Surface microstructure flexible substrate graphene fiber material piezoresistive-triboelectric bimodal tactile sensor based on bionic principle

Abstract

The invention provides a tactile sensor and application thereof based on tactile perception system bionics, and relates to the technical field of sensors. The touch sensor provided by the invention comprises a microstructure substrate, a laser-induced graphene fiber layer and a polyimide layer. Wherein the substrate is mainly used for bearing the response material, constructing a fluctuating array and increasing the contact area; the laser-induced graphene fiber layer is vertically arranged nano microfilaments, has a large contact area and a rough surface, is used as a response center for detecting a mechanical signal and identifying a material, and grows on the polyimide substrate; the polyimide layer serves as a friction layer corresponding to the laser-induced graphene fiber layer and induces different types of charges, and the polyimide layer and the laser-induced graphene fiber layer are fixed to the substrate and play a role in external connection. The sensor provided by the invention can detect and distinguish different tiny mechanical signals, can distinguish objects made of different materials, can perform multi-modal object detection, is high in detection sensitivity, and avoids the problems of low detection precision, single detection signal and inaccurate result in a traditional tactile sensor.

Description

Technical Field

[0001] The present invention relates to the field of flexible tactile sensors, and in particular to a multimodal sensor for detecting tiny forces and identifying object materials and shapes. Background Art

[0002] When objects come into contact with the skin, organisms can sense pressure and material, and infer their material properties. Today, the development of functional electronics has revealed strategies for machines to achieve some of the tactile functions of human skin. For example, electronic skin and flexible sensors have been implemented in robots and wearable health monitoring devices to detect environmental changes such as strain, vibration, and applied pressure. An important prospect for simulating the characteristics of human skin is the development of multifunctional sensors, especially for inferring material properties. Graphene, as a two-dimensional material, has good conductivity, is non-toxic, and is easy to prepare. The new laser-induced graphene technology can produce graphene at low cost and high efficiency, and has been widely used in tactile sensors.

[0003] Hair-like receptors play a crucial role in the tactile system of living organisms. For example, the tactile hairs on manatees' mouths help them locate prey; some insects use tactile hairs on their legs to capture prey and interact with their environment. While many tactile sensors can detect pressure, their accuracy, recognition range, and sensitivity are still significantly lower than those of natural organisms.

[0004] Therefore, it is necessary to optimize the performance of existing sensors and increase the recognition dimension by mimicking the hair-like receptors in the tactile system of organisms. Simultaneously achieving high-precision mechanical testing and material identification using the same device at low cost and high production speed requires biomimetic design and optimization of the sensor structure.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention aims to provide a tactile sensor device based on a biomimetic surface microstructure and a flexible graphene fiber substrate, and to provide a multi-layer, miniature sensing structure. This sensor is used to detect and identify minute forces and distinguish materials. The multi-layer microstructure is used to enhance sensing performance and enable multi-signal detection to increase detection reliability. To achieve this objective, the present invention employs the following technical solutions:

[0007] A tactile sensor characterized by being prepared from dual-microstructured graphene fibers obtained by secondary CO2 laser irradiation of a commercial polyimide film. The flexible tactile sensor comprises a flexible microstructured substrate, a graphene fiber layer, and a spacer layer. The flexible microstructured substrate is a polyimide film with a surface that has been initially microstructured by a CO2 laser and has a linear array of undulating lines with a spacing of 140-150 μm. The laser-induced graphene fiber layer is composed of a vertically aligned nanowire array prepared by secondary CO2 laser irradiation of the flexible microstructured substrate. The graphene fiber array is orderly distributed on the surface of the flexible microstructured substrate, with a single wire diameter of 150-200 nm. The wire height is 100-150 μm, and the array wire spacing is 140-150 μm. The flexible microstructured substrate was treated with CO2 laser irradiation to create an undulating linear array structure. A 1mm-thick, high-adhesion PET tape was applied to the surrounding laser-induced graphene fiber layer and to the untreated area of ​​the flexible substrate. A copper wire was connected to the laser-induced graphene fiber layer, adhered beneath the barrier layer, and grounded at its other end. The voltage variation across the copper wire was primarily influenced by the force applied to the graphene fiber layer and the material of the object it was in contact with.

[0008] A method for preparing a tactile sensor device based on a biomimetic surface microstructure using a flexible graphene fiber substrate is described. The method comprises the following steps: first, designing a rectangular pattern with a line width of 140-150 μm and an area of ​​1 cm × 2 cm, and then irradiating a commercial polyimide film cleaned with anhydrous ethanol with a CO2 laser at a wavelength of 10.6 μm at a power of 9-12 W, a line spacing of 100-150 μm, a line speed of 300-500 mm / s, and a frequency of 500-1500 Hz. This produces a flexible microstructure substrate with the same specifications. Using this substrate, the laser parameters are then changed to a power of 15.5-19.5 W, a line spacing of 100-150 μm, a line speed of 300-500 mm / s, and a frequency of 2000-4000 Hz, and the substrate is irradiated again, producing a graphene fiber layer with an area of ​​1 cm × 2 cm and a line width of 140-150 μm. A high-viscosity PET tape was attached as a space barrier layer around the laser-induced graphene fiber layer to obtain a tactile sensor device with a surface microstructure and a flexible substrate graphene fiber material based on the bionic principle.

