CN111551291B - Method for manufacturing liquid metal film electrode and flexible pressure sensor - Google Patents
Method for manufacturing liquid metal film electrode and flexible pressure sensor Download PDFInfo
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- CN111551291B CN111551291B CN202010449419.0A CN202010449419A CN111551291B CN 111551291 B CN111551291 B CN 111551291B CN 202010449419 A CN202010449419 A CN 202010449419A CN 111551291 B CN111551291 B CN 111551291B
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- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
- G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
Abstract
The invention relates to a manufacturing method of a liquid metal film electrode and a flexible pressure sensor, comprising the following steps: mixing the two components of the elastomer dielectric layer according to a ratio, stirring and removing bubbles, then dropwise adding the mixture on a first carrier treated by a surfactant, and carrying out spin coating treatment; heating the first carrier, and adhering a conductive adhesive tape when the elastomer dielectric layer is not completely cured; spraying liquid metal on the elastomer dielectric layer to form a liquid metal electrode, wherein the liquid metal electrode is connected with the conductive adhesive tape; adding a shaping body on the elastomer dielectric layer with the liquid metal electrode to form a first liquid metal elastomer composite electrode, and separating the first liquid metal elastomer composite electrode from the first carrier after curing. The invention has high sensitivity and is not easy to be interfered by external environment.
Description
Technical Field
The invention relates to the technical field of flexible pressure sensors, in particular to a manufacturing method of a liquid metal film electrode and a flexible pressure sensor.
Background
The flexible pressure sensor can be classified into a capacitive type, a resistive type, a piezoelectric type, and the like according to the working principle. The capacitance type pressure sensor has the advantages of low detection limit, high sensitivity, low energy consumption, low heating degree, compact structure and the like. The capacitive pressure sensor consists of a flexible electrode and a capacitance medium, and response of an output signal is realized according to the change of the facing area of the electrode, the spacing distance and the capacitance medium under the action of an external force. The preparation scheme of the flexible electrode can be roughly divided into two types: one is to dope conductive fillers such as graphene, Carbon Nanotubes (CNTs), metal nanoparticles or nanowires into elastic polymer matrices such as Polydimethylsiloxane (PDMS), styrene-ethylene-butylene-styrene block copolymer (SEBS), Polyurethane (PU), etc.; another option is to use conductive materials that are themselves stretchable, such as ionic liquids, ionic gels, liquid metals, etc.
In the two preparation schemes of the flexible electrode, the method for doping the conductive filler into the elastomer polymer can increase the overall Young modulus of the material, reduce the mechanical strength and the stretchability, and easily cause the resistance to be increased rapidly in the deformation process, even cause irreversible damage; and when materials such as liquid metal are used as the flexible electrode, the fluidity of the flexible electrode increases the difficulty of three-dimensional structure modification and packaging.
In addition, in the existing flexible pressure sensors, "flexibility" is often limited to being able to bend freely and stretch slightly. Although many stretchable materials are currently used for developing strain sensors, that is, the degree of stretching of the sensor is fed back by using an electrical signal generated by stretching deformation of the material, the variable of stretching is an interference factor affecting the accuracy of pressure detection for most pressure sensors, and therefore, the stretchability of the pressure sensor is not sufficiently studied, and how to improve the flexibility and stretchability of the sensor on the basis of ensuring the pressure sensitivity is still a problem worthy of study.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the problems of poor stretchability, easy tensile interference of pressure signals, etc. of the pressure sensor in the prior art, thereby providing a method for manufacturing a high-sensitivity stretchable liquid metal thin film electrode and a flexible pressure sensor.
In order to solve the above technical problem, a method for manufacturing a liquid metal thin film electrode according to the present invention includes: mixing the two components of the elastomer dielectric layer according to a ratio, stirring and removing bubbles, then dropwise adding the mixture on a first carrier treated by a surfactant, and carrying out spin coating treatment; heating the first carrier, and adhering a conductive adhesive tape when the elastomer dielectric layer is not completely cured; spraying liquid metal on the elastomer dielectric layer to form a liquid metal electrode, wherein the liquid metal electrode is connected with the conductive adhesive tape; adding a shaping body on the elastomer dielectric layer with the liquid metal electrode to form a first liquid metal elastomer composite electrode, and separating the first liquid metal elastomer composite electrode from the first carrier after curing.
In one embodiment of the invention, the material used for the elastomeric dielectric layer and the sizing body is silicone rubber.
