Array-type flexible tactile sensor and manufacturing method therefor, and tactile sensing system

Abstract

An array-type flexible tactile sensor, comprising a plurality of flexible tactile sensor units arranged in an array. Each tactile sensor unit comprises, from top to bottom, a friction layer, a hydrophilic layer, an electrode layer, and a substrate layer. The lower surface of the friction layer is a hydrophilic surface. By adding the hydrophilic layer between the friction layer and the electrode layer, the friction layer and the electrode layer can be well bonded; on this basis, the electrode layer is printed on the hydrophilic layer by adopting a simple screen printing method, so that the electrode layer can be bonded to the friction layer; a screen printing plate is designed into an array-type structure, so that the array-type tactile sensor can be directly obtained, realizing large-area batch production, and improving the manufacturing efficiency. The manufactured array-type flexible tactile sensor can realize dynamic multi-point sensing, the sensitivity, the working stability and the resolution are improved, and self-powering and self-driving can be achieved. Also provided are a manufacturing method for the array-type flexible tactile sensor, and a tactile sensing system.

Description

Array-type flexible tactile sensor, preparation method thereof, and tactile sensing system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 12, 2023, with application number 202311708259.7 and invention name “An array-type flexible tactile sensor, its preparation method and tactile sensing system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the technical field of tactile sensor preparation, and in particular to an array-type flexible tactile sensor, a preparation method thereof, and a tactile sensing system. Background Art

[0003] Sensing technology is one of the three pillars of today's information technology. With the development of the Internet, sensing technology has achieved unprecedented development prospects. Among them, tactile sensing technology is more widely used. It can respond to external stimuli. Compared with traditional tactile sensors, flexible tactile sensors have good flexibility and can fit well on various complex surfaces (such as various joints of the human body) to better perform real-time monitoring. In order to realize the application of specific functions, a huge sensor network is required to connect with the human body or robot, so the supply of energy is crucial. However, many power supplies are rigid power supplies, which are relatively heavy and large in size, and inevitably have the problems of high cost and large application limitations, which are not convenient for use in flexible sensors. In addition, the resolution of current tactile sensors is not high, and the signal recognition for monitoring is not accurate enough.

[0004] Triboelectric nanogenerators, based on the coupling of triboelectric charging and electrostatic induction, can harvest bioenergy and use it as an energy source for sensors, converting mechanical signals into electrical signals. They generate energy in a low-frequency, lightweight manner, offering advantages such as low cost and fast response time. Currently, combining triboelectric nanogenerator technology with tactile sensors to create flexible tactile sensors with self-propulsion, low cost, high resolution, and ease of mass production has become a hot topic for many researchers.

[0005] To improve the resolution of tactile sensors, they are generally designed as array structures. A report has disclosed an arrayed triboelectric tactile sensor, which includes multiple arrayed triboelectric tactile units. A single tactile sensing unit consists of an insulating flexible inverted cone, a metal electrode, a flexible cover layer, a flexible intermediate layer, a flexible bottom layer, and leads. The triboelectric pair formed by the insulating flexible inverted cone and the metal electrode converts deformation into an electrical signal through contact electrification and electrostatic coupling effects, achieving self-powered and highly sensitive measurement of three-dimensional contact forces, including contact normal stress and sliding shear force. However, the structure of a single flexible sensing unit is relatively complex, and the document does not disclose the preparation method for achieving the array structure.

[0006] Flexible tactile sensors based on triboelectric charging generally include an electrode layer and a friction layer. The electrode layer is generally made of a hydrophilic material, while the friction layer is mostly made of a hydrophobic polymer. Due to the difference in hydrophilicity and hydrophobicity, it is difficult to achieve a good fit between the friction layer and the electrode layer, which is not conducive to the precise preparation of array structures. Current research has mostly focused on setting single or multiple reinforcement layers at the non-friction interface between the friction layer and the electrode layer to enhance the pressure electrical signal output under the action of the induced external force. Less attention has been paid to how to prepare array-type flexible tactile sensors based on triboelectric charging.

