A Graphene Flexible Pressure Sensor with Bionic Micro-Nano Structure and Its Preparation Method

Abstract

The present invention discloses a graphene flexible pressure sensor with a bionic micro-nano structure and a preparation method thereof. The flexible pressure sensor includes a flexible substrate, an intermediate sensing layer, and an external lead wire; the flexible substrate is made of ECO FLEX material; the intermediate sensing layer is a graphene conductive polymer film modified with a bionic structure; both ends of the graphene conductive polymer film of the sensor are respectively bonded to a flexible copper-clad organic polymer material film, and conductive silver paste is used at the bonding part; the graphene flexible sensor is encapsulated by the way that two graphene conductive polymer film sensing layers are in face-to-face contact, and ECO FLEX material is used as a flexible substrate to provide support. The present invention realizes a bionic surface structure graphene layer similar to taro leaves induced by laser through exploring a laser processing technology, and the prepared flexible pressure sensor simultaneously has excellent hydrophobic, anti-serum, and anti-sweat properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and particularly relates to a graphene flexible pressure sensor with a bionic micro-nano structure and a preparation method thereof. Background Art

[0002] With the increasing demands for artificial intelligence, Internet of Things technology, electronic chips, etc., advanced sensors, as one of the most critical sensing components, have received more and more attention. Flexible sensing devices have become increasingly important for health monitoring and management because they can be closely laminated on human organs (such as the skin) for minimally invasive procedures and for continuous, real-time, and persistent data collection to achieve dynamic tracking of the body state. Flexible pressure sensors have received extensive scientific research attention due to their extensive applications in flexible wearable electronics such as physiological condition detection and medical diagnosis.

[0003] Classified by the sensing mechanism of the sensor, flexible pressure sensors are mainly divided into three types: resistive, capacitive, and piezoelectric. Among them, resistive flexible pressure sensors have been widely studied due to their advantages of high sensitivity, fast response, and low response hysteresis. Flexible pressure sensors mainly consist of a conductor for realizing good electrical signal sensing and a flexible substrate for providing support and protection. Nanoconductor materials such as nanoparticles and nanotubes are considered the core materials for manufacturing flexible pressure sensors. However, various chemical substances are used in the traditional sensor preparation process, which is prone to environmental pollution. In addition, due to the high complexity of life scenarios and usage environments, the durability and sensitivity of various flexible pressure sensors still need to be improved. The performance of ordinary flexible capacitive or resistive pressure sensors is often insufficient to meet the requirements of practical applications. On the other hand, the problem of high traditional preparation cost and inability to achieve large-scale production. Improving the performance of flexible pressure sensors mainly relies on microstructural modification of the conductive sensing layer or flexible electrode, but the work of constructing microstructures usually uses complex and costly methods such as chemical modification.

[0004] Carbon nanoparticles such as graphene and carbon black have been widely used in the manufacture of flexible devices due to their advantages of high conductivity and low cost. Moreover, graphene manufacturing under laser assistance provides a simple and rapid method for the preparation and patterning modification of graphene due to its advantages of large-area preparation and maskless. Compared with photolithography manufacturing and chemical method manufacturing, laser-assisted graphene manufacturing has higher economic benefits.

[0005] The research on the performance of flexible sensors is mainly carried out by introducing microstructures to modify the conductive sensing layer of the sensor. Researchers have studied the preparation of bionic structure pressure sensors from butterfly scales, roses, and moth eye structures, etc. However, the performance of a single bionic structure is limited and cannot improve the erosion resistance and liquid resistance of the sensor. Summary of the Invention

[0006] In view of the problems existing in the prior art, the primary object of the present invention is to provide a graphene flexible pressure sensor with a bionic micro-nano structure. The flexible pressure sensor has a simple preparation method, high economic efficiency, and strong liquid resistance, and can achieve high-sensitivity and stable pressure response testing.

[0007] The second object of the present invention is to provide a preparation method of a graphene flexible pressure sensor with a bionic micro-nano structure. Inspired by the superhydrophobic surface structure of taro leaves in nature, from the perspective of bionics, through the bionic structure design of the flexible pressure sensor and the use of laser-induced graphene materials, a flexible pressure sensor with rapid preparation, low cost, corrosion resistance, and high sensitivity is prepared.