The invention also provides a preparation method of the liquid metal film electrode, which comprises the following steps after the steps of the preparation method of the liquid metal film electrode are completed: placing a first liquid metal elastomer composite electrode on a second carrier with an elastomer dielectric layer in the first liquid metal elastomer composite electrode facing the second carrier and aligning the stripes with liquid metal electrodes with the pores of the second carrier; placing the second carrier and the first liquid metal elastomer composite electrode in a vacuum environment, firstly applying negative pressure, and then pressurizing to enable the first liquid metal elastomer composite electrode to be sunken into the micropores; and adding a shaping body into the recess to form a second liquid metal elastomer composite electrode, and separating the second liquid metal elastomer composite electrode from the second carrier after curing.
In one embodiment of the invention, the degree of the depression of the first liquid metal elastomer composite electrode into the micropores is adjusted by changing the magnitude of the negative pressure.
The invention also provides a flexible pressure sensor which comprises a first liquid metal elastomer composite electrode and a second liquid metal elastomer composite electrode, wherein the first liquid metal elastomer composite electrode is of a planar structure, the second liquid metal elastomer composite electrode is of an arched structure, and the second liquid metal elastomer composite electrode is positioned above the first liquid metal elastomer composite electrode.
In one embodiment of the present invention, the liquid metal stripes of the first liquid metal elastomer composite electrode and the liquid metal stripes of the second liquid metal elastomer composite electrode are perpendicular to each other, and the arch-shaped protrusions of the second liquid metal elastomer composite electrode and the liquid metal stripes of the first liquid metal elastomer composite electrode are aligned with each other.
The invention also provides a flexible pressure sensor which comprises the flexible pressure sensor, wherein a plurality of first liquid metal elastomer composite electrodes are arranged in an array manner, and a plurality of second liquid metal elastomer composite electrodes are also arranged in an array manner.
The invention also provides a flexible pressure sensor which comprises two second liquid metal elastomer composite electrodes, wherein one of the two second liquid metal elastomer composite electrodes is used as a bottom electrode, the other one of the two second liquid metal elastomer composite electrodes is used as a top electrode, and the second liquid metal elastomer composite electrodes are of an arch structure.
The invention also provides a flexible pressure sensor which comprises the flexible pressure sensor, wherein a plurality of second liquid metal elastomer composite electrodes serving as bottom electrodes are arranged in an array manner, and a plurality of second liquid metal elastomer composite electrodes serving as top electrodes are also arranged in an array manner.
The invention also provides a flexible pressure sensor which comprises any one of the array-type flexible pressure sensors and is used as a basic unit for assembling the flexible pressure sensor in multiple layers.
Compared with the prior art, the technical scheme of the invention has the following advantages:
the invention relates to a manufacturing method of a liquid metal film electrode and a flexible pressure sensor, which comprises a liquid metal film with an arch structure, an Ecoflex film for uniformly encapsulating liquid metal, and an Ecoflex substrate used as a structural support, wherein the maintenance of the arch structure shape can be realized by Ecoflex filling. In addition, the size of the space of the basic unit, the thickness of the liquid metal film and the thickness of the Ecoflex film can be regulated and controlled. And through experiments, the following results can be obtained: the pressure sensor can withstand 94% tensile strain without significant damage; the response of the pressure sensor to pressure under 45% tensile strain is almost the same as that in a normal state, namely the pressure sensor is not easily interfered by tension to a pressure measurement signal; immunity temperature and humidity.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which
FIG. 1 is a flow chart of a first method of manufacturing a liquid metal elastomer composite electrode according to the present invention;
FIG. 2 is a specific process for preparing a first liquid metal elastomer composite electrode according to the present invention;
FIG. 3 is a flow chart of a method of making a second liquid metal elastomer composite electrode according to the present invention;
FIG. 4 is a specific process for preparing a second liquid metal elastomer composite electrode according to the present invention;
FIG. 5a is a schematic diagram of the present invention in a state where the pressure sensor is not exposed to the external pressure;
FIG. 5b is a schematic diagram of the present invention in a state where the pressure sensor is exposed to an external pressure;
FIG. 6 is a graph of incremental changes in capacitance as a pressure sensor of the present invention is subjected to varying pressures;
FIG. 7 is a schematic representation of the mechanical and electrical response of the elements of the pressure sensor array of the present invention;
FIG. 8a is a schematic representation of different states of the pressure sensor array of the present invention;
FIG. 8b is a schematic view of the top dome electrode of the present invention in a stretched state when the strain is different;
FIG. 8c is a graph of the mechanical and electrical properties of the pressure sensor of the present invention in normal and extended states;
FIG. 8d is a schematic diagram illustrating the variation of the coefficient of variation of the initial capacitance value after multiple stretching of the pressure sensor of the present invention;
FIG. 9 is a schematic diagram of an application of the pressure sensor array of the present invention to measure two-dimensional pressure distribution;
fig. 10 is a schematic view of the pressure change of the pressure sensor of the present invention applied to the neck.
