Flexible micro tenon-and-mortise structure tactile sensor

Abstract

A flexible touch sensor with a micro tenon-and-mortise structure comprises an upper flexible sensing substrate, a lower flexible sensing substrate, an interdigital electrode and a flexible bottom film. The interdigital electrode comprises a single-face conductive finger electrode and a double-face conductive finger electrode, the lower surface of the single-face conductive finger electrode is conductive, and the upper surface of the single-face conductive finger electrode is non-conductive. The flexibility of the upper flexible sensing substrate is higher than that of the lower flexible sensing substrate, the lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate are respectively provided with convex and concave microstructures with the same characteristic size, and the surfaces of the microstructures are respectively provided with a conductive film layer. The upper surface of the interdigital electrode is in contact with the lower surface of the upper flexible sensing substrate, the lower surface of the interdigital electrode is adhered to the upper surface of the lower flexible sensing substrate, and a gap is formed between the upper flexible sensing substrate and the lower flexible sensing substrate due to the thickness of the interdigital electrode. The invention has the advantages of high sensitivity, low detection limit and multi-mode signal response monitoring capability, and belongs to the technical field of flexible sensing.

Description

Technical Field

[0001] The invention relates to flexible sensing technology, and in particular to a flexible micro-mortise and tenon structure tactile sensor. Background Art

[0002] With the continuous development of science and technology, tactile sensors that mimic the sensing ability of human skin have been widely used in electronic skin, biomedical prostheses, human-machine interfaces, etc. An ideal tactile sensor can distinguish various external stimuli, such as pressure, shear force, torsion, vibration, and temperature, and can also detect their intensity. For example, in robots or prostheses, it is important to identify the magnitude of mechanical force. When in contact with an object, specific operations such as grasping control and object manipulation can be achieved by distinguishing and detecting multiple mechanical stimuli.

[0003] In order to achieve tactile perception of human activities or movements, tactile sensors must measure several relevant parameters, such as sensitivity, working range, response time, and hysteresis. Previously, there have been reports on the use of sensors with different materials and structures to detect and distinguish the perception of multiple mechanical stimuli, but these sensors have low sensitivity to external mechanical stimuli and are limited in the types and sizes of mechanical stimuli that can be detected. In order to improve the performance of tactile sensors, new tactile sensors need to be designed. Summary of the invention

[0004] In view of the technical problems existing in the prior art, the object of the present invention is to provide a flexible micro-mortise and tenon structure tactile sensor with high sensitivity, low detection limit and multi-modal signal response monitoring capability.

[0005] In order to achieve the above object, the present invention adopts the following technical solution.

[0006] A flexible micro-mortise and tenon structure tactile sensor comprises an upper flexible sensing substrate, a lower flexible sensing substrate, interdigitated electrodes and a flexible bottom film. The interdigitated electrodes comprise a single-sided conductive finger electrode and a double-sided conductive finger electrode, wherein the lower surface of the single-sided conductive finger electrode is conductive and the upper surface is non-conductive. The upper flexible sensing substrate is more flexible than the lower flexible sensing substrate, and the lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate are respectively provided with convex and concave microstructures of the same characteristic size, and a conductive film layer is provided on the surface of the microstructures. The upper surface of the interdigitated electrodes contacts the lower surface of the upper flexible sensing substrate, and the lower surface of the interdigitated electrodes adheres to the upper surface of the lower flexible sensing substrate. The thickness of the interdigitated electrodes forms a gap between the upper flexible sensing substrate and the lower flexible sensing substrate at the inter-finger position. The flexible bottom film is tightly attached to the lower surface of the lower flexible sensing substrate.

[0007] As a preferred embodiment, the convex and concave microstructure features are in the shape of a pyramid, a cone, a hemisphere, a truncated cone or a wave, and the surface of the microstructure has a submicron-level wrinkled secondary structure.

[0008] As a preference, the upper flexible sensing substrate and the lower flexible sensing substrate are flexible polymer substrates with conductive surfaces but different softness, and the conductivity thereof is obtained through chemical oxidation, ion sputtering, deposition or spraying processes.

[0009] As a preferred embodiment, the flexible polymer substrate is prepared by injection compression molding, compression molding, roll molding, spin coating curing or UV curing, and the flexible polymer material is a thermoplastic elastomer, ethylene-octene copolymer, polydimethylsiloxane, silicone rubber or photosensitive resin.

