A flexible tactile sensor based on tilted microspiky array enhancement and its fabrication method

Abstract

This invention discloses a flexible tactile sensor based on a tilted microspiky array for enhanced sensitivity and its fabrication method, belonging to the field of flexible tactile sensors. The sensor includes a dielectric layer with microspiky structures. The fabrication process is as follows: (1) a tilted photoresist microspiky array is fabricated using two-photon polymerization technology; (2) a polymer film A with micro-pits is cast onto the photoresist microspiky array; (3) a photocurable adhesive microspiky array is cast onto the polymer film A; (4) a polymer film B with micro-pits is cast using the photocurable adhesive microspiky array as a mold; (5) a target tilted microspiky array is cast as a dielectric layer using the polymer film B as a mold; (6) the dielectric layer and electrode layer are encapsulated to prepare a flexible tactile sensor based on a tilted microspiky array for enhanced sensitivity. This invention utilizes two-photon technology to process the tilted microspiky array in one step and a four-step molding process, enabling the fabrication of a flexible tactile sensor based on a tilted microspiky array for enhanced sensitivity on a flexible substrate.

Description

Technical Field

[0001] This invention relates to the field of flexible tactile sensor technology, specifically to a flexible tactile sensor based on a tilted micro-spiky array for enhanced sensitivity and its fabrication method. Background Technology

[0002] Flexible tactile sensors have attracted much attention in fields such as flexible tactile displays and human-computer interaction interfaces due to their small size, flexible and stretchable substrate, and ease of conformal integration. In particular, tactile sensors with shear force recognition capabilities can serve as artificial electronic skin for intelligent prosthetics, converting external tactile information into electrical signals and transmitting them to the central nervous system; they can also be integrated into the end effector of flexible robots as force feedback units to improve the efficiency and safety of dexterous operation of flexible robots.

[0003] Currently, flexible tactile sensors rely on an array structure combining inductive, capacitive, piezoresistive, and piezoelectric effects to identify pressure and shear force. The inductive effect distinguishes pressure and shear force by the suppression of coil inductance by eddy currents generated within a metal plate parallel to the coil. When subjected to pressure, the metal plate moves closer to the coil, increasing eddy currents and decreasing inductance; conversely, when subjected to shear force, the effective area occupied by the metal plate in the magnetic field generated by the coil decreases, reducing eddy currents and increasing inductance. Flexible tactile sensors based on capacitive, piezoresistive, and piezoelectric effects determine the direction of force application by observing the relative changes in capacitance, resistance, and voltage of the sensing unit array. Typically, four sensing units are required to form a sensing module group. Therefore, tactile sensors based on high-density array sensing units require further signal processing to convert the changes in capacitance, resistance, and voltage into an array cloud map to determine the direction of shear force. Summary of the Invention

[0004] The purpose of this invention is to provide a flexible tactile sensor based on a tilted micro-spiky array for enhanced sensitivity and a method for fabricating the same. The fabricated flexible tactile sensor can sense the direction of shear force. The fabrication process does not require the sensing unit to be made into a high-density array group, nor does it require further complex processing of the capacitance signal. By using two-photon technology to process the tilted micro-spiky array in one step and a four-step molding process, it is possible to fabricate a flexible tactile sensor based on a tilted micro-spiky array for enhanced sensitivity on a flexible substrate.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A flexible tactile sensor based on tilted microspiky array enhancement includes a dielectric layer with a microspiky structure, wherein: the dielectric layer includes a plurality of microspiky arrays arranged in an array, and the depth-to-diameter ratio of the microspiky array is adjustable; the dielectric layer is a polymer material doped with nanoparticles.

[0007] The dielectric layer has a thickness of 50-1000 μm, and the nanoparticles doped in the dielectric layer are one or more of carbon powder, carbon nanotubes, graphene and metal nanoparticles, with a doping amount of 1.5-10 wt.%.

