Flexible piezoresistive sensor with structurally tunable matching layer and applications thereof

Abstract

The application discloses a flexible piezoresistive sensor with a structure-adjustable matching layer and application thereof. The flexible piezoresistive sensor comprises a packaging layer and a sensing layer; the sensing layer comprises a sensitive layer and a matching layer; the matching layer is constructed into a preset micro-pattern support network through a programmable electrostatic direct writing printing process. A gradient distribution of a conductive filler content gradually decreases from the sensitive layer to the matching layer in a thickness direction of the sensing layer. Through the geometric microstructure design of the matching layer and the material gradient distribution, the mechanical response and sensitivity of the sensor are significantly improved. The matching layer effectively guides stress redistribution on a microscale, avoids stress concentration, and improves the stress uniformity of the sensitive layer, so that balanced and efficient response of the piezoresistive signal is realized. By adjusting the structure morphology and thickness of the matching layer, the balance between the rigidity and the sensitivity of the sensor can be precisely adjusted without changing the material composition of the sensitive layer, and the mechanical strength and long-term stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of intelligent sensor technology, and relates to a flexible piezoresistive sensor with an adjustable matching layer and its application. In particular, it relates to a flexible piezoresistive sensor with a sensing layer consisting of a sensitive layer and a matching layer, which can effectively change the mechanical properties by changing the structure of the matching layer and adjust the sensor sensitivity by adjusting the thickness of the matching layer and the sensitive layer. Background Technology

[0002] In recent years, with the rapid development of smart healthcare and wearable technology, flexible pressure sensors, as a key component of flexible electronic products, have shown broad application prospects in health monitoring, smart wearables, motion behavior recognition, and human-computer interaction. Especially in personalized medicine, elderly health management, and rehabilitation assistance, flexible pressure sensors have become an important functional module of such terminal devices due to their excellent flexibility, lightweight nature, and high fit. However, facing complex and diverse application requirements, existing flexible pressure sensors face significant technical bottlenecks in sensitivity control, mechanical performance management, and structural construction, particularly in material system construction, structural parameter optimization, and manufacturing process integration.

[0003] Currently, research on improving the performance of flexible pressure sensors mainly focuses on three directions: material formulation optimization, structural design innovation, and processing technology upgrades. Firstly, the rational design of material formulations is fundamental to achieving high-performance sensing. Carbon-based conductive materials (such as graphene and carbon nanotubes) and polymer materials are widely used due to their excellent conductivity, flexibility, and film-forming properties. However, how to precisely control the proportions of each component and their synergistic effects to balance conductivity, flexibility, and environmental stability remains a core challenge in current research. Secondly, device structure design has a decisive impact on sensor performance. Constructing multi-layered composite structures, such as sensitive layers and matching layers, can effectively regulate stress transmission paths and interface response behavior, thereby significantly improving sensing sensitivity and mechanical adaptability. The patterned structure of the matching layer (such as meshes, rings, fiber walls, etc.) and its number of layers can achieve directional response adjustment under different load conditions. Thirdly, in terms of manufacturing technology, traditional processes such as solution casting, spin coating, or vapor deposition have many limitations in microstructure construction and large-area consistency. In comparison, 3D printing technology, especially direct-write printing and electrostatic direct-write printing, has become an effective means of manufacturing flexible sensors due to its advantages such as precise pattern control, programmable process parameters, and customizable structures.

[0004] Against this backdrop, this invention proposes a flexible piezoresistive sensor with an adjustable matching layer. Utilizing an innovative material formulation scheme, an adjustable structural design, and a 3D printing manufacturing strategy compatible with various flexible materials, a multi-scale composite structure composed of a sensitive layer and a matching layer is constructed. By adjusting the number, thickness, and microstructure morphology of the sensitive and matching layers, comprehensive control over the sensor's sensitivity and mechanical properties can be effectively achieved. This solution features simple manufacturing process, flexible structure, and strong material versatility, making it suitable for various wearable health monitoring and human-machine interface applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flexible piezoresistive sensor with an adjustable matching layer and its applications. Through the unique geometric microstructure design and material gradient distribution of the matching layer, the mechanical response and sensitivity of the sensor are significantly improved. The matching layer effectively guides stress redistribution at the microscale, avoiding stress concentration and improving the uniformity of stress on the sensitive layer, thereby achieving a balanced and efficient response to the piezoresistive signal. By adjusting the structural morphology and thickness of the matching layer, the stiffness and sensitivity balance of the sensor can be precisely adjusted without changing the material composition of the sensitive layer, improving mechanical strength and long-term stability. This design overcomes the performance trade-off between sensitivity and structural strength in traditional sensors, offering advantages such as simple manufacturing process, high controllability, high repeatability, and low cost, making it widely applicable in flexible electronics fields such as electronic skin, intelligent rehabilitation, and human-computer interaction.

[0006] The present invention is implemented as follows: In a first aspect, the present invention provides a flexible piezoresistive sensor with a structurally adjustable matching layer, comprising an encapsulation layer, a sensing layer, leads, and copper foil; wherein, the sensor encapsulation layer comprises a top encapsulation layer and a bottom encapsulation layer, the sensing layer comprises a sensitive layer and a matching layer; the sensitive layer comprises a sensitive layer matrix material and a conductive filler; the matching layer comprises a matching layer matrix material and a conductive filler;

[0007] The matching layer is constructed as a preset micro-pattern support network using a programmable electrostatic direct writing printing process; the micro-pattern support network is composed of regularly arranged fibrous scaffolds; the fibrous scaffolds are a three-dimensional multi-layer structure.

[0008] Preferably, the conductive filler content is formed in a gradient distribution along the thickness direction of the sensing layer, with the content gradually decreasing from the sensitive layer to the matching layer. More preferably, the conductive filler comprises a mixture of graphene (G) and polyaniline (PANI); the mass content of graphene (G) in the matching layer is less than 0.15%, and the mass content of polyaniline (PANI) is less than 0.15%.

[0009] Preferably, the micropatterned support network adopts at least one of a parallel fiber wall structure, a concentric ring structure, or a grid cross structure.

[0010] Preferably, the spacing between adjacent fibers in the micropatterned support network is greater than or equal to 200 μm.

[0011] Preferably, the fibrous scaffold has 10-30 layers, and each layer has a thickness of 5 μm.

