A swell-bonded securement dual-channel flexible pressure sensor and method

Abstract

The application provides a swelling-bonding fixed-type dual-channel flexible pressure sensor and a method, and relates to the technical field of flexible pressure sensors. The sensor comprises, in sequence, an upper flexible substrate, an upper electrode layer, a first sensitive layer, an intermediate common electrode layer, a second sensitive layer, a lower electrode layer and a lower flexible substrate; the electrode layer is nano-silver / PDMS, and the sensitive layer is graphene / PDMS; the first sensitive layer is provided with a dome microstructure, and the second sensitive layer is provided with an inclined microcolumn structure, which respectively form a first and a second capacitance detection channel with the common electrode layer; adjacent electrode layers and sensitive layers are fixed through a swelling-bonding interface, which is formed by interpenetration and solidification of surface PDMS chains. The method comprises the following steps: preparing slurry, forming the electrode layer and the sensitive layer, interface swelling treatment, alignment and lamination, heating and solidification and electrode leading-out. The application can inhibit interlayer slip and contact hysteresis, take into account low-pressure sensitivity and high-pressure bearing, realize dual-channel partition detection, and is process-compatible and easy to mass-produce.

Description

Technical Field

[0001] This invention relates to the field of flexible pressure sensor technology, and more specifically to a swelling bonded solid-bonded dual-channel flexible pressure sensor and method. Background Technology

[0002] Flexible pressure sensors can convert external pressure, tactile contact, vibration, or acoustic disturbances into detectable electrical signals, making them valuable for applications in wearable devices, electronic skin, soft robots, human-computer interaction, and underwater disturbance monitoring. Capacitive flexible pressure sensors typically consist of a flexible electrode layer, a dielectric sensitive layer, and an encapsulation layer. Their output stability depends not only on the microstructure morphology of the sensitive layer and the conductive network of the electrodes but also significantly on the interface state between the electrode layer and the sensitive layer.

[0003] In existing technologies, to improve the compressibility and low-pressure response sensitivity of flexible pressure sensors, microstructure designs such as micropyramids, microcolumns, microdome, or porous structures are commonly employed. However, a single microstructure often struggles to simultaneously achieve both sensitive response in the low-pressure region and wide range capacity in the high-pressure region. For example, easily deformable microstructures are suitable for detecting minute pressures, but are prone to compression saturation under higher pressures; microstructures with high stiffness or strong support can help extend the measurement range, but their initial response is insufficient under minute pressures.

[0004] Furthermore, in traditional stacked flexible pressure sensors, the microstructure sensitive layer and electrode layer often rely on physical bonding, van der Waals interactions, or ordinary adhesion. Under dynamic pressure or high-frequency vibration, local slippage, micro-contact separation, interfacial frictional energy dissipation, and adhesion hysteresis can easily occur at the interlayer interface, leading to delayed response, inconsistent recovery, and decreased cyclic stability in the sensor output. While using an additional adhesive layer can enhance interlayer bonding, the adhesive layer introduces additional thickness, viscoelastic energy dissipation, and dielectric discontinuities, reducing pressure response sensitivity and dynamic response consistency.

[0005] Meanwhile, a single capacitance detection channel has limited signal resolution capability over a wide pressure range, making it difficult to distinguish between low-pressure and high-pressure ranges. Simply increasing the number of layers or detection channels introduces more interlayer interfaces and process steps, increasing structural complexity and interface instability.

[0006] Therefore, existing flexible pressure sensors still have shortcomings in terms of interface stability under dynamic loading conditions, balancing low-pressure sensitivity and high-pressure load-bearing capacity, and signal resolvability across multiple pressure ranges. Summary of the Invention

[0007] The purpose of this invention is to provide a swollen bonded solid-bonded dual-channel flexible pressure sensor and method to reduce interlayer slippage and contact hysteresis, improve dynamic response stability, and balance low-pressure response and high-pressure load bearing, while maintaining process feasibility.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A swellable bonded dual-channel flexible pressure sensor includes an upper flexible substrate, an upper electrode layer, a first sensitive layer, an intermediate common electrode layer, a second sensitive layer, a lower electrode layer, and a lower flexible substrate arranged in a top-to-bottom sequence. The upper electrode layer, the middle common electrode layer and the lower electrode layer all contain nano-silver / PDMS composite material, and the first sensitive layer and the second sensitive layer both contain graphene / PDMS composite material; The upper surface of the first sensitive layer is provided with a dome microstructure, and the upper surface of the second sensitive layer is provided with an inclined microcolumn structure. The upper electrode layer, the first sensitive layer, and the middle common electrode layer constitute the first capacitance detection channel, and the middle common electrode layer, the second sensitive layer, and the lower electrode layer constitute the second capacitance detection channel. A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer; The swelling bonding interface is formed by the interpenetration and solidification of polymer chains between the PDMS matrix surface layer in the adjacent layers of the nano-silver / PDMS composite material and the PDMS matrix surface layer in the graphene / PDMS composite material in the swollen state.