[0008] The flexible tactile sensor also includes electrode layers disposed on both sides of the dielectric layer. The electrode layers include PET plastic layers with metal layers on their surfaces, and the metal layers are connected to leads.

[0009] The method for fabricating the flexible tactile sensor based on tilted micro-spiky array enhancement includes the following steps:

[0010] (1) Using two-photon polymerization technology to fabricate an array of tilted photoresist micro-spiks;

[0011] (2) Using an inclined photoresist micro-spiked array as a mold, a polymer film A with micro-pits is cast and fabricated;

[0012] (3) Using a polymer film A with micro-pits as a mold, a UV-curable adhesive micro-spiky array is cast and made. Since the micro-spiky array and the substrate are cast and formed as a whole by UV-curable adhesive, the inclined UV-curable adhesive micro-spiky array has extremely high strength and can be molded multiple times without being damaged.

[0013] (4) Using a light-curable adhesive micro-spiked array as a mold, a polymer film B with micro-pits is cast and produced. The polymer film B should have weak adhesion to the material of the target tilted micro-spiked array.

[0014] (5) Using a polymer film B with micro-pits as a mold, a target tilted micro-spiky array is cast and fabricated as the dielectric layer of a flexible capacitive tactile sensor.

[0015] (6) Encapsulate the dielectric layer and the electrode layer to prepare a flexible tactile sensor based on the sensitization enhancement of the tilted micro-spiky array.

[0016] In step (1) above, the process of fabricating the tilted photoresist micro-spiky array is as follows: a rigid substrate is placed on a three-dimensional motion platform as a receiving substrate, and a two-photon polymerization system is used to polymerize the photoresist material in situ onto the receiving substrate to form a tilted photoresist micro-spiky array; wherein: the rigid substrate is glass, silicon wafer, metal or polymethyl methacrylate (PMMA); the photoresist material is a commercially available negative photoresist, and the aspect ratio of the photoresist micro-spiky array is controllable.

[0017] In step (2) above, the process of preparing polymer film A with micropits is as follows: using an inclined photoresist micro-spiked array as a mold, polymer precursor A is poured onto the photoresist micro-spiked array, and after curing, a mold is made to obtain polymer film A with micropits; the polymer precursor A is made by mixing polymer A and curing agent, and the material of polymer film A is polymer A; the polymer A is polydimethylsiloxane (PDMS) or Ecoflex; the depth-to-diameter ratio of the micropits in polymer film A is controllable.

[0018] The process of making the photocurable adhesive micro-spiky array in step (3) above is as follows: using a polymer film A with micro-pits as a mold, the photocurable adhesive material is poured onto the polymer film A with micro-pits. After curing, the mold is flipped to obtain a photocurable adhesive structure with a micro-spiky array. The photocurable adhesive is a commercially available photocurable adhesive, and the depth-to-diameter ratio of the micro-spiky array in the photocurable adhesive structure is controllable.

[0019] The process of preparing the polymer film B with micropits in step (4) above is as follows: using a photocurable adhesive structure with a micro-spiked array as a mold, the polymer precursor B is poured onto the tilted micro-spiked array of photoresist, and after curing, the mold is flipped to obtain the polymer film B with micropits; the polymer precursor B is a mixture of polymer B solute and solvent, and the polymer film B is made of polymer B; the polymer B is polyvinyl alcohol (PVA) or polyethylene oxide (PEO), and the depth-to-diameter ratio of the micropits in the polymer film B is controllable.

[0020] The process of fabricating the dielectric layer in step (5) above is as follows: using a polymer film B with micro-pits as a mold, the dielectric layer material doped with nanoparticles is poured onto the polymer film B with micro-pits. After curing, the mold is flipped to obtain a dielectric layer with a micro-spiky array. The dielectric layer material doped with nanoparticles is a mixture of nanoparticles, dispersant, curing agent and polymer C. The dielectric layer is a polymer material doped with nanoparticles (formed by uniformly dispersing nanoparticles in polymer C).

