Temperature-controllable flexible piezoresistive sensing material, preparation method and application thereof

Abstract

The present application belongs to the field of intelligent materials, and particularly discloses a temperature-controlled flexible piezoresistive sensing material with piezoresistive performance adaptive to temperature environment changes. The temperature-controlled flexible piezoresistive sensing material comprises a base resin and a conductive foam filler; wherein the weight percentage of the conductive foam filler in the base resin is 1% to 50%, the T g of the base resin is -30 to 35℃, preferably 0 to 33℃, and more preferably 15 to 30℃. The temperature-controlled flexible piezoresistive sensing material is based on its specific T g , and realizes adjustable pressure detection range. The RCR can stably respond to a large pressure of 500kPa to 1500kPa at an ambient temperature lower than T g . After the temperature is raised, the RCR can stably respond to a small pressure, and the pressure detection can be accurate to 10kPa, which is 50 times higher than under the foregoing conditions. The present application also discloses a preparation method and application of the temperature-controlled flexible piezoresistive sensing material. The temperature-controlled flexible piezoresistive sensing material can be used as a component of devices including intelligent, wearable, life monitoring or motion monitoring devices.

Description

Technical Field

[0001] This invention relates to a flexible piezoresistive sensing material, belonging to the field of smart materials, specifically a sensor material whose piezoresistive properties adapt to changes in temperature environment; this invention also relates to the preparation method and application of the aforementioned flexible piezoresistive sensing material. Background Technology

[0002] Flexible piezoresistive sensing materials are intelligent materials that deform under external force, resulting in changes in their resistance. They are the core sensing materials for stress-strain sensors and have broad application prospects in wearable electronic devices, fitness tracking, and robot sensing.

[0003] To prevent irreparable damage to the sensor caused by external pressure exceeding its operating range, piezoresistive sensors are generally required to possess both high sensitivity and a wide pressure detection range. Current research on piezoresistive sensing materials has achieved adjustable piezoresistive performance based on the application scenario; however, the influencing factors in different application scenarios are diverse. Clearly, controlling the piezoresistive performance of piezoresistive sensing materials through temperature changes is a more widely applicable and simpler method, but currently, there are no piezoresistive sensing materials whose piezoresistive performance can be controlled solely by temperature variations. Summary of the Invention

[0004] Therefore, the main objective of this invention is to provide a temperature-controlled flexible piezoresistive sensing material, its preparation method, and its applications, thereby increasing the diversity of controllable factors in flexible piezoresistive sensing materials. This invention provides a flexible piezoresistive sensing material based on its glass transition properties, specifically its glass transition temperature (T0). g The pressure detection range of this flexible piezoresistive sensing material is adjustable, ranging from below T... g Under ambient temperature, it can maintain a stable RCR response to high pressure (500kPa~1500kPa); while after increasing the temperature, its response to low pressure is stable, and the pressure detection accuracy can be as low as 10kPa, which is 50 times higher than under the aforementioned conditions.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] As one aspect of the present invention, a temperature-controlled flexible piezoresistive sensing material is provided, comprising a matrix resin and a conductive foam filler; wherein the conductive foam filler accounts for 1% to 50% of the weight percentage of the matrix resin, and the matrix resin has a T... g The temperature range is -30 to 35°C, preferably 0 to 33°C, and more preferably 15 to 30°C.

[0007] Furthermore, the matrix resin is selected from cured epoxy resin, phenolic resin, urea-formaldehyde resin, alkyd resin, urethane, furan resin, allyl resin, or a combination thereof.

[0008] Furthermore, the matrix resin is preferably an epoxy glass, which includes a thermosetting resin prepared by reacting an epoxy component selected from glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, phenolic epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, or a combination thereof with a curing agent.

[0009] Furthermore, the epoxy component is selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, and alicyclic glycidyl ester multifunctional epoxy resin, preferably from 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester (TDE-85) and 1,4-cyclohexanediethanol diglycidyl ether.

[0010] Furthermore, the curing agent is selected from one or more of alkane diacids, acrylonitrile compounds and adducts of amine compounds, and polyamine compounds.

[0011] The nitrile compound can be one or more of acrylonitrile, 3-butenonitrile, 2-pentenonitrile, 3-pentenonitrile and 4-pentenonitrile, preferably acrylonitrile; while the amine compound can be one or more of diethylenetriamine, triethylenetetramine, polyetheramine, 1,3-cyclohexyldimethylamine, isophorone diamine, 4,4'-diaminodicyclohexylmethane, diaminomethylcyclohexylmethane and diphenylmethane diamine, preferably isophorone diamine.

[0012] Furthermore, the conductive foam filler is carbonized plastic foam or sponge, preferably selected from one or more of polyolefin foaming materials, polyester foaming materials, polyurethane foaming materials, polystyrene foaming materials, polyether foam, starch plastic, phenolic foam, melamine sponge, and rubber cotton.

