before or after the state of the switches has been controlled to the relevant conductor lines 20a 20b, in the current case the bottom row and the right most column. Voltage measurements are then taken from conductor lines 20a, 20b.

An iterative process may be applied to each row, column and set of switches so that a map of the environmental conditions can be created. This could be automatically controlled in a scan pattern Referring to figure 6, a deformable sensing device is generally indicated at 30.

The deformable sensing device has three deformable sensing layers 10a, 10b, 10c. In the current embodiment each sensor array is designed to measure the same environmental condition, for example pressure. However, in other embodiments each sensor array may be designed to measure a different environmental condition, for example one layer measures strain, one layer measures temperature and one layer measures pressure.

The deformable sensing layers are the same as discussed above, i.e. there is an array of sensors formed in the grid-like pattern. Figure 6 does not show the detail of the sensor or switches in detail as these are shown and discussed above in more detail. However, the grid-like pattern shown in Figure 6 can be considered to be the array of sensors.

Each layer is bonded to at least one other layer in the stack. In some embodiments, the sensors in one array of sensors correspond with sensors in the other two arrays of sensors, for example the central sensor for each array of sensors are aligned along the same axis.

The method of controlling which sensor is selected may be performed in the same way.

Each sensor in each sensor array may be selected individually. In some embodiments, the corresponding sensors in each layer may be selected collectively, for example, each central sensor on each layer may be measured at substantially the same time.

A method of collecting data related to fluid flow over an object will now be briefly discussed.

A deformable sensing layer as shown in the Figures and discussed above, or a sensing device having multiple deformable sensing layer as shown in the Figures and discussed above, is provided. The provided deformable sensing layer or device is attached, preferably by means of an adhesive, to an area of an object, for example a portion of its surface. Once attached, the object is subject to a flow of fluid and data indicative of the pressure, temperature, or strain, is recorded. The sensors in the arrays may be individually measured using the methods discussed above.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims

CLAIMS 2. 3. 4. 5. 6. 7. 8.A deformable sensing layer comprising: an array of variable impedance sensors disposed on or in a deformable substrate in a substantially grid-like pattern having rows and columns, wherein each variable impedance sensor includes a first electrode connected by a conductor line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode which is connected by a conductor line to the second electrode of at least one variable impedance sensor on the same column, wherein each variable impedance sensor in the grid of variable impedance sensors is individually measurable by controlling the state of each switch and which row and column receives an excitation signal.
A deformable sensing layer as claimed in claim 1, in which each switch is either individually controllable to change its state or controllable as part of a subset of switches to change their states collectively.
A deformable sensing layer as claimed in claim 2 or claim 3, in which the switches are deformable switches.
A deformable sensing layer as claimed in any preceding claim, in which the switches are transistors.
A deformable sensing layer as claimed in any preceding claim, in which the deformable substrate is a laminate structure.
A deformable sensing layer as claimed in any preceding claim, in which the thickness of the deformable substrate is in the range of 0.1mm to 1.5mm.
A deformable sensing layer as claimed in any preceding claim, in which the thickness of the deformable substrate is in the range of 0.25mm to 1mm.
A deformable sensing layer as claimed in any of the preceding claims, in which the variable impedance sensors are deformable sensors.
9. A deformable sensing layer as claimed in any of the preceding claims, in which the variable impedance sensors are capacitive sensors.
10. A deformable sensing layer as claimed in any of the preceding claims, in which the variable impedance sensors are resistive sensors.
11. A deformable sensing device comprising at least two deformable sensing layers as claimed in any preceding claim wherein the deformable sensing layers are arranged in a stack.
12. A deformable sensing device as claimed in claim 12, in which each deformable sensing layer either senses the same physical phenomenon or a different physical phenomenon.
13. A method of controlling which sensor(s) in an array of sensors is measured, the method comprising the steps of: providing at least one deformable sensing layer having an array of variable impedance sensors disposed on or in a deformable substrate in a grid-like pattern with rows and columns, each variable impedance sensor having a first electrode connected by a conductive line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode connected by a conductive line to the second electrode of at least one variable impedance senor in the same column; and selectively measuring at least one sensor in the array of variable impedance sensors by controlling the state of the switches and which rows and columns receive an excitation signal.
14. A method as claimed in claim 14, in which each switch is either individually controllable to change its state or controllable as part of a subset of switches to change their states collectively.
15. A method as claimed in any of claims 14 or claim 15, in which at least two deformable sensing layers are provided and arranged in a stack.
16. A method as claimed in claim 15, in which each deformable sensing layer is measured independently.
17. A method as claimed in claim 15, in which each deformable sensing layer is measured collectively.
18. A method of collecting data related to fluid flow over an object, the method comprising the steps of: providing at least one deformable sensing layer having an array of variable impedance sensors disposed on or in a deformable substrate in a grid-like pattern with rows and columns, each variable impedance sensor having a first electrode connected by a conductive line and a switch to the first electrode of at least one variable impedance sensor on the same row and a second electrode connected by a conductive line to the second electrode of at least one variable impedance senor in the same column; attaching the deformable sensing layer to an area of an object; subjecting the object to a fluid flow; selecting at least one sensor in the array of variable impedance sensors to measure by controlling the state of the switches and which column and row receives an excitation signal; and recording, from the deformable sensing layer, data indicative of at least pressure over the surface of the deformable sensing layer proximate the selected sensor(s).
19. A method as claimed in claim 20, in which at least two deformable sensing layers are provided and arranged in a stack.
20. A method as claimed in claim 21, in which each deformable sensing layer in the stack is measured independently.
21. A method as claimed din claim 21, in which each deformable sensing layer in the stack is measured collectively