Preparation method of supramolecular polymer based on lipoic acid and application of supramolecular polymer in sandwich type flexible wearable strain sensor

Abstract

The invention belongs to the technical field of flexible wearable equipment, and relates to a flexible strain sensor which is used for monitoring human motion and recognizing voice and is formed by assembling a multi-walled carbon nanotube / silver nanowire / lipoic acid supramolecular polymer according to a sandwich strategy and a preparation method of the flexible strain sensor. Firstly, a supramolecular polymer Poly (TA-GDA-Zr4 < + >) coated PMMA prepared by melting thioctic acid (TA) shows high tensile strength (485 kPa) and remarkable elongation at break (588%); a flexible strain sensor which is assembled by the supramolecular polymer and has a double-conductive-layer structure has high conductivity (2.22 S m <-1 >), a wide strain linear detection range (epsilon = 210%), good stability, excellent self-healing capability (the self-healing efficiency reaches 96.86% at 80 DEG C for 2 hours), excellent sensitivity (GF = 1416.283) and quick response performance (the response time is 94 ms, and the recovery time is 168 ms). Besides, a deep learning system is developed, accurate feature comparison is carried out on images, the recognition rate reaches 98.58%, and accurate voice recognition is achieved.

Description

Technical Field

[0001] This invention belongs to the field of flexible wearable device technology, and relates to a method for preparing a thioctic acid-based supramolecular polymer for monitoring human movement and voice recognition, and its application in a sandwich-type flexible wearable strain sensor. Background Technology

[0002] With the rapid development of medical and technological advancements, point-of-care testing (POCT) has become a major direction in clinical testing. This has led to new challenges for electronic strain sensing technology in fields such as electronic skin, human-computer interaction, wearable electronics, and motion monitoring. Traditional strain sensors are primarily based on metals and semiconductors, and while the technology is mature after years of development, their rigidity prevents integration with flexible surfaces like human skin. In complex deformation environments, they exhibit low sensitivity and detection range, limiting their applications and hindering their use in wearable sensor fields.

[0003] In recent years, with the emergence of advanced microfabrication technologies and new sensing / recording principles for novel functional organic conductive materials, especially the unique properties of organic conductive materials (including conductive polymers, graphene, and carbon nanotubes) have brought about new functions that are impossible to achieve with traditional metal or silicon-based devices. The application of organic and carbon-based conductors in wearable and implantable biosensors has become a rapidly developing research field with significant progress. The versatility and tunable properties of organic conductors have led to the development of soft, stretchable, transparent, and adhesive electrodes for connection to human skin and tissues. This improves biosensing performance and facilitates the attachment of devices to tissues and organs with minimal interference to the normal activities of human tissues.

[0004] Despite significant progress in developing highly stretchable and sensitive flexible wearable strain sensors, limitations still hinder their development. Most reported flexible strain sensors involve complex fabrication processes, are costly, and exhibit poor reusability and self-healing properties in complex operating environments.

[0005] The rapid development of supramolecular polymers has driven the rise of a new generation of flexible intelligent electronic devices, which have enormous potential in various applications. Their excellent self-healing capabilities allow flexible electronic devices to independently repair themselves after unpredictable structural damage during use, restoring their original functions and extending their lifespan and durability. The self-healing properties of most existing supramolecular polymers are built by introducing dynamic covalent and non-covalent hydrogen bonds, metal coordination bonds, host-guest interactions, and hydrophobic interactions into their polymer networks. However, supramolecular polymers based on non-covalent interactions are typically built upon petroleum-based covalent polymer networks and require complex polymerization steps. This not only increases the consumption of non-renewable resources but also results in high manufacturing costs. Therefore, selecting renewable materials from biomass resources to prepare self-healing supramolecular polymers is a promising option for future applications.

[0006] Therefore, it is essential to design a flexible wearable strain sensor with good adhesion, high reusability, wide detection range, high sensitivity, and rapid self-healing properties. Summary of the Invention

[0007] Based on this, the purpose of this invention is to provide a method for preparing a lipoic acid-based supramolecular polymer for monitoring human movement and speech recognition, and its application in a sandwich-type flexible wearable strain sensor. The flexible strain sensor provided by this invention possesses high sensitivity, good stability, a wide detection range, excellent reusability, and good self-healing ability. The detection method is simple and suitable for real-time detection, enabling it to detect various changes in human movement states. In future applications, it can be combined with machine learning to design a speech recognition system. The flexible strain sensor mentioned in this invention serves as a detection device for collecting different speech feature peaks.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A method for preparing a supramolecular polymer based on thioctic acid for monitoring human motion and voice recognition, and its application in a flexible wearable strain sensor assembled using a sandwich strategy. The sensor comprises a substrate layer, a response layer, and an encapsulation layer arranged sequentially from bottom to top, forming a sandwich structure. Silver paste is applied to copper foil at both ends of the response layer, and copper wires are attached. After heating, these become an integrated unit serving as left and right electrodes, thus creating a flexible strain sensor characterized by its sandwich structure.