[0013] Furthermore, an elastomer layer is also included between the interface of the matrix resin and the conductive foam filler.

[0014] Furthermore, the elastomer is selected from one or more of silicone rubber, fluororubber, polyurethane, ethylene propylene rubber, nitrile rubber, chloroprene rubber, polyisobutylene, polysulfide rubber, and natural rubber.

[0015] The thickness of the aforementioned elastomer layer is preferably controlled to not exceed 1 mm.

[0016] In this invention, the curing of the matrix resin can also be achieved by using curing accelerators, regulators, and other additives to change and adjust the effect parameters.

[0017] Furthermore, the promoter may be selected from one or a mixture of several of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole and 2-phenyl-4-methylimidazole.

[0018] This invention, through the control of raw materials (including material type, epoxy equivalent, functionality, etc.) and the curing process (including curing agent, curing condition parameters, etc.), produces composite materials with glass transition temperature characteristics suitable for specific application scenarios, thus obtaining functional materials that meet the requirements of temperature-controlled flexible piezoresistive sensing. The products provided by this invention are particularly suitable for use at room temperature or ambient temperature.

[0019] The temperature-controlled flexible piezoresistive sensing material provided by this invention, when subjected to external pressure, causes the network skeleton in the conductive foam filler to break, disrupting the conductive path and increasing resistance. When the external force is removed, the conductive skeleton reconnects, and the electrical signal returns to its initial level, thus enabling sensing activity. The inclusion of an elastomer further optimizes the reconnection process of the conductive skeleton.

[0020] As a second aspect of the present invention, a method for preparing the temperature-controlled flexible piezoresistive sensing material as described above is provided, namely, immersing conductive foam filler in a precursor of a matrix resin, degassing and curing to obtain the temperature-controlled flexible piezoresistive sensing material.

[0021] Furthermore, the precursor of the matrix resin includes monomers, oligomers, and solutions.

[0022] In this invention, the precursor of the matrix resin may also include additives such as diluents and defoamers.

[0023] Further, the diluent is preferably selected from one or more of butyl glycidyl ether, benzyl glycidyl ether, butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,2-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycidyl ethers with C12-C14 alkyl groups in their molecular backbone, benzyl alcohol, phenethyl alcohol, nonylphenol, propylene carbonate, trimethylolpropane triacrylate, diisopropanol methyl ether, toluene, and xylene.

[0024] Furthermore, the defoamer is preferably one or more selected from polyacrylates and modified silicones. As an example, the defoamer may specifically be one or more of BYK066N, BYKA530, BYK141, and BYK354 manufactured by BYK Chemicals.

[0025] As a preferred embodiment, the above preparation method further includes the step of applying the elastomer to the surface of the conductive foam by an impregnation-drying method.

[0026] The temperature-controlled flexible piezoresistive sensing material prepared by the above method of the present invention can operate at temperatures below T0. g At this temperature, the matrix resin exhibits high compressive strength, remains in a rigid state, and has poor sensitivity, only 1.21 × 10⁻⁶. -4 kPa -1 However, it has a wide pressure detection range, with relatively small compression deformation within the sensing range. Upon heating, the matrix resin undergoes a glass transition, resulting in a significant decrease in its mechanical properties and substantial stress relaxation, making it more elastic. When the pressure is released, this temperature-controlled flexible piezoresistive sensing material can quickly return to its initial level, exhibiting better deformation capacity in a relaxed state at high temperatures, and increasing its sensitivity to 3.95 × 10⁻⁶. -4 kPa -1 It can detect minute compression deformations. Therefore, the aforementioned temperature-controlled flexible piezoresistive sensing material possesses the following physical properties:

[0027] 1) Wide pressure detection range: Dynamic force detection over a wide range of 5kPa to 1500kPa can be achieved at frequencies of 0.1Hz to 5Hz;

[0028] 2) Sensitivity: Maintains good sensitivity within the frequency range of 0.1Hz to 5Hz, with a value of 1.65×10⁻⁶. -4 kPa -1 ~8.71×10 -4 kPa -1 ;

[0029] 3) Fast response speed, up to approximately 70ms;

[0030] 4) It has good stability and can be used continuously and stably for up to 1000 times.

[0031] As a third aspect of the present invention, an application of the temperature-controlled flexible piezoresistive sensing material as described above is provided, that is, the temperature-controlled flexible piezoresistive sensing material is used as a component of intelligent, wearable, life monitoring or motion monitoring devices.

