Flexible pressure sensor based on biomimetic microstructure and preparation method and application thereof

Abstract

The application discloses a flexible pressure sensor based on a bionic microstructure and a preparation method and application thereof, relates to the technical field of flexible sensing, and comprises a flexible electrode layer, an intermediate fixing layer, a microstructure sensing layer and a packaging layer which are sequentially attached from bottom to top, wherein the flexible electrode layer comprises a film base material and an interdigital electrode, the interdigital electrode is prepared by printing conductive ink on the film base material, the intermediate fixing layer is provided with a notch in the center for placing the microstructure sensing layer, and the microstructure sensing layer comprises a bionic microstructure elastomer and a conductive layer on the outer surface of the bionic microstructure elastomer.The application has the performances of high sensitivity, wide detection range, fast response, low detection limit and long-term stability, and has wide application prospects in the fields of human health monitoring and tactile perception.

Description

Technical Field

[0001] This invention relates to the field of flexible sensing technology, specifically to a flexible pressure sensor based on biomimetic microstructures, its fabrication method, and its application. Background Technology

[0002] Advances in flexible electronics technology are driving the transformation of traditional rigid sensors into systems with biocompatibility, skin adaptability, and multifunctional integration, overcoming limitations in epidermal compatibility and surface adaptability. Flexible sensors can closely conform to various irregular surfaces, thus providing more precise sensing capabilities. These unique characteristics make them show broad application potential in wearable devices, medical monitoring, and robotic skin. Force sensing is a crucial sensing module for precise environmental interaction between humans and robots.

[0003] Currently, various types of flexible pressure sensors have been developed, covering piezoresistive, capacitive, piezoelectric, triboelectric, magnetic, and optical response mechanisms. Among them, piezoresistive pressure sensors have become a widely studied subject due to their high stability, simple structure, and ease of integration. Despite significant progress, key challenges remain in achieving efficient sensing (high sensitivity, wide monitoring range, and low detection limit) and stable response in flexible pressure sensors.

[0004] The microstructure morphology and distribution design of the sensing layer are key factors in improving the detection range and sensitivity of pressure sensors. Currently, microstructure design includes traditional geometric shapes (such as pyramids, columns, and porous structures) as well as biomimetic natural surface features (such as mimicking nacre, rose petals, lotus leaves, and cicada wings). However, traditionally reported single-gradient or single-arrangement microstructures often suffer from signal saturation defects under relatively small pressures, thus limiting the application scenarios of the devices. Furthermore, in the fabrication of microstructures, 3D printing technology offers high control precision and shape plasticity, enabling the accurate construction of complex geometric microstructures, and is one of the most commonly used and efficient processes. However, for the fabrication of complex flexible microstructures, traditional secondary or multiple template methods have inherent problems such as complex processes, demolding defects, and poor structural fidelity, which can easily lead to reduced device sensitivity and baseline drift.

[0005] Traditional spraying and metal mask processes often lead to heterogeneous interfacial resistance thickness distribution and significant conductivity differences between batches when fabricating interdigitated electrodes or high-precision electronic patterns. Furthermore, the weak interfacial bonding between the electrode material and the flexible substrate severely affects the stable signal output of the device. Therefore, these processes are generally insufficient for manufacturing high-volume, finely patterned electrodes. Consequently, a flexible pressure sensor based on biomimetic microstructures, its fabrication method, and its applications are proposed. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solution: a flexible pressure sensor based on a biomimetic microstructure, comprising a flexible electrode layer, an intermediate fixing layer, a microstructure sensing layer, and an encapsulation layer sequentially bonded from bottom to top. The flexible electrode layer includes a thin film substrate and interdigitated electrodes, which are prepared by printing conductive ink on the thin film substrate. The intermediate fixing layer has a notch in the center for placing the microstructure sensing layer. The microstructure sensing layer includes a biomimetic microstructure elastomer and a conductive layer on its outer surface. The encapsulation layer is used to wrap the intermediate fixing layer and the microstructure sensing layer. The biomimetic microstructure elastomer of the microstructure sensing layer has multiple snake-scale-like microstructure units with different tilt angles.