[0007] Summary of the Invention

[0008] In view of this, the present invention aims to provide an array-type flexible tactile sensor, a method for preparing the same, and a tactile sensing system. The tactile sensor comprises an array-type sensing unit comprising, from top to bottom, a friction layer, a hydrophilic layer, an electrode layer, and a base layer. This allows for close adhesion between the friction layer and the electrode layer, facilitating the fabrication of the array sensor and exhibiting the advantages of high resolution, high sensitivity, and good stability.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides an array-type flexible tactile sensor, comprising a plurality of arrayed flexible tactile sensor units, wherein the flexible tactile sensor units comprise, from top to bottom, a friction layer, a hydrophilic layer, an electrode layer, and a base layer;

[0011] The lower surface of the friction layer is a hydrophilic surface.

[0012] Preferably, the lower surface of the friction layer is a hydrophilic surface modified by a surfactant.

[0013] Preferably, the surfactant is selected from any one or more of sodium lauryl sulfate, sodium diisobutyl sulfosuccinate, dodecyltrimethylammonium chloride or sodium dodecylbenzenesulfonate.

[0014] Preferably, the friction layer is selected from any one or more of perfluoroethylene propylene copolymer, polytetrafluoroethylene, polydimethylsiloxane, polyethylene, polyoxyethylene, polystyrene, polypropylene, polyvinyl chloride or polyvinylidene chloride.

[0015] Preferably, the hydrophilic layer is selected from any one or more of polyvinyl alcohol, polyimide or polyurethane.

[0016] Preferably, the electrode layer is selected from any one of graphene, modified graphene, modified graphene biocomposite, carbon nanotube, modified carbon nanotube, modified carbon nanotube biocomposite or PEDOT:PSS.

[0017] Further preferably, the electrode layer is a carboxylated multi-walled carbon nanotube / chitosan composite material.

[0018] Preferably, the base layer is selected from any one of polyurethane, polyimide, polyethylene terephthalate or polydimethylsiloxane.

[0019] In a second aspect, the present invention further provides a method for preparing the above-mentioned array-type flexible tactile sensor, comprising the following steps:

[0020] (1) After the friction layer is subjected to hydrophilic modification treatment, a hydrophilic layer is prepared on its surface;

[0021] (2) coating the electrode layer on the surface of the hydrophilic layer by screen printing;

[0022] Wherein, the screen printing plate used in the screen printing method has an array structure;

[0023] (3) Combining the base layer with the electrode layer to obtain the array-type flexible tactile sensor.

[0024] Preferably, the hydrophilic modification is specifically: treating the friction layer with oxygen plasma and then treating it with a surfactant.

[0025] Preferably, the radio frequency power of the oxygen plasma treatment is 100-130 W, the treatment time is 30-60 s, and the oxygen flow rate is 120-160 sccm.

[0026] In a third aspect, the present invention further provides a tactile perception system, comprising the array-type flexible tactile sensor involved in the above technical solution.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention provides an array-type flexible tactile sensor, comprising a plurality of arrayed flexible tactile sensor units, wherein the flexible tactile sensor units sequentially comprise a friction layer, a hydrophilic layer, an electrode layer, and a base layer from top to bottom. The friction layer is subjected to a hydrophilic modification treatment and then covered with a hydrophilic layer, so that the friction layer and the electrode layer are well bonded;

[0029] (2) On the basis that the friction layer and the electrode layer can be well bonded, the present invention can use a simple screen printing method to print the electrode layer on the hydrophilic layer, thereby combining it with the friction layer, and the screen printing plate is designed into an array structure, which can directly obtain an arrayed touch sensor, which is conducive to large-scale batch production and improves preparation efficiency;

[0030] (3) The array-type flexible tactile sensor provided by the present invention can realize dynamic multi-point sensing, improve the conversion efficiency, sensing sensitivity, working stability and resolution of the sensor in converting biological energy into electrical energy, and can achieve self-power and self-drive without the need for external power supply. In addition, the selection of a flexible substrate makes the sensor very wearable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of the screen printing method; Figure 2 is a schematic diagram of the structure of an array-type flexible tactile sensor; Figure 3 is a design diagram of the array structure; Figure 4 is a sensitivity test curve diagram of the array-type flexible tactile sensor; Figure 5 is a stability test result diagram of the array-type flexible tactile sensor; Figure 6 is an image of the micro-nano structure (5 cm) formed after the nanofiber membrane in Example 2 is treated with sandpaper; Figure 7 is an SEM image of the nanofiber membrane in Example 2. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] In response to the problems of complex structure of flexible tactile sensors in the prior art and difficulty in preparing sensors with an arrayed structure, the present invention provides an arrayed flexible tactile sensor, including a plurality of arrayed flexible tactile sensor units, wherein the flexible tactile sensor units include a friction layer, a hydrophilic layer, an electrode layer and a base layer from top to bottom.