[0032] The temperature-controlled flexible piezoresistive sensing material provided by the present invention has good thermal conductivity and can soften under the applied voltage (0V~15V), thereby better realizing the function of a heater that fits the skin and can be applied to practical applications such as wearable electric drive heaters. Attached Figure Description

[0033] The above and other aspects, features, and advantages of embodiments of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 This is a schematic diagram of the preparation process of the temperature-controlled flexible piezoresistive sensing material according to an embodiment of the present invention;

[0035] Figure 2 These are electron microscope images of a temperature-controlled flexible piezoresistive sensing material provided according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram illustrating the working principle of the temperature-controlled flexible piezoresistive sensing material provided according to an embodiment of the present invention;

[0037] Figure 4 These are mechanical performance test data of the composite sensor provided according to an embodiment of the present invention;

[0038] Among them, Figure 4 The corresponding conditions are: a: 23℃, b: 40℃, c: 60℃, strain rate is 0.1mm / s; f: 10V; g: 5V, h: 10V, i: 15V;

[0039] Figures 5-7 These are the sensing performance test data of the composite sensor provided according to an embodiment of the present invention;

[0040] Among them, Figure 5 In this case, the strain rate is 1 mm / min.

[0041] exist Figure 6 In the given conditions, a: 100 kPa, b: 250 kPa, c: 500 kPa, d: 1500 kPa; e: 5 kPa, f: 10 kPa, g: 100 kPa, h: 500 kPa; i: 5 kPa, j: 10 kPa, k: 100 kPa, l: 500 kPa; m: 5 kPa, n: 10 kPa, o: 100 kPa, p: 500 kPa;

[0042] exist Figure 7 The corresponding conditions are as follows: a: 5 kPa, 23℃; b: 10 kPa, 23℃; c: 1000 kPa, 23℃; d: 250 kPa, 40℃; e: 1000 kPa, 40℃; f: 1000 kPa, 60℃; g: 5 kPa, 10V; h: 10 kPa, 10V; i: 100 kPa, 10V; j: 500 kPa, 10V; k: 1000 kPa, 10V; l: 1000 kPa, 15V.

[0043] Figure 8 These are response time test data of a composite sensor provided according to an embodiment of the present invention;

[0044] exist Figure 8 The corresponding conditions are: a: 23℃; b: 40℃; c: 60℃; d: 10V; e: 15V;

[0045] Figures 9-10 These are cycle performance test data of the composite sensor provided according to an embodiment of the present invention;

[0046] exist Figure 9 The corresponding conditions are: a: 100kPa, 23℃; b: 1000kPa, 23℃; c: 100kPa, 40℃; d: 1000kPa, 40℃; e: 100kPa, 10V; f: 1000kPa, 10V; g: 100kPa, 15V; h: 1000kPa, 15V.

[0047] Figure 11 These are application demonstration test results of the composite sensor provided according to embodiments of the present invention;

[0048] Figure 12 The results are performance test results of the sensing materials according to the comparative example of the present invention. Detailed Implementation

[0049] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in many different forms, and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the various embodiments of the invention and various modifications suitable for particular intended applications.

[0050] Example 1

[0051] This embodiment provides a CMS / silicone rubber / epoxy resin composite material, wherein CMS (melamine carbide) is used as a conductive foam filler, filling the space between the epoxy resin matrix resin, and silicone rubber is used as an elastomer layer material, located between the epoxy resin and CMS.

[0052] Furthermore, the epoxy resin is a TDE-85 type resin (4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester) and adipic acid prepared by TDE-85 type resin and adipic acid. g It is a thermosetting resin with a temperature of 30.1℃. Its properties are below and above T... g At the specified temperatures, the material's compressive modulus exhibits performance levels of 17 mPa and 8 mPa, respectively.

[0053] CMS is obtained by carbonizing melamine sponge.

[0054] The CMS / silicone rubber / epoxy resin composite material described in this embodiment was prepared using the following method:

[0055] Materials: Silicone rubber was supplied by Smooth-On, Inc.; melamine sponge was purchased from Kanghao Polymer Materials Technology Co., Ltd.; TDE-85 resin was purchased from Tianjin Jingdong Chemical Composite Materials Co., Ltd.; adipic acid was purchased from Shanghai Meiya Chemical Technology Co., Ltd.

[0056] Preparation method (e.g.) Figure 1 As shown):

[0057] First, melamine sponge was carbonized at 1000°C for 2 hours in a N2 atmosphere to obtain CMS.

[0058] Then, CMS was immersed in an organosilicon ether solution (10wt%) and dried at 60°C for 2 hours to obtain porous CMS / silicone rubber foam.

[0059] To increase the silicone content, the coating process can be repeated multiple times.

[0060] Finally, a mixture of TDE-85 and adipic acid with an epoxy group to carboxyl group molar ratio of 1:1 was injected into the above CMS / silicone rubber foam with the assistance of a vacuum pump. After vacuum degassing, it was continuously cured at 90°C for 2 hours and at 150°C for 6 hours to obtain the final product.

