A bionic flexible pressure sensor with a stiffness gradient microstructure distribution

Abstract

The application discloses a kind of bionic flexible pressure sensor with stiffness gradient microstructure distribution, comprising: at least 3 conductive layers, each conductive layer is sequentially overlapped arrangement;A plurality of convex microstructures are located between two adjacent conductive layers, and the convex microstructure has conductivity;Convex microstructure can be deformed to change the contact area of convex microstructure and conductive layer;The stiffness of the convex microstructure of different layers is different, and different degrees of deformation occur.Due to the sensor when receiving smaller pressure, the convex microstructure with smaller stiffness is deformed under pressure to change resistance, when the pressure increases, the convex microstructure with larger stiffness is deformed under pressure to change resistance.Pressure changes in a larger range, can be detected, realize the effect of large range.Due to the top surface of convex microstructure is curved, small change of pressure can also cause large change of the top surface area of convex microstructure, so as to have higher sensitivity.Therefore, the sensor realizes the consideration of large range and high sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensing, in particular to a bionic flexible pressure sensor with stiffness gradient microstructure distribution. BACKGROUND

[0002] In recent years, flexible pressure sensors have attracted more and more attention of researchers due to their wide application in human-computer interaction, electronic skin, intelligent wearable and other fields. At present, there are numerous researches on the selection of flexible pressure sensor materials, the design of microstructure and other aspects, the main purpose of which is to improve the performance level of the sensor, especially its sensitivity and working range. In the prior art, there is an exclusive relationship between sensitivity and working range, high sensitivity usually brings low range, and high range usually accompanies low sensitivity.

[0003] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a bionic flexible pressure sensor with stiffness gradient microstructure distribution to solve the problem that high range and high sensitivity of the pressure sensor cannot be considered in the prior art.

[0005] The technical solution adopted by the present application to solve the technical problem is as follows:

[0006] A bionic flexible pressure sensor with stiffness gradient microstructure distribution, comprising:

[0007] At least three conductive layers, each conductive layer being arranged in turn and overlapping;

[0008] A plurality of convex microstructures located between adjacent two conductive layers, and the convex microstructures have conductivity;

[0009] Wherein, the convex microstructure is deformable to change the contact area between the convex microstructure and the conductive layer;

[0010] The convex microstructures of different layers have different degrees of deformation due to different stiffness.

[0011] The bionic flexible pressure sensor with stiffness gradient microstructure distribution, wherein the convex microstructures of different layers are arranged in turn and overlapping according to the stiffness.

[0012] The bionic flexible pressure sensor with stiffness gradient microstructure distribution, wherein the convex microstructure adopts an ellipsoidal crown-shaped convex microstructure, the long axis of the ellipsoidal crown-shaped convex microstructure is perpendicular to the conductive layer, and the short axis of the ellipsoidal crown-shaped convex microstructure is parallel to the conductive layer.

[0013] The bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the same layer of the convex microstructure has several convex microstructures, and the convex microstructures of the same layer have the same structure; and / or

[0014] The outermost conductive layer is provided with an electrode.

[0015] The bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the conductive layer and the convex microstructure both comprise:

[0016] An elastic matrix;

[0017] A conductive material dispersed in the elastic matrix.

[0018] The bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the elastic matrix comprises at least one of an epoxy resin, a thermoplastic polyurethane, a polyacrylate, a polyvinylidene fluoride, a polystyrene, a polyamide, a polyimide, a polyethylene terephthalate, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-ethylene-butylene-styrene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, a natural rubber, a styrene-butadiene rubber, a cis-butadiene rubber, an isoprene rubber, a silicone rubber, a chlorobutyl rubber, a butyl rubber, a nitrile rubber, an ethylene-propylene rubber, a fluorine rubber, and a polydimethylsiloxane; and / or

[0019] The conductive material comprises at least one of a single metal nanomaterial, a multi-element alloy nanomaterial, and a carbon material.

[0020] The bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the single metal nanomaterial comprises at least one of gold nanoparticles, silver nanoparticles, and copper nanoparticles.

[0021] The multi-element alloy nanomaterial comprises at least one of aluminum boron alloy nanoparticles, aluminum chromium alloy nanoparticles, iron manganese alloy nanoparticles, aluminum chromium yttrium nanoparticles, and silver copper palladium nanoparticles.

[0022] The carbon material comprises at least one of carbon nanotubes, graphite, graphene, and carbon black.

