A method of manufacturing a multi-functional stress sensor comprising a flexible substrate material and a sensor

Abstract

This invention discloses a method for fabricating a multifunctional stress sensor containing a flexible substrate material and the sensor itself. A multifunctional integrated material system is constructed through molecular design and composite technology. The method includes: mixing an elastomer matrix, a dynamic crosslinking agent, conductive nanomaterials, and biocompatible additives to prepare a composite solution; pouring the solution into a flat-bottomed container containing a thin sheet and solidifying it to form a grooved template containing the flexible substrate material; leading out electrodes and filling them with a composite conductive material; and coating the composite solution and solidifying it. The resulting sensor comprises an elastomer substrate, a composite conductive layer, and an electrode structure, possessing high tensile strength, high conductivity, self-healing capabilities, and biocompatibility. The process is simple and controllable, suitable for mass production, and can be widely applied in electronic, wearable devices, and biomedical monitoring fields containing flexible substrate materials.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, specifically to a method for fabricating a multifunctional stress sensor containing a flexible substrate and the sensor itself. Background Technology

[0002] Stress sensors incorporating flexible substrates have wide applications in wearable electronics, medical and health monitoring, and intelligent robotics. Traditional sensor fabrication methods using flexible substrates typically involve step-by-step assembly of single-functional materials, requiring multiple coating, curing, and patterning processes. This complex and costly process makes it difficult to meet the demands of mass production. Existing substrates in flexible materials often suffer from limited functionality, such as possessing only elasticity or conductivity. Material systems that simultaneously achieve high tensile strength, conductive stability, self-healing capabilities, and biocompatibility are still underdeveloped. Furthermore, traditional nanomaterial filling processes are prone to uneven dispersion and weak interfacial bonding, leading to sensor sensitivity degradation or structural failure. In biomedical applications, materials lacking biocompatibility may trigger rejection reactions, limiting their use in implantable devices. Therefore, developing a sensor fabrication technology incorporating flexible substrates that integrates multiple functional properties, has a simple process, and is suitable for large-scale production has become a critical issue that urgently needs to be addressed in this field. Summary of the Invention

[0003] To address the technical problems of existing sensors containing flexible substrate materials, such as complex fabrication processes, high costs, difficulty in mass production, limited material functionality and inability to simultaneously possess high tensile strength, conductivity, self-healing properties, and biocompatibility, as well as uneven nanomaterial dispersion, weak interfacial bonding, and insufficient biocompatibility, this application provides a method for fabricating a multifunctional stress sensor containing a flexible substrate material and the sensor itself.

[0004] In a first aspect, this application provides a method for fabricating a multifunctional stress sensor comprising a flexible substrate material, characterized by comprising the following steps:

[0005] S1: Take a flat-bottomed container and place a thin slice in the center of the container;

[0006] S2: Mix the elastomer matrix, dynamic crosslinking agent, conductive nanomaterial and biocompatible additive in a mass ratio of 8:1:0.5:0.5, stir at 500 r / min for 30 min and then vacuum filter for 10 min to prepare a multifunctional composite solution.

[0007] S3: Pour the composite solution into a flat-bottomed container to cover the sheet, cure at room temperature for 24 hours and / or heat at 60°C for 2 hours, peel off the sheet to obtain a template with grooves containing a flexible substrate material;

[0008] S4: Lead out electrodes from the opposite sides of the template groove containing flexible substrate material, and fill the groove with carbon nanotube-silver nanowire composite conductive material.

[0009] S5: A composite solution is coated on the surface of the filling material, and then cured after vacuum filtration for 5 minutes to obtain a stress sensor containing a flexible substrate material.

[0010] Furthermore, in the preparation of the multifunctional composite solution, an elastomer matrix, a dynamic crosslinking agent (an organic small molecule containing disulfide bonds / boron ester bonds / imine bonds), conductive nanomaterials, and biocompatible additives were added to a stirred tank at a mass ratio of 8:1:0.5:0.5 and mixed at 500 r / min for 30 min. A homogeneous system was formed through intermolecular dynamic chemical bonding. Subsequently, the mixture was vacuum filtered (-0.1 MPa) for 10 min to remove bubbles, thus obtaining a composite solution that combines elasticity, conductivity, self-healing groups, and biocompatible groups.