[0061] When using CMS / silicone rubber / epoxy resin composite material as a sensor, the process also includes the step of forming electrodes at both ends by coating with silver paste, thereby obtaining a CMS / silicone rubber / epoxy resin composite sensor.

[0062] Example 2

[0063] The carbonized phenolic foam / polyurethane rubber / epoxy resin composite material provided in this embodiment is prepared using the following method:

[0064] Materials: Phenolic foam material was purchased from Shandong Shengquan Chemical Co., Ltd.; MDI and polyether were provided by Yantai Wanhua; bisphenol A epoxy resin (E-51) was purchased from Nantong Xingchen Synthetic Materials Co., Ltd.; sebacic acid (SA) was purchased from Nantong Ruida Electronic Materials Co., Ltd.

[0065] Preparation method:

[0066] First, the phenolic foam material is washed in ethanol to remove impurities, dried, and then placed in a tube furnace and carbonized at 900°C for 2 hours in a He atmosphere to obtain carbonized phenolic foam.

[0067] Then, the carbonized phenolic foam is immersed in a mixture of MDI and polyether, and then reacted at 70°C to obtain carbonized phenolic foam / polyurethane rubber.

[0068] Finally, a mixture of E-51 and sebacic acid with an epoxy group to carboxyl group molar ratio of 3:1 is injected into the above-mentioned carbonized phenolic foam / polyurethane rubber with the assistance of a vacuum pump. After vacuum degassing, it is cured at 140°C for 2 hours to obtain the final product.

[0069] Example 3

[0070] The CMS / silicone rubber / epoxy resin composite material described in this embodiment was prepared using the following method:

[0071] Materials: Natural latex was provided by Shanghai Liankangming Chemical Co., Ltd.; starch-based plastic foam material was purchased commercially; TDE-85 resin was purchased from Tianjin Jingdong Chemical Composite Materials Co., Ltd.; adipic acid was purchased from Shanghai Meiya Chemical Technology Co., Ltd.

[0072] Preparation method:

[0073] First, the starch-based plastic foam is washed in ethanol to remove impurities, dried, and then placed in a tube furnace. It is then carbonized at 900°C for 2 hours in a N2 atmosphere to obtain carbonized starch-based plastic.

[0074] Then, the carbonized starch plastic is immersed in natural rubber latex, a vulcanizing agent is added, and after vacuum degassing, it is cured at 70°C to obtain carbonized starch plastic / natural rubber.

[0075] Finally, a mixture of TDE-85 and adipic acid with an epoxy group to carboxyl group molar ratio of 1:1 is injected into the above carbonized starch plastic / natural rubber with the assistance of a vacuum pump. After vacuum degassing, it is continuously cured at 90°C for 2 hours and at 150°C for 6 hours to obtain the final product.

[0076] Example 4

[0077] The carbonized rubber cotton / epoxy resin composite material provided in this embodiment is prepared using the following method:

[0078] First, the rubber cotton is washed in ethanol to remove impurities, dried, and then placed in a tube furnace and carbonized at 300°C for 2 hours in a He atmosphere to obtain carbonized rubber cotton.

[0079] Then, bisphenol A type epoxy resin (solid, epoxy equivalent of 7700 g / eq to 870 g / eq) is heated to 100°C to 150°C, and then stirred evenly with a mixture of 2-methylimidazole and dicyandiamide (mass ratio of 1:5) to obtain epoxy resin precursor.

[0080] Finally, the epoxy resin precursor is injected into the carbonized rubber cotton with the assistance of a vacuum pump, and cured at room temperature to obtain the final product.

[0081] Example 5

[0082] The carbonized polyurethane foam / chloroprene rubber / epoxy resin composite material provided in this embodiment is prepared by the following method:

[0083] First, the polyurethane foam was washed in ethanol to remove impurities, dried, and then carbonized at 180°C for 2 hours in a He atmosphere to obtain carbonized polyurethane foam.

[0084] Then, the dimer acid modified epoxy resin (viscosity 40000cP~90000cP, epoxy equivalent 380g / eq~460g / eq) and bisphenol F type epoxy resin (viscosity 3400cP~4200cP, epoxy equivalent 167g / eq~174g / eq) are heated to 100℃~150℃, and then stirred evenly with a mixture of imidazole accelerator (imidazole latent curing agent) and dicyandiamide (mass ratio of 1:5.5) to obtain epoxy resin precursor.

[0085] Finally, the epoxy resin precursor is injected into the carbonized polyurethane foam with the assistance of a vacuum pump, and cured at room temperature to obtain the final product.

[0086] Example 6

[0087] The carbonized phenolic foam / acrylic resin composite material provided in this embodiment was prepared using the following method:

[0088] First, the phenolic foam material is washed in ethanol to remove impurities, dried, and then placed in a tube furnace and carbonized at 900°C for 2 hours in a He atmosphere to obtain carbonized phenolic foam.