[0012] Preferably, the sensor is prepared using the following method:

[0013] (1) Ink preparation:

[0014] At room temperature, graphene (G) and polyaniline (PANI) are dispersed in a solvent system, and then polyethylene oxide (PEO) is added to form a uniformly dispersed sensitive layer composite ink.

[0015] Using the same method, graphene (G) and polyaniline (PANI) were dispersed in an organic solvent, and then a matrix material was added to formulate a matching layer composite ink;

[0016] (2) Sensor layer printing:

[0017] A sensitive layer is prepared on a pretreated substrate using a programmable direct-write printing process with a sensitive layer composite ink. Then, a matching layer with a preset micro-pattern support network structure is formed on top of the sensitive layer using a matching layer composite ink through a programmable electrostatic direct-write technology.

[0018] (3) Sensing layer pretreatment and encapsulation layer ink preparation:

[0019] After the printed sensor layer is cut to the predetermined size, it is surface treated and ink for the encapsulation layer is pre-made.

[0020] (4) Printing of the bottom encapsulation layer:

[0021] The bottom encapsulation layer is printed using electrostatic direct writing technology with encapsulation layer ink, and then semi-cured in a vacuum oven or at room temperature.

[0022] (5) Printing and encapsulation of the top layer encapsulation:

[0023] The surface-treated sensing layer is adhered to the bottom encapsulation layer, so that the sensing layer and the bottom encapsulation layer are bonded. Then, the top encapsulation layer is printed on the upper surface of the matching layer using electrostatic direct writing technology using encapsulation layer ink, and cured in a vacuum oven or at room temperature to form a complete flexible piezoresistive sensor.

[0024] More preferably, in the sensitive layer, the matrix material of the sensitive layer is polyethylene oxide (PEO) with a mass concentration of 7.4 wt%, graphene (G) with a mass concentration of 0.5 wt%, and polyaniline (PANI) with a mass concentration of 1.6 wt%.

[0025] In the matching layer, the matrix material of the matching layer is polycaprolactone (PCL) with a mass concentration of 22-24 wt%, polyaniline (PANI) with a mass concentration of 0.01-0.15 wt%, and graphene (G) with a mass concentration of 0.01-0.15 wt%.

[0026] More preferably, the sensitive layer is constructed using a programmable direct-write printing process, with the following printing parameters: a fan is installed above the printing platform, the printing needle is 20 G, the solution flow rate is 0.5 - 2.5 ml / h, the working distance is 0.1 - 2 mm, and the platform moving speed is 10 - 90 mm / s;

[0027] The matching layer is printed using electrostatic direct writing technology. The printing parameters are as follows: no fan is installed above the printing platform, the extrusion rate is 0.1 - 0.4 ml / h, the working distance is 1.5 - 3.5 mm, the platform moving speed is 40 - 70 mm / s, and the working voltage is 1.9 - 2.5 kV.

[0028] Secondly, the present invention provides the application of the sensor in at least one of wearable devices, electronic skin, and human-computer interaction interfaces.

[0029] Combining the above technical solutions and the technologies used to solve the problems, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0030] The matching layer of this invention constructs a three-dimensional micropattern support network through programmable electrostatic direct writing, with a fiber spacing ≥200μm and 10-30 layers. The micropattern network forms a multi-level stress buffer structure through regularly arranged fiber supports, overcoming the contradiction of "high sensitivity - low mechanical strength" in traditional sensors.

[0031] The present invention forms a conductive filler gradient distribution in the thickness direction of the sensing layer, and the high filler concentration in the sensitive layer forms a continuous conductive network to ensure high piezoresistive response; the low filler concentration in the matching layer ensures mechanical properties and guarantees structural integrity, realizing the functional transition of "high sensitivity-high rigidity", and solving the defect that homogeneous materials cannot take into account both electrical and mechanical properties.

[0032] This invention provides a flexible piezoresistive sensing layer. Through in-depth research on the sensing performance of inks made from different printable polymer composite materials, the optimal polymer material for sensing performance under the same conductive filler ratio was discovered and determined. Furthermore, this invention explores in detail the influence of the content of each ink component on the printing effect, thereby establishing the optimal printing parameters. The influence of different structures on sensor performance was systematically studied, providing a detailed process technology route and design ideas for the development of controllable printable flexible pressure sensors, and optimizing the balance between printing process and sensor performance.

[0033] The sensing layer material of this invention does not require replacement; the mechanical properties and sensitivity of the sensor can be quickly customized by adjusting the structure and number of layers. Specifically, by changing the structure of the matching layer and the number of sensitive layers, the mechanical response performance of the sensor can be effectively controlled. Simultaneously, the sensitivity of the sensing layer can be adjusted by varying the thickness of the matching layer, further enhancing the sensor's adaptability. Furthermore, the flexible piezoresistive sensor with an adjustable matching layer prepared by this invention can quickly respond to external pressure signals, adapting to different application scenarios such as smart healthcare, wearable devices, and robotics.

[0034] The flexible piezoresistive sensor of this invention employs a fully printed fabrication process, where all materials (including encapsulation and sensing materials) are produced using printing technology. This manufacturing method significantly reduces material waste, lowers production costs, and allows for precise customization of the three-dimensional structure and sensing performance to meet specific needs. Furthermore, all materials used in the sensor are flexible, enabling excellent surface adaptability, making it particularly suitable for bonding to irregular surfaces and greatly facilitating sensor integration. While maintaining its flexibility, the sensor can preserve the natural deformation of the main structure without significant deformation constraints, exhibiting excellent integrability and making it particularly suitable for wearable devices and soft robotics. Attached Figure Description

[0035] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. 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 the 3D printing system with an additional fan assembly provided in an embodiment of the present invention.

[0037] Figure 2 yes Figure 1 A schematic diagram of the extrusion system with an additional fan assembly is shown, where (a) is a perspective view, (b) is a top view, (c) is a front view, (d) is a side view, and (e) is a cross-sectional view.

[0038] Figure 3 This is a flowchart of the flexible piezoresistive sensor fabrication method provided in the embodiments of the present invention.

[0039] Figure 4 This is a schematic diagram of the fabrication process of the flexible piezoresistive sensor provided in an embodiment of the present invention.

[0040] Figure 5 This is a top view of the matching layer structure, where (a) is M22, (b) is M32, (c) is M42, and (d) is M52.

[0041] Figure 6 This is a top view of the flexible piezoresistive sensing layer structure, where (a) is M1, (b) is M2, (c) is M3, (d) is M4, and (e) is M5.