[0007] Preferably, the biomimetic microstructure elastomer of the microstructure sensing layer is provided with three snake-scale microstructure units with different tilt angles. The tilt angles of the three snake-scale microstructure units are 45°, 35° and 25°, respectively, and the heights are 443.7µm, 361.3µm and 263.9µm, respectively. The multiple snake-scale microstructure units are distributed in a cross pattern, and the three snake-scale microstructure units are arranged in a gradient.

[0008] Preferably, the encapsulation layer is made of polyimide tape with a thickness of 50–100 µm.

[0009] This invention also provides a method for fabricating a flexible pressure sensor based on a biomimetic microstructure, used to fabricate the flexible pressure sensor based on a biomimetic microstructure as described above, comprising the following steps:

[0010] Step 1: Clean the thin film substrate with deionized water and alcohol to remove surface impurities, and after natural drying, perform oxygen plasma treatment to enhance its surface hydrophilicity. Then, print conductive ink on the thin film substrate according to the preset electrode pattern to obtain a flexible electrode layer with interdigitated electrode structure.

[0011] Step 2: Cut a notch in the center of the pre-cut flexible film to place the microstructure sensing layer, thus obtaining the intermediate fixing layer;

[0012] Step 3: Directly construct the reverse model of the biomimetic microstructure elastomer, and prepare the reverse template with grooves through 3D printing technology. Immerse the reverse template completely in isopropanol solution for no less than 24 hours. After drying, add silicone rubber to its surface. After vacuum degassing and curing, the biomimetic microstructure elastomer can be obtained by peeling it off once.

[0013] Step 4: Clean the biomimetic microstructure elastomer with deionized water and alcohol in sequence to remove surface impurities, then treat the surface of the microstructure with oxygen plasma, and form a conductive layer by magnetron sputtering or spraying. Then place it in an oven at 50-70℃ and heat for 15-30 minutes to obtain a microstructure sensing layer with a biomimetic cross-tilted gradient structure.

[0014] Step 5: Using a layer-by-layer bonding method, place the interdigitated electrode face of the flexible electrode layer from Step 1 facing upwards, and then use square copper tape to bond the wires at both ends of the interdigitated electrode. Next, attach the intermediate fixing layer from Step 2 onto the flexible electrode layer, and then place the microstructure sensing layer from Step 4 into the notch in the center of the intermediate fixing layer, so that the conductive layer of the microstructure sensing layer is attached to the central area of ​​the interdigitated electrode. Finally, encapsulate the intermediate fixing layer and the microstructure sensing layer to obtain a flexible pressure sensor based on a biomimetic microstructure.

[0015] Preferably, the film substrate in step 1 is polyethylene terephthalate, and the conductive ink is one or a combination of several of MXene solution, carbon nanotube dispersion, PEDOT:PSS, or graphene conductive paste.

[0016] Preferably, the intermediate fixing layer in step 2 is a polyethylene terephthalate film with a thickness of 100-300 μm, and one side of the intermediate fixing layer is adhesive for face-to-face bonding with the flexible electrode layer.

[0017] Preferably, the target material for the magnetron sputtering process in step 4 is any one of silver, gold, copper, aluminum, platinum, or nickel; the material used in the spraying process in step 4 is any one or a combination of several of MXene, graphene, carbon nanotubes, silver nanowires, and copper nanowires.

[0018] This invention also provides the application of a flexible pressure sensor based on a biomimetic microstructure in human health monitoring and tactile sensing.

[0019] The present invention has the following beneficial effects:

[0020] The flexible pressure sensor based on biomimetic microstructure provided by this invention comprises, from bottom to top, a flexible electrode layer, an intermediate fixing layer, a microstructure sensing layer, and an encapsulation layer. This flexible pressure sensor has the characteristics of high sensitivity, wide detection range, fast response, low detection limit, and long-term stability, and has broad application prospects in fields such as human health monitoring and tactile perception. In particular, by combining conductive ink with microcircuit printing technology, high-precision and high-efficiency electrode printing can be achieved.