[0010] Preferably, the base layer and the encapsulation layer are both made of a flexible supramolecular polymer with high Young's modulus, excellent biocompatibility, and efficient self-healing properties. The self-healing supramolecular polymer Poly(TA-GDA-Zr) 4+PMMA is prepared by melt polymerization of metal salt and thioctic acid (TA) at 140 ℃-150 ℃. Here, we prefer zirconium oxychloride octahydrate (ZrOCl2·8(H2O)).

[0011] Furthermore, to increase the tensile strength of the substrate layer, a PMMA solution is added during the preparation process; more preferably, the concentration is 70 mg / ml. Regarding the relationship between tensile strength and elongation, it is known that tensile strength is inversely proportional to elongation; these two physical quantities are balanced to meet the standards of strain sensors.

[0012] Preferably, the response layer is a conductive layer designed on the substrate layer, and the conductive response layer is divided into layer a and layer b. The response layer a is a conductive slurry prepared by incorporating multi-walled carbon nanotubes (MWCNTs) as a solute into polydimethylsiloxane (PDMS) and stirring thoroughly in the presence of n-hexane as a solvent.

[0013] Furthermore, to enhance the conductivity and resistivity stability of the response layer, a conductive response layer b is prepared. Silver nanowires (AgNWs) with a diameter of 40 nm and a length of 10 μm-20 μm are prepared by heating and stirring using silver nitrate (AgNO3), sodium chloride (NaCl), and polyvinylpyrrolidone (PVP). The prepared silver nanowire slurry is then spin-coated onto the cured PDMS / MWCNTs layer.

[0014] Preferably, the encapsulation preparation method is the same as the substrate preparation method.

[0015] In the aforementioned flexible sensor, the thickness of the substrate layer is 0.1 mm to 0.8 mm;

[0016] The thickness of the encapsulation layer is 0.1 mm to 0.8 mm;

[0017] The density of multi-walled carbon nanotubes in the responsive layer is 0.01 mg / cm³. 3 -0.05 mg / cm 3 The length is 2 μm-20 μm and the inner diameter is 2 nm-10 nm.

[0018] The flexible sensor of the present invention can be assembled according to the following steps:

[0019] Conductive paste was applied to the successfully prepared substrate layer using a custom mask with dimensions of 20 mm * 10 mm * 0.05 mm. Spin-coating was then performed on the cured PDMS / MWCNTs layer, transferred to a hot plate, and heated at 100℃-110℃ for 5 min. External copper foil wires were then used to assemble the electrodes and connect them to the conductive layer. The encapsulation layer was then transferred onto the conductive response layer for complete bonding, with dimensions identical to the substrate layer. Finally, the encapsulation was cured and encapsulated at 100℃-110℃ for 10 min on the hot plate.

[0020] In motion detection, the flexible strain sensor of this invention measures bending conditions by analyzing changes in electrical signals under different bending conditions through a patterned conductive circuit. It exhibits rapid response, excellent electrochemical stability, and good signal response performance. After 1000 cycles at 50% strain, its resistance signal shows no significant attenuation. The sensor material also possesses high sensitivity; at a maximum stretch of 210%, a high sensitivity GF = 1416.283 can be obtained. The results are as follows... Figure 5 As shown; and the material's response and recovery times are short, only 94 ms and 168 ms respectively. The specific measurement principle of the sensor is as follows;

[0021] When a flexible sensor undergoes bending deformation, the supramolecular polymer base layer and encapsulation layer elastically deform. Simultaneously, the spacing between the conductive nanomaterials in the response layer between the base layer and encapsulation layer changes, creating a network of microcracks. This breaks the conductive pathways, resulting in a significant change in resistance, thus giving the strain sensor a large measurement range and sensitivity. The magnitude of the resistance corresponds to the sensor's deformation, altering the overall conductivity of the response layer and causing different electrical signals to be output under different deformation conditions. This allows for the detection of muscle movements at various joints and even minute vibrations, such as vocal cord vibration.