[0010] As a preference, the thickness of the interdigital electrodes is 0.05-0.2 mm, and the material is copper foil, aluminum foil or conductive adhesive.

[0011] As a preference, the material of the flexible base film is a flexible heat-resistant and corrosion-resistant film, preferably, the material is polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE) or polypropylene (PP).

[0012] As a preferred embodiment, the flexible micro-mortise and tenon structure tactile sensor has high sensitivity, low detection limit and multi-modal signal response monitoring capability.

[0013] The working principle of the flexible micro-mortise and tenon structure tactile sensor of the present invention is as follows. When the flexible micro-mortise and tenon structure tactile sensor is not subjected to force, the upper surface of the single-sided conductive finger-shaped electrode contacts the lower surface of the upper flexible sensing substrate but is insulated from each other, and the upper flexible sensing substrate and the lower flexible sensing substrate do not form a conductive path in the inter-finger region. At this time, after the interdigital electrodes are energized, the charge only flows through the lower flexible sensing substrate.

[0014] When the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of normal force in the inter-finger area, the upper flexible sensing substrate bends and deforms, and a part of its lower surface comes into contact with the upper surface of the lower flexible sensing substrate; at the same time, in the contact area, the raised microstructures and recessed microstructures respectively arranged on the lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate form interlocking micro-mortise and tenon structures, and the wrinkled secondary structures on the microstructures are in contact with each other; as the normal force increases, the contact areas of the upper and lower flexible sensing substrates expand, the number of interlocking micro-mortise and tenon structures increases, and at the same time the wrinkled secondary structures undergo micro-deformation, which increases the contact area, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor.

[0015] When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of tangential force under the pre-normal force, the microstructure surface facing the direction of the tangential force in the micro-mortise and tenon structure is subjected to greater pressure than other microstructure surfaces, and the wrinkle secondary structure on the compressed positive micro-pyramid cone surface undergoes micro-deformation, and the contact area increases with the increase of the tangential force, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the tangential force is greater than the static friction force, unstable slip occurs between the protruding microstructure and the recessed microstructure, and at this time the contact area between the two is reduced, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor is reduced.

[0016] When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of torsional torque under the pre-normal force, the microstructures in the micro-mortise and tenon structure will be compressed, the wrinkle secondary structure on the compressed microstructure surface will undergo micro-deformation, and the contact area will increase with the increase of torsional torque, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the torsional torque is greater than the static friction torque, unstable separation will occur between the protruding microstructure and the recessed microstructure, and the contact area between the two will decrease, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor will decrease.

[0017] The present invention has the following advantages over the prior art.

[0018] (1) The flexible micro-mortise and tenon structure tactile sensor in the present invention has high sensitivity, low detection limit and multi-modal signal response monitoring capability.

[0019] (2) The preparation process of the flexible sensor substrate in the present invention is simple and easy to operate. The equipment used is a continuous processing equipment (such as an injection molding machine) that is relatively common in industrial production. Therefore, continuous and batch preparation can be achieved, which is easy to promote in industry and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the packaging structure of the flexible micro-mortise and tenon structure tactile sensor of the present invention.

[0021] Figure 2a and Figure 2b They are scanning electron microscope photos of the lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate in the flexible micro-mortise and tenon structure tactile sensor of the present invention.

[0022] Figure 3a , Figure 3b , Figure 3c and Figure 3d It is a schematic diagram of the working principle of the flexible micro-mortise and tenon structure tactile sensor of the present invention.

[0023] Figure 4 is the relative resistance change (ΔR / R 0) with the change of normal force.

[0024] Figure 5 is the relative resistance change (ΔR / R) of the flexible micro-mortise and tenon structure tactile sensor under three pre-normal forces of the present invention. 0 ) with the change of tangential force.

[0025] Figure 6 is the relative resistance change (ΔR / R) of the flexible micro-mortise and tenon structure tactile sensor under different pre-normal forces. 0 ) with the change of torque.

[0026] Figure 7a and 7b These are the resistance curves of the flexible micro-mortise and tenon structure tactile sensor under 5N vector force as a function of polar angle and azimuth angle.

