Flexible sensor and preparation method and application thereof

Abstract

The invention relates to the field of functional devices, and discloses a flexible sensor and a preparation method and application thereof.The flexible sensor comprises a micropore structure and a conductive inorganic matter and an electrode which are loaded on the surface of the micropore structure, the upper top layer and the lower bottom layer of the micropore structure are compact silica gel layers, and the upper top layer and the lower bottom layer of the micropore structure are made of flexible materials. The middle part of the microporous structure is provided with mutually communicated three-dimensional network structures, and the porosity of the three-dimensional network structures is gradually increased from top to bottom. The flexible sensor can integrate pressure detection, stretching and bending, has high sensitivity, can be applied to a flexible strain sensor, and can broaden the actual application scene of the flexible sensor.

Description

Technical Field

[0001] The present invention belongs to the field of functional devices, and in particular relates to a flexible sensor and a preparation method and application thereof. Background Art

[0002] Skin is a multi-layer composite material. The thickness of the epidermis is between 0.06 and 1.00 mm. It is composed of the upper layer of cells and has a certain mechanical strength, which plays a role in protecting the lower dermis. The thickness of the dermis is 1 to 4 mm, containing cells and extracellular matrix (Advanced Materials 2018, 30(12), 1706299). The extracellular matrix is ​​mainly a substrate for cell adhesion, growth and differentiation. It also contains a large number of collagen fibrils and elastic fibers, which provide mechanical support for surrounding tissues and organs.

[0003] External forces are transmitted to the dermis and subcutaneous tissue through the epidermis, while internal forces are transmitted to the epidermis through the dermis (Science 2017, 355(6320), 59–64). Therefore, under normal conditions, the mechanical behavior of the dermis dominates the mechanical behavior of the skin (Science Advances 2018, 4(1)), so the internal forces of collagen fibrils in the dermis are an important source of mechanical stimulation that affects mechanochemical transduction in the dermis and epidermis. The elastic tissue in the skin forms a three-dimensional network composed of branched fibers with different diameters and elastin contents (Nature Electronics 2018, 1, 589–595). The passive mechanical properties of the skin roughly reflect the mechanical behavior of the collagen and elastic networks that constitute most of the macromolecular components of the dermis (Science 2016, 353(6300), 682–687). Elastic fibers are thought to contribute to the initial low modulus portion of mechanical behavior, providing restorative capacity to the collagen network in the skin, while collagen fibers prevent premature mechanical failure of the skin (Cell 2014, 157(3), 664–675).

[0004] Thanks to the three-dimensional elastic network structure of the dermis in the skin, the skin has excellent perception of mechanical stimulation. However, to achieve accurate perception of force in three-dimensional space, it is also inseparable from the accurate perception of three different forces of pressure, stretching and bending by different mechanical receptors in the skin. Therefore, flexible sensors that simulate the skin's perception of force in three-dimensional space are expected to be used in the field of electronic smart skin in the future. Various activities in daily human life can be monitored in real time and non-invasively under the most natural conditions, so that electronic smart skin and human skin can enhance each other and play a huge role in many different fields such as research, health and fitness, and clinical environments. However, the functions of current flexible sensors tend to be single and the sensitivity is not high, and there is still a certain gap between them and the functions of human skin. Summary of the invention

[0005] In order to solve the defects of the above-mentioned flexible sensors such as single function and low sensitivity, the present invention provides a flexible sensor and a preparation method and application thereof. On the one hand, the flexible sensor can integrate the detection of pressure, stretching and bending and has high sensitivity. On the other hand, the flexible sensor can be applied to flexible strain sensors, which can broaden the practical application scenarios of flexible sensors.

[0006] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a flexible sensor, wherein the flexible sensor includes a microporous structure and a conductive inorganic substance and an electrode loaded on the surface of the microporous structure, wherein the upper top layer and the lower bottom layer of the microporous structure are dense silica gel layers, and the middle part of the microporous structure has a three-dimensional network structure interconnected with each other, and the porosity of the three-dimensional network structure gradually increases from top to bottom.