[0022] The flexible wearable sensor material used in this invention for motion monitoring has extremely strong self-healing capabilities, as shown in the following results. Figure 2 After the sensor breaks, it can be immediately reconnected and still allow the small light bulb to light up normally, although the brightness is reduced by 20%. Under conditions of 80 ℃ and 2 hours, the self-healing process has almost no impact on the original mechanical and sensing properties, making it suitable for scenarios requiring frequent stretching in sensor applications. The self-healing efficiency reaches 96%, which is a significant advantage over similar polyurethane materials. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the wearable flexible strain sensor in an embodiment of the present invention.

[0024] Figure 2This is an optical microscope image of the tearing-self-healing of a flexible supramolecular polymer film in an embodiment of the present invention.

[0025] Figure 3 The stress-strain curves of supramolecular polymer films containing GDA and ZrOCl2·8(H2O) in different volume ratios are shown in the embodiments of the present invention.

[0026] Figure 4 This is a comparison chart of the relative resistivity of conductive fillers with different concentrations added to the conductive layer in embodiments of the present invention.

[0027] Figure 5 This is the sensitivity GF curve of the flexible strain sensor in an embodiment of the present invention.

[0028] Figure 6 The resistance change rate curves of the wearable flexible strain sensor of this invention applied to the human finger and wrist joints.

[0029] Figure 7 The figure shows the application results of the flexible strain sensor of the present invention in a deep learning-assisted speech recognition system. Detailed Implementation

[0030] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0031] like Figure 1 The diagram shown is a schematic representation of the overall structure of the wearable flexible strain sensor for measuring angular bending provided by the present invention. From top to bottom, the sensor consists of a substrate layer, a response layer, and an encapsulation layer.

[0032] In this invention, the self-healing supramolecular polymer Poly(TA-GDA-Zr) 4+ PMMA utilizes biomass-derived small-molecule thioctic acid (TA) as a monomer. At high temperatures, TA undergoes a thermal ring-opening reaction, forming a primary linear backbone with disulfide bonds, resulting in a viscous yellow liquid. Upon cooling to room temperature, the carboxyl groups on the side chains further crosslink through hydrogen bonding, forming a rigid solid polymer. However, the solid polymer exhibits metastable properties. Therefore, glyceryl dimethacrylate (GDA) is introduced as a crosslinking agent. After high-temperature melting of TA, the addition of GDA can quench the terminal diradicals of TA through anti-sulfurization, forming Poly(TA-GDA). Since TA readily undergoes reverse ring-closure depolymerization at low temperatures, a zirconium oxychloride octahydrate (ZrOCl2·8(H2O)) solution is introduced to introduce zirconium ions (ZrO2·8(H2O)). 4+Zirconium(IV) ions are introduced into the network as strong complex centers with carboxyl groups to replace some weak hydrogen bonds and stabilize Poly(TA-GDA), forming Poly(TA-GDA-Zr). 4+ @PMMA, while also improving the mechanical properties of the polymer. By comparing the stress-strain curves of supramolecular polymer films with different volume ratios of GDA and ZrOCl2·8(H2O), the results are as follows: Figure 3 The optimal concentration will be selected in subsequent experiments. The carbonyl group (C=O) in PMMA and Poly(TA-GDA-Zr) will be utilized. 4+ Hydrogen bonds can form between the hydroxyl (OH) groups in PMMA. This hydrogen bonding not only enhances the interfacial compatibility of the two materials but also creates additional cross-linking points at the molecular level, providing extra mechanical support and strengthening the Poly(TA-GDA-Zr) alloy. 4 + Tensile strength of PMMA.

[0033] In this invention, among several metal salts including ferric chloride (FeCl3), zinc chloride (ZnCl2), manganese chloride (MnCl2), and zirconium oxychloride octahydrate (ZrOCl2·8(H2O)), zirconium ions in ZrOCl2·8(H2O) are preferred, as a strong complex center with a carboxyl group replacing some of the weak hydrogen bonds. It should be noted that several previously unconsidered metal salts can also achieve metal coordination bonding. ZrOCl2·8(H2O) is preferred as the metal salt because zirconium ions have a higher coordination number compared to other metal ions, resulting in a more stable zirconium carboxylate cluster and a more stable corresponding compound. Compared to the prices of other metal salts, ZrOCl2·8(H2O) has a significant advantage in reducing sensor manufacturing costs.

