Wearable flexible sensor based on circumferential negative poisson's ratio structure and preparation method

Abstract

The application provides a wearable flexible sensor based on a circumferential negative Poisson's ratio structure and a preparation method, relates to the technical field of intelligent wearable devices, and the sensor comprises a signal module, a sensing module, a first wire and a second wire; the sensing module comprises a shell, a first electrode, a second electrode and a sensing unit; the sensing unit comprises a composite material body and a plurality of elastomer skeleton structures embedded in the composite material body in a uniform distribution; the elastomer skeleton structures comprise a plurality of circumferential negative Poisson's ratio structures; the circumferential negative Poisson's ratio structure comprises a first panel, a second panel, a first deformation rod, a second deformation rod, a third deformation rod and a fourth deformation rod; the first panel of each circumferential negative Poisson's ratio structure is located on the same plane and is connected to each other, and the second panel of each circumferential negative Poisson's ratio structure is located on the same plane and is connected to each other. The application improves the mechanical properties and material compression deformation characteristics of the flexible sensor, so that the sensor has a larger sensing range and higher measurement sensitivity.

Description

Technical Field

[0001] This invention relates to the field of smart wearable technology, and in particular to a wearable flexible sensor based on a circumferential negative Poisson's ratio structure and its fabrication method. Background Technology

[0002] Skin possesses characteristics such as tactile perception, high flexibility, stretchability, and healing ability. Flexible wearable devices based on skin perception can transmit a range of health information by adhering to the skin, showing broad development prospects in areas such as intelligent robots, wearable medical devices, and medical health monitoring. As early as the 1970s, the potential applications of tactile perception simulation were explored, and some encouraging tactile sensor effects were developed, but problems such as low resolution and poor performance remained.

[0003] As China gradually enters an aging society, the proportion of elderly people is increasing, and service facilities for the elderly population are being strengthened. Addressing issues such as decreased limb flexibility and cognitive impairment in the elderly, individuals with motor disorders often require personal guidance from medical personnel during rehabilitation training. This increases the financial burden and, to some extent, wastes medical resources. In this context, there is an urgent need to develop a simple and easy-to-use health monitoring device to provide a comprehensive standard and control over the rehabilitation training process. Furthermore, during high-level, high-intensity training for athletes, coaches need to have a rigorous grasp of the athletes' condition throughout the process, making a highly sensitive and high-performance wearable device essential.

[0004] Flexible wearable devices can adhere closely to the surface of human skin to transmit a range of important health information, such as wrist pulse, vocal cord vibration, knee flexion, and heart rate monitoring, to help patients maintain their health. Existing flexible wearable devices are all based on a Poisson's ratio structure; under stretching, they expand longitudinally and compress laterally. Therefore, the sensitivity caused by longitudinal stretching is offset by lateral Poisson compression, which inherently limits the sensitivity.

[0005] Mechanical metamaterials are a newly emerging branch in the field of metamaterials in recent years. They mainly achieve enhanced or unattainable mechanical properties, such as negative Poisson's ratio or negative compressibility, by carefully designing the internal geometry. Existing sensors based on negative Poisson's ratio structures are all based on stretching. High sensitivity can only be maintained within a certain range because the negative Poisson's ratio effect weakens or even disappears after the negative Poisson's ratio structural unit exceeds a certain degree of stretching, thus reducing sensitivity. They cannot achieve a sustained high sensitivity effect over a large stretching range and cannot meet the needs of applications with a large deformation range.

[0006] Furthermore, currently, a single flexible sensor still struggles to achieve, for example, full-area human body information monitoring and acquisition, and cannot adapt to the measurement requirements of different parts during full-area human body monitoring. There is a profound contradiction between the high sensitivity and high load-bearing requirements of flexible force sensors. Summary of the Invention

[0007] The purpose of this invention is to provide a wearable flexible sensor based on a negative Poisson's ratio structure and its fabrication method. By combining the circumferential negative Poisson's ratio structure with composite materials, the mechanical properties of the flexible sensor are improved, thereby enabling the sensor to have a larger sensing range and higher measurement sensitivity.