[0011] A thin, adjustable sheet with a thickness of 0.05–0.2 cm is placed in the center of a flat-bottomed container. A composite solution is poured in to cover the sheet, and curing is performed at room temperature (humidity ≤50%, 24h) or by heating (60℃, 2h). The sheet is then demolded to form a grooved template containing a flexible substrate material. The groove depth is precisely controlled by the sheet thickness. Symmetrical electrodes are drawn out along the opposite sides of the grooves by coating with silver paste or imprinting copper foil. The grooves are then filled with a carbon nanotube-silver nanowire composite conductive material (volume ratio 3:1–1:1), utilizing the viscosity of the composite solution to achieve material interlocking. A layer of composite solution is then coated for sealing, followed by vacuum filtration for 5 minutes and secondary curing to form an integrated structure of "substrate-conductive layer-protective layer".

[0012] In one embodiment, the sheet shape includes any one of rectangle, circle, triangle, square, pentagon, and hexagon, and the material is silicon wafer, glass sheet, plexiglass sheet, or plastic sheet.

[0013] In one embodiment, the flat-bottomed container is a 2cm×1cm rectangular and / or a 2cm diameter circular container with short walls, the size of which is adapted to the sheet.

[0014] In one embodiment, the nanoconductive material includes any one of carbon nanotubes, silver nanowires, gold nanoparticles, copper nanowires, graphene, or an oxide composite thereof.

[0015] In one embodiment, the electrodes are made of silver, copper, or ITO, are symmetrically distributed, and extend outward from the edge of the groove.

[0016] In one embodiment, the elastomer matrix is ​​any one of polyurethane, silicone rubber, and Ecoflex, and the dynamic crosslinking agent is an organic compound containing disulfide bonds, borate ester bonds, or imine bonds.

[0017] In a second aspect, the present invention also provides a stress sensor comprising a flexible substrate material prepared by any of the methods described herein, characterized in that it comprises a PDMS substrate, a nano-conductive material layer embedded in a groove of the substrate, and an electrode layer symmetrically disposed on both sides of the groove.

[0018] In one embodiment, the PDMS substrate has a thickness of 0.5 mm to 2 mm, a groove depth of 0.05 cm to 0.3 cm, and a width consistent with the width of the sheet.

[0019] In one embodiment, the nano-conductive material layer has a filling density of 80% to 100% and forms a composite structure by physical intercalation with the PDMS substrate.

[0020] In one embodiment, the electrode layer has a width of 0.1 cm to 0.5 cm, and the area of ​​the contact region with the nano-conductive material layer accounts for 60% of the surface area of ​​the electrode layer.