The specification reference numbers indicate: 10-elastomer dielectric layer, 20-first carrier, 30-conductive adhesive tape, 40-liquid metal electrode, 50-second carrier, 51-micropore, 61-first liquid metal elastomer composite electrode, 62-second liquid metal elastomer composite electrode.
Detailed Description
Example one
As shown in fig. 1 and 2 and fig. 5a and 5b, the present embodiment provides a method for manufacturing a liquid metal thin film electrode, including the steps of: step S1, mixing the two components of the elastomer dielectric layer 10 according to a proportion, dropping the mixture on the first carrier 20 treated by the surfactant after stirring and removing bubbles, and carrying out spin coating treatment; step S2: heating the first carrier 20, and adhering a conductive adhesive tape 30 when the elastomer dielectric layer is not completely cured; step S3: spraying liquid metal on the elastomer dielectric layer 10 to form a liquid metal electrode 40, wherein the liquid metal electrode 40 is connected with the conductive tape 30; step S4: adding a shaping body on the elastomer dielectric layer 10 with the liquid metal electrode 40 to form a first liquid metal elastomer composite electrode 61, and after curing, separating the first liquid metal elastomer composite electrode 61 from the first carrier 20.
In the method for manufacturing a liquid metal thin film electrode according to this embodiment, in step S1, two components of the elastomer dielectric layer 10 are mixed according to a certain ratio, and after stirring and removing bubbles, the mixture is dropped on the first carrier 20 treated by the surfactant, so as to facilitate film uncovering and prevent tearing, and spin-coating is performed to make spin-coating more uniform; in step S2, the first carrier 20 is heated, and the conductive tape 30 is adhered when the elastomer dielectric layer is not completely cured, so as to connect the external lead with the liquid metal after the flexible sensor package is completed; in the step S3, a liquid metal is sprayed on the elastomer dielectric layer 10 to form a liquid metal electrode 40, and the liquid metal electrode 40 is connected to the conductive tape 30 to facilitate signal transmission; in step S4, a shaping body is added on the elastomer dielectric layer 10 with the liquid metal electrode 40, which is beneficial to supporting and encapsulating the liquid metal to form a first liquid metal elastomer composite electrode 61, and after curing, the first liquid metal elastomer composite electrode 61 is separated from the first carrier 20, so as to form a group of planar electrodes without a special three-dimensional structure, which can be used as bottom electrodes of a flexible sensor.
In this embodiment, the material used for the elastomer dielectric layer and the shaping body is silicone rubber. Specifically, the materials used for the elastomer dielectric layer and the shaping body comprise an Ecoflex elastomer material, a PDMS elastomer material, or other rubber materials, and combinations of the three materials; the first carrier 20 may be a silicon wafer. The liquid metal includes gallium indium alloy (EGaIn) and gallium indium tin alloy (Galinstan).
Specifically, A, B components of Ecoflex 0030 were mixed at a ratio of 1:1 (where they may be mixed at a mass ratio or a volume ratio), sufficiently stirred and vacuumed, dropped in the center of the surfactant-treated silicon wafer, spin-coated at 500rpm for 10s using a spin coater for spin coating at 1000rpm for 1 min.
And (3) placing the silicon wafer on a heating plate at 50 ℃, and adhering a copper-nickel conductive cloth adhesive tape when the silicon wafer is not completely cured so as to realize the connection between an external lead and liquid metal after the flexible sensor is packaged.
A small amount of liquid metal is dripped into the spray pen, the air pump is connected, the air pressure is set to be 40psi, and the liquid metal is sprayed on the Ecoflex film through the customized stainless steel mask plate by using compressed air to form a liquid metal electrode 40. The spraying time can be 5s, and the distance between the nozzle and the mask plate is kept to be 20 cm; 3g of Ecoflex prepolymer is dripped on the Ecoflex film with the liquid metal electrode 40 pattern, the Ecoflex prepolymer is uniformly spread by spin coating at a low rotating speed, and the Ecoflex prepolymer is heated at 60 ℃ for 10min to be solidified. Wherein the Ecoflex of this layer serves to support the entire structure and encapsulate the liquid metal.