[0008] This invention provides a wearable flexible sensor based on a circumferential negative Poisson's ratio structure, including a signal module, a sensing module, a first wire, and a second wire;

[0009] The sensing module includes a housing, a first electrode, a second electrode, and a sensing unit; the sensing unit includes a composite material body and a plurality of elastomeric skeleton structures uniformly distributed within the composite material body; the elastomeric skeleton structure includes a plurality of circumferential negative Poisson's ratio structures.

[0010] The circumferential negative Poisson's ratio structure includes a first panel, a second panel, a first deformable rod, a second deformable rod, a third deformable rod, and a fourth deformable rod; the first panels of each of the circumferential negative Poisson's ratio structures are located on the same plane and are connected to each other, and the second panels of each of the circumferential negative Poisson's ratio structures are located on the same plane and are connected to each other;

[0011] The first panel and the second panel are the same size and shape, and the first panel and the second panel are parallel; the line connecting the center point of the first panel and the center point of the second panel is perpendicular to the first panel.

[0012] Both the first panel and the second panel are hollow squares; the surface of the first panel facing the second panel is defined as the first connecting surface, and the surface of the second panel facing the first panel is defined as the second connecting surface.

[0013] The first deformable rod, the second deformable rod, the third deformable rod, and the fourth deformable rod are the same size and are all V-shaped;

[0014] The first end of the first deformable rod is connected to the first apex corner of the first connecting surface, and the second end of the first deformable rod is connected to the first apex corner of the second connecting surface; the first end of the second deformable rod is connected to the second apex corner of the first connecting surface, and the second end of the second deformable rod is connected to the second apex corner of the second connecting surface; the first end of the third deformable rod is connected to the third apex corner of the first connecting surface, and the second end of the third deformable rod is connected to the third apex corner of the second connecting surface; the first end of the fourth deformable rod is connected to the fourth apex corner of the first connecting surface, and the second end of the fourth deformable rod is connected to the fourth apex corner of the second connecting surface.

[0015] The third ends of the first deformable rod, the second deformable rod, the third deformable rod, and the fourth deformable rod all point to the center point of the circumferential negative Poisson's ratio structure.

[0016] The first electrode, the second electrode, and the sensing unit are all disposed within the housing. The first electrode is attached to the first surface of the sensing unit, and the second electrode is attached to the second surface of the sensing unit. The first and second surfaces of the sensing unit are symmetrical about the sensing unit.

[0017] The first end of the first wire is connected to the first electrode, and the second end of the first wire is electrically connected to the signal module; the first end of the second wire is connected to the second electrode, and the second end of the second wire is electrically connected to the signal module.

[0018] Optionally, the signal module includes a first pin, a second pin, a microcontroller, a circuit board, and a power interface;

[0019] Both the microcontroller and the power interface are fixed on the circuit board, and the power interface is used to supply power to the microcontroller.

[0020] The first pin and the second pin are fixed on the microcontroller. The first pin is electrically connected to the second end of the first wire, and the second pin is electrically connected to the second end of the second wire.

[0021] The microcontroller acquires the resistance signal of the sensing unit through the first pin, the second pin, the first wire, the second wire, the first electrode, and the second electrode.

[0022] Optionally, the housing includes a first outer shell and a second outer shell; the first outer shell is provided with a first reserved hole, and the second outer shell is provided with a second reserved hole; the first outer shell includes a body, a first extending surface, and a second extending surface;

[0023] The main body is provided with an opening surface, which extends to both sides in the long axis direction of the sensing unit to form a first extension surface and a second extension surface. The first extension surface, the second extension surface and the opening surface constitute a connecting surface, which has the same shape and size as the second outer shell. Both the first extension surface and the second extension surface are fixedly connected to the second outer shell.

