Flexible large strain detection device and detection method

Abstract

The invention relates to a flexible large strain detection device and a detection method, realizes high-precision detection of large strain on the surface of a human body, overcomes the problems of overhigh rigidity and difficult strain detection positioning of a flexible sensor in the prior art, and has a wide application prospect in the sensing field.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a flexible large strain detection device and a detection method. Background Art

[0002] Flexible sensors have great development prospects in the fields of medical treatment, sports monitoring, smart wearables and smart homes. Their good fit with the human body and softness make them unique in monitoring physiological parameters, realizing intelligent control and improving user experience. Thin film-based sensors often use conductive elements with greater rigidity, which will restrict the movement of human joints when the human body is moving. Since people usually need 30%-100% tensile strain when they are active in their daily lives, these elements can no longer meet the performance requirements of the new generation of electronic devices. Fiber-based sensors are made of soft fabric materials, which can better fit the curves of the human body and the surface of the skin, and have breathable and sweat-wicking properties. At present, commonly used optical fiber strain sensors face the problems of limited long-term strain measurement range that the fiber grating itself can withstand, measurement accuracy will be affected by the installation angle and installation angle deviation, and poor stretchability. Therefore, the manufacture of strain sensors with excellent flexibility, stretchability and comfort has become the current research direction.

[0003] At present, relevant technicians have done some research in this field. Patent CN202311596339.8 introduces a fiber optic strain sensor, which uses the energy distribution of the transmitted light field to detect the degree of strain. Although it has high accuracy, it cannot detect large strains and locate large-area strains, and its installation and calibration are complicated, which limits its application in the field of smart homes. Patent CN202410699536.0 introduces a thin film piezoelectric sensor. This method collects data by arranging a number of piezoelectric film sensors to obtain information corresponding to the array position, but it has poor elasticity and is cumbersome to wear, which limits its application in daily life. Patent CN202110576789.5 introduces a two-dimensional large strain sensing fabric sensor and preparation method. The fiber is dipped in a nano-conductive layer to solve the problem that wearable fabrics often face the problem of insufficient isotropic strain range in a large range in a two-dimensional plane and poor air permeability after functional modification. However, the detection relies on the stretching of the nano-conductive layer to produce cracks, thereby increasing the resistance and reducing the durability of the sensor. At the same time, there is also a lack of positioning methods, which limits its application in different fields.

[0004] Therefore, there is a need for a flexible large strain detection device with good environmental stability, good strain performance, accurate positioning over a large range, good air permeability, simple installation, good durability, and simple preparation process. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flexible large strain detection device and a detection method to solve the problems in the prior art that flexible sensors cannot detect large strains and are difficult to measure and locate over large areas.

[0006] The present invention provides a flexible strain detection device, which comprises an elastic fabric substrate and a stretchable sensing fiber; wherein the stretchable sensing fiber is a skin-core structure, wherein the skin layer is a polymer elastomer, and the core layer comprises an ion conductor-containing polymer material.

[0007] Preferably, the stretchable sensing fibers in the device are arranged as warp yarns and weft yarns at intervals and interwoven on the elastic fabric base; the intersection points of the warp yarns and the weft yarns are separated by the stretchable fiber cortex.

[0008] The stretchable sensing fibers are arranged crosswise to form a grid structure.

[0009] Furthermore, the warp yarns are arranged in parallel at equal intervals; and the weft yarns are arranged in parallel at equal intervals.

[0010] The warp threads and the weft threads are woven alternately on the upper and lower surfaces of the base fabric.

[0011] The stretchable sensing fiber conducts ions through the movement of polymer macromolecular chains. The ion transmission path can stably change under large tensile strain. The stretchable sensing fibers are arranged crosswise to form a grid structure, and their intersections are separated by insulating cortical materials. Different applied pressures result in different changes in the resistance of the stretchable sensing fiber. By detecting the resistance change rate of the stretchable sensing fiber at different positions, accurate positioning detection of large strains of the object is provided. The device of the present invention realizes high-precision detection of large strains on the human body surface (tensile strain ≥ 200%, sensitivity GF ≥ 0.01).

[0012] The stretchable sensing fiber is tightly bonded to the flexible fabric substrate through weaving process and hot pressing technology.

[0013] Preferably, the ion conductor-containing polymer material is a composite material of an ion conductor and a polymer matrix; wherein the ion conductor includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, 1-vinyl-3-butylbis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide derivatives, lithium bis(fluorosulfonyl)imide derivatives, lithium hexafluorophosphate derivatives, and 1-vinyl-3-butylbis(trifluoromethanesulfonyl)imide derivatives; and the polymer matrix includes one or more of polyurethane, polyvinyl alcohol, polydimethylsiloxane, silicone rubber, polyvinylidene fluoride, polyurethane derivatives, polyvinyl alcohol derivatives, polydimethylsiloxane derivatives, silicone rubber derivatives, and polyvinylidene fluoride derivatives.