[0023] A preparation method of the bionic flexible pressure sensor with the stiffness gradient microstructure distribution, comprising the following steps:

[0024] The conductive layer and the convex microstructure are prepared layer by layer to obtain the bionic flexible pressure sensor with the stiffness gradient microstructure distribution.

[0025] The preparation method of the bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the conductive layer and the convex microstructure each comprise:

[0026] An elastic matrix;

[0027] A conductive material dispersed in the elastic matrix;

[0028] The layer-by-layer preparation of the conductive layer and the convex microstructure to obtain the bionic flexible pressure sensor with the stiffness gradient microstructure distribution comprises:

[0029] A template method is used to place raw materials in a template and remove the template after solidification to obtain a conductive layer and a convex microstructure, or a raw material is flattened and a stamping template or etching is used to form a conductive layer and a convex microstructure;

[0030] A different template or stamping template or etching parameter is used to form another conductive layer and another convex microstructure;

[0031] One convex microstructure is pasted with another conductive layer, and a conductive layer is formed on another convex microstructure to obtain the bionic flexible pressure sensor with the stiffness gradient microstructure distribution.

[0032] The preparation method of the bionic flexible pressure sensor with the stiffness gradient microstructure distribution, wherein the conductive layer and the convex microstructure each comprise:

[0033] An elastic matrix;

[0034] A conductive material dispersed in the elastic matrix;

[0035] The layer-by-layer preparation of the conductive layer and the convex microstructure to obtain the bionic flexible pressure sensor with the stiffness gradient microstructure distribution comprises:

[0036] A 3D printing method is used to layer-by-layer print a conductive layer and a convex microstructure to obtain the bionic flexible pressure sensor with the stiffness gradient microstructure distribution.

[0037] Beneficial effects: Since the bionic flexible pressure sensor is subjected to a smaller pressure, the convex microstructure with smaller stiffness is deformed under pressure to change the resistance, so that it can be detected, and when the pressure increases, the convex microstructure with larger stiffness is deformed under pressure to change the resistance, so that it can also be detected. That is, the pressure can be detected in a large range, achieving a large range effect. Moreover, in the detection process, since the top surface of the convex microstructure is curved, a small change in pressure can also cause a large change in the area of the top surface of the convex microstructure, thereby having high sensitivity. Therefore, the bionic flexible pressure sensor realizes the combination of large range and high sensitivity. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the biomimetic flexible pressure sensor with stiffness gradient microstructure distribution in this invention.

[0039] Figure 2 This is a diagram showing the changes in the conductive layer and convex hull microstructure before and after being subjected to external force in this invention.

[0040] Figure 3 This is a diagram showing the series and parallel relationship of the resistances of the conductive layer and the convex hull microstructure in this invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1. Upper electrode lead; 2. Upper electrode layer; 3, 5, 7, 9. Conductive layer; 4, 6, 8. Convex hull microstructure; 10. Lower electrode layer; 11. Lower electrode lead. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0044] Please also refer to Figures 1-3 This invention provides some embodiments of a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution.

[0045] To date, various types of high-sensitivity pressure sensors have been reported in the literature. These include introducing hollow three-dimensional structures with free volume to improve sensor sensitivity and minimum detection limit, and introducing three-dimensional pyramidal micro / nano structures to increase sensor sensitivity by reducing the stress-bearing area and enhancing the sensor's strain. However, the sensing range of currently reported high-sensitivity sensors is generally relatively narrow. Human skin is a well-known sensory organ with typical pressure-sensing functions, easily sensing extremely weak pressure such as a hair falling on the skin, as well as painful pressure up to 90 kPa, exhibiting excellent sensitivity and a large sensing range. This is due to the raised folds distributed beneath the skin's epidermis; these raised micro / nano structures act as stress concentration points, amplifying external excitation signals, which are then transmitted to the central nervous system via sensory nerves. Inspired by these raised microstructures in the skin, pressure sensors can be endowed with even higher sensitivity.

[0046] like Figures 1-2 As shown, the biomimetic flexible pressure sensor of the present invention, which has a stiffness gradient microstructure distribution, includes:

[0047] At least three conductive layers (3, 5, 7, 9) are arranged in an overlapping manner.

[0048] Several convex hull microstructures (4, 6, 8) are located between two adjacent conductive layers (3, 5, 7, 9), and the convex hull microstructures (4, 6, 8) are conductive;

[0049] The convex hull microstructures (4, 6, 8) are deformable to change the contact area between the convex hull microstructures (4, 6, 8) and the conductive layer (3, 5, 7, 9);

[0050] The different stiffnesses of the convex hull microstructures (4, 6, 8) in different layers result in different degrees of deformation.

