A pressure detection system

Abstract

The application discloses a pressure detection system, and relates to the technical field of intelligent wearing, which comprises the following steps: 1) a flexible base layer is used for adhering to the skin and perceiving the external slight pressure change; 2) a micro column array layer is composed of a plurality of micro column structures and is used for amplifying and conducting the pressure change perceived by the flexible base layer; 3) a flexible gel sensing layer is used for receiving the pressure transmitted by the micro column array layer and generating an electric signal; and 4) a packaging layer is arranged. The flexible gel sensing layer is provided with an interdigital electrode layer, the electric signal of the flexible gel sensing layer changes with the change of the applied pressure, and the detection of the pressure electric signal is realized through the interdigital electrode layer. The design can realize the high-sensitivity response to the slight pressure change, significantly amplify the micro-pressure signal, and overcome the hysteresis effect problem commonly existing in traditional silica gel or metal film materials, so that the response speed of the sensor is greatly improved.

Description

Technical Field

[0001] This application relates to the field of smart wearable technology, and more particularly to a pressure detection system, which can be widely used in smart wearable devices, clinical physiological parameter monitoring and remote health management. Background Technology

[0002] With the widespread application of smart wearable medical devices in continuous clinical monitoring and individual health management, photoplethysmography (PPG) technology has become one of the core methods for assessing cardiovascular physiological parameters. However, current mainstream wearable PPG sensors still face significant challenges in dynamic monitoring environments: the contact pressure between the sensor and the skin surface is prone to fluctuations with movement, leading to baseline drift, distortion, and increased noise in the PPG signal. Furthermore, existing devices lack sufficient signal amplification capabilities in the micro-pressure domain, making it difficult to simultaneously achieve high-sensitivity detection and wide-area stress recognition, resulting in inaccurate data measurements. Summary of the Invention

[0003] This application proposes a pressure detection system, particularly suitable for PPG sensors, to significantly improve their response speed, sensitivity, and detection range.

[0004] The pressure detection of the present invention includes the following components arranged sequentially:

[0005] A flexible base layer is used to conform to the skin and sense minute changes in external pressure.

[0006] The micropillar array layer, composed of multiple micropillar structures, is used to amplify and transmit pressure changes sensed by the flexible substrate layer;

[0007] A flexible gel sensing layer is used to receive the pressure transmitted by the micropillar array layer and generate an electrical signal; and

[0008] Encapsulation layer;

[0009] The flexible gel sensing layer is provided with an interdigitated electrode layer. The electrical signal of the flexible gel sensing layer changes with the applied pressure, and the pressure electrical signal is detected through the interdigitated electrode layer.

[0010] It should be noted that the flexible gel sensing layer converts the pressure received from the micropillar array layer into an electrical signal through force-to-electricity conversion. The electrical signal of the flexible gel sensing layer undergoes a repeatable and reversible response change with the applied pressure, and the interdigitated electrode layer enables highly sensitive detection of the pressure electrical signal.

[0011] This application achieves high-gain stress-electric signal conversion through an ion-hydrogel coupled with a micropillar structure, enabling highly sensitive response to minute pressure changes and amplifying minute pressure signals. It also overcomes the hysteresis effect commonly found in traditional silicone or metal thin film materials, thereby significantly improving the sensor's response speed.

[0012] In some embodiments, the flexible gel sensing layer comprises an ion-hydrogel microsphere crosslinking agent, a crosslinked gel matrix, and conductive ions. The ion-hydrogel microsphere crosslinking agent is polymerized from zwitterionic monomers and carboxyl polymer chains. The crosslinked gel matrix is ​​composed of gel monomers and polymer chains. The crosslinked gel matrix and conductive ions form a stable metal coordination network structure through carboxyl coordination, endowing the material with excellent mechano-electric response properties and structural stability.

[0013] The zwitterionic monomers include at least one of SBMA (sulfobetaine methacrylate) and DMAPS ([2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium inner salt). These zwitterionic monomers contain both anions and cations, which can form a stronger electrostatic coupling effect. They provide ionic groups, which can improve the ionic conductivity of the flexible gel sensing layer. They contain carboxyl groups that coordinate with iron ions, and can bind to primary amine groups to form amide bonds, thereby forming a stable sensing layer and improving the mechanical properties of the hydrogel network; and / or,

[0014] Carboxyl-based polymer chains include at least one of polyaspartic acid and its derivatives, polylysine and its derivatives, alginate and its derivatives, and hyaluronic acid and its derivatives. These carboxyl-based polymer chains contain ionic groups, which facilitates electrical conductivity and can improve the ionic conductivity of the flexible gel sensing layer; and / or,

[0015] The gel monomer includes at least one of acrylamide and its derivatives, acrylic acid and its derivatives, and N,N-dimethylacrylamide and its derivatives; and / or

[0016] The polymer chain includes at least one of polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), and gelatin to enhance the gel's flexibility and biocompatibility; and / or

[0017] Conductive ions include Zn 2+ Fe 3+ Ca 2+ and Mg 2+ At least one of these ions forms a tunable three-dimensional metal coordination network structure with carboxyl ligands through dynamic coordination, thereby constructing a sensing channel with high ionic conductivity and endowing the gel with excellent pressure response sensitivity, flexible adhesion properties and self-healing potential.