[0024] Optionally, the first extension surface and the second extension surface are bonded to the second housing using silicone adhesive.

[0025] Optionally, the shell is made of silicone.

[0026] Optionally, both the first electrode and the second electrode are made of copper foil.

[0027] Optionally, the number of circumferential negative Poisson's ratio structures is four, with the first panels of each circumferential negative Poisson's ratio structure located on the same plane and connected to each other to form a square, and the second panels of each circumferential negative Poisson's ratio structure located on the same plane and connected to each other to form a square.

[0028] The present invention also provides a method for preparing the above-mentioned shell, comprising the following steps:

[0029] Mixing silicone A and silicone B, both with a Shore hardness of 40 and the same mass, yields a mixed silicone.

[0030] The mixed silicone was stirred at 100 r / min for 5 minutes using a magnetic stirrer and then poured into a 3D-printed white resin mold. The mold was left to stand at room temperature and pressure for 12 hours to obtain the shell.

[0031] The present invention also provides a method for preparing the above-mentioned elastomer skeleton structure, comprising the following steps:

[0032] Construct a 3D printing model, which includes an elastomer skeleton structure model and a support structure model;

[0033] Tango material and VeroCyan material are mixed at a mass ratio of 20:1 to obtain a hybrid printing material; the hybrid printing material is used as the material for the elastomer skeleton structure, and SUP705 material is used as the material for the support structure. The 3D printing model is then printed to obtain the initial elastomer skeleton structure.

[0034] The support structure in the initial elastomer skeleton structure is removed by water jet washing to obtain the elastomer skeleton structure.

[0035] The present invention also provides a method for preparing the above-mentioned sensing unit, comprising the following steps:

[0036] After uniformly applying petroleum jelly inside the composite material mold, several elastomer skeleton structures are fixed inside the composite material mold.

[0037] Mix HY-F662 material and foaming silicone A and foaming silicone B of the same mass to obtain mixed foaming silicone; stir the mixed foaming silicone for 120s and pour it into a composite material mold; place the composite material mold in a drying oven and heat it at 80℃ for 30min; take it out and let it stand at room temperature and pressure for 24h to obtain an initial composite material with several elastomer skeleton structures.

[0038] Deionized water and graphite with a microscale size of 10 μm were mixed at a mass ratio of 10:1 and stirred at 100 r / min for 2 min using a magnetic stirrer to obtain a graphite ink dispersion. The initial composite material was immersed in the graphite ink dispersion and immersed in a vacuum at -0.1 MPa and 25 °C for 48 h. After being removed, it was dried at 120 °C under normal pressure for 3 h to remove moisture, thus obtaining the sensing unit. The sensing unit has a sponge-like porous structure inside.

[0039] The effects of this invention are as follows:

[0040] This invention relates to a composite material in a wearable flexible sensor based on a circumferential negative Poisson's ratio structure. Guided by the deformation of the elastomer skeleton structure, it can simultaneously contract inward in both the left-right and front-back directions during vertical compression. This solves the problem of low measurement sensitivity caused by the outward expansion in the left-right and front-back directions during vertical compression of traditional flexible sensors. At the same time, embedding the elastomer skeleton structure in the composite material improves the mechanical performance of the sensor, enabling it to sense greater forces under the same compression deformation. This solves the problem of the small sensing range of traditional flexible sensors and resolves the contradiction between improving the sensing range and measurement sensitivity of traditional flexible sensors. It has the advantage of simultaneously improving both the sensing range and measurement sensitivity of the sensor.

[0041] 2. The elastomeric skeleton structure in the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of this invention is made of Tango and VeroCyan, which have the advantages of adjustable hardness and good compression recovery.