[0027] The symbols in the above figures are explained as follows: 1—upper flexible sensing substrate; 2—lower flexible sensing substrate; 3—interdigitated electrodes; 3.1—single-sided conductive finger electrodes; 3.2—double-sided conductive finger electrodes; 4—flexible bottom film. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] Figure 1 The packaging structure of the flexible micro-mortise and tenon structure tactile sensor of the present invention is shown. The flexible micro-mortise and tenon structure tactile sensor includes an upper flexible sensing substrate 1, a lower flexible sensing substrate 2, a forked electrode 3 and a flexible bottom film 4. The material of the forked electrode 3 is copper foil, and its thickness, number of electrode pairs, forked finger width and gap between adjacent forked fingers are 0.05mm, 3, 2mm and 4mm respectively, including a single-sided conductive finger electrode 3.1 and a double-sided conductive finger electrode 3.2, and the lower surface of the single-sided conductive finger electrode 3.1 is conductive while the upper surface is not conductive. The upper flexible sensing substrate 1 is more flexible than the lower flexible sensing substrate 2, and the lower surface of the upper flexible sensing substrate 1 and the upper surface of the lower flexible sensing substrate 2 are respectively provided with positive micro-pyramids ( Figure 2a ) and inverted micro-pyramids ( Figure 2b ), the height / depth and cone angle of the positive / inverted micro-pyramid are 50μm and 60° respectively, and both cones have conductive polypyrrole (PPy) films, and the cone surface of the positive micro-pyramid has a submicron-level wrinkled secondary structure (such as Figure 2aThe upper surface of the interdigital electrode 3 contacts the lower surface of the upper flexible sensing substrate 1, and the lower surface of the interdigital electrode 3 adheres to the upper surface of the lower flexible sensing substrate 2. The thickness of the interdigital electrode 3 forms a gap between the upper flexible sensing substrate 1 and the lower flexible sensing substrate 2 in the interdigital region. The flexible bottom film 4 is a PET film with a thickness of 0.1 mm, which is closely attached to the lower surface of the lower flexible sensing substrate 2.

[0030] The manufacturing process of the lower flexible sensing substrate 2 is as follows: first, a polyurethane elastomer (TPU) substrate (Shore hardness: 90A, size: 30mm×30mm×0.5mm) with inverted micro-pyramids on the surface is prepared by injection compression molding technology, and then a conductive PPy film layer with a thickness of about 15nm is deposited on the surface of the substrate with the inverted micro-pyramids, and the lower flexible sensing substrate 2 is obtained after washing and drying; the manufacturing process of the upper flexible sensing substrate 1 is as follows: first, a two-component commercial polydimethylsiloxane (PDMS) is mixed evenly and then spin-coated on the surface of the lower flexible sensing substrate 2 with the inverted micro-pyramids, and the PDMS is peeled off after being cured to obtain a PDMS substrate with a thickness of 0.5mm and a positive micro-pyramid on the surface (Shore hardness: 30A), and then a PPy film layer with a thickness of about 15nm is deposited on the surface of the substrate with the positive micro-pyramids. After washing and drying, the PPy film layer on the surface of the positive pyramid shrinks to obtain a submicron-level wrinkled secondary structure.

[0031] Figure 3a , Figure 3b , Figure 3c and Figure 3d The working principle of the flexible micro-mortise and tenon structure tactile sensor of the present invention is shown in FIG. 1 , where the arrows represent the direction of force application. When the flexible micro-mortise and tenon structure tactile sensor is not subjected to force (see FIG. 1 ), the tactile sensor is subjected to force. Figure 3a ), although the upper surface of the single-sided conductive finger electrode 3.1 is in contact with the lower surface of the upper flexible sensing substrate 1, they are insulated from each other, and no conductive path is formed between the upper flexible sensing substrate 1 and the lower flexible sensing substrate 2 in the inter-finger area. At this time, after the interdigitated electrode 3 is energized, the charge only flows through the lower flexible sensing substrate 2.

[0032] When the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of normal force in the inter-finger area (see Figure 3b ), the upper flexible sensing substrate 1 is bent and deformed, and a part of its lower surface comes into contact with the upper surface of the lower flexible sensing substrate 2; at the same time, in the contact area, the positive micro-pyramids and inverted micro-pyramids respectively arranged on the lower surface of the upper flexible sensing substrate 1 and the upper surface of the lower flexible sensing substrate 2 form an interlocking micro-mortise and tenon structure, and the wrinkle secondary structure on the cone surface of the positive micro-pyramid is in contact with the cone surface of the inverted micro-pyramid; with the increase of the normal force, the contact area of ​​the upper and lower flexible sensing substrates is expanded, the number of the interlocking micro-mortise and tenon structures increases, and at the same time the wrinkle secondary structure is slightly deformed, which increases the contact area, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor.