[0018] Specifically, the ionic hydrogel microsphere crosslinking agent is synthesized by reverse emulsion polymerization of zwitterionic monomers and carboxyl macromolecular chains. Subsequently, the carboxyl functional groups on the surface of the microspheres are activated using a glycidyl methacrylate (GMA) / tetra-n-butylammonium bromide (TBAB) solution system, and GMA is grafted to form a multifunctional microsphere structure, which significantly improves the crosslinking efficiency and compatibility between the microspheres and the hydrogel network.

[0019] In the optimized formulation design, the mass fractions of the zwitterionic monomer, carboxyl macromolecular chain, and GMA graft chain are 15-20 wt%, 5-10 wt%, and 2.5-5 wt%, respectively, with the balance being solvent. This achieves a synergistic enhancement of the chemical stability, interfacial activity, and ion channel regulation capability of the microsphere structure. This ion-hydrogel microsphere crosslinking agent not only provides abundant anion and cation sites, serving as functional ion channels for the hydrogel matrix, but also forms a stable and flexible three-dimensional network structure through physical crosslinking (such as hydrogen bonding and electrostatic coupling) and covalent crosslinking, significantly enhancing the overall mechanical strength and fatigue resistance of the gel.

[0020] In some embodiments, the molar coordination ratio of the conductive ions to the carboxyl ligands in the crosslinked gel matrix is ​​1:(3~6). This ratio helps to maintain the effectiveness and flexibility of ion migration channels while ensuring network strength, achieving efficient electron-ion synergistic conduction, improving response speed and reducing hysteresis error, thereby enhancing the material's flexibility, fatigue resistance, and the overall stability and dynamic performance of the pressure sensing system; and / or,

[0021] The crosslinking density of the flexible gel sensing layer increases in a gradient from the micropillar array layer to the encapsulation layer. The crosslinking density gradually increases along the thickness direction from the micropillar array layer to the encapsulation layer. Crosslinking density refers to the number of crosslinked nodes per unit volume, reflecting the spatial density and mechanical stiffness of the gel network. This gradient structure design creates a soft, highly deformable, low-crosslinking region near the micropillar array layer to enhance the sensitivity to initial micro-pressure signals; while a highly crosslinked, high-elastic-modulus support region near the encapsulation layer is formed to withstand external loads and prevent premature crushing failure. This gradient crosslinking design helps to construct a dual-channel enhancement region for both mechanical and electrical signals, significantly improving the dynamic linear range, resolution, and durability of the sensing system, and effectively suppressing hysteresis and signal drift caused by repeated loading.

[0022] In some embodiments, the flexible gel sensing layer includes a first layer and a second layer, with the first layer located between the flexible substrate layer and the second layer. The material of the second layer is doped with carbon nanotubes (CNTs) to form a dense conductive network structure. This composite design significantly improves the volumetric conductivity of the second layer, enhancing its lateral electrical signal conduction capability and vertical strain response sensitivity during pressure loading.

[0023] In some embodiments, the thickness ratio of the first layer to the second layer is (1~3):1. This ratio is configured to balance flexible fit with force-to-electrical signal gradient conversion capability, thereby achieving excellent flexible distribution response and vertical conductive coupling effect, while ensuring the sensor's strain matching capability and efficient signal transmission performance under complex biomechanical conditions; and / or,

[0024] The second layer contains carbon nanotubes at a mass ratio of 0.3% to 0.8%. This doping concentration enables the construction of uniform conductive pathways without significantly increasing the overall stiffness of the composite material, optimizing pressure-impedance coupling performance and improving signal amplification. The introduction of carbon nanotubes not only endows the material with high conductivity but also enhances the mechanical robustness and conductive stability of the network through π-π stacking interactions, further improving the overall dynamic response performance and reliability under multi-cycle loading. This allows for the construction of a highly efficient force-to-electricity conversion conductive network while maintaining flexibility and adhesion.

