Flexible sensor structure and preparation method thereof

Abstract

The invention relates to the technical field of flexible sensor structures, in particular to a flexible sensor structure and a preparation method thereof.The flexible sensor structure comprises a flexible substrate, a bottom electrode layer, a middle composite structure, an upper electrode layer and a transparent protective film which are arranged from bottom to top; wherein the middle composite structure comprises at least one surface of a microstructure which is made of a metal wire mesh template and can generate deformation, the interior or the surface of the middle composite structure contains a photosensitive material, and the conductivity condition of the middle composite structure can change along with the change of pressure and illumination intensity. According to the flexible sensor, pressure and illumination measurement can be achieved, specific microstructure design and manufacturing can be achieved, the flexible sensor can be attached to the human skin surface or arranged in an intelligent mechanical arm, and the flexible sensor can be conveniently used for behavior detection and prediction of actions, postures, grabbing and the like in various occasions; the method can also play an important role in the fields of wearable equipment, medical health, robot touch, man-machine interaction systems and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor structure technology, and in particular to a flexible sensor structure and its fabrication method. Background Technology

[0002] Flexible sensors have broad application prospects in human-computer interaction systems, wearable devices, healthcare, and intelligent robots. With technological advancements, flexible sensors are currently developing towards greater intelligence, miniaturization, and multifunctionality, further meeting diverse market demands. Among these, composite flexible sensors for human bodies and intelligent robotic arms primarily focus on the integration of flexible pressure sensing and photoelectric sensing to detect gripping force (pressure) and the optical properties of object surfaces (such as color, texture, and reflectivity). This may involve different sensor structures, such as piezoresistive and capacitive flexible pressure sensors, and photoelectric sensors integrating photosensitive elements. Existing solutions mainly utilize heterogeneous integration (such as a piezoelectric layer + photosensitive layer) combined with noble metal electrodes (such as gold nanowires) and distributed fiber Bragg grating sensors. These solutions generally involve multiple complex processes, resulting in relatively high costs and making large-scale application difficult.

[0003] In the field of pressure sensing, recent years have seen a focus on constructing microstructures (such as micropillars, pores, or wrinkles) on the surfaces of polymers like PDMS and TPU to modulate interfacial contact behavior and stress distribution, becoming a core strategy for improving the sensitivity, response speed, and linear range of pressure sensors. To promote the application of flexible sensors, we propose a flexible sensor structure and its fabrication method. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a flexible sensor structure and its fabrication method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A flexible sensor structure includes, from bottom to top, a flexible substrate, a bottom electrode layer, an intermediate composite structure, an upper electrode layer, and a transparent protective film. The intermediate composite structure includes at least one deformable microstructure surface made of a metal mesh template. The interior or surface of the intermediate composite structure contains a photosensitive material. The conductivity of the intermediate composite structure changes with pressure and light intensity.

[0007] Preferably, when the intermediate composite structure includes a surface with a deformable microstructure, the surface is the lower end face of the intermediate composite structure.

[0008] Preferably, when the intermediate composite structure includes two surfaces with deformable microstructures, the surfaces are located on the two end faces or the inner side of the intermediate composite structure; when the surface with deformable microstructures is located on the inner side of the intermediate composite structure, the two surfaces are arranged facing each other and the microstructures cooperate with each other.

[0009] Preferably, a method for fabricating a flexible sensor structure includes the following steps:

[0010] Step 1, Prepolymer Preparation: The base polymer and curing agent are added to a stirrer at a mass ratio of 10:(1-1.6) and mixed thoroughly. The mixture is then placed in a vacuum oven to remove bubbles, thus obtaining the prepolymer.

[0011] Step 2, Fabrication of microstructures: The prepolymer is poured into a polytetrafluoroethylene tank, and a metal mesh template is placed so that the metal mesh template is located at the upper and / or lower end of the prepolymer. After the prepolymer has completely cured, the metal mesh template is peeled off to obtain a film with microstructures.