[0034] In the present invention, the lower surface of the friction layer is hydrophilic. The friction layer is preferably treated with a hydrophilic surface modification method, such as plasma treatment, UV-ozone treatment, layer-by-layer self-assembly, sol-gel method, dynamic coating modification, silanization, and graft copolymerization. The lower surface of the friction layer is preferably a hydrophilic surface modified with a surfactant, and more preferably, a hydrophilic surface treated sequentially with oxygen plasma and then a surfactant. After the oxygen plasma treatment, an oxide layer forms on the surface of the friction layer. The friction layer is then treated with an amphiphilic surfactant, such that the lipophilic interface of the surfactant contacts the oxide layer, while the hydrophilic interface is exposed on the side away from the oxide layer, thereby rendering the friction layer surface hydrophilic. The surfactant may include any one or more of sodium dodecyl sulfate (SDS), sodium diisobutyl sulfosuccinate, dodecyltrimethylammonium chloride, or sodium dodecylbenzenesulfonate.

[0035] The array of flexible tactile sensors described above can be attached to objects and used to monitor their usage. For example, the base layer of the tactile sensor can be attached to a mouse to monitor the frequency of clicks and other usage patterns when the user is using the mouse. The working principle is as follows: When the skin (finger) comes into contact with the surface friction layer, the skin and the PDMS layer are electrified due to contact, causing charges to accumulate on the surface. The friction layer surface is negatively charged, while the skin surface is positively charged. At this point, the entire device appears electrically neutral. When the skin separates from the friction layer surface, electrons are transferred from the electrode layer to the ground to balance the negative charge accumulated on the friction layer surface. The electrode layer gradually acquires a positive charge equal to the friction layer's. When the skin and the friction layer come into close contact again, electrons flow from the ground back to the electrode layer.

[0036] The flexible tactile sensor array provided by the present invention can be directly attached to human skin to monitor human health information. For example, the tactile sensor array can be attached to the neck (where the friction layer contacts the skin). When the neck twists, a sensing signal is generated to detect the degree of change in neck movement. Similarly, it can also be attached to the wrist and ankle. The operating principle is consistent with the above.

[0037] The tactile sensor provided by the present invention includes a plurality of arrayed flexible tactile sensor units, which include a friction layer, a hydrophilic layer, an electrode layer and a substrate layer from top to bottom. The friction layer is hydrophilically modified and then covered with a hydrophilic layer on its surface, so that the friction layer and the electrode layer are well bonded, which is conducive to the preparation of an array structure to achieve dynamic multi-point sensing, improve the conversion efficiency, perception sensitivity, working stability and resolution of the sensor in converting bio-energy into electrical energy, and can achieve self-power and self-drive without the need for external power supply. In addition, the selection of a flexible substrate makes the sensor very wearable.

[0038] The present invention also provides a method for preparing the array-type flexible tactile sensor involved in the above technical solution, comprising the following steps:

[0039] (1) After the friction layer is subjected to hydrophilic modification treatment, a hydrophilic layer is prepared on its surface;

[0040] (2) coating the electrode layer on the surface of the hydrophilic layer by screen printing;

[0041] Wherein, the screen printing plate used in the screen printing method has an array structure;

[0042] (3) Combining the base layer with the electrode layer to obtain the array-type flexible tactile sensor.

[0043] According to the present invention, the friction layer is first subjected to a hydrophilic modification treatment, and then a hydrophilic layer is formed on its surface. In the present invention, the friction layer is selected from any one or more of perfluoroethylene propylene copolymer, polytetrafluoroethylene, polydimethylsiloxane, polyethylene, polyethylene oxide, polystyrene, polypropylene, polyvinyl chloride, or polyvinylidene chloride. These materials can also be used as friction layer materials after surface functional modification. The friction layer can be purchased directly or prepared according to conventional preparation methods familiar to those skilled in the art, such as spin coating or electrospinning. The spin coating method preferably includes a low-speed stage (or static glue dripping) and a high-speed stage. The low-speed stage has a rotation speed of 800-1000 rpm and a duration of 25-40 seconds, while the high-speed stage has a rotation speed of 3000-5000 rpm and a duration of approximately 1 minute. The electrospinning method can produce polymer filaments with nanometer-scale diameters as a friction layer. The resulting friction layer has a high specific surface area and porosity, which can increase the air permeability of the friction layer and the interaction area between the friction layer and the object being detected, and is expected to significantly improve the performance of the sensor.