[0025] In some embodiments, the micropillar array layer includes multiple micropillars, and the micropillar structure is a multi-level biomimetic helical cavity structure, including an outer helical flow-guiding shell and an inner nested slow-release cavity, wherein:

[0026] The spiral guiding shell has an asymmetric spin-helical structure along the axial direction, which can achieve radial-axial coordinated deformation under small pressure, significantly amplifying the local stress transmission amplitude of the flexible substrate and enhancing the primary triggering sensitivity; and / or,

[0027] The sustained-release cavity is designed as a multi-level collapse response structure, capable of collapsing layer by layer under applied pressure. This provides multiple deformation amplification effects while effectively protecting the integrity of the underlying structure. The multi-level cavity structure, by controlling the collapse sequence of the microstructure, achieves nonlinear stress amplification and multimodal stress response, significantly improving the strain output and electrical signal amplitude modulation capability of the ion hydrogel layer; and / or,

[0028] The cone angle of the micropillars is 30°~60°, which is used to guide the orderly construction of ion migration channels, expand the dynamic detection range of the sensor, and realize the tunable stiffness gradient of the microstructure.

[0029] The height-to-diameter ratio of the micropillar is 0.2~0.8, used to synergistically control the compressive deformation range and structural springback capability, thereby maintaining structural stability while enhancing the deformability of the micropillar and improving strain amplitude transmission efficiency; and / or,

[0030] The micropillars, with a height of 50-150 μm, can precisely amplify minute biomechanical disturbances to match the flexible mechanical properties and response frequency band of human skin.

[0031] It should be noted that in other embodiments, the cross-sectional shape of the micropillar structure can also be conical, stepped columnar, wavy, or a multi-level helical cavity structure, with a biomimetic helical-cavity combination structure being preferred to achieve superior multidimensional mechanical response performance. This multi-scale biomimetic structure can achieve controllable and reversible radial-axial composite deformation under small vertical loads; under larger pressure conditions, it exhibits layer-by-layer collapse extension response characteristics, thereby significantly amplifying the deformation of the flexible substrate and improving the stress-induced electrical signal amplitude of the flexible gel sensing layer. Overall, this design significantly improves the system's force-to-electrical conversion efficiency and detection sensitivity, effectively suppresses hysteresis effects and interface stress concentration, and significantly enhances the stability of the microstructure and the overall mechanical durability of the device.

[0032] In some embodiments, the interdigitated electrode layer consists of multiple distributed electrode units. The density of these electrode units increases gradually along the pressure conduction direction perpendicular to the flexible substrate (i.e., from the micropillar array layer to the encapsulation layer), thereby forming an asymmetric electric field sensing region. This asymmetric arrangement strategy can significantly improve the sensitivity of electrical signal extraction at different strain depths, enhance the system's ability to distinguish minute pressure gradient changes, and achieve partitioned acquisition of multi-level pressure signals. Through the gradient distribution of the interdigitated electrode structure, the spacing between adjacent electrodes gradually varies along the pressure loading direction, forming a resistance gradient amplification effect, thereby significantly enhancing the sensing ability and signal amplification effect of minute contact pressure changes, and improving the overall sensitivity and real-time response capability of the sensor. This design can effectively capture low-frequency minute pressure disturbances, meet the requirements of high-sensitivity detection, and significantly suppress background noise interference, optimizing the signal-to-noise ratio.

[0033] In some embodiments, the distribution density of the electrodes ranges from 8 to 24 electrodes / cm²; and / or,

[0034] The spacing Δd between adjacent electrode units is 20–100 μm. By precisely controlling the electrode distribution density and spacing parameters, a reasonable resistance gradient distribution can be formed along the pressure loading path, creating an asymmetric electric field distribution to enhance the resolution and detection sensitivity of minute pressure signals. Simultaneously, this structural design helps to effectively suppress electric field crosstalk effects, ensuring stable acquisition and reconstruction of multi-point distributed signals, and improving the reliability and adaptability of the sensor under complex physiological environments. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of a pressure detection system according to an embodiment of this application.

[0037] Figure 2 This is an exploded view of a pressure detection system according to an embodiment of this application.

[0038] Figure 3 This is a schematic diagram of the flexible gel sensing layer structure of a pressure detection system according to an embodiment of this application.

[0039] Explanation of icon numbers:

[0040] 100 Pressure detection system; 1 Flexible substrate layer; 2 Micropillar array layer; 3 Flexible gel sensing layer; 31 Interdigitated electrode layer; 32 First layer; 33 Second layer; 4 Encapsulation layer. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0042] With the widespread application of wearable medical devices in clinical monitoring, chronic disease management, and personalized health assessment, PPG technology has become an important means of non-invasive monitoring of cardiovascular function. However, existing wearable PPG sensors still face significant technical bottlenecks in practical applications: the sensor-skin contact interface is easily affected by external interference (such as motion artifacts and environmental vibrations) and physiological activities (such as gait changes, respiration, and muscle contraction), leading to frequent fluctuations in contact pressure, which in turn causes baseline drift in the PPG signal and increased noise interference. Furthermore, existing pressure detection components are difficult to adapt to complex dynamic monitoring scenarios, generally exhibiting significant response hysteresis, slow dynamic response speed, insufficient mechanical compliance, and limited sensitivity, resulting in the inability to correct contact pressure in a timely manner and affecting the stability and accuracy of the detection data.