[0008] The primary object of the present invention is achieved by the following technical solutions:

[0009] A graphene flexible pressure sensor with a bionic micro-nano structure includes a flexible substrate, an intermediate sensing layer, and external connecting wires. The flexible substrate includes an upper flexible substrate and a lower flexible substrate, and the two ends of the intermediate sensing layer are connected with external connecting wires; the flexible substrate is made of ECO FLEX material; the intermediate sensing layer is a graphene conductive polymer film (CCP / LIG) modified by a bionic micro-nano structure; both ends of the graphene conductive polymer film (CCP / LIG) are bonded to a flexible copper-clad organic polymer material film (PI), and a conductive silver paste is used at the bonding part.

[0010] Furthermore, the graphene flexible pressure sensor is encapsulated by a method in which two graphene conductive polymer film (CCP / LIG) sensing layers are in face-to-face contact, and ECO FLEX is used as the flexible substrate to provide support.

[0011] Furthermore, the graphene conductive polymer film (CCP / LIG) is prepared by mixing graphene (LIG) generated by laser-induced polyimide and conductive carbon paste (CCP), and the mass content of LIG in the mixture is 3% - 9%.

[0012] Furthermore, the bionic micro-nano structure is the surface structure of taro leaves. The surface structure of taro leaves is a hexagonal nest-like cave. The hexagonal nest-like cave has elliptical papillae with an average diameter of 10 ± 1 μm. The surface of the elliptical papillae has nanoscale pins. Its surface hierarchical structure and the formed micro-structure cause surface superhydrophobicity, with a static contact angle of 159° ± 2° and a sliding angle of 30° ± 1°.

[0013] Further, the specific steps of modifying the intermediate sensing layer with the bionic structure are as follows: The surface structure of the taro leaf is transferred onto the graphene conductive polymer film (CCP / LIG) by using the template transfer method to form the graphene conductive polymer film (CCP / LIG) modified with the bionic structure.

[0014] The second object of the present invention is achieved by the following technical solution:

[0015] A preparation method of a graphene flexible pressure sensor with a bionic micro-nano structure, comprising the following steps:

[0016] (1) Obtain the surface microstructure of the taro leaf by using a SEM scanning electron microscope and set the working program of the laser engraving machine;

[0017] (2) Select the template material for the intermediate sensing layer, prepare the template material and perform pretreatment;

[0018] (3) Use the laser engraving method to etch the microstructure with the bionic surface morphology of the taro leaf on the intermediate sensing layer template to obtain the bionic sensing layer template;

[0019] (4) Prepare the conductive material graphene (LIG), and use the laser induction method to induce the generation of conductive material graphene (LIG) with different microscale on the flexible polyimide film (PI). The surface roughness and ablation depth of the sample are characterized by using a scanning electron microscope, a three-dimensional surface topography analyzer and Raman spectroscopy;

[0020] (5) Select the conductive carbon paste (CCP) as the auxiliary material, dissolve it in n-hexane, mix the conductive material graphene (LIG) with the conductive carbon paste (CCP), and obtain the graphene conductive polymer solution after dispersion, magnetic stirring and ultrasonic cleaning;

[0021] (6) Uniformly introduce the graphene conductive polymer solution described in step (5) into the bionic sensing layer template in step (3) for vacuum defoaming, heating to volatilize the organic solvent (n-hexane), cooling and solidifying, and peeling into a film; Obtain the graphene conductive polymer film (CCP / LIG) with a bionic micro-nano structure;

[0022] (7) Package by using two pieces of graphene conductive polymer films (CCP / LIG) with bionic micro-nano structures in a face-to-face contact manner. The two ends of the graphene conductive polymer film (CCP / LIG) are respectively bonded by using a flexible copper-clad organic polymer material film (PI), and the bonding part uses conductive silver paste; ECOFLEX is used as the flexible substrate to provide support to complete the packaging of the graphene flexible pressure sensor, and the graphene flexible pressure sensor with a bionic micro-nano structure is prepared.

[0023] Further, in the step (1), the taro leaves are specimens obtained from a botanical garden. Their surfaces have hexagonal nest-like cavities, inside which there are many elliptical papillae with an average diameter of 10 ± 1 μm. Using a relatively high SEM magnification, it can be found that many nano-scale stitches are evenly distributed on the surface of the elliptical papillae. The hierarchical structure and the formed micro-structure on its surface cause surface superhydrophobicity, with a static contact angle of 159° ± 2° and a sliding angle of 30° ± 1°. The model of the scanning electron microscope is MERLIN.