[0044] After the friction layer is prepared, it is preferably first subjected to a hydrophilic modification treatment. Methods for surface hydrophilic modification include plasma treatment, UV-ozone treatment, layer-by-layer self-assembly, sol-gel method, dynamic coating modification, silanization, and graft copolymerization. The present invention preferably uses a surfactant to treat the friction layer to modify its surface energy and make it hydrophilic. However, using a single surfactant to treat the friction layer can lead to partial penetration of the surfactant into the friction layer over time, reducing its flexibility and causing it to break, hindering practical sensor applications. Therefore, the present invention further utilizes a combined oxygen plasma treatment and surfactant treatment for hydrophilic modification. By pre-forming an oxide layer on the friction layer surface, this prevents the surfactant from penetrating into the friction layer. In the present invention, the hydrophilic modification specifically involves treating the friction layer with oxygen plasma followed by surfactant treatment. The oxygen plasma treatment can be performed using a conventional oxygen plasma apparatus. The oxygen plasma treatment is performed at a radio frequency power of 100-130 W, for 30-60 seconds, and at an oxygen flow rate of 120-160 sccm. After the oxygen plasma treatment, the treated friction layer is directly immersed in a surfactant solution, then removed, rinsed, and dried to obtain a hydrophilic friction layer. The surfactant is selected as described in the above technical solution and will not be detailed here. The soaking time is 20 to 40 seconds, and deionized water is used for rinsing. The friction layer is then blown dry with nitrogen.

[0045] It should be noted that in order to further increase the specific surface area of ​​the friction layer and improve the sensing performance, plasma etching or simple sandpaper can be used to treat the surface of the friction layer so that the surface of the friction layer in contact with external objects or skin has a micro-nano structure.

[0046] After obtaining the hydrophilic friction layer, a hydrophilic layer is constructed on the surface of the friction layer. The hydrophilic layer is selected from any one or more of polyvinyl alcohol, polyimide or polyurethane, preferably polyvinyl alcohol (PVA). The preparation of the PVA can be carried out according to conventional methods. The present invention preferably heats the aqueous solution of PVA at 90-95°C for 2-4 hours, and then adds glutaraldehyde (GA) and a small amount of dilute acid to promote cross-linking to obtain a GA-crosslinked PVA solution. Then, referring to the spin coating method in the above technical solution, the GA-crosslinked PVA solution is spin-coated on the hydrophilic friction layer to obtain a hydrophilic layer-friction layer; or the GA-crosslinked PVA solution is prepared into a film on the hydrophilic friction layer by electrospinning to obtain a hydrophilic layer-friction layer material.

[0047] It should be noted that the hydrophilic layer primarily serves to create a hydrophilic surface on the friction layer. This synergistic effect, combined with the aforementioned plasma treatment and surfactant treatment, allows for a clear, printed array of electrode layers on the friction layer. Furthermore, the hydrophilic layer is made of a high-molecular-weight polymer, which creates a polarized charge distribution during generator operation, thereby increasing output.

[0048] After obtaining the hydrophilic layer-friction layer material, the electrode layer raw material is first prepared and then coated onto the surface of the hydrophilic layer using a screen printing method. The electrode layer is selected from any one of graphene, modified graphene, modified graphene biocomposite, carbon nanotubes, modified carbon nanotubes, modified carbon nanotube biocomposite, or PEDOT:PSS. Carbon nanotubes can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes based on the number of layers. Single-walled carbon nanotubes have superior conductivity compared to multi-walled carbon nanotubes, but multi-walled carbon nanotubes are less expensive to prepare. The appropriate electrode material can be selected based on the device's performance and cost requirements. While meeting the conductivity requirements, the present invention selects multi-walled carbon nanotubes for cost considerations. However, due to their large specific surface area and aspect ratio, adjacent carbon nanotubes can agglomerate due to strong van der Waals forces, hindering subsequent printing. Therefore, effective dispersion of the carbon nanotubes is crucial. In the present invention, multi-walled carbon nanotubes are preferentially carboxylated, and then chitosan with good biocompatibility is electrostatically adsorbed with the carboxylated multi-walled carbon nanotubes to finally obtain a well-dispersed carboxylated multi-walled carbon nanotube / chitosan composite material as the electrode layer raw material.