[0051] It's worth noting that, typically, the stiffer convex hull microstructures (4, 6, 8) deform less under stress, resulting in a smaller contact area and higher resistance between them and the upper conductive layer (3, 5, 7, 9). Conversely, the less stiff convex hull microstructures (4, 6, 8) deform more under stress, leading to a larger contact area and lower resistance. As the pressure on the sensor increases, the contact between the convex hull microstructures and the upper conductive layer (3, 5, 7, 9) changes from point contact to surface contact, thus reducing resistance. In this biomimetic flexible pressure sensor, under low pressure, the less stiff convex hull microstructures (4, 6, 8) deform and change their resistance, thus being detected. Conversely, as the pressure increases, the more stiff convex hull microstructures (4, 6, 8) deform and change their resistance, also being detected. In other words, the sensor can detect pressure variations over a wide range, achieving a large detection range. Furthermore, during the detection process, because the top surface of the convex hull microstructure (4, 6, 8) is curved, even a small change in pressure can lead to a large change in the top surface area of ​​the convex hull microstructure (4, 6, 8), thus exhibiting high sensitivity. Therefore, the biomimetic flexible pressure sensor achieves a balance between a large range and high sensitivity.

[0052] The magnitude of the external force F is negatively correlated with the resistance R of the sensor; when F increases, R decreases, and when F decreases, R increases. R is:

[0053] R = R1 + R2 + ... + R i +…+R n

[0054]

[0055] Among them, R i r represents the resistance between the i-th conductive layer and the i-th convex hull microstructure. ij The resistance between the i-th conductive layer and the j-th convex hull microstructure in the i-th layer is represented by n, where n represents the number of convex hull microstructures and m represents the number of convex hull microstructures in the i-th layer.

[0056] In a preferred implementation of this invention, such as Figures 1-2 As shown, the convex hull microstructures (4, 6, 8) of different layers are arranged in an overlapping manner according to their stiffness.

[0057] Specifically, since the stiffness of the convex hull microstructures (4, 6, 8) in different layers is different, in order to facilitate the stability of each layer of convex hull microstructures (4, 6, 8) during deformation, the convex hull microstructures (4, 6, 8) are arranged in order of stiffness. For example, the convex hull microstructure 8 with the lowest stiffness is placed on the bottom conductive layer 9 of the sensor, the convex hull microstructure 7 with the second lowest stiffness is placed on the second to last conductive layer 7 of the sensor, and so on. The convex hull microstructure 4 with the highest stiffness is placed on the second conductive layer 5 of the sensor, and finally the top conductive layer 3 is placed on the convex hull microstructure 4 with the highest stiffness.

[0058] It is understandable that since the convex hull microstructures (4, 6, 8) of each layer are stacked, when the convex hull microstructures (4, 6, 8) are subjected to force, they will apply pressure to the corresponding convex hull microstructures (4, 6, 8) of the next layer. Thus, the stacked convex hull microstructures (4, 6, 8) form a series structure of resistors, which makes it easier to establish the relationship between pressure and resistance.

[0059] In a preferred implementation of this invention, such as Figures 1-2 As shown, the convex hull microstructures (4, 6, 8) are ellipsoidal convex hull microstructures. The major axis of the ellipsoidal convex hull microstructures is perpendicular to the conductive layer (3, 5, 7, 9), and the minor axis of the ellipsoidal convex hull microstructures is parallel to the conductive layer (3, 5, 7, 9).

[0060] Specifically, to ensure that the convex hull microstructures (4, 6, 8) do not tip over during deformation under stress, the convex hull microstructures adopt an ellipsoidal crown shape. An ellipsoidal crown is formed by cutting a portion of an ellipsoid. Therefore, the ellipsoidal crown-shaped convex hull microstructure has two surfaces: one curved and the other planar, facing the two adjacent conductive layers (3, 5, 7, 9) respectively. Due to the presence of the planar surface, the convex hull microstructures (4, 6, 8) will compress vertically during deformation, rather than moving outwards.

[0061] The planar surface is circular with a diameter of d. The height of the convex hull microstructure (4, 6, 8) along its major axis is h, and the height-to-diameter ratio is h / d. The stiffness of the convex hull microstructure (4, 6, 8) is changed by adjusting the height-to-diameter ratio. Generally, a larger height-to-diameter ratio results in lower stiffness and easier deformation; a smaller ratio results in higher stiffness and less deformation. The height-to-diameter ratio ranges from [1, 3]. Different layers of convex hull microstructures (4, 6, 8) are arranged in an overlapping manner according to their stiffness and their height-to-diameter ratio.