[0021] This invention significantly improves the overall performance and fabrication efficiency of stress sensors incorporating flexible substrate materials through the creation of multifunctional integrated materials and innovative integration processes. First, the composite solution system synergistically integrates an elastomer matrix, a dynamic crosslinking agent, conductive nanomaterials, and biocompatible additives. Through dynamic chemical bond design at the molecular level and the construction of a microscopic conductive network, the material simultaneously possesses high tensile strength, conductive stability, self-healing capabilities, and biocompatibility, overcoming the limitations of traditional materials with single functions. Second, the integrated fabrication process eliminates the need for complex step-by-step assembly. Multiple components can be integrated through a single mixing, molding, and filling process, simplifying template preparation, material filling, and structural fixation, reducing process complexity and production costs, and providing a feasible path for mass production. In terms of performance, the dynamic cross-linking network endows the material with self-healing properties, enabling it to restore structural integrity through chemical bond reconstruction after being damaged by external forces, thus improving the sensor's lifespan and reliability. The construction of a continuous conductive network ensures the material's conductivity stability under large deformations, solving the signal attenuation problem caused by tensile fracture in traditional nanomaterial-filled systems. The introduction of biocompatible additives makes the material suitable for human contact or implantation, broadening the application boundaries of the sensor in medical monitoring, wearable health devices, and other fields. Furthermore, the adjustability of process parameters allows for the flexible fabrication of sensors with different specifications and functional focuses by changing the sheet shape, material ratio, and curing conditions, meeting diverse application needs. Overall, this invention, through dual innovation in materials and processes, achieves a leap from single-function to multi-functional integration of sensors containing flexible substrate materials, possessing both technological advancement and industrial application potential. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the fabrication process of a multifunctional stress sensor containing a flexible substrate material, as provided in an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining this application and not for limiting it. It should also be noted that, for ease of description, only the parts relevant to this application are shown in the drawings, not all of them. Before discussing exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as being processed sequentially, many of these operations can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. A process can be terminated when its operation is completed, but it may also have additional steps not included in the drawings. A process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0024] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] Stress sensors incorporating flexible substrates have wide applications in wearable electronics, medical and health monitoring, and intelligent robotics. Traditional sensor fabrication methods using flexible substrates typically involve step-by-step assembly of single-functional materials, requiring multiple coating, curing, and patterning processes. This complex and costly process makes it difficult to meet the demands of mass production. Existing substrates in flexible materials often suffer from limited functionality, such as possessing only elasticity or conductivity. Material systems that simultaneously achieve high tensile strength, conductive stability, self-healing capabilities, and biocompatibility are still underdeveloped. Furthermore, traditional nanomaterial filling processes are prone to uneven dispersion and weak interfacial bonding, leading to sensor sensitivity degradation or structural failure. In biomedical applications, materials lacking biocompatibility may trigger rejection reactions, limiting their use in implantable devices. Therefore, developing a sensor fabrication technology incorporating flexible substrates that integrates multiple functional properties, has a simple process, and is suitable for large-scale production has become a critical issue that urgently needs to be addressed in this field.

[0026] Therefore, this invention discloses a method for preparing a multifunctional stress sensor containing a flexible substrate material and the sensor itself, constructing a multifunctional integrated material system through molecular design and composite technology. The method includes: mixing an elastomer matrix, a dynamic crosslinking agent, conductive nanomaterials, and biocompatible additives to prepare a composite solution; pouring the solution into a flat-bottomed container containing a thin sheet and solidifying it to form a grooved template containing the flexible substrate material; leading out electrodes and filling them with a composite conductive material; and coating the composite solution and solidifying it. The resulting sensor comprises an elastomer substrate, a composite conductive layer, and an electrode structure, possessing high tensile strength, high conductivity, self-healing capabilities, and biocompatibility. The process is simple and controllable, suitable for mass production, and can be widely applied in electronic, wearable devices, and biomedical monitoring fields containing flexible substrate materials.

[0027] This embodiment provides a detailed description of the fabrication method and the sensor itself for a multifunctional stress sensor containing a flexible substrate material, in order to achieve the technical solution described in the claims.

[0028] Example 1

[0029] This application provides a method for fabricating a multifunctional stress sensor comprising a flexible substrate material, characterized by comprising the following steps:

[0030] S1. Take a flat-bottomed container and place a thin slice in the center of the container;

[0031] S2. Mix the elastomer matrix, dynamic crosslinking agent, conductive nanomaterial and biocompatible additive in a mass ratio of 8:1:0.5:0.5, stir at 500 r / min for 30 min and then vacuum filter for 10 min to prepare a multifunctional composite solution.

[0032] S3. Pour the composite solution into a flat-bottomed container to cover the sheet, cure at room temperature for 24 hours and / or heat at 60°C for 2 hours, and peel off the sheet to obtain a template with grooves containing a flexible substrate material;

[0033] S4. Lead out electrodes from the opposite sides of the template groove containing the flexible substrate material, and fill the groove with carbon nanotube-silver nanowire composite conductive material.

[0034] S5. A composite solution is coated on the surface of the filling material, and then cured after vacuum filtration for 5 minutes to obtain a stress sensor containing a flexible substrate material.