[0049] Then, the electrode layer raw material is printed on the surface of the hydrophilic layer by a screen printing method to obtain an electrode layer-hydrophilic layer-friction layer material. The screen printing method can be operated according to technical means familiar to those skilled in the art, wherein the electrode layer raw material is used as conductive ink, the screen printing plate has an array structure, and the substrate is a hydrophilic layer-friction layer. The schematic diagram of the screen printing method is shown in Figure 1. During printing, conductive ink is poured into one end of the screen printing plate, and a certain pressure is applied to the ink part on the screen printing plate with a scraper. At the same time, the screen printing plate moves at a constant speed toward the other end. During the movement, the ink is squeezed from the array mesh by the scraper onto the substrate, and the electrode layer can be printed on the surface of the hydrophilic layer. The printing plate in the screen printing method is soft and has a certain elasticity. It is not only suitable for printing on soft items such as paper and cloth, but also suitable for printing on hard items. The printed ink layer is thick and has strong covering power. By screen printing, the design of the pattern shape of the electrode layer can be realized, and the preparation of the array electrode layer can be realized, which lays the foundation for achieving multi-function and high performance.

[0050] After obtaining the electrode layer-hydrophilic layer-friction layer material, the present invention preferably uses a base layer for encapsulation and support, resulting in an array-type tactile sensor having a base layer-electrode layer-hydrophilic layer-friction layer structure. The base layer is selected from a polymer material such as polyurethane, polyimide, polyethylene terephthalate, or polydimethylsiloxane. It can be spin-coated onto the surface of the electrode layer to form a film, or electrospun onto the surface of the electrode layer to form a film. If the base layer is a commercially available finished product, the base layer and electrode layer can also be bonded using hot pressing.

[0051] The preparation method of the above-mentioned array-type flexible tactile sensor provided by the present invention is to perform hydrophilic modification on the friction layer and then cover its surface with a hydrophilic layer, so that the friction layer and the electrode layer are well bonded. On this basis, a simple screen printing method can be used to directly print the electrode layer on the hydrophilic layer, thereby combining it with the friction layer, and the screen printing plate is designed into an array structure, so that a sensor with an array structure can be directly obtained, which is conducive to large-scale mass production and improves preparation efficiency.

[0052] The present invention also provides a tactile perception system, which includes an array of flexible tactile sensors prepared by the above technical solution, and may also include a signal acquisition module, a control module and a power supply module.

[0053] The array-type flexible tactile sensor is used to sense the external force acting thereon and output a pressure electrical signal corresponding to the external force;

[0054] The signal acquisition module is connected to the arrayed flexible tactile sensor and is used to collect and process the pressure electrical signals output by the arrayed flexible tactile sensor;

[0055] The adjustment module is connected to the signal acquisition module and is used to adjust the external force acting on the array-type flexible tactile sensor according to the pressure electrical signal output by the signal acquisition module;

[0056] The power supply module is connected to the signal acquisition module and is used to supply power to the signal acquisition module.

[0057] To further illustrate the present invention, the following examples are provided for detailed description. The experimental materials used in the following examples can be purchased commercially or prepared according to conventional methods known to those skilled in the art. Chitosan was purchased from McLean Biochemical Technology Co., Ltd., with a deacetylation degree of 90% and a MW of 200,000; carboxylated multi-walled carbon nanotubes and multi-walled carbon nanotubes were purchased from Aladdin Biochemical Technology Co., Ltd., with a purity of >98%, a tube diameter of 5-15 nm, and a tube length of 10-30 μm; and PDMS prepolymer and curing agent were purchased from Dow Corning Co., Ltd., Model 184.