[0009] Furthermore, the swelling bonding interface is a continuous or discontinuously distributed interface bonding region, which covers at least the dome microstructure region of the first sensitive layer, the inclined micropillar structure region of the second sensitive layer, and the effective pressure-sensing region of the electrode layer.

[0010] Furthermore, the swelling bonding interface is located between the end of the dome microstructure and the upper electrode layer, between the lower surface of the first sensitive layer and the intermediate common electrode layer, between the end of the inclined micropillar structure and the intermediate common electrode layer, and between the lower surface of the second sensitive layer and the lower electrode layer.

[0011] Furthermore, the upper surface of the first sensitive layer protrudes upward to form several hemispheres, and the array structure composed of several hemispheres forms the dome microstructure, and the dome microstructure is integrally formed with the first sensitive layer.

[0012] Furthermore, the upper surface of the second sensitive layer protrudes upward to form several cylindrical or frustum-shaped pillars. The central axis of the pillars is arranged obliquely relative to the thickness direction of the second sensitive layer. The array structure composed of several pillars forms the oblique micropillar structure, and the oblique micropillar structure is integrally formed with the second sensitive layer.

[0013] Furthermore, the initial equivalent compressive stiffness of the first sensitive layer is less than the initial equivalent compressive stiffness of the second sensitive layer.

[0014] Furthermore, the initial deformation threshold of the dome microstructure is lower than the initial deformation threshold of the inclined microcolumn structure.

[0015] Furthermore, under the first applied pressure, the first sensitive layer preferentially compresses and deforms the second sensitive layer, increasing the capacitance change of the first capacitance detection channel; under the second applied pressure, the second sensitive layer participates in supporting and compressing deformation, increasing the capacitance change of the second capacitance detection channel; wherein, the first applied pressure is less than the second applied pressure.

[0016] Furthermore, the nano-silver / PDMS composite material includes nano-silver and PDMS prepolymer, wherein the nano-silver is one or more of silver nanowires, silver nanoparticles, and silver nanosheets, and the mass ratio of the nano-silver to the PDMS prepolymer is 8 wt.%-18 wt.%; the graphene / PDMS composite material includes graphene and PDMS prepolymer, wherein the mass ratio of the graphene to the PDMS prepolymer is 0.5 wt.%-5 wt.%; the PDMS prepolymer includes PDMS base adhesive and curing agent, wherein the mass ratio of the PDMS base adhesive to the curing agent is 3:1-10:1.

[0017] A method for fabricating a swellable bonded-bonded dual-channel flexible pressure sensor, the method comprising the following steps: S1. Preparation of PDMS prepolymer; PDMS-based adhesive and curing agent are mixed and degassed to obtain PDMS prepolymer; S2. Preparation of nano-silver / PDMS conductive paste and graphene / PDMS dielectric paste; Nano-silver was dispersed in chloroform, PDMS prepolymer was added, and the solvent was evaporated by stirring to obtain nano-silver / PDMS conductive paste;

[0018] Graphene was dispersed in chloroform, PDMS prepolymer was added, and the solvent was evaporated by stirring to obtain graphene / PDMS dielectric paste; S3. Prepare the electrode layer and the sensitive layer; Nano-silver / PDMS conductive paste is screen-printed to form an upper electrode layer and a lower electrode layer. Nano-silver / PDMS conductive paste is then spin-coated, scraped, or transferred to form an intermediate common electrode layer. The graphene / PDMS dielectric paste is replicated and molded using a dome microstructure mold to obtain the first sensitive layer, and the graphene / PDMS dielectric paste is replicated and molded using an inclined micropillar structure mold to obtain the second sensitive layer. S4. A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer; The electrode layer and the sensitive layer to be bonded are treated with an interface treatment solution containing chloroform, which causes the surface PDMS chain segments of the surface to be bonded to undergo micro-swelling. Align and bond the upper flexible substrate, upper electrode layer, first sensitive layer, middle common electrode layer, second sensitive layer, lower electrode layer and lower flexible substrate in that order; Light pressure and heat curing cause the PDMS chain segments of adjacent surface layers to interpenetrate, entangle, and solidify, forming a swollen bonding interface; S5, the electrode is led out, and a swollen bonded solid-bonded dual-channel flexible pressure sensor is obtained.

[0019] Compared with the prior art, the swelling bonded and solidified dual-channel flexible pressure sensor and method of the present invention have achieved the following significant technical effects: 1. This invention forms a swollen bonding interface between adjacent electrode layers and the sensitive layer. This interface is formed by the interpenetration and solidification of polymer chains between the PDMS matrix surface layer in the nano-silver / PDMS composite material and the PDMS matrix surface layer in the graphene / PDMS composite material in a swollen state, rather than by setting an independent adhesive layer. Therefore, under dynamic pressure or high-frequency vibration, it can effectively suppress interlayer local slippage, micro-contact separation, interfacial frictional energy dissipation, and adhesion hysteresis, reduce response hysteresis, and improve recovery consistency and cycle stability.

