A wearable device for human EMG signal detection and its dedicated multifunctional elastic aerogel

Abstract

The application provides a wearable device for human EMG signal detection and a special multifunctional elastic aerogel thereof. The multifunctional elastic aerogel is prepared by reacting carboxymethyl cellulose (CMC), epoxidized natural rubber (ENR) and carboxylated multi-walled carbon nanotubes (cMWCNT) as raw materials. In the field of wearable devices, the sensor made based on the multifunctional characteristics of the aerogel can monitor the human motion state in real time, and provide accurate data for sports health management and rehabilitation medicine; in the aspect of stress recognition, through high-precision stress detection, the aerogel can be applied to robot tactile perception, intelligent insole and the like, and solves the problem that the prior art cannot realize high-precision stress recognition; in addition, the electromagnetic shielding and thermal insulation performance of the aerogel can also be used for electronic device shells, aerospace thermal insulation materials and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of intelligent sensing technology, and specifically relates to a wearable device for human EMG signal detection and a special multifunctional elastic aerogel thereof, wherein the multifunctional elastic aerogel is prepared by adsorbing carboxylated multi-walled carbon nanotubes based on crosslinking of carboxymethyl cellulose and epoxidized natural rubber, has high conductivity, electromagnetic interference shielding, thermal insulation and pressure-sensitive sensing properties, and can be used in the field of wearable sensors. BACKGROUND

[0002] The rapid development of wearable electronic devices and wireless communication technology has increased the demand for lightweight, flexible, high-performance electromagnetic interference (EMI) shielding materials and sensitive strain sensors for health monitoring and human-machine interfaces. Traditional metal shielding materials have the disadvantages of high density, poor flexibility, easy corrosion, etc., which limit their application in wearable devices [Liu, J., Yu, M.-Y., Yu, Z.-Z., & Nicolosi, V. (2023). Design and advanced manufacturing of electromagnetic interference shielding materials. Materials Today, 66, 245-272.]. In contrast, polymer-based nanocomposites, especially those containing conductive nanofillers such as carbon nanotubes, graphene and MXenes, have become promising alternative materials due to their adjustable electrical conductivity, mechanical flexibility and easy processability [Nan, Z., Wei, W., Lin, Z., Chang, J., & Hao, Y. (2023). Flexible Nanocomposite Conductors for Electromagnetic Interference Shielding. Nano-Micro Letters, 15(1)].

[0003] In the field of functional materials, the existing aerogel materials have obvious technical shortcomings: first, traditional aerogels usually only have single or a few functions, such as some aerogels can only achieve thermal insulation, and it is difficult to simultaneously meet the performance requirements of high electrical conductivity, high electromagnetic interference (EMI) shielding and pressure-sensitive sensing, and cannot be applied to complex scenes with high comprehensive requirements for materials. Second, the mechanical structure of most aerogels is unstable, and there is no effective cross-linking network construction method, resulting in low mechanical strength. When subjected to external force or environmental changes, the structure is prone to collapse or damage, the service life is short, and it is difficult to be used stably in actual working conditions. In the field of wearable sensors, the existing sensing materials also have shortcomings: on the one hand, the strain sensing sensitivity is low, and it is difficult to accurately capture small strain changes, which cannot meet the high-precision monitoring requirements; on the other hand, the cycle stability of the sensing unit is poor, and after several loading-unloading cycles, the performance significantly decays, affecting the long-term use reliability of the sensor. In addition, the stress recognition accuracy of the existing sensor is insufficient, the spatial resolution cannot reach millimeter level, and when monitoring multi-joint human motion, it cannot output stable current response, resulting in large monitoring data error, poor real-time performance, and difficulty in accurately perceiving the human motion state. SUMMARY

[0004] The present application aims at the problems existing in the prior art, and provides a wearable device for human EMG signal detection and a special multifunctional elastic aerogel thereof.

[0005] Through esterification reaction between carboxymethyl cellulose (CMC) and epoxidized natural rubber (ENR), a stable three-dimensional cross-linked network skeleton is constructed, which structurally enhances the mechanical strength and stability of the aerogel, so that it can withstand 1000 cycles of loading while maintaining stable performance. At the same time, by using the coupling reaction of carboxylated multi-walled carbon nanotubes (cMWCNT) with the aerogel and the freeze-drying process, the cMWCNT is uniformly fixed on the surface of the aerogel, which endows the aerogel with high electrical conductivity, stable EMI shielding performance (40 dB) and high-sensitivity pressure-sensitive sensing characteristics (strain coefficient = 2.56), realizing the integration of multiple functions.

[0006] The wearable device for human EMG signal detection provided by the present application comprises a multifunctional elastic aerogel.