[0034] The following is in conjunction with the appendix Figure 2 The present invention will be described in detail with reference to specific embodiments.

[0035] Example 1: Fabrication of a flexible strain sensor for motion monitoring, specifically including the following steps (the control group in Examples 1-5 consists of devices with a flexible substrate and encapsulation layer without the addition of crosslinking agent GDA):

[0036] (1) Self-healing supramolecular polymer base layer and encapsulation layer Poly(TA-GDA-Zr) 4+ Preparation of PMMA

[0037] First, ZrOCl2·8(H2O) powder was dissolved in ethanol to obtain a ZrOCl2·8(H2O) solution with a concentration of 200 mg / ml. Then, 0.6673 g of GDA (i.e., a TA to GDA molar ratio of 5:1) was taken (the molar ratio of monomer TA and small molecule crosslinking agent GDA was changed in subsequent examples).

[0038] Take 3 g of TA and place it in a reagent bottle. Under the preferred conditions of 140 ℃-150 ℃, more preferably 150 ℃, stir continuously in an oil bath until it is completely melted into a transparent yellow liquid. Then, slowly add 0.334 ml of ZrOCl2·8(H2O) solution to the reagent bottle. After reacting for 5 min, add 0.5 ml of PMMA solution (volume ratio of 4.85:1 to lipoic acid) to the reagent bottle. After reacting for 5 min, slowly add 0.6673 g of GDA to the reagent bottle. After reacting for 5 min, a binary melt is obtained. Pour the melt into a polytetrafluoroethylene mold (mold specifications are 30 mm*20 mm*0.5 mm and 25 mm*15 mm*0.5 mm, and the relevant mold specifications mentioned below are consistent) placed on a 150 ℃ hot plate. Cover with a layer of polytetrafluoroethylene mold, and then place it in a drying oven to cool for 10 min before demolding to obtain a flexible base layer.

[0039] (2) Fabrication of conductive MWCNTs / PDMS response layer

[0040] MWCNTs / PDMS membranes were prepared using an in-situ polymerization process. First, the PDMS precursor and curing agent were mixed in a beaker at a mass ratio of 10:1. Then, n-hexane and the PDMS precursor were mixed in the beaker at a mass ratio of 1:1 and stirred uniformly for 10 min. A mass fraction of 8% was then measured. wt % of MWCNTs were added to the beaker. The conductive paste was then evacuated in a vacuum drying oven for 30 minutes, and the conductive response layer a was completed.

[0041] (3) Preparation of silver nanowire (AgNWs) paste

[0042] Prepare sodium chloride (NaCl) solution, silver nitrate (AgNO3) solution, and polyvinylpyrrolidone (PVP) solution with concentrations of 1.8 mg / ml, 22 mg / ml, and 5 mg / ml, respectively.

[0043] Place the PVP solution in a 120℃ oil bath and stir to remove water for 15 min. Heat the oil bath to 170℃, add 0.2 ml of NaCl solution dropwise to the reagent bottle, and react for 30 min. Then, slowly add 2 ml of AgNO3 dropwise using a dropper. After the addition is complete, seal the bottle and react in the 170℃ oil bath for 30 min. Finally, centrifuge at 7000 r for 5 min, discard the supernatant, add acetone and continue centrifuging. Finally, discard the supernatant, add ethanol and seal. Before use, perform ultrasonic dispersion.

[0044] (4) Assembly of flexible strain sensors

[0045] Using a spin coater, a mask was applied to a flexible substrate, and a conductive paste of MWCNTs / PDMS was applied using a coating rod to form the response layer a. The sample was then placed on a spin coater, and 60 μl of silver nanowire paste was spin-coated onto the response layer a at 500 r. The sample was then placed on a hot plate and heated at 110 °C for 5 min to form the response layer b. The encapsulation layer was transferred to the sample and bonded together. The assembled sandwich-type sensor was then placed on a hot plate and heated at 110 °C for 10 min to cure and encapsulate.

[0046] Example 2: Fabrication of a flexible strain sensor for motion monitoring, specifically including the following steps.

[0047] (1) Self-healing supramolecular polymer base layer and encapsulation layer Poly(TA-GDA-Zr) 4+ Preparation of PMMA

[0048] Same as Example 1;

[0049] (2) Fabrication of conductive MWCNTs / PDMS response layer

[0050] The mass fraction weighed is 4 wt % of MWCNTs were added to the beaker. Other steps were the same as in Example 1;

[0051] (3) Preparation of silver nanowire (AgNWs) paste

[0052] Same as Example 1;

[0053] (4) Assembly of flexible strain sensors

[0054] Same as Example 1;

[0055] Example 3: Fabrication of a flexible strain sensor for motion monitoring, specifically including the following steps.