[0012] Step 3: Fabrication of conductive structure: The thin film with microstructure is cleaned sequentially with anhydrous ethanol and deionized water, dried after cleaning, and then the conductive structure is fabricated.

[0013] Step 4: Transfer the thin film with the conductive structure onto the flexible substrate, and attach the bottom electrode layer on the flexible substrate to the lower end face of the thin film;

[0014] Step 5: Spray a composite conductive material with photosensitive properties onto the upper surface of the thin film to obtain a photosensitive composite conductive layer. Then, attach the photosensitive composite conductive layer to a transparent protective film with an upper electrode layer to assemble a composite flexible sensor.

[0015] Preferably, the base polymer is one of PDMS, modified PDMS, TPU liquid, and nano-silver-doped PDMS.

[0016] Preferably, in step 1, hydrolyzable solid particles are doped into the base polymer. The solid particles are one of white sugar, sodium salt, glucose, and potassium salt, and the particle size of the solid particles is 30-400 micrometers.

[0017] Preferably, the mesh pattern in the wire mesh template is one of triangle, rectangle, square, circle, rhombus, hexagon and wavy, and the mesh count in the wire mesh template is 100-2000 mesh.

[0018] Preferably, in step 3, after drying, the upper and lower surfaces of the film with microstructure are subjected to oxygen plasma treatment for 30 seconds, a graphene-mixed conductive liquid is spin-coated onto the lower surface of the film using a spin coater, and then annealed in an oven at 95-105°C for 15-30 minutes.

[0019] Preferably, in step 3, the obtained microstructured film is first soaked in deionized water for 24-36 hours to completely dissolve the solid particles, then taken out and washed and dried; after drying, it is immersed in a graphene mixed conductive liquid, taken out after 1.5-3 hours, and placed in an oven at 95-105℃ for annealing for 1-2 hours.

[0020] Preferably, a flexible sensor structure is used in wearable devices, medical devices, and robotic grippers.

[0021] The beneficial effects of this invention are:

[0022] 1. A flexible sensor structure, wherein the intermediate composite structure comprises a specific microstructure capable of deformation and a low-dimensional material with specific wavelength photosensitive properties, and the conductivity of the intermediate composite structure changes with specific pressure and light.

[0023] 2. A method for fabricating a flexible sensor, using metal meshes with different pore sizes and mesh structures as templates, and different surface microstructures can be fabricated on PDMS by changing the mesh count and placement of the metal meshes; combining different metal meshes can effectively improve the sensitivity of the sensor and broaden its dynamic range; combining graphene mixed conductive liquid (photosensitive composite material) with a thin film with microstructures by solution coating (such as spin coating, spray coating, inkjet printing) not only has strong process compatibility, but also enables the composite sensor to simultaneously sense pressure (or tactile, physiological signals) and light signals (signal light, ambient light, human body radiation, blood oxygen-related light absorption).

[0024] 3. The flexible sensor involved in this invention can not only measure pressure and light, but its manufacturing process is also relatively simple. Specific microstructure design and manufacturing can be achieved through low-cost metal wire mesh. It can be attached to the human body surface or built into intelligent robotic hands, making it convenient for detecting and predicting behaviors such as actions, postures, and grasping in various situations. It can also play an important role in wearable devices, medical health, robotic tactile sensing, human-computer interaction systems and other fields, and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the composite sensor structure of Example 1 proposed in this invention;

[0026] Figure 2 This is a schematic diagram of the composite sensor structure of Example 2 proposed in this invention;

[0027] Figure 3 This is a schematic diagram of the composite sensor structure of Example 3 proposed in this invention;

[0028] Figure 4This is a schematic diagram of the composite sensor structure of Example 4 proposed in this invention;

[0029] Figure 5 This is a schematic diagram of the composite sensor structure of Example 5 proposed in this invention;

[0030] Figure 6 The structure of the metal mesh template under a microscope in Example 1 (20x lens).

[0031] Figure 7 The PDMS surface structure prepared under a microscope based on a metal mesh template in Example 1 (20x lens).