Before the first liquid metal elastomer composite electrode 61 is separated from the first carrier 20, the method further includes the steps of cleaning and drying the first liquid metal elastomer composite electrode 61. Specifically, the prepared liquid metal elastomer composite electrode is slowly uncovered from a silicon wafer, cleaned by ultrapure water and ethanol, and finally placed into an oven for drying.
Example two
As shown in fig. 3 and fig. 4, this embodiment provides a method for manufacturing a liquid metal thin film electrode, and after the steps of the method for manufacturing a liquid metal thin film electrode according to the first embodiment are completed, the method further includes: step 1: placing a first liquid metal elastomer composite electrode 61 on a second carrier 50 with the elastomer dielectric layer 10 in the first liquid metal elastomer composite electrode 61 facing the second carrier 50 and aligning the stripes with liquid metal electrodes with the pores 51 of the second carrier 50; step 2: placing the second carrier 50 and the first liquid metal elastomer composite electrode 61 in a vacuum environment, applying negative pressure, and then pressurizing to make the first liquid metal elastomer composite electrode 61 recess into the micropores 51; step 3: and adding a shaping body into the recess to form a second liquid metal elastomer composite electrode 62, and separating the second liquid metal elastomer composite electrode 62 from the second carrier after curing.
After the steps of the method for manufacturing a liquid metal thin film electrode according to the first embodiment are completed, the method further includes step1, placing the first liquid metal elastomer composite electrode 61 on the second carrier 50, so that the elastomer dielectric layer 10 in the first liquid metal elastomer composite electrode 61 faces the second carrier 50, and aligning the stripes with the liquid metal electrode with the micropores 51 of the second carrier 50, thereby facilitating deformation of the elastomer dielectric layer 10; in step2, the second carrier 50 and the first liquid metal elastomer composite electrode 61 are placed in a vacuum environment, and a negative pressure is applied and then a pressure is applied, so that the pressure difference causes the first liquid metal elastomer composite electrode 61 to recess into the micro-hole 51; in step3, a shaping body is added into the recess to support and encapsulate the liquid metal, so as to form a second liquid metal elastomer composite electrode 62, and after curing, the second liquid metal elastomer composite electrode 62 is separated from the second carrier 50, so as to form a set of non-planar electrodes with a three-dimensional structure, specifically, arch-shaped electrodes, which can be used as top electrodes of a flexible sensor.
In this embodiment, the second carrier 50 may be a 96-well plate.
The first liquid metal elastomer composite electrode 61 formed in one of the examples was laid flat on a 96-well plate with the Ecoflex dielectric film facing the 96-well plate and the liquid metal electrode stripes aligned with the circular wells of the 96-well plate.
And integrally moving the 96-hole plate and the first liquid metal elastomer composite electrode 61 into a vacuum box, and applying negative pressure of-0.03 MPa. In the specific operation process, an elastomer film and a mould are used for forming a closed cavity, the film structure is changed by utilizing the air pressure difference inside and outside the cavity, and finally, a polymer retaining structure is cast. The three-dimensional structure of the film can be changed by designing different internal structures of the mold. The method described herein has the advantage over casting the polymer directly onto the mold that other flexible materials can be embedded within the polymer, under a thin film of uniform thickness.
And after a set time such as 30 seconds, introducing air into the vacuum box, and instantly increasing the air pressure in the vacuum box to enable the first liquid metal elastomer composite electrode 61 to be adsorbed on the 96-pore plate. And as the external air continuously enters the vacuum box, the air pressure outside the 96-pore plate continuously rises, and the generated pressure difference prompts the composite electrode with excellent elasticity to be sunken into the round micropores of the 96-pore plate. The degree of the first liquid metal elastomer composite electrode 61 sinking into the micropores 51 is adjusted by changing the magnitude of the negative pressure. Such as the degree of concavity, can be adjusted in the experiment by appropriately changing the magnitude of the negative pressure.
And adding an Ecoflex prepolymer into the recess for filling to form a second liquid metal elastomer composite electrode, putting the second liquid metal elastomer composite electrode into a 60 ℃ oven for heating for 10min, and taking the second liquid metal elastomer composite electrode out of the 96-pore plate after the Ecoflex is completely cured.