[0021] Inspired by the interlocking structure and distribution characteristics of snake scales, the biomimetic cross-tilted gradient microstructure constructed in this invention has the following advantages: (1) Compared with the traditional side-by-side structure layout, this snake scale-inspired cross-distribution structure can build more conductive contact units in the same sensing area; In the initial state, there is only local point contact between the microstructure sensing layer and the flexible electrode layer, so the interface resistance R0 is extremely high. Based on the dual effects of increased contact area and increased conductive path, when the external pressure increases, the ultra-dense conductive path of the microstructure sensing layer and the flexible electrode layer achieve complete contact, effectively enhancing the signal response capability of the device, resulting in a large signal response (ΔR). =R0-R, where R is the final resistance of the maximum pressure threshold); and this biomimetic ultra-dense structure distribution can effectively disperse pressure, avoiding local stress concentration caused by sparse and uneven distribution of contact areas in traditional structures; (2) The three-level gradient microstructure with synergistic bending deformation (i.e., three snake-scale microstructure units with different tilt angles) triggers electrode contact according to the gradient, effectively suppressing signal saturation and expanding the response range; Specifically, as the pressure increases, the first-level microstructure unit (45°) undergoes bending deformation, which in turn causes the second-level microstructure unit (35°) to contact with the interdigitated electrode, thereby compensating for the contact area of ​​the first-level microstructure unit (45°). In this process, the stress is no longer concentrated only on the first-level microstructure unit (45°), but is redistributed to the second-level microstructure unit (35°), effectively alleviating the compression saturation tendency of the first-level microstructure unit (45°). At this time, the conductive path and contact area of ​​the microstructure layer sensing layer and the flexible electrode layer are significantly increased. As pressure continues to increase, the cumulative effect of compression at different levels significantly improves the contact conductivity of the pressure-sensitive layer (microstructure sensing layer). That is, the level III microstructure unit (25°) and the level II microstructure unit (35°) have the same function, and their synergistic effect improves the compressibility of the microstructure sensing layer.

[0022] The microstructure sensing layer of this invention is prepared using a three-dimensional model constructed with reverse thinking, requiring only one molding process to prepare a highly perfect microstructure silicone film (bionic microstructure elastomer); in addition, the high precision of 3D printing ensures the consistency of microstructure preparation between different batches.

[0023] In this invention, the interdigital electrode is prepared using advanced microcircuit direct writing technology, which allows for flexible control of the electrical properties of the interdigital electrode by adjusting the printing parameters. Compared with traditional processes such as spraying and metal masking, this avoids problems such as material waste and uneven electrode distribution.

[0024] This invention introduces an intermediate fixing layer and bonds it to the flexible electrode layer to form a fixing module, which enables flexible replacement of the microstructure sensing unit on the flexible electrode layer frame; the intermediate fixing layer also serves to encapsulate and protect the interdigitated electrodes, preventing damage to the electrode structure during the assembly and replacement of the microstructure sensing layer. Attached Figure Description

[0025] Figure 1 A schematic diagram of the flexible pressure sensor structure based on biomimetic microstructure provided by the present invention;

[0026] Figure 2 A physical image of the flexible pressure sensor based on biomimetic microstructure provided by this invention;

[0027] Figure 3 This is a SEM image of the snake-scale-like microstructure unit of the flexible pressure sensor based on biomimetic microstructures of the present invention.

[0028] Figure 4 This is another SEM image of the snake-scale-like microstructure unit of the flexible pressure sensor based on biomimetic microstructure of the present invention;

[0029] Figure 5 This is a physical image of the microstructure sensing layer in this invention;

[0030] Figure 6 This is another physical image of the microstructure sensing layer in this invention;

[0031] Figure 7 This is a physical image of the flexible electrode layer in this invention;

[0032] Figure 8 This is a schematic diagram showing the structure and dimensions of the interdigitated electrode in this invention;

[0033] Figure 9 This is a schematic diagram of the fabrication method of the microstructure sensing layer in Embodiment 1 of the present invention;

[0034] Figure 10 This is a schematic diagram illustrating the working principle of the flexible pressure sensor based on biomimetic microstructure of the present invention;

[0035] Figure 11 This is the pressure testing platform for testing sensor performance provided in Embodiment 1 of the present invention;

[0036] Figure 12 The pressure-resistance curve of the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention;

[0037] Figure 13 This is a response time and recovery time diagram of the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention;

[0038] Figure 14 This is a diagram showing the dynamic response performance of the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention to weak stimuli.