[0024] Further, in the step (2), the template material of the middle sensing layer is a polished aluminum alloy template with dimensions of 30 mm × 10 mm × 3 mm. The method for preparing the template material and performing pre-treatment is specifically as follows: conduct metallographic grinding and polishing, immerse it in an acidic rust remover for 4 - 6 minutes, then ultrasonically clean it with deionized water, acetone, and absolute ethanol, and finally dry it for standby.

[0025] Further, in the step (3), the laser instrument used in the laser engraving method is a multi-mode laser engraving machine (CLS8100), equipped with a diode-pumped Nd:YAG solid-state pulsed laser. Its output center wavelength is 1055 - 1070 nm, the maximum output power is 0 - 20 W, the repetition frequency is 0 - 50 kHz, the pulse duration is 100 - 200 ns, the focused diameter of the laser beam is 30 - 50 μm, and the repetition accuracy is ±2.5 μm.

[0026] Further, in the step (5), dissolving the conductive carbon paste (CCP) in n-hexane means dissolving the conductive carbon paste (CCP) in a n-hexane filler diluent, putting in a magnetic stir bar, placing the beaker under a magnetic stirrer, and performing magnetic stirring for 1 hour at a parameter of 750 r / min to dilute the conductive carbon paste (CCP); again performing magnetic stirring for 1 hour on the diluted conductive carbon paste (CCP) at a parameter of 750 r / min, then putting it into an ultrasonic cleaner and performing deep dispersion treatment at full power for 2 hours, and finally obtaining a uniformly dispersed graphene conductive polymer solution.

[0027] Further, in the step (5), the graphene conductive polymer solution is a mixture of laser-induced graphene (LIG) and conductive carbon paste (CCP), where the mass content of LIG in the mixture is 3% - 9%.

[0028] Further, in the step (6), the specific method for vacuum de-bubbling is to place the bionic sensing layer template into a small vacuum container and pump out the air therein to perform de-bubbling treatment through vacuum.

[0029] Further, in step (7), the size of the graphene conductive polymer film (CCP / LIG) with a bionic micro-nano structure is 30 mm × 10 mm; the encapsulation method is: encapsulation is carried out in a face-to-face contact manner, and both ends of the graphene conductive polymer film (CCP / LIG) are bonded with a flexible copper-clad organic polymer material film (PI), and conductive silver paste is used at the bonding part; ECOFLEX is used as a flexible substrate to provide support to complete the encapsulation of the graphene flexible pressure sensor.

[0030] The present invention has the following advantages and beneficial effects compared with the prior art:

[0031] (1) The graphene flexible pressure sensor with a bionic micro-nano structure prepared by the present invention includes a flexible substrate, an intermediate sensing layer, and an external lead; the flexible substrate is made of ECO FLEX material; the intermediate sensing layer is a graphene conductive polymer film (CCP / LIG) modified by a bionic structure; both ends of the sensor are bonded with a flexible copper-clad organic polymer material film (PI) by the graphene conductive polymer film (CCP / LIG), and conductive silver paste is used at the bonding part; the encapsulation of the graphene flexible sensor is carried out by a face-to-face contact method of two graphene conductive polymer film (CCP / LIG) sensing layers, and ECO FLEX is used as a flexible substrate to provide support; the flexible pressure sensor has excellent hydrophobic, antiserum, and anti-sweat properties.

[0032] (2) By using a laser-induced polyimide film (PI) to prepare high-quality graphene (LIG) with a bionic structure, the present invention has the advantage of one-step rapid preparation compared with the chemical vapor deposition method, and the preparation process is environmentally friendly and non-toxic;

[0033] (3) Inspired by the superhydrophobic structure of the taro leaf surface, a standardized bionic structure is designed during the preparation of high-quality graphene by laser-induced polyimide film, and the bionic structure is given by laser processing to make it have the surface function of super liquid-resistant self-cleaning; compared with surface modification methods such as chemical modification, it is more rapid and environmentally friendly;

[0034] (4) By introducing a bionic structure of taro leaf with a large aspect ratio into the conductive sensing layer of the flexible pressure sensor, the prepared multi-scale and large aspect ratio sensing layer can effectively improve the sensitivity of the sensor and endow it with the advantages of good wettability, high corrosion resistance, high cycle stability, and fast response speed. Brief Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the model of the flexible pressure sensor with a bionic micro-nano structure of the present invention;