[0007] A second aspect of the present invention provides a method for preparing a flexible sensor, wherein the preparation method comprises:

[0008] (1) mixing an elastomeric material with an inorganic salt to obtain a mixture;

[0009] (2) curing the mixture in a mold to construct a non-uniform microporous structure using chemical potential;

[0010] (3) etching the uneven microporous structure with hot water to remove inorganic salts, thereby obtaining a silica gel matrix containing an uneven microporous structure;

[0011] (4) dispersing the conductive inorganic substance in the silica gel matrix by suction filtration to obtain a silica gel matrix loaded with the conductive inorganic substance;

[0012] (5) Drying the silica gel substrate loaded with the conductive inorganic substance and connecting electrodes to obtain a flexible sensor.

[0013] A third aspect of the present invention provides an application of the aforementioned flexible sensor in a flexible strain sensor, wherein the flexible strain sensor includes a simulated human skin in the field of medical health monitoring.

[0014] Through the above technical solution, the advantages of the present invention are:

[0015] (1) A highly sensitive flexible sensor capable of detecting pressure, stretching and bending is obtained by the preparation method described in the present invention. Due to the uneven microporous structure constructed by chemical potential, the upper layer of the silicone matrix is ​​a dense and uniform silicone layer, similar to the epidermis; the middle and lower layers of the silicone matrix are open and connected three-dimensional network structures, and the porosity gradually increases from top to bottom, similar to the three-dimensional network structure in the dermis. Therefore, the silicone matrix successfully simulates the structure of the epidermis and dermis of human skin, and can be used in the field of medical health monitoring to simulate human skin.

[0016] (2) In addition, in terms of function, the microporous structure gives the sensor a good detection effect on pressure, stretching and bending. At the same time, due to the use of suction filtration, a method of physically dispersing graphene, graphene can be embedded in the network structure, which greatly improves the graphene loading (reaching more than 0.8% by weight) and the stability of the graphene loading, thereby forming a relatively continuous conductive path, greatly improving the sensitivity of the sensor. This method for preparing flexible sensors is efficient, controllable, and reproducible; the method has good universality and is easy to operate, solving the problem of traditional flexible sensors with single functions and low sensitivity; the starting materials are cheap and easy to obtain; the reaction conditions are mild and easy to control; the reaction device is simple and the operating cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a method for preparing a flexible sensor according to the present invention;

[0018] Figure 2 This is a schematic diagram of a silica gel matrix with an uneven microporous structure constructed by utilizing chemical potential in the present invention;

[0019] Figure 3 This is a scanning electron microscope photograph of the middle cross section of the silica gel substrate prepared in Example 2 of the present invention;

[0020] Figure 4 This is a scanning electron microscope photograph of the upper part of the longitudinal section of the silica gel substrate prepared in Example 2 of the present invention;

[0021] Figure 5 This is a scanning electron microscope photograph of the lower part of the longitudinal section of the silica gel substrate prepared in Example 2 of the present invention;

[0022] Figure 6 This is a scanning electron microscope photograph of undispersed graphene on a silica gel matrix prepared in Example 2 of the present invention;

[0023] Figure 7 This is a scanning electron microscope photograph of the silica gel matrix prepared in Example 2 of the present invention after graphene is dispersed by suction filtration;

[0024] Figure 8 This is a cross-sectional scanning electron microscope photograph of the silica gel matrix prepared in Example 2 of the present invention after graphene is dispersed by suction filtration;

[0025] Fig. 9 This is a cross-sectional scanning electron microscope photograph of graphene inserted into a silica gel matrix after graphene is dispersed by suction filtration in the silica gel matrix prepared in Example 2 of the present invention;

[0026] Fig.10 This is a pressure sensitivity curve of the flexible sensor prepared in Example 2 of the present invention;

[0027] Fig.11 This is the stretch sensitivity curve of the flexible sensor prepared in Example 2 of the present invention;

[0028] Fig.12 This is a bending sensitivity curve of the flexible sensor prepared in Example 2 of the present invention;

[0029] Fig.13 This is the sensitivity curve of three consecutive compressions of the flexible sensor prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0031] In the present invention, unless otherwise specified, the flexible sensor in the specification is the abbreviation of a high-sensitivity flexible sensor that is manufactured by the method of the present invention and is capable of detecting pressure, stretching and bending.

