CN113155327B

CN113155327B - Bionic microarray flexible electrode, preparation method thereof and flexible pressure sensor

Info

Publication number: CN113155327B
Application number: CN202110339836.4A
Authority: CN
Inventors: 李晖; 陈静; 李林; 王磊
Original assignee: Shenzhen Institute of Advanced Technology of CAS
Current assignee: Shenzhen Institute of Advanced Technology of CAS
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2023-02-10
Anticipated expiration: 2041-03-30
Also published as: CN113155327A

Abstract

The invention provides a bionic microarray flexible electrode, a preparation method thereof and a flexible pressure sensor, wherein the preparation method of the flexible electrode comprises the following steps: providing plant leaves; mixing the PDMS prepolymer with a curing agent to obtain a PDMS mixture; pouring the PDMS mixture on plant leaves, and taking out the cured PDMS to obtain a mold; attaching the mold to a template, and starting vacuum adsorption; and preparing AgNWs dispersion liquid, spraying the AgNWs dispersion liquid onto a mould, and annealing. According to the preparation method of the flexible electrode, the plant leaves with the specific micron-sized conical array structure on the surface are used as the template, the mold is prepared, and meanwhile, the millimeter-sized semicircular convex array formed by vacuum adsorption is combined to form the three-dimensional array structure with different sizes from micron to millimeter, so that the microarray flexible electrode with the structure has good response characteristics to different magnitudes of pressure, and the measurement range is greatly widened.

Description

Bionic microarray flexible electrode, preparation method thereof and flexible pressure sensor

Technical Field

The invention relates to the technical field of flexible wearable healthy electronic equipment, in particular to a bionic microarray flexible electrode, a preparation method thereof and a flexible pressure sensor.

Background

In recent years, the rapid development of the 5G communication technology greatly promotes the cross integration of the internet of things and the intelligent terminal, and the flexible pressure sensor serving as one of the core components plays more and more important roles in medical health, motion detection and correction and the like. The flexible pressure sensor has the characteristics of good conformability, light weight, portability and the like. The medical wearable device based on the flexible pressure sensor can be integrated into clothes, accessories or directly pasted on the surface of skin, and the physiological information of the human body is dynamically collected and used for feedback judgment of the health condition of the human body. The flexible pressure sensor can be attached to the surface of an irregular three-dimensional object at will according to a using scene for signal detection, for example, the flexible pressure sensor is attached to the throat for monitoring the vibration of a vocal cord, the sound reproduction of a patient who cannot speak can be realized, and the flexible pressure sensor is attached to the abdomen of a human body for monitoring the breathing intensity and frequency of the human body.

The flexible pressure sensor with excellent electrical performance mainly comprises a high-performance flexible substrate electrode and a sensitive material, and is realized by combining a special structure. At present, the flexible pressure sensor is mostly prepared by a method with complex processes such as silicon chip etching, vapor deposition, high-resolution 3D printing and the like, expensive equipment and high energy consumption, and the development and the application of the flexible pressure sensor in real life are limited by the high manufacturing cost of the flexible pressure sensor; on the other hand, most of the flexible pressure sensors have low sensitivity and narrow measurement range, and cannot actively identify weak physiological signals, so that the defects seriously restrict the comprehensive analysis and detection of the flexible pressure sensors on various complex physiological signals.

Based on the technical problems of the present flexible pressure sensor, there is a need for improvement.

Disclosure of Invention

In view of the above, the invention provides a bionic microarray flexible electrode, a preparation method thereof and a flexible pressure sensor, so as to solve or partially solve the technical problems in the prior art.

In a first aspect, the invention provides a preparation method of a bionic microarray flexible electrode, which comprises the following steps:

providing a plant leaf with leaf surface texture;

mixing the PDMS prepolymer with a curing agent to obtain a PDMS mixture for later use;

pouring the PDMS mixture on the plant leaf, curing the PDMS, and taking the cured PDMS out of the plant leaf to obtain a mold with the surface opposite to the surface of the plant leaf;

attaching the surface of the mold opposite to the surface of the plant leaf to a template provided with a plurality of through holes, placing the template in a vacuum adsorption device, starting vacuum adsorption, and separating the mold from the template;

and preparing AgNWs dispersion liquid, spraying the AgNWs dispersion liquid on a mold subjected to vacuum adsorption, and annealing to obtain the bionic microarray flexible electrode.