[0043] To address the aforementioned technical challenges, this application provides a pressure detection system. This system achieves high-sensitivity detection of minute external pressure disturbances by constructing a flexible microstructure layer, an ion-conducting network, and a gradient-distributed electrode array. This effectively alleviates signal drift and noise problems in existing technologies, significantly improves response speed, and extends the detection range, thus providing an innovative solution for high-performance PPG sensors and wearable health monitoring devices.

[0044] Firstly, such as Figure 1 and Figure 2 As shown, this application provides a pressure detection system 100, comprising the following components arranged sequentially:

[0045] Flexible base layer 1, used to conform to the skin and sense minute changes in external pressure;

[0046] The micropillar array layer 2, composed of multiple micropillar structures, is used to amplify and transmit pressure changes sensed by the flexible substrate layer; and

[0047] The flexible gel sensing layer 3 is used to receive the pressure transmitted by the micropillar array layer and generate an electrical signal;

[0048] Encapsulation layer 4 is used to protect the structural stability of the pressure detection system 100;

[0049] The flexible gel sensing layer is provided with an interdigitated electrode layer. The electrical signal of the flexible gel sensing layer changes with the applied pressure, and the pressure electrical signal is detected through the interdigitated electrode layer.

[0050] It should be noted that the flexible gel sensing layer converts the pressure received from the micropillar array layer into an electrical signal through force-to-electricity conversion. The electrical signal of the flexible gel sensing layer undergoes a repeatable and reversible response change with the applied pressure, and the interdigitated electrode layer enables highly sensitive detection of the pressure electrical signal.

[0051] This application achieves high-gain stress-electric signal conversion through an ion-hydrogel coupled with a micropillar structure, enabling highly sensitive response to minute pressure changes and amplifying minute pressure signals. It also overcomes the hysteresis effect commonly found in traditional silicone or metal thin film materials, thereby significantly improving the sensor's response speed.

[0052] In some embodiments, the flexible gel sensing layer comprises an ion-hydrogel microsphere crosslinking agent, a crosslinked gel matrix, and conductive ions. The ion-hydrogel microsphere crosslinking agent is polymerized from zwitterionic monomers and carboxyl polymer chains. The crosslinked gel matrix is ​​composed of gel monomers and polymer chains. The crosslinked gel matrix and conductive ions form a stable metal coordination network structure through carboxyl coordination, endowing the material with excellent mechano-electric response properties and structural stability.

[0053] The zwitterionic monomers include at least one of SBMA (sulfobetaine methacrylate) and DMAPS ([2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium inner salt). The zwitterionic monomers contain both anions and cations, which can form a stronger electrostatic coupling effect, provide ionic groups, and can improve the ionic conductivity of the flexible gel sensing layer. They contain carboxyl groups that combine with iron ions for coordination, and can combine with primary amine groups to form amide bonds, thereby forming a stable sensing layer and improving the mechanical properties of the hydrogel network.

[0054] Carboxyl polymer chains include at least one of polyaspartic acid and its derivatives, polylysine and its derivatives, alginate and its derivatives, and hyaluronic acid and its derivatives. The above-mentioned carboxyl polymer chains contain ionic groups, which are beneficial for conductivity and can improve the ionic conductivity of the flexible gel sensing layer.

[0055] The gel monomers include at least one of acrylamide and its derivatives, acrylic acid and its derivatives, and N,N-dimethylacrylamide and its derivatives.

[0056] The polymer chains include at least one of polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), and gelatin to enhance the gel's flexibility and biocompatibility.

[0057] Conductive ions include Zn 2+ Fe 3+ Ca 2+ and Mg 2+ At least one of these ions forms a tunable three-dimensional metal coordination network structure with carboxyl ligands through dynamic coordination, thereby constructing a sensing channel with high ionic conductivity and endowing the gel with excellent pressure response sensitivity, flexible adhesion properties and self-healing potential.

[0058] Specifically, the ionic hydrogel microsphere crosslinking agent is synthesized by reverse emulsion polymerization of zwitterionic monomers and carboxyl macromolecular chains. Subsequently, the carboxyl functional groups on the surface of the microspheres are activated using a glycidyl methacrylate (GMA) / tetra-n-butylammonium bromide (TBAB) solution system, and GMA is grafted to form a multifunctional microsphere structure, which significantly improves the crosslinking efficiency and compatibility between the microspheres and the hydrogel network.