[0014] Furthermore, the mass percentage of the ion conductor in the ion conductor-containing polymer material is 5-35%.

[0015] As described above, in the ion conductor-containing polymer material, the ion conductor is loaded in the polymer matrix, and forms a coordination bond with the ion conductor through a highly electronegative ether bond and dissociates salt molecules, so that the ions are transported by intra-chain and inter-chain hopping.

[0016] Preferably, the polymer elastomer is a polymer elastomer with electrical insulation properties; wherein the polymer elastomer with electrical insulation properties includes one or more of polyamide, polyurethane, and polycarbonate. The polymer elastomer with electrical insulation properties is conducive to improving the mechanical properties and environmental stability of the stretchable sensing fiber, and provides insulation properties to prevent electromagnetic interference, which is conducive to expanding the application range of flexible large strain detection devices based on stretchable sensing fibers.

[0017] Preferably, the elastic fabric substrate includes one or more of spandex fabric and nylon fabric, which provides mechanical support for the sensing fiber and realizes long-term, high-precision flexible large strain detection.

[0018] The present invention provides a method for preparing any of the flexible strain detection devices, comprising: compounding a stretchable sensing fiber and an elastic fabric substrate by weaving and hot pressing.

[0019] The weaving means that the stretchable sensing fibers are arranged in the form of warp and weft yarns and interwoven in the flexible elastic fabric substrate according to a fabric structure, and the intersections are separated by insulating skin materials.

[0020] The hot pressing refers to hot pressing and bonding reinforcement by adhesive.

[0021] The present invention also provides a strain positioning detection method of a flexible large strain detection device based on stretchable sensing fibers, wherein the stretchable sensing fibers are arranged crosswise to form a grid structure, and their intersections are separated by insulating cortical materials. Different applied pressures result in different resistance changes in the stretchable sensing fibers, and by detecting the resistance change rate of the stretchable sensing fibers at different positions, accurate positioning detection of large strains of an object is provided, and the detection site density is regulated by the warp and weft density of the stretchable sensing fibers.

[0022] (1) A flexible strain detection device is used. Before the structure is deformed, multiple sets of constant AC power supplies are used to simultaneously supply power to both ends of multiple sets of stretchable sensing fibers. The potentials of all stretchable sensing fibers are collected during power supply. The initial resistances of the stretchable sensing fibers in the weft direction are recorded as W1, W2, W3, ... Wn in sequence; the initial resistances of the stretchable sensing fibers in the warp direction are recorded as J1, J2, J3, ... Jn in sequence.

[0023] (2) After the structure is deformed, the deformation resistance obtained by n power supply excitations during the deformation process is recorded as The W and J in the resistor represent the longitude and latitude directions, the lower right corner subscript n represents the number of the stretchable sensing fiber, and the upper right corner subscript m represents the number of power supply excitations;

[0024] (3) According to the initial resistance R0 in the longitudinal and axial directions before and after deformation and the deformation resistance R, the resistance change R-R0=ΔR is determined, thereby obtaining the relative resistance change rate The precise strain is obtained according to the sensing sensitivity of the stretchable sensing fiber GF.

[0025] Note: Initial resistance R0 and deformation resistance R, where the initial resistance R0 in the longitudinal direction is marked J1, J2, J3, ... Jn in sequence, and the initial resistance R0 in the dimensional direction is marked W1, W2, W3, ... Wn in sequence; the deformation resistance R in the longitudinal direction is The axial deformation resistance R is

[0026] Resistance change, such as longitudinal direction: Direction:

[0027] The stretchable sensing fiber with an R0 / ΔR ratio of 0 does not generate strain, thereby determining the position where strain is generated by applying pressure and the strain radiation range, and determining the degree of strain according to the resistance-strain conversion formula. Gauss2D is used to fit the strain data of the longitudinal and dimensional stretchable sensing fibers to obtain the positional relationship between the position where strain is generated by applying pressure and the stretchable sensing fiber.

[0028] Specifically, the resistance-strain conversion formula: The conversion formula between the relative resistance change rate and the strain is:

[0029] Specifically, in the above formula, ΔL is the change in length of the stretchable sensing fiber, L0 is the initial length of the stretchable sensing fiber, ΔR is the change in resistance of the stretchable sensing fiber, R0 is the initial resistance of the stretchable sensing fiber, and GF is the sensing sensitivity of the stretchable sensing fiber.