On the basis of the above technical solution, preferably, the method for preparing the bionic microarray flexible electrode further comprises, before attaching the surface of the mold opposite to the surface of the plant leaf to a template provided with a plurality of through holes: dripping the PDMS mixture into the surface of the mold opposite to the surface of the plant leaf, performing spin coating and curing, and taking the cured PDMS out of the mold to obtain a PDMS film with a micro-cone surface; then attaching the surface of the PDMS film in the shape of a micro cone to a template provided with a plurality of through holes, and separating the PDMS film from the template through vacuum adsorption; and spraying the AgNWs dispersion liquid onto the PDMS film subjected to vacuum adsorption, and annealing to obtain the bionic microarray flexible electrode.

Further preferably, the preparation method of the bionic microarray flexible electrode further comprises the following steps of before spraying the AgNWs dispersion liquid on the PDMS film subjected to vacuum adsorption: dripping the PDMS mixture into the surface of the PDMS film far away from the micro-cone, performing spin coating, curing the PDMS, and separating the cured PDMS film from the template; and spraying the AgNWs dispersion liquid onto the cured PDMS film, and annealing to obtain the bionic microarray flexible electrode.

Further preferably, the method for preparing the bionic microarray flexible electrode further comprises before dropping the PDMS mixture on the surface of the mold opposite to the surface of the plant leaf: and putting the mould into an alcohol solution for passivation.

Further preferably, in the preparation method of the bionic microarray flexible electrode, the PDMS mixture is dropped on the surface of the mold opposite to the surface of the plant leaf, and then spin-coating and curing are performed, wherein the spin-coating specifically comprises: spin-coating at 300-500 r/min for 10-20s; the curing is specifically as follows: curing at 80-100 deg.c for 20-40 min.

Preferably, the preparation method of the bionic microarray flexible electrode comprises the steps of dropping the PDMS mixture on the surface of the side, far away from the side of the micro-cone, of the PDMS film, performing spin coating, and curing the PDMS, wherein the spin coating specifically comprises the following steps: spin-coating at 300-500 r/min for 8-12 s; the curing is specifically as follows: firstly heating and curing for 10-20 min under an infrared lamp, and then heating for 40-60min in an oven at 80-100 ℃.

On the basis of the technical scheme, preferably, the preparation method of the bionic microarray flexible electrode comprises the following steps: adding AgNWs into absolute ethyl alcohol, and performing ultrasonic dispersion to obtain AgNWs dispersion liquid;

and/or the annealing treatment specifically comprises the following steps: annealing in a baking oven at 80-100 ℃ for 40-60 min.

In a second aspect, the invention also provides a bionic microarray flexible electrode prepared by the preparation method.

In a third aspect, the present invention also provides a flexible pressure sensor comprising:

a pair of said biomimetic microarray flexible electrodes;

and the ionic gel dielectric layer is positioned between the pair of bionic microarray flexible electrodes.

On the basis of the above technical solution, preferably, the method for preparing the ionic gel dielectric layer of the flexible pressure sensor comprises the following steps:

adding PVDF-HFP into acetone, stirring uniformly, adding ionic liquid, and continuously stirring to obtain a mixed solution;

and coating the mixed solution on a substrate, annealing, and stripping to obtain the ionic gel dielectric layer.