[0036] Figure 2Wettability analysis diagram of the laser-induced graphene material with a bionic micro-nano structure of the present invention;

[0037] Figure 3 Schematic diagram of the preparation process of the flexible pressure sensor with a bionic micro-nano structure of the present invention;

[0038] Figure 4 Physical diagram of the flexible pressure sensor with a bionic micro-nano structure of the present invention;

[0039] Figure 5 During the test of the flexible pressure sensor with a bionic micro-nano structure prepared in Example 1, for templates processed with different laser fluxes, the change in the resistivity of the sensor;

[0040] Figure 6 During the test of the flexible pressure sensor with a bionic micro-nano structure prepared in Example 2, when tested at different frequencies, the change in the sensitivity of the sensor;

[0041] Figure 7 During the durability test of the flexible pressure sensor with a bionic micro-nano structure prepared in Example 2, when tested at the same frequency, the change in the sensitivity of the sensor;

[0042] Figure 8 Effect diagram of the response time and recovery time of the flexible pressure sensor prepared in Test Example 1;

[0043] Figure 9 During the test of the flexible pressure sensor prepared in Test Example 1, when tested at different frequencies, the change in the sensitivity of the flexible pressure sensor;

[0044] Figure 10 During the durability test of the flexible pressure sensor prepared in Test Example 1, when tested at the same frequency, the change in the sensitivity of the flexible pressure sensor;

[0045] Figure 11 Schematic diagram of the test process of the flexible pressure sensor;

[0046] Among them, flexible substrate 1, intermediate sensing layer 2, external connecting wire 3, polyimide film 4; unmodified graphene film 5; bionic taro leaf structure-modified laser-induced graphene 6; conductive carbon paste (CCP) 7; graphene (LIG) 8; graphene conductive polymer solution (CCP / LIG) 9; bionic intermediate sensing layer template 10; ECO FLEX flexible substrate 11. Detailed implementation manners

[0047] The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the implementation manners of the present invention are not limited thereto.

[0048] Figure 1Schematic diagram of the flexible pressure sensor model with the bionic taro leaf surface structure of the present invention. The flexible pressure sensor includes a flexible substrate, an intermediate sensing layer, and external wires. The two ends of the intermediate sensing layer are externally connected to the wires.

[0049] Figure 2 Wettability analysis diagram of the laser-induced graphene material with the bionic micro-nano structure of the present invention. It can be seen from Figure 2 that the penetration states of deionized water, artificial sweat, and serum on the surface of the initial polyimide film, and the contact angles are 71°, 78°, and 73° respectively; the contact angle values of the unmodified graphene film surface for water, artificial sweat, and serum are 138°, 130°, and 137° respectively; after being modified with the bionic taro leaf structure, the contact angle values of the laser-induced graphene material surface for water, artificial sweat, and serum are as high as 151.5°, 145°, and 149° respectively. Compared with the unmodified graphene film surface, the contact angles of water, artificial sweat, and serum on the surface of the bionically modified material increase by about 9.8%, 11.5%, and 8.1% respectively, indicating that its surface has excellent hydrophobic, anti-serum, and anti-sweat properties.

[0050] Figure 3 Schematic diagram of the preparation process of the flexible pressure sensor with the bionic micro-nano structure of the present invention.

[0051] Figure 4 Physical picture of the flexible pressure sensor with the bionic micro-nano structure of the present invention.

[0052] Example 1

[0053] A preparation method of a graphene flexible pressure sensor with a bionic micro-nano structure, comprising the following steps:

[0054] (1) Preliminary preparation: Obtain the microscopic structure of the taro leaf surface by using a SEM scanning electron microscope, and set the working program of the laser engraving machine; select the template material for the sensing layer, prepare the template material and carry out pretreatment;

[0055] (2) Preparation of the template material for the sensing layer: Use laser fluxes of 15.92 J·cm -2 , 31.85 J·cm -2 , 47.77 J·cm -2 , 55.73 J·cm -2 , 71.66 J·cm -2The laser engraving method etches microscopic structures with a biomimetic taro leaf surface topography on the sensing layer template to serve as a biomimetic sensing layer template; the material of the sensing layer template is a polished aluminum alloy template with dimensions of 30mm×10mm×3mm. Prepare the template material and perform pretreatment. The pretreatment method is metallographic grinding and polishing, immersion in an acidic rust remover for 4 - 6 minutes, then ultrasonic cleaning with deionized water, acetone, and absolute ethanol, and finally drying for standby;