[0089] Then, butyl acrylate, ethyl acrylate, acrylonitrile, glycidyl methacrylate and water are mixed, N2 is replaced, and then heated to 55°C to obtain the resin precursor.

[0090] Finally, the mixture of the above resin precursor and diethylene ethyl peroxybicarbonate is injected into the above carbonized phenolic foam with the assistance of a vacuum pump, and cured at the above temperature for 4 hours to obtain the final product.

[0091] Product Testing: All optical photographs were recorded using a digital camera (Canon 850D). The morphology of the conductive foam filler, matrix resin, conductive foam filler / elastomer layer, and temperature-controlled flexible piezoresistive sensing material was obtained using a field emission scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy (FESEM, Phenom XL). The conductivity of the conductive foam filler and temperature-controlled flexible piezoresistive sensing material was measured using a digital multimeter (VICTOR 86E) via a dual-probe method.

[0092] Glass transition temperature (T) gA matrix resin composition was prepared by casting in a mold with a length, width, and thickness of 80 mm, 10 mm, and 4 mm, respectively. After curing, demolding, and surface polishing, a 4 mm thick sample was obtained. The storage modulus as a function of temperature was measured using a TA Q800 dynamic mechanical thermal analyzer at a heating rate of 2 °C / min and a frequency of 1 Hz. The inflection point where the slope of the curve changed significantly was taken as T. g .

[0093] The mechanical properties of the temperature-controlled flexible piezoresistive sensing material were characterized by a universal testing machine (SHIMADZUAGS-X), and the resistance was recorded by a digital multimeter (KEYSIGHT 34465A).

[0094] The sensing performance is represented by the relative change in resistance (RCR = (R - R0) / R0), where R and R0 are the resistances of the temperature-controlled flexible piezoresistive sensing material under conditions of presence and absence of external stimulation, respectively. Sensitivity is defined as S = RCR / ΔP, where P is the applied pressure.

[0095] FT-IR spectra were recorded on a Thermo Scientific Nicolet iS50 FT-IR spectrometer. Differential scanning calorimetry (DSC) was performed on a NETZSCH DSC 214 polyma, specifically controlled at a scan rate of 10 °C / min from 0 °C to 100 °C in a N2 atmosphere for CMS / silicone rubber / epoxy resin type temperature-controlled flexible piezoresistive sensing materials.

[0096] Figure 2 This illustrates CMS (CMS) in CMS / silicone rubber / epoxy resin type composites. Figure 2 a) CMS / silicone rubber after 1 to 3 dip coating cycles (in order of...) Figure 2 b~d), CMS / epoxy resin ( Figure 2 e), and CMS / silicone rubber / epoxy resin under 1 to 3 dip coating cycles (in order of... Figure 2 Electron micrographs of f~h). Figure 2 It can be seen that increasing the dip-coating cycle leads to increased void blockage, which is detrimental to the injection of high-viscosity TDE-85 / adipic acid mixture. Figure 2 a~d); such as Figure 2 As shown in e-h, more voids were observed in the CMS / silicone rubber / epoxy resin composite material with 3 dip-coating cycles, while fewer voids were observed in the CMS / silicone rubber / epoxy resin composite material with fewer dip-coating cycles. However, the elasticity of this CMS / silicone rubber / epoxy resin composite material increased with the number of dip-coating cycles. To achieve a balance between mechanical adjustability and elasticity, the aforementioned CMS / silicone rubber / epoxy resin composite sensor was prepared using 2 dip-coating cycles.

[0097] The working principle of CMS / silicone rubber / epoxy resin composite materials is as follows: Figure 3 As shown. The fragile but conductive CMS deforms under external loading, leading to an increase in resistance. Simultaneously, the elastic silicone rubber pulls the CMS back to its original position after the external force is removed, resulting in immediate recovery of resistance. Furthermore, the high toughness of epoxy resin at 23°C provides a higher upper limit for the detection of CMS / silicone rubber / epoxy resin composites. Increasing the temperature to T... g This process induces a mechanical transformation of the epoxy resin from phase I (tough state) to phase II (soft state). As a result, the compressive modulus decreases sharply at 40°C and 60°C, leading to a significant increase in the sensitivity and detection limit of the temperature-controlled flexible piezoresistive sensing material. Due to its high conductivity, when a voltage is applied, the resulting heat raises the local temperature through an electrothermal effect, further reducing the compressive modulus and allowing the temperature-controlled flexible piezoresistive sensing material to exhibit a sensitivity enhancement effect similar to that caused by temperature changes.