Compared with the prior art, the bionic microarray flexible electrode and the flexible pressure sensor have the following beneficial effects:

(1) According to the preparation method of the bionic microarray flexible electrode, the plant leaves with the specific micron-sized conical array structure on the surface are used as the template, the mold is prepared, meanwhile, the millimeter-sized semicircular bulge array formed by vacuum adsorption is combined, the three-dimensional array structure with different sizes from micron to millimeter is formed, the microarray flexible electrode with the structure enables a sensor to have good response characteristics to pressure with different magnitudes, and the measurement range is greatly widened;

(2) The flexible pressure sensor disclosed by the invention has the advantages that the response to the pressure is completed by the combined action of the flexible electrode change of the microarray structures with different sizes and the interface capacitance change of the ion gel layer, and the pressure sensor has more obvious capacitance change when facing the external pressure compared with a common capacitive flexible sensor due to the ultrahigh specific capacitance of the ion gel layer, so that the sensor has extremely high sensitivity and responsiveness; meanwhile, the pressure sensor is simple in structure, easy in manufacturing steps, and capable of greatly reducing manufacturing cost and processing difficulty.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a schematic diagram of a method for preparing a bionic microarray flexible electrode according to the present invention, in which a PDMS mixture is poured on the surface of a velvet arrowroot blade in one embodiment;

FIG. 2 is a schematic diagram of a method for fabricating a bionic microarray flexible electrode according to the present invention, in which a PDMS mixture is continuously spin-coated on a surface of a formed mold in one embodiment;

FIG. 3 is a schematic diagram of a method for fabricating a bionic microarray flexible electrode according to the present invention, in which a PDMS film is adhered to a template having a plurality of through holes;

FIG. 4 is a schematic structural diagram of a bionic microarray flexible electrode according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a flexible pressure sensor according to the present invention;

FIG. 6 is a schematic illustration of a flexible pressure sensor of the present invention in which an ionic gel dielectric layer is fabricated on a substrate in one embodiment;

FIG. 7 is a surface topography map of a biomimetic microarray flexible electrode fabricated in example 1 of the present invention;

FIG. 8 is a graph of the sensitivity and response of the assembled flexible pressure sensor of example 1 of the present invention;

FIG. 9 is a graph showing the pulse rate of the human body detected by the flexible pressure sensor assembled in embodiment 1 of the present invention;

fig. 10 is a graph showing a detection curve of the sole pressure of the human body of the flexible pressure sensor assembled in embodiment 1 of the present invention.

Detailed Description

In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments of the present invention, belong to the protection scope of the present invention.

The invention provides a preparation method of a bionic microarray flexible electrode, which comprises the following steps:

s1, providing a plant leaf with leaf surface textures;

s2, mixing the PDMS prepolymer with a curing agent to obtain a PDMS mixture for later use;

s3, pouring the PDMS mixture on the plant leaf, curing the PDMS, and taking the cured PDMS out of the plant leaf to obtain a mold with the surface opposite to the surface of the plant leaf;

s4, attaching the surface of the mold opposite to the surface of the plant leaf to a template provided with a plurality of through holes, placing the template in a vacuum adsorption device, starting vacuum adsorption, and separating the mold from the template;

and S5, preparing AgNWs dispersion liquid, spraying the AgNWs dispersion liquid on a mold subjected to vacuum adsorption, and annealing to obtain the bionic microarray flexible electrode.

In the preparation method of the bionic microarray flexible electrode, the plant leaves with the leaf surface textures mean that the textures of the surfaces of the plant leaves are clear, and the surfaces of the plant leaves form a similar micron-sized micro-convex cone array structure, for example, the plant leaves comprise velvet arrowroot leaves, watermelon peels, pepper grass leaves, eurya angustifolia leaves, zodiac arrowroot leaves and the like; in practice, plant leaves can be fixed on a substrate, and then PDMS mixture is poured, wherein the substrate can be an acrylic plate, and obviously, other plate bodies which can play a role of a carrier can be adopted; the plant leaves can be fixed on the base plate through double-sided adhesive tapes, and for the velvet arrowroot leaves, the front surfaces of the plant leaves are fixed on the base plate; pouring the PDMS mixture on a plant leaf of a substrate, and curing PDMS to obtain a mold, wherein one surface of the mold is provided with an array structure opposite to the micro convex cone array structure on the surface of the plant leaf, namely a micro concave cone structure is formed; attaching the surface of the mold opposite to the surface of the plant leaf to a template provided with a plurality of through holes, namely attaching the surface of the mold with a micro-concave cone structure to the template, wherein the through holes on the template are arranged in an array, the diameters of the through holes can be the same or different, the mold can be adhered to the template by adopting a PET (polyethylene terephthalate) substrate double faced adhesive tape, and after vacuum adsorption, the mold can form a millimeter-grade semicircular concave structure in the area of the corresponding through holes on the surface of the template opposite to the surface of the plant leaf due to the pressure difference between the upper surface and the lower surface; and then spraying the AgNWs (silver nanowire) dispersion liquid on the surface of the mold after vacuum adsorption, wherein the surface is opposite to the surface of the plant leaf, so as to obtain the bionic microarray flexible electrode.