EXAMPLE III
Referring to fig. 5a and 5b, the present embodiment provides a first flexible pressure sensor, which includes a first liquid metal elastomer composite electrode 61 and a second liquid metal elastomer composite electrode 62, wherein the first liquid metal elastomer composite electrode 61 is a planar structure, the second liquid metal elastomer composite electrode 62 is an arch structure, and the second liquid metal elastomer composite electrode 62 is located above the first liquid metal elastomer composite electrode 61.
The flexible pressure sensor of the embodiment includes a first liquid metal elastomer composite electrode 61 and a second liquid metal elastomer composite electrode 62, wherein the first liquid metal elastomer composite electrode 61 is of a planar structure, the second liquid metal elastomer composite electrode 62 is of an arch structure, and the second liquid metal elastomer composite electrode 62 is located above the first liquid metal elastomer composite electrode 61, that is, the first liquid metal elastomer composite electrode 61 is used as a bottom layer, and the second liquid metal elastomer composite electrode 62 is used as a top layer, so that the flexible pressure sensor is beneficial to bearing more tensile strain and improving the service life; in addition, the pressure sensor has almost the same response to pressure under certain tensile strain as the normal state, is not easily interfered by tension to a pressure measurement signal, has high sensitivity, and avoids the interference of external environments such as temperature and humidity.
The liquid metal stripes of the first liquid metal elastomer composite electrode 61 are perpendicular to the liquid metal stripes of the second liquid metal elastomer composite electrode 62, and the arch-shaped protrusions of the second liquid metal elastomer composite electrode 62 are aligned with the liquid metal stripes of the first liquid metal elastomer composite electrode 61, so that more tensile strain can be borne, and the service life can be prolonged.
Specifically, the bottom electrode is a planar structure, and the top electrode is a liquid metal film with an arch structure. The Ecoflex capacitor media of the two layers of composite electrodes are stacked inwards, so that the liquid metal stripes of the two layers of electrodes are perpendicular to each other, and the arch-shaped bulge on the top layer of electrode is aligned with the center of the stripe of the bottom layer of electrode. In order to fix the relative position of the two layers of composite electrodes, bonding was performed using a very small amount of Ecoflex in the region outside the sensing cell.
As shown in fig. 5a, when the liquid metal in the top electrode is bent along the dome-shaped elastic body, the pressure sensor maintains the minimum contact area and the maximum separation distance between the two electrodes in the initial state of zero external force. When the pressure sensor is acted by external pressure, as shown in fig. 5b, the liquid metal film electrode on the top layer is extruded, the contact area between the electrodes is obviously increased, and the spacing distance is reduced. The pressure sensor can be equivalent to a series circuit of a variable capacitor and a resistor, and the capacitance can be predicted by the classical equation of a parallel plate capacitor:
wherein A represents the facing area of the two electrodes, d represents the distance between the two electrodes, ε0And εrRepresenting the absolute permittivity and the relative permittivity of the capacitive medium, respectively.
Example four
This embodiment provides a second kind of flexible pressure sensor, and the improvement of going on the basis on the fourth embodiment of this embodiment makes whole flexible pressure sensor be array arrangement, specifically, a plurality of first liquid metal elastomer combined electrode 61's quantity is a plurality of, and is array arrangement, the quantity of second liquid metal elastomer combined electrode 62 also is a plurality of, and is array arrangement to the flexible pressure sensor who forms also is array arrangement, is favorable to measuring pressure distribution, improves life.
In addition, the flexible pressure sensors are arranged in an array form, wherein the array can be arranged in parallel or in a vertical way, for example, the flexible pressure sensors can be arranged in pairs (mirror symmetry) and vertically in a grouped way; or can be vertically arranged in series one by one.
EXAMPLE five
The present embodiment provides a third flexible pressure sensor, which has a composition different from that of the first flexible pressure sensor described in the third embodiment, specifically: two second liquid metal elastomer composite electrodes 62 are included, one of which is used as a bottom electrode and the other is used as a top electrode, and the second liquid metal elastomer composite electrodes 62 are in an arch structure.
The third flexible pressure sensor described in this embodiment includes two second liquid metal elastomer composite electrodes 62, one of which is used as a bottom electrode, and the other is used as a top electrode, and the second liquid metal elastomer composite electrode 62 is an arch structure, which is not only beneficial to improving the pressure resistance, but also enhances the anti-interference capability.