[0032] As mentioned above, the first aspect of the present invention provides a flexible sensor, wherein the flexible sensor includes a microporous structure and a conductive inorganic substance and an electrode loaded on the surface of the microporous structure, wherein the upper top layer and the lower bottom layer of the microporous structure are dense silica gel layers, and the middle part of the microporous structure has a three-dimensional network structure interconnected with each other, and the porosity of the three-dimensional network structure gradually increases from top to bottom.

[0033] According to the present invention, the porosity of the three-dimensional network structure gradually changes from 0.1-5% to 30-60% from top to bottom.

[0034] According to the present invention, the pores in the three-dimensional network structure gradually decrease in diameter from top to bottom; preferably, the pores in the three-dimensional network structure gradually decrease in diameter from 300-400 μm to 90-110 μm from top to bottom; more preferably, the pores in the three-dimensional network structure gradually decrease in diameter from 300-400 μm to 100-110 μm.

[0035] According to the present invention, the material of the microporous structure is an elastomeric material; preferably, the elastomeric material is silicone rubber; more preferably, the silicone rubber is platinum silicone Ecoflex T10.

[0036] According to the present invention, preferably, the platinum silicone Ecoflex T10 comprises one or more of vinyl-terminated dimethylsiloxane, polysiloxane, alkyl platinum complex and methyl hydrogen silicone oil. Preferably, the alkyl platinum complex is platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane.

[0037] According to the present invention, more preferably, the platinum silicone Ecoflex T10 includes agent A and / or agent B; further preferably, the platinum silicone Ecoflex T10 includes agent A and agent B, and the ratio of agent A to agent B is 1:(0.9-1.1); wherein agent A includes vinyl-terminated dimethylsiloxane and / or polysiloxane, and alkyl platinum complex, and based on the total weight of agent A, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 90-99.9% by weight, and the content of alkyl platinum complex is 0.1-10% by weight; agent B includes vinyl-terminated dimethylsiloxane and / or polysiloxane, and methyl hydrogen silicone oil, and based on the total weight of agent B, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 60-80% by weight, and the content of methyl hydrogen silicone oil is 20-40% by weight.

[0038] In addition, in the present invention, the platinum silicone Ecoflex T10 is purchased from Smooth-On.

[0039] According to the present invention, based on the total weight of the flexible sensor, the loading amount of the conductive inorganic substance is ≥ 0.8 wt %, preferably 2-12 wt %.

[0040] According to the present invention, the conductive inorganic substance is graphene, specifically, the graphene is reduced graphene and / or graphite oxide, preferably reduced graphene, and the basic structure is a layered carbon atom layer. In the present invention, the graphene is purchased from Xiamen Kaina Graphene Technology Co., Ltd.

[0041] According to the present invention, the electrode may be a copper electrode.

[0042] A second aspect of the present invention provides a method for preparing the aforementioned flexible sensor, wherein the method comprises:

[0043] (1) mixing an elastomeric material with an inorganic salt to obtain a mixture;

[0044] (2) curing the mixture in a mold to construct a non-uniform microporous structure using chemical potential;

[0045] (3) etching the uneven microporous structure with hot water to remove inorganic salts, thereby obtaining a silica gel matrix containing an uneven microporous structure;

[0046] (4) dispersing the conductive inorganic substance in the silica gel matrix by suction filtration to obtain a silica gel matrix loaded with the conductive inorganic substance;

[0047] (5) Drying the silica gel substrate loaded with the conductive inorganic substance and connecting electrodes to obtain a flexible sensor.

[0048] According to the present invention, the inorganic salt includes one or more of potassium chloride (KCl), sodium chloride (NaCl), sodium sulfate (Na2SO4) and potassium sulfate (K2SO4).

[0049] According to the present invention, the weight ratio of the elastomeric material to the inorganic salt is 1:(1-4).

[0050] According to the present invention, the mold is made of polytetrafluoroethylene (PTFE) with a size of 50×35×5 mm.

[0051] According to the present invention, the bottom of the mold is attached with filter paper moistened with 0.3-1 mL of deionized water.