[0059] In the optimized formulation design, the mass fractions of the zwitterionic monomer, carboxyl macromolecular chain, and GMA graft chain are 15-20 wt%, 5-10 wt%, and 2.5-5 wt%, respectively, with the balance being solvent. This achieves a synergistic enhancement of the chemical stability, interfacial activity, and ion channel regulation capability of the microsphere structure. This ion-hydrogel microsphere crosslinking agent not only provides abundant anion and cation sites, serving as functional ion channels for the hydrogel matrix, but also forms a stable and flexible three-dimensional network structure through physical crosslinking (such as hydrogen bonding and electrostatic coupling) and covalent crosslinking, significantly enhancing the overall mechanical strength and fatigue resistance of the gel.

[0060] In conjunction with the first aspect, in some embodiments provided in this application, the molar coordination ratio between conductive ions and carboxyl ligands in the flexible gel sensing layer 3 is preferably 1:(3~6). The molar coordination ratio refers to the number of carboxyl functional groups that can be coordinated to a unit metal ion. This ratio helps to maintain the effectiveness and flexibility of ion migration channels while ensuring network strength, achieving efficient electron-ion synergistic conduction, improving response speed, and reducing hysteresis errors, thereby enhancing the material's flexibility, fatigue resistance, and the overall stability and dynamic performance of the pressure sensing system.

[0061] In conjunction with the first aspect, in some embodiments provided in this application, the crosslinking density of the flexible gel sensing layer 3 increases progressively from the micropillar array layer 2 to the encapsulation layer 4. The crosslinking density of the flexible gel sensing layer 3 refers to the number of crosslinking points forming a stable network structure per unit volume, representing the spatial density and mechanical stiffness of the gel network. Its progressive increase from the micropillar array layer 2 to the encapsulation layer 4 allows for the formation of a soft, highly deformable, low-crosslinked region near the micropillar array layer, enhancing the initial micro-pressure response sensitivity. Conversely, a highly crosslinked, high-elastic-modulus support region is constructed near the encapsulation layer to withstand larger external loads and prevent premature yielding or collapse. This gradient structure facilitates the construction of a distributed enhancement region for both mechanical and electrical signals, significantly improving the overall dynamic linear range, resolution, and mechanical stability of the pressure sensing system, and effectively reducing hysteresis and signal drift caused by multiple loading cycles.

[0062] In conjunction with the first aspect, in some embodiments provided in this application, such as Figure 3As shown, the flexible gel sensing layer 3 includes a first layer 32 and a second layer 33. The first layer 32 is disposed between the flexible substrate layer 1 and the second layer 33. The first layer 32 is used to buffer the primary pressure load and improve the interfacial bonding strength. The material of the second layer 33 is doped with carbon nanotubes (CNTs) to enhance the network structure. This enhances the lateral conduction capability of electrical signals and the sensitivity of vertical strain response. This composite structure design helps to significantly improve the volume conductivity of the second layer, enhance the transmission efficiency of the vertical pressure response signal, optimize the accuracy and stability of the signal, and improve the structural stability and durability of the device under multiple loading cycles.

[0063] In conjunction with the first aspect, in some embodiments provided in this application, the thickness ratio of the first layer 32 to the second layer 33 is (1~3):1; this ratio is configured to balance flexible fit and force-to-electrical signal gradient conversion capability, thereby achieving excellent flexible distribution response and vertical conductive coupling effect, while ensuring the strain matching capability and efficient signal transmission performance of the sensor under complex biomechanical conditions.

[0064] In conjunction with the first aspect, in some embodiments provided in this application, the carbon nanotubes account for 0.3% to 0.8% of the mass of the material in the second layer 33. This doping concentration can construct a uniform conductive path without significantly increasing the overall stiffness of the composite material, optimizing pressure-impedance coupling performance and improving signal amplification. The introduction of carbon nanotubes not only endows the material with high electrical conductivity, but also enhances the mechanical robustness and conductive stability of the network through π-π stacking, further improving the overall dynamic response performance and reliability under multi-cycle loading of the system, and constructing a highly efficient force-to-electric conversion conductive network while ensuring flexibility and adhesion performance.

[0065] In conjunction with the first aspect, in some embodiments provided in this application, the micropillar array layer 2 includes multiple micropillars. The micropillar structure is a multi-level biomimetic helical cavity structure, including an outer helical flow-guiding shell and an inner nested slow-release cavity. The helical flow-guiding shell has an axially asymmetric spin-helical shape, capable of generating rapid radial-axial coordinated deformation under minute pressure, significantly amplifying the local deformation amplitude of the flexible substrate and improving primary trigger sensitivity. The slow-release cavity is designed as a multi-level collapse response structure, capable of collapsing layer by layer under applied pressure, providing multiple deformation amplification effects and effectively protecting the integrity of the underlying structure. This multi-level cavity structure, by controlling the microstructure collapse sequence, achieves nonlinear stress amplification and multimodal stress response, significantly improving the strain output and electrical signal amplitude modulation capability of the ion hydrogel layer.