[0007] The multifunctional elastic aerogel is prepared by reaction of carboxymethyl cellulose (CMC), epoxidized natural rubber (ENR) and carboxylated multi-walled carbon nanotubes (cMWCNT),

[0008] The carboxymethyl cellulose (CMC) and the epoxidized natural rubber (ENR) construct a three-dimensional cross-linked network skeleton through esterification reaction between the epoxy groups and the carboxyl groups, and the carboxylated multi-walled carbon nanotubes (cMWCNT) are adsorbed on the surface of the three-dimensional cross-linked network skeleton.

[0009] The multifunctional elastic aerogel is denoted as ENR / CMC-cMWCNT aerogel.

[0010] The carboxylated multi-walled carbon nanotubes (cMWCNT) are adsorbed on the surface of the three-dimensional cross-linked network skeleton through coupling reaction and freeze-drying.

[0011] In the multifunctional elastic aerogel, the mass ratio of the epoxidized natural rubber (ENR) to the carboxymethyl cellulose (CMC) is 10: (1-5).

[0012] The mass ratio of the carboxylated multi-walled carbon nanotubes (cMWCNT) to the carboxymethyl cellulose (CMC) is (1-5) : 10.

[0013] In the present application, the carboxymethyl cellulose (CMC) is added in the epoxidized natural rubber (ENR) according to the mass ratio (the ratio of ENR: CMC is 10:1, 10:2, 10:3, 10:4, 10:5) to prepare ENR / CMC1, ENR / CMC2, ENR / CMC3, ENR / CMC4 and ENR / CMC5 aerogels.

[0014] The carboxylated multi-walled carbon nanotubes (cMWCNT) are added based on the ENR / CMC3 aerogel obtained by optimizing the rebound performance, and the mass ratio is prepared according to the ratio of CMC: cMWCNT is 10:1, 10:2, 10:3, 10:4, 10:5 to prepare ENR / CMC-cMWCNT1, ENR / CMC-cMWCNT2, ENR / CMC-cMWCNT3, ENR / CMC-cMWCNT4 and ENR / CMC-cMWCNT5 aerogels.

[0015] Further, in the multifunctional elastic aerogel, ENR: CMC: cMWCNT = 100:30: (3-15) (mass ratio).

[0016] The present application also provides a method for preparing the multifunctional elastic aerogel.

[0017] The method for preparing the multifunctional elastic aerogel provided by the present application comprises the following steps:

[0018] 1) Preparation of carboxylated multi-walled carbon nanotubes (cMWCNT)

[0019] 2) Preparation of CMC-cMWCNT dispersion composite liquid

[0020] The cMWCNT powder is added to the CMC solution, the carboxyl group is activated after adding EDC, and then ethylenediamine is added for stirring to promote the coupling reaction of the carboxyl group of CMC and the carboxyl group of cMWCNT to form an amide bond. After the reaction is completed, the obtained mixture is centrifuged, and the product obtained by centrifugation is vacuum freeze-dried to obtain a CMC-cMWCNT dispersion composite liquid;

[0021] 3) Preparation of ENR / CMC-cMWCNT aerogel

[0022] The ENR emulsion is mixed with the CMC-cMWCNT dispersion composite liquid, and a homogeneous emulsion is obtained by stirring. The pH is adjusted to 9.0-10.0, an esterification reaction is carried out, the pH is adjusted to neutral after the reaction is completed, and freeze-drying is carried out to obtain an ENR / CMC-cMWCNT aerogel.

[0023] In the above method step 1), a strong oxidizing agent is used to oxidize the surface of MWCNT to obtain carboxylated carbon nanotubes (cMWCNT);

[0024] The strong oxidizing agent is a mixed solution of concentrated H2SO4 / HNO3 with a volume ratio of 3:1;

[0025] The ratio of MWCNT to strong oxidizing agent can be 1g:40mL;

[0026] The oxidation treatment is carried out under ultrasonic conditions; the frequency of the ultrasonic is 40kHz, the temperature is 60°C, and the ultrasonic treatment time is 6h.

[0027] In the above method step 2), the mass ratio of carboxylated multi-walled carbon nanotubes (cMWCNT) to carboxymethyl cellulose (CMC) is (1-5):10;

[0028] The carboxyl activating agent is specifically EDC;

[0029] The stirring is carried out at room temperature, and the stirring time can be 6-8h;

[0030] The stirring speed can be 500-600rpm;

[0031] The above method step 2) further includes the operation of adding ethylenediamine to block the unreacted active groups after the reaction is completed;

[0032] The centrifugation conditions can be 10000-12000rpm centrifugation for 10-15min to remove unreacted catalyst and by-products;

[0033] The freeze-drying condition can be: -40~ -50 DEG C, under the condition of vacuum degree 10~15Pa freeze-drying 36~48h.