[0042] 3. The sensing unit of the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of this invention uses graphite with a micro-size of 10um as a highly conductive functional material. The composite material is impregnated and adsorbed by graphite ink dispersion to achieve the attachment of the highly conductive functional material. Compared with conductive materials such as graphene, carbon nanotubes, and silver nanowires, it has the advantages of simple preparation process and low manufacturing cost.

[0043] 4. The outer shell of the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of this invention is made of silicone with a Shore hardness of 40. It has good flexibility when it fits with clothing, does not affect the normal movement of the human body, and has the advantages of good insulation and softness to the skin. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the three-dimensional structure of the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of the present invention;

[0045] Figure 2 This is a three-dimensional cross-sectional view of the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of the present invention.

[0046] Figure 3 This is a schematic diagram of the elastomer skeleton structure and the circumferential negative Poisson's ratio structure of the present invention;

[0047] Figure 4 This is a schematic diagram of the compression process of the circumferential negative Poisson's ratio structure of the present invention;

[0048] Figure 5 This is a comparison diagram of the mechanical properties of the sensing unit of this invention and a material without a negative Poisson's ratio structure during compression.

[0049] Figure 6 This is a comparison diagram of the electrical conductivity of the sensing unit of this invention and that of a material without a negative Poisson's ratio structure during compression.

[0050] Figure 7 This is a comparison chart of the sensitivity performance of the sensing unit of this invention and materials without a negative Poisson's ratio structure during compression.

[0051] In the diagram: 1. Signal module; 2. Sensing module; 3. First wire; 4. Second wire; 11. Microcontroller; 12. Power interface; 13. First pin; 14. Second pin; 21. First housing; 22. First electrode; 23. Elastomer skeleton structure; 24. Composite material body; 25. Second electrode; 26. Second housing; 231. First circumferential negative Poisson's ratio structure; 232. Second circumferential negative Poisson's ratio structure; 233. Third circumferential negative Poisson's ratio structure; 234. Fourth circumferential negative Poisson's ratio structure; 2311. First deformable rod; 2312. Second deformable rod; 2313. Third deformable rod; 2314. Fourth deformable rod; 2315. First panel; 2316. Second panel. Detailed Implementation

[0052] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0053] Figure 1 This is a schematic diagram of the three-dimensional structure of the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of the present invention. Figure 1As shown, the present invention provides a wearable flexible sensor based on a circumferential negative Poisson's ratio structure, including a signal module 1, a sensing module 2, a first wire 3, and a second wire 4.

[0054] like Figure 2 As shown, the sensing module 2 includes a housing, a first electrode 22, a second electrode 25, and a sensing unit; the signal module 1 includes a first pin 13, a second pin 14, a microcontroller 11, a circuit board, and a power interface 12; the housing includes a first outer shell 21 and a second outer shell 26; the first outer shell 21 includes a body, a first extension surface, and a second extension surface.

[0055] The main body has an opening that extends to both sides along the long axis of the sensing unit, forming a first extension surface and a second extension surface. The first extension surface, the second extension surface, and the opening surface constitute a connecting surface, which has the same shape and size as the second outer shell 26. Both the first and second extension surfaces are fixedly connected to the second outer shell 26. In this embodiment, the first and second extension surfaces are bonded to the second outer shell 26 with silicone adhesive to create an insulating shell, thereby preventing leakage.

[0056] The first electrode 22, the second electrode 25, and the sensing unit are all disposed within the housing; the first electrode 22 is bonded to the first surface of the sensing unit, and the second electrode 25 is bonded to the second surface of the sensing unit, with the first and second surfaces of the sensing unit being symmetrical about the sensing unit. In this embodiment, both the first electrode 22 and the second electrode 25 are made of copper foil.