[0020] Since adjacent electrode layers and the sensitive layer are directly bonded together through a swelling bonding interface, the additional thickness, viscoelastic energy loss, and dielectric discontinuity introduced by the additional adhesive layer are avoided. This helps to maintain the pressure response sensitivity and dynamic response consistency of the sensor and improve the reliability of interlayer connections.

[0021] 2. This invention achieves differentiated mechanical responses through the dome-shaped microstructure of the first sensitive layer and the inclined microcolumn structure of the second sensitive layer. The initial equivalent compressive stiffness of the first sensitive layer is relatively small, and the initial deformation threshold of the dome-shaped microstructure is relatively low, allowing it to preferentially undergo elastic compressive deformation under low pressure, thus improving the response capability in the low-pressure region. The second sensitive layer participates in support and compressive deformation under higher pressure, which is beneficial for expanding the high-pressure bearing range and improving the signal differentiation capability in the high-pressure region, thereby balancing low-pressure sensitive response and high-pressure wide-range bearing capacity.

[0022] The upper electrode layer, the first sensitive layer, and the intermediate common electrode layer constitute the first capacitance detection channel, while the intermediate common electrode layer, the second sensitive layer, and the lower electrode layer constitute the second capacitance detection channel. Under a low applied pressure F1, the capacitance change in the first capacitance detection channel increases, while the change in the second capacitance detection channel is relatively small. Under a high applied pressure F2, the response of the second capacitance detection channel is enhanced. Therefore, different pressure ranges can be distinguished and detected through dual-channel signals, improving the signal resolution capability of a single capacitance detection channel over a wide pressure range.

[0023] The intermediate common electrode layer serves as the common electrode for both the first and second capacitance detection channels. This eliminates the need to simply increase the number of layers or detection channels to achieve multi-zone detection, reducing the number of interlayer interfaces and process steps, lowering structural complexity and interface instability factors, while maintaining the advantages of the sensor's thinness and flexible integration.

[0024] The upper electrode layer, intermediate common electrode layer, and lower electrode layer are made of nano-silver / PDMS composite material, which helps maintain conductivity continuity under bending and compression conditions. The first and second sensitive layers are made of graphene / PDMS composite material, which helps improve dielectric response and detectability of capacitance changes. The dome microstructure and tilted micropillar structure are integrally formed with their respective sensitive layers, avoiding secondary bonding interfaces between the microstructure and the sensitive layer substrate, thus improving structural integrity and response consistency.

[0025] The swelling bonding interface is a continuous or discontinuously distributed interfacial bonding region, which can cover part of the dome microstructure of the first sensitive layer, part of the inclined micropillar structure of the second sensitive layer, and the effective pressure-sensing region of the electrode layer, thereby achieving stable bonding within the effective pressure-sensing region without significantly limiting the compressive deformation capability of the microstructure.

[0026] 3. This invention can prepare the electrode layer and sensitive layer using processes such as screen printing, spin coating, blade coating, transfer printing, and mold replication. The surface PDMS segments are induced to undergo micro-swelling via an interface treatment solution containing chloroform, followed by alignment, bonding, light pressing, and heat curing to form a swollen bonding interface. This process is compatible with commonly used material systems and manufacturing processes for flexible sensors, has high feasibility, and is suitable for mass production. Attached Figure Description

[0027] Figure 1 This is an exploded view of the swollen-bonded and bonded dual-channel flexible pressure sensor according to an embodiment of the present invention; Figure 2 This is a perspective view of a swelling bonded and solidified dual-channel flexible pressure sensor according to an embodiment of the present invention; Figure 3 This is a top view of a swelling bonded and solidified dual-channel flexible pressure sensor according to an embodiment of the present invention; Figure 4 This is a structural schematic diagram of the assembly cross-section of the swelling bonded and solidified dual-channel flexible pressure sensor according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the first sensitive layer in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the second sensitive layer in an embodiment of the present invention; Figure 7 This is a partial structural diagram of the upper electrode layer, the first sensitive layer, and the swelling bonding interface in an embodiment of the present invention; Figure 8 for Figure 7 A magnified view of a section at point A in the middle; Figure 9 This is a schematic diagram of the response of a swelling bonded and fixed dual-channel flexible pressure sensor under a first external pressure according to an embodiment of the present invention. Figure 10 This is a schematic diagram illustrating the response of a swelling-bonded, fixed-connection dual-channel flexible pressure sensor under a second applied pressure, according to an embodiment of the present invention. Figure 11 This is a process flow diagram of the fabrication method of the swelling bonded and solidified dual-channel flexible pressure sensor according to an embodiment of the present invention; in, 1. Upper flexible substrate; 2. Upper electrode layer; 3. First sensitive layer; 31. Dome microstructure; 4. Intermediate common electrode layer; 5. Second sensitive layer; 51. Inclined micropillar structure; 6. Lower electrode layer; 7. Lower flexible substrate; 81. First capacitance detection channel; 82. Second capacitance detection channel; 9. Swelling bonding interface; 91. Polymer chain interpenetration region. Detailed Implementation

[0028] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Certain embodiments of the invention will be described more fully below with reference to the accompanying drawings, and some, but not all, of these embodiments will be shown. In fact, various embodiments of the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the invention to meet applicable legal requirements.

[0029] In the description of this invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In this embodiment of the invention, a swelling-bonded and fixed dual-channel flexible pressure sensor and method are provided. Please refer to [reference needed]. Figures 1 to 11 As shown.

[0031] A swell-bonded dual-channel flexible pressure sensor includes an upper flexible substrate 1, an upper electrode layer 2, a first sensitive layer 3, an intermediate common electrode layer 4, a second sensitive layer 5, a lower electrode layer 6, and a lower flexible substrate 7, which are stacked sequentially from top to bottom.

[0032] The upper flexible substrate 1 and the lower flexible substrate 7 can be flexible insulating films such as PI film and PET film. In this embodiment, a PI film with a thickness of about 25 μm is preferred.

[0033] The upper electrode layer 2, the middle common electrode layer 4 and the lower electrode layer 6 all contain nano-silver / PDMS composite material, and the first sensitive layer 3 and the second sensitive layer 5 both contain graphene / PDMS composite material.

[0034] The nanosilver / PDMS composite material includes nanosilver and PDMS prepolymer. The nanosilver is one or more of silver nanowires, silver nanoparticles, and silver nanosheets, and the mass ratio of nanosilver to PDMS prepolymer is 8 wt.%-18 wt.%. In this embodiment, silver nanowires are preferred. The average diameter of the silver nanowires is 30 nm to 40 nm and the average length is 30 μm to 50 μm. They overlap each other in the PDMS matrix (PDMS prepolymer) to form a conductive network, so that the electrode layer can maintain conductive continuity under bending and compression conditions.

[0035] The graphene / PDMS composite material comprises graphene and PDMS prepolymer, with a graphene to PDMS prepolymer mass ratio of 0.5 wt.% to 5 wt.%. The PDMS prepolymer comprises PDMS base adhesive and curing agent, with a PDMS base adhesive to curing agent mass ratio of 3:1 to 10:1. In this embodiment, the graphene is preferably few-layer graphene powder with a sheet thickness of less than 5 nm and a lateral dimension of 1 μm to 5 μm. The graphene filler is used to improve the dielectric response of the graphene / PDMS composite material and enhance the detectability of capacitance changes without transforming the entire sensitive layer into a conductive layer.

[0036] The upper surface of the first sensitive layer 3 is provided with a dome microstructure 31, and the upper surface of the second sensitive layer 5 is provided with an inclined microcolumn structure 51.

[0037] The upper surface of the first sensitive layer 3 protrudes upward to form several hemispheres, and the array structure composed of several hemispheres forms a dome microstructure 31, and the dome microstructure 31 is integrally formed with the first sensitive layer 3.

[0038] The upper surface of the second sensitive layer 5 protrudes upward to form several cylindrical or frustum-shaped pillars. The central axis of the pillars is arranged obliquely relative to the thickness direction of the second sensitive layer 5. The array structure composed of several pillars forms an oblique micropillar structure 51, and the oblique micropillar structure 51 is integrally formed with the second sensitive layer 5.

[0039] The initial equivalent compressive stiffness of the first sensitive layer 3 is less than the initial equivalent compressive stiffness of the second sensitive layer 5, wherein the initial deformation threshold of the dome microstructure 31 is lower than the initial deformation threshold of the inclined microcolumn structure 51.

[0040] The initial equivalent compressive stiffness of the first sensitive layer 3 is less than that of the second sensitive layer 5. This difference in equivalent stiffness is adjusted by the radius of curvature, height, and array spacing of the dome microstructure 31, as well as the inclination angle, column height, column diameter, or cross-sectional dimensions of the inclined micro-column structure 51.

[0041] The first sensitive layer 3 and the second sensitive layer 5 have different microstructure morphologies. The dome microstructure 31 of the first sensitive layer 3 is adapted to preferentially undergo elastic compression deformation under low applied pressure F1 (first applied pressure); the inclined micropillar structure 51 of the second sensitive layer 5 is adapted to participate in support and compression deformation under high applied pressure F2 (second applied pressure). Both types of sensitive layers are integrally formed from graphene / PDMS composite material, avoiding secondary bonding between the inclined micropillar structure 51 and the sensitive layer matrix.

[0042] The upper electrode layer 2, the first sensitive layer 3 and the middle common electrode layer 4 constitute the first capacitance detection channel 81, and the middle common electrode layer 4, the second sensitive layer 5 and the lower electrode layer 6 constitute the second capacitance detection channel 82.

[0043] Under the first applied pressure, the first sensitive layer 3 preferentially compresses and deforms the second sensitive layer 5, increasing the capacitance change of the first capacitance detection channel 81; under the second applied pressure, the second sensitive layer 5 participates in supporting and compressing and deforming, increasing the capacitance change of the second capacitance detection channel 82; wherein, the first applied pressure is less than the second applied pressure.

[0044] Specifically, under low applied pressure F1, the dome microstructure 31 of the first sensitive layer 3 preferentially undergoes elastic compression, causing a significant capacitance change in the first capacitance detection channel 81. At this time, the second sensitive layer 5 mainly plays a supporting role, and the change in the second capacitance detection channel 82 is relatively small. As the applied pressure increases to high applied pressure F2, the first sensitive layer 3 is further compressed and tends to a lower gain state. The tilted micropillar structure 51 in the second sensitive layer 5 begins to undergo more significant compression or bending deformation, enhancing the response of the second capacitance detection channel 82.

[0045] A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer.

[0046] The swelling bonding interface 9 is not an independently set adhesive layer, but rather an interfacial bonding region formed by the interpenetration and solidification of polymer chains between the PDMS matrix surface layers of adjacent nano-silver / PDMS composite materials and the PDMS matrix surface layers of graphene / PDMS composite materials in a swollen state. In this way, stable interfacial bonding structures can be formed between the upper electrode layer 2 and the first sensitive layer 3, between the first sensitive layer 3 and the intermediate common electrode layer 4, between the intermediate common electrode layer 4 and the second sensitive layer 5, and between the second sensitive layer 5 and the lower electrode layer 6.

[0047] Since the adjacent electrode layers and the sensitive layer are bonded together through the swelling bonding interface 9, the relative slippage and contact hysteresis between layers are suppressed during dynamic loading, which is beneficial to improving the response stability during cyclic loading and high-frequency disturbance detection.

[0048] The swelling bonding interface 9 is a continuous or discontinuous interface bonding region, which covers at least a portion of the dome microstructure 31 of the first sensitive layer 3, a portion of the inclined micropillar structure 51 of the second sensitive layer 5, and the effective pressure-sensing region of the electrode layers (upper electrode layer 2, intermediate common electrode layer 4, and lower electrode layer 6).

[0049] The effective pressure-sensing region of the electrode layer is the overlapping region of the orthogonal projections of the upper electrode layer 2, the intermediate common electrode layer 4, and the lower electrode layer 6, which is the region where pressure response coupling occurs with the first sensitive layer 3 and the second sensitive layer 5.

[0050] The swelling bonding interface 9 is located between the end of the dome microstructure 31 and the upper electrode layer 2, between the lower surface of the first sensitive layer 3 and the intermediate common electrode layer 4, between the end of the inclined micropillar structure 51 and the intermediate common electrode layer 4, and between the lower surface of the second sensitive layer 5 and the lower electrode layer 6.

[0051] The swell-bonded dual-channel flexible pressure sensor of this embodiment takes the interface bonding of the swell-bonded interface 9 as the core, and improves the interlayer connection stability through the polymer chain interpenetration region 91 between the highly conductive nano-silver / PDMS electrode layer and the high dielectric graphene / PDMS sensitive layer; and forms a dual-capacitance detection channel by combining the dome microstructure 31, the inclined micro-pillar structure 51 and the intermediate common electrode layer 4. While maintaining the feasibility of the material system and process system, it improves the adaptability of the flexible pressure sensor to different pressure ranges and the dynamic response stability.

[0052] A method for fabricating a swellable bonded dual-channel flexible pressure sensor, used to fabricate the swellable bonded dual-channel flexible pressure sensor described in this embodiment, the method comprising the following steps: S1. Preparation of PDMS prepolymer; PDMS-based adhesive is mixed with curing agent and degassed to obtain PDMS prepolymer.

[0053] Specifically, take PDMS base adhesive and curing agent, control the mass ratio of the two to 5:1, and stir with a glass rod for 5 to 10 minutes to make the curing agent evenly dispersed in the PDMS base adhesive; then place the mixture in a vacuum environment to degas for 20 to 30 minutes until the mixture is clear and transparent and there are no obvious bubbles left, and obtain the PDMS prepolymer for use.

[0054] S2. Preparation of nano-silver / PDMS conductive paste and graphene / PDMS dielectric paste; Nano-silver was dispersed in chloroform, PDMS prepolymer was added, and the solvent was evaporated by stirring to obtain nano-silver / PDMS conductive paste.

[0055] Specifically, 1.2 g of silver nanowires were added to 50 mL of chloroform and magnetically stirred for 20 minutes at room temperature at a stirring speed of approximately 500 r / min to obtain a silver nanowire dispersion. While maintaining stirring, 10 g of the PDMS prepolymer prepared above was slowly added to the silver nanowire dispersion, and stirring was continued at approximately 60°C to allow the chloroform to gradually evaporate. When the mixture turned into a silver-gray paste and no obvious solvent odor was detected, heating and stirring were stopped, and after degassing, a nano-silver / PDMS conductive paste was obtained. The amount of silver nanowires added was approximately 12 wt.% based on the mass of the PDMS prepolymer.