[0098] The mechanical property test results of the CMS / silicone rubber / epoxy resin composite sensor are as follows: Figure 4 As shown. At 23℃, compressive stresses of 0.24 MPa, 1.07 MPa, 2.11 MPa, and 4.36 MPa were obtained at strains of 10%, 20%, 30%, and 40%, respectively. Figure 4 a). However, load-unload cycles showed that the CMS / silicone rubber / epoxy resin composite exhibited limited elasticity at high compressive strain (i.e., 40%). In contrast, when the temperature exceeded the To of the epoxy resin... g At that time, elasticity is significantly improved, such as Figure 4 In samples b to c, there is no significant reduction in mechanical stress at 40℃ and 60℃. It is noteworthy that the compressive stresses at 40℃ with strains of 10%, 20%, 30%, and 40% (124 kPa, 339 kPa, 614 kPa, and 1065 kPa respectively) are significantly lower than the corresponding values ​​at 23℃, indicating a decrease in the elastic modulus of this CMS / silicone rubber / epoxy resin composite material at high temperatures. When the temperature is further increased to 60℃, the rate of decrease in compressive stress during cyclic loading slows down.

[0099] Furthermore, due to the use of highly conductive CMS, the temperature of this CMS / silicone rubber / epoxy resin composite material can be induced by applying a voltage. For example... Figure 4 As shown in Figure d, temperatures of 28.5℃, 47.1℃, and 73.6℃ were obtained at voltages of 5V, 10V, and 15V, respectively, compared with... Figure 4 The values ​​in the mid-infrared image are in excellent agreement. Meanwhile, cyclic voltage testing confirms the reliable electrothermal behavior of the CMS / silicone rubber / epoxy resin composite material. Figure 4f) By applying a voltage, the CMS / silicone rubber / epoxy resin composite material can be made to have similar temperature-mechanical adjustability. For example... Figure 4 As shown in g~i, compressive stresses of 1.38 MPa, 0.60 MPa, and 0.48 MPa were obtained at 30% strain under voltages of 5V, 10V, and 15V, respectively, which is consistent with the mechanical behavior at high temperatures. Load-unloading tests at 5V, 10V, and 15V showed that the CMS / silicone rubber / epoxy resin composite material exhibited excellent elasticity similar to that at 40℃ and 60℃. These results indicate that the mechanical properties of this CMS / silicone rubber / epoxy resin composite material can be manipulated by changing the temperature or voltage.

[0100] Figure 5 The sensitivity test results of the above-mentioned CMS / silicone rubber / epoxy resin composite sensor under different conditions are shown. It can be seen that the sensitivity of the CMS / silicone rubber / epoxy resin composite material increases significantly with increasing temperature. Specifically, at 23℃, a sensitivity of 1.65 × 10⁻⁶ was obtained within a pressure range of 0–5 kPa. -4 kPa -1 The sensitivity at 40℃ and 60℃ is increased to 4.85×10. -4 kPa -1 and 5.87×10 -4 kPa -1 These improvements of 194% and 256% respectively enable this CMS / silicone rubber / epoxy resin composite material to monitor stimuli at lower pressure levels, such as respiration and pulse. A similar effect can be achieved by applying voltage. Figure 5 As shown in b, within a pressure range of 0–5 kPa and a voltage range of 5 V–15 V, the corresponding sensitivity ranges from 2.51 × 10⁻⁶. -4 kPa -1 Increased to 8.71×10 -4 kPa -1 Compared to 23℃ without applied voltage, the improvements were 52%, 254%, and 428%, respectively. In summary, the CMS / silicone rubber / epoxy resin composite material at 1.65 × 10⁻⁶... - 4 kPa -1 ~8.71×10 -4 kPa -1 It maintains good sensitivity within a certain range, providing a wide pressure detection range suitable for various motion recordings.

[0101] Since the motion of humans or robots mainly occurs in the frequency range of 0.01 Hz to 5 Hz, the effective detection range of CMS / silicone rubber / epoxy resin composite materials at frequencies of 0.1 Hz, 1 Hz and 5 Hz was evaluated. Figure 6and Figure 7 The test results of the above-mentioned CMS / silicone rubber / epoxy resin composite material under different pressure ranges are shown.

[0102] Due to limited sensitivity at 23°C, the response of CMS / silicone rubber / epoxy resin composite materials to 5kPa–100kPa is unreliable, especially at high frequencies, as evidenced by irregularities or multiple peaks in the RCR mode at 5Hz. Figure 6 a, Figure 7 (a~b). However, when the external stress increases to 250kPa~1500kPa, accurate cyclic RCR modes are obtained at 0.1Hz, 1Hz and 5Hz ( Figure 6 b~d、 Figure 7 c) indicates a high upper limit for pressure detection at 23°C. Sensing performance significantly improves at lower pressure levels when the temperature rises to 40°C. Reliable RCR responses for 10 kPa and 100 kPa were obtained in the frequency range of 0.1 Hz to 5 Hz. Figure 6 e~g) indicates that the detection limit at 40℃ is 10 kPa. Simultaneously, accurate RCR responses can also be observed at cyclic pressures of 250 kPa and 500 kPa. Figure 6 h、 Figure 7 d). However, further increasing the pressure to 1000 kPa produces an irregular RCR response ( Figure 7 e) indicates that the upper limit of detection for the CMS / silicone rubber / epoxy resin composite material at 40℃ is less than 1000 kPa. When the temperature is increased to 60℃, the CMS / silicone rubber / epoxy resin composite material exhibits a similar upper limit of detection of less than 1000 kPa, but the improved lower limit of detection is 5 kPa. Figure 6 i~l、 Figure 7 f).