[0058] Example 1

[0059] This embodiment provides an array-type flexible tactile sensor, the structure of which is shown in FIG2 . From top to bottom, it includes a friction layer, a hydrophilic layer, an electrode layer, and a base layer. The specific preparation method is as follows:

[0060] (1) Dissolving chitosan powder at a concentration of 1% (w / v) in a 1 wt% acetic acid solution at room temperature, and continuously stirring with a glass rod in a beaker until the chitosan powder is completely dissolved, to obtain a protonated chitosan solution dissolved in acetic acid;

[0061] (2) 200 mg of carboxylated multi-walled carbon nanotubes, 100 mg of hexadecyltrimethylammonium bromide, and 10 mL of chitosan acetic acid solution were mixed in a beaker, placed on a magnetic stirrer for mechanical stirring (500 r / min, 15 min), and then ultrasonically dispersed in a cell crusher to uniformly disperse the carboxylated multi-walled carbon nanotubes and chitosan in the solution. The mixture was then heated on a hot plate at 60°C to evaporate most of the water until the solution became viscous, thereby obtaining a carboxylated multi-walled carbon nanotube / chitosan composite material, i.e., the electrode layer material.

[0062] (3) PDMS prepolymer and curing agent were mixed in a ratio of 10:1, stirred thoroughly, and vacuumed to remove bubbles (30 min) to obtain a PDMS solution;

[0063] Prepare the glass plate and wipe the surface of the glass plate with alcohol to ensure that there is no impurities or dust on the surface. Install the spin coater and vacuum pump, turn on the vacuum pump, place the glass plate in the center of the substrate, firmly adsorb it, and rotate it evenly. The spin coating process is divided into two gradient stages. The first stage is low-speed rotation. During the low-speed rotation stage, the PDMS solution is added dropwise, and it must be dropped in the center of the substrate; the second stage is high-speed rotation, which accelerates to the final spin coating speed to form a coating of the correct thickness. Among them, the low-speed rotation speed is 900r / min, the time is 30s, and the high-speed rotation speed is 4000r / min, the time is 1min, and it is dried at 80°C for 20min to finally form a PDMS layer, that is, a friction layer;

[0064] (4) The PDMS layer was treated with a PLASMACLEANER instrument (RF power of 120 W, oxygen flow rate of 150 sccm) for 40 s, and then the treated PDMS layer was immersed in a 0.5 wt% SDS solution for 30 s, rinsed with deionized water for 30 s, and finally dried with nitrogen to obtain a hydrophilic PDMS layer;

[0065] 4 g of PVA particles and 40 g of water were placed in a 50 mL round-bottom flask, swelled in cold water, stirred thoroughly, placed in an oil bath, and heated at 90°C for 2 h to dissolve. Then, 5 mL of 10 wt% GA (glutaraldehyde) and 500 μL of dilute hydrochloric acid were added to obtain a GA-crosslinked PVA solution, i.e., the hydrophilic layer material.

[0066] Referring to the spin coating method in step (3), the GA cross-linked PVA solution is spin-coated on the hydrophilic PDMS layer to obtain a hydrophilic layer-PDMS layer;

[0067] (5) The electrode layer material obtained in step (2) is printed on the surface of the hydrophilic layer in the hydrophilic layer-PDMS layer obtained in step (4) by screen printing, and then placed in a drying oven for drying at 60° C. for 10 min, and a copper enameled wire is fixed to the end of the electrode layer material with a conductive silver paste;

[0068] The screen printing plate has an array structure as shown in FIG3 .

[0069] (6) 15 mL of PDMS solution was taken and dried at 80°C to obtain a PDMS film, i.e., the base layer. The base layer was combined with the electrode layer material screen-printed on the surface of the hydrophilic layer by hot pressing to finally prepare an array-type flexible tactile sensor.

[0070] The resulting array of flexible tactile sensors was tested for sensitivity and stability using a linear motor. The test results are shown in Figures 4 and 5. Figure 4 shows the sensitivity test curve of the array of flexible tactile sensors, and Figure 5 shows the stability test results of the array of flexible tactile sensors. Figure 4 shows that the tactile sensor has excellent response sensitivity under low external forces. Figure 5 shows that after approximately 1000 cycles of testing, the peak output current does not change significantly, indicating that the tactile sensor has excellent operational stability.