In some embodiments, the casting of the PDMS mixture on the plant leaves further comprises: the plant leaves are placed in deionized water for cleaning for 2-4 min and then are dried by using nitrogen.

In some embodiments, the PDMS prepolymer and the curing agent are mixed to obtain a PDMS mixture, wherein the mass ratio of the PDMS (polydimethylsiloxane) prepolymer to the curing agent is 10 (1-3), the model of the PDMS prepolymer is dow corning 184, and the curing agent is dow corning 184.

In some embodiments, before casting the PDMS mixture on the plant leaves, further comprises: placing the PDMS mixture into a stirrer, stirring and degassing for 3-5 minutes.

In some embodiments, before attaching the surface of the mold opposite to the surface of the plant leaf to the template provided with the plurality of through holes, the method further comprises: dripping the PDMS mixture into the surface of the mould opposite to the surface of the plant leaf, performing spin coating and curing, and taking the cured PDMS out of the mould to obtain a PDMS film with a micro-cone surface; attaching the surface of the PDMS film in the shape of a micro cone to a template provided with a plurality of through holes, and separating the PDMS film from the template through vacuum adsorption; and spraying the AgNWs dispersion liquid onto the PDMS film subjected to vacuum adsorption, and annealing to obtain the bionic microarray flexible electrode. In the embodiment of the application, the PDMS mixture is dripped on the surface of the mold, and the PDMS film is obtained after curing, wherein the surface of the PDMS film is a micro-cone, and specifically, the surface of the PDMS film has a surface micro-convex cone array structure which is the same as that of the plant leaves; during spraying, the AgNWs dispersion is sprayed on the surface of the PDMS film in a micro-cone shape.

In some embodiments, before spraying the AgNWs dispersion on the vacuum-adsorbed PDMS film, the method further comprises: dripping the PDMS mixture into the surface of the PDMS film far away from the side of the micro-cone, performing spin coating, curing the PDMS, and separating the cured PDMS film from the template; and spraying the AgNWs dispersion liquid onto the cured PDMS film, and annealing to obtain the bionic microarray flexible electrode. In the embodiment of the application, the PDMS mixture is dripped into the surface of the PDMS film again, agNWs dispersion liquid is sprayed, and the bionic microarray flexible electrode prepared in the way forms a multi-layer upper and lower polar plate structure which has good response characteristics to pressures of different magnitudes.

In some embodiments, prior to dropping the PDMS mixture into the surface of the mold opposite the plant leaf surface, further comprises: and (4) putting the mold into an alcohol solution for passivation. The alcoholic solution is an absolute ethyl alcohol solution; specifically, in practice, the mold is firstly placed into a plasma cleaning machine and is treated by oxygen plasma for 2-4 min, then the mold is immersed into absolute ethyl alcohol solution, and is then placed into a vacuum drying oven to be dried for 1-3 h at 70-80 ℃, and the mold is taken out and dried by nitrogen; the mold surface is rendered hydrophobic by passivation, which facilitates the removal of the PDMS film from the mold.