[0103] Simultaneously, applying 10V and 15V also provided improved detection limits for CMS / silicone rubber / epoxy resin composites. At frequencies of 0.1Hz to 5Hz, and voltages of 10V and 15V, accurate RCR response modes were observed for 10kPa to 500kPa and 5kPa to 500kPa, respectively, while the response to 1000kPa was poor. Figure 6 m~p、 Figure 7 g~k).

[0104] The above results indicate that, within the frequency range of 0.1 Hz to 5 Hz, the upper limit of pressure detection for this CMS / silicone rubber / epoxy resin composite material at 23°C is 1500 kPa, while the lower limit of pressure detection at 60°C or a voltage above 15 V is as low as 5 kPa. In other words, the CMS / silicone rubber / epoxy resin composite material exhibits a wide detection range from 5 kPa to 1500 kPa with the aid of temperature or voltage.

[0105] Figure 8 The response time test results of the above-mentioned CMS / silicone rubber / epoxy resin composite sensor under different temperature / voltage stimuli are shown. It achieved response times of 125ms, 82ms, and 71ms at 23℃, 40℃, and 60℃, respectively, while at 10V and 15V, the response times were 78ms and 69ms, respectively.

[0106] Figure 9 and Figure 10 The cycling stability of the aforementioned CMS / silicone rubber / epoxy resin composite sensor is shown. After 1000 cycles at 23°C, it exhibits poor sensing performance at 100 kPa. Figure 9 (irregular RCR patterns can be displayed in a); however, in Figure 10 a and Figure 9 Precise cyclic responses to 500 kPa and 1000 kPa were observed in b, revealing its reliable long-term service under ultra-high pressure stimulation. Similar reliable sensing performance was observed at 100 kPa and 500 kPa cyclic pressures, exceeding 1000 cycles, when temperatures were increased to 40°C and 60°C or voltages of 10V and 15V were applied; however, the response at 1000 kPa cyclic pressure was poor. Figure 9 ch、 Figure 10 be).

[0107] Application demonstration test results of the CMS / silicone rubber / epoxy resin composite sensor are as follows: Figure 11 As shown. Due to its low thermal conductivity (0.133 W / mK), although the temperature of human skin is approximately 36°C, the temperature of this CMS / silicone rubber / epoxy resin composite sensor when applied to the human chest is 23°C. The results indicate that a voltage of 5V heats it to 28.5°C, enabling it to record human respiration. Figure 11 As shown in Figure a, normal breathing and fluctuating breathing can be distinguished by comparing RCR peak values; moreover, the respiratory rate can be obtained by counting the peak values. This is because the RCR peak value is the same as the step count (…). Figure 11(b) It can also be attached to the sole of the foot to provide real-time response to walking. Simultaneously, applying 10V increases its temperature to 47.1°C, thus the increased sensitivity at higher temperatures or voltages leads to an increase in the RCR peak. This CMS / silicone rubber / epoxy composite sensor can also be used to monitor finger movements by attaching it to the finger. Figure 11 As shown in Figure c, the increase or decrease in the RCR value indicates the action of pressing and releasing the spray bottle button. Furthermore, this CMS / silicone rubber / epoxy resin composite sensor can monitor the movement of lifting the disc by attaching it to a glove. Figure 11 As shown in Figure d, when a 2.5 kg iron disc is lifted and a compressive stress exceeding 100 kPa is generated, RCR values ​​of 4.8%, 7.8%, and 9.4% are obtained at 23℃, 40℃, and 60℃, respectively. Further increasing the weight of the iron disc by 2.5 kg produces RCR values ​​of 11.6%, 18.1%, and 23.0% at 23℃, 40℃, and 60℃, respectively. Figure 6 and Figure 7 The results are consistent with those in the previous section.