[0042] Figure 7 (a)- Figure 7 (b) are surface morphology diagrams of the sensing layers in Examples 1 and 5, respectively.

[0043] Figure 8 The effect of the number of sensitive layers on the mechanical properties of the sensing layer is shown in (a) for stress-strain and (b) for fracture strain.

[0044] Figure 9 The effect of the matching layer structure on the mechanical properties of the sensing layer is shown in (a) for stress-strain and (b) for modulus.

[0045] Figure 10 The influence of the number of mesh structure layers on the mechanical properties of the flexible piezoresistive sensor is shown in (a) for pressures of 0-50 kPa and (b) for pressures of 0-7 kPa.

[0046] Figure 11 These are the results of muscle movement monitoring by a flexible piezoresistive sensor, where (a) is a rapid 45° twist of the sternocleidomastoid muscle, (b) is a slow 45° twist of the sternocleidomastoid muscle, (c) is bending the little finger, (d) is bending the four fingers, (e) is a lightly clenched fist and a forcefully clenched fist, and (f) is the forearm raised from the plane at different angles. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0048] This embodiment provides a flexible piezoresistive sensor with a structurally adjustable matching layer, including an encapsulation layer, a sensing layer, leads, and copper foil;

[0049] The encapsulation layer includes a top encapsulation layer and a bottom encapsulation layer;

[0050] The sensing layer comprises a sensitive layer and a matching layer; the sensitive layer comprises a sensitive layer matrix material and a conductive filler; the matching layer comprises a matching layer matrix material and a conductive filler.

[0051] In one embodiment, the conductive filler comprises a mixture of graphene (G) and polyaniline (PANI); the mass content of graphene (G) in the matching layer is less than 0.15%, and the mass content of polyaniline (PANI) is less than 0.15%.

[0052] The matching layer is constructed as a pre-defined micro-pattern support network using a programmable electrostatic direct-write printing process. This micro-pattern support network consists of regularly arranged fibrous supports. These fibrous supports are three-dimensional multilayer structures; the tightly stacked fiber walls between layers provide directional support and stress dispersion, forming a mechanical adjustment structure between the sensitive layer and the external load. On one hand, the three-dimensional patterned structure of this invention guides stress redistribution at the microscale, reducing stress concentration effects and making the sensitive layer more uniformly stressed, thereby achieving a balanced response of the piezoresistive network. On the other hand, by changing the structural morphology and thickness of the matching layer, precise adjustment of the overall stiffness and sensitivity of the device can be achieved without changing the composition of the sensitive layer. Especially when the number of matching layers is moderate, it can improve both sensitivity and significantly enhance the structural strength of the sensing layer, which is beneficial for the long-term stable operation of the device.

[0053] In one embodiment, a gradient distribution of conductive filler content is formed along the thickness direction of the sensing layer, with the content gradually decreasing from the sensitive layer to the matching layer. Regarding material distribution, the functional material content of the sensitive layer and the matching layer exhibits a gradient difference, clearly defining the functional division of different regions within the sensing layer. The sensitive layer uses flexible polymer PEO as a matrix, with a relatively high proportion of graphene (G) and polyaniline (PANI) conductive fillers uniformly dispersed internally, forming a continuous conductive network to generate a significant piezoresistive effect under external force. In contrast, the matching layer uses a polymer material with higher mechanical strength (such as PCL) as a matrix, containing a lower proportion of graphene and polyaniline (e.g., each with a mass fraction not exceeding 0.15%, and the total filler content is much lower than that of the sensitive layer), primarily constructing a supporting framework and supplementing it with a certain degree of conductivity. Thus, a gradient distribution of conductive filler content is formed along the thickness direction of the sensing layer, with the conductive component content gradually decreasing from the sensitive layer to the matching layer; in other words, the conductive component content of the sensitive layer is relatively high, while the conductive component content of the matching layer is relatively low. This gradient arrangement of material conductivity creates functional zones in the sensing layer, transitioning from a high-sensitivity region to a high-rigidity support region from bottom to top: the lower sensitive layer is highly sensitive to pressure changes, while the upper matching layer provides structural support and stress buffering. The two layers bond well at the interface, and if necessary, material compatibility allows some components to permeate and fuse in the interface region, further enhancing the gradient transition and interfacial bonding. This material distribution not only ensures that the sensitive and matching layers function optimally in their respective regions but also endows the sensor with gradual changes in mechanical and electrical properties along its thickness, improving the device's response linearity and stability under different stress levels.

[0054] In one embodiment, the micropatterned support network employs at least one of a parallel fiber wall structure, a concentric ring structure, or a grid cross structure. The matching layers with different geometries exhibit varying mechanical control effects: for example, parallel fiber walls provide directional support and stress dispersion, concentric ring structures create symmetrical support in the central region, and grid structures achieve uniform stress transmission in all directions due to the uniform distribution of longitudinal and transverse fibers.

[0055] In one embodiment, the spacing between adjacent fibers in the micropatterned support network is greater than or equal to 200 μm. The fibrous scaffold has 10-30 layers, each with a thickness of 5 μm. By selecting appropriate microstructure morphology and parameters (such as fiber diameter, spacing, and number of layers), a minimum fiber spacing of approximately 200 μm can be achieved, and the printing layer thickness accuracy can reach 5 μm.

[0056] This embodiment also provides a method for fabricating the sensor, specifically including:

[0057] (1) Ink preparation:

[0058] At room temperature, graphene (G) and polyaniline (PANI) are dispersed in a solvent system, and then a sensitive layer matrix material is added to form a uniformly dispersed sensitive layer composite ink.

[0059] In one embodiment, the sensitive layer matrix material is made of polyethylene oxide (PEO) with a mass concentration of 7.4 wt%; graphene (G) with a mass concentration of 0.5 wt%; and polyaniline (PANI) with a mass concentration of 1.6 wt%.

[0060] Using the same method, graphene (G) and polyaniline (PANI) were dispersed in an organic solvent, and then a matching layer matrix material was added to formulate a composite ink for matching layer printing.

[0061] In one embodiment, the matching layer matrix material is made of polymer materials such as polycaprolactone (PCL), polyvinylpyrrolidone (PVP), thermoplastic polyurethane (TPU), polylactic acid (PLA), and polyurethane (PU). The concentration can be adjusted to a printable concentration according to the different matching layer matrix materials. PCL is preferred, with a concentration of 22-24 wt%; polyaniline (PANI) mass concentration of 0.01-0.15 wt%; and graphene (G) mass concentration of 0.01-0.15 wt%.