[0032] Figure 8 The structure of the metal mesh template under a microscope in Example 3 (20x lens).

[0033] Figure 9 The PDMS surface structure prepared under a microscope based on a metal mesh template in Example 1 (20x lens).

[0034] Figure 10 Example 3 shows the current-time response of a resistive flexible composite sensor: (a) under low pressure, (b) under high pressure;

[0035] Figure 11 Example 3 shows the current-time response of a resistive flexible composite sensor under illumination of different power levels. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] A flexible sensor structure is characterized by comprising, from bottom to top, a flexible substrate, a bottom electrode layer, an intermediate composite structure, an upper electrode layer, and a transparent protective film, wherein the intermediate composite structure includes at least one surface with a deformable microstructure, the interior or surface of the intermediate composite structure contains a photosensitive material, and the conductivity of the intermediate composite structure changes with pressure and light intensity.

[0040] Reference Figure 1 , Figure 6 and Figure 7 In Example 1,

[0041] A method for fabricating a resistive flexible sensor, the method comprising the following steps:

[0042] Step 1: Mix the PDMS base polymer and curing agent in a 10:1 ratio to form a prepolymer, stir thoroughly, and then place it in a vacuum oven to remove bubbles;

[0043] Step 2: Lay the metal wire mesh template I with a specific structure in the square groove (the mesh pattern is square and the mesh count is 200), and then spray a layer of release agent; heat at 65℃ for 1-2 hours, and let stand at room temperature for 24 hours;

[0044] Step 3: Pour the PDMS with the metal mesh template out of the square glass tank and manually peel off the metal mesh template I; clean and dry the PDMS surface I with the metal mesh-like structure using anhydrous ethanol and deionized water respectively.

[0045] Step 4: After treating the microstructured surface I and the flat surface II without microstructure of PDMS with oxygen plasma for 30 seconds, spin-coating the composite conductive liquid with photosensitive properties onto the PDMS surface I using a spin coater, and then annealing it in an oven at 100°C for 20 minutes.

[0046] Step 5: Transfer the PDMS with the conductive layer onto a flexible substrate with an interdigitated electrode pattern, with the conductive layer corresponding to the electrode area of ​​the flexible substrate, to complete the initial bonding.

[0047] Step 6: Spray a composite conductive material with photosensitive properties onto PDMS surface II, then dry it on a 60°C heating table. Finally, attach a transparent organic film with an electrode layer onto the PDMS surface II with the photosensitive composite material to form a composite flexible sensor.

[0048] Figure 6 and Figure 7 The metal mesh template under a microscope and the PDMS surface structure prepared based on the metal mesh template (20x lens).

[0049] Reference Figure 2 In Example 2,

[0050] A method for fabricating a resistive flexible sensor, the method comprising the following steps:

[0051] Step 1: Lay the metal wire mesh template I with a specific structure in the square groove, and then spray a layer of release agent; pour TPU adhesive onto the metal wire mesh template I (mesh count of 2000 mesh), and let it stand at room temperature for 30 minutes;

[0052] Step 2: Then place another metal wire mesh template II (with a square mesh pattern and a mesh count of 300) on top of the PDMS, apply a certain pressure (10-20N), and heat at 60℃ for 20 minutes to cure.

[0053] Step 3: Pour the TPU with the metal mesh template out of the square glass tank, and manually peel off the metal mesh templates I and II; clean and dry the PDMS surface I with a similar structure to the metal mesh using anhydrous ethanol and deionized water respectively.

[0054] Step 4: After treating TPU microstructure surfaces I and II with oxygen plasma for 30 seconds, spin coat a photosensitive composite conductive material onto TPU surface I using a spin coater, and then anneal in an oven at 100°C for 20 minutes; (Alternatively, a photosensitive mixed conductive liquid can be sprayed onto both PDMS surfaces I and II).

[0055] Step 5: Transfer the TPU with the conductive layer onto a flexible substrate with a dual-electrode pattern, with the conductive layer corresponding to the electrode area of ​​the flexible substrate, to complete the initial bonding.