[0033] When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of tangential force under the pre-normal force (see Figure 3c ), the pyramid surface facing the tangential force direction in the micro-mortise and tenon structure is subjected to greater pressure than other surfaces, the wrinkle secondary structure on the compressed positive micro-pyramid surface undergoes micro-deformation, and the contact area increases with the increase of the tangential force, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the tangential force is greater than the static friction force, unstable slip occurs between the positive micro-pyramid surface and the inverted micro-pyramid surface, and at this time the contact area between the two is reduced, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor is reduced.

[0034] When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of torsion torque under the pre-normal force (see Figure 3d ), the micro-pyramid surfaces in the micro-mortise and tenon structure will be compressed, the wrinkle secondary structure on the compressed positive micro-pyramid surface will undergo micro-deformation, and the contact area will increase with the increase of the torque, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the torque is greater than the static friction torque, unstable separation will occur between the positive micro-pyramid surface and the inverted micro-pyramid surface, and at this time the contact area between the two will decrease, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor will decrease.

[0035] Figure 4 The relative resistance change (ΔR / R 0 ) changes with the normal force. It can be seen that in the low normal force range of 0 to 3.5N, that is, the approximate range of the force applied to the object by human touch, grasping and other actions, the sensitivity of the tactile sensor (S 1 ) is 0.18N -1 ; There is also a certain response in the high normal force area of ​​3.5~7N (S 2 =0.01N -1 ).like Figure 4 As shown in the illustration, the flexible micro-mortise and tenon structure tactile sensor responds to a normal force of 9.8 mN (≈ 1 g), which is close to the force when a human touches an object lightly, indicating that the detection limit of the flexible micro-mortise and tenon structure tactile sensor is low.

[0036] Figure 5 The ΔR / R of the flexible micro-mortise and tenon structure tactile sensor of this embodiment under three pre-normal forces (1, 2, 5N) are shown. 0 The curve of the change with the tangential force. It can be seen that when the tangential force is less than the maximum static friction force, the ΔR / R of the tactile sensor under the three pre-normal forces is 0 Both increase approximately linearly with the increase of tangential force; with the increase of pre-normal force, the sensitivity decreases but the linear response range becomes wider. When the tangential force is greater than the maximum static friction force, ΔR / R0 It decreases rapidly with the increase of tangential force, which is due to the unstable slip between the positive micro-pyramid surface and the inverted micro-pyramid surface.

[0037] Figure 6 The ΔR / R of the flexible micro-mortise and tenon structure tactile sensor of this embodiment under three pre-normal forces (1, 2, 5N) are shown. 0 Curves showing the change of torque. It can be seen that when the torque is less than the maximum static friction torque, the ΔR / R of the tactile sensor under the three pre-normal forces is 0 Both increase approximately linearly with the increase of torque; with the increase of preload, the sensitivity decreases but the linear response range becomes wider. When the torque is greater than the static friction torque, ΔR / R 0 It decreases rapidly with the increase of torque, which is due to the unstable separation between the positive micro-pyramid cone surface and the inverted micro-pyramid cone surface.

[0038] Figure 7a and 7b The resistance curves of the flexible micro-mortise and tenon structure tactile sensor of this embodiment under 5N vector force with polar angle and azimuth angle are shown respectively. It can be seen that the resistance of the flexible micro-mortise and tenon structure tactile sensor changes with the direction of the vector force. When the polar angle θ of the vector force is in the range of 60 to 120°, the resistance of the flexible micro-mortise and tenon structure tactile sensor first decreases and then increases, and the resistance is the smallest when the polar angle is 90° (see Figure 7a ); Under the same polar angle, when the azimuth angle φ of the vector force is ±45°, the resistance of the flexible micro-mortise and tenon structure tactile sensor is the smallest (see 7b).

[0039] Figure 4 , Figure 5 , Figure 6 , Figure 7a and Figure 7b The results shown indicate that the flexible micro-mortise and tenon structure tactile sensor can distinguish the type and direction of the external force it receives through different response intensities, and has multi-modal signal response monitoring capabilities.