In some embodiments, the PDMS mixture is dropped on the surface of the mold opposite to the surface of the plant leaf, and then is spin-coated and cured, wherein the spin-coating is specifically: spin-coating at 300-500 r/min for 10-20s; the curing method specifically comprises the following steps: curing at 80-100 deg.c for 20-40 min.

In some embodiments, the PDMS mixture is dropped on the surface of the PDMS film away from the micro-cone, and then the PDMS is cured by spin coating, wherein the spin coating specifically comprises: spin-coating at 300-500 r/min for 8-12 s; the curing method specifically comprises the following steps: heating and curing for 10-20 min under an infrared lamp, and then heating for 40-60min in an oven at 80-100 ℃.

In some embodiments, the AgNWs dispersion is prepared by: adding AgNWs into absolute ethyl alcohol, and performing ultrasonic dispersion to obtain AgNWs dispersion liquid;

Specifically, the mass ratio of AgNWs (silver nanowires) to absolute ethyl alcohol is 1 (5-10).

In some embodiments, the AgNWs dispersion is sprayed on the surface of the cured PDMS film until the surface resistance of the PDMS film is 10-30 Ω, and the solvent in the AgNWs dispersion is completely evaporated by annealing in an oven at 80-100 ℃ for 40-60min, thereby forming AgNWs on the surface of the PDMS film and increasing the adhesion between the AgNWs and the PDMS film.

In some embodiments, spraying the AgNWs dispersion onto the PDMS film further comprises: and (3) putting the PDMS film into a plasma cleaning machine, and treating the PDMS film for 3-5 min by using oxygen plasma so as to improve the adhesive capacity of the surface of the PDMS film.

FIGS. 1 to 4 show schematic diagrams of bionic microarray flexible electrodes prepared from velvet arrowroot leaves in one embodiment. Wherein, fig. 1 is a schematic diagram of pouring a PDMS mixture 2 on the surface of a velvet arrowroot blade 1, forming a mold after curing, and forming a micro-convex cone array structure on the surface of the velvet arrowroot blade 1; FIG. 2 is a view showing that PDMS mixture 2 is continuously coated on the surface of the formed mold 3, and after curing, PDMS is taken out of the mold 3 to obtain a PDMS film, which is apparently the opposite structure of the mold 3 and has the same microstructure as the surface of the velvet arrowroot blade 1, i.e. the micro-cone structure mentioned above; fig. 3 is a schematic diagram of a bionic microarray flexible electrode 6 obtained by adhering a PDMS film 4 to a template 5 provided with a plurality of through holes 51, forming a concave shape 41 on the PDMS film 4 at a position corresponding to the through holes 51 after vacuum adsorption, continuing to spin-coat a PDMS mixture 2 on the surface of the PDMS film 4 at the side away from the micro-cone, after the PDMS is cured, spraying an AgNWs dispersion liquid on the surface of the PDMS film 4 having the micro-cone structure, and forming AgNWs61 on the surface of the PDMS film, wherein the structure of the bionic microarray flexible electrode 6 is as shown in fig. 4.

Based on the same inventive concept, the present invention also provides a flexible pressure sensor, as shown in fig. 5, including:

a pair of bionic microarray flexible electrodes 6 prepared by the method;

and the ionic gel dielectric layer 7 is positioned between the pair of bionic microarray flexible electrodes 6.

In some embodiments, the method for assembling the flexible pressure sensor comprises the following steps:

respectively leading out leads at the edges of the two bionic microarray flexible electrodes 6, bonding the leads and the electrodes by using conductive silver paste, and then placing the electrodes in an oven at 80-100 ℃ for curing for 40-60min; and then placing an ionic gel dielectric layer 7 between the two bionic microarray flexible electrodes 6, and sealing the periphery of the bionic microarray flexible electrodes 6 by using a polyimide adhesive tape to complete the assembly of the flexible pressure sensor.