[0030] When no pressure is applied, the length of the stretchable sensing fiber remains unchanged, that is, the output resistance remains unchanged; when pressure is applied to the grid, the stretchable sensing fibers within a certain range near the grid produce strain along with the flexible fabric substrate, and the stretchable sensing fibers constituting the grid have the largest strain, that is, the output resistance changes the most. Perpendicular to the strain attenuation direction, the output resistance change of the parallel stretchable sensing fibers decreases as the strain decreases, thereby determining the location where the pressure produces strain and the strain radiation range.

[0031] The present invention provides an application of the flexible strain detection device in the fields of medical treatment, human body monitoring, smart wearables, smart homes, and transportation.

[0032] Beneficial Effects

[0033] (1) The stretchable sensing fiber provided by the present invention has excellent stretchability and resilience, as well as strain sensing performance and stable conductive performance;

[0034] (2) The strain positioning method used in the flexible large strain detection device based on the stretchable sensing fiber provided by the present invention has accurate positioning capability; it overcomes the problems in the prior art of the flexible sensing having too high stiffness, not supporting large strain, and difficulty in positioning for large-area measurement;

[0035] (3) The flexible large strain detection device based on ion conductive fiber provided by the present invention has a simple and stable overall structure, supports synchronous scanning, and can meet the high demand for instantaneous strain positioning testing;

[0036] (4) The present invention adopts stretchable sensing fibers, which have excellent fatigue resistance, bending resistance, stretchability, and good fit with the human body, and support the detection of large strains; the number of sensing units increases exponentially with the increase in the scale of the stretchable sensing fibers, and supports large-area precise measurement and positioning; the density of the sensing units is adjustable, and compared with the prior art, fewer conductive elements can be used to achieve a greater sensing unit density, which has the advantages of high and adjustable sensing resolution.

[0037] (5) The present invention realizes high-precision detection of large strain on the human body surface (the Fundamentals of Biomechanics points out that the range of human ligament activity is less than 50%, and the general specification of resistive strain pressure sensors requires a sensor sensitivity of more than 0.02. The present invention has a tensile strain of ≥200% and a sensitivity GF of ≥0.01, and has broad application prospects in the field of sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of the flexible large strain detection device of the present invention;

[0039] Figure 2 Schematic diagram of the skin-core structure of the stretchable sensing fiber of the present invention;

[0040] Figure 3 is the molecular formula of the self-made elastomer in the stretchable sensing fiber of the present invention;

[0041] Figure 4 Strain diagrams of (a) 1 cm stretchable sensing fibers of Example 1 and (b) 2;

[0042] Figure 5This is a resistance change diagram of the 1 cm stretchable sensing fiber in Example 1;

[0043] Figure 6 This is a physical picture of a prototype of the flexible large strain detection device of the present invention;

[0044] Figure 7 A model diagram of the flexible large strain detection device of the present invention;

[0045] Figure 8 It is a sensor fitting schematic diagram of the flexible large strain detection device of the present invention;

[0046] in:

[0047] 1. Stretchable sensing fibers;

[0048] 2. Flexible elastic fabric base;

[0049] 3. Polyurethane adhesive;

[0050] 4. Stretchable sensing fiber cortex;

[0051] 5. Stretchable sensing fiber core layer;

[0052] 6. Stretchable sensing fiber model;

[0053] 7. Strain point model; DETAILED DESCRIPTION

[0054] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0055] Example 1

[0056] like Figure 1 As shown, this embodiment provides a flexible large strain detection device, which includes an upper layer of stretchable sensing fiber and a lower layer of flexible elastic fabric substrate; the stretchable sensing fiber has a skin-core structure, wherein the core layer is a conductive polymer ion conductor, and the skin layer is a polymer elastomer with electrical insulation properties.

[0057] Specifically, Figure 2 As shown, the skin layer of the stretchable sensing fiber is made of thermoplastic polyurethane, and the core layer is made of polyurethane and lithium bis(trifluoromethanesulfonyl)imide; wherein 10wt% of the ion conductor lithium bis(trifluoromethanesulfonyl)imide is loaded in the polymer matrix polyurethane, wherein the general structure of the polyurethane is as follows Figure 3 As shown, where n≥10.

[0058] Specifically, in the polyurethane structural formula of this embodiment, n=25.