[0035] S1 includes: The preparation process in this embodiment first requires preparing the materials and equipment needed for the experiment. A flat-bottomed container of suitable size is selected, such as a rectangular container of 2cm × 1cm or a circular container with a diameter of 2cm and low walls, to ensure the uniformity of subsequent film formation. A thin sheet is placed in the center of the container. The sheet material can be silicon, glass, plexiglass, or plastic, and its shape can be rectangular, circular, triangular, square, pentagonal, or hexagonal, depending on the groove structure required by the sensor. The size of the sheet should match the container to ensure that the composite solution can uniformly cover its surface.

[0036] An elastomer matrix (such as polyurethane, silicone rubber, or Ecoflex), a dynamic crosslinking agent (an organic compound containing disulfide bonds, borate ester bonds, or imine bonds), conductive nanomaterials (carbon nanotubes, silver nanowires, gold nanoparticles, copper nanowires, or graphene, etc.), and a biocompatible additive are mixed in a mass ratio of 8:1:0.5:0.5. The elastomer matrix provides support for the flexible substrate material, the dynamic crosslinking agent imparts self-healing capabilities to the material, the conductive nanomaterials construct a conductive network, and the biocompatible additive ensures the safety of the sensor in biomedical applications.

[0037] The mixing process was carried out at a stirring speed of 500 r / min for 30 minutes to ensure that the components were fully and uniformly dispersed. Subsequently, the mixture was vacuum filtered for 10 minutes to remove air bubbles and improve the homogeneity of the solution, finally obtaining a multifunctional composite solution that can be used for film formation.

[0038] Slowly pour the prepared composite solution into a flat-bottomed container, ensuring the solution completely covers the surface of the sheet and avoiding air bubbles or uneven thickness. Then, place the container at room temperature for 24 hours to cure, or accelerate curing by heating at 60°C for 2 hours. After curing, gently peel off the sheet, revealing a groove structure on the substrate containing the flexible base material, conforming to the shape of the sheet. The groove has a depth of 0.05cm to 0.3cm and a width consistent with the sheet size, providing precise spatial positioning for subsequent filling of the conductive material.

[0039] Carbon nanotube-silver nanowire composite conductive material is filled into the grooves of a template containing a flexible substrate, ensuring a filling density of 80%–100% to guarantee the sensor's conductivity. Filling methods can include drop-coating, blade coating, or micro-injection techniques to ensure uniform distribution and tight bonding of the conductive material to the substrate. After filling, electrodes are led out from opposite sides of the grooves. Electrode materials can be silver, copper, or ITO (indium tin oxide), and they are distributed symmetrically to ensure stable signal acquisition. The electrode width is controlled between 0.1 cm and 0.5 cm, and the contact area with the conductive material must account for more than 60% of the electrode surface area to reduce contact resistance.

[0040] After filling with conductive material, to protect the conductive layer and enhance the mechanical stability of the sensor, a composite solution is coated on the surface of the conductive layer, and then vacuum filtered again for 5 minutes to remove air bubbles. Subsequently, a second curing process is performed to form an integrated structure of the entire sensor containing a flexible substrate material. The final stress sensor containing the flexible substrate material consists of a PDMS substrate, a layer of nano-conductive material with embedded grooves, and symmetrically distributed electrode layers. The substrate thickness is 0.5 mm to 2 mm, exhibiting good tensile strength and environmental adaptability.

[0041] Secondly, the present invention also provides a stress sensor comprising a flexible substrate material prepared by any of the methods described herein, characterized in that it comprises a PDMS substrate, a nano-conductive material layer embedded in a groove in the substrate, and electrode layers symmetrically disposed on both sides of the groove. The PDMS substrate has a thickness of 0.5 mm to 2 mm, a groove depth of 0.05 cm to 0.3 cm, and a width consistent with the width of the sheet. The nano-conductive material layer has a filling density of 80% to 100% and forms a composite structure with the PDMS substrate through physical interlocking. The electrode layer has a width of 0.1 cm to 0.5 cm, and the contact area with the nano-conductive material layer accounts for 60% of the surface area of ​​the electrode layer.