In some embodiments, the method of making the ionic gel dielectric layer 7 comprises the steps of:

adding PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer) into acetone, stirring uniformly, then adding ionic liquid, and continuously stirring to obtain a mixed solution;

In the application, the ionic liquid is EMIM TFSI (1-ethyl-3-methylimidazole bis (trifluoromethanesulfonyl) imide salt), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer) is added into acetone and stirred for 2-4 hours at 50-70 ℃ to melt the PVDF-HFP and uniformly disperse the PVDF-HFP in an acetone solvent; then adding ionic liquid EMIM TFSI and stirring for 1-2 h at room temperature to obtain a mixed solution.

In some embodiments, the substrate is a glass substrate, the mixed solution is spin-coated on the glass substrate at a rotation speed of 300-500 rpm for 40-60 seconds, and then the glass substrate is placed in a vacuum drying oven at a temperature of 40-60 ℃ for annealing for 1-3 hours, so that the solvent in the mixed solution is completely removed, and the ionic gel dielectric layer is obtained after stripping.

Fig. 6 shows a schematic diagram of an ionic gel dielectric layer 7 prepared on a substrate 8.

The preparation method of the bionic microarray flexible electrode comprises the steps of preparing a mold by taking a plant blade with a specific micron-sized conical array structure on the surface as a template, further forming a PDMS film with the same microstructure array as the surface of the plant blade by using the mold, and forming a three-dimensional array structure with different sizes from micron to millimeter by combining a millimeter-sized semicircular convex array formed by vacuum adsorption.

The flexible pressure sensor disclosed by the invention has the advantages that the response to the pressure is completed by the combined action of the flexible electrode changes of the microarray structures with different sizes and the interface capacitance change of the ionic gel layer, and the ionic gel layer has ultrahigh specific capacitance, so that the pressure sensor has more remarkable capacitance change when facing the external pressure than a common capacitive flexible sensor, and the sensor has extremely high sensitivity and responsiveness.

The following further describes the preparation methods of the bionic microarray flexible electrode and the flexible pressure sensor of the present application with specific examples.

Example 1

The embodiment of the application provides a preparation method of a bionic microarray flexible electrode, which comprises the following steps:

a1, washing velvet arrowroot blades with deionized water for 3 minutes and drying the surfaces of the velvet arrowroot blades with nitrogen; then, adhering 3M double-sided adhesive tape on the acrylic plate, and adhering the velvet arrowroot leaves with the right side facing upwards on the acrylic plate;

a2, mixing a PDMS prepolymer poly (dimethyl-methylsilylsiloxane) and a curing agent poly (dimethyl-hydrogensiloxane) according to a mass ratio of 10;

a3, pouring the PDMS mixture in the A2 on an acrylic plate attached with a velvet arrowroot blade, curing for 20 hours in a vacuum environment, and removing the cured PDMS from the velvet arrowroot blade to obtain a mold with one surface having a structure opposite to the micro-convex cone on the surface of the velvet arrowroot blade;

a4, placing the mould obtained in the step A3 in a plasma cleaning machine, treating the mould for 3min by using oxygen plasma, immersing the mould in an ethanol water solution with the mass concentration of 80%, then placing the mould in a vacuum drying oven, drying the mould for 2h at 70 ℃, taking out the mould, and drying the mould by using nitrogen;

a5, dripping the PDMS mixture in the A2 into the surface of the mould processed in the step S4, which has a structure opposite to the micro-convex cone on the surface of the velvet arrowroot blade, and spin-coating for 10-20S at the rotating speed of 400 r/min; then putting the substrate into a drying oven with the temperature of 90 ℃ for heating and curing for 30min, and taking the cured PDMS out of the mold to obtain a PDMS film with the same structure surface as the micro-convex cone on the surface of the velvet arrowroot blade;