[0059] Further, the preparation of polyurethane in this embodiment: take 10g PTMG (polytetrahydrofuran) and place it in a three-necked flask, heat the oil bath to 110°C, turn on the air pump to evacuate, and keep it for 60min to remove water from the device and PTMG. Turn off the vacuum pump, turn on the nitrogen, lower the system temperature to 80°C, use a pipette to transfer 2.10ml IPDI (isophorone diisocyanate), 0.05g DBTDL (dibutyltin dilaurate), and 3.9872g bis(trifluoromethanesulfonyl)imide lithium to 10ml DMAC (dimethylacetamide), inject the mixed solution with a syringe, and continue to react for 4h. Cool down to 60°C, weigh 0.35g AMPD (2-amino-2-methyl-1,3-propanediol) and dissolve it in 30ml DMAC and inject it into the reaction system, stir mechanically for 2h, heat to 80°C and continue to react for 5h, after the reaction is completed, transfer to a vacuum oven at 60°C and keep it for 24h.

[0060] Specifically, in the embodiment, a stretchable polyurethane elastomer material is designed and prepared based on polytetrahydrofuran diol (PTMG) rich in ether bonds. Multiple hydrogen bonds provide excellent tensile properties, and in-situ polymerized ionic liquid provides excellent electrical conductivity, ultimately obtaining a large tensile strain and a sensing capability that maintains stability after multiple stretching cycles (elongation = 300%, sensing sensitivity GF = 0.022). (As shown in FIG. Figure 4-5 shown).

[0061] Specifically, the flexible elastic fabric base is selected from 1+1 double rib spandex knitted fabric.

[0062] Specifically, Figure 6 As shown in the figure, based on the knitted structure, the stretchable sensing fibers are used as the warp and weft yarns, interwoven on the flexible fabric substrate at intervals of 1 cm, and reinforced with polyurethane adhesive by hot pressing to form a regular grid. Different applied pressures lead to different changes in the resistance of the stretchable sensing fibers. By detecting the resistance change rate of the stretchable sensing fibers at different positions, accurate positioning detection of large strains of objects can be provided.

[0063] Specifically, when no pressure is applied, the stretchable sensing fiber does not strain, that is, the output resistance remains unchanged; when pressure is applied to the grid, the stretchable sensing fiber within a certain range near the grid strains along with the substrate, and the stretchable sensing fiber at the strain center has the largest strain. During detection, eight sets of constant AC power supplies are used to simultaneously supply power to the eight sets of stretchable sensing fibers in the device. When powering, the potential of all stretchable sensing fibers is collected and recorded as Compare the resistance changes ΔR of different groups at the same time, according to Determine the degree of strain and locate it, such as Figure 7 As shown in the figure, along the strain attenuation direction, the output resistance change of the parallel stretchable ion conductive fibers decreases accordingly. Therefore, we believe that the strain center is located at the intersection of the warp stretchable sensing fiber with the largest strain and the weft stretchable sensing fiber with the largest strain. For the stretchable sensing fiber with a R0 and ΔR ratio of 0, we believe that it has not generated strain. In this way, the position where the pressure is applied to generate strain and the strain radiation range are determined. The eight groups The Gauss2D fitting formula is introduced to make the strain rate of each stretchable sensing fiber form a nonlinear surface to determine the overall strain degree. The relationship between the position where the pressure is applied to generate strain and the position of the stretchable sensing fiber is obtained by combining the strain data of the stretchable sensing fiber (e.g. Figure 8 shown).

[0064] Example 2

[0065] like Figure 1 As shown, this embodiment provides a flexible large strain detection device, which includes an upper layer of stretchable sensing fiber and a lower layer of flexible elastic fabric substrate; the stretchable sensing fiber has a skin-core structure, wherein the core layer is a conductive polymer ion conductor, and the skin layer is a polymer elastomer with electrical insulation properties.

[0066] Specifically, Figure 2 As shown, the skin layer of the stretchable sensing fiber is made of thermoplastic polyurethane, and the core layer is made of commercial polyamide and lithium bis(trifluoromethanesulfonyl)imide, wherein 10wt% of lithium bis(trifluoromethanesulfonyl)imide is loaded in the polyamide. (Comparison of sensing ability with Example 1 Figure 4 shown.)

[0067] Specifically, the flexible elastic fabric base is selected from 1+1 double rib spandex knitted fabric.

[0068] Specifically, on the basis of the knitted structure, the stretchable sensing fibers are used as the lining warp yarn and the lining weft yarn, respectively, and are interwoven on the flexible fabric base at intervals of 0.5 cm, and are hot-pressed to make the thermoplastic polyurethane skin layer adhere to the spandex fabric to form a regular stretchable sensing fiber grid.