[0042] PDMS substrates serve as the mechanical support and functional carrier for sensors, and their performance has been significantly improved through chemical modification and structural design. The -Si-O- backbone of the PDMS molecular chain endows the material with the intrinsic properties of a flexible substrate, while the introduction of dynamic crosslinking agents (such as small molecules containing disulfide bonds) can form a reversible covalent bond network between the molecular chains. When the substrate is fractured by external force, the dynamic bonds break and absorb energy. After the external force is removed, the bonding sites re-recognize and crosslink, achieving self-repair function. Experiments show that PDMS substrates containing 5% disulfide crosslinking agent achieve a tensile strength recovery rate of 92% and a conductive pathway repair efficiency of 95% within 24 hours after cutting damage. Improved biocompatibility is achieved through surface molecular engineering: polyethylene glycol (PEG) is grafted onto the PDMS molecular chain via hydrosilylation reaction to form a hydrophilic interface. Contact angle measurements show that the contact angle of the modified PDMS surface decreased from 110° to 55°, significantly improving cell adhesion. In co-culture experiments with L929 fibroblasts, the cell survival rate on the modified substrate surface reached 98%, superior to the 85% of untreated PDMS, meeting medical-grade material standards. Precise control of substrate thickness and groove structure relies on mold engineering. By changing the thickness of the central sheet (0.05-0.3cm), the groove depth can be precisely controlled. For example, a 0.05cm thick silicon wafer mold can form a shallow groove with a depth of 0.05cm, suitable for low-strain monitoring (such as pulse fluctuations); a 0.3cm thick glass sheet forms a deep groove, suitable for large deformation scenarios (such as joint movement). The overall substrate thickness (0.5-2mm) is controlled by the PDMS solution dosage. In industrial-grade coating equipment, the solution flow error can be controlled within ±1%, ensuring consistency in mass production.

[0043] The performance of the nano-conductive material layer is determined by its composition, microstructure, and interfacial interactions. When using a composite system of carbon nanotubes (CNTs) and silver nanowires (AgNWs), the two materials achieve synergistic performance through a "filler network interpenetration" mechanism: the high aspect ratio (>1000) of carbon nanotubes forms a mechanical framework, while silver nanowires fill the gaps and construct highly efficient conductive pathways. When the volume ratio of CNTs to AgNWs is 2:1, the resistivity change rate of the conductive layer at 100% stretching is only 4.2%, significantly better than the 12.5% ​​of the single CNT system. Innovation in the filling process is key to achieving high uniformity. Using vacuum-assisted filling technology (-0.08 MPa pressure), the conductive slurry is injected into the grooves at a constant flow rate of 0.1 mL / min, utilizing the capillary effect to eliminate air bubbles and achieve close packing. Experimental results show that this process can achieve a filling density of 98%, a 20% improvement over traditional gravity filling. In terms of interface bonding, 3-aminopropyltriethoxysilane (APTES) was used to aminate the CNT surface, so that it formed covalent bonds with the -SiOH group of PDMS. The interfacial shear strength was increased from 3MPa in traditional physical intercalation to 12MPa, effectively suppressing interfacial peeling under large deformation.

[0044] The microstructure of the conductive layer was characterized using scanning electron microscopy (SEM). At 5000x magnification, a three-dimensional network structure formed by CNTs and AgNWs was visible, with a node spacing of approximately 200 nm. This structure allows the conductive layer to maintain conductivity through network deformation rather than breakage during stretching. Finite element simulations showed that the structure maintained 85% of the conductive pathway integrity even under 500% strain, providing a structural basis for high sensitivity.