a6, attaching the PDMS film in A5 to a stainless steel template (the thickness is 100-300 mu m) provided with a plurality of through holes with different apertures by adopting a PET double faced adhesive tape, wherein the surface of the PDMS film with the structure the same as the micro-convex cone on the surface of the velvet arrowroot blade is adhered to the stainless steel template; placing the stainless steel template in a vacuum adsorption device, starting vacuum adsorption, and forming a concave shape at the through hole by the PDMS film due to the pressure difference between the upper surface and the lower surface; dripping the PDMS mixture in the A2 into the surface of the side of the PDMS film with a concave shape, and spin-coating for 10s at the rotating speed of 400 r/min; then heating and curing the PDMS film for 15min at 60 ℃ by adopting an infrared lamp, then placing the PDMS film into an oven with the temperature of 90 ℃ to bake the PDMS film for 50min again to completely cure the PDMS, and finally stripping the PDMS film from the stainless steel template;

a7, adding AgNWs (XF-J02, jiangsu Xiancheng nano material science and technology Co., ltd.) into absolute ethyl alcohol, and performing ultrasonic dispersion for 15min to obtain AgNWs dispersion liquid for later use; wherein the mass ratio of AgNWs to absolute ethyl alcohol is 1:5;

and A8, placing the PDMS film in the A6 in a plasma cleaning machine, treating the PDMS film for 4min by using oxygen plasma, spraying AgNWs dispersion liquid on the surface of the PDMS film with a micro-convex cone structure with the surface of a velvet arrowroot blade by using a spray gun until the surface resistance value of the PDMS film is 20 omega, and finally placing the PDMS film in a drying oven with the temperature of 90 ℃ for annealing treatment for 50min to completely evaporate the solvent in the AgNWs dispersion liquid, thus preparing the bionic microarray flexible electrode.

The embodiment of the application also provides a preparation method of the ionic gel dielectric layer, which comprises the following steps:

mixing PVDF-HFP (Sigma-Aldrich, 427179-100 g) with acetone, stirring at 60 ℃ for 3h, adding EMIM TFSI, and continuously stirring uniformly to obtain a mixed solution; wherein the mass ratio of EMIM TFSI (aladdin, E101506-5 g), PVDF-HFP and acetone is 1;

and spin-coating the mixed solution on glass for 50s at the rotating speed of 400r/min, then putting the glass into a vacuum drying oven at the temperature of 50 ℃ for annealing for 2h, and stripping the mixture on the glass to obtain the ionic gel dielectric layer.

The bionic microarray flexible electrode prepared in the embodiment 1 and the ionic gel dielectric layer are assembled into a flexible pressure sensor, and the specific method comprises the following steps:

preparing two bionic microarray flexible electrodes according to the method in the embodiment 1, leading out leads from the two bionic microarray flexible electrodes, bonding the leads and the electrodes by using conductive silver paste, and then placing the electrodes in a 90 ℃ oven for curing for 50min; and then the ionic gel dielectric layer prepared in the embodiment 1 is arranged between the two bionic microarray flexible electrodes 6, and the polyimide adhesive tape is used for sealing the periphery of the bionic microarray flexible electrodes 6, so that the assembly of the flexible pressure sensor is completed.

The surface topography of the bionic microarray flexible electrode prepared in the embodiment 1 is shown in fig. 7, and it can be seen from fig. 7 that a large number of cone-shaped structures with micron-scale sizes are uniformly distributed on a millimeter-scale hemispherical array, that is, the surface topography of a PDMS film copied with a fresh velvet arrowroot blade surface microstructure is obtained by twice die-reversing, the diameter of each cone is about 15-25 μm, and the height is about 20-30 μm.

The sensitivity and response curves of the assembled flexible pressure sensor of example 1 above were tested and the results are shown in fig. 8.

As can be seen in fig. 8. The flexible pressure sensor has higher sensitivity in the range of 0-90KPa, and ensures that the sensor can accurately sense the pressure in a larger measurement range, particularly, the sensitivity is as high as 37.5KPa in a lower pressure area ^-1 The sensor can sense extremely weak pressure signals such as pulse vibration and the like, and the application range of the flexible sensor is greatly widened.

The pulse of the human body was measured by testing the flexible pressure sensor assembled in the above example 1, the flexible sensor was applied to the arm pulse position of the volunteer with medical tape, and the output signal of the sensor was measured by using the LCR source meter, and the result is shown in fig. 9.