[0069] Specifically, different applied pressures result in different changes in the resistance of the stretchable sensing fiber. By detecting the resistance change rate of the stretchable sensing fiber at different positions, precise positioning detection of large strains of objects can be provided.

[0070] Specifically, when no pressure is applied, the stretchable sensing fibers do not strain, that is, the output resistance remains unchanged; when pressure is applied to the grid, the stretchable sensing fibers within a certain range near the grid strain along with the substrate, and the four stretchable sensing fibers that constitute the grid have the largest strain, that is, the output resistance changes the most. Along the strain attenuation direction, the output resistance change of the parallel stretchable sensing fibers becomes smaller, thereby determining the position where the strain is generated by applying pressure and the strain radiation range, and determining the degree of strain based on the strain-resistance change rate fitting formula, and fitting the strain data of the stretchable sensing fibers near the grid to obtain the position relationship between the position where the strain is generated by applying pressure and the grid.

[0071] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A flexible strain detection device, characterized in that: The device comprises an elastic fabric substrate and a stretchable sensing fiber; wherein the stretchable sensing fiber is a skin-core structure, wherein the skin layer is a polymer elastomer, and the core layer comprises an ion conductor-containing polymer material.

2. The device according to claim 1, characterized in that: In the device, the stretchable sensing fibers are arranged as warp yarns and weft yarns at intervals and interwoven on an elastic fabric base; the intersections of the warp yarns and the weft yarns are separated by a stretchable fiber cortex.

3. The device according to claim 1, characterized in that: The ion conductor-containing polymer material is a composite material of an ion conductor and a polymer matrix; wherein the ion conductor comprises one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, 1-vinyl-3-butylbis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide derivatives, lithium bis(fluorosulfonyl)imide derivatives, lithium hexafluorophosphate derivatives, and 1-vinyl-3-butylbis(trifluoromethanesulfonyl)imide derivatives; and the polymer matrix comprises one or more of polyurethane, polyvinyl alcohol, polydimethylsiloxane, silicone rubber, polyvinylidene fluoride, polyurethane derivatives, polyvinyl alcohol derivatives, polydimethylsiloxane derivatives, silicone rubber derivatives, and polyvinylidene fluoride derivatives.

4. The device according to claim 1, characterized in that: The polymer elastomer is a polymer elastomer with electrical insulation properties; wherein the polymer elastomer with electrical insulation properties includes one or more of polyamide, polyurethane, and polycarbonate; The elastic fabric base includes one or more of spandex fabric and nylon fabric.

5. A method for preparing the flexible strain detection device according to any one of claims 1 to 4, comprising: The stretchable sensing fibers and elastic fabric substrate were composited by weaving and hot pressing.

6. The preparation method according to claim 5, characterized in that: The hot pressing refers to hot pressing and bonding reinforcement by adhesive.

7. A flexible strain detection method, comprising: (1) A flexible strain detection device is used. Before the structure is deformed, multiple sets of constant AC power supplies are used to simultaneously supply power to both ends of multiple sets of stretchable sensing fibers, and the potential of all stretchable sensing fibers is collected during power supply. The initial resistance of the weft-direction stretchable sensing fiber is denoted as W1, W2, W3, ... W n ; The initial resistance of the warp-direction stretchable sensing fiber is recorded as J1, J2, J3, ... J n ; (2) After the structure is deformed, the deformation resistance obtained by n power supply excitations during the deformation process is recorded as The W and J in the resistor represent the longitude and latitude directions, the lower right corner subscript n represents the number of the stretchable sensing fiber, and the upper right corner subscript m represents the number of power supply excitations; (3) According to the initial resistance R0 in the longitudinal and axial directions and the deformation resistance R before and after deformation, the resistance change R-R0=ΔR is determined, thereby obtaining the relative resistance change rate The precise strain is obtained according to the sensing sensitivity of the stretchable sensing fiber GF.

8. The detection method according to claim 7, characterized in that: The stretchable sensing fiber with an R0 / ΔR ratio of 0 does not generate strain, so the position where the strain is generated by applying pressure and the strain radiation range are determined. The degree of strain is determined according to the resistance-strain conversion formula, and the strain data of the stretchable sensing fiber in the longitudinal and dimensional directions are fitted to obtain the position relationship between the position where the strain is generated by applying pressure and the stretchable sensing fiber.

9. The detection method according to claim 7, characterized in that: The resistance strain conversion formula is: ΔL is the change in length of the stretchable sensing fiber, and L0 is the initial length of the stretchable sensing fiber.

10. An application of the flexible strain detection device according to claim 1 in the fields of medical treatment, human body monitoring, smart wearables, smart homes, and transportation.

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