[0052] According to the present invention, the curing conditions include: a temperature of 60-100° C. and a curing time of 2-4 hours; preferably, the temperature is 80-90° C. and the curing time is 3-4 hours.

[0053] According to the present invention, the conditions for hot water etching include: the temperature of the hot water is 60-90° C., and the etching time is 12-24 hours.

[0054] According to the present invention, the amount of the conductive inorganic substance used is 60-240 mg relative to 2-8 g of the silica gel matrix.

[0055] In the present invention, specifically, Figure 1 A schematic diagram of a process for preparing a flexible sensor according to the present invention, from Figure 1 It can be seen that:

[0056] (1) Under stirring conditions, an elastomer platinum silicone Ecoflex T10 (silicone rubber Ecoflex) and an inorganic salt potassium chloride (KCl) are uniformly mixed to obtain a mixture;

[0057] (2) curing the mixture obtained in the above step (1) in a mold to construct a non-uniform microporous structure by utilizing chemical potential;

[0058] (3) etching the uneven microporous structure with hot water to remove inorganic salts, thereby obtaining a silica gel matrix containing an uneven microporous structure;

[0059] (4) dispersing the conductive inorganic substance in the silica gel matrix by suction filtration to obtain a silica gel matrix loaded with the conductive inorganic substance;

[0060] (5) Drying the silica gel matrix loaded with conductive inorganic substances obtained in the above step (4) and connecting electrodes to obtain a highly sensitive flexible sensor capable of detecting pressure, stretching and bending.

[0061] Figure 2 This is a schematic diagram of a silica gel matrix with an uneven microporous structure constructed by chemical potential in the present invention. Figure 2 In the process, potassium chloride (KCl) particles have a certain fluidity in the uncured silica gel. On the filter paper moistened with water at the bottom, the potassium chloride (KCl) particles in contact with it will dissolve to form a potassium chloride solution. At the same time, due to the chemical potential difference, water and potassium chloride (KCl) particles will migrate to a certain extent. Specifically, for water, the chemical potential of pure water is higher than that of water in potassium chloride solution, so water will overcome the effect of gravity and continue to migrate upward from the filter paper to the silica gel to dissolve potassium chloride (KCl) particles. At the same time, because the heated water will evaporate, this is also conducive to the upward migration of water to a certain extent. For potassium chloride, the chemical potential of pure potassium chloride is higher than that of potassium chloride in potassium chloride solution, but because the migration ability of potassium chloride is not as good as that of water in potassium chloride solution, water will continue to migrate upward. In the process of continuous migration, the potassium chloride solution at the bottom gradually loses water, which causes potassium chloride to gradually form smaller crystals and precipitate out, thus forming an uneven microporous structure with large top and small bottom.

[0062] A third aspect of the present invention provides an application of the aforementioned flexible sensor in a flexible strain sensor, wherein the flexible strain sensor includes a simulated human skin in the field of medical health monitoring.

[0063] In the present invention, the flexible sensor is applied to simulate human skin, and can be used to monitor pulse, recognize facial micro-expressions, recognize human voice, etc. by analyzing the sensor electrical signal.

[0064] The present invention will be described in detail below through examples.

[0065] The raw materials and equipment used in the present invention are all commercially available products.

[0066] Example 1

[0067] This embodiment is intended to illustrate the flexible sensor prepared by the present invention.

[0068] (1) Platinum silica gel Ecoflex T10 and potassium chloride (KCl) are uniformly mixed in a mass ratio of 1:3, specifically 4.02 g of platinum silica gel Ecoflex T10 (specific components are shown in Table 1) and 12.03 g of potassium chloride (KCl).

[0069] (2) The solid obtained above was cured in a polytetrafluoroethylene (PTFE) mold at 90°C for 2 hours. The mold had a size of 50×35×5 mm. A filter paper moistened with 0.5 mL of deionized water was placed on the bottom of the mold in advance, so that a non-uniform microporous structure could be constructed using chemical potential.

[0070] (3) Etching was then performed using hot water at 90° C. for 20 hours to remove potassium chloride (KCl) in the solid obtained above, thereby obtaining a silica gel matrix having a non-uniform microporous structure.

[0071] (4) Then, 90 mg of graphene is dispersed in the porous silica gel matrix obtained above by filtration, and the evenly dispersed silica gel matrix is ​​placed in a vacuum drying oven and dried at a temperature of 50° C. for 48 hours. Finally, the dried silica gel matrix loaded with graphene is connected to a copper electrode to obtain a highly sensitive flexible sensor that can detect pressure, stretching, and bending.

[0072] Example 2

[0073] This embodiment is intended to illustrate the flexible sensor prepared by the present invention.

[0074] (1) Platinum silica gel Ecoflex T10 and potassium chloride (KCl) were uniformly mixed in a mass ratio of 1:2, specifically 5.02 g of platinum silica gel Ecoflex T10 (specific components are shown in Table 1) and 10.02 g of potassium chloride (KCl).

[0075] (2) The solid obtained above was cured in a polytetrafluoroethylene (PTFE) mold at 90°C for 3 hours. The mold had a size of 50×35×5 mm. Filter paper moistened with 0.3 mL of deionized water was placed on the bottom of the mold in advance, so that a non-uniform microporous structure could be constructed using chemical potential.

[0076] (3) Etching was then performed using hot water at 80° C. for 12 hours to remove potassium chloride (KCl) from the solid obtained above, thereby obtaining a silica gel matrix having a non-uniform microporous structure.

[0077] (4) Then, 150 mg of graphene is dispersed in the porous silica gel matrix obtained above by suction filtration, and the evenly dispersed silica gel matrix is ​​placed in a vacuum drying oven and dried at a temperature of 50° C. for 48 hours. Finally, the dried silica gel matrix loaded with graphene is connected to a copper electrode to obtain a highly sensitive flexible sensor that can detect pressure, stretching, and bending.

[0078] Figure 3 This is a scanning electron microscope photograph of the middle cross section of the silica gel substrate prepared in Example 2 of the present invention. Figure 3 It can be seen that the middle cross-section of the silica gel matrix shows relatively uniform, interconnected cubic holes under a scanning electron microscope, with a size roughly between 300-400 μm, which is consistent with the original size of potassium chloride (KCl) particles.

[0079] Figure 4 This is a scanning electron microscope photograph of the upper part of the longitudinal section of the silica gel substrate prepared in Example 2 of the present invention. Figure 4 It can be seen that under a scanning electron microscope, the upper part of the longitudinal section of the silicone matrix is ​​a continuous, delicate and uniform structure with a certain mechanical strength, which plays a role in protection and mechanical support, which is similar to the epidermal tissue in human skin tissue.

[0080] Figure 5 This is a scanning electron microscope photograph of the lower part of the longitudinal section of the silica gel substrate prepared in Example 2 of the present invention. Figure 5 It can be seen that under a scanning electron microscope, the pore size distribution of the lower part of the longitudinal section of the silicone matrix is ​​uneven, with sparse larger pores of 300-400μm on the top and gradually transitioning to fine and smaller pores of about 100μm on the bottom. This uneven microporous structure is similar to the dermis in human skin tissue.

[0081] Figure 6 This is a scanning electron microscope photo of the undispersed graphene on the silica gel matrix prepared in Example 2 of the present invention. Figure 6 It can be seen that under a scanning electron microscope, the surface of the silica gel matrix without dispersed graphene is smooth, different pores are interconnected, and there are relatively few defects, indicating that the etching is relatively sufficient.

[0082] Figure 7 and Figure 8 All are scanning electron microscope photos of the silica gel matrix prepared in Example 2 of the present invention after graphene is dispersed by suction filtration. Figure 7 and Figure 8It can be seen from the scanning electron microscope photograph after the graphene is dispersed in the silica gel matrix by suction filtration that the graphene is evenly dispersed and the dispersion amount is also large, basically forming a connected conductive network.

[0083] Fig. 9 This is a cross-sectional scanning electron microscope photograph of the graphene inserted into the silica gel matrix after the graphene is dispersed by suction filtration in the silica gel matrix prepared in Example 2 of the present invention. Fig. 9 It can be seen from the cross-sectional scanning electron microscope photo of the silicone matrix after ultrasonic dispersion of graphene that the graphene is inserted into the silicone matrix, forming a relatively strong adhesion. Therefore, the stability of the flexible sensor can be maintained during use.

[0084] Fig.10 This is the pressure sensitivity curve of the flexible sensor prepared in Example 2 of the present invention. Fig.10 It can be seen that the vertical coordinate ΔI / I0 and the horizontal coordinate pressure (Pressure) of the flexible sensor are linearly related in the pressure range of 0-100 kPa, and its slope S can represent the sensitivity, which is 1.12×10 5 kPa -1 It remains unchanged and shows high sensitivity, which shows the potential of this flexible sensor to be used in many occasions, such as in the field of medical care, where physiological signals can be monitored in real time.

[0085] Fig.11 This is the tensile sensitivity curve of the flexible sensor prepared in Example 2 of the present invention. Fig.11 It can be seen that under the stretching of 0-210%, the ΔI / I0 of the flexible sensor decreases from 150k to 35k, and the ΔI / I0 and the tensile strain data points are basically near a straight line, which can be shown to have a relatively good linear relationship, indicating that the flexible sensor can also be used to detect tensile strain.

[0086] Fig.12 This is the bending sensitivity curve of the flexible sensor prepared in Example 2 of the present invention. Fig.12 It can be seen that the flexible sensor has obvious detection effect on different bending effects. The horizontal axis is the bending curvature diameter (Diameter) that characterizes the degree of bending, and its value increases from 1cm to 30cm. The vertical axis is resistance. The resistance value of the sensor is linearly related to the change of the curvature diameter of the bending degree. The curvature diameter of 1-30cm can be fully applied to most scenarios in real life.

[0087] Fig.13 The sensitivity curve of the flexible sensor prepared in Example 2 of the present invention after three consecutive compressions is shown in FIG. Fig.13It can be seen that the sensitivity curves of the prepared flexible sensor have good coincidence in three consecutive high-pressure (0-300kPa) compression tests, which indicates that the flexible sensor has good stability in use.

[0088] Embodiment 3-4

[0089] This embodiment is intended to illustrate the flexible sensor prepared by the present invention.

[0090] The flexible sensor was prepared in the same manner as in Example 1, except that the amounts of the raw materials platinum silica gel Ecoflex T10 (specific components are shown in Table 1) and potassium chloride (KCl), the curing temperature and time, the hot water etching temperature and time, the amount of deionized water used to wet the filter paper at the bottom of the mold, and the amount of graphene dispersed in the porous silica gel matrix were different, as shown in Table 1.

[0091] Comparative Example 1-2

[0092] The flexible sensor was prepared in the same manner as in Example 1, except that the amounts of the raw materials platinum silica gel Ecoflex T10 (specific components are shown in Table 1) and potassium chloride (KCl), the curing temperature and time, the hot water etching temperature and time, the amount of deionized water used to wet the filter paper at the bottom of the mold, and the amount of graphene dispersed in the porous silica gel matrix were different, as shown in Table 1.

[0093] Table 1

[0094]

[0095]

[0096] Note: "Platinum silicone Ecoflex T10*" means that in the embodiments and comparative examples of the present invention, when the platinum silicone Ecoflex T10 is composed of agent A and agent B, the ratio of agent A to agent B is between 1: (0.9-1.1);

[0097] Wherein, agent A comprises vinyl-terminated dimethylsiloxane and / or polysiloxane, and alkyl platinum complex, and based on the total weight of agent A, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 90-99.9% by weight, and the content of alkyl platinum complex is 0.1-10% by weight;

[0098] Agent B includes vinyl-terminated dimethylsiloxane and / or polysiloxane, and methyl hydrogen silicone oil, and based on the total weight of agent B, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 60-80 weight %, and the content of methyl hydrogen silicone oil is 20-40 weight %.

[0099] Test Example 1

[0100] The same test method as in Example 2 was used to test the various properties of the examples and comparative examples. The results are shown in Table 2.

[0101] Table 2

[0102]

[0103]

[0104] It can be seen from Table 2 that the embodiment using the technical solution of the present invention has suitable large and small pore diameters. This uneven microporous structure is similar to the dermis in human skin tissue, and the sensitivity and other performances of the sensor are also relatively good.