[0066] In conjunction with the first aspect, in some embodiments provided in this application, the micropillar array layer 2 includes a plurality of micropillars, wherein: the cone angle of the micropillars is 30°~60°, which helps to induce the ion migration channels to be oriented along a predetermined path, expands the dynamic detection range of the sensor, and helps to adjust the stiffness gradient of the micropillars to achieve a balance between force transmission and response speed.

[0067] In conjunction with the first aspect, in some embodiments provided in this application, the micropillar array layer 2 includes a plurality of micropillars, wherein the ratio of the height to the diameter of the micropillars is 0.2 to 0.8, which is used to coordinately control the range of compression deformation and the structural resilience, so as to maintain structural stability while improving the deformability of the micropillars and enhancing the strain amplitude transmission efficiency.

[0068] In conjunction with the first aspect, in some embodiments provided in this application, the micropillar array layer 2 includes a plurality of micropillars, wherein: the height of the micropillars is 50~150 μm, which can achieve precise amplification of minute pressure disturbances to match the mechanical response window of biological skin.

[0069] It should be noted that in other embodiments, the cross-sectional shape of the micropillar structure can also be conical, stepped columnar, wavy, or a multi-level helical cavity structure, with a biomimetic helical-cavity combination structure being preferred to achieve superior multidimensional mechanical response performance. This multi-scale biomimetic structure can achieve controllable and reversible radial-axial composite deformation under small vertical loads; under larger pressure conditions, it exhibits layer-by-layer collapse extension response characteristics, thereby significantly amplifying the deformation of the flexible substrate and improving the stress-induced electrical signal amplitude of the flexible gel sensing layer. Overall, this design significantly improves the system's force-to-electrical conversion efficiency and detection sensitivity, effectively suppresses hysteresis effects and interface stress concentration, and significantly enhances the stability of the microstructure and the overall mechanical durability of the device.

[0070] In conjunction with the first aspect, in some embodiments provided in this application, the interdigitated electrode layer 31 includes multiple electrode units. The distribution density of these electrode units gradually increases along the pressure conduction direction perpendicular to the flexible substrate (i.e., from the micropillar array layer to the encapsulation layer), thereby forming an asymmetric electric field sensing region. This asymmetric arrangement strategy can significantly improve the sensitivity of electrical signal extraction at different depth strain levels, enhance the system's ability to distinguish minute pressure gradient changes, and achieve partitioned acquisition of multi-level pressure signals. Through the gradient distribution of the interdigitated electrode structure design, the spacing between adjacent electrodes gradually varies along the pressure loading direction, forming a resistance gradient amplification effect, thereby significantly enhancing the sensing ability and signal amplification effect of minute contact pressure changes, and improving the overall sensitivity and real-time response capability of the sensor. This design can effectively capture low-frequency minute pressure disturbances, meet the requirements of high-sensitivity detection, and significantly suppress background noise interference, optimizing the signal-to-noise ratio.

[0071] Asymmetric interdigitated electrodes refer to structures with non-equidistant spacing and different widths introduced in adjacent electrode pairs, forming a region with non-uniform electric field density. This can achieve local sensitivity enhancement, directional distribution control of the response domain, and noise shielding effect, further improving the sensor's detection capability and stability.

[0072] In conjunction with the first aspect, in some embodiments provided in this application, the electrode distribution density is 8~24 electrodes / cm². The spacing Δd between adjacent electrode units is 20~100μm. By controlling the electrode spacing Δd within this density range, the resistance gradient amplification effect along the pressure loading path can be achieved, while suppressing the electric field crosstalk effect, ensuring stable acquisition and reconstruction of multi-point distributed signals.

[0073] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0074] Example 1

[0075] A pressure detection system

[0076] A micropillar array was constructed on a flexible PDMS substrate using laser direct writing and mold replication technology. The cone angle was designed to be 45°, and the ratio of micropillar height to substrate diameter (h / D) was set to 0.5. The micropillar height was 100 μm, with 100 pillars / cm. 2 ;

[0077] Hydroxyethyl methacrylate and acrylate-zinc ion monomer (AA-Zn) were used. 2+ A flexible gel sensing layer was generated by copolymerization, with a molar coordination ratio of zinc ions to carboxyl ligands of 1:3. Ionic hydrogel microspheres synthesized by reverse emulsion polymerization of SBMA / polyaspartic acid were used as crosslinking agents for the ionic hydrogel microspheres, with an addition amount accounting for 0.05 wt% of the total mass of the reaction system. A gradient crosslinking structure was constructed by layer casting technology, with a gradient increasing distribution from the micropillar array layer to the encapsulation layer (the initial crosslinking density was set to 0.01 mol / cm³, and the terminal crosslinking density was set to 0.05 mol / cm³), and a total thickness of 0.5 mm. Among them, a 0.25 mm thick flexible gel sensing layer near the encapsulation layer contained 0.3% carbon nanotubes.