[0062] Since the longitudinal section of the ellipsoid is elliptical and the cross section is circular, with the center of the ellipsoid as the origin, the radial direction as the x-axis, and the height direction as the y-axis, the equation of the ellipse is:

[0063]

[0064] Therefore, as the deformation proceeds, the following relationship is satisfied:

[0065]

[0066] Where H represents the height of the convex hull microstructure during deformation, and D represents the diameter of the contact surface during deformation. As the convex hull microstructure deforms, the contact area of ​​a single convex hull microstructure is:

[0067]

[0068] Where S represents the contact area of ​​a single convex hull microstructure, D represents the diameter of the contact surface, and π represents pi.

[0069] As the external force F increases, the height of the convex hull microstructure decreases, and the contact area increases. The external force F can be approximated as F∝(h 2 -H 2 ),because and Then F∝S.

[0070] As the external force F increases, the convex hull microstructures of each conductive layer deform. Although the degree of deformation varies among different layers, for every increase of ΔF, ΔS... 总 The size difference is not significant, △S 总 This represents the change in contact area of ​​all convex hull microstructures. Since F∝S, then F∝S 总 S 总 This represents the contact area of ​​all convex hull microstructures. If S... 总 ∝R, where R represents the resistance of the sensor, then F∝R. Of course, the actual situation may deviate, but the external force F and the sensor resistance R are generally linearly related.

[0071] In a preferred implementation of this invention, such as Figures 1-3 As shown, there are several convex hull microstructures (4, 6, 8) in the same layer, and the structures of the convex hull microstructures (4, 6, 8) in the same layer are the same.

[0072] Specifically, to further improve the uniformity of force distribution on the sensor and prevent damage, several convex hull microstructures (4, 6, 8) are present in the same layer. These microstructures (4, 6, 8) have identical structures, shapes, aspect ratios, and are fabricated using the same material. The multiple convex hull microstructures (4, 6, 8) in the same layer are arranged in a matrix. Within the same layer, each convex hull microstructure (4, 6, 8) forms a parallel resistor structure, while microstructures (4, 6, 8) in different layers form a series resistor structure.

[0073] In a preferred implementation of this invention, such as Figures 1-3 As shown, electrodes are provided on the outermost conductive layer (3, 9).

[0074] Specifically, electrodes and electrode leads are respectively disposed on the upper and lower surfaces of the tactile sensor. The electrodes are divided into an upper electrode layer 2 and a lower electrode layer, and the electrode leads are divided into an upper electrode lead 1 and a lower electrode lead. The resistance of the sensor can be detected through the electrodes and electrode leads, thereby obtaining the pressure applied to the sensor.

[0075] In a preferred embodiment of the present invention, the conductive layer (3, 5, 7, 9) comprises:

[0076] Elastic matrix;

[0077] Conductive material is dispersed within the elastic matrix.

[0078] Specifically, the conductive layer (3, 5, 7, 9) is made of an elastic matrix and conductive material, and the conductive layer (3, 5, 7, 9) has a certain degree of elasticity and conductivity.

[0079] In a preferred embodiment of the present invention, the convex hull microstructures (4, 6, 8) all include:

[0080] Elastic matrix;

[0081] Conductive material is dispersed within the elastic matrix.

[0082] Specifically, conductive materials are dispersed in an elastic matrix to form conductive layers (3, 5, 7, 9) and convex microstructures (4, 6, 8). Due to the presence of conductive materials, the conductive layers (3, 5, 7, 9) and convex microstructures (4, 6, 8) have conductive properties. However, the contact area between the conductive layers (3, 5, 7, 9) and the convex microstructures (4, 6, 8) varies with the magnitude of the applied force. When the force is greater, the contact area is larger, resulting in a lower resistance between the conductive layers (3, 5, 7, 9) and the convex microstructures (4, 6, 8); when the force is less, the contact area is smaller, resulting in a higher resistance between the conductive layers (3, 5, 7, 9) and the convex microstructures (4, 6, 8).

[0083] Because the conductive layer (3, 5, 7, 9) and the convex hull microstructure (4, 6, 8) are made of an elastic matrix, both the conductive layer (3, 5, 7, 9) and the convex hull microstructure (4, 6, 8) deform under pressure, allowing for sufficient contact between them and ensuring that the resistance between them changes.

[0084] In a preferred embodiment of the present invention, the elastic matrix comprises at least one of the following: epoxy resin, thermoplastic polyurethane, polyacrylate, polyvinylidene fluoride, polystyrene, polyamide, polyimide, polyethylene terephthalate, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, silicone rubber, chloroprene rubber, butyl rubber, nitrile rubber, ethylene-propylene rubber, fluororubber, and polydimethylsiloxane.

[0085] Specifically, the elastic matrix may also be selected from at least one of the following: styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, diene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyamide-based thermoplastic elastomers (TPAE), or thermoplastic vulcanizates (TPV).

[0086] In a preferred embodiment of the present invention, the conductive material includes at least one of the following: elemental metal nanomaterials, multi-element alloy nanomaterials, and carbon materials.

[0087] Specifically, to ensure relatively uniform conductivity, the conductive material is small in size and uniformly dispersed within the elastic matrix; the conductive material is specifically nanoscale or microscale. It can be a single metal, alloy, or carbon material.

[0088] In a preferred embodiment of the present invention, the elemental metal nanomaterial includes at least one of gold nanoparticles, silver nanoparticles, and copper nanoparticles.

[0089] Specifically, elemental metal nanomaterials can be made of gold, silver, or copper, which have good electrical conductivity.

[0090] In a preferred embodiment of the present invention, the multi-element alloy nanomaterial includes at least one of aluminum-boron alloy nanoparticles, aluminum-chromium alloy nanoparticles, iron-manganese alloy nanoparticles, aluminum-chromium-yttrium nanoparticles, and silver-copper-palladium nanoparticles.

[0091] Specifically, using alloy nanomaterials can reduce costs while ensuring better conductivity.

[0092] In a preferred embodiment of the present invention, the carbon material includes at least one of carbon nanotubes, graphite, graphene, and carbon black.

[0093] Specifically, when carbon materials are used, electrical conductivity can also be achieved.

[0094] Based on the biomimetic flexible pressure sensor with stiffness gradient microstructure distribution described in any of the above embodiments, the present invention also provides a preferred embodiment of a method for fabricating a biomimetic flexible pressure sensor with stiffness gradient microstructure distribution:

[0095] The method for fabricating a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution according to an embodiment of the present invention includes the following steps:

[0096] Step S100: Prepare conductive layers and convex hull microstructures layer by layer to obtain a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution.

[0097] Specifically, the conductive layer and the convex hull microstructure are fabricated layer by layer to obtain the sensor. Each conductive layer and each convex hull microstructure can be integrally formed or fabricated separately and then connected.

[0098] Step S100 specifically includes:

[0099] Step S111: The raw material is placed in the template using the template method and cured. After curing, the template is removed to obtain a conductive layer and a convex microstructure.

[0100] Specifically, the conductive layer and the convex microstructure are prepared by template method. First, a template is prepared and multiple grooves are formed on the plate to form the template. Then, the raw material is placed on the template and the convex microstructure is formed at the groove. After curing, the template is removed to form a conductive layer and a convex microstructure.

[0101] Step S112: After the raw material is laid flat, a conductive layer and a raised microstructure are formed by imprinting a template or etching.

[0102] Specifically, conductive layers or convex microstructures are prepared using imprinting or etching methods. For example, the raw material is first laid flat to form a raw material layer, then an imprinting template is used to imprint the raw material layer. After curing, the imprinting template is removed, resulting in a conductive layer and a convex microstructure. Alternatively, the raw material is first laid flat to form a raw material layer, and after curing and etching, a conductive layer and a convex microstructure are formed. In this case, the conductive layer and the convex microstructure are integrally formed.

[0103] Step S120: Using different templates, imprint templates, or etching parameters, another conductive layer and another convex hull microstructure are formed.

[0104] Specifically, by adjusting the size of the grooves on the (imprinting) template and the etching parameters, convex hull microstructures of different sizes are formed, thereby creating another conductive layer and another convex hull microstructure. At this point, the conductive layer and the convex hull microstructure are integrally formed.

[0105] Step S130: A convex hull microstructure is bonded to another conductive layer, and a conductive layer is formed on the other convex hull microstructure to obtain a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution.

[0106] Specifically, the convex hull microstructure is bonded to another conductive layer, and each convex hull microstructure and conductive layer can be bonded in sequence until the outermost convex hull microstructure forms a conductive layer, thus obtaining the sensor.