[0056] Graphene was dispersed in chloroform, PDMS prepolymer was added, and the solvent was stirred to evaporate, thus obtaining a graphene / PDMS dielectric paste.

[0057] Specifically, 0.2 g of few-layer graphene was added to 50 mL of chloroform and magnetically stirred or ultrasonically dispersed to form a relatively uniform pre-dispersion system. Then, 10 g of the PDMS prepolymer obtained above was added to the graphene dispersion, and the mixture was continuously stirred at approximately 60°C to allow the chloroform to evaporate. After the system formed a black, uniform paste, degassing was performed to obtain the graphene / PDMS dielectric paste. The amount of graphene added was approximately 2 wt.% based on the mass of the PDMS prepolymer.

[0058] It should be noted that, in this embodiment, chloroform can be used as both a pre-dispersion solvent for nano-silver and graphene fillers and an interfacial swelling solvent in the subsequent swelling and bonding steps. The chloroform used for slurry preparation is evaporated and removed during heating and stirring to avoid residual solvent affecting the curing state and dielectric properties of the electrode layer and sensitive layer; the chloroform used for swelling and bonding acts briefly on the surface to be bonded to induce micro-swelling of the surface PDMS segments.

[0059] S3. Prepare the electrode layer and the sensitive layer; Nano-silver / PDMS conductive paste is screen-printed to form upper electrode layer 2 and lower electrode layer 6. Nano-silver / PDMS conductive paste is spin-coated, scraped, or transferred to form intermediate common electrode layer 4.

[0060] Specifically, the upper flexible substrate 1 and the lower flexible substrate 7 are cleaned and surface-treated before the electrode layer is formed. The upper flexible substrate 1 and the lower flexible substrate 7 can be made of PI film. The PI film is ultrasonically cleaned for 15 minutes each in acetone, anhydrous ethanol and deionized water in sequence to remove surface grease and particulate contamination. After drying, it is treated with oxygen plasma to generate polar groups on its surface to enhance the adhesion stability between the nano-silver / PDMS conductive paste and the flexible substrate.

[0061] A 300-mesh stainless steel screen was fabricated with the pre-defined electrode effective area, lead wires, and pad patterns. A surface-treated PI film was fixed to a printing table, and nano-silver / PDMS conductive paste was placed on one side of the screen. Printing was performed at a squeegee angle of approximately 45° and a squeegee speed of approximately 15 cm / s. After printing, the paste was cured in an 80°C forced-air oven for approximately 1 hour to obtain an upper electrode layer 2 and a lower electrode layer 6 with a thickness of approximately 20 μm. Because the nano-silver conductive network is embedded in the PDMS matrix, the cured electrode surface still retains the PDMS matrix surface layer, which is beneficial for the subsequent formation of a swelling bonding interface 9.

[0062] Nano-silver / PDMS conductive paste is spin-coated onto a PET release film treated with fluorosilane or other low surface energy at a spin-coating speed of approximately 2000 r / min for approximately 60 seconds. It is then cured at 80°C for approximately 1 hour to obtain a flexible conductive film with a thickness of approximately 20 μm to 30 μm. It is then cut into an intermediate common electrode layer 4 that matches the effective pressure-sensitive area by laser cutting or die-cutting, and the corresponding electrode leads are formed.

[0063] The graphene / PDMS dielectric paste is replicated and molded using a dome microstructure mold to obtain the first sensitive layer 3, and the graphene / PDMS dielectric paste is replicated and molded using an inclined micropillar structure mold to obtain the second sensitive layer 5.

[0064] Specifically, a reverse mold (dome microstructure mold) with a dome cavity array is first prepared, and the mold surface is treated with an anti-sticking agent. The inner contour of the dome cavity is hemispherical. Then, graphene / PDMS dielectric paste is poured or coated onto the mold surface to fully fill the dome cavity. After vacuum degassing, excess paste is scraped off. The mold is then pre-cured or fully cured at 65°C to 80°C, and demolded after cooling to obtain the first sensitive layer 3 with dome microstructure 31. The dome microstructure 31 and the first sensitive layer 3 substrate are continuously formed from the same graphene / PDMS composite material, and there is no independent bonding interface between them.

[0065] A reverse mold (tilted micropillar structure mold) with an array of tilted micropillar cavities is fabricated using micromachining, photolithography, laser processing, or precision mold making methods. The mold surface is then treated to prevent sticking. The inner contour of each tilted micropillar cavity is a cylindrical or frustum-shaped column, with the central axis of the column tilted relative to the thickness direction of the second sensitive layer 5. Graphene / PDMS dielectric paste is filled into the mold cavities, and after vacuum degassing, leveling, and heat curing, the mold is demolded to obtain the second sensitive layer 5 with the tilted micropillar structure 51. The central axis of each column in the tilted micropillar structure 51 is tilted relative to the thickness direction of the second sensitive layer 5, thereby providing support and space for compression deformation under high pressure.