[0062] In one embodiment, the solvent for the ink in the sensitive layer is a mixture of water and ethanol, with a volume ratio of 4:6, 5:5, or 3:7, preferably 3:7.

[0063] Specifically, the conductive fillers in the matching layer ink are G and PANI, both at a concentration of 0.01-0.15 wt%. The purity of G is >98%, and the conductivity and molecular weight of PANI are 7.5 S / cm and 5-6 W, respectively. Both G and PANI can be replaced with other conductive fillers, such as carbon-based conductive materials or metallic conductive nanoparticles.

[0064] The organic solvent of the ink in the matching layer is selected from one or more of glacial acetic acid, chloroform, dichloromethane or dimethylformamide, with the preferred solvent corresponding to the polymer material being selected.

[0065] (2) Sensor layer printing:

[0066] A sensitive layer is prepared on a pretreated substrate using a programmable direct-write printing process with a sensitive layer composite ink. Then, a matching layer with a preset micro-pattern support network structure is printed on top of the sensitive layer using programmable electrostatic direct-write technology. The printed sensing layer can also be dried in a desiccator for 0.5 hours.

[0067] In one embodiment, the sensitive layer is constructed using a programmable direct-write printing process, with the following printing parameters: a fan is installed above the printing platform, the printing needle is 20 G, the solution flow rate is 0.5 - 2.5 ml / h (preferably 2.0 - 2.5 ml / h), the working distance is 0.1 - 2 mm (preferably 0.1 - 0.5 mm), the platform moving speed is 10 - 90 mm / s (preferably 40 - 50 mm / s), and the number of layers is preferably 6 - 14.

[0068] In one embodiment, the matching layer is printed using electrostatic direct writing technology, with the following printing parameters: no fan is installed above the printing platform, the extrusion rate is 0.1 - 0.4 ml / h (preferably 0.2 - 0.3 ml / h), the working distance is 1.5 - 3.5 mm (preferably 2.5 - 3 mm), the platform moving speed is 40 - 70 mm / s, the working voltage is 1.9 - 2.5 kV, and the number of printing layers is preferably 10 - 40 layers.

[0069] The thicknesses of the sensitive layer and the matching layer can be adjusted by controlling the printing parameters, thereby regulating the mechanical properties and sensitivity of the sensor respectively. Different micropattern structures can be used to regulate the mechanical properties of the sensing layer. The thickness of the matching layer is precisely controlled by the number of printing layers, with a minimum resolution of 5 μm and a minimum spacing between adjacent fibers of the structure of 200 μm.

[0070] (3) Sensing layer pretreatment and encapsulation layer ink preparation:

[0071] After the printed sensor layer is cut to the predetermined size, it is surface treated and ink for the encapsulation layer is pre-made.

[0072] In one embodiment, the encapsulation layer material is selected from polydimethylsiloxane (PDMS) or Ecoflex, with PDMS being preferred. The encapsulation layer ink is prepared by mixing the matrix and curing agent of the encapsulation layer material in a specific ratio, stirring at room temperature for 10 minutes, and then removing air bubbles by vacuuming in a vacuum oven before use. The ratio of matrix to curing agent for Ecoflex or PDMS is 1:1 and 10:1, respectively.

[0073] In one embodiment, the surface treatment of the sensing layer includes attaching leads to both ends of the sensitive layer with conductive silver paste and drying for 10-30 minutes; subsequently, copper foil is used to cover both ends of the leads and the sensing film to enhance electrical contact stability.

[0074] (4) Printing of the bottom encapsulation layer:

[0075] The bottom encapsulation layer is printed using electrostatic direct writing technology with encapsulation layer ink, and then semi-cured in a vacuum oven or at room temperature.

[0076] In one embodiment, the bottom encapsulation layer is stacked layer by layer according to a programmed pattern using electrostatic direct writing technology. The printing parameters include: working distance of 3-5 mm, working voltage of 2.6-4.5 kV, extrusion rate of 2.0-4.0 ml / h, and platform moving speed of 40-70 mm / s. After printing 1-4 layers, the layers are placed at room temperature for 5 h for semi-curing or heated in a vacuum oven at 60-80℃ (preferably 60℃) for 20-40 min for semi-curing.

[0077] (5) Printing and encapsulation of the top layer encapsulation:

[0078] The surface-treated sensing layer is adhered to the bottom encapsulation layer, so that the sensing layer and the bottom encapsulation layer are bonded. Then, the top encapsulation layer is printed on the upper surface of the matching layer using electrostatic direct writing technology using encapsulation layer ink, and cured in a vacuum oven or at room temperature to form a complete flexible piezoresistive sensor.

[0079] In one embodiment, the top encapsulation layer printing and encapsulation steps are as follows: First, the pre-treated sensing layer in step (4) is adhered to the semi-cured bottom encapsulation layer with a certain viscosity in step (4); second, the top encapsulation layer is printed on the bottom encapsulation layer with the sensing layer adhered thereto. The printing parameters are: working distance of 3-5 mm, working voltage of 2.6-4.5 kV, extrusion rate of 2.0-4.0 ml / h, and platform moving speed of 40-70 mm / s; after printing 1-4 layers, the layers are placed at room temperature for more than 10 hours for curing or heated in a vacuum oven at 60-80℃ (preferably 60℃) for 2-5 hours for curing.

[0080] This embodiment provides a sensor that is adaptable to different application scenarios. Its sensitivity and mechanical properties can be customized and quickly prepared and adjusted according to application requirements.

[0081] Using the flexible piezoresistive sensor with an adjustable matching layer, the tensile modulus of its sensing layer is significantly increased compared to a sensing layer with only a sensing layer structure (without a matching layer). When the matching layer structure is a mesh, parallel fiber walls, or a concentric ring structure, the tensile modulus increases by 1.9, 2.1, and 2.7 times, respectively.

[0082] The flexible piezoresistive sensor with an adjustable matching layer prepared by the above method has a tensile modulus and fracture strain of the sensing layer that increase with the number of sensing layers. When the number of sensing layers is 6, 8 and 10, the tensile modulus of the sensing layer increases to 18.8, 70.6 and 70.0 MPa, respectively.