[0021] The advantages and beneficial effects of this invention are as follows:

[0022] 1. The flexible tactile sensor and its manufacturing method of the present invention do not require the sensing unit to be made into a high-density array group, nor do they require further complex processing of the capacitance signal. By using two-photon technology to process the tilted micro-spiky array in one step and four-times mold-making process, a flexible tactile sensor based on tilted micro-spiky array-enhanced sensitivity can be manufactured on a flexible substrate.

[0023] 2. The flexible tactile sensor produced by this invention can determine the direction of shear force by changes in capacitance signal. Attached Figure Description

[0024] Figure 1A schematic diagram of a micro-spiky array structure fabricated on a rigid substrate.

[0025] Figure 2 A schematic diagram for fabricating a polymer film A with micropits.

[0026] Figure 3 A schematic diagram of the micro-spiky array structure for fabricating photocurable adhesive.

[0027] Figure 4 A schematic diagram for fabricating polymer film B with micropits.

[0028] Figure 5 A schematic diagram of the dielectric layer for fabricating the micro-spiky array.

[0029] Figure 6 This is a schematic diagram of the structure of the packaged flexible tactile sensor.

[0030] Figure 7 The images are scanning electron microscope (SEM) images of the photoresist micro-spiky array; where (a) and (b) are views at different magnifications.

[0031] Figure 8 The images are scanning electron microscope (SEM) images of a micro-spiky array of photocurable adhesive; where (a) and (b) are views at different magnifications.

[0032] Figure 9 The images are scanning electron microscope (SEM) images of the dielectric layer of the microspiky array; where (a) and (b) are views at different magnifications.

[0033] Figure 10 This is a performance test curve for a flexible tactile sensor.

[0034] In the figure: 1-Two-photon polymerization system; 2-Photoresist micro-spiky array; 201-Photoresist material; 3-Hard substrate; 4-Polymer film A; 401-Polymer precursor A; 5-Photocurable adhesive structure; 501-Photocurable adhesive; 6-Polymer film B; 601-Polymer precursor B; 7-Dielectric layer; 701-Dielectric layer material; 8-Electrode layer. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] This invention relates to a flexible tactile sensor based on a tilted microspiky array for enhanced sensitivity, and its fabrication method. The fabrication process is as follows: Figure 1-6As shown. First, photoresist material 201 is polymerized in situ onto a hard substrate 3 using a two-photon polymerization system 1 to form an inclined photoresist micro-spiked array 2. Using the inclined photoresist micro-spiked array 2 as a mold, a polymer precursor A401 is poured onto the inclined photoresist micro-spiked array 2. After curing, a mold is made to obtain a polymer film A4 with micro-pits. Using the polymer film A4 with micro-pits as a mold, photocurable adhesive 501 is poured onto the polymer film A4 with micro-pits. After curing, a mold is made to obtain a photocurable adhesive structure 5 with a micro-spiked array. Using a photocurable adhesive structure 5 with a micro-spiky array as a mold, a polymer precursor B601 is cast onto the photocurable adhesive structure 5. After curing, a mold is made to obtain a polymer film B6 with micro-pits. Using the polymer film B6 with micro-pits as a mold, a dielectric layer material 701 doped with nanomaterials is cast onto the polymer film B6 with micro-pits. After curing, a mold is made to obtain a dielectric layer 7 with a micro-spiky array. The dielectric layer 7 with a micro-spiky array and the electrode layer 8 are encapsulated to obtain a flexible capacitive tactile sensor based on tilted micro-spiky enhancement.

[0037] This invention places a rigid substrate on a mobile receiving platform, and the two-photon processing power, polymerization rate, resolution, two-photon polymerization material, and rigid substrate are all adjustable. The depth-to-diameter ratio of the micro-spiky array can be controlled according to different usage requirements, and the direction of the micro-spiky is adjustable. It can fabricate arrayed one-dimensional and two-dimensional micro-spiky array structures.