[0056] (3) Preparation of flexible dielectric layer graphene thin film material: Use the laser-induced method to induce the generation of conductive materials (LIG) with different microscale on the flexible film; the method of using the laser-induced method to induce the generation of conductive materials (LIG) with different microscale on the flexible film is laser-induced graphene material. Use a scanning electron microscope, three-dimensional surface topography analyzer, Raman spectroscopy, etc. for characterization. Select conductive carbon paste (CCP) as an auxiliary material, dissolve it in n-hexane, mix the conductive material (LIG) with the conductive carbon paste (CCP), and after dispersion, magnetic stirring, and ultrasonic cleaning, obtain a conductive polymer solution (CCP / LIG), where the mass fraction of the conductive material (LIG) is 5%; uniformly introduce the above mixture solution into the biomimetic sensing layer template for vacuum defoaming, heating to volatilize the organic solvent (n-hexane), cooling and solidifying, and peeling and film-forming treatment; obtain a graphene conductive polymer film (CCP / LIG) with a biomimetic taro leaf micro-nano structure;

[0057] (4) Preparation of a graphene flexible pressure sensor with a biomimetic micro-nano structure by the template transfer method: The size of the graphene conductive polymer film (CCP / LIG) with a biomimetic taro leaf micro-nano structure is 30mm×10mm; the encapsulation method is: encapsulate by the face-to-face contact method, and both ends of the graphene conductive polymer film (CCP / LIG) are bonded with a flexible copper-clad PI film, and the bonding part uses conductive silver paste; ECOFLEX is used as a flexible substrate to provide support to complete the encapsulation of the graphene flexible pressure sensor.

[0058] Figure 5 In the test of the flexible pressure sensor with a biomimetic micro-nano structure prepared in this embodiment, for the templates processed with different laser fluxes, the sensor sensitivity changes, and as the laser flux increases, the sensor sensitivity improves.

[0059] Example 2

[0060] (1) Preliminary preparation: Use a SEM scanning electron microscope to obtain the microscopic structure of the taro leaf surface and set the working program of the laser engraving machine; select the sensing layer template material, prepare the template material and perform pretreatment;

[0061] (2) Preparation of the sensing layer template material: Use a laser flux of 71.66J·cm -2The laser engraving method etches a microstructure with a biomimetic taro leaf surface topography on the sensing layer template to serve as a biomimetic sensing layer template. The material of the sensing layer template is a polished aluminum alloy template with dimensions of 30 mm × 10 mm × 3 mm. Prepare the template material and perform pretreatment. The pretreatment method is metallographic grinding and polishing, immersion in an acidic rust remover for 4 - 6 minutes, then ultrasonic cleaning with deionized water, acetone, and absolute ethanol, and finally drying for standby.

[0062] (3) Preparation of graphene thin film material for the flexible dielectric layer: Use the laser-induced method to induce the generation of conductive materials (LIG) with different microscale on the flexible film; the method of using the laser-induced method to induce the generation of conductive materials (LIG) with different microscale on the flexible film is the laser-induced graphene material. Characterize it using a scanning electron microscope, a three-dimensional surface topography analyzer, Raman spectroscopy, etc. Select conductive carbon paste (CCP) as the auxiliary material, dissolve it in n-hexane, mix the conductive material (LIG) with the conductive carbon paste (CCP), and after dispersion, magnetic stirring, and ultrasonic cleaning, obtain a conductive polymer solution (CCP / LIG), where the mass fraction of the conductive material (LIG) is 3%, 5%, 7%, 9%; uniformly introduce the above mixture solution into the biomimetic sensing layer template for vacuum degassing, heating to volatilize the organic solvent (n-hexane), cooling and solidifying, and peeling to form a film; obtain a graphene conductive polymer film (CCP / LIG) with a biomimetic taro leaf micro-nano structure.