[0056] Step 6: Spray a photosensitive composite conductive material (such as graphene composite material) onto TPU surface II, then dry it on a 50°C heating table. Finally, attach a transparent organic film with an electrode layer onto PDMS surface II with photosensitive composite material to form a composite flexible sensor.

[0057] Reference Figure 3 , Figure 8and Figure 9 In Example 3,

[0058] A method for fabricating a resistive flexible sensor, the method comprising the following steps:

[0059] Step 1, Solution preparation: Mix the carboxyl-terminated PDMS base polymer and curing agent in a 7:1 ratio to prepare a prepolymer, stir thoroughly, and then place it in a vacuum oven to remove bubbles;

[0060] Step 2: Lay the metal wire mesh template I with a specific structure in the square groove, and then spray a layer of release agent; pour the PDMS solution onto the metal wire mesh template I (the mesh pattern is circular and the mesh count is 2000 mesh), and heat it at 60℃ for 1-2 hours. Then place another metal wire mesh template II (the mesh pattern is square and the mesh count is 300 mesh) on top of the PDMS and apply a certain pressure (10-20N). Let it stand at room temperature for 24 hours.

[0061] Step 3: Pour the PDMS with the metal mesh template out of the square glass tank, and manually peel off the metal mesh templates I and II; clean and dry the PDMS surface I with the metal mesh-like structure using anhydrous ethanol and deionized water respectively.

[0062] Step 4: After subjecting the microstructured surfaces I and II of PDMS to oxygen plasma treatment for 30 seconds, spin-coat PEDOT:PSS:Ti3C2T onto PDMS surface I using a spin coater. X A ZnO mixed conductive liquid (mass ratio approximately 5:2:1) is then annealed in an oven at 100°C for 30 minutes; then, graphene conductive liquid is sprayed onto PDMS surface II; (alternatively, a mixed conductive liquid with photosensitive properties can be sprayed onto both PDMS surfaces I and II).

[0063] Step 5: Transfer the PDMS with the conductive layer onto a flexible substrate with a dual-electrode pattern, where the conductive layer on the PDMS surface I corresponds to the electrode area of ​​the flexible substrate, thus completing the initial bonding.

[0064] Step 6: Finally, attach the transparent organic film with the electrode layer to the PDMS surface II with photosensitive composite material to form a composite flexible sensor.

[0065] Figure 8 and Figure 9 The metal mesh template under a microscope and the PDMS surface structure prepared based on the metal mesh template (20x lens).

[0066] Figure 10-11 middle, Figure 10The current-time response of the resistive flexible composite sensor: (a) detection under low pressure and (b) detection under high pressure; Figure 11 Current-time response diagram of resistive flexible composite sensor under illumination.

[0067] Reference Figure 4 In Example 4,

[0068] A method for fabricating a resistive flexible sensor, the method comprising the following steps:

[0069] Step 1: Mix the PDMS base polymer and curing agent in a 10:1 ratio to prepare a prepolymer; (Alternatively, modified PDMS, such as hydroxyl-terminated PDMS or epoxy-modified PDMS, can be selected).

[0070] Step 2: Dope hydrolyzable solid particles (such as white sugar, salt, glucose, etc.) of a certain particle size into the PDMDS prepolymer, stir thoroughly, and then place it in a vacuum oven to remove bubbles;

[0071] Step 3: Lay the metal wire mesh template I with a specific structure in the square groove, and then spray a layer of release agent; pour the mixed solution onto the metal wire mesh template I (the mesh pattern is circular and the mesh count is 900 mesh), and heat it at 60℃ for 2-4 hours. Then place another metal wire mesh template III (the mesh pattern is triangular and the mesh count is 2000 mesh) on top of the semi-cured PDMS, apply a certain pressure, and then let it stand at room temperature for 24 hours.