[0078] Asymmetric interdigitated electrodes were deposited on the surface of the flexible gel sensing layer using magnetron sputtering and photolithography, and the electrode spacing was controlled to form a 50 μm gradient in the pressure loading direction.

[0079] An encapsulation layer is prepared on the surface of a flexible gel sensing layer to obtain a pressure detection system.

[0080] Example 2

[0081] A pressure detection system

[0082] A micropillar array was constructed on a flexible PDMS substrate using laser direct writing and mold replication technology. The cone angle was designed to be 55°, and the ratio of micropillar height to substrate diameter (h / D) was set to 0.8. The micropillar height was 150 μm, and 40 micropillars / cm were used. 2 ;

[0083] Hydroxyethyl methacrylate and acrylamide-iron monomer (AM-Fe) were used. 3+ A flexible gel sensing layer was generated by copolymerization, with a molar coordination ratio of iron ions to carboxyl ligands of 1:6. Ionic hydrogel microspheres synthesized by reverse emulsion polymerization of DMAPS / sodium alginate were used as crosslinking agents for the ionic hydrogel microspheres, with an addition amount accounting for 0.08 wt% of the total mass of the reaction system. A gradient crosslinking structure was constructed by layer casting technology, with a gradient increasing distribution from the micropillar array layer to the encapsulation layer (the initial crosslinking density was set to 0.02 mol / cm³, and the terminal crosslinking density was set to 0.08 mol / cm³), and a total thickness of 0.5 mm. Among them, 0.3% carbon nanotubes were added to the 0.2 mm thick flexible gel sensing layer near the encapsulation layer.

[0084] Asymmetric interdigitated electrodes were deposited on the surface of the flexible gel sensing layer using magnetron sputtering and photolithography, and the electrode spacing was controlled to form a 20 μm gradient in the pressure loading direction.

[0085] An encapsulation layer is prepared on the surface of a flexible gel sensing layer to obtain a pressure detection system.

[0086] Example 3

[0087] A pressure detection system

[0088] A micropillar array was constructed on a flexible PDMS substrate using laser direct writing and mold replication technology. The cone angle was designed to be 50°, and the ratio of micropillar height to substrate diameter (h / D) was set to 0.2. The micropillar height was 50 μm, and 60 micropillars / cm were constructed. 2 ;

[0089] Using N,N-dimethylacrylamide and acrylate-calcium ion monomer (AA-Ca) 2+A flexible gel sensing layer was generated by copolymerization, with a molar coordination ratio of calcium ions to carboxyl ligands of 1:4. Ionic hydrogel microspheres synthesized by DMAPS / polylysine reverse emulsion polymerization were used as crosslinking agents for the ionic hydrogel microspheres, with an addition amount accounting for 0.05 wt% of the total mass of the reaction system. A gradient crosslinking structure was constructed by layer casting technology, with a gradient increasing distribution from the micropillar array layer to the encapsulation layer (the initial crosslinking density was set to 0.015 mol / cm³, and the terminal crosslinking density was set to 0.06 mol / cm³), and a total thickness of 0.5 mm. Among them, the flexible gel sensing layer with a thickness of 0.18 mm near the encapsulation layer contained 0.8% carbon nanotubes.

[0090] Asymmetric interdigitated electrodes were deposited on the surface of the flexible gel sensing layer using magnetron sputtering and photolithography, and the electrode spacing was controlled to form a 100 μm gradient in the pressure loading direction.

[0091] An encapsulation layer is prepared on the surface of a flexible gel sensing layer to obtain a pressure detection system.

[0092] Comparative Example 1

[0093] The difference from Example 1 is that the micropillar array on the surface of the flexible PDMS substrate is replaced with a micropillarless array.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that the flexible hydrogel sensing layer is replaced with a rigid dual-network hydrogel (the specific material is sodium poly(2-acrylamide-2-methylpropanesulfonate):polyacrylamide in a mass ratio of 1:12).

[0096] Performance testing

[0097] Within the static loading range of 0–50 kPa, the response time of the pressure detection systems in Examples 1 to 3 and Comparative Examples 1 to 2 was tested. The specific test method was as follows:

[0098] Response time is the time required for the sensor's output signal to change from its initial value to its steady-state value during external pressure loading or unloading.

[0099] The testing method is as follows:

[0100] Using an Instron 5943 or equivalent precision device, apply a certain pressure (e.g., 10 kPa) vertically to the sensor at a set speed (e.g., 10 mm / min), and simultaneously connect a high-resolution data acquisition module (e.g., Keithley DAQ6510) to record changes in electrical signals in real time.

[0101] Record the time (rise process) for the output voltage / resistance to reach the steady-state output value from the baseline value.