In addition, in the top layer electrode and the bottom layer electrode, the bending arc directions of the arch structures used respectively comprise a same direction arrangement and a reverse direction arrangement.
The number of the second liquid metal elastomer composite electrodes as the bottom electrode is multiple and is arranged in an array manner, and the number of the second liquid metal elastomer composite electrodes as the top electrode is multiple and is arranged in an array manner, so that the pressure distribution can be measured, and the service life can be prolonged.
EXAMPLE six
The present embodiment provides a fourth flexible pressure sensor, which is an improvement made on the basis of the fourth and fifth embodiments, specifically: the flexible pressure sensor according to the fourth embodiment or the flexible pressure sensor according to the fifth embodiment is included, and the flexible pressure sensor is assembled in a plurality of layers as a basic unit.
The fourth flexible pressure sensor in this embodiment includes any one of the flexible pressure sensors described in the fourth embodiment or the flexible pressure sensors described in the fifth embodiment, and as a basic unit, the flexible pressure sensors are assembled in multiple layers, which is not only beneficial to improving the pressure resistance, but also enhances the anti-interference capability.
The beneficial effects described above are demonstrated in detail in the following combination tests:
as shown in fig. 6, the incremental capacitance change curve is shown during the time that the pressure sensor is subjected to a pressure from 0 to 25kPa and then returned to 0. Where 50 capacitance output readings were taken for each data point and the mean and standard deviation were calculated. The pressure sensor has a sensitivity of 39% k Pa in the range of 0-1kPa-1Sensitivity of 15% k Pa in the range of 1-6kPa-1Sensitivity of 10% k Pa in the range of 6-25kPa-1At a maximum pressure of 25kPa, the hysteresis error is 8.46%.
As shown in fig. 7, the pressure-capacitance increment curves of all the sensing units are sequentially arranged according to the respective spatial serial numbers, and the consistency of the mechanical-electrical response of each unit in the 4 × 4 sensor array is studied. In the pressure range of 0-25kPa, the capacitance increment of all the curves has the same change trend, and the sensitivity deviation of each unit is only 0.48% k Pa-1。
As shown in FIG. 8a, three photographs show different states of the sensor array (tensile strain: 0, 45%, 94%). Thanks to the fluidity of the liquid metal and the lower young's modulus of the Ecoflex elastomer, no significant cracks appear on both the electrode and the elastomer during stretching. The tensile state of the sensor is analyzed by numerical simulation, and fig. 8b shows the tensile state of the top dome electrode when the strain is 0, 14%, 31% and 45%, and the volume strain distribution of the dome electrode in each state. Each sensing unit comprises an arch-shaped bulge and a surrounding flat membrane, and the part of the pressure sensor which deforms when being subjected to pressure is mainly concentrated at the position of the arch-shaped bulge. This location is protected by the thicker Ecoflex elastomer, and therefore, when the pressure sensor is in a stretched state, the non-uniformity in thickness causes the tensile strain to be mainly dispersed at a location which is not related to the capacitance signal, thereby greatly attenuating the strain caused by the tensile stress to the dome-shaped electrode, and reducing the influence on the capacitance signal. Fig. 8c summarizes the mechanical-electrical performance of the pressure sensor in the normal (0% strain) and tensile (45% strain) states. The same mechanical load is applied to the same sensing unit within the pressure range of 0-4kPa, and due to the unique arch structure of the top electrode of the sensor, the change curves of capacitance increment along with the pressure are not obviously different in two states, so that the result of numerical simulation is verified. This means that the sensor can still output an accurate electrical signal even in the 45% strained stretched state. In addition, the present application also performed repeated stretch-recovery cycles of about 94% strain on the sensor, and measured the capacitance of the sensing cell at the initial length state every 30 cycles. As shown in fig. 8d, the Coefficient of Variation (CV) of these initial capacitance values was less than 1.2% over the course of 180 stretches, indicating that the sensor can withstand repeated high mechanical stretches and still maintain normal function.