[0108] Robotic arms are of great importance in military, industrial production, and healthcare, therefore their movement must be monitored to control them. For this purpose, the aforementioned CMS / silicone rubber / epoxy resin composite sensor is mounted on the robotic arm's mounting device to monitor lifting conditions. Figure 11 e). Compared to the slight change in RCR when loaded to 20g at 23°C, the RCR values ​​observed at 40°C and 60°C were 1.9% and 2.77%, respectively, indicating improved sensitivity and a lower detection limit at increasing temperatures. Further stepwise increases in weight to 1000g showed similar trends in RCR at 23°C, 40°C, and 60°C. Figure 11 f shows the real-time response of the CMS / silicone rubber / epoxy resin composite sensor as a car passes by at different temperatures. Accurate monitoring of additional loads from 0 to 7.5 kg is possible across the entire temperature range; however, as the load increases from 7.5 kg to 10 kg, the increase in RCR at 40°C and 60°C decreases significantly. In contrast, the CMS / silicone rubber / epoxy resin composite sensor maintains a stable increase in RCR at 23°C, indicating a higher detection upper limit at 23°C. The above application demonstration test results demonstrate that the aforementioned CMS / silicone rubber / epoxy resin composite material can monitor motion from low to ultra-high pressure with the aid of temperature or voltage, and can be used as a component in devices including wearable devices, life monitoring, or motion monitoring devices.

[0109] Although the sensing performance of the temperature-controlled flexible piezoresistive sensing material provided by the present invention is due to the specific T0 of its matrix resin. gHowever, the combination of the matrix resin and the conductive foam filler is extremely important for achieving its performance and application. Therefore, the following comparative experiments were conducted.

[0110] Comparative Example

[0111] In this comparative example, only the aforementioned T is used. g Using epoxy resin at 30.1℃ as the sensing material, its sensing performance was tested, such as... Figure 12 As shown. Although it obtained compressive moduli of 42.0 MPa, 20.9 MPa and 15.9 MPa at 30% strain at 23℃, 40℃ and 60℃ respectively ( Figure 12 a); However, the sharp drop in compressive stress during the load-unload test indicates that the epoxy resin has poor elasticity. Figure 12 b), therefore it is not suitable for direct use as a sensor.

[0112] Although the invention has been shown and described with reference to specific embodiments, those skilled in the art will understand that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the claims and their equivalents.

Claims

1. A temperature-controlled flexible piezoresistive sensing material, characterized in that, It includes a matrix resin and a conductive foam filler, wherein the conductive foam filler accounts for 1% to 50% of the weight of the matrix resin, and the matrix resin has a T... g -30~35℃; The matrix resin is an epoxy-based glass, comprising a thermosetting resin prepared by reacting an epoxy component selected from glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, phenolic epoxy resin, biphenyl-type epoxy resin, naphthalene-type epoxy resin, or a combination thereof with a curing agent; the curing agent is selected from one or more of alkane diacids, acrylonitrile compounds, adducts of amine compounds, and polyamine compounds. The conductive foam filler is selected from carbonized plastic foam or sponge, and the plastic foam or sponge is selected from one or more of polyolefin foam materials, polyester foam materials, polyurethane foam materials, polystyrene foam materials, polyether foam, starch plastic foam, phenolic foam, melamine sponge, and rubber cotton.

2. The temperature-controlled flexible piezoresistive sensing material as described in claim 1, characterized in that, The T of the matrix resin g The temperature ranges from 0 to 33℃.

3. The temperature-controlled flexible piezoresistive sensing material as described in claim 2, characterized in that, The T of the matrix resin g The temperature is 15~30℃.

4. The temperature-controlled flexible piezoresistive sensing material as described in any one of claims 1 to 3, characterized in that, The epoxy component is selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, and alicyclic glycidyl ester multifunctional epoxy resin.

5. The temperature-controlled flexible piezoresistive sensing material as described in claim 4, characterized in that, The epoxy component is selected from 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester and 1,4-cyclohexanediethanol diglycidyl ether.

6. The temperature-controlled flexible piezoresistive sensing material as described in any one of claims 1 to 3, characterized in that, An elastomer layer is also included between the interface of the matrix resin and the conductive foam filler.

7. The temperature-controlled flexible piezoresistive sensing material as described in claim 6, characterized in that, The elastomer is selected from one or more of silicone rubber, fluororubber, polyurethane, ethylene propylene rubber, nitrile rubber, chloroprene rubber, polyisobutylene, polysulfide rubber, and natural rubber.

8. A method for preparing a temperature-controlled flexible piezoresistive sensing material as described in any one of claims 1 to 7, characterized in that, The conductive foam filler is immersed in the precursor of the matrix resin, defoamed, and cured to obtain the temperature-controlled flexible piezoresistive sensing material.

9. The preparation method according to claim 8, characterized in that, The precursors of the matrix resin include monomers, oligomers, and solutions.

10. The preparation method according to claim 8, characterized in that, It also includes the step of applying the elastomer to the surface of the conductive foam by an impregnation-drying method.

11. The use of a temperature-controlled flexible piezoresistive sensing material as described in any one of claims 1 to 7, characterized in that, The temperature-controlled flexible piezoresistive sensing material is used as a component in smart, wearable, life monitoring, or motion monitoring devices.

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