[0039] Figure 15This is a test diagram of the long-term cyclic stability of the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention;

[0040] Figure 16 A schematic diagram illustrating how the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention can detect minute displacements of the muscles in a local area of ​​the wrist caused by the flexion and extension movements of the thumb when it is tightly wrapped around the wrist.

[0041] Figure 17 This is a schematic diagram of a flexible pressure sensor based on a biomimetic microstructure provided in Embodiment 1 of the present invention, which is attached to an arm muscle to capture minute pressure changes in the muscle when it is clenched and relaxed in real time.

[0042] Figure 18 This is a schematic diagram of the electrical signal change curve generated by the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention during the heel strike process due to contact.

[0043] Figure 19 This is a graph showing the change in electrical signal when a finger taps the flexible pressure sensor based on a biomimetic microstructure, as provided in Embodiment 1 of the present invention.

[0044] In the figure: 1, flexible electrode layer; 2, intermediate fixing layer; 3, microstructure sensing layer; 4, encapsulation layer. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0047] Example 1: As Figure 1 , Figure 3 , Figure 4 and Figure 8As shown, this embodiment provides a flexible pressure sensor based on a biomimetic microstructure, including a flexible electrode layer 1, an intermediate fixing layer 2, a microstructure sensing layer 3, and an encapsulation layer 4, which are sequentially bonded from bottom to top. The flexible electrode layer 1 includes a thin film substrate and interdigitated electrodes, which are fabricated by printing conductive ink on the thin film substrate. The intermediate fixing layer 2 has a notch in the center for placing the microstructure sensing layer 3. The microstructure sensing layer 3 includes a biomimetic microstructure elastomer and a conductive layer on its outer surface. The encapsulation layer 4 is used to encapsulate the intermediate fixing layer 2 and the microstructure sensing layer 3. The microstructure sensing layer 3 is based on the biomimetic microstructure elastomer substrate. The device is equipped with three different tilt angles of snake scale-like microstructure units (Level I, Level II, and Level III microstructure units). The tilt angles of the three types of snake scale-like microstructure units are 45°, 35°, and 25°, respectively, and the heights are 443.7µm, 361.3µm, and 263.9µm, respectively. The design inspiration of the snake scale-like microstructure units comes from the structure and distribution characteristics of snake scales. Multiple snake scale-like microstructure units are distributed in a cross pattern, and the three types of snake scale-like microstructure units are arranged in a gradient.

[0048] The biomimetic microstructure elastomer of the microstructure sensing layer 3 is composed of flexible polymer elastic material, and the material of the encapsulation layer 4 is polyimide tape.

[0049] This embodiment also provides a method for fabricating a flexible pressure sensor based on a biomimetic microstructure, which is used to fabricate the flexible pressure sensor based on a biomimetic microstructure as described above, and includes the following steps:

[0050] Step 1: The polyethylene terephthalate film substrate is cleaned with deionized water and alcohol to remove surface impurities. After natural drying, it is subjected to oxygen plasma treatment to enhance its surface hydrophilicity. Then, an MXene solution with a concentration of 75 mg / mL is printed on the film substrate according to the preset electrode pattern to obtain a flexible electrode layer 1 with an MXene interdigitated electrode structure.

[0051] Step 2: A 16mm × 16mm notch for placing the microstructure sensing layer 3 is laser-cut at the center of a pre-cut rectangular flexible film with a thickness of approximately 225µm, thus obtaining the intermediate fixing layer 2.

[0052] Step 3: Directly construct the reverse model of the biomimetic microstructure elastomer, and prepare the reverse template with grooves (for forming snake scale microstructure units) using 3D printing technology. Immerse the reverse template completely in isopropanol solution for no less than 24 hours. After drying, add silicone rubber (i.e., reinforced dimethyl liquid silicone, with a 1:1 ratio of A and B components) to its surface. After vacuum degassing and curing, the biomimetic microstructure elastomer can be obtained by peeling it off once.

[0053] Step 4: The biomimetic microstructure elastomer is cleaned with deionized water and alcohol in sequence to remove surface impurities. Then, the surface of the microstructure is treated with oxygen plasma and a conductive layer is formed on the surface of the biomimetic microstructure elastomer by magnetron sputtering with a silver target under an argon atmosphere. Then, it is placed in an oven at 50-70℃ and heated for 15-30 minutes to obtain the microstructure sensing layer 3 with a biomimetic cross-tilted gradient structure.

[0054] Step 5: Using a layer-by-layer bonding method, place the MXene interdigital electrode face of the flexible electrode layer 1 from Step 1 facing upwards, and then use square copper tape to bond the wires at both ends of the interdigital electrode. Next, attach the intermediate fixing layer 2 from Step 2 onto the flexible electrode layer 1, and then place the microstructure sensing layer 3 from Step 4 into the notch in the center of the intermediate fixing layer 2, so that the silver metal electrode layer (i.e., conductive layer) of the microstructure sensing layer 3 is bonded to the central area of ​​the MXene interdigital electrode. Finally, encapsulate the intermediate fixing layer 2 and the microstructure sensing layer 3 with polyimide tape to obtain a flexible pressure sensor based on a biomimetic microstructure.

[0055] In step 2, the intermediate fixing layer 2 is a polyethylene terephthalate film, and one side of the intermediate fixing layer 2 is adhesive for face-to-face bonding with the flexible electrode layer 1; the encapsulation layer 4 is made of polyimide tape with a thickness of approximately 55µm; the design inspiration of the snake scale microstructure unit comes from the interlocking structure and distribution characteristics of snake scales. After structural optimization design, a cross-tilted gradient biomimetic microstructure elastomer is prepared by template method. The overall size of the biomimetic microstructure elastomer is approximately 15mm×15mm, and its base thickness is approximately 500µm, containing a total of 885 snake scale microstructure units; the overall size and base thickness of the biomimetic microstructure elastomer are achieved by adjusting the size of the unit microgrooves and the overall groove thickness in the 3D printing template.

[0056] like Figure 2 As shown, the pressure sensor prepared in this embodiment has the characteristics of flexibility and ultrathinness.

[0057] like Figure 3 and Figure 4 As shown, SEM images characterize the morphology of the biomimetic microstructure elastomer prepared by the template method. It can be seen that the microstructure is composed of snake-scale-like microstructure units arranged in a cross pattern with three different tilt angles (45°, 35° and 25°). The heights of the snake-scale-like microstructure units with the three different tilt angles are 443.7µm, 361.3µm and 263.9µm, respectively. The snake-scale-like microstructure units prepared by the single template method have a stable bond with the substrate of the biomimetic microstructure elastomer.

[0058] like Figure 5 and Figure 6As shown, the sensing area of ​​the microstructure sensing layer 3 prepared in this embodiment is about 2.25 cm², and it is covered with an ultra-high density array of sensing points (about 393 points / cm²). The silicone rubber film used has excellent flexibility and elasticity.

[0059] like Figure 7 The image shown is a physical diagram of the flexible electrode layer 1 prepared in step 1 of this embodiment. It can be seen that the MXene interdigitated electrodes printed on the polyethylene terephthalate film substrate have uniform surface distribution characteristics and an electrode thickness of about 10µm. At the same time, MXene and the polyethylene terephthalate substrate exhibit good bonding and stability.

[0060] like Figure 8 The diagram shows the printed MXene interdigitated electrode structure and dimensions in this embodiment. The total length of the electrode is 37mm and the total height is 15mm. The middle part is formed by two interlaced "finger teeth" to create a sensing area. This design with a large finger width and a small gap (1mm) can significantly increase the effective electrode surface area, thereby enhancing the electric field distribution and sensitivity.

[0061] like Figure 9 The diagram illustrates the fabrication method of the microstructure sensing layer 3 in this embodiment. By constructing a reverse model of the target microstructure using a reverse design approach, a highly flat biomimetic microstructure elastomer can be obtained with only one molding process. It should be noted that, to facilitate the smooth peeling of the silicone rubber from the resin mold, the printed reverse structure resin template is pre-immersed in isopropanol for at least 24 hours. The resulting biomimetic microstructure elastomer is then subjected to oxygen plasma treatment, and a conductive layer is formed on its surface.

[0062] like Figure 10 The diagram shown illustrates the working principle of the flexible pressure sensor provided by this invention. Based on the piezoresistive effect, since the contact area is negatively correlated with the device resistance, an increase in pressure will cause the contact area between the microstructure sensing layer 3 and the flexible electrode layer 1 to gradually increase (e.g., ...). Figure 10The process proceeds from A0 to A1 to A2, thereby reducing the total resistance of the sensing unit. Initially, there is only local point contact between the microstructure sensing layer 3 and the flexible electrode layer 1, resulting in extremely high interface resistance. As pressure is applied, the Level I microstructure unit (45°) undergoes bending deformation, which triggers the Level II microstructure unit (35°) to contact the interdigitated electrode, compensating for the contact area. During this process, the pressure stress is no longer concentrated solely on the Level I microstructure unit but is distributed to the Level II microstructure unit, effectively suppressing the signal saturation tendency of the Level I microstructure unit. This compression process is based on the dual effects of increased contact area and increased conductive pathways between the microstructure sensing layer 3 and the flexible electrode layer 1. As the pressure continues to increase, the superposition of the hierarchical compression effect significantly enhances the contact conductivity of the pressure-sensitive layer (microstructure sensing layer 3). Specifically, the Level III microstructure unit (25°) plays the same role as the Level II microstructure unit, and their synergistic effect improves the compressibility of the pressure-sensitive layer, thereby effectively avoiding the compression saturation phenomenon of the Level I microstructure unit. Furthermore, when pressure is applied to the sensor surface, the ultra-dense distribution of the cross-tilted gradient biomimetic structure proposed in this invention can effectively disperse the pressure, avoiding the local stress concentration phenomenon caused by the sparse and uneven distribution of the contact area in the traditional single side-by-side structure.

[0063] like Figure 11 As shown, this is a pressure testing platform used to test the sensing performance of sensors. The platform consists of a computer, a multimeter, a force gauge, an electric displacement stage, and a displacement controller adapted to it.

[0064] like Figure 12 The figure shows the pressure-resistance curve of the biomimetic pressure sensor prepared in this embodiment. It can be seen that the sensor exhibits a sensitivity as high as 2.116 kPa⁻¹ within a pressure range below 44.4 kPa. During compression, the cross-tilted gradient structure of the sensing layer (i.e., the microstructure sensing layer 3) exhibits a gradual bending characteristic from top to bottom, forming continuous contact with the MXene electrode layer (i.e., the flexible electrode layer 1). This biomimetic microstructure design strategy based on the synergistic bending effect effectively optimizes the current transmission characteristics, enabling the pressure sensor to have a pressure detection range as high as 511.11 kPa.

[0065] like Figure 13 The diagram shows the response and recovery times of the biomimetic pressure sensor prepared in this embodiment. It can be seen that it exhibits rapid response and recovery times (8ms / 76ms) under external pressure stimulation, demonstrating a stimulus response capability comparable to human skin. This performance stems from the high elasticity of the microstructure layer (i.e., microstructure sensing layer 3), which enables rapid compression-rebound cycles during pressure loading / unloading and ensures high-fidelity transmission of dynamic pressure signals.

[0066] like Figure 14As shown, the pressure sensor prepared in this embodiment exhibits dynamic response performance to weak stimuli, demonstrating that it can respond quickly and accurately to the signal generated when a drop of water (approximately 35 mg) falls, indicating that the sensor can accurately sense weak signal changes at high resolution.

[0067] like Figure 15 The figure shows the cyclic durability test results of the biomimetic pressure sensor prepared in this embodiment under a relative pressure of 45 kPa. It can be seen that the sensor's signal output curve remained basically consistent during 5000 load-unload cycles, thus verifying its good durability and signal output stability.

[0068] like Figure 16 As shown, when the pressure sensor prepared in this embodiment is wrapped around the wrist, it can sensitively detect the minute displacement changes of the muscles in the local area of ​​the wrist caused by the flexion and extension of the thumb, thus achieving high sensitivity to weak stimuli.

[0069] like Figure 17 As shown, the pressure sensor prepared in this embodiment is attached to the arm muscle to capture minute pressure changes in the muscle when it is clenched and relaxed in real time, demonstrating its significant application potential in fields such as motion analysis and rehabilitation training.

[0070] Detecting pressure on the human foot requires a sensor with a wide detection range, such as... Figure 18 As shown, the sensor prepared in this embodiment is installed at the heel of the insole, which can accurately capture the changes in electrical signals caused by the sensor contact point when the heel strikes the ground, and is used to analyze gait and walking posture.

[0071] like Figure 19 As shown, the pressure sensor prepared in this embodiment is attached to the surface of the mouse, which can achieve sensitive and rapid capture of the tactile signal generated by the finger clicking the mouse during use.

[0072] The performance comparison of the flexible pressure sensor based on biomimetic microstructure provided in Example 1 with other reported sensors is shown in Table 1 below:

[0073]

[0074] In summary, the flexible pressure sensor based on biomimetic microstructure provided in Embodiment 1 of the present invention has high sensitivity, wide detection range, fast response, low detection limit and long-term working stability, and has great application potential in fields such as human motion monitoring and tactile perception.

[0075] Example 2: This example uses the fabrication method of the flexible pressure sensor based on biomimetic microstructures provided in Example 1. The difference from Example 1 is that the "MXene solution" in step 1 is replaced with other conductive materials, such as one or a combination of carbon nanotube dispersion, PEDOT:PSS, or graphene conductive paste. Other preparation methods are the same as in Example 1.

[0076] Example 3: This example uses the fabrication method of the flexible pressure sensor based on biomimetic microstructure provided in Example 1. The difference from Example 1 is that the "silver target" material in step 4 is replaced with other conductive metals, such as gold (Au), copper (Cu), aluminum (Al), platinum (Pt), or nickel (Ni). Other fabrication methods are the same as in Example 1.

[0077] Example 4: This example uses the fabrication method of the flexible pressure sensor based on biomimetic microstructures provided in Example 1. The difference from Example 1 is that step 4, "forming a conductive layer by magnetron sputtering of a silver target onto the surface of the biomimetic microstructure elastomer under an argon atmosphere," is replaced with "preparing the conductive layer using a spraying technique." The spraying material is one or a combination of two-dimensional materials (such as MXene, graphene) and one-dimensional nanomaterials (such as carbon nanotubes, silver nanowires, copper nanowires). Other preparation methods are the same as in Example 1.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flexible pressure sensor based on a biomimetic microstructure, characterized in that, The structure consists of a flexible electrode layer (1), an intermediate fixing layer (2), a microstructure sensing layer (3), and an encapsulation layer (4) attached sequentially from bottom to top. The flexible electrode layer (1) includes a thin film substrate and interdigitated electrodes. The interdigitated electrodes are prepared by printing conductive ink on the thin film substrate. The intermediate fixing layer (2) has a notch in the center for placing the microstructure sensing layer (3). The microstructure sensing layer (3) includes a biomimetic microstructure elastomer and a conductive layer on its outer surface. The encapsulation layer (4) is used to wrap the intermediate fixing layer (2) and the microstructure sensing layer (3). The biomimetic microstructure elastomer of the microstructure sensing layer (3) has multiple snake-scale microstructure units with different tilt angles.