[0071] Example 2

[0072] This embodiment provides an array-type flexible tactile sensor, the structure of which is shown in FIG2 . From top to bottom, it includes a friction layer, a hydrophilic layer, an electrode layer, and a base layer. The specific preparation method is as follows:

[0073] (1) Ultrasonic dispersion of a 20% PEDOT / PSS solution for 30 min was performed to ensure good dispersion and no sedimentation.

[0074] (2) Prepare a hydrophilic layer on the base layer: Mix acetic anhydride and DMF in a ratio of 1:1, then mix with polyamide acid solution in a mass ratio of 100:35, stir evenly in an environment below 0°C, and apply a film on the base PU film by spin coating, with a low-speed stage (or static glue dripping) and a high-speed stage. The speed of the low-speed stage is 800-1000 r / min, the time is 25-40s, and the speed of the high-speed stage is 5000-7000 r / min, the time is about 1 minute, and the polyurethane-polyimide layer is obtained by successively placing it in an oven at 120°C and 300°C, and dehydrating and curing to obtain a polyurethane-polyimide layer;

[0075] (3) Apply the dispersed PEDOT / PSS electrode material to one side of the electrode pattern on the screen printing plate. The screen printing scraper prints the PEDOT / PSS electrode material on the substrate and places it in a drying oven to dry. Use conductive silver paste to fix the copper enameled wire to the end of the electrode material.

[0076] (4) Preparation of friction layer: A PU solution with a mass fraction of 18% was prepared: PU particles + DMF + acetone. The electrospinning method was used. The electrospinning parameters (voltage, receiving distance, and propulsion speed) were 20 kV, 20 cm, and 0.5 mL / h, respectively. A nanofiber membrane with a micro-nano structure was prepared on sandpaper using a 20-gauge needle.

[0077] The prepared PU nanofiber membrane / PU film is combined with the electrode material screen-printed on the substrate layer by a hot pressing method.

[0078] FIG6 is an image of the micro-nanostructure formed after the nanofiber membrane is treated with sandpaper (5 cm), and FIG7 is an SEM image of the nanofiber membrane.

[0079] Example 3

[0080] This embodiment provides an array-type flexible tactile sensor, the structure of which is shown in FIG2 . From top to bottom, it includes a friction layer, a hydrophilic layer, an electrode layer, and a base layer. The specific preparation method is as follows:

[0081] (1) Preparation of the base layer: The PET film was placed in an ultrasonic cleaner filled with deionized water and cleaned at an ultrasonic power of 80 W for 10 minutes. The deionized water was then poured out, and acetone was added to the ultrasonic cleaner. The PET film was then ultrasonically cleaned in the acetone for 10 minutes. Finally, the film was removed and placed in a thermostat to dry.

[0082] (2) Preparing a hydrophilic layer on the substrate: treating the PET film with a PLASMA CLEANER instrument (RF power of 120 W, oxygen flow rate of 150 sccm) for 40 s, then immersing the treated PET film in a 1 wt% sodium dodecylbenzenesulfonate solution for 30 s, rinsing with deionized water for 30 s, and finally drying with nitrogen to obtain a hydrophilic PET layer;

[0083] 4 g of PVA particles and 40 g of water were placed in a 50 mL round-bottom flask, swelled in cold water, stirred thoroughly, placed in an oil bath, and heated at 90°C for 2 h to dissolve. Then, 5 mL of 10 wt% GA (glutaraldehyde) and 500 μL of dilute hydrochloric acid were added to obtain a GA-crosslinked PVA solution, i.e., the hydrophilic layer material.

[0084] The low-speed rotation speed was 900 r / min for 30 seconds, the high-speed rotation speed was 4000 r / min for 1 minute, and the film was dried at 80°C for 20 minutes to finally form a hydrophilic layer. The GA-crosslinked PVA solution was spin-coated on the hydrophilic PET film to obtain a hydrophilic layer-PET layer;

[0085] (3) Electrode layer preparation: Weigh 1 g of chitosan powder and dissolve it in 19 g of deionized water by heating to form a viscous liquid. Use an electronic balance to weigh a certain amount of conductive filler PEDOT:PSS, solvent ethylene glycol, and binder chitosan.

[0086] A certain amount of conductive filler, solvent and binder are placed in a beaker and stirred with a heatable magnetic stirrer at a temperature of 40-60°C for 1 hour to obtain ink.