[0066] S4. A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer; Specifically, before assembly, an interface treatment solution is prepared. Take 1 g of PDMS base adhesive and 0.1 g of curing agent, add them to 100 mL of chloroform, and stir or sonicate to form a diluted solution. The chloroform in this interface treatment solution is used to induce micro-swelling of the PDMS matrix surface layer to be bonded, while the PDMS base adhesive and curing agent are used to replenish curable segments at the interface.

[0067] The interface treatment solution contains low levels of PDMS base adhesive and curing agent, and its main function is to supplement the curable chain segments at the interface. After subsequent curing, it forms a polymer chain interpenetrating region 91 together with the PDMS chain segments of the adjacent surface layer, rather than forming an independent adhesive layer with a distinguishable thickness.

[0068] The electrode layer and the sensitive layer to be bonded are treated with an interface treatment solution containing chloroform, which causes the surface PDMS chain segments of the surface to be bonded to undergo micro-swelling.

[0069] Specifically, the surfaces to be bonded, namely the upper electrode layer 2, the intermediate common electrode layer 4, and the lower electrode layer 6, are laid flat and spin-coated with an interface treatment solution at a speed of approximately 1000 r / min. For the first sensitive layer 3 and the second sensitive layer 5, their edges are held with tweezers, and the surfaces of the microstructures to be bonded are briefly in contact with or immersed in the interface treatment solution for approximately 2 to 5 seconds before being removed. This allows chloroform to wet the microstructure surfaces and induce micro-swelling of the surface PDMS, while avoiding excessive swelling that could cause the dome microstructure 31 or the tilted micropillar structure 51 to collapse or deform.

[0070] The upper flexible substrate 1, upper electrode layer 2, first sensitive layer 3, middle common electrode layer 4, second sensitive layer 5, lower electrode layer 6 and lower flexible substrate 7 are aligned and bonded in that order.

[0071] Specifically, the layers are stacked and assembled in the following order from top to bottom: upper flexible substrate 1, upper electrode layer 2, first sensitive layer 3, intermediate common electrode layer 4, second sensitive layer 5, lower electrode layer 6 and lower flexible substrate 7 to form a stacked structure, with the first sensitive layer 3 located between the upper electrode layer 2 and the intermediate common electrode layer 4, and the second sensitive layer 5 located between the intermediate common electrode layer 4 and the lower electrode layer 6.

[0072] Light pressure and heat curing cause the PDMS chain segments of adjacent surface layers to interpenetrate, entangle, and solidify, forming a swollen bonding interface 9.

[0073] Specifically, the aligned laminated structure is placed in a hot press or flat plate press, and a slight pre-pressure of about 1 kPa to 2 kPa is applied to ensure that the contact area between the electrode layer and the corresponding sensitive layer is fully adhered, but without crushing the dome microstructure 31 and the tilted micropillar structure 51; then the pressure is maintained and the temperature is raised to about 95°C for about 3 hours for curing. During the heating process, chloroform gradually evaporates from the interface, and PDMS segments from adjacent sides continue to diffuse, entangle, and cross-link at the interface, eventually forming a swollen bonded interface 9.

[0074] S5, the electrode is led out, and a swollen bonded solid-bonded dual-channel flexible pressure sensor is obtained.

[0075] The present embodiment has now been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the swelling-bonded and fixed dual-channel flexible pressure sensor and method of the present invention. Of course, the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A swelling-bonded, fixed-type dual-channel flexible pressure sensor, characterized in that, It includes an upper flexible substrate, an upper electrode layer, a first sensitive layer, an intermediate common electrode layer, a second sensitive layer, a lower electrode layer, and a lower flexible substrate, which are stacked sequentially from top to bottom; The upper electrode layer, the middle common electrode layer and the lower electrode layer all contain nano-silver / PDMS composite material, and the first sensitive layer and the second sensitive layer both contain graphene / PDMS composite material; The upper surface of the first sensitive layer is provided with a dome microstructure, and the upper surface of the second sensitive layer is provided with an inclined microcolumn structure. The upper electrode layer, the first sensitive layer, and the middle common electrode layer constitute the first capacitance detection channel, and the middle common electrode layer, the second sensitive layer, and the lower electrode layer constitute the second capacitance detection channel. A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer; The swelling bonding interface is an interfacial bonding region formed by the interpenetration and solidification of polymer chains between the PDMS matrix surface layer in the adjacent layers of the nano-silver / PDMS composite material and the PDMS matrix surface layer in the graphene / PDMS composite material in the swollen state.