[0083] The aforementioned flexible piezoresistive sensor with an adjustable matching layer allows for sensitivity adjustment to adapt to different application scenarios, including as a component in wearable devices, smart medical devices, and human-computer interaction systems. The sensor's sensitivity can be adjusted based on the number of matching layers; increasing the number of matching layers from 0 to 10 increases the sensor's sensitivity by 24.4 times. In summary, through the unique geometric microstructure design of the matching layer and the gradient distribution of material content in the sensitive and matching layers, this invention effectively defines and enhances the originality of the flexible pressure sensor's technical solution. Compared to existing technologies that typically employ only a single structure or uniform material distribution in the sensing layer, this invention introduces an adjustable micropatterned matching layer structurally and forms a functional gradient from sensitive to supportive in the material. This design significantly improves the sensor's mechanical stability and structural adjustability while maintaining high sensitivity, avoiding the defects of stress concentration and performance trade-offs. This fully demonstrates the innovation and limitation of the invention's technical solution and helps enhance the uniqueness of the solution within the scope of patent protection.

[0084] To more clearly illustrate the technical problem to be solved, the technical solution, and the beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the technical solution of the present invention and are not intended to limit the scope of the invention.

[0085] This invention compares the sensitivity performance of sensing layers printed using various polymer-based conductive inks to screen out the most suitable polymer matrix material for flexible piezoresistive sensors at the same graphene-to-polyaniline ratio. Using 3D printing technology, a sensing layer with a composite structure of both a sensing layer and a matching layer is constructed and applied to a flexible piezoresistive sensor. By precisely controlling the material composition, printing parameters, and thin film structure design of the sensing and matching layers, accurate regulation of the sensor's sensitivity and mechanical properties is achieved. The following examples will demonstrate that the technical solution proposed in this invention can effectively fabricate flexible piezoresistive sensors with customizable performance to meet the needs of various application scenarios, such as wearable devices, smart healthcare, and human-computer interfaces.

[0086] The preliminary work in Example 1 mainly investigated the scalability of the sensitive layer ink formulation. For example... Figure 1 As shown, this invention fabricated a flexible pressure sensor 4 using a laboratory-made 3D printing device (including a syringe 1, a micro-injection pump 2, an extrusion system 3 with an accessory fan assembly, a receiving platform 4, and a high-voltage power supply 5). The printing inks for the sensitive layer used PEO, TPU, PCL, and PVP as polymer materials, and graphene and polyaniline as conductive functional materials. The proportions of conductive materials remained constant, and the polymer materials were all used at concentrations suitable for printing. The number of layers and the structure of the sensitive layer were also kept consistent. According to the experimental data in Table 1, except for the PEO-based sensitive membrane which exhibited significant pressure sensitivity, the other sensitive membranes based on TPU, PCL, and PVP did not show a pressure response when external force was applied, demonstrating the irreplaceable nature of PEO.

[0087] Furthermore, all embodiments of the present invention employ an extrusion system 3 with an additional fan assembly. Figure 2 (a) Figure 2 In the middle (e), including needle 11, fan assembly 12, fan mold 1201, and fan 1202, a sensitive layer is prepared; otherwise, the sensitivity of the prepared sensitive layer will be greatly reduced. The fan assembly is not used when preparing the encapsulation layer.

[0088] Table 1 Performance of Sensitive Layers Prepared Based on Different Polymer Substrates

[0089]

[0090] Example 1

[0091] Materials: PEO, PCL, G, PANI, and PDMS were purchased from Huagao Fine Chemical Co., Ltd., Sigma-Aldrich, Suzhou Carbon-rich Graphene Technology Co., Ltd., Kuer Technology Co., Ltd., and Dow Corning, respectively.

[0092] method:

[0093] like Figure 3 and Figure 4 As shown, this embodiment of the invention provides a method for fabricating a flexible pressure sensor 4, comprising the following steps:

[0094] S1 Ink Preparation: Inks for printing the sensitive layer 4101 and the matching layer 4102 were prepared separately. 3 ml of deionized water and 7 ml of ethanol were placed in a wide-mouth bottle. 0.05 g of glucose (G) and 0.15 g of poly(PANI) were weighed into the bottle, and the mixture was magnetically stirred for 4 h to ensure complete dispersion and suspension of G and PANI. 0.7 g of poly(ethylene glycol) was weighed and added to the suspension, and the mixture was magnetically stirred for 10 h at room temperature to obtain the sensitive layer printing ink. Separately, 10 ml of glacial acetic acid was placed in a wide-mouth bottle, and 0.0005 g of G and 0.0005 g of PANI were added. The mixture was magnetically stirred for 4 h to form a suspension. 0.3113 g of poly(poly(ethylene glycol)) PCL was weighed and added to the suspension, and the mixture was magnetically stirred at 50 °C for 4 h to form the matching layer printing ink.

[0095] S2 Sensing Layer Printing: Based on the ink obtained in step S1, the sensitive layer 4101 of the sensing layer 41 is first printed using direct writing printing technology (with an additional fan assembly). Then, a grid structure matching layer 4102 is electrostatically written (without a fan assembly) on the sensitive layer 4101. A gradient distribution of conductive filler content gradually decreases from the sensitive layer to the matching layer in the thickness direction of the sensing layer.

[0096] S3 Sensing Layer Pretreatment and Encapsulation Layer Ink Preparation: The sensing layer is cut into the target shape and the printing ink for the encapsulation layer 42 is prepared;

[0097] S4 Bottom Encapsulation Layer Printing: The bottom encapsulation layer 4201 is printed using electrostatic direct writing technology and the encapsulation layer ink prepared in step S3, and then semi-cured by heating it in a vacuum oven for a certain time.

[0098] S5 Top layer encapsulation printing and encapsulation: The pre-treated sensing layer 41 in step S3 is adhered to the bottom encapsulation layer 4201 prepared in step S4, and the top encapsulation layer 4202 is printed on it by electrostatic direct writing and cured in a vacuum oven.

[0099] In step S1, the conductive fillers in the sensitive layer ink are G and PANI, with concentrations of 0.5 wt% and 1.6 wt%, respectively; the solvent is a mixture of deionized water and ethanol in a volume ratio of 3:7; and the polymer material is PEO with a concentration of 7.4 wt%. The conductive fillers in the matching layer ink are G and PANI, each with a concentration of 0.15 wt%; the solvent is acetic acid; and the polymer material is PCL with a concentration of 24 wt%.