[0107] Step S100 specifically includes:

[0108] Step S101: Using 3D printing, conductive layers and convex hull microstructures are printed layer by layer to obtain a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution.

[0109] 3D printing can be used to directly form the conductive layers and the convex microstructures of each layer to obtain the sensor.

[0110] Based on this, electrodes and electrode leads can be formed on the outermost conductive layer.

[0111] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution, characterized in that, include: At least three conductive layers, which are arranged in a sequentially overlapping manner; Several convex hull microstructures are located between two adjacent conductive layers, and the convex hull microstructures are conductive; The convex hull microstructure is deformable to change the contact area between the convex hull microstructure and the conductive layer; Different layers of the convex hull microstructure exhibit varying degrees of deformation due to their different stiffness. The convex hull microstructures of different layers are arranged in an overlapping manner according to their stiffness; The convex hull microstructure is an ellipsoidal crown-shaped convex hull microstructure, the major axis of which is perpendicular to the conductive layer, and the minor axis of which is parallel to the conductive layer; the stiffness of the convex hull microstructure is changed by adjusting the height-to-diameter ratio of the convex hull microstructure. There are several convex hull microstructures in the same layer, and the convex hull microstructures in the same layer have the same structure. The height-to-diameter ratio ranges from [1, 3]. When the convex hull microstructure is subjected to force, it will apply pressure to the corresponding convex hull microstructure in the next layer. The overlapping layers of convex hull microstructures form a series structure of resistors.

2. The biomimetic flexible pressure sensor with stiffness gradient microstructure distribution according to claim 1, characterized in that, Electrodes are provided on the outermost conductive layer.

3. The biomimetic flexible pressure sensor with stiffness gradient microstructure distribution according to claim 1, characterized in that, Both the conductive layer and the convex hull microstructure include: Elastic matrix; Conductive material is dispersed within the elastic matrix.

4. The biomimetic flexible pressure sensor with stiffness gradient microstructure distribution according to claim 3, characterized in that, The elastic matrix comprises at least one of the following: epoxy resin, thermoplastic polyurethane, polyacrylate, polyvinylidene fluoride, polystyrene, polyamide, polyimide, polyethylene terephthalate, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, silicone rubber, chloroprene rubber, butyl rubber, nitrile rubber, ethylene-propylene rubber, fluororubber, and polydimethylsiloxane; and / or The conductive material includes at least one of the following: elemental metal nanomaterials, multi-element alloy nanomaterials, and carbon materials.

5. The biomimetic flexible pressure sensor with stiffness gradient microstructure distribution according to claim 4, characterized in that, The elemental metal nanomaterials include at least one of gold nanoparticles, silver nanoparticles, and copper nanoparticles. The multi-element alloy nanomaterials include at least one of the following: aluminum-boron alloy nanoparticles, aluminum-chromium alloy nanoparticles, iron-manganese alloy nanoparticles, aluminum-chromium-yttrium nanoparticles, and silver-copper-palladium nanoparticles. The carbon material includes at least one of carbon nanotubes, graphite, graphene, and carbon black.

6. A method for fabricating a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution as described in any one of claims 1 to 5, characterized in that, Including the following steps: A biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution was obtained by fabricating conductive layers and convex hull microstructures layer by layer.

7. The method for fabricating a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution according to claim 6, characterized in that, Both the conductive layer and the convex hull microstructure include: Elastic matrix; A conductive material is dispersed within the elastic matrix; The stepwise fabrication of conductive layers and convex hull microstructures yields a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution, including: The template method is used to place the raw material in the template and then remove the template after curing to obtain a conductive layer and a raised microstructure. Alternatively, the raw material can be flattened and then a conductive layer and a raised microstructure can be formed by imprinting a template or etching. By using different templates, imprint templates, or etching parameters, another conductive layer and another convex hull microstructure can be formed. By attaching a convex hull microstructure to another conductive layer and forming a conductive layer on the other convex hull microstructure, a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution is obtained.

8. The method for fabricating a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution according to claim 6, characterized in that, Both the conductive layer and the convex hull microstructure include: Elastic matrix; A conductive material is dispersed within the elastic matrix; The stepwise fabrication of conductive layers and convex hull microstructures yields a biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution, including: A biomimetic flexible pressure sensor with a stiffness gradient microstructure distribution was obtained by printing conductive layers and convex hull microstructures layer by layer using 3D printing.

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