2. The swelling bonded rigid dual-channel flexible pressure sensor according to claim 1, characterized in that, The swelling bonding interface is a continuous or discontinuously distributed interface bonding region, which covers at least the dome microstructure region of the first sensitive layer, the inclined micropillar structure region of the second sensitive layer, and the effective pressure-sensing region of the electrode layer.

3. The swelling bonded and fixed dual-channel flexible pressure sensor according to claim 2, characterized in that, The swelling bonding interfaces are located between the end of the dome microstructure and the upper electrode layer, between the lower surface of the first sensitive layer and the intermediate common electrode layer, between the end of the inclined micropillar structure and the intermediate common electrode layer, and between the lower surface of the second sensitive layer and the lower electrode layer.

4. The swelling bonded and fixed dual-channel flexible pressure sensor according to claim 1, characterized in that, The upper surface of the first sensitive layer protrudes upward to form several hemispheres, and the array structure composed of several hemispheres forms the dome microstructure, and the dome microstructure is integrally formed with the first sensitive layer.

5. The swelling bonded and fixed dual-channel flexible pressure sensor according to claim 1, characterized in that, The upper surface of the second sensitive layer protrudes upward to form several cylindrical or frustum-shaped pillars. The central axis of the pillars is arranged obliquely relative to the thickness direction of the second sensitive layer. The array structure composed of several pillars forms the oblique micropillar structure, and the oblique micropillar structure is integrally formed with the second sensitive layer.

6. The swelling bonded and fixed dual-channel flexible pressure sensor according to claim 1, characterized in that, The initial equivalent compressive stiffness of the first sensitive layer is less than that of the second sensitive layer.

7. A swelling bonded and fixed dual-channel flexible pressure sensor according to claim 6, characterized in that, The initial deformation threshold of the dome microstructure is lower than that of the inclined microcolumn structure.

8. A swelling-bonded, fixed-connection type dual-channel flexible pressure sensor according to claim 6, characterized in that, Under a first applied pressure, the first sensitive layer preferentially compresses and deforms the second sensitive layer, increasing the capacitance change of the first capacitance detection channel; under a second applied pressure, the second sensitive layer participates in supporting and compressing deformation, increasing the capacitance change of the second capacitance detection channel; wherein, the first applied pressure is less than the second applied pressure.

9. A swelling bonded and fixed dual-channel flexible pressure sensor according to claim 1, characterized in that, The nano-silver / PDMS composite material includes nano-silver and PDMS prepolymer, wherein the nano-silver is one or more of silver nanowires, silver nanoparticles, and silver nanosheets, and the mass ratio of the nano-silver to the PDMS prepolymer is 8 wt.%-18 wt.%; the graphene / PDMS composite material includes graphene and PDMS prepolymer, wherein the mass ratio of the graphene to the PDMS prepolymer is 0.5 wt.%-5 wt.%; the PDMS prepolymer includes PDMS base adhesive and curing agent, wherein the mass ratio of the PDMS base adhesive to the curing agent is 3:1-10:

1.

10. A method for fabricating a swellable bonded dual-channel flexible pressure sensor, used to fabricate the swellable bonded dual-channel flexible pressure sensor according to any one of claims 1 to 9, characterized in that, The method includes the following steps: S1. Preparation of PDMS prepolymer; PDMS-based adhesive is mixed with curing agent and degassed to obtain PDMS prepolymer; S2. Preparation of nano-silver / PDMS conductive paste and graphene / PDMS dielectric paste; Nano-silver was dispersed in chloroform, PDMS prepolymer was added, and the solvent was evaporated by stirring to obtain nano-silver / PDMS conductive paste; Graphene was dispersed in chloroform, PDMS prepolymer was added, and the solvent was evaporated by stirring to obtain graphene / PDMS dielectric paste; S3. Prepare the electrode layer and the sensitive layer; Nano-silver / PDMS conductive paste is screen-printed to form an upper electrode layer and a lower electrode layer. Nano-silver / PDMS conductive paste is then spin-coated, scraped, or transferred to form an intermediate common electrode layer. The graphene / PDMS dielectric paste is replicated and molded using a dome microstructure mold to obtain the first sensitive layer, and the graphene / PDMS dielectric paste is replicated and molded using an inclined micropillar structure mold to obtain the second sensitive layer. S4. A swollen bonding interface is formed between adjacent electrode layers and the sensitive layer; The electrode layer and the sensitive layer to be bonded are treated with an interface treatment solution containing chloroform, which causes the surface PDMS chain segments of the surface to be bonded to undergo micro-swelling. Align and bond the upper flexible substrate, upper electrode layer, first sensitive layer, middle common electrode layer, second sensitive layer, lower electrode layer and lower flexible substrate in that order; Light pressure and heat curing cause the PDMS chain segments of adjacent surface layers to interpenetrate, entangle, and solidify, forming a swollen bonding interface; S5, the electrode is led out, and a swollen bonded solid-bonded dual-channel flexible pressure sensor is obtained.

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