As shown in FIG. 9, different types of pressure sources were tested using a 4X 4 sensor array, including a cylindrical weight (20 g mass, 13mm bottom diameter, representing relatively concentrated pressure load) and a circular adhesive tape (16 g mass, 52mm diameter, representing relatively dispersed pressure load). As shown in fig. 9(a-b), the weight and the adhesive tape are sequentially placed at corresponding positions of the same sensor array, the capacitance increment displayed by each sensing unit is recorded, and the pressure intensity born by each sensing unit is calculated. The sensor arrays are numbered as shown in fig. 9 (a). The contact area of the weight and the sensor is small, the bottom of the weight is approximately positioned on the No. 7 sensing unit, and the weight and the adjacent sensing unit are also in small contact. As shown in fig. 9(c), the unit No. 7 is subjected to most of the pressure (relative pressure is 1.41kPa), and the adjacent sensing unit shows a smaller relative pressure: 450Pa (No. 3), 180Pa (No. 8), 100Pa (No. 6), 80Pa (No. 11), and 40Pa (No. 4). In contrast, the pressure generated by the tape when it contacts the sensor is relatively dispersive. As can be seen from FIG. 9(d), the cells at the four corners of the sensor array bear most of the pressure (relative pressure 160-210Pa) due to the largest area in direct contact with the adhesive tape, followed by 8 sensor cells (70-130Pa) on the four sides. The middle 4 sensing units, although not in direct contact with the tape, also show a smaller signal due to interference from ambient pressure. Fig. 9(e-f) are contour plots of the pressure for both cases, showing more clearly the relative position and intensity of the pressure source on the sensor array, and even the underlying topography of the pressure source can be roughly inferred from the contours.
As shown in fig. 10, the present application explores potential applications for recognizing neck gestures by detecting pressure between sensor cells and the neck. The pressure sensor has sufficient elasticity, softness and biocompatibility, can be comfortably fitted to human skin, and can be adapted to most neck postures. This application is laminated pressure sensor array on the neck skin, fixed with the film. There is an initial pressure between the sensor and the skin. As shown in fig. 10(a-b), the pressure between the sensor and the neck in the posture in which the volunteer looks straight ahead is defined as an initial value, and the capacitance value of each sensing unit in this posture is set as an initial capacitance. When the experimenter changes various neck postures, the capacitance increment of each sensing unit is calculated, and the change of the pressure intensity corresponding to each sensing unit is calculated.
The neck position and the corresponding pressure distribution of the experimenter when raising his head are shown in fig. 10 (c-d). The color of the signals measured by all the sensing units in the graph changes, which shows that the pressure detected by all the sensing units in the head-up posture of the volunteer is increased compared with the forward and direct-view posture. As shown in fig. 10(e-f), the sensor array detects a transverse pressure gradient as the experimenter turns the head to the left. Wherein the leftmost column of sensing units detects the highest pressure increase, and the rightmost column of sensing units detects a reduced pressure compared to the direct-view posture, indicating that the pressure is mainly distributed on the side where the experimenter turns.
By analyzing the pressure distribution of the neck region, various neck postures of the user can be deduced, and effective reference is provided for subsequent real-time neck posture recognition. Further, the sensor array can be applied to detect unhealthy neck postures for patients in rehabilitation training or the like, and prompt in time.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (9)
1. The preparation method of the liquid metal film electrode is characterized by comprising the following steps:
step S1, mixing the two components of the elastomer dielectric layer according to a proportion, dripping the mixture on the first carrier treated by the surfactant after stirring and removing bubbles, and carrying out spin coating treatment;
step S2: heating the first carrier, and adhering a conductive adhesive tape when the elastomer dielectric layer is not completely cured;
step S3: spraying liquid metal on the elastomer dielectric layer to form a liquid metal electrode, wherein the liquid metal electrode is connected with the conductive adhesive tape;
step S4: adding a shaping body on an elastomer dielectric layer with a liquid metal electrode to form a first liquid metal elastomer composite electrode, and separating the first liquid metal elastomer composite electrode from the first carrier after curing; further comprising:
step 1: placing a first liquid metal elastomer composite electrode on a second carrier with an elastomer dielectric layer in the first liquid metal elastomer composite electrode facing the second carrier and aligning the stripes with liquid metal electrodes with the pores of the second carrier;
step 2: placing the second carrier and the first liquid metal elastomer composite electrode in a vacuum environment, firstly applying negative pressure, and then pressurizing to enable the first liquid metal elastomer composite electrode to be sunken into the micropores;
step 3: and adding a shaping body into the recess to form a second liquid metal elastomer composite electrode, and separating the second liquid metal elastomer composite electrode from the second carrier after curing.
2. A method for preparing a liquid metal thin film electrode according to claim 1, wherein: the elastomer dielectric layer and the shaping body are made of silicon rubber.