[0100] In step S2, the matching layer 4102 is printed onto the sensitive layer 4101 and dried in a desiccator for 30 min. The printing parameters for the sensitive layer 4101 are: solution flow rate 2.5 ml / h, working distance 0.1 mm, and platform movement speed 50 mm / s; the printing parameters for the matching layer 4102 are: flow rate 0.3 ml / h, voltage 2.1 kV, working distance 2 mm, and platform movement speed 60 mm / s. The area of ​​a minimum complete grid of the matching layer is 500 × 500 μm. 2 The number of matching layers is 10.

[0101] In step S3, the sensing layer is cut to 11 × 25 mm. 2 The substrate was shaped into a rectangle, and two equal-length leads 4103 were attached to both ends of the sensitive layer 5 mm apart using conductive silver paste. The entire assembly was then placed in a desiccator and dried for 10 minutes. After complete drying, the leads were wrapped with copper foil 4104. The encapsulation layer ink was PDMS, with a substrate-to-curing agent weight ratio of 10:1.

[0102] In step S4, a certain amount of PDMS liquid prepared in step S3 is drawn into syringe 1 and extruded through peristaltic pump 2 and tubing at a rate of 3.0 ml / h. The printing working distance is set to 3 mm, the working voltage to 2.6 kV, and the moving speed of receiving platform 4 to 50 mm / s. Subsequently, the printed two layers of PDMS are placed in a vacuum oven and semi-cured at 80°C for 20 min to prepare the bottom encapsulation layer 4201.

[0103] In step S5, the sensor layer 41 processed in S3 is adhered to the semi-cured bottom encapsulation layer 4201 in S4, and then a top encapsulation layer 4202 is printed on it. The number of printing layers is 3, and the printing parameters are: working distance 3 mm, working voltage 2.6 kV, and the moving speed of the receiving platform 4 is 50 mm / s. Finally, the printed sensor is placed in a vacuum oven and heated at 60°C for 2 hours, and then cooled to room temperature for 5 hours after removal.

[0104] Comparative Example 1

[0105] In step S2 of Example 1, the number of mesh structure matching layers is 20, and the other conditions remain unchanged.

[0106] Comparative Example 2

[0107] In step S2 of Example 1, the number of mesh structure matching layers is 30, and the other conditions remain unchanged.

[0108] Comparative Example 3

[0109] In step S2 of Example 1, the number of mesh structure matching layers is 40, and the other conditions remain unchanged.

[0110] Example 2

[0111] The mesh structure of the matching layer in step S2 ( Figure 5 (d)M52) was changed to a concentric ring structure. Figure 5 (c)M42), the rest of the steps remain the same.

[0112] Example 3

[0113] The mesh structure of the matching layer in step S2 ( Figure 5 The structure (d)M52) was changed to a hollow, parallel fiber wall structure. Figure 5 (b)M32), the remaining steps remain the same.

[0114] Example 4

[0115] The mesh structure of the matching layer in step S2 ( Figure 5 The (d)M52) structure was changed to a parallel fiber wall structure. Figure 5 (a)M22), the remaining steps remain the same.

[0116] Example 5

[0117] In step S2, no matching layer is set; only the sensitive layer is printed as the sensing layer. The rest of the steps remain unchanged.

[0118] Furthermore, the sensitive layers in Examples 1-5 were all prepared using steps S1 and S2 in Example 1. In Examples 1-4, matching layers with different structures were constructed on the sensitive layers, and schematic diagrams of the top views of the resulting sensing layer structures are shown below. Figure 6 (a) Figure 6 Middle (e).

[0119] Furthermore, in step S1 of Embodiment 1 of the present invention, PCL can be replaced with other printable polymers such as TPU, PVP, PU, ​​etc.; PANI can be replaced with other conductive polymers; and G can be replaced with other conductive (nano) materials such as flakes, wires, or particles.

[0120] Furthermore, the structure of the sensitive layer and the matching layer in step S2 provided in Embodiment 1 of the present invention can be customized as needed, and is not limited to grid, concentric ring, or parallel fiber wall structure. The structure and thickness can be arbitrarily customized as needed.

[0121] Furthermore, the printing parameters in steps S1, 2, 4, and 5 provided in Embodiment 1 of the present invention can be adjusted according to actual conditions.

[0122] Furthermore, in step S3 provided in Embodiment 1 of the present invention, the target shape and size of the sensing layer to be cut can be adjusted as needed.

[0123] Furthermore, the number of printing layers for the sensitive layer, matching layer, and encapsulation layer provided in Embodiment 1 of the present invention can all be adjusted according to requirements.

[0124] The sensors prepared in the above embodiments or comparative examples were subjected to performance testing and application research, and the results are as follows:

[0125] Surface morphology test

[0126] The surface morphology of the sensing layers prepared in Examples 1 and 5 was observed using field emission scanning electron microscopy. The surface morphology of the sensing layers is as follows: Figure 7 As shown in (a), its surface is rough and porous. The large image in the upper right corner shows the high-resolution microstructure of the sensitive layer. The rod-shaped structure in the image is PANI, and the multilayer structure is G. A matching layer with a 40-layer grid structure was printed on the sensitive layer. Figure 7 (b) shows the precise stacking of the grid structure, and the high-resolution image in the upper right corner shows that the surface of the matching layer is relatively smooth.

[0127] Mechanical performance testing

[0128] The mechanical properties of the sensors prepared in the above embodiments or comparative examples were tested using a universal testing machine. The upper and lower ends of the sensor were fixed using the instrument's built-in clamps, and the sensor was stretched at a rate of 5 mm / s until fracture. The stress-strain curves of the sensor were recorded. The results are as follows: Figure 8 (a) Figure 8 As shown in (b), the steeper the slope of the linear segment of the stress-strain curve, the higher the modulus, and vice versa. It can be seen that as the number of sensitive layers increases from 6 to 10 and then 14, the elongation at break and the modulus of the sensing layer gradually increase. The flexibility of the sensing layer decreases somewhat, but its resistance to deformation increases. Therefore, in device fabrication and applications in soft interfaces, the flexibility and deformation resistance of the sensing layer can be controlled by adjusting the number of sensitive layers.