[0057] The first housing 21 has a first reserved hole, and the second housing 26 has a second reserved hole. The first end of the first wire 3 passes through the first reserved hole and is positioned between the first electrode 22 and the first surface of the sensing unit. The second end of the first wire 3 is electrically connected to the first pin 13. The first end of the second wire 4 passes through the second reserved hole and is positioned between the second electrode 25 and the second surface of the sensing unit. The second end of the second wire 4 is electrically connected to the second pin 14. Both the first pin 13 and the second pin 14 are soldered onto the microcontroller 11. The microcontroller 11 and the power interface 12 are both fixed on the circuit board, and the power interface 12 is used to supply power to the microcontroller 11. The microcontroller 11 acquires the resistance signal of the sensing unit through the first pin 13, the second pin 14, the first wire 3, the second wire 4, the first electrode 22, and the second electrode 25.

[0058] The sensing unit includes a composite material body 24 and several elastic skeleton structures 23 uniformly distributed inside the composite material body 24; the elastic skeleton structure 23 includes several circumferential negative Poisson's ratio structures.

[0059] like Figure 3As shown, the circumferential negative Poisson's ratio structure includes a first panel 2315, a second panel 2316, a first deformable rod 2311, a second deformable rod 2312, a third deformable rod 2313, and a fourth deformable rod 2314; the first panels 2315 of each circumferential negative Poisson's ratio structure are located on the same plane and are connected to each other, and the second panels 2316 of each circumferential negative Poisson's ratio structure are located on the same plane and are connected to each other.

[0060] The first panel 2315 and the second panel 2316 are the same size and shape, and the first panel 2315 and the second panel 2316 are parallel; the line connecting the center point of the first panel 2315 and the center point of the second panel 2316 is perpendicular to the first panel 2315.

[0061] Both the first panel 2315 and the second panel 2316 are hollow squares; the surface of the first panel 2315 facing the second panel 2316 is defined as the first connecting surface, and the surface of the second panel 2316 facing the first panel 2315 is defined as the second connecting surface.

[0062] The first deformable rod 2311, the second deformable rod 2312, the third deformable rod 2313, and the fourth deformable rod 2314 are all the same size and are all V-shaped.

[0063] The first end of the first deformable rod 2311 is connected to the first apex of the first connecting surface, and the second end of the first deformable rod 2311 is connected to the first apex of the second connecting surface; the first end of the second deformable rod 2312 is connected to the second apex of the first connecting surface, and the second end of the second deformable rod 2312 is connected to the second apex of the second connecting surface; the first end of the third deformable rod 2313 is connected to the third apex of the first connecting surface, and the second end of the third deformable rod 2313 is connected to the third apex of the second connecting surface; the first end of the fourth deformable rod 2314 is connected to the fourth apex of the first connecting surface, and the second end of the fourth deformable rod 2314 is connected to the fourth apex of the second connecting surface.

[0064] The third ends of the first deformable rod 2311, the second deformable rod 2312, the third deformable rod 2313, and the fourth deformable rod 2314 all point to the center point of the circumferential negative Poisson's ratio structure.

[0065] In this embodiment, as Figure 3As shown, there are four circumferential negative Poisson's ratio structures. These four structures are defined as the first circumferential negative Poisson's ratio structure 231, the second circumferential negative Poisson's ratio structure 232, the third circumferential negative Poisson's ratio structure 233, and the fourth circumferential negative Poisson's ratio structure 234. The first panels 2315 of the first, second, third, and fourth circumferential negative Poisson's ratio structures 231, 2315, and 2315 of the fourth circumferential negative Poisson's ratio structure 234 are located in the same plane and are connected to each other to form a square. The second panels 2316 of the first, second, third, and fourth circumferential negative Poisson's ratio structures 231, 2316, and 2316 of the fourth circumferential negative Poisson's ratio structure 234 are located in the same plane and are connected to each other to form a square. Several elastomeric skeleton structures 23 form four cuboids that are evenly distributed inside the composite material body 24.