[0009] The working principle of the present invention is:

[0010] A biomimetic tactile sensor based on a flexible graphene fiber substrate with a microstructured surface, when pressed, generates friction between the graphene fiber layer and the contact material surface, generating electric charge. The amount of frictional charge varies depending on the pressure. Greater pressure increases the contact area between the material and the device, and the more graphene fibers affected by friction, the greater the generated triboelectric charge, and the corresponding voltage. Due to the varying ability of different materials to gain or lose electrons, the charge generated by friction with the graphene fiber layer also varies, and the corresponding voltage also varies. The flexible substrate with a high- and low-relief microstructure, combined with an array of vertically aligned graphene fibers, significantly increases the contact area with the contact material, generating more triboelectric charge than other materials, resulting in a lower detection limit and greater sensitivity. Furthermore, due to the vertically aligned graphene fibers on the microstructured substrate, when the sensor is applied to an object, fibers come into contact, reducing electrical resistance and enabling measurement of the object's curvature.

[0011] Utilizing a biomimetic surface microstructured flexible graphene fiber-based tactile sensor, the sensor can detect subtle pressure changes and the materials of different contact objects by monitoring the corresponding voltage output under different pressures and contact materials. Furthermore, the use of laser-induced graphene fiber material reduces costs while effectively increasing the sensor's detection accuracy, meeting the needs of subtle force detection and material identification.

[0012] In summary, the benefits of the present invention lie in providing a tactile sensor device based on a biomimetic surface microstructure and a flexible graphene fiber substrate, as well as a multi-layer, miniature sensing structure. By analyzing the output of different voltage signals, it can be used to detect and identify small forces and distinguish between different materials. Furthermore, the biomimetic design of the multi-layer microstructure and graphene fibers reduces costs while effectively improving sensor performance and multi-dimensional detection, thereby increasing detection reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 This is the preparation process of the main part of the tactile sensor based on the surface microstructure flexible substrate graphene fiber material based on the bionic principle.

[0015] Figure 2The structure of a tactile sensor made of graphene fiber material with a surface microstructure and flexible substrate based on bionic principles.

[0016] Figure 3 This is the sensing principle and wiring diagram of the tactile sensor based on the bionic principle and the surface microstructure flexible substrate graphene fiber material.

[0017] Figure 4 These are SEM images of the flexible microstructure substrate obtained after a single laser irradiation in Example 1 of the present invention and an SEM image of the graphene fiber array grown on the substrate surface obtained after a secondary laser irradiation.

[0018] Figure 5 This is a force-electric test diagram of the tactile sensor with a surface microstructured flexible substrate graphene fiber material based on the bionic principle in Example 1 of the present invention, which is applied to the detection and identification of small forces (0.1-0.5N) under contact with the same material (polyimide), reflecting the change in voltage of the device under different small pressures.

[0019] Figure 6 This is a voltage test diagram of the surface microstructure flexible substrate graphene fiber material tactile sensor based on the bionic principle in Example 1 of the present invention, which is applied to distinguish different materials under the same pressure (5N), reflecting the difference in voltage when the device is in contact with different materials.

[0020] Figure 7 This is a curve showing the change in resistance over time of the tactile sensor made of graphene fiber material with a surface microstructure and a flexible substrate based on the bionic principle in Example 1 of the present invention when the bending angle is 90°. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0022] This embodiment provides a tactile sensor based on a biomimetic principle and a flexible graphene fiber substrate with a surface microstructure for identifying micromechanical signals and distinguishing object materials. The tactile sensor is mounted on a mechanical testing platform and is specifically implemented as follows:

[0023] (1) Preparation of flexible microstructure substrates

[0024] Using EZCAD, geometric patterns with horizontal fill and a line width of 150 μm, including but not limited to circles, rectangles, and diamonds, were drawn, with a total area of ​​1 cm × 2 cm. A commercial polyimide film, ultrasonically cleaned in anhydrous ethanol for 5 minutes and then attached to a glass slide with double-sided tape, was subjected to a single irradiation at a power of 9-12 W, a line speed of 300-500 mm / s, and a frequency of 500-1500 Hz. This irradiation produced a flexible substrate with a microstructure array with a concave-convex structure and a line spacing of 150 μm.

[0025] (2) Preparation of graphene fiber layer and assembly of sensor

[0026] Keeping the pattern filling mode, line width and area drawn by EZCAD in step (1) unchanged, the microstructure flexible substrate prepared in step (1) is subjected to secondary irradiation under the conditions of power 15.5-19.5W, line speed 300-500mm / s and frequency 2000-4000Hz, as shown in FIG. Figure 1 As shown. A graphene fiber layer with a concave-convex microstructure is obtained. It is peeled off from the glass sheet. A high-viscosity PET tape is attached to the area around the graphene fiber layer and the area not treated by the laser in the flexible substrate to form a space barrier layer. The copper wire is connected to the laser-induced graphene fiber layer and adhered under the space barrier layer. The specific structure of the device is shown as follows: Figure 2 .