[0129] The impact of the matching layer structure on the mechanical properties of the sensing layer is shown in Figure 9 (a) Figure 9(b) Sensing layers M2, M4, and M5, with a matching layer structure consisting of fiber wall M22, ring M42, and mesh M52, have moduli that are 2.1, 2.7, and 1.9 times that of sensing layer M1 without a matching layer, respectively. In contrast, the modulus of sensing layers with a hollow fiber wall matching layer is similar to that of sensing layers with only a sensing layer. Due to the uneven structural distribution, the hollow fiber wall structure causes stress concentration in a certain section of the membrane, making it more prone to fracture. Therefore, when designing the matching layer structure, a structure that can uniformly distribute stress should be fully considered.

[0130] Sensitivity test

[0131] Besides the matching layer structure, the number of matching layers also significantly impacts sensor performance. Therefore, this invention utilizes weights to apply static pressure and tests the response performance of the composite structure sensors in Example 1 and Comparative Examples 2-4 under different pressures, and analyzes the response curves. Figure 10 In section (a), the sensitivity of each sensor was obtained by linear fitting of the data from 0 to 5 kPa. The results are shown in [the table / image]. Figure 10 (b) In the figure, all dashed lines represent linear fitting curves for different sensors, and the slope (S1-S4) of the dashed lines represents the sensitivity of the corresponding sensor. Since the sensor with 40 matching layers has an R-value of 40, the R-value of its fitting curve is... 2 The value of approximately 0.7 indicates that the fit is not of reference value, therefore S5 is not marked in the figure. Sensitivity data shows that as the number of matched layers increases from 0 to 40, the sensor sensitivity exhibits a trend of first increasing and then decreasing. The highest value for S2 is 4.64 kPa. -1 (R) 2 = 0.901), and the sensitivities of S3 and S4 are 0.91 kPa respectively. -1 (R) 2 = 0.909), 0.16 kPa -1 (R) 2 = 0.916), the sensor with 40 matching layers has the worst sensitivity. When the number of matching layers is 10, the elasticity and strength of the sensor increase, and the deformation under the same external pressure also increases; however, when the number of matching layers is too large (≥ 30), the sensor's ability to resist deformation is too great, and when the same external force is applied, the deformation decreases with the increase of layer thickness, and the sensitivity is actually reduced compared to the device without matching layers. Therefore, for the flexible piezoresistive sensor with adjustable matching layers designed in this invention, if the need to improve sensitivity outweighs the need to enhance mechanical performance, the number of matching layers should not exceed 30.

[0132] Muscle movement monitoring

[0133] The application performance of the flexible piezoresistive sensor prepared according to this invention was investigated using human muscle movement detection. A flexible piezoresistive sensor (SMS) with 10 sensitive layers and 10 mesh structure matching layers was prepared using the preparation method described in Example 1 above. First, it was attached to the sternocleidomastoid muscle (SCM) at the neck, and the relative resistance change of the sensor SMS during head and neck twisting was measured using an electrochemical workstation. The head and neck were twisted to a certain position at a relatively uniform rate and a relatively fixed angle, and then the head and neck either did not remain in that position or remained there for a few seconds before returning to the initial position. This process was repeated several times. The test group where the head and neck did not remain at a twisting angle of approximately 45° was recorded as fast, and the resulting relative resistance change of the device was as follows: Figure 11 As shown in (a). The experimental group in which the head and neck were twisted to 45° and held in that position for several seconds was recorded as slow. The resulting change in the relative resistance of the device is shown in Figure (a). Figure 11 As shown in (b). Due to slight differences in the force and angle of head and neck twisting, whether the head and neck remain at a 45° position or not, Figure 11 (a) Figure 11 The results of the eight repeated experiments in (b) all showed that the relative resistance change of the sensor SMS was not completely consistent, which also indicates that the SMS has high sensitivity and can detect the force difference of SCM caused by different head and neck twisting angles. The difference is that when the head and neck are held at a 45° position and then returned to the initial position, the relative resistance change curve shows a "double peak" phenomenon. Figure 11 (b) The first peak is the stress response peak of the SCM. During the rotation of the head and neck to a 45° position, the instantaneous change in SCM force causes deformation of the SMS, increasing the spacing and potential barrier of the conductive material inside the sensing material and generating microcracks. A very small number of conductive pathways are established but are not dominant. Overall, the resistance of the device increases, thus generating the response peak. When the head and neck remain in this position, due to the stress relaxation characteristics of the polymer-based flexible pressure sensor, the stress decreases slightly over time, resulting in a decrease in the relative change in resistance. The instant the head and neck return to the initial position, the stress is suddenly unloaded, and a small portion of the newly established conductive pathways inside the sensing membrane material are quickly broken, causing the resistance to increase rapidly, thus resulting in the second peak (recovery peak). Due to the hysteresis characteristics of the polymer material, the recovery rate of the microcracks generated inside the polymer after the previous pressure is slower than the rate of breakage of the conductive pathways. Therefore, after the appearance of the second peak, the resistance gradually decreases with the recovery of the microcracks and returns to the initial value.

[0134] The SMS sensor was attached to the abductor digitorum minimi (ADM) muscle in the palm to monitor little finger movement, in order to explore the potential applications of the SMS sensor in prosthetics, human-machine interfaces, and other fields. The results are as follows: Figure 11As shown in (c), each time the little finger bends, the ADM contracts and its force increases, causing the sensor's resistance to increase; when the little finger returns to its original position, the AMD relaxes and its force decreases, thus restoring the sensor's SMS resistance to its initial value. The larger the little finger bend angle, the greater the force generated by the ADM, and the larger the peak value of the curve; the smaller the little finger bend angle, the smaller the force generated by the ADM, the smaller the sensor deformation, and the smaller the peak value of the curve.

[0135] Figure 11 The middle (d) panel shows the monitoring results of the SMS sensor on the flexion movements of the other four fingers. The SMS sensor was applied to the Jianshi acupoint (3 cun above the wrist crease), located between the flexor carpi radialis tendon and the palmaris longus tendon. The four fingers (excluding the thumb) were repeatedly flexed. The curves showing the change in relative resistance of the sensor over time reflect the movement state of the four fingers and the changes in muscle strength caused by flexion. A greater change in relative resistance indicates a greater degree of flexion of the four fingers, and a greater change in the strength of the flexor carpi radialis tendon and palmaris longus tendon caused by flexion.