[0072] Step 4: Remove the upper metal mesh template III, then pour the PDMS / metal mesh template out of the square glass tank, and manually peel off the metal mesh template I;

[0073] Step 5: Soak the obtained PDMS containing solid particles in deionized water for 24-36 hours to completely dissolve the solid particles (such as white sugar, salt, glucose, etc.). After taking it out, use anhydrous ethanol to clean and dry the PDMS with porous structure.

[0074] Step 6: Immerse PDMS with internal porous structure and surface microstructure in graphene-mixed conductive liquid, remove after 2 hours, and anneal in an oven at 100℃ for 1 hour; (multiple immersions are possible, and composite conductive liquid materials with various photosensitive properties can be selected).

[0075] Step 7: Transfer the PDMS film containing conductive material to a flexible substrate with interdigitated electrode layers, and attach another organic layer with electrode patterns on top of the PDMS to form a flexible sensor based on the PDMS intermediate composite layer.

[0076] Reference Figure 5In Example 5,

[0077] A method for fabricating a capacitive flexible sensor, the method comprising the following steps:

[0078] Step 1: Mix the PDMS base polymer and curing agent at a ratio of 10:1 to form a prepolymer, stir thoroughly, and then place it in a vacuum oven to remove bubbles; (Alternatively, carboxyl-terminated PDMS can be selected, and the PDMS and curing agent can be mixed at a ratio of 6.5:1 or 8:1)

[0079] Step 2: Lay the wire mesh templates I and II with specific structures parallel to each other in a square PTFE tank, and then spray a layer of release agent; pour the PDMS solution onto the wire mesh templates I and II, and heat at 65°C for 1-2 hours, then let it stand at room temperature for 24 hours; (Alternatively, you can directly pour the PDMS solution into the square PTFE tank, heat at 65°C for 2-4 hours, then lay the square wire mesh templates I and II flat on the semi-cured PDMS, apply a certain pressure, and let it stand at room temperature for 24 hours)

[0080] Step 3: Pour the PDMS / metal mesh template out of the square glass tank and manually peel off the metal mesh templates I and II; clean and dry the PDMS surfaces I and II, which have a similar structure to the metal mesh, using anhydrous ethanol and deionized water.

[0081] Step 4: Cut PDMS with surface I and surface II at the boundary between the two surfaces to obtain PDMS-A and PDMS-B, and perform oxygen plasma treatment on each for 30 seconds.

[0082] Step 5: Spray a graphene composite solution with photosensitive properties onto the back side of PDMS-B with surface II, and dry it on an 80°C heating table; (Alternatively, you can spray graphene composite solution onto both surface II and the back side of PDMS-B)

[0083] Step 6: Transfer PDMS-A with surface I to a flexible substrate with an electrode layer, with surface I facing upwards; the side of PDMS-B without surface structure corresponds to the electrode of the flexible substrate to complete the initial bonding.

[0084] Step 7: Combine the surface II of the PDMS-B with the electrode layer that is attached to the flexible substrate electrode with the surface I of the PDMS-A mentioned above to form a composite flexible sensor.

[0085] The composite flexible sensor was characterized under different pressures, different illuminations, and different pressures under illumination. Then, the composite flexible sensor was attached to specific parts of the human body or a robotic gripper, and related application tests could be achieved by combining it with a specific linear simulator. Figure 10As shown.

[0086] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flexible sensor structure, characterized in that, It includes a flexible substrate, a bottom electrode layer, an intermediate composite structure, an upper electrode layer, and a transparent protective film arranged from bottom to top. The intermediate composite structure contains at least one deformable microstructure surface made of a metal mesh template. The interior or surface of the intermediate composite structure contains photosensitive material. The electrical conductivity of the intermediate composite structure changes with pressure and light intensity.

2. The flexible sensor structure according to claim 1, characterized in that, When the intermediate composite structure includes a surface with a deformable microstructure, that surface is the lower end face of the intermediate composite structure.

3. The flexible sensor structure according to claim 1, characterized in that, When the intermediate composite structure contains two surfaces with deformable microstructures, the surfaces are located on the two end faces or inside the intermediate composite structure; when the surface with deformable microstructures is located inside the intermediate composite structure, the two surfaces are arranged facing each other and the microstructures cooperate with each other.