As can be seen from fig. 9, the flexible pressure sensor can continuously collect the waveforms of the pulse waves of the human body, the main wave (P wave), the tidal wave (T wave) and the dicrotic wave (D wave) in each waveform can be clearly identified, and important physiological information can be extracted from the waveforms for evaluating the health status of the human body.

The flexible pressure sensor assembled in the above embodiment 1 was tested to detect the sole pressure of a human body, the flexible pressure sensor was applied to the heel of a volunteer with a medical tape, and the output signal of the human body during walking was detected with an LCR source meter, and the result is shown in fig. 10.

As can be seen from FIG. 10, the sensor signal rapidly increases when the volunteer's heel touches the ground, and returns to the original level when the volunteer's heel leaves the ground, and the activity status of the volunteer can be analyzed by the information on the magnitude of the pressure and the pace frequency.

The invention is not to be considered as limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed.

Claims

1. A preparation method of a bionic microarray flexible electrode is characterized by comprising the following steps:

providing a plant leaf with leaf surface texture;

preparing AgNWs dispersion liquid, spraying the AgNWs dispersion liquid on a mold subjected to vacuum adsorption, and annealing to obtain the bionic microarray flexible electrode;

still include before attaching the surface opposite with the plant leaf surface of mould on the template that is equipped with a plurality of through-holes: dripping the PDMS mixture into the surface of the mold opposite to the surface of the plant leaf, performing spin coating and curing, and taking the cured PDMS out of the mold to obtain a PDMS film with a micro-cone surface; then attaching the surface of the PDMS film in the shape of a micro cone to a template provided with a plurality of through holes, and separating the PDMS film from the template through vacuum adsorption; spraying the AgNWs dispersion liquid onto a PDMS film subjected to vacuum adsorption, and annealing to obtain a bionic microarray flexible electrode;

before the AgNWs dispersion is sprayed on the PDMS film after vacuum adsorption, the method also comprises the following steps: dripping the PDMS mixture into the surface of the side, far away from the side of the micro-cone, of the PDMS film, performing spin coating, curing the PDMS, and separating the cured PDMS film from the template; and spraying the AgNWs dispersion liquid onto the cured PDMS film, and annealing to obtain the bionic microarray flexible electrode.

2. The method of claim 1, wherein before dropping the PDMS mixture onto the surface of the mold opposite to the surface of the plant leaf, the method further comprises: and putting the mould into an alcohol solution for passivation.

3. The method for preparing a bionic microarray flexible electrode according to claim 1, wherein the PDMS mixture is dripped on the surface of the mold opposite to the surface of the plant leaf, and is then spin-coated and cured, wherein the spin-coating specifically comprises: spin-coating at 300-500 r/min for 10-20s; the curing is specifically as follows: curing at 80-100 deg.c for 20-40 min.

4. The method for preparing a bionic microarray flexible electrode according to claim 1, wherein the PDMS mixture is dropped on the surface of the PDMS film far away from the side of the micro-cone, and then the PDMS is solidified by spin coating, wherein the spin coating specifically comprises: spin-coating at 300-500 r/min for 8-12 s; the curing method specifically comprises the following steps: firstly heating and curing for 10-20 min under an infrared lamp, and then heating for 40-60min in an oven at 80-100 ℃.

5. The method for preparing a bionic microarray flexible electrode according to claim 1, wherein the AgNWs dispersion is prepared by the following steps: adding AgNWs into absolute ethyl alcohol, and performing ultrasonic dispersion to obtain AgNWs dispersion liquid;

the annealing treatment specifically comprises the following steps: annealing in a baking oven at 80-100 ℃ for 40-60 min.

6. A bionic microarray flexible electrode, which is prepared by the preparation method of any one of claims 1 to 5.

7. A flexible pressure sensor, comprising:

a pair of biomimetic microarray flexible electrodes according to claim 6;

8. The flexible pressure sensor of claim 7, wherein the method of making the ionic gel dielectric layer comprises the steps of: