CN111533081B - A composite flexible pressure sensor based on bionic microstructure and preparation method thereof - Google Patents

Abstract

The invention provides a composite flexible pressure sensor based on a bionic microstructure and a preparation method thereof. The pressure sensor is divided into a capacitive layer, a common matrix layer and a piezoresistive layer from top to bottom. Wherein, the capacitor layer includes a protective film layer, a first electrode layer, a dielectric layer and a second electrode layer from top to bottom; the piezoresistive layer includes a lateral electrode layer, a vertical electrode layer, a dielectric layer, a cross electrode layer and a second electrode layer from top to bottom. base film. The dielectric layer adopts a double-layer bi-level dome bionic microstructure, and the material is the same polymer with adjustable elastic modulus as the common matrix layer. The dielectric layer adopts a single-layer bi-level dome biomimetic microstructure, and the material is a nano-scale conductive composite material filled with multi-walled carbon nanotubes (MWCNT) and carbon black (CB) into a flexible polymer. The bottom staggered electrode layer adopts a multi-level "S" type interconnected wire structure. The invention has the characteristics of high sensitivity, good stability and strong anti-interference while ensuring a large detection range.

Description

A composite flexible pressure sensor based on bionic microstructure and preparation method thereof

technical field

The invention belongs to the field of flexible electronics and sensors, in particular to a composite flexible pressure sensor based on a bionic microstructure and a preparation method thereof.

Background technique

With the continuous development of flexible electronic devices, in order to meet the needs of the intelligent era, a variety of flexible pressure sensors have been developed around the world to detect pressures of different magnitudes. The flexible pressure sensor has a simple structure, is ultra-thin, and has a very small mass. It also has variable characteristics and good stability. Flexible pressure sensors have been widely used in technology and other fields.

At present, flexible pressure sensors have been the focus of researchers in terms of sensitivity, pressure detection range, anti-interference, repeatability, stretchability, and transparency. Literature survey shows that the existing flexible tactile sensors still have two main shortcomings: First, the detection range of flexible pressure sensors that focus on micro pressure detection is generally small, and the sensitivity is small under high pressure (large pressure within the detection range), This limits the development of flexible pressure sensors in more application fields; second, flexible pressure sensors generally cannot collect multi-source signals at the same time, mainly through the plane integration of multiple sensors (sensor array) to achieve multi-signal detection, combined with signal processing system analysis and identification The pressure application position significantly increases the workload of signal processing and reduces the integration level of the flexible pressure sensor. At the same time, the cost of manufacturing multiple sensors is further increased, which needs to be solved urgently.

Therefore, the present invention develops a composite flexible pressure sensor based on a bionic microstructure, which has good comprehensive characteristics such as higher sensitivity and stability in a larger pressure sensing range. Combining the acquired multi-source signals with the signal acquisition and processing system can realize the visualization of pressure information. The detection process does not need to apply the same pressure multiple times to the sensor, thereby improving reliability and reducing errors. Improve the performance of detecting multiple electrical signals at the same time, creating application advantages for miniaturized sensors.

SUMMARY OF THE INVENTION

Aiming at the defects of the above-mentioned flexible pressure sensor, the present invention proposes a composite flexible pressure sensor based on a bionic microstructure and a preparation method thereof. The flexible pressure sensor adopts a composite structure design as a whole, and adopts a bionic structure in the dielectric layer and the dielectric layer; the conductive film in the capacitor layer is used as an electrode, and a double-layer double-stage dome bionic is introduced between the first electrode layer and the second electrode layer. Microstructured elastic polymer PDMS, the side with the dome biomimetic microstructure of the upper layer and the side with the dome biomimetic microstructure of the lower layer are in contact with each other; in the piezoresistive layer, the transverse and longitudinal electrode layers, the dielectric layer and the staggered electrode layer constitute a differential layer distribution , wherein the nano-scale conductive composite material with a single-layer double-level dome structure is used as the dielectric layer, and the upper multi-level "S" type interconnected micro-scale wires, the separation layer and the lower multi-level "S" type interconnected micro-scale wires are used as interlaced electrode layers.

The pressure sensor of the present invention is divided into a capacitive layer, a common matrix layer and a piezoresistive layer from top to bottom. Wherein, the capacitor layer includes a protective film layer, a first electrode layer, a dielectric layer and a second electrode layer from top to bottom; the piezoresistive layer includes a lateral electrode layer, a vertical electrode layer, a dielectric layer, a cross electrode layer and a second electrode layer from top to bottom. base film. The dielectric layer adopts a double-layer bi-level dome bionic microstructure, and the material is the same polymer with adjustable elastic modulus as the common matrix layer. The dielectric layer adopts a single-layer bi-level dome biomimetic microstructure, and the material is a nano-scale conductive composite material filled with multi-walled carbon nanotubes (MWCNT) and carbon black (CB) into a flexible polymer. The bottom staggered electrode layer adopts a multi-level "S"-shaped interconnected wire structure, so that when the sensor is bent or twisted to a certain extent, the influence on the electrical signal is significantly reduced, and the ductility of the flexible pressure sensor is further improved. The material of the protective film layer and the base film is a protective flexible insulating material, and covers the top and bottom of the sensor, respectively. The composite flexible pressure sensor based on the bionic microstructure of the present invention has the characteristics of high sensitivity, good stability and strong anti-interference while ensuring a large detection range. In addition, the sensor can distinguish the position where pressure is applied by collecting multi-source signals, which provides a broader space for the practical application of flexible pressure sensors focusing on the visualization of pressure information.

The concrete technical scheme of the present invention is as follows:

A composite flexible pressure sensor based on bionic microstructure is divided into a capacitive layer, a common matrix layer and a piezoresistive layer from top to bottom. Among them, the capacitor layer includes a protective film layer 1, a first electrode layer 2, a dielectric layer 3 with a bionic structure, and a second electrode layer 4 from top to bottom; these four layers are stacked in parallel planes in sequence; To the bottom including the lateral and vertical electrode layers 6, the dielectric layer 7 with bionic structure, the upper multi-level "S" type interconnect micro-scale wires 8, the separation layer 9, the lower multi-level "S" type interconnect micro-scale wires 10 and the bottom is The base film 11 with protective effect; the staggered electrode layer is composed of the upper multi-level "S" type interconnected micron-scale wires 8, the separation layer 9 and the lower multi-level "S" type interconnected micron-scale wires 10; The electrode layers 6 are superimposed and attached to the lower surface of the common matrix layer 5 in the same shape, and then form a differential layer distribution with the staggered electrode layers.

Further, in the biomimetic microstructure of the double-layer double-stage dome, the biomimetic microstructure of the upper-layer double-stage dome is opposite to the biomimetic microstructure of the lower-layer double-stage dome, and the biomimetic microstructures 12 of the first-level dome are regularly distributed and relatively uniform in height, and the convex The average height is 20-40 μm, and the average width is 15-20 μm; the biomimetic microstructures 13 of the secondary domes are randomly distributed on the surface of the biomimetic microstructures 12 of each primary dome, and the ratio of height to width is similar to that of the biomimetic microstructures of the primary dome. It is 5 to 6 times smaller than the first-level dome bionic microstructure.

Further, in the single-layer two-stage dome biomimetic microstructure, the dome biomimetic microstructure is opposite to the staggered electrode layer, the first-level dome biomimetic microstructure 12 is distributed without gaps and has a similar height, and the average height of the protrusions is 10-20 μm. The average width is 10-15 μm; the biomimetic microstructures 13 of the secondary domes are randomly distributed on the surface of each primary dome biomimetic microstructure 12, and the ratio of height to width is similar to that of the biomimetic microstructures of the primary domes, and the volume ratio is higher than that of the biomimetic microstructures of the primary domes. 5 to 6 times smaller.

Further, the thickness of the protective film layer and the base film layer is 30-50 μm, and the thickness of the electrode film is 150-250 nm.

The invention provides a preparation method of a composite flexible pressure sensor based on a bionic microstructure, comprising:

The PDMS solution fully mixed with the prepolymer and the curing agent at a ratio of 10:1 was put into a vacuum desiccator, and the PDMS mixture was spin-coated on the surface of the reverse mold of the single-layer bi-level dome biomimetic microstructure. A conductive thin film is sputter deposited on the other side. Two sheets of the above-mentioned single-layer double-stage dome bionic microstructure film with electrode layers are made, and the dome structures are opposite to each other and any side of the dome structure is selected to be pasted on the flexible insulating protective film layer.

Next, spin-coat a 40-50 μm thick positive photoresist AZ6130 on the single crystal silicon substrate, and develop it on the photoresist film by photolithography. After hard baking and etching, a microstructure mold opposite to the common matrix layer is obtained. The PDMS solution in which the prepolymer and the curing agent were thoroughly mixed at a ratio of 8:1 was put into a vacuum dryer, and then the PDMS mixture was spin-coated on the surface of the reverse film, cured and peeled off.

Then, the concave-convex structure side of the common matrix layer obtained above is attached to a masking abrasive tool, and the masking abrasive tool is removed after sputtering deposition to obtain lateral and vertical electrode layers. The MWCNT/CB/PDMS nanocomposite solution was scraped on the surface of the anti-mold of the single-layer bi-level dome biomimetic microstructure, placed in a vacuum chamber after adding a curing agent to extract the internal gas, and cured at high temperature and attached to the surface. horizontal and vertical electrodes.

Then, put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 10:1 into the vacuum dryer, and then intrude the PDMS mixture into the reverse mold of the separator structure, so that the liquid level of the mixture solution is lower than the mold groove. Depth, after curing, stripping, and printing the upper layer of multi-level "S"-shaped interconnected silver micron-level wires on its surface. The lower layer of multi-level "S"-shaped interconnected silver micro-scale wires is printed on the base film, and is attached to the electrode-free side of the previously obtained structure.

Finally, the above obtained structures are laminated together in sequence, and an electrode cord is introduced to connect with the conductive film, and the composite flexible pressure sensor based on the biomimetic microstructure is obtained by encapsulation.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention adopts a composite structure design, and is a flexible pressure sensor prepared by microstructured polymer materials, conductive materials and protective insulating materials. The elastic modulus of the common matrix layer is two orders of magnitude higher than that of the upper dielectric layer and the lower dielectric layer, so that deformation is unlikely to occur under the condition of ensuring elasticity. By rationally utilizing the adjustable hardness of the polymer polydimethylsiloxane, the capacitive layer and the piezoresistive layer are assembled together without affecting the process of converting pressure into various electrical signals.

2. The double-stage dome structure in the present invention is a bionic microstructure, and the sensor is deformed under pressure to make the elastic polymer structure more compact, further reducing the distance between the electrode layers and increasing the contact area, so there is a relatively Large electrical signal output. The bi-level dome biomimetic microstructure increases the friction between the two layers, which can avoid sliding displacement. This can not only improve the detection ability of micro pressure, but also can assist the composite structure to further improve the pressure detection range. Solve the problems of small detection range and unsatisfactory sensitivity under high pressure of some thin-film sensors that focus on micro pressure detection.

3. The differential layer distribution structure in the present invention can convert the pressure signal into a plurality of electrical signals to analyze the magnitude and position information of the pressure. In addition, this special structure makes it almost difficult for sliding displacement to occur between the multiple layers of the sensor, which improves the stability of the flexible pressure sensor in practical applications.

4. The present invention improves the signal acquisition performance, and replaces the traditional way of realizing multi-signal detection through the planar integration (sensor array) of multiple sensors. On the one hand, the function of the array sensing element is integrated into the sensor, and miniaturization is achieved; on the other hand, the manufacturing process can be simplified and the cost can be reduced.

5. The composite flexible pressure sensor based on the bionic microstructure of the present invention has the characteristics of high sensitivity, good stability and strong anti-interference while ensuring a large detection range, and combined with the signal acquisition and processing system, the pressure can be realized. Information visualization. The improvement of performance and the realization of multifunctionality can further expand the application field of flexible pressure sensors.

Description of drawings

Fig. 1 is a schematic diagram of the split structure of the composite flexible pressure sensor based on the bionic microstructure of the present invention.

Figure 2. Cross-sectional view of the internal piezoresistive layer of the composite flexible pressure sensor based on the biomimetic microstructure along the XOZ plane.

Figure 3. Schematic diagram of the regular array distribution of primary microspheres in the dome biomimetic microstructure.

Figure 4. Schematic diagram of the bi-level dome biomimetic microstructure of the composite flexible pressure sensor based on the biomimetic microstructure.

Figure 5. Structural schematic diagram of the distribution of the first-order microsphere gapless array in the dome biomimetic microstructure.

Figure 6. Schematic diagram of multi-level "S" interconnect micron-scale wires.

Figure 7. Cross-sectional view of the present invention with localized stress acting on the flexible pressure sensor.

Figure 8. Top view of the bottom staggered electrode layer of the composite flexible pressure sensor based on the biomimetic microstructure.

Figure 9a. Schematic analysis of the sensor base with lateral electrodes.

Figure 9b. Schematic analysis of the sensor base with longitudinal electrodes.

In Fig. 9a and Fig. 9b: the thick solid line is a multi-level "S"-shaped interconnected micron-level wire, the thinned part of one end can be regarded as the calculated resistance of the appropriate value R ₀ , 1-4 represent the resistance value caused by local compression deformation changing area

In the figure: 1. Protective film layer, 2. First electrode layer, 3. Dielectric layer, 4. Second electrode layer, 5. Common matrix layer, 6. Horizontal and vertical electrode layers, 7. Dielectric layer, 8. Upper-layer multi-level "S"-shaped interconnected micron-scale wires, 9. Separation layer, 10. Lower-layer multi-level "S"-shaped interconnected micron-scale wires, 11. Base film, 12. First-level dome bionic microstructure, 13. Second-level dome Bionic Microstructure

Detailed ways

The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, so that the purpose, technical solutions, features, etc. of the invention are more clearly understood and easy to understand. Limitations of Invention.

Referring to 1, it is a schematic diagram of the split structure of the composite flexible pressure sensor based on the bionic microstructure of the present invention. From top to bottom, it includes protective film layer 1, first electrode layer 2, dielectric layer 3, second electrode layer 4, common matrix layer 5, lateral and vertical electrode layers 6, dielectric layer 7, upper multi-level "S" type interconnected micron-scale wires 8 , separation layers 9 , lower multi-level “S” type interconnected micron-scale wires 10 and base film 11 . The staggered electrode layer is composed of the upper multi-level "S" type interconnected micro-scale wires 8 , the separation layer 9 and the lower multi-level "S" type interconnected micro-scale wires 10 . The dielectric layer 3 has a double-layer bi-level dome biomimetic microstructure, and one side of each layer with the bi-level dome biomimetic microstructure is in contact with each other. The dielectric layer 7 has a single-layer bi-level dome biomimetic microstructure, and the side with the bi-level dome biomimetic microstructure faces the staggered electrode layer. The cross-sectional structure of this part is shown in FIG. 2 .

The double-layer double-stage dome biomimetic microstructure of the capacitor layer, the first-level dome biomimetic microstructure 12 is regularly distributed and the height is relatively uniform, as shown in FIG. . The biomimetic microstructures 13 of the secondary dome are randomly distributed on the surface of each primary dome biomimetic microstructure, as shown in FIG. 4 . The average height of the protrusions is 3-6 μm, and the average width is 2-3 μm. The single-layer double-stage dome biomimetic microstructure of the piezoresistive layer, the first-stage dome biomimetic microstructure is distributed without gaps and has a similar height, as shown in Figure 5, the average height is 10-20 μm, and the average width is 10-15 μm. Similarly, the biomimetic microstructures of the secondary domes are randomly distributed on the surface of each primary dome biomimetic microstructure, and the average height of the protrusions is 2-3 μm, and the average width is 1-2 μm. The thickness of the protective film layer and the base film is 30-50 μm, the thickness of the conductive film deposited by sputtering is 150-250 nm, and the thickness of the common base layer in the middle is 40-80 μm. Referring to FIG. 6 , the overall line width of the multi-level "S" type interconnected micron-level wires is 50-100 μm, and the height is 500-700 nm.

The working principle of the present invention is as follows:

The bi-level dome biomimetic microstructure of the present invention is inspired by the facial skin structure and integumentary sensory organs of the vertebrate with excellent mechanosensing ability, the South American caiman.

Vertebrates have abundant sensory organs, and the combination of different surface structures can show a very strong comprehensive sensitivity to a variety of stimuli. As far as pressure stimulation is concerned, it can have high sensitivity to pressure within a specific range, and instantly identify and respond to the part of the body that is stimulated by pressure. This relies on multiple sensory receptors in vertebrates, which are discretely distributed in multiple locations such as the face, mouth, and skin. The South American caiman is particularly sensitive to pressure stimuli, and can precisely locate its prey through tiny pressure waves on the water surface.

Studies have shown that the skin of the South American caiman includes many tiny sensory organs discretely distributed on the head and face, similar in size, in the shape of micro-dome or micro-dome, and in large numbers and widely distributed. Areas containing these tiny sensory organs have a thinner outer stratum corneum, which increases sensitivity to stress without losing its protective function. In particular, multiple small domes of different grades are randomly distributed on the face/jaw of the caiman in South America, and multiple tiny sensory organs are also randomly distributed on each dome. When the head of the caiman is half-floating on the water surface, such a large-small bi-level structure increases the contact area of caiman with the water, further increasing the sensitivity to tiny pressure waves on the water surface. Multiple tiny sensory organs form a high-resolution pressure-sensing array that can pinpoint the location of prey.

Based on the features of the facial skin structure and outer skin sensory organs of the South American caiman, the present invention designs the upper dielectric layer and the lower dielectric layer as a double-level micro-dome structure. In detail, when the sensor of the present invention is subjected to external stress, the sensor undergoes deformation as shown in Fig. 7, PDMS can change its elasticity degree by adjusting the ratio of curing agent and original solution and curing time, that is, curing agent The more it is added, the harder it becomes after curing, and its ratio and hardness conform to a logarithmic curve, so the dielectric and dielectric layers deform preferentially. For the sensor, the external pressure can be simply divided into low pressure and high pressure. When the sensor is subjected to very low pressure, the secondary structure in the double-layer double-stage dome biomimetic microstructure will deform and contact after the primary structure contacts, which can make the face-to-face The elastic polymer structure is more compact, and the distance between the first electrode layer and the second electrode layer is further reduced, so that there is a larger electrical signal output. This takes full advantage of the high sensitivity, low hysteresis and high stability of the capacitive layer. When the sensor is subjected to high pressure, when the pressure and electrical signal change curve of the capacitive layer is almost close to horizontal saturation, the piezoresistive layer can help overcome this defect and share a part of the pressure to produce corresponding deformation. In the single-layer bi-level dome biomimetic microstructure, the secondary structure is in contact with the staggered electrodes and the primary structure is deformed and contacted, which not only improves the sensitivity of the piezoresistive layer, but also further increases the contact area between each microstructure and the staggered electrodes. , so that the nanocomposite will form more complex conductive paths, so there is a larger electrical signal output. The electrical signals of the two layers are collected separately, and the pressure information can be obtained after analysis and processing. In fact, the piezoresistive layer can not only provide multiple signals for the visualization of pressure information, but also play an auxiliary role in expanding the detection range of the sensor while maintaining a high sensitivity.

In the above case, for the capacitive layer containing the double-layer bi-level dome biomimetic microstructure, the relative elastic PDMS microstructure is more compact when the external stress is applied, which is equivalent to an indirect increase in the dielectric constant ε _r , and The distance d between the first electrode layer and the second electrode layer also becomes smaller. Therefore, the capacitance of the circuit is changed as described in the following calculation formula. For the special case of tiny pressure, the secondary dome biomimetic microstructure will preferentially contact deformation resulting in capacitance change.

The capacitance C is closely dependent on the dielectric constant ε _r of the interlayer material, the effective electrode area A and the distance d between the two plate electrodes, where ε ₀ is the vacuum dielectric constant.

In the above case, for a piezoresistive layer containing a single-layer bi-level dome biomimetic microstructure, the dielectric layer is deformed by force, the contact area between each microstructure and the staggered electrode layer increases, and the nanocomposite will form a certain complex conductive paths. The compressive deformation actually causes an increase in the contact area and a decrease in the thickness of the nanocomposite, and indirectly increases the total resistivity, thus changing the resistance of the circuit as described in the following calculation formula.

The resistance is closely dependent on the cross-sectional area B between the nanocomposite layer and the electrode and the total thickness m of the nanocomposite layer, ρ is the resistivity.

It should be noted that when the sensor is subjected to external pressure, the pressure information can be converted into multiple electrical signal changes. The signal collected by the first electrode and the second electrode in the capacitive layer is changed to electrical signal 1, the signal collected by the lateral electrode and the staggered electrode layer A1 in the piezoresistive layer is changed to an electrical signal 2, and the lateral electrode and the staggered electrode layer A2. The collected signal changes to electrical signal 3 , the signal collected from the A1 and A2 ends of the interleaved electrode layer changes to electrical signal 4 , and the signal collected from the longitudinal electrode and the B1 end of the interleaved electrode layer changes to electrical signal 5 . The signals collected by the longitudinal electrodes and the B2 end of the staggered electrode layer are changed into electrical signals 6, and the signals collected at the ends B1 and B2 of the staggered electrode layers are changed into electrical signals 7, as shown in FIG. 8 and FIG. 9 .

The following is a detailed analysis of the principle of the pressure information visualization function:

The comprehensive performance index is an important factor in determining the application field of the flexible pressure sensor, and the pressure information visualization function is a supplement to the good performance index, which can further expand the application field of the sensor. The improvement of signal acquisition performance is the basis for realizing the visualization function of pressure information, so the present invention not only improves the comprehensive performance, but also can collect multi-source signals, and combine the two sets of electrical signals obtained by the differential layer distribution structure with the signal acquisition and processing system , so as to realize the visualization function of pressure information.

The bottom piezoresistive layer structure design of the present invention actually divides the sensor plane into 9 areas. When the local pressure is deformed, as shown in FIG. 7, the upper layer electrical signal 2, electrical signal 3 and electrical signal 4 determine the pressure The position information in the X-axis coordinate direction, the lower layer electrical signal 5 , the electrical signal 6 and the electrical signal 7 determine the position information in the Y-axis coordinate direction of the pressure. The size of the pressure needs to be comprehensively analyzed and determined in combination with all electrical signal changes of the sensor. The following takes the X-axis coordinate as an example to explain how to determine the position information in detail, referring to Fig. 9a and Fig. 9b (the solid line is the lower electrode, which is connected with a calculated resistance of appropriate value R ₀ , in fact, the calculated resistance R ₀ is calculated by subtracting The local resistance value increases due to the small cross-sectional area of the wire, not the series resistance between the wires) in the initial state, the corresponding electrical signal, that is, the resistance is approximately equal to the sum of the resistance value of the appropriate resistance and the resistance of the microstructure. When the sensor is subjected to external pressure at the elliptical position, the resistance between the upper and lower electrodes at the elliptical position changes, the greater the pressure, the smaller the on-resistance, and the resulting resistance value varies in the range of R0 and close to _zero between ohms (R ₀ ≤ actual resistance value < 0). The pressure reaches a certain value such that the resistance is small enough that the measurement of the resistance between A1 and A2 will cause the calculated resistance at the corresponding location to be short-circuited. From the point of view of the two-dimensional coordinate information for determining the pressure, the larger the local pressure on the externally applied sensor, the closer the determined result is to the ideal value.

Example

The preparation method of the composite flexible pressure sensor based on the bionic microstructure of the present invention specifically includes:

Step 1: Put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 10:1 into a vacuum desiccator, which can remove the air bubbles generated in the PDMS mixture during the stirring process. Then spin-coat the PDMS mixture on the counter-mold surface of the single-layer double-stage dome biomimetic microstructure with a forward rotation speed of 1000 r/min for 45 s and a rear rotation speed of 5000 r/min for 50 s;

Step 2: The PDMS solution is cured at 100° C. for 50 minutes, and a PDMS film is obtained after peeling off. Refer to one side of the dielectric layer 3 shown in FIG. 1 , the thickness of which is about 60 μm;

Step 2: The PDMS solution is cured at 100°C for 50 minutes, and a PDMS film is obtained after peeling off. Step 3: A copper electrode film is plated on the smooth side of the PDMS film by RF sputtering. The RF current in this process is 100 mA, and the sputtering time For 5 minutes, the target material is a copper target material, and the thickness of the obtained electrode film is about 200nm;

Step 4: The surface of the single crystal silicon substrate is cleaned and dried, and then a positive photoresist (AZ6130) with a thickness of 40-50 μm is spin-coated on the surface. Continue to rotate for 40s, and the speed is 2000r/min. The microstructure mold with the opposite common matrix layer 5 is obtained after soft baking, alignment exposure, post-baking, developing, hard baking, and etching in sequence. Put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 8:1 into a vacuum desiccator, and then spin-coat the PDMS mixture on the surface of the reverse mold at a forward rotation speed of 1000 r/min for 45 s and a rear rotation speed is 5000r/min for 50s; the same conditions as in step 2 are cured and peeled off to obtain the common matrix layer 5;

Step 5: The concave-convex structure side of the common matrix layer obtained in Step 4 is attached to the masking abrasive tool, and a copper-plated film with a thickness of about 200 nm is deposited on the surface thereof by sputtering. Then remove the masking tool to obtain transverse and longitudinal electrode layers 6;

Step 6: Repeat Step 1, Step 2 and Step 3, place the two prepared films with the bi-level dome biomimetic microstructure on the opposite side, and laminate them between the flexible polyimide (PI) film and the common substrate layer , the capacitive layer of the composite flexible pressure sensor based on the bionic microstructure is completed;

Step 7: The 8% MWCNT and 3% CB particle content PDMS nanocomposite solution was blade-coated on the reverse mold surface of the single-layer bi-level dome biomimetic microstructure, cured at 100 °C for 30 minutes and peeled off from the mold, the nanocomposite After the film is fully cured, it is attached to the transverse and longitudinal electrodes;

Step 8: Put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 10:1 into a vacuum dryer, and then make the PDMS mixture penetrate into the reverse mold of the separator structure, so that the liquid level of the mixture solution is lower than the mold cavity. The depth of the groove, the thickness is about 30μm, and cured and peeled off under the same conditions as in step 2

Step 9: Using inkjet printing technology on the surface of the structure obtained in Step 8, the nano-silver ink is directly printed to prepare the upper-layer multi-level "S"-shaped interconnected silver micro-scale wires 8, as shown in Figure 1 and Figure 5;

Step 10: Refer to Figures 1 and 5 on the upper surface of the flexible polyimide (PI) base film to print and prepare the lower-layer multi-level "S"-shaped interconnected silver micro-scale wires 10, and the structure obtained in Step 6 has no electrodes one side fit;

Step 11: Introduce an electrode cord connected to the conductive film, and finally package the above obtained structures in order from top to bottom to obtain the composite flexible pressure sensor based on the biomimetic microstructure.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. within.

Claims (9)

1. a composite flexible pressure sensor based on bionic microstructure, is characterized in that, is divided into capacitance layer, common matrix layer and piezoresistive layer from top to bottom, wherein, capacitance layer from top to bottom comprises: protective film layer ( 1), a first electrode layer (2), a dielectric layer (3) with a biomimetic structure, and a second electrode layer (4); these four layers are stacked in parallel planes in sequence; the piezoresistive layer from top to bottom includes: lateral and a vertical electrode layer (6), a dielectric layer with a bionic structure (7), an upper layer of multi-level "S" type interconnected micron-scale wires (8), a separation layer (9), a lower layer of multi-level "S" type interconnected micron-scale wires (10) and a protective base film (11) at the bottom; the staggered electrode layer consists of the upper multi-level "S" type interconnected micron-scale wires (8), the separation layer (9) and the lower multi-level "S" type interconnected micron-scale wires Wires (10) are composed; the dielectric layer (7) and the transverse and longitudinal electrode layers (6) are superimposed in the same shape and attached to the lower surface of the common matrix layer (5); the transverse and longitudinal electrode layers (6), the dielectric The layer (7) and the staggered electrode layers constitute a differential layer distribution; The differential layer distribution, the cross-sectional view is that the two-layer microstructures alternate at different heights, and the electrical signals collected by the piezoresistive layer can be divided into two groups; the upper layer electrical signal is used to determine the position information of the applied pressure in the X-axis direction, and the lower layer The electrical signal is used to determine the position information of the applied pressure in the Y-axis direction. 2. A composite flexible pressure sensor based on a biomimetic microstructure according to claim 1, characterized in that the dielectric layer (3) adopts a double-layer double-stage dome biomimetic microstructure, and the upper-layer double-stage dome biomimetic microstructure Compared with the biomimetic microstructure of the lower two-level dome, the biomimetic microstructure (12) of the first-level dome is regularly distributed and has a relatively uniform height, the average height of the protrusions is 20-40 μm, and the average width is 15-20 μm; the biomimetic microstructure of the second-level dome is (13) randomly distributed on the surface of each primary dome biomimetic microstructure (12), the height-width ratio is similar to that of the primary dome bionic microstructure, and the volume is 5-6 times smaller than the primary dome bionic microstructure. 3. A composite flexible pressure sensor based on a biomimetic microstructure according to claim 1 or 2, wherein the dielectric layer (7) adopts a single-layer two-stage dome biomimetic microstructure, and the dome biomimetic microstructure is staggered and The electrode layers are opposite to each other, the first-level dome biomimetic microstructures (12) are distributed without gaps and have similar heights, the average height of the protrusions is 10-20 μm, and the average width is 10-15 μm; the second-level dome biomimetic microstructures (13) are irregularly distributed On the surface of each first-level dome biomimetic microstructure (12), the ratio of height to width is similar to that of the first-level dome biomimetic microstructure, and the volume is 5-6 times smaller than that of the first-level dome biomimetic microstructure. 4. A composite flexible pressure sensor based on a bionic microstructure according to claim 3, characterized in that the thickness of the protective film layer (1) and the base film (11) is 30-50 μm; the dielectric layer (3) ) and the material of the common matrix layer (5) are selected from polydimethylsiloxane PDMS. 5. A composite flexible pressure sensor based on bionic microstructure according to claim 1, characterized in that, the interleaved electrode layer adopts a multi-level "S" type interconnected wire structure, and the top of the first-level "S" type wire is A small section of the cross-sectional area is smaller than other sections, and the rest of the wires are normal "S"-shaped distribution. 6. A composite flexible pressure sensor based on a bionic microstructure according to claim 2, wherein the piezoresistive layer divides the sensor into 9 regions, and the position information of the local pressure is clarified in combination with the signal processing system; The contact between the two-layer bi-level dome biomimetic microstructures is dome-to-dome or dome-to-groove. 7. A preparation method of a composite flexible pressure sensor based on a bionic microstructure, characterized in that, comprising the following steps: Step 1: Put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 10:1 into a vacuum desiccator, and then spin-coat the PDMS mixture on the surface of the reverse mold of the single-layer double-stage dome biomimetic microstructure and cure. , after peeling off and sputtering deposited conductive film on the other side; Step 2: making two single-layer double-stage dome biomimetic microstructures with electrode layers in step 1, and the two-stage dome biomimetic microstructures are opposite to each other and select any side to be attached to the flexible insulating protective film layer; Step 3: Spin-coat a positive photoresist AZ6130 with a thickness of 40-50 μm on the monocrystalline silicon substrate, and develop on the photoresist film by photolithography technology. After hard baking and etching, a common matrix layer (5) is obtained. Conversely For the microstructure mold, the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 8:1 was put into a vacuum dryer, and then the PDMS mixture was spin-coated on the surface of the reverse mold, cured and peeled off; Step 4: The concave-convex structure side of the common matrix layer (5) obtained in step 3 is attached to the masking mold, and the masking mold is removed after sputtering deposition to obtain horizontal and vertical electrode layers (6); Step 5: The nanocomposite material solution is scraped on the surface of the anti-mold of the single-layer two-stage dome biomimetic microstructure, and then placed in a vacuum chamber after adding a curing agent to extract the internal gas, and after curing at high temperature, it is attached to the lateral and horizontal directions. on longitudinal electrodes; Step 6: Put the PDMS solution fully mixed with the prepolymer and the curing agent in a ratio of 10:1 into the vacuum dryer, and then intrude the PDMS mixture into the reverse mold of the separator structure, so that the liquid level of the mixture solution is lower than the mold cavity. The depth of the groove, after curing, stripping, and printing the upper layer of multi-level "S"-shaped interconnected silver micron-level wires on its surface (8); Step 7: print the lower multi-level "S"-shaped interconnected silver micro-scale wires (10) on the base film, and attach it to the electrodeless side of the structure obtained in step 6; Step 8: Finally, the structures obtained in Step 2, Step 5 and Step 7 are laminated together in order up and down, and electrodes are introduced to connect with the conductive film, and packaged to obtain the composite flexible pressure sensor based on the bionic microstructure. 8 . The method according to claim 7 , wherein the thickness of the conductive thin film deposited by sputtering in step 1 is 150-250 nm. 9 . 9. method according to claim 7, is characterized in that, in step 3, spin coating photoresist AZ6130 spin coating process condition is: continue 15s forward rotation, rotating speed is 1500r/min, continue 40s backward rotating, rotating speed is 2000r/min; the spin coating process conditions of liquid PDMS are: forward rotation for 45s, rotation speed is 1000r/min, rear rotation for 50s, rotation speed is 5000r/min; PDMS solution curing conditions are cured at 100 ℃ for 50 minutes .

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