[0038] In this invention, the flexible polymer film can be replaced with different materials as needed, and the depth-to-diameter ratio and orientation of the micro-pits can be controlled according to different usage requirements.

[0039] The nanomaterials in the dielectric layer of this invention can be replaced with different materials as needed, and the concentration of the nanomaterials can be controlled according to different usage requirements.

[0040] Example 1:

[0041] A glass substrate was placed on a three-dimensional motion platform. SZ2080 photoresist material was in-situ polymerized onto the substrate using a two-photon polymerization system. After polymerization, the substrate was developed with a propyl ether-acetic acid-methanol solution for 20 minutes and then cleaned with isopropanol for 3 minutes to form an inclined array of photoresist micro-spiks. The scanning electron microscope image is shown below. Figure 7 As shown.

[0042] Using an inclined photoresist micro-spiked array as a mold, polymer precursor A is poured onto the photoresist micro-spiked array and cured by heating at 80°C for 2 hours to obtain a polydimethylsiloxane polymer film A with micro-pits; wherein: the polymer precursor A is composed of polydimethylsiloxane main agent and curing agent mixed in a mass ratio of 10:1.

[0043] Using a polydimethylsiloxane polymer film A with micropits as a mold, NOA 74 photocurable adhesive was poured onto the polydimethylsiloxane polymer film A with micropits. After curing under a 15W UV lamp for 10 minutes, the film was flipped to obtain a NOA 74 photocurable adhesive structure with a micro-spiky array. The scanning electron microscope image is shown below. Figure 8 As shown.

[0044] Using a NOA 74 UV-curable adhesive structure with a micro-spiky array as a mold, polymer precursor B is poured onto the NOA 74 UV-curable adhesive structure. After curing at 100°C for 20 minutes, the mold is flipped to obtain a polyvinyl alcohol polymer film B with micro-pits. The polymer precursor B is a mixture of polyvinyl alcohol particles and water solvent at a mass ratio of 1:10.

[0045] Using a polyvinyl alcohol polymer film B with micropits as a mold, a dielectric layer precursor was cast onto the polyvinyl alcohol polymer film B with micropits. After curing at 100℃ for 1 hour, the film was molded to obtain a dielectric layer with a micro-spiky array. The scanning electron microscope image is shown below. Figure 9 As shown. The dielectric layer precursor is composed of graphene, dispersant, curing agent, and polymer material mixed in a mass ratio of 0.75:40:1:10. The polymer material is polydimethylsiloxane, and the prepared dielectric layer is a graphene-doped polymer material (a composite material composed of graphene and polydimethylsiloxane). The dielectric layer thickness is 200 μm.

[0046] Using a PET layer with a 5nm gold film as the electrode layer, electrode layers are set on both sides of a dielectric layer with a micro-spiky array and encapsulated to obtain a flexible capacitive tactile sensor based on tilted micro-spiky enhancement.

[0047] The capacitance signal of the flexible capacitive tactile sensor prepared in this embodiment changes with the magnitude and direction of the applied force, as follows: Figure 10 As shown in the figure, when the sensor is subjected to positive pressure, the capacitance signal changes drastically. Then, when the sensor is subjected to a leftward shear force (the direction of the force is opposite to the tilt direction of the micro-spiky array), the sensor capacitance signal decreases; when the sensor is subjected to a rightward shear force (the direction of the force is the same as the tilt direction of the micro-spiky array), the sensor capacitance signal increases. Therefore, the flexible capacitive tactile sensor fabricated in this invention can determine the direction of the force based on changes in the capacitance signal.