[0136] The SMS sensor can also be used to monitor changes in muscle strength caused by clenching the fist, in order to comprehensively assess grip strength or finger movement. The SMS sensor is attached to the flexor carpi radialis (FCR) muscle to monitor the fluctuations in the FCR caused by natural and forceful clenching of the fist. Figure 11 As shown in (e), when the fist is lightly clenched, the smaller the gripping force, the smaller the fluctuation of the FCR and the less obvious the contraction, resulting in a smaller change in the relative resistance of the SMS. Conversely, when the fist is clenched forcefully, the greater the gripping force, the larger the fluctuation of the FCR and the tighter the contraction, leading to a greater change in the relative resistance of the SMS. When the fist is clenched, the contraction pressure of the FCR causes some conductive paths inside the sensor to break, creating tiny cracks, thus increasing the SMS resistance. When the finger is released, the FCR relaxes, the force applied to the SMS disappears, and the resistance returns to its initial value. A strong fist clench held for about 1 second also shows a "double peak" in the curve of relative resistance over time, the principle of which is similar to... Figure 11 The principle behind the formation of the "double peaks" in (b) is the same. Figure 11 The comparison of the two sets of curves in (e) shows that the SMS sensor can better identify the magnitude of grip force.

[0137] Contraction and relaxation of the biceps brachii can also cause changes in the sensor's resistance. By attaching the sensor (SMS) to the biceps brachii muscle of the upper arm, changes in biceps brachii strength can be monitored. The amplitude of biceps brachii contraction is controlled by the angle at which the forearm is raised from a plane; a smaller angle results in a smaller amplitude of biceps brachii contraction. The raised angles are 30°, 60°, and 90°. Monitoring results are as follows... Figure 11As shown in (f), when the forearm is raised to 30°, the change in relative resistance of the sensor is minimal (<7%); when the forearm is raised to 90°, the change in relative resistance increases to approximately 22.5%. In summary, within the range of forearm raising angle of 30-90°, the change in relative resistance increases with the increase in forearm raising angle or the amplitude of biceps contraction.

[0138] The above muscle movement detection is only to illustrate one of the potential applications of the flexible piezoresistive sensor proposed in this invention, and does not limit the application of the sensor proposed in this invention.

[0139] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A flexible piezoresistive sensor with a structurally adjustable matching layer, comprising an encapsulation layer, a sensing layer, leads, and copper foil; wherein, The sensor encapsulation layer includes a top encapsulation layer and a bottom encapsulation layer; the sensing layer includes a sensitive layer and a matching layer; the sensitive layer includes a sensitive layer matrix material and a conductive filler; the matching layer includes a matching layer matrix material and a conductive filler. The feature is that the matching layer is constructed into a preset micro-pattern support network through a programmable electrostatic direct writing printing process; the micro-pattern support network is composed of regularly arranged fibrous scaffolds; the fibrous scaffolds are a three-dimensional multi-layer structure; The sensor was prepared using the following method: (1) Ink preparation: At room temperature, graphene (G) and polyaniline (PANI) are dispersed in a solvent system, and then polyethylene oxide (PEO) is added to form a uniformly dispersed sensitive layer composite ink. Using the same method, graphene (G) and polyaniline (PANI) were dispersed in an organic solvent, and then a matrix material was added to formulate a matching layer composite ink; (2) Sensor layer printing: A sensitive layer is prepared on a pretreated substrate using a programmable direct-write printing process with a sensitive layer composite ink. Then, a matching layer with a preset micro-pattern support network structure is formed on top of the sensitive layer using a matching layer composite ink through a programmable electrostatic direct-write technology. (3) Sensing layer pretreatment and encapsulation layer ink preparation: After the printed sensor layer is cut to the predetermined size, it is surface treated and ink for the encapsulation layer is pre-made. (4) Printing of the bottom encapsulation layer: The bottom encapsulation layer is printed using electrostatic direct writing technology with encapsulation layer ink, and then semi-cured in a vacuum oven or at room temperature. (5) Printing and encapsulation of the top layer encapsulation: The surface-treated sensing layer is adhered to the bottom encapsulation layer, so that the sensing layer and the bottom encapsulation layer are bonded. Then, the top encapsulation layer is printed on the upper surface of the matching layer using electrostatic direct writing technology using encapsulation layer ink, and cured in a vacuum oven or at room temperature to form a complete flexible piezoresistive sensor.

2. The sensor according to claim 1, characterized in that, A gradient distribution of conductive filler content is formed in the thickness direction of the sensing layer, with the content gradually decreasing from the sensitive layer to the matching layer.

3. The sensor according to claim 2, characterized in that, The conductive filler comprises a mixture of graphene (G) and polyaniline (PANI); the mass content of graphene (G) in the matching layer is less than 0.15%, and the mass content of polyaniline (PANI) is less than 0.15%.

4. The sensor according to claim 1, characterized in that, The micro-patterned support network adopts at least one of the following: parallel fiber wall structure, concentric ring structure, or grid cross structure.

5. The sensor according to claim 1, characterized in that, The spacing between adjacent fibers in the micropatterned support network is greater than or equal to 200 μm.

6. The sensor according to claim 1, characterized in that, The fibrous scaffold has 10-30 layers, and each layer is 5 μm thick.

7. The sensor according to claim 1, characterized in that, In the sensitive layer, the matrix material is polyethylene oxide (PEO) with a mass concentration of 7.4 wt%, graphene (G) with a mass concentration of 0.5 wt%, and polyaniline (PANI) with a mass concentration of 1.6 wt%. In the matching layer, the matrix material of the matching layer is polycaprolactone (PCL) with a mass concentration of 22-24 wt%, polyaniline (PANI) with a mass concentration of 0.01-0.15 wt%, and graphene (G) with a mass concentration of 0.01-0.15 wt%.

8. The sensor according to claim 1, characterized in that, The sensitive layer is constructed using a programmable direct-write printing process, with the following printing parameters: a fan is installed above the printing platform, the printing needle is 20 G, the solution flow rate is 0.5-2.5 ml / h, the working distance is 0.1-2 mm, and the platform moving speed is 10-90 mm / s. The matching layer is printed using electrostatic direct writing technology. The printing parameters are as follows: no fan is installed above the printing platform, the extrusion rate is 0.1 - 0.4 ml / h, the working distance is 1.5 - 3.5 mm, the platform moving speed is 40 - 70 mm / s, and the working voltage is 1.9 - 2.5 kV.

9. The application of the sensor according to any one of claims 1-8 in at least one of wearable devices, electronic skin, and human-computer interaction interfaces.

Images