2. The flexible pressure sensor based on biomimetic microstructure according to claim 1, characterized in that, Three types of snake-scale microstructure units with different tilt angles are provided on the biomimetic microstructure elastomer of the microstructure sensing layer (3). The tilt angles of the three types of snake-scale microstructure units are 45°, 35° and 25°, respectively, and the heights are 443.7µm, 361.3µm and 263.9µm, respectively. Multiple snake-scale microstructure units are distributed in a cross pattern, and the three types of snake-scale microstructure units are arranged in a gradient.

3. The flexible pressure sensor based on biomimetic microstructure according to claim 2, characterized in that, The material of the encapsulation layer (4) is polyimide tape with a thickness of 50-100µm.

4. A method for fabricating a flexible pressure sensor based on a biomimetic microstructure, characterized in that, The method for fabricating a flexible pressure sensor based on a biomimetic microstructure as described in any one of claims 1 to 3 comprises the following steps: Step 1: The thin film substrate is cleaned with deionized water and alcohol to remove surface impurities. After natural drying, it is subjected to oxygen plasma treatment to enhance its surface hydrophilicity. Then, conductive ink is printed on the thin film substrate according to the preset electrode pattern to obtain a flexible electrode layer with interdigitated electrode structure (1). Step 2: Cut a notch in the center of the pre-cut flexible film to place the microstructure sensing layer (3) to obtain the intermediate fixing layer (2). Step 3: Directly construct the reverse model of the biomimetic microstructure elastomer, and prepare the reverse template with grooves through 3D printing technology. Immerse the reverse template completely in isopropanol solution for no less than 24 hours. After drying, add silicone rubber to its surface. After vacuum degassing and curing, the biomimetic microstructure elastomer can be obtained by peeling it off once. Step 4: Clean the biomimetic microstructure elastomer with deionized water and alcohol in sequence to remove surface impurities, then treat the surface of the microstructure with oxygen plasma, and form a conductive layer by magnetron sputtering or spraying. Then place it in an oven at 50-70℃ and heat for 15-30 minutes to obtain a microstructure sensing layer with a biomimetic cross-tilted gradient structure (3). Step 5: Using the layer-by-layer bonding method, place the interdigitated electrode face of the flexible electrode layer (1) in Step 1 facing upwards, and then use square copper tape to bond the wires at both ends of the interdigitated electrode; then, attach the intermediate fixing layer (2) in Step 2 onto the flexible electrode layer (1), and then place the microstructure sensing layer (3) in Step 4 into the notch in the center of the intermediate fixing layer (2), so that the conductive layer of the microstructure sensing layer (3) is bonded to the middle area of ​​the interdigitated electrode; finally, encapsulate the intermediate fixing layer (2) and the microstructure sensing layer (3) to obtain a flexible pressure sensor based on biomimetic microstructure.

5. The method for fabricating a flexible pressure sensor based on a biomimetic microstructure according to claim 4, characterized in that, The thin film substrate in step 1 is polyethylene terephthalate, and the conductive ink is one or a combination of several of the following: MXene solution, carbon nanotube dispersion, PEDOT:PSS, or graphene conductive paste.

6. The method for fabricating a flexible pressure sensor based on a biomimetic microstructure according to claim 5, characterized in that, The intermediate fixing layer (2) in step 2 is a polyethylene terephthalate film with a thickness of 100-300 μm, and one side of the intermediate fixing layer (2) is adhesive for face-to-face bonding with the flexible electrode layer (1).

7. The method for fabricating a flexible pressure sensor based on a biomimetic microstructure according to claim 6, characterized in that, In step 4, the target material for the magnetron sputtering process is any one of silver, gold, copper, aluminum, platinum, or nickel; the material used in the spraying process in step 4 is any one or a combination of several of MXene, graphene, carbon nanotubes, silver nanowires, and copper nanowires.

8. The application of the pressure sensor prepared by the method of preparing a flexible pressure sensor based on a biomimetic microstructure as described in claim 7 in human health detection and tactile sensing.

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