[0027] (3) Application of micro-force detection, material identification, and strain detection

[0028] The surface microstructure flexible substrate graphene fiber material tactile sensor based on the bionic principle prepared in step (2) is mounted on a mechanical test platform, and the device is connected to Keithley6514 and grounded through the lead copper wire to detect the voltage change of the graphene fiber layer affected by pressure and the material gaining and losing electrons, such as Figure 3 As shown, it can realize the detection of micro pressure and the identification of materials.

[0029] In order to determine the microstructure of the flexible microstructure substrate and the graphene fiber layer, the morphology was observed by SEM. Figure 4 As shown in (a), the undulating structure of the flexible microstructure substrate obtained by the initial laser treatment is relatively uniform and the degree of arraying is considerable. Figure 4 As shown in (b), the graphene fiber layer obtained by secondary laser processing is obviously fiberized, and a clearly undulating array can be observed, which greatly increases the contact area of ​​the device while constructing a conductive layer.

[0030] The tactile sensor made of graphene fiber material with a surface microstructure and flexible substrate based on biomimetic principle and polyimide as contact material was placed on an electric displacement stage to test its electromechanical performance. The results are as follows: Figure 5 As shown in the figure, when subjected to pressures of 0.1N, 0.2N, 0.3N, 0.4N, and 0.5N respectively, it can be seen that the device has sensitive detection capabilities for tiny pressures and can distinguish five different pressures well.

[0031] Similarly, keep the pressure at 5N, change the material in contact with the device, and test the ability to distinguish materials. The results are as follows: Figure 6As shown, when eight materials including PTFE, PDMS, PVC, PC, PI, PEEK, paper, and rubber were used in contact with the device, the voltage values ​​output by the device were significantly different due to the differences in electronegativity between the materials. This shows that the device has excellent recognition capabilities for different materials.

[0032] Since the device has a graphene fiber array arranged vertically on the surface of the undulating microstructure, when the device bends inward, adjacent graphene fibers contact each other, and the resistance decreases accordingly; similarly, when the device returns to its initial state from bending, adjacent graphene fibers separate and the resistance increases, such as Figure 7 As shown in Figure 2, it can be observed that a significant resistance change occurs before and after the device is deformed, indicating that the device has the ability to detect curvature.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tactile sensor, characterized in that: The sensor includes a flexible microstructure substrate, a laser-induced graphene fiber layer, and a space barrier layer; the flexible microstructure substrate is a polyimide film whose surface is treated with CO2 laser microstructuring; the laser-induced graphene fiber layer is vertically arranged nanowires prepared by irradiating a polyimide substrate with CO2 laser; and the laser-induced graphene fiber layer is grown on the flexible microstructure substrate.

2. The tactile sensor according to claim 1, wherein The graphene microfilaments are neatly distributed in rows on a polyimide substrate, and the diameter of a single microfilament is 150-200 nm; preferably, the height of the microfilaments is 100-150 μm; preferably, the spacing between adjacent microfilaments in each row is 140-150 μm.

3. The tactile sensor according to claim 1, wherein The laser-induced graphene layer is prepared by a laser-induced graphene method, and the geometric shape of the laser-induced graphene layer includes but is not limited to a circle, a rectangle, a diamond, etc.

4. The tactile sensor according to claim 1, wherein The material of the flexible microstructure substrate is selected from commercial polyimide films.

5. The tactile sensor according to claim 1, wherein The flexible microstructure substrate is irradiated by CO2 laser to obtain an undulating line array structure with a line spacing of 140-150 μm.

6. The method for preparing the laser-induced graphene layer and the polyimide layer of the tactile sensor according to claim 1, comprising the following steps: Step 1: Clean the commercial polyimide film with anhydrous ethanol and dry it, and then stick the cleaned commercial polyimide film on the surface of the glass slide with double-sided tape; Step 2: The polyimide film prepared in step 1 is exposed to a CO2 laser with a wavelength of 10.6 μm for a single irradiation to form a flexible microstructure substrate with high and low undulations; Step 3: Place the polyimide film in step 2 under a CO2 laser with a wavelength of 10.6 μm for single irradiation again, and peel it off from the glass sheet to obtain a laser-induced graphene layer grown on the polyimide substrate.

7. The method for preparing the laser-induced graphene layer and the polyimide layer of the tactile sensor according to claim 6, characterized in that: The laser parameters for step 2 are: power 9-12 W, line spacing 100-150 μm, line speed 300-500 mm / s, frequency 500-1500 Hz. The laser parameters for step 3 are: power 15.5-19.5 W, line spacing 100-150 μm, line speed 300-500 mm / s, frequency 2000-4000 Hz.

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