[0040] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A flexible micro-mortise and tenon structure tactile sensor, characterized in that: It includes an upper flexible sensing substrate, a lower flexible sensing substrate, interdigital electrodes and a flexible bottom film; the interdigital electrodes include single-sided conductive finger electrodes and double-sided conductive finger electrodes, the lower surface of the single-sided conductive finger electrodes is conductive and the upper surface is non-conductive; The softness of the upper flexible sensing substrate is higher than that of the lower flexible sensing substrate. The lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate are respectively provided with convex and concave microstructures with the same characteristic size, and there are conductive film layers on the surfaces of the microstructures; the upper surface of the interdigitated electrode contacts the lower surface of the upper flexible sensing substrate, and the lower surface of the interdigitated electrode adheres to the upper surface of the lower flexible sensing substrate. The thickness of the interdigitated electrode forms a gap between the upper flexible sensing substrate and the lower flexible sensing substrate at the inter-finger position; the flexible bottom film is tightly attached to the lower surface of the lower flexible sensing substrate.

2. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: The convex and concave microstructure features are in the shape of a pyramid, a cone, a hemisphere, a truncated cone or a wave, and there are submicron-level wrinkled secondary structures on the surface of the microstructure.

3. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: The upper flexible sensing substrate and the lower flexible sensing substrate are flexible polymer substrates with conductive surfaces but different softness, and the conductivity is obtained through chemical oxidation, ion sputtering, deposition or spraying process.

4. A flexible micro-mortise and tenon structure tactile sensor according to claim 3, characterized in that: The flexible polymer substrate is prepared by injection compression molding, compression molding, roll molding, spin coating curing or ultraviolet light curing process, and the flexible polymer material is thermoplastic elastomer, ethylene-octene copolymer, polydimethylsiloxane, silicone rubber or photosensitive resin.

5. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: The thickness of the interdigital electrode is 0.05-0.2 mm, and the material is copper foil, aluminum foil or conductive glue.

6. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: The flexible micro-mortise and tenon structure tactile sensor has high sensitivity, low detection limit and multimodal signal response monitoring capability.

7. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: When the flexible micro-mortise and tenon structure tactile sensor is not subjected to force, the upper surface of the single-sided conductive finger-shaped electrode is in contact with the lower surface of the upper flexible sensing substrate, but they are insulated from each other, and the upper flexible sensing substrate and the lower flexible sensing substrate do not form a conductive path in the inter-finger area. At this time, after the interdigital electrode is energized, the charge only flows through the lower flexible sensing substrate; When the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of normal force in the inter-finger area, the upper flexible sensing substrate is bent and deformed, and a part of its lower surface comes into contact with the upper surface of the lower flexible sensing substrate; at the same time, in the contact area, the convex microstructures and the concave microstructures respectively arranged on the lower surface of the upper flexible sensing substrate and the upper surface of the lower flexible sensing substrate form an interlocking micro-mortise and tenon structure, and the wrinkled secondary structures on the microstructures are in contact with each other; As the normal force increases, the contact area of ​​the upper and lower flexible sensing substrates expands, the number of interlocking micro-mortise and tenon structures increases, and at the same time, the wrinkled secondary structure undergoes micro-deformation, which increases the contact area and thus reduces the resistance of the flexible micro-mortise and tenon structure tactile sensor.

8. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of tangential force under the pre-normal force, the microstructure surface facing the direction of the tangential force in the micro-mortise and tenon structure is subjected to greater pressure than other microstructure surfaces, and the wrinkle secondary structure on the compressed positive micro-pyramid cone surface undergoes micro-deformation, and the contact area increases with the increase of the tangential force, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the tangential force is greater than the static friction force, unstable slip occurs between the protruding microstructure and the recessed microstructure, and at this time the contact area between the two is reduced, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor is reduced.

9. A flexible micro-mortise and tenon structure tactile sensor according to claim 1, characterized in that: When the inter-finger area of ​​the flexible micro-mortise and tenon structure tactile sensor is subjected to a certain degree of torsional torque under the pre-normal force, the microstructures in the micro-mortise and tenon structure will be compressed, the wrinkle secondary structure on the compressed microstructure surface will undergo micro-deformation, and the contact area will increase with the increase of torsional torque, thereby reducing the resistance of the flexible micro-mortise and tenon structure tactile sensor; when the torsional torque is greater than the static friction torque, unstable separation will occur between the protruding microstructure and the recessed microstructure, and the contact area between the two will decrease, and the resistance change of the flexible micro-mortise and tenon structure tactile sensor will decrease.

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