[0063] (4) Preparation of a graphene flexible pressure sensor with a biomimetic micro-nano structure by the template transfer method: The size of the graphene conductive polymer film (CCP / LIG) with a biomimetic taro leaf micro-nano structure is 30 mm × 10 mm; the encapsulation method is: encapsulate by the face-to-face contact method, bond the two ends of the graphene conductive polymer film (CCP / LIG) with a flexible copper-clad PI film respectively, and use conductive silver paste at the bonding part; Use ECOFLEX as the flexible substrate to provide support to complete the encapsulation of the graphene flexible pressure sensor.

[0064] Figure 6 In the test of the flexible pressure sensor with a biomimetic micro-nano structure prepared in this example, when the content of different graphene (LIG) is different, the resistivity of the sensor changes. As the mass fraction of graphene (LIG) increases, the resistivity of the sensor shows a continuous decreasing trend.

[0065] Figure 7In the test of the flexible pressure sensor with a bionic micro-nano structure prepared in Example 2, when testing at different graphene (LIG) contents and different frequencies, the sensitivity of the sensor changes. When the mass fraction of graphene (LIG) reaches 5%, the sensor obtains the highest sensitivity. As the mass fraction of graphene (LIG) continues to increase, the conductivity of the sensor continues to increase, but the sensitivity of the sensor shows a downward trend. The higher the conductivity, the lower the sensitivity. At this time, the sensitivity and conductivity show a negative correlation.

[0066] Test Example 1

[0067] The sensing layer template processed with a laser fluence of 71.66 J·cm -2 and the sensor prepared with a 5% mass fraction of the conductive material (LIG) in the conductive polymer solution (CCP / LIG) were subjected to performance tests; Figure 11 It is a schematic diagram of the test process of the flexible pressure sensor.

[0068] Figure 8 It is the response time and recovery time effect diagram of the flexible pressure sensor prepared in Test Example 1. When a uniform load is applied, the response time of the sensor for each deformation maintains a high degree of consistency. At the same time, the response time reaches 86 ms, and the recovery time is 101 ms when the load is withdrawn. The difference between the response time and the recovery time is 15 ms. This is because the slight viscosity of ECO FLEX causes the two sensing layers of the sensor to not fully return to the initial contact state, resulting in this time difference.

[0069] Figure 9 In the test of the flexible pressure sensor prepared in Test Example 1, when testing at different frequencies, the sensitivity of the flexible pressure sensor changes. When the sensor is under a constant pressure of 10 kPa and affected by the same load at different frequencies, its sensitivity level maintains a high degree of consistency. At the same time, the response of the sensor at each frequency also maintains excellent stability, indicating that the sensor can avoid interference and perform detection work normally, and has good universality.

[0070] Figure 10In the durability test of the flexible pressure sensor prepared in Test Example 1, when tested at the same frequency, the sensitivity change of the flexible pressure sensor was measured. A cyclic loading-unloading test was performed on the sensor at a constant pressure of 10 kPa, and the sensor was tested at every 50 cycles as a test point. After 650 tests, the sensor still showed stable response characteristics, and the sensitivity did not change significantly, without attenuation. This indicates that the CCP / LIG flexible sensor with ECO FLEX as the flexible support substrate has a long working life and high stability during the working life. The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A graphene flexible pressure sensor with a bionic micro-nano structure, characterized in that, It includes a flexible substrate, an intermediate sensing layer, and external connecting wires. The flexible substrate includes an upper flexible substrate and a lower flexible substrate. The two ends of the intermediate sensing layer are connected with external connecting wires. The flexible substrate is made of ECO FLEX material. The intermediate sensing layer is a graphene conductive polymer film modified by a bionic micro-nano structure. The two ends of the graphene conductive polymer film are respectively bonded to a flexible copper-clad organic polymer material film, and conductive silver paste is used at the bonding part. The graphene conductive polymer film is prepared by mixing graphene generated by laser-induced polyimide with conductive carbon paste, and the mass content of LIG in the mixture is 3% - 9%. The bionic micro-nano structure is the surface structure of a taro leaf. The surface structure of the taro leaf is a hexagonal nest-like cave. The hexagonal nest-like cave has elliptical papillae with an average diameter of 10 ± 1 μm. The surface of the elliptical papillae has nano-scale stitches. Its surface hierarchical structure and formed micro-structure cause surface superhydrophobicity, with a static contact angle of 159° ± 2° and a sliding angle of 30° ± 1°.