[0034] In the above method step 3), the mass ratio of ENR in the ENR emulsion to CMC in the CMC-cMWCNT dispersion composite liquid is 10: (1-5) ;

[0035] The temperature of the esterification reaction is 40~60 DEG C, and the time is 4~8h;

[0036] The freeze-drying condition can be: -40~ -50 DEG C, under the condition of vacuum degree 10~15Pa freeze-drying 36~48h.

[0037] The above ENR / CMC-cMWCNT aerogel is used in the fields of wearable electronic devices, strain sensing and electromagnetic interference shielding.

[0038] Based on the multifunctional elastic aerogel, a sensing array and a signal acquisition circuit are designed, high-precision stress recognition with a spatial resolution of less than 1mm is realized, and the multifunctional aerogel is applied to a wearable sensor, so that stable and reliable current responses can be generated in the process of multi-joint human motion monitoring.

[0039] The application provides a novel ENR / CMC-cMWCNT aerogel, which is prepared by a casting ice process and has flexibility of ENR, dispersibility of CMC and conductivity of cMWCNT.

[0040] Compared with the prior art, the application has the following advantages:

[0041] Existing aerogel preparation often depends on petrochemical-based synthetic raw materials, such as petroleum-derived polymers, which not only consume non-renewable resources, but also easily produce pollution in the production process. However, the core raw material carboxymethyl cellulose (CMC) in the application is derived from natural cellulose, and the epoxidized natural rubber (ENR) is based on natural rubber modification, both of which belong to renewable resources, which reduces the dependence on fossil energy from the source and meets the global green and sustainable development trend. In terms of cost, some high-performance aerogels in the prior art need to use expensive special materials or rare additives, which has high preparation cost. The auxiliary reagents used in the application, such as sodium dodecyl sulfate (SDS) and citric acid, are common chemical products, which are low in price and easy to obtain; the multi-walled carbon nanotubes (MWCNT) can introduce carboxyl groups through simple mixed acid oxidation modification, without complex process and expensive equipment, which greatly reduces the raw material cost and preparation threshold, making large-scale industrial production possible, while the prior art is difficult to realize large-scale popularization and application due to high cost.

[0042] Traditional aerogel preparation processes often have complex procedures and harsh conditions, such as some requiring high temperature and high pressure environments, not only high energy consumption, but also extremely high requirements for equipment, limiting the production scale and efficiency. The preparation process of the present application integrates chemical modification, solution mixing, freeze drying and other technologies, with clear parameters and simple operation for each step. In the carboxylation modification of MWCNT, by accurately controlling the proportion of mixed acid, ultrasonic frequency and time, the surface carboxyl content can be precisely controlled; the ENR emulsion concentration uses a rotary evaporator, which can effectively control the solid content; the esterification reaction adjusts the amount of citric acid, pH value and reaction temperature to realize precise control of the crosslinking degree. The whole process does not require high temperature and high pressure, and each link is closely connected, with strong repeatability, which is not only suitable for laboratory small test, but also easy to scale up production. Compared with the prior art, the process is complex and difficult to accurately control the quality of the product, resulting in poor product consistency, while the present application significantly improves the production efficiency and product stability.

[0043] The present application also realizes the multifunctional integration and performance improvement of aerogel, as follows:

[0044] Mechanical properties: Most traditional aerogels have low mechanical strength and poor flexibility, and are easily damaged in structure when subjected to external force or environmental changes, which cannot meet the demand of complex working conditions. The esterification reaction of ENR and CMC forms a three-dimensional cross-linked network, which gives the aerogel good mechanical strength and flexibility, and the uniform dispersion of cMWCNT further enhances its tensile and compression resistance, which can still maintain stable performance after 1000 cycle loading tests, far exceeding traditional aerogels;

[0045] Conductive and sensing performance: existing aerogel materials that can be used for sensing either have poor conductivity or low strain sensing sensitivity, making it difficult to accurately monitor small deformations. In the present application, cMWCNT constructs a continuous conductive path in the aerogel, making the aerogel have high conductivity and a strain coefficient of 2.56, which can accurately capture small deformations and monitor human movement or external stress changes in real time and accurately, having a significant advantage in the sensor field;

[0046] Electromagnetic shielding and thermal insulation performance: existing aerogel materials are usually single-function, rarely having both electromagnetic shielding and thermal insulation performance. The present application uses the high conductivity and large specific surface area of cMWCNT to achieve a stable electromagnetic shielding performance of 40 dB; the unique porous structure is filled with air, effectively blocking heat conduction and convection, and has excellent thermal insulation performance. This multifunctional integration characteristic is difficult to achieve by existing technology.