[0056] (1) Self-healing supramolecular polymer base layer and encapsulation layer Poly(TA-GDA-Zr) 4+ Preparation of PMMA

[0057] Same as Example 1;

[0058] (2) Fabrication of conductive MWCNTs / PDMS response layer

[0059] The mass fraction weighed is 6 wt % of MWCNTs were added to the beaker. Other steps were the same as in Example 1;

[0060] (3) Preparation of silver nanowire (AgNWs) paste

[0061] Same as Example 1;

[0062] (4) Assembly of flexible strain sensors

[0063] Same as Example 1;

[0064] Example 4: Fabrication of a flexible strain sensor for motion monitoring, specifically including the following steps.

[0065] (1) Self-healing supramolecular polymer base layer and encapsulation layer Poly(TA-GDA-Zr) 4+ Preparation of PMMA

[0066] First, ZrOCl2·8(H2O) powder was dissolved in ethanol to obtain a ZrOCl2·8(H2O) solution with a concentration of 200 mg / ml. Then, 1.2291 g of GDA (i.e., a TA to GDA molar ratio of 3:1) was taken. Other steps were the same as in Example 1;

[0067] (2) Fabrication of conductive MWCNTs / PDMS response layer

[0068] Same as Example 1;

[0069] (3) Preparation of silver nanowire (AgNWs) paste

[0070] Same as Example 1;

[0071] (4) Assembly of flexible strain sensors

[0072] Same as Example 1;

[0073] Example 5: Fabrication of a flexible strain sensor for motion monitoring, specifically including the following steps.

[0074] (1) Self-healing supramolecular polymer base layer and encapsulation layer Poly(TA-GDA-Zr) 4+ Preparation of PMMA

[0075] First, ZrOCl2·8(H2O) powder was dissolved in ethanol to obtain a ZrOCl2·8(H2O) solution with a concentration of 200 mg / ml. Then, 0.5268 g of GDA (i.e., a TA to GDA molar ratio of 7:1) was taken. Other steps were the same as in Example 1;

[0076] (2) Fabrication of conductive MWCNTs / PDMS response layer

[0077] Same as Example 1;

[0078] (3) Preparation of silver nanowire (AgNWs) paste

[0079] Same as Example 1;

[0080] (4) Assembly of flexible strain sensors

[0081] Same as Example 1;

[0082] Table 1: Performance test results of the flexible wearable sensor material for motion monitoring according to the present invention

[0083] Example Resistance (KΩ) Tensile stress (MPa) Elongation at break (%) GF (Maximum Strength) Example 1 0.4±0.05 0.4852±0.009 588±8 1416.283±0.22 Example 2 11.3±0.2 - - 1200.33±0.43 Example 3 5.3±0.1 - - 971.63±0.13 Example 4 - 0.2911±0.008 532±3 - Example 5 - 0.2723±0.006 375±4 -

[0084] The specific steps of the experiment on the relative resistance change of the sensor under different strains are as follows: The measurement factor (GF) is considered an important parameter for quantitatively evaluating the sensitivity of the sensor, representing the typical strain-relative resistance response law. GF can be expressed by the following equation:

[0085] GF = in : Relative change in resistance : Applied strain / pressure

[0086] As can be seen from the experimental data in Table 1, the resistance of the flexible wearable sensor materials for motion monitoring prepared in Examples 2 and 3 is significantly higher than that of the flexible wearable sensor for motion monitoring prepared in Example 1. The comparison of their resistance change rates is shown in the graph below. Figure 4 This indicates that when the carbon nanotube concentration is 8... wt At a concentration of %, the characteristic peaks exhibited by the device are most stable. When the concentration is further increased, it is found that too much conductive filler is added to the PDMS, resulting in poor dispersibility and easy agglomeration, which makes the conductive film mechanically brittle and difficult to process into films.