[0102] Record the time it takes for the electrical signal to recover to its initial state after the load is removed (recovery process);

[0103] The average value is used as the response time metric.

[0104] The experimental results are shown in Table 1:

[0105] Table 1 Performance of the pressure detection systems in Examples 1 to 3 and Comparative Examples 1 to 2

[0106]

[0107] As can be seen from Table 1, the response time of the embodiments is significantly better than that of the comparative examples. Based on the comparative examples, embodiments 1 to 3 of this application shorten the response time.

[0108] Comparative Example 1 lacks an effective mechanical signal amplification mechanism due to the absence of a micropillar array. The minute pressure changes sensed by the flexible substrate cannot be fully transmitted to the gel sensing layer, resulting in a significant decrease in the overall system's response sensitivity in the low-pressure range, an increase in the minimum detectable pressure threshold, and unstable strain transfer efficiency during pressure loading.

[0109] Comparative Example 2 replaced the flexible hydrogel sensing layer with a rigid dual-network hydrogel layer. Because the electrical signal of the rigid dual-network hydrogel layer does not change with the applied pressure, it has low sensitivity, an increased minimum detectable pressure threshold, and low resolution.

[0110] In summary, by utilizing the electrical signal of the flexible gel sensing layer, which changes with pressure, a highly sensitive response to minute pressure variations is achieved. This amplifies minute pressures and mitigates the hysteresis effect present in traditional silicone or metal films, significantly improving the overall response speed of the sensor. Simultaneously, the flexible gel sensing layer also provides a buffering effect, reducing signal drift and noise when pressure changes are significant, thus improving the accuracy of signal transmission.

[0111] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and 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, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0112] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0113] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A pressure detection system, characterized in that, Including the following settings in sequence: A flexible base layer is used to conform to the skin and sense minute changes in external pressure. The micropillar array layer, composed of multiple micropillar structures, is used to amplify and transmit pressure changes sensed by the flexible substrate layer; A flexible gel sensing layer is used to receive the pressure transmitted by the micropillar array layer and generate an electrical signal; as well as Encapsulation layer; The flexible gel sensing layer is provided with an interdigitated electrode layer. The electrical signal of the flexible gel sensing layer changes with the applied pressure, and the pressure electrical signal is detected through the interdigitated electrode layer. The flexible gel sensing layer comprises an ion-hydrogel microsphere crosslinking agent, a crosslinked gel matrix, and conductive ions. The ion-hydrogel microsphere crosslinking agent is polymerized from zwitterionic monomers and carboxyl polymer chains, and the crosslinked gel matrix is ​​composed of gel monomers and polymer chains. zwitterionic monomers include at least one of SBMA and DMAPS; and / or, Carboxyl-based polymer chains include at least one of polyaspartic acid and its derivatives, polylysine and its derivatives, alginate and its derivatives, and hyaluronic acid and its derivatives; and / or, The gel monomer includes at least one of acrylamide and its derivatives, acrylic acid and its derivatives, and N,N-dimethylacrylamide and its derivatives; and / or The polymer chain includes at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, and gelatin; and / or Conductive ions include Zn 2+ Fe 3+ Ca 2+ and Mg 2+ At least one of them; The crosslinking density of the flexible gel sensing layer increases in a gradient along the direction from the micropillar array layer to the encapsulation layer. The flexible gel sensing layer includes a first layer and a second layer, wherein the first layer is located between the flexible substrate layer and the second layer, and the material of the second layer is doped with carbon nanotubes. The thickness ratio of the first layer to the second layer is (1~3):1; The carbon nanotubes in the second layer account for 0.3% to 0.8% of the total mass. The micropillar array layer comprises multiple micropillars, and the micropillar structure is a multi-level biomimetic helical cavity structure, including an outer helical flow-guiding shell and an inner nested slow-release cavity, wherein: The spiral guiding shell has an asymmetric spin spiral shape along the axial direction and has radial-axial composite deformation capability. The slow-release cavity can collapse and deform step by step under external pressure to amplify the response signal; The interdigitated electrode layer is composed of multiple distributed electrode units, and its spatial distribution density increases in a gradient along the direction from the micropillar array layer to the encapsulation layer.

2. The pressure detection system as described in claim 1, characterized in that: The molar coordination ratio of the conductive ions to the carboxyl ligands in the cross-linked gel matrix is ​​1:(3~6).

3. The pressure detection system as described in claim 1, characterized in that: The cone angle of the micropillar is 30°~60°; and / or, The height-to-diameter ratio of the micropillar is 0.2 to 0.8; and / or, The height of the micropillars is 50~150 μm.

4. The pressure detection system as described in claim 1, characterized in that: The electrode distribution density is 8~24 electrodes / cm²; and / or, The spacing Δd between adjacent electrode units is 20~100μm.

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