[0105] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A flexible sensor, characterized in that: The flexible sensor includes a microporous structure and a conductive inorganic substance and an electrode loaded on the surface of the microporous structure, wherein the upper top layer and the lower bottom layer of the microporous structure are dense silica gel layers, the middle part of the microporous structure has a three-dimensional network structure interconnected with each other, and the porosity of the three-dimensional network structure gradually increases from top to bottom.

2. The flexible sensor according to claim 1, wherein: The porosity of the three-dimensional network structure gradually transitions from 0.1-5% to 30-60% from top to bottom; And / or, the pores in the three-dimensional network structure gradually decrease in diameter from top to bottom; Preferably, the pores in the three-dimensional network structure gradually change from 300-400 μm to 90-110 μm from top to bottom; More preferably, the pore diameter of the corresponding pores gradually transitions from 300-400 μm to 100-110 μm.

3. The flexible sensor according to claim 1, wherein: The material of the microporous structure is an elastomeric material; Preferably, the elastomeric material is silicone rubber; Preferably, the silicone rubber is platinum silicone Ecoflex T10; Preferably, the platinum silicone Ecoflex T10 comprises one or more of vinyl-terminated dimethylsiloxane, polysiloxane, alkyl platinum complex and methyl hydrogen silicone oil, preferably, the alkyl platinum complex is platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane; More preferably, the platinum silicone Ecoflex T10 includes agent A and / or agent B; And / or, when the platinum silicone Ecoflex T10 is composed of agent A and agent B, the ratio of agent A to agent B is 1:(0.9-1.1); Wherein, agent A comprises vinyl-terminated dimethylsiloxane and / or polysiloxane, and alkyl platinum complex, and based on the total weight of agent A, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 90-99.9% by weight, and the content of alkyl platinum complex is 0.1-10% by weight; agent B comprises vinyl-terminated dimethylsiloxane and / or polysiloxane, and methyl hydrogen silicone oil, and based on the total weight of agent B, the content of vinyl-terminated dimethylsiloxane and / or polysiloxane is 60-80% by weight, and the content of methyl hydrogen silicone oil is 20-40% by weight.

4. The flexible sensor according to any one of claims 1 to 3, wherein: Based on the total weight of the flexible sensor, the loading amount of the conductive inorganic substance is ≥ 0.8 wt %, preferably 2-12 wt %; Preferably, the conductive inorganic substance is graphene.

5. A method for preparing a flexible sensor according to any one of claims 1 to 4, characterized in that: The preparation method comprises: (1) mixing an elastomeric material with an inorganic salt to obtain a mixture; (2) curing the mixture in a mold to construct a non-uniform microporous structure using chemical potential; (3) etching the uneven microporous structure with hot water to remove inorganic salts, thereby obtaining a silica gel matrix containing an uneven microporous structure; (4) dispersing the conductive inorganic substance in the silica gel matrix by suction filtration to obtain a silica gel matrix loaded with the conductive inorganic substance; (5) Drying the silica gel substrate loaded with the conductive inorganic substance and connecting electrodes to obtain a flexible sensor.

6. The preparation method according to claim 5, wherein: The inorganic salt includes one or more of potassium chloride, sodium chloride, sodium sulfate and potassium sulfate.

7. The preparation method according to claim 5, wherein: The weight ratio of the elastomer material to the inorganic salt is 1:(1-4).

8. The preparation method according to claim 5, wherein: The material of the mold is polytetrafluoroethylene; And / or, the bottom of the mold is attached with filter paper moistened with 0.3-1 mL of deionized water.

9. The preparation method according to claim 5, wherein: The curing conditions include: a temperature of 60-100° C. and a curing time of 2-4 hours.

10. The preparation method according to claim 5, wherein: The hot water etching conditions include: the temperature of the hot water is 60-90° C., and the etching time is 12-24 hours.

11. The preparation method according to claim 5, wherein: Relative to 2-8 g of the silica gel matrix, the amount of the conductive inorganic substance used is 60-240 mg.

12. Application of the flexible sensor according to any one of claims 1 to 4 in a flexible strain sensor, characterized in that: The flexible strain sensor includes a simulated human skin in the field of medical health monitoring.

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