[0045] The electrode layer design needs to balance conductivity, the inclusion of flexible substrate materials, and process compatibility. Silver paste is preferred as the electrode material, with its nano-silver particles (particle size <50nm) forming a percolation network in an organic carrier, achieving a sheet resistance as low as 0.8Ω / □ and withstanding 300% tensile deformation. The optimization of electrode width (0.1-0.5cm) and contact area was achieved using response surface methodology: when the width is 0.2cm and the contact area occupies 65% of the electrode surface area, the contact resistance stabilizes at 7-9Ω, and the signal-to-noise ratio reaches 45dB, a 15% improvement over traditional designs. The symmetrically distributed electrode structure is ensured by precise mold positioning; on automated production lines, the electrode spacing error can be controlled within ±50μm. For scenarios requiring wireless transmission, a helical copper antenna is deposited on the conductive layer surface using magnetron sputtering. The antenna thickness is 2μm, with a resonant frequency of 2.4GHz, enabling stable signal transmission within a 10cm distance, suitable for wireless power supply and data transmission in implantable sensors.

[0046] The interfacial bonding between the electrode and the conductive layer employs dynamic covalent bonds. A crosslinking agent containing borate ester bonds is added to the silver paste, enabling it to form reversible bonds with the hydroxyl groups on the CNT surface. This bonding method not only improves contact stability but also endows the electrode with self-healing capabilities—when the electrode breaks due to tensile stress, the borate ester bonds can be repositioned, and the contact resistance recovers to 93% of its initial value within 24 hours.

[0047] The sensor is manufactured using a fully automated production line, with core processes including:

[0048] Solution preparation unit: A loss-in-weight metering system precisely controls the feeding ratio of PDMS main agent, curing agent, and dynamic crosslinking agent (error ±0.5%). A high-shear disperser (10000 r / min) ensures that the nanomaterials achieve nanoscale dispersion (particle size <100 nm) within 30 minutes. Template forming unit: A precision coating machine uniformly coats the composite solution onto the mold. Gradient curing (40℃→60℃→80℃) is achieved through a temperature-controlled tunnel oven, reducing the total curing time to 1.5 hours, improving efficiency by 40% compared to traditional processes. Conductive filling unit: A five-axis linkage micro-injection system achieves precise filling of the slurry within the grooves. A visual inspection system identifies filling defects online, with a rejection rate <0.3%. Encapsulation and curing unit: Utilizing ultraviolet curing technology (365 nm, 1000 mW / cm²).2 The curing time of the sealing layer is shortened from 1 hour for traditional heat curing to 5 minutes, making it suitable for heat-sensitive material systems.

[0049] Through the above embodiments, the resulting stress sensor incorporating a flexible substrate material has the following characteristics: its nano-conductive material layer has a filling density of 80% to 100%, forming a stable composite structure through physical interlocking with the substrate; the contact area between the electrode layer and the conductive material layer is large, ensuring accurate signal transmission; simultaneously, the sensor can sensitively respond to minute stress changes applied externally, making it suitable for a wide range of applications, such as electronic devices, health monitoring, and smart wearables incorporating flexible substrate materials. This stress sensor incorporating a flexible substrate material exhibits excellent conductivity and scalability, and can be improved and adjusted according to different application requirements to meet various high-precision stress monitoring needs.

[0050] This invention significantly improves the overall performance and fabrication efficiency of stress sensors incorporating flexible substrate materials through the creation of multifunctional integrated materials and innovative integration processes. First, the composite solution system synergistically integrates an elastomer matrix, a dynamic crosslinking agent, conductive nanomaterials, and biocompatible additives. Through dynamic chemical bond design at the molecular level and the construction of a microscopic conductive network, the material simultaneously possesses high tensile strength, conductive stability, self-healing capabilities, and biocompatibility, overcoming the limitations of traditional materials with single functions. Second, the integrated fabrication process eliminates the need for complex step-by-step assembly. Multiple components can be integrated through a single mixing, molding, and filling process, simplifying template preparation, material filling, and structural fixation, reducing process complexity and production costs, and providing a feasible path for mass production. In terms of performance, the dynamic cross-linking network endows the material with self-healing properties, enabling it to restore structural integrity through chemical bond reconstruction after being damaged by external forces, thus improving the sensor's lifespan and reliability. The construction of a continuous conductive network ensures the material's conductivity stability under large deformations, solving the signal attenuation problem caused by tensile fracture in traditional nanomaterial-filled systems. The introduction of biocompatible additives makes the material suitable for human contact or implantation, broadening the application boundaries of the sensor in medical monitoring, wearable health devices, and other fields. Furthermore, the adjustability of process parameters allows for the flexible fabrication of sensors with different specifications and functional focuses by changing the sheet shape, material ratio, and curing conditions, meeting diverse application needs. Overall, this invention, through dual innovation in materials and processes, achieves a leap from single-function to multi-functional integration of sensors containing flexible substrate materials, possessing both technological advancement and industrial application potential.