[0087] An electronic balance was used to weigh 10%, 15%, and 20% of multi-walled carbon nanotubes and a dispersant (mass ratio 2:1). The multi-walled carbon nanotubes and dispersant were then added to the ink and ultrasonically dispersed for 15 minutes. The conductive ink was then heated and stirred evenly using a magnetic stirrer to obtain the conductive ink.

[0088] (4) Preparation of friction layer: Chitosan (CS) and polyethylene oxide (PEO) were weighed in a mass ratio of 1:1, mixed, and transferred to a reagent bottle. A 1% dilute acetic acid solution was added to obtain a 4% CS / PEO mixed solution. The mixed solution was transferred to a syringe for electrospinning. The electrospinning parameters (voltage, receiving distance, and propulsion speed) were 20 kV, 20 cm, and 0.5 mL / h, respectively. A 20-gauge needle was used to spin the CS / PEO nanofiber membrane. The CS / PEO nanofiber membrane was soaked in deionized water at room temperature for two days to remove the water-soluble PEO. The deionized water was replaced every four hours.

[0089] Prepare a 1 mol / L solution of sodium carbonate and sodium hydroxide (1:1, w / w). Immerse the PEO-removed CS nanofiber membrane in this solution and the protonated amino groups on the chitosan. Rinse with deionized water until the pH reaches neutral. Remove the membrane and dry it in a vacuum oven for 48 hours.

[0090] Conductive inks containing different mass fractions of carbon nanotubes were screen-printed on the hydrophilic layer-PET layer, and the prepared CS / PEO nanofiber membrane was combined with the electrode material screen-printed on the substrate layer by hot pressing to obtain a tactile sensor.

[0091] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. An array-type flexible tactile sensor, characterized in that: It comprises a plurality of arrayed flexible tactile sensor units, wherein the flexible tactile sensor units sequentially comprise a friction layer, a hydrophilic layer, an electrode layer and a substrate layer from top to bottom; The lower surface of the friction layer is a hydrophilic surface.

2. The array-type flexible tactile sensor according to claim 1, characterized in that: The lower surface of the friction layer is a hydrophilic surface modified by a surfactant.

3. The array-type flexible tactile sensor according to claim 2, characterized in that: The surfactant is selected from any one or more of sodium dodecyl sulfate, sodium diisobutyl sulfosuccinate, dodecyltrimethylammonium chloride or sodium dodecylbenzene sulfonate.

4. The array-type flexible tactile sensor according to claim 1, characterized in that: The friction layer is selected from any one or more of perfluoroethylene-propylene copolymer, polytetrafluoroethylene, polydimethylsiloxane, polyethylene, polyoxyethylene, polystyrene, polypropylene, polyvinyl chloride or polyvinylidene chloride; The hydrophilic layer is selected from any one or more of polyvinyl alcohol, polyimide or polyurethane.

5. The array-type flexible tactile sensor according to claim 1, characterized in that: The electrode layer is selected from any one of graphene, modified graphene, modified graphene biocomposite, carbon nanotube, modified carbon nanotube, modified carbon nanotube biocomposite or PEDOT:PSS; The base layer is selected from any one of polyurethane, polyimide, polyethylene terephthalate or polydimethylsiloxane.

6. The array-type flexible tactile sensor according to claim 5, characterized in that: The electrode layer is a carboxylated multi-walled carbon nanotube / chitosan composite material.

7. The method for preparing an array-type flexible tactile sensor according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) After the friction layer is subjected to hydrophilic modification treatment, a hydrophilic layer is prepared on its surface; (2) coating the electrode layer on the surface of the hydrophilic layer by screen printing; Wherein, the screen printing plate used in the screen printing method has an array structure; (3) Combining the substrate layer with the electrode layer to obtain the array-type flexible tactile sensor.

8. The preparation method according to claim 7, characterized in that: The hydrophilic modification specifically comprises: subjecting the friction layer to oxygen plasma treatment and then further subjecting the friction layer to surfactant treatment.

9. The preparation method according to claim 7, characterized in that: The radio frequency power of the oxygen plasma treatment is 100-130 W, the time is 30-60 s, and the oxygen flow rate is 120-160 sccm.

10. A tactile perception system, characterized in that: The invention comprises the array-type flexible tactile sensor according to any one of claims 1 to 6 or the array-type flexible tactile sensor prepared by the preparation method according to any one of claims 7 to 9.

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