[0087] The flexible strain sensor of this invention is used to test the movement of human finger and wrist joints. Figure 6As can be seen, the wearable sensor exhibits a consistent and stable response signal, demonstrating its ability to detect signals of different frequencies. Similarly, other joint movements such as those of the arm, neck, wrist, and ankle can be accurately detected by the sensor of this invention. We designed the ResNet50 convolutional neural network algorithm, a deep learning algorithm based on deep convolutional neural networks (CNNs). By attaching the sensor to the vibration point of the human vocal cords, we collected feature peaks of eight real-time speech signals, including "Whatever," "Hello," and "Baby." Each speech signal was sampled for 200 cycles, resulting in a total dataset of 1600 sample cycles. The dataset was divided into training, test, and validation sets (in an 8:1:1 ratio) for further labeling. Then, the ReLU activation function was used to increase the nonlinearity of the network. The data was processed through convolution and residual structures to extract original data features for classification decisions. Fully connected layers are responsible for connecting the learned features and classifying them using the Softmax function, finally producing the results at the output layer. Figure 7 As can be seen, after 400 epochs of training, both the training loss and accuracy reached an ideal state. The recognition accuracy of the TMAT sensor after combining deep learning is illustrated using a confusion matrix (numbered A, B, C…H) composed of eight speech signal feature peaks; the overall accuracy reached 98.58%.

[0088] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with practical applications and with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A sandwich type flexible strain sensor based on MWCNTs / AgNWs / TA supramolecular polymer and a preparation method thereof, comprising, from bottom to top, a substrate layer, a response layer and an encapsulation layer;The response layer a, b is a conductive layer arranged on the substrate layer;The conductive layer a is composed of PDMS / MWCNTs, and the conductive layer b is composed of one-dimensional conductive silver nanowires;The substrate layer and the encapsulation layer are formed by supramolecular polymer Poly(TA-GDA-Zr 4+ )@PMMA.In response to the use of silver glue coated on the copper foil at both ends of the response layer, and the adhesion of copper wire, after heating, it becomes integrated as left and right electrodes, and is characterized by a sandwich structure.

2. The method of claim 1, wherein the flexible strain sensor is prepared by the steps of: The preparation method comprises: (1) preparing a flexible supramolecular polymer by a high-temperature melting method, and forming a base layer and an encapsulation layer after cooling and solidification; the thickness of the base layer is 0.1 mm-0.8 mm; the thickness of the encapsulation layer is 0.1 mm-0.8 mm. A conductive paste containing multi-walled carbon nanotubes / polydimethylsiloxane is scraped on the flexible base by using a mask plate, and is dried and solidified to form a conductive response layer a; in the response layer a, the density of the multi-walled carbon nanotubes is 0.01 mg / cm 3 -0.1 mg / cm 3 , the length is 2 μm-20 μm, and the inner diameter is 2 nm-10 nm. Wherein, the mass fraction of the carbon nanotubes in the polydimethylsiloxane is 3 wt%-10 wt%. A silver nanowire conductive paste is spin-coated on the conductive response layer a, and is dried and solidified to form a conductive response layer b; in the response layer b, the diameter of the silver nanowire is 10 nm-60 nm, and the length is 5 μm-30 μm. The sensing film layer on the conductive electrode layer is formed into a reticular microcrack structure by repeatedly bending the flexible polymer matrix, and the flexible strain sensor with the reticular microcrack structure is obtained; wherein, the crack depth of the formed reticular microcrack structure is less than the thickness of the sensing film layer. (2) The molar ratio of thioctic acid and dimethyl acrylate glycerol ester is 5:1; a zirconium oxychloride·octahydrate solution is prepared by using ethanol as a solvent; the volume ratio of thioctic acid and zirconium oxychloride·octahydrate is 7:1; a polymethyl methacrylate solution is prepared by using anisole and butanone as solvents; the volume ratio of thioctic acid and polymethyl methacrylate is 4.85:

1. (3) The steps of preparing a flexible supramolecular polymer by a high-temperature melting method, and forming a base layer and an encapsulation layer after cooling and solidification are as follows: thioctic acid monomers are stirred at 140 ℃-150 ℃ for 10 min-20 min to obtain a transparent yellow liquid A; zirconium oxychloride·octahydrate is added into A, and is stirred at 140 ℃-150 ℃ for 5 min-10 min to obtain a mixture B; polymethyl methacrylate is added into the mixture B, and is stirred at 140 ℃-150 ℃ for 5 min-10 min to obtain a mixture C; dimethyl acrylate glycerol ester is added into the mixture C, and is stirred at 140 ℃-150 ℃ for 5 min-10 min, and then is poured into a mold, and is cooled and solidified to obtain a flexible material, that is, the flexible wearable sensor material for motion monitoring.

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