[0066] like Figure 4 As shown, under vertical compression, the circumferential negative Poisson's ratio structure guides the composite material body 24 to contract. In the left-right direction, the composite material body 24 exhibits a negative Poisson's ratio contraction phenomenon, where the left-right inward compression increases with increasing vertical compression. Because the first deformation rod 2311, second deformation rod 2312, third deformation rod 2313, and fourth deformation rod 2314 within the circumferential negative Poisson's ratio structure are axially symmetrically distributed around the line connecting the center points of the vertical and horizontal planes, the composite material body 24 also achieves negative Poisson's ratio contraction in the front-back direction. That is, under the guidance of the circumferential negative Poisson's ratio structure of the elastomer skeleton structure 23, the composite material body 24 achieves circumferential negative Poisson's ratio contraction under vertical compression conditions. The number of contact points in the conductive network of the composite material body 24 increases rapidly, and the resistance decreases rapidly. The microcontroller 11 reads the resistance information, and subsequently, the corresponding parameters can be obtained using the resistance information. The embedding of the elastomer skeleton structure 23 further enhances the mechanical performance of the sensor, providing advantages such as high measurement sensitivity and a large sensing range.

[0067] The shell is prepared as follows:

[0068] Silicone A and silicone B, both with a Shore hardness of 40 and equal in mass, were mixed to obtain a mixed silicone. In this embodiment, the mass of both silicone A and silicone B was 30g.

[0069] The mixed silica gel was stirred at 100 rpm for 5 minutes using a magnetic stirrer, then poured into a 3D-printed white resin mold and left to stand at room temperature and pressure for 12 hours to obtain the shell. When the shell consists of a first outer shell and a second outer shell, the same method can be used to obtain both the first and second outer shells.

[0070] The preparation method of the elastomer framework structure is as follows:

[0071] Construct a 3D printing model, which includes an elastomer skeleton structure model and a support structure model.

[0072] Tango and VeroCyan materials were mixed at a mass ratio of 20:1 to obtain a hybrid printing material. This hybrid printing material was used as the material for the elastomer skeleton structure, and SUP705 material was used as the material for the support structure. The mixture was then used in conjunction with a 3D printing model to obtain the initial elastomer skeleton structure. In this embodiment, a Stratasys J750 3D printer was selected for printing.

[0073] The elastomer skeleton structure is obtained by removing the supporting structure in the initial elastomer skeleton structure through water jet washing.

[0074] The method for fabricating the sensing unit is as follows:

[0075] After uniformly applying Vaseline inside the composite material mold, several elastomer skeleton structures are fixed inside the composite material mold.

[0076] HY-F662 material and equal masses of foaming silicone A and foaming silicone B were mixed to obtain a mixed foaming silicone. The mixed foaming silicone was stirred for 120 seconds and then poured into a composite material mold. The composite material mold was placed in a drying oven and heated at 80°C for 30 minutes. After removal, it was allowed to stand at room temperature and pressure for 24 hours to obtain an initial composite material body with several elastomer skeleton structures. In this embodiment, the mass of both foaming silicone A and foaming silicone B was 8g.

[0077] Deionized water and graphite with a microscopic size of 10 μm were mixed at a mass ratio of 10:1 and stirred at 100 rpm for 2 minutes using a magnetic stirrer to obtain a graphite ink dispersion. The initial composite material was immersed in the graphite ink dispersion and impregnated under vacuum conditions of -0.1 MPa and 25°C for 48 hours. After removal, it was dried at 120°C under normal pressure for 3 hours to remove moisture, resulting in a sensing unit. The sensing unit has a sponge-like porous structure inside. In this embodiment, the mass of deionized water was 50 g and the mass of graphite was 5 g.

[0078] The elastic skeleton structure in the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of this invention is subjected to uniform compression under the same compression conditions, along with a material that does not possess a negative Poisson's ratio structure. Figure 5 As shown, the mechanical properties of the composite material are enhanced due to the elastomeric skeleton structure. Under the same compression conditions, wearable flexible sensors based on the circumferential negative Poisson's ratio structure require a larger external force. Figure 5Experimental results show that the wearable flexible sensor based on the circumferential negative Poisson's ratio structure of the present invention has a large range of 0-150 kPa, which is 2.06 times that of the sensor without a negative Poisson's ratio structure.