[0047] The existing aerogel material has narrow application scenarios due to performance limitations, for example, the traditional aerogel can only be used in single heat or sound insulation field. The application widens the application field based on the multifunctional characteristics of the aerogel. In the field of wearable devices, the prepared sensor can monitor the human motion state in real time, and provide accurate data for sports health management and rehabilitation medicine. The existing wearable sensor has the problems of low precision and poor stability; in the stress recognition aspect, through high-precision stress detection, it can be applied to robot tactile perception, intelligent insole and the like, and solves the problem that the existing technology cannot realize high-precision stress recognition; in addition, the electromagnetic shielding and thermal insulation performance can also be used for electronic device shell, aerospace thermal insulation material and the like, fills the blank of the existing technology in the multifunctional integrated application, and creates significant economic and social benefits. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a process schematic diagram of the application.

[0049] Figure 2 is the appearance and SEM image of ENR, ENR / CMC and ENR / CMC-cMWCNT aerogel prepared in Example 1.

[0050] Figure 3 is the thermal insulation performance of different aerogels. Temperature-time curve of ENR, ENR / CMC3 and ENR / CMC3-cMWCNT3 aerogel (A); surface equilibrium temperature and temperature difference between aerogel and heating plate (B); infrared thermal image of ENR / CMC3 and ENR / CMC3-cMWCNT3 aerogel on 100℃ heating plate (C); temperature-time curve of ENR / CMC3-cMWCNT3 aerogel during cyclic heating and cooling on the heating plate (D); DSC curve of ENR / CMC3-cMWCNT3 aerogel (E); optical image of paper crane placed on ENR / CMC3-cMWCNT3 aerogel and burned with alcohol lamp (F).

[0051] Figure 4 is the strain recovery analysis of ENR / CMC aerogel with different MCM contents. Stress-strain curve of ENR / CMC aerogel with different CMC contents (A); stress-strain curve of ENR / CMC-cMWCNT aerogel with different cMWCNT contents (B); compression stress and hysteresis energy of cMWCNT aerogel (C); Young's modulus of ENR / CMC and ENR / CMC-cMWCNT aerogel (D); stress-strain curve of ENR / CMC3-cMWCNT3 aerogel at different strains (E); stress-strain curve of ENR / CMC3-cMWCNT3 aerogel at 70% strain for different times (F).

[0052] Figure 5 Piezoelectric properties of ENR / CMC-cMWCNT aerogel. Variation of luminance of light emitting diode under different pressure (A); variation of current of ENR / CMC-cMWCNT aerogel under 1-10% deformation (B); variation of current of ENR / CMC-cMWCNT aerogel under 10-50% deformation (C); sensitivity test of aerogel sensor in 0-1.6 kPa pressure range (D); variation of current of ENR / CMC-cMWCNT aerogel under different compression frequency (E); equivalent circuit model of aerogel compression variation (F); response time of aerogel under fast loading and unloading conditions (G).

[0053] Figure 6 Electromagnetic shielding properties of ENR / CMC-cMWCNT aerogel with different cMWCNT addition. Relationship between conductivity and resistance of aerogel with different cMWCNT addition level (A); electromagnetic path propagation mode diagram of ENR / CMC-cMWCNT aerogel (B); reflection shielding effectiveness (C), absorption shielding effectiveness (D) and total shielding effectiveness (E) of ENR / CMC-cMWCNT aerogel; comparison of different shielding effectiveness of ENR / CMC3-cMWCNT aerogel with different cMWCNT addition (F).

[0054] Figure 7 Detection of human skin signals by aerogel sensor. Relative current variation caused by throat sound (A); relative current variation caused by elbow bending (B); relative current variation caused by arm bending (C); relative current variation caused by neck bending when nodding (D); relative current variation caused by neck rotation when turning head (E); relative current variation caused by finger bending at different angles (F). DETAILED DESCRIPTION

[0055] The application will be further described in details below with specific embodiments. The examples provided below are only for illustrating the application, and are not intended to limit the scope of the application. The examples provided below can serve as a guide for further improvement by those skilled in the art, and do not constitute any limitation on the application.

[0056] The experimental methods in the following examples are all conventional methods, and are performed according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents and the like used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0057] Multi-walled carbon nanotubes (MWCNT) used in the following examples: diameter 10-20 nm, length 1-10 μm, used to prepare carboxylated carbon nanotubes (cMWCNT) to endow the aerogel with conductivity as conductive filler, amount 5 g, supplier example Nanjing Xianfeng Nanometer Material Technology Co., Ltd.

[0058] Concentrated sulfuric acid (H2SO4): AR grade, purity 98%, mixed with nitric acid to modify MWCNT for carboxylation, amount 150 mL, provided by National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0059] Concentrated nitric acid (HNO3): AR grade, purity 68%, mixed with sulfuric acid to modify MWCNT for carboxylation, amount 50 mL, supplier National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0060] Carboxymethyl cellulose (CMC): analytical pure, degree of substitution 0.6-0.8, part used to prepare a 3 wt% solution, part used to prepare ENR / CMC-MWCNT aerogel, amounts 3 g and 22 g respectively, obtained from Arlanz Reagent (Shanghai) Co., Ltd., and used to react with ENR to build a crosslinked network and couple with cMWCNT.

[0061] Epoxidized natural rubber (ENR) latex: initial solid content about 20%, after being concentrated to a 3 wt% emulsion, reacted with CMC to form a crosslinked network skeleton, amount appropriate, commercially available.

[0062] Coupling agent 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC): analytical pure, used to promote the reaction of CMC with the carboxyl group of cMWCNT, amount 0.5 g, supplied by Arlanz Reagent (Shanghai) Co., Ltd.

[0063] Ethylene diamine: AR grade, used to block unreacted active groups, amount 0.5 mL, available from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0064] Sodium dodecyl sulfate (SDS): AR grade, used as a dispersion stabilizer for ENR emulsion, amount 0.2% of the total mass of ENR emulsion, provided by National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0065] Citric acid: AR grade, used to catalyze the esterification reaction of ENR with other raw materials, amount 2 g, supplier National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0066] Sulfuric acid (H2SO4): AR grade, purity 98%, used to adjust the pH value of the esterification reaction system to 2.5-3.0, amount appropriate, supplied by National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0067] Sodium bicarbonate (NaHCO3): AR grade, used to terminate esterification reaction and adjust the pH of the system to neutral, used in appropriate amount, available from Sinoreagent Co., Ltd.

[0068] Deionized water: used as solvent and washing water, made in the laboratory.

[0069] Equipment and tools

[0070] Ultrasonic cleaner: model KQ-500DE, power 500W, frequency 40kHz, used for ultrasonic treatment during MWCNTs carboxylation modification, 1 unit, brand example Kunshan Sumet Ultrasonic Instrument Co., Ltd.

[0071] Centrifuge: model TGL-16C, maximum speed 16000 rpm, used for centrifugal washing after MWCNT modification and CMC-cMWCNT dispersion treatment, 1 unit, produced by Shanghai Anting Scientific Instrument Factory.

[0072] Vacuum drying oven: model DZF-6020, temperature range RT+10-250℃, vacuum degree-0.1MPa, used for cMWCNT drying to remove water, 1 unit, brand Shanghai Yiheng Scientific Instrument Co., Ltd.

[0073] Rotary evaporator: model RE-52AA, water bath temperature range room temperature~99℃, vacuum degree-0.098MPa, used for ENR latex concentration, 1 unit, produced by Shanghai Alex Science Instrument Factory.

[0074] Magnetic stirrer: model 85-2, speed range 50-2000rpm, 2 units, used for solution stirring and reaction process mixing, brand example Changzhou Guohua Electrical Appliance Co., Ltd.

[0075] Digital constant temperature water bath: model HH-4, temperature range RT~100℃, accuracy ±0.5℃, used for esterification reaction temperature control and solution heating, 1 unit, produced by Changzhou Guohua Electrical Appliance Co., Ltd.

[0076] Freeze dryer: model FD-1A-50, cold trap temperature-50℃, vacuum degree 10Pa, used for freeze drying during aerogel preparation, 1 unit, brand Beijing Boyikang Experimental Instrument Co., Ltd.

[0077] pH meter: model PHS-3C, accuracy ±0.01pH, used for solution pH measurement and adjustment, 1 unit, produced by Shanghai Rayleigh Instrument Factory.

[0078] Electronic balance: model FA2004B, accuracy 0.1mg, used for solid reagent weighing, 1 unit, brand Shanghai Precision Scientific Instrument Co., Ltd.

[0079] Graduated cylinder: specifications 50 mL, 100 mL, 500 mL, used for liquid volume measurement, brand example is Shuniu Glass Instrument Factory.

[0080] Beaker: specifications 100 mL, 250 mL, 500 mL, used as solution preparation and reaction container, produced by Shuniu Glass Instrument Factory.

[0081] Glass rod: different specifications, used for stirring and drainage, ordinary glass instrument.

[0082] Pipette: specifications 100-1000 μL, 1-5 mL, each 1, used for accurate pipetting, brand example is Dalongxingchuang Experimental Instrument (Beijing) Co., Ltd.

[0083] In the following examples, the ENR aerogel is prepared by the following method: 100 mL of ENR emulsion with a solid content of 3 wt% is placed in a beaker, and a magnetic stirrer is used to stir at a speed of 800 rpm for 1 h. After forming a homogeneous emulsion, it is pre-cooled in a refrigerator at -20°C for 6 h and then placed in a freeze dryer FD-1A-50. The freeze drying is carried out at -50°C and a vacuum degree of 10 Pa for 48 h, and finally the ENR aerogel is obtained.

[0084] The ENR / CMC aerogel is prepared by the following method: 100 mL of epoxidized natural rubber (ENR) latex is added with carboxymethyl cellulose (CMC) according to the mass ratio (ENR: CMC ratio is 10:1, 10:2, 10:3, 10:4, 10:5) in a beaker, and a magnetic stirrer is used to stir at a speed of 800 rpm for 1 h. After forming a homogeneous emulsion, it is cooled to room temperature and then placed in a freeze dryer FD-1A-50. The freeze drying is carried out at -50°C and a vacuum degree of 10 Pa for 48 h, and finally the ENR / CMC1, ENR / CMC2, ENR / CMC3, ENR / CMC4, ENR / CMC5 aerogels are prepared.

[0085] Example 1, preparation of ENR / CMC-cMWCNT aerogel

[0086] 1) MWCNT carboxylation modification

[0087] 5g MWCNT was placed in a 250mL beaker, 150mL of concentrated sulfuric acid and 50mL of concentrated nitric acid were added to form a mixed acid solution, and was placed in a KQ-500DE ultrasonic cleaner, set at a frequency of 40kHz and a temperature of 60°C, and was ultrasonically treated for 6h. After the reaction was completed, the sample was transferred to a centrifuge tube and was placed in a TGL-16C centrifuge at a speed of 8000rpm for 10min, and the supernatant was discarded. The precipitate was repeatedly washed with deionized water until the pH of the washing solution was neutral. The washed sample was transferred to a DZF-6020 vacuum drying oven and was dried at 60°C under a vacuum of 10MPa for 12h to obtain carboxylated carbon nanotubes (cMWCNT).

[0088] 2) Preparation of CMC-cMWCNT dispersion composite

[0089] 3g of CMC powder was weighed and slowly added to 97ml of deionized water, and was placed in a magnetic stirrer and was stirred at a speed of 600rpm for 2h until completely dissolved. After standing for 2h to remove bubbles, a 3wt% CMC solution was obtained. 1.5g of cMWCNT was weighed and added to the above CMC solution to prepare a 1.5wt% cMWCNT dispersion. 0.5g of EDC was added to the dispersion, and was stirred at a speed of 500rpm for 6h at room temperature using a magnetic stirrer. After the reaction was completed, 0.5mL of ethylenediamine was added and was stirred for another 30min. The mixture was transferred to a centrifuge tube and was centrifuged at a speed of 12000rpm for 15min to remove unreacted catalyst and by-products, and a CMC-cMWCNT dispersion composite (CMC:cMWCNT=10:5, denoted as CMC-cMWCNT5 dispersion composite) was obtained. In the same way, CMC-cMWCNT1, CMC-cMWCNT2, CMC-cMWCNT3, and CMC-cMWCNT4 dispersion composites were prepared according to the mass ratio (CMC:cMWCNT ratio of 10:1, 10:2, 10:3, and 10:4).

[0090] 3) Preparation of ENR / CMC-MWCNTs aerogel

[0091] In 100 mL of ENR latex, CMC-cMWCNT dispersion composite liquid (CMC: cMWCNT ratio of 10:1, 10:2, 10:3, 10:4, 10:5) was added according to the mass ratio (ENR: CMC ratio of 10:1, 10:2, 10:3, 10:4, 10:5), stirred at 800 rpm for 1 h using a magnetic stirrer, to form a homogeneous emulsion. Subsequently, NaOH solution was added, the pH was adjusted to 9.0-10.0, and crosslinking was carried out at 800 rpm in a 60°C water bath for 4 h. After the reaction was completed, the pH was adjusted to neutral with acetic acid solution, and after cooling to room temperature, it was placed in a freeze dryer FD-1A-50, and freeze-dried at -50°C and a vacuum degree of 10 Pa for 48 h, to obtain ENR / CMC-cMWCNT aerogel.

[0092] Example 2, Morphology characterization

[0093] The microstructure of the aerogel sample was photographed by scanning electron microscope (SEM, S-4800, Japan).

[0094] Figure 2 The appearance and SEM images of ENR, ENR / CMC (ENR: CMC = 10:3) and ENR / CMC-cMWCNT (ENR: CMC = 10:3, CMC: cMWCNT = 10:3) aerogels.

[0095] Example 3, Investigation of thermal insulation performance of aerogel

[0096] The heat flux density and temperature difference through the sample were measured by a thermal flow meter (Instruments, HFM 436, USA) under a stable temperature gradient, and the thermal conductivity was calculated according to the Fourier law.

[0097] Figure 3 The thermal insulation performance of different aerogels. Temperature-time curves of ENR, ENR / CMC3 and ENR / CMC3-CMWCNT3 aerogels (A); surface equilibrium temperature and temperature difference between the aerogel and the heating plate (B); infrared thermal image of ENR / CMC3 and ENR / CMC3-CMWCNT3 aerogels on a 100°C heating plate (C); temperature-time curve of ENR / CMC3-CMWCNT3 aerogel during cyclic heating and cooling on the heating plate (D); DSC curve of ENR / CMC3-CMWCNT3 aerogel (E); optical image of a paper crane placed on ENR / CMC3-CMWCNT3 aerogel and burned with an alcohol lamp (F).

[0098] Example 4, Investigation of aerogel resilience performance

[0099] The rebound mechanical properties of the samples were tested using a universal mechanical testing machine (REM-710, China) equipped with a 50 N sensor.

[0100] Figure 4 Strain-rebound analysis of ENR / CMC aerogels with different MCM contents. Stress-strain curves of ENR / CMC aerogels with different CMC contents (A) where (ENR / CMC1, ENR / CMC2, ENR / CMC3, ENR / CMC4 refer to the aerogels prepared with the mass ratio of ENR to CMC being 10:1, 10:2, 10:3, 10:4, respectively); stress-strain curves of ENR / CMC-cMWCNT aerogels with different cMWCNT contents (B) where (ENR / CMC3-cMWCNT1, ENR / CMC3-cMWCNT2, ENR / CMC3-cMWCNT3, ENR / CMC3-cMWCNT4 refer to the aerogels prepared with the mass ratio of ENR to CMC being 10:3, the mass ratio of CMC to cMWCNT being 10:1, 10:2, 10:3, 10:4, respectively); compressive stress and hysteresis energy of ENR / CMC and ENR / CMC-cMWCNT aerogels (C); Young's modulus of ENR / CMC and ENR / CMC-cMWCNT aerogels (D); stress-strain curves of ENR / CMC3-cMWCNT3 aerogel at different strains (E); stress-strain curves of ENR / CMC3-cMWCNT3 aerogel at 70% strain for different times (F).

[0101] From Figure 4 (B) it can be seen that: ENR / CMC3-cMWCNT3 aerogel has the best rebound performance.

[0102] Example 5, Conductive properties of aerogels

[0103] The real-time current signal was recorded by an electrochemical workstation (CHI660E, CH Instruments, China), and a voltage of 1.0 V was applied to all measurements.

[0104] Figure 5Piezoelectric properties of ENR / CMC3-cMWCNT3 aerogel. The luminance change of light-emitting diode under the process of finger pressing ENR / CMC3-cMWCNT3 aerogel (A); the current change of ENR / CMC-cMWCNT aerogel under 1-10% deformation (B); the current change of ENR / CMC-cMWCNT aerogel under 10-50% deformation (C); the sensitivity test of aerogel sensor in the pressure range of 0-1.6 kPa (D); the current change of ENR / CMC-cMWCNT aerogel under different compression frequencies (E); the equivalent circuit model of aerogel compression change (F); the response time of aerogel under the condition of rapid loading and unloading (G).

[0105] Example 6, electromagnetic shielding performance of aerogel

[0106] The electromagnetic interference (EMI) shielding performance of the aerogel was measured in the frequency range of 8.2-12.4 GHz (X-band) at room temperature using an Agilent PNAN5244A vector network analyzer, and the sample was a square material with a thickness of 1 cm and a diameter of 4 cm x 4 cm.

[0107] Figure 6 Electromagnetic shielding properties of ENR / CMC-cMWCNT aerogels with different cMWCNT additions (abscissa 1, 2, 3, 4, 5 represent the mass ratio of CMC to cMWCNT as 10:1, 10:2, 10:3, 10:4, 10:5, respectively, and the mass ratio of ENR to CMC is 10:3). The relationship between conductivity and resistance and resistance of aerogels with different cMWCNT addition levels (A); electromagnetic path propagation mode diagram of ENR / CMC-cMWCNT aerogel (B); reflection shielding effectiveness (C), absorption shielding effectiveness (D), total shielding effectiveness (E) of ENR / CMC-cMWCNT aerogel and comparison of shielding effectiveness between different groups (F) (wherein, cMWCNT1, cMWCNT2, cMWCNT3, cMWCNT4, cMWCNT5 respectively refer to the aerogel with the mass ratio of ENR to CMC as 10:3, and the mass ratio of CMC to cMWCNT as 10:1, 10:2, 10:3, 10:4, 10:5).

[0108] Example 7, signal recognition of aerogel as a sensor

[0109] The skin electrical signal monitoring device of the aerogel sensor is composed of an ENR / CMC3-cMWCNT3 aerogel (the mass ratio of ENR to CMC is 10:3, and the mass ratio of CMC to cMWCNT is 10:3) sensor unit, a signal conditioning module (AD8232), and a data acquisition and transmission module (STM32 built-in ADC), and realizes real-time signal acquisition by pasting the sensor on the skin.

[0110] Figure 7 The aerogel sensor is used for detecting the human skin signals. Relative current changes caused by throat voice (A), elbow bending (B), arm bending (C), neck bending when nodding (D), neck rotation when rotating the head (E), and finger bending at different angles (F).

[0111] The application is described in detail above. For those skilled in the art, the application can be implemented in a wider range under equivalent parameters, concentrations and conditions without departing from the purpose and scope of the application and without unnecessary experiments. Although the application gives a special example, it should be understood that the application can be further improved. In summary, according to the principle of the application, the application intends to include any change, use or improvement of the application, including changes made by conventional techniques known in the art, which deviates from the range disclosed in the application.

Claims

1. A wearable device for human EMG signal detection, comprising a multifunctional elastic aerogel; The multifunctional elastic aerogel is prepared by reaction of carboxymethyl cellulose (CMC), epoxidized natural rubber (ENR) and carboxylated multi-walled carbon nanotubes (cMWCNT) as raw materials. The multifunctional elastic aerogel is prepared by a method comprising the following steps: 1) MWCNT carboxylation modification 5g of MWCNT was placed in a 250mL beaker, 150mL of concentrated sulfuric acid and 50mL of concentrated nitric acid were added to form an acid solution, and the KQ-500DE ultrasonic cleaner was set to a frequency of 40kHz and a temperature of 60℃, and ultrasonic treatment was carried out for 6h;After the reaction was completed, the sample was transferred to a centrifuge tube and placed in a TGL-16C centrifuge at a speed of 8000rpm for 10min, the supernatant was discarded, and the precipitate was washed repeatedly with deionized water until the pH of the washing liquid was neutral;The washed sample was transferred to a DZF-6020 vacuum drying oven and dried at 60℃ under a vacuum of 10MPa for 12h to obtain carboxylated carbon nanotubes (cMWCNT). 2) Preparation of CMC-cMWCNT dispersion composite liquid 3g of CMC powder was weighed and slowly added to 97ml of deionized water, placed on a magnetic stirrer and stirred at a speed of 600rpm for 2h until completely dissolved, and then left to stand for 2h to remove bubbles, obtaining a 3wt% CMC solution;1.5g of cMWCNT was weighed and added to the above CMC solution to prepare a 1.5wt% cMWCNT dispersion liquid;0.5g of EDC was added to the dispersion liquid, and a magnetic stirrer was used to stir at a speed of 500rpm for 6h at room temperature;After the reaction was completed, 0.5mL of ethylenediamine was added and stirring was continued for 30min;The mixture was transferred to a centrifuge tube and centrifuged at a speed of 12000rpm for 15min to remove unreacted catalyst and by-products, obtaining a CMC-cMWCNT dispersion composite liquid, CMC: cMWCNT = 10:5, denoted as CMC-cMWCNT5 dispersion composite liquid;In the same way, CMC-cMWCNT1, CMC-cMWCNT2, CMC-cMWCNT3 and CMC-cMWCNT4 dispersion composite liquids were prepared according to the mass ratio of CMC: cMWCNT of 10:1, 10:2, 10:3 and 10:4 respectively; 3) Preparation of ENR / CMC-MWCNTs aerogel In 100 mL of ENR latex, the ratio of ENR:CMC was 10:1, 10:2, 10:3, 10:4, 10:5 according to the mass ratio, CMC-cMWCNT dispersion composite liquid was added, the ratio of CMC:cMWCNT was 10:1, 10:2, 10:3, 10:4, 10:5, a magnetic stirrer was used to stir at a speed of 800 rpm for 1 h to form a homogeneous emulsion; then NaOH solution was added, the pH was adjusted to 9.0-10.0, crosslinking was carried out in a 60℃ water bath at 800 rpm for 4 h, after the reaction was completed, the pH was adjusted to neutral with acetic acid solution, after cooling to room temperature, it was put into a freeze dryer FD-1A-50, and freeze-dried at-50℃, a vacuum degree of 10 Pa for 48 h, finally ENR / CMC-cMWCNT aerogel was obtained.

2. The wearable device of claim 1, wherein, Based on the multi-functional elastic aerogel, a sensing array and a signal acquisition circuit are designed, high-precision stress recognition with a spatial resolution of less than 1 mm is realized, and a wearable device including the same can produce stable and reliable current responses in the process of multi-joint human motion monitoring.

3. The multi-functional elastic aerogel according to claim 1 or 2.

Images