4. A method for fabricating a flexible sensor structure according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1, Prepolymer Preparation: Add the base polymer and curing agent to a stirrer at a mass ratio of 10:(1-1.6) and mix thoroughly. Place the mixture in a vacuum oven at room temperature and with a vacuum degree ≤1 Torr to remove bubbles and obtain the prepolymer. Step 2, Fabrication of microstructures: The prepolymer is poured into a polytetrafluoroethylene tank, and a metal mesh template is placed so that the metal mesh template is located at the upper and / or lower end of the prepolymer. After the prepolymer has completely cured, the metal mesh template is peeled off to obtain a film with microstructures. Step 3: Fabrication of conductive structure: The thin film with microstructure is cleaned sequentially with anhydrous ethanol and deionized water, dried after cleaning, and then the conductive structure is fabricated. Step 4: Transfer the thin film with the conductive structure onto the flexible substrate, and attach the bottom electrode layer on the flexible substrate to the lower end face of the thin film; Step 5: Spray a composite conductive material with photosensitive properties onto the upper surface of the thin film to obtain a photosensitive composite conductive layer. Then, attach the photosensitive composite conductive layer to a transparent protective film with an upper electrode layer to assemble a composite flexible sensor.

5. The method for fabricating a flexible sensor structure according to claim 4, characterized in that, The base polymer is one of PDMS, hydroxyl-terminated PDMS, aqueous thermoplastic polyurethane liquid, and silver-doped nanoparticles, wherein the PDMS has a molecular weight of 22,000-27,000 and a viscosity of 3,000-4,000 mPa·s, the hydroxyl-terminated PDMS has a molecular weight of 22,000-27,000 and a viscosity of 1,000-2,000 mPa·s, and the silver-doped nanoparticles contain 3%-5% by mass of silver. The photosensitive composite conductive material is conductive graphene / nano-ZnO, PEDOT:PSS / few-layer MoS2 / nano-silver, or PEDOT:PSS / monolayer Ti3C2T. X One or two of the nano-ZnO, wherein the mass ratio of PEDOT:PSS, few-layer MoS2 and nano-silver is 10:1:1, and the mass ratio of PEDOT:PSS and monolayer Ti3C2T is... X And the mass ratio of nano-silver is (6-10):4:

1.

6. The method for fabricating a flexible sensor structure according to claim 5, characterized in that, In step 1, hydrolyzable solid particles are doped into the base polymer. The solid particles are one of white sugar, sodium salt, glucose and potassium salt, and the particle size of the solid particles is 30-400 micrometers.

7. The method for fabricating a flexible sensor structure according to claim 4, characterized in that, The mesh pattern in the metal wire mesh template is one of triangle, rectangle, square, circle, rhombus, hexagon and wave. The mesh count in the metal wire mesh template is 100-2000 mesh, the thickness of the metal wire mesh is 0.05-3mm, and the microstructure shape of the PDMS surface complements the mesh pattern of the metal wire mesh.

8. The method for fabricating a flexible sensor structure according to claim 4, characterized in that, In step 3, after drying, the upper and lower surfaces of the film with microstructure are subjected to oxygen plasma treatment for 30 seconds respectively. Then, graphene mixed conductive liquid or PEDOT:PSS conductive ink is spin-coated or directly sprayed onto the lower surface of the film using a spin coater. Finally, the film is annealed in an oven at 95-105℃ for 15-30 minutes.

9. The method for fabricating a flexible sensor structure according to claim 6, characterized in that, In step 3, the obtained microstructured film is first soaked in deionized water for 24-36 hours to completely dissolve the solid particles. After being taken out, it is washed and dried. After drying, it is immersed in a graphene mixed conductive liquid. After 1.5-3 hours, it is taken out and placed in an oven at 95-105℃ for annealing for 1-2 hours.

10. The application of a flexible sensor structure according to any one of claims 1-3 in wearable devices, medical devices, and robotic grippers.

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