[0079] Figure 6 The relationship between compression and resistance is shown. During the compression process of 0-12mm, the present invention reduces the volume of the conductive material that can be attached due to the embedded elastic skeleton structure, thus achieving a large resistance value of 5.6MΩ. Under the same compression, the resistance decrease of the composite material is greater than that of the structure without negative Poisson's ratio, indicating that the composite material of the present invention has a better resistance variation range.

[0080] Figure 7 This demonstrates the relationship between strain and the rate of change of resistance. Based on the principles of sensor sensitivity calculation, the slope G of the curve representing the rate of change of resistance versus strain... F Defined as the sensitivity of the sensor. Figure 7 The results show that under 30%-40% compressive strain, the sensitivity of the composite material of the present invention is 0.50, and 0.34 without a negative Poisson's ratio structure; under 65%-80% compressive strain, the sensitivity of the composite material of the present invention is 1.17, and 0.94 without a negative Poisson's ratio structure, indicating that the composite material of the present invention has even higher sensitivity.

[0081] It should be understood that in the description of this invention, the terms "first," "second," etc., are used only to simplify the textual description and distinguish it from similar objects, and should not be understood as a specific sequential relationship.

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A wearable flexible sensor based on a circumferential negative Poisson's ratio structure, characterized in that, It includes a signal module, a sensing module, a first wire, and a second wire; The sensing module includes a housing, a first electrode, a second electrode, and a sensing unit; the sensing unit includes a composite material body and a plurality of elastomeric skeleton structures uniformly distributed within the composite material body; the elastomeric skeleton structure includes a plurality of circumferential negative Poisson's ratio structures. The circumferential negative Poisson's ratio structure includes a first panel, a second panel, a first deformable rod, a second deformable rod, a third deformable rod, and a fourth deformable rod; the first panels of each of the circumferential negative Poisson's ratio structures are located on the same plane and are connected to each other, and the second panels of each of the circumferential negative Poisson's ratio structures are located on the same plane and are connected to each other; The first panel and the second panel are the same size and shape, and the first panel and the second panel are parallel; the line connecting the center point of the first panel and the center point of the second panel is perpendicular to the first panel. Both the first panel and the second panel are hollow squares; the surface of the first panel facing the second panel is defined as the first connecting surface, and the surface of the second panel facing the first panel is defined as the second connecting surface. The first deformable rod, the second deformable rod, the third deformable rod, and the fourth deformable rod are the same size and are all V-shaped; The first end of the first deformable rod is connected to the first apex corner of the first connecting surface, and the second end of the first deformable rod is connected to the first apex corner of the second connecting surface; the first end of the second deformable rod is connected to the second apex corner of the first connecting surface, and the second end of the second deformable rod is connected to the second apex corner of the second connecting surface; the first end of the third deformable rod is connected to the third apex corner of the first connecting surface, and the second end of the third deformable rod is connected to the third apex corner of the second connecting surface; the first end of the fourth deformable rod is connected to the fourth apex corner of the first connecting surface, and the second end of the fourth deformable rod is connected to the fourth apex corner of the second connecting surface. The third ends of the first deformable rod, the second deformable rod, the third deformable rod, and the fourth deformable rod all point to the center point of the circumferential negative Poisson's ratio structure. The first electrode, the second electrode, and the sensing unit are all disposed within the housing. The first electrode is attached to the first surface of the sensing unit, and the second electrode is attached to the second surface of the sensing unit. The first and second surfaces of the sensing unit are symmetrical about the sensing unit. The first end of the first wire is connected to the first electrode, and the second end of the first wire is electrically connected to the signal module; the first end of the second wire is connected to the second electrode, and the second end of the second wire is electrically connected to the signal module.

2. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 1, characterized in that, The signal module includes a first pin, a second pin, a microcontroller, a circuit board, and a power interface; Both the microcontroller and the power interface are fixed on the circuit board, and the power interface is used to supply power to the microcontroller. The first pin and the second pin are fixed on the microcontroller. The first pin is electrically connected to the second end of the first wire, and the second pin is electrically connected to the second end of the second wire. The microcontroller acquires the resistance signal of the sensing unit through the first pin, the second pin, the first wire, the second wire, the first electrode, and the second electrode.

3. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 1, characterized in that, The housing includes a first outer shell and a second outer shell; the first outer shell is provided with a first reserved hole, and the second outer shell is provided with a second reserved hole; the first outer shell includes a body, a first extension surface, and a second extension surface; The main body is provided with an opening surface, which extends to both sides in the long axis direction of the sensing unit to form a first extension surface and a second extension surface. The first extension surface, the second extension surface and the opening surface constitute a connecting surface, which has the same shape and size as the second outer shell. Both the first extension surface and the second extension surface are fixedly connected to the second outer shell.

4. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 3, characterized in that, The first extension surface and the second extension surface are bonded to the second housing with silicone adhesive.

5. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 1, characterized in that, The shell is made of silicone.

6. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 1, characterized in that, Both the first electrode and the second electrode are made of copper foil.

7. The wearable flexible sensor based on a circumferential negative Poisson's ratio structure according to claim 1, characterized in that, The number of circumferential negative Poisson's ratio structures is four. The first panel of each circumferential negative Poisson's ratio structure is located on the same plane and is connected to each other to form a square. The second panel of each circumferential negative Poisson's ratio structure is located on the same plane and is connected to each other to form a square.

8. A method for preparing the shell according to any one of claims 1-7, characterized in that, Includes the following steps: Mixing silicone A and silicone B, both with a Shore hardness of 40 and the same mass, yields a mixed silicone. The mixed silicone was stirred at 100 r / min for 5 minutes using a magnetic stirrer and then poured into a 3D-printed white resin mold. The mold was left to stand at room temperature and pressure for 12 hours to obtain the shell.

9. A method for preparing an elastomer skeleton structure according to any one of claims 1-7, characterized in that, Includes the following steps: Construct a 3D printing model, which includes an elastomer skeleton structure model and a support structure model; Tango material and VeroCyan material are mixed at a mass ratio of 20:1 to obtain a hybrid printing material; the hybrid printing material is used as the material for the elastomer skeleton structure, and SUP705 material is used as the material for the support structure. The 3D printing model is then printed to obtain the initial elastomer skeleton structure. The support structure in the initial elastomer skeleton structure is removed by water jet washing to obtain the elastomer skeleton structure.

10. A method for preparing a sensing unit according to any one of claims 1-7, characterized in that, Includes the following steps: After uniformly applying petroleum jelly inside the composite material mold, several elastomer skeleton structures are fixed inside the composite material mold. Mix HY-F662 material and foaming silicone A and foaming silicone B of the same mass to obtain mixed foaming silicone; stir the mixed foaming silicone for 120s and pour it into a composite material mold; place the composite material mold in a drying oven and heat it at 80℃ for 30min; take it out and let it stand at room temperature and pressure for 24h to obtain an initial composite material with several elastomer skeleton structures. Deionized water and graphite with a microscale size of 10 μm were mixed at a mass ratio of 10:1 and stirred at 100 r / min for 2 min using a magnetic stirrer to obtain a graphite ink dispersion. The initial composite material was immersed in the graphite ink dispersion and immersed in a vacuum at -0.1 MPa and 25 °C for 48 h. After being removed, it was dried at 120 °C under normal pressure for 3 h to remove moisture, thus obtaining the sensing unit. The sensing unit has a sponge-like porous structure inside.

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