3. A method for preparing a liquid metal thin film electrode according to claim 1, wherein: the degree of the first liquid metal elastomer composite electrode sinking into the micropores is adjusted by changing the size of the negative pressure.
4. A flexible pressure sensor, characterized by: the liquid metal elastomer composite electrode is of a planar structure, the second liquid metal elastomer composite electrode is of an arched structure and is positioned above the first liquid metal elastomer composite electrode, the first liquid metal elastomer composite electrode is placed on a second carrier, an elastomer dielectric layer in the first liquid metal elastomer composite electrode faces the second carrier, and the stripes with the liquid metal electrodes are aligned with micropores of the second carrier; placing the second carrier and the first liquid metal elastomer composite electrode in a vacuum environment, firstly applying negative pressure, and then pressurizing to enable the first liquid metal elastomer composite electrode to be sunken into the micropores; and adding a shaping body into the recess to form a second liquid metal elastomer composite electrode, and separating the second liquid metal elastomer composite electrode from the second carrier after curing.
5. The flexible pressure sensor of claim 4, wherein: the liquid metal stripes of the first liquid metal elastomer composite electrode are perpendicular to the liquid metal stripes of the second liquid metal elastomer composite electrode, and the arch-shaped protrusions of the second liquid metal elastomer composite electrode are aligned with the liquid metal stripes of the first liquid metal elastomer composite electrode.
6. A flexible pressure sensor, characterized by: the flexible pressure sensor of any one of claims 4-5, wherein the first plurality of liquid metal elastomer composite electrodes are arranged in an array, and the second plurality of liquid metal elastomer composite electrodes are arranged in an array.
7. A flexible pressure sensor, characterized by: the device comprises two second liquid metal elastomer composite electrodes, wherein one of the two second liquid metal elastomer composite electrodes is used as a bottom electrode, the other one of the two second liquid metal elastomer composite electrodes is used as a top electrode, the second liquid metal elastomer composite electrode is of an arch structure, the first liquid metal elastomer composite electrode is placed on a second carrier, an elastomer dielectric layer in the first liquid metal elastomer composite electrode faces the second carrier, and stripes with the liquid metal electrodes are aligned with micropores of the second carrier; placing the second carrier and the first liquid metal elastomer composite electrode in a vacuum environment, firstly applying negative pressure, and then pressurizing to enable the first liquid metal elastomer composite electrode to be sunken into the micropores; and adding a shaping body into the recess to form a second liquid metal elastomer composite electrode, and separating the second liquid metal elastomer composite electrode from the second carrier after curing.
8. A flexible pressure sensor, characterized by: the flexible pressure sensor of claim 7, wherein the number of the second liquid metal elastomer composite electrodes as the bottom electrode is plural and arranged in an array, and the number of the second liquid metal elastomer composite electrodes as the top electrode is plural and arranged in an array.
9. A flexible pressure sensor, characterized by: the flexible pressure sensor according to claim 6 or the flexible pressure sensor according to claim 8 is included as a base unit, and the flexible pressure sensor is assembled in multiple layers.
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| PCT/CN2020/123605 WO2021238042A1 (en) | 2020-05-25 | 2020-10-26 | Method for manufacturing liquid metal thin-film electrode, and flexible pressure sensor |
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| CN111551291B (en) * | 2020-05-25 | 2022-04-05 | 苏州大学 | Method for manufacturing liquid metal film electrode and flexible pressure sensor |
| CN114486009A (en) * | 2020-11-11 | 2022-05-13 | 北京梦之墨科技有限公司 | Piezoresistive flexible sensor and manufacturing method thereof |
| CN113074840B (en) * | 2021-03-30 | 2023-03-24 | 西交利物浦大学 | Active pressure sensor and preparation method thereof |
| CN113387322A (en) * | 2021-04-30 | 2021-09-14 | 中国科学院理化技术研究所 | Preparation method and application of uniform micro-nano film of liquid metal |
| CN113525494B (en) * | 2021-07-05 | 2022-11-25 | 吉林大学 | Intelligent automobile steering wheel device with multi-mode tactile perception |
| CN113556054B (en) * | 2021-08-11 | 2022-12-23 | 浙江大学杭州国际科创中心 | Self-driven, channel-free and expandable sensor based on liquid metal and solid-liquid friction interface and preparation method thereof |
| CN114149686B (en) * | 2021-12-08 | 2023-01-13 | 北京航空航天大学 | Dielectric elastomer-based microstructure surface liquid transport direction control valve and preparation method thereof |
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