2. The graphene flexible pressure sensor with a bionic micro-nano structure according to claim 1, wherein The graphene flexible pressure sensor is encapsulated by the method of face-to-face contact of two graphene conductive polymer film sensing layers, and ECO FLEX is used as the flexible substrate to provide support.

3. The graphene flexible pressure sensor with a bionic micro-nano structure according to claim 1, characterized in that, The specific step of modifying the intermediate sensing layer with a bionic structure is to transfer the surface structure of the taro leaf onto the graphene conductive polymer film by the template transfer method to form a graphene conductive polymer film modified by a bionic structure.

4. A preparation method of a graphene flexible pressure sensor with a bionic micro-nano structure according to any one of claims 1 to 3, characterized in that, It includes the following steps: (1) Use a SEM scanning electron microscope to obtain the surface microstructure of the taro leaf and set the working program of the laser engraving machine. (2) Select the template material for the intermediate sensing layer, prepare the template material and carry out pretreatment. (3) Use the laser engraving method to etch a microstructure with the surface morphology of a bionic taro leaf on the intermediate sensing layer template to obtain a bionic sensing layer template. (4) Prepare the conductive material graphene, and use the laser-induced method to induce conductive material graphene with different micro-scale on the flexible polyimide film. The surface roughness and ablation depth of the sample are characterized by a scanning electron microscope, a three-dimensional surface topography analyzer, and Raman spectroscopy. (5) Select conductive carbon paste as an auxiliary material, dissolve it in n-hexane, mix the conductive material graphene with the conductive carbon paste, and after dispersion, magnetic stirring, and ultrasonic cleaning, obtain a graphene conductive polymer solution. (6) Uniformly introduce the graphene conductive polymer solution described in step (5) into the bionic sensing layer template in step (3) for vacuum defoaming, heating to volatilize the organic solvent, cooling and solidifying, and peeling into a film treatment; obtain a graphene conductive polymer film with a bionic micro-nano structure. (7) Encapsulate by the method of face-to-face contact of two graphene conductive polymer films with bionic micro-nano structures. The two ends of the graphene conductive polymer film are respectively bonded with a flexible copper-clad organic polymer material film, and conductive silver paste is used at the bonding part. Use it as a flexible substrate to provide support to complete the encapsulation of the graphene flexible pressure sensor, and prepare a graphene flexible pressure sensor with a bionic micro-nano structure.

5. The preparation method of the graphene flexible pressure sensor with a bionic micro-nano structure according to claim 4, characterized in that, In step (2), the template material of the intermediate sensing layer is a polished aluminum alloy template with dimensions of 30 mm × 10 mm × 3 mm. The method for preparing the template material and performing pretreatment is as follows: subject it to metallographic grinding and polishing, immerse it in an acidic rust remover for 4 - 6 minutes, then ultrasonically clean it with deionized water, acetone, and absolute ethanol, and finally dry it for standby.

6. The preparation method of the graphene flexible pressure sensor with bionic micro-nano structure according to claim 4, characterized in that, In step (3), the laser instrument used in the laser engraving method is a multimode laser engraving machine equipped with a diode-pumped Nd:YAG solid-state pulsed laser. Its output center wavelength is 1055 - 1070 nm, the maximum output power is 0 - 20 W, the repetition frequency is 0 - 50 kHz, the pulse duration is 100 - 200 ns, the focused diameter of the laser beam is 30 - 50 μm, and the repetition accuracy is ±2.5 μm.

7. The preparation method of the graphene flexible pressure sensor with a bionic micro-nano structure according to claim 4, characterized in that, In step (5), dissolving the conductive carbon paste in n-hexane means dissolving the conductive carbon paste in a n-hexane filler diluent, adding a magnetic stir bar, placing the beaker under a magnetic stirrer, and performing magnetic stirring for 1 hour at a parameter of 750 r / min to dilute the conductive carbon paste. Again, perform magnetic stirring on the diluted conductive carbon paste for 1 hour at a parameter of 750 r / min, then place it in an ultrasonic cleaner and perform deep dispersion treatment at full power for 2 hours to finally obtain a uniformly dispersed graphene conductive polymer solution.

8. The preparation method of the graphene flexible pressure sensor with bionic micro-nano structure according to claim 4, characterized in that, In step (6), the specific method for vacuum defoaming is to place the bionic sensing layer template into a small vacuum container and evacuate the air therein for defoaming treatment by vacuum.

Images