Claims

1. A flexible tactile sensor based on the sensitivity enhancement of an array of tilted micro spikes, characterized by: The flexible tactile sensor comprises a dielectric layer with micro spike structure, wherein: the dielectric layer comprises a plurality of inclined micro spikes arranged in an array; the dielectric layer is a nanoparticle-doped polymer material; the flexible tactile sensor further comprises electrode layers arranged on both sides of the dielectric layer; when the sensor is subjected to a left shear force, the sensor capacitance signal decreases, and the direction of the left shear force is opposite to the inclination direction of the micro spike array; when the sensor is subjected to a right shear force, the sensor capacitance signal increases, and the direction of the right shear force is the same as the inclination direction of the micro spike array. The thickness of the dielectric layer is 50-1000 μm, the nanoparticles doped in the dielectric layer are one or more of carbon powder, carbon nanotube, graphene and metal nanoparticles, and the nanoparticle doping amount in the dielectric layer is 1.5-10 wt%. 2.The flexible tactile sensor based on the tilt micro spike array sensitization according to claim 1, wherein: The electrode layer comprises a PET plastic layer with a metal layer on the surface, and the metal layer is connected to a lead wire.

3. The method of claim 1 or 2, wherein the method further comprises: The method comprises the following steps: (1) using a two-photon polymerization technology to manufacture an inclined photoresist micro spike array; (2) using the inclined photoresist micro spike array as a mold, pouring to manufacture a polymer film A with micro pits; (3) using the polymer film A with micro pits as a mold, pouring to manufacture a photo-curing glue micro spike array; (4) using the photo-curing glue micro spike array as a mold, pouring to manufacture a polymer film B with micro pits; (5) using the polymer film B with micro pits as a mold, pouring to manufacture a target inclined micro spike array as a dielectric layer of a flexible capacitive tactile sensor; (6) packaging the dielectric layer and the electrode layer to prepare a flexible tactile sensor based on the inclined micro spike array.

4. The method of claim 3, wherein the method further comprises: In step (1), the process of manufacturing the inclined photoresist micro spike array is as follows: placing a hard substrate on a three-dimensional motion platform as a receiving substrate, using a two-photon polymerization system to polymerize photoresist material in situ on the receiving substrate to form an inclined photoresist micro spike array; wherein: the hard substrate is glass, silicon wafer, metal or polymethyl methacrylate; the photoresist material is a commercial negative photoresist, and the depth-diameter ratio of the photoresist micro spike array is controllable.

5. The method of claim 3, wherein the method further comprises: In step (2), the process of manufacturing the polymer film A with micro pits is as follows: using the inclined photoresist micro spike array as a mold, pouring polymer precursor A onto the photoresist micro spike array, and after solidification, performing mold turning to obtain a polymer film A with micro pits; the polymer precursor A is obtained by mixing polymer A and a curing agent, the material of the polymer film A is polymer A; the polymer A is polydimethylsiloxane or Ecoflex; the depth-diameter ratio of the micro pits in the polymer film A is controllable.

6. The method of claim 3, wherein the method further comprises: In step (3), the process of manufacturing the photo-curing glue micro spike array is as follows: using the polymer film A with micro pits as a mold, pouring photo-curing glue material onto the polymer film A with micro pits, and after solidification, performing mold turning to obtain a photo-curing glue structure with a micro spike array; the photo-curing glue is a commercial photo-curing glue, and the depth-diameter ratio of the micro spike array in the photo-curing glue structure is controllable.

7. The method of claim 3, wherein the method further comprises: The step (4) is the process of preparing the polymer film B with micro-pits, which comprises the following steps: using the photoresist structure with the micro-sting array as a mold, pouring the polymer precursor B on the photoresist inclined micro-sting array, and after solidification, turning the mold to obtain the polymer film B with micro-pits; the polymer precursor B is mixed by the polymer B solute and the solvent, the material of the polymer film B is the polymer B, the polymer B is polyvinyl alcohol or polyethylene oxide, and the depth-diameter ratio of the micro-pit in the polymer film B is controllable.

8. The method of claim 3, wherein the method further comprises: The step (5) is the process of preparing the dielectric layer, which comprises the following steps: using the polymer film B with micro-pits as a mold, pouring the dielectric layer material doped with nano-particles on the polymer film B with micro-pits, and after solidification, turning the mold to obtain the dielectric layer with the micro-sting array.

Images