[0051] The above description is merely a preferred embodiment and the technical principles employed in this application. This application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions that can be made by those skilled in the art will not depart from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application. The scope of this application is determined by the scope of the claims.

Claims

1. A method of making a multi-functional stress sensor comprising a flexible base material, characterized by, Includes the following steps: S1: Take a flat-bottomed container and place a thin slice in the center of the container; S2: The elastomer matrix, dynamic crosslinking agent, conductive nanomaterial, and biocompatible additive are mixed in a mass ratio of 8:1:0.5:0.5, stirred at 500 r / min for 30 min, and then vacuum filtered for 10 min to prepare a multifunctional composite solution; wherein the dynamic crosslinking agent is a small molecule containing disulfide bonds, which can form a reversible covalent bond network between molecular chains. S3: Pour the composite solution into a flat-bottomed container to cover the sheet, cure at room temperature for 24 hours and / or heat at 60°C for 2 hours, peel off the sheet to obtain a template with grooves containing a flexible substrate material; S4: Electrodes are led out from the opposite side of the template groove containing the flexible substrate material, and carbon nanotube-silver nanowire composite conductive material is filled into the groove; wherein, 3-aminopropyltriethoxysilane is used to amide the surface of carbon nanotubes to form covalent bonds with the -SiOH groups of PDMS to improve the interfacial shear strength and suppress interfacial peeling under deformation. S5: A composite solution is coated on the surface of the filling material, vacuum filtered for 5 minutes, and then cured to obtain a stress sensor containing a flexible substrate material; wherein, the stress sensor includes a PDMS substrate, a nano-conductive material layer embedded in the substrate groove, and electrode layers symmetrically arranged on both sides of the groove; the PDMS substrate has a thickness of 0.5mm~2mm, a groove depth of 0.05cm~0.3cm, and a width consistent with the width of the sheet; the nano-conductive material layer has a filling density of 80%~100%, and forms a composite structure with the PDMS substrate through physical interlocking; the electrode layer has a width of 0.1cm~0.5cm, and the contact area with the nano-conductive material layer accounts for 60% of the surface area of ​​the electrode layer.

2. The method for fabricating a multifunctional stress sensor comprising a flexible substrate material according to claim 1, characterized in that, The sheet shape includes any one of rectangle, circle, triangle, square, pentagon, and hexagon, and the material is silicon wafer, glass sheet, plexiglass sheet, or plastic sheet.

3. The method for fabricating a multifunctional stress sensor comprising a flexible substrate material according to claim 1, characterized in that, The flat-bottomed container is a 2cm×1cm rectangular container and / or a 2cm diameter circular container with short walls, the size of which is adapted to the sheet.

4. The method for fabricating a multifunctional stress sensor comprising a flexible substrate material according to claim 1, characterized in that, The nanoconductive materials include any one of carbon nanotubes, silver nanowires, gold nanoparticles, copper nanowires, graphene, or their oxide composites.

5. The method for fabricating a multifunctional stress sensor comprising a flexible substrate material according to claim 1, characterized in that, The electrodes are made of silver, copper or ITO material, are symmetrically distributed and extend outward from the edge of the groove.

6. The method for fabricating a multifunctional stress sensor comprising a flexible substrate material according to claim 1, characterized in that, The elastomer matrix is ​​any one of polyurethane, silicone rubber, and Ecoflex, and the dynamic crosslinking agent is an organic compound containing disulfide bonds, borate ester bonds, or imine bonds.

7. A stress sensor, characterized in that, The stress sensor is prepared using the method described in any one of claims 1-6.

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