Degradable polylipoic acid zwitterionic gel wireless strain sensor, preparation method and application thereof

Abstract

The invention provides a preparation method of a degradable polylipoic acid zwitterionic gel wireless strain sensor, which comprises the following steps: neutralizing lipoic acid into sodium lipoic acid by using sodium ethoxide, and then preparing a Poly (LA-LANa) polyhydrogel prepolymer from the sodium lipoic acid and the lipoic acid through ring-opening reaction (ROP); finally, [2-(methylacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) is introduced into the poly-hydrogel prepolymer, and stable Poly (LA-LANa-SBMA-n) (PLLS-n) hydrogel, namely the degradable polylipoic acid zwitterionic gel wireless strain sensor, is formed through a nucleophilic addition reaction. Wherein n is the quality of the SBMA. The PLLS hydrogel has the advantages of being high in strength, good in toughness, good in adhesion, easy to heal, easy to degrade and good in conductivity. The method can also be used for a wireless wearable sensor; the invention also provides the PLLS hydrogel prepared by the method and application of the PLLS hydrogel.

Description

Technical Field

[0001] The invention belongs to the field of gel sensors, and in particular relates to a degradable polylipoic acid zwitterionic gel wireless strain sensor and a preparation method thereof. Background Art

[0002] As a key bridge connecting human health monitoring and digital management systems, gel sensors have developed rapidly in the field of wireless wearable devices in recent years. However, the poor biocompatibility of traditional conductive gels limits their application in flexible wearable devices and biomedical fields. Biogels can not only be better compatible with biological tissues and reduce rejection, but also stably transmit wireless signals, promoting the development of bioelectronics and wireless medical monitoring technology. However, problems such as low strength, poor toughness, poor adhesion, difficulty in healing and non-degradation have always been bottlenecks restricting their development. For example, Si et al. prepared bioconductive gels based on catechol-grafted chitosan to achieve the functions of human motion monitoring and promoting wound healing, but did not show satisfactory stretchability and adhesion; Yan et al. prepared fish gelatin (FG)-based biogels that showed high feasibility in wireless wearable monitoring platforms and triboelectric sensing devices, but the gel sensor could not self-heal, and the service life of the device was limited.

[0003] In summary, a multifunctional biogel with high stretchability, self-healing and adhesion for wireless strain sensing is urgently needed to be prepared. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the technical problems of low strength, poor toughness, poor adhesion, difficult healing and non-degradable in the prior art are solved;

[0005] The present invention also aims to provide a method for preparing a degradable polylipoic acid zwitterionic gel wireless strain sensor, wherein the preparation method comprises the following steps: neutralizing lipoic acid with sodium ethoxide to form sodium lipoate, and then preparing a Poly(LA-LANa) polyhydrogel prepolymer by a ring-opening reaction (ROP) of the sodium lipoate and lipoic acid; finally, introducing [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SBMA) into the polyhydrogel prepolymer to form a stable Poly(LA-LANa-SBMA-n) (PLLS-n) hydrogel by a nucleophilic addition reaction, wherein n is the mass of SBMA; the reaction formula of the preparation method is:

[0006]

[0007] Preferably, the preparation method comprises the following steps:

[0008] a. Preparation of sodium lipoate: Sodium ethoxide and lipoic acid were dissolved in quantitative anhydrous ethanol respectively, then the sodium ethoxide solution was added dropwise to the lipoic acid (LA) solution, stirred for 12 h, centrifuged, and vacuum dried to obtain yellow sodium lipoate (LANa) powder and stored at -20 °C;

[0009] b. Add LA powder and LANa powder into 1 mL of deionized water to form a LA / LANa mixed dispersion to obtain PLL hydrogel prepolymer, stir it at 90°C until it melts, add SBMA, and cool it at room temperature to obtain Poly

[0010] (LA-LANa-SBMA-n)(PLLS-n) hydrogel, that is, the degradable polylipoic acid zwitterionic gel wireless strain sensor.

[0011] Preferably, in step a, the mass ratio of sodium ethoxide to lipoic acid is 2.5 to 3.5.

[0012] Preferably, the mass ratio of LA:LANa in step b is 1.5-2; the molar ratio of LA:LANa in step b is 1.5-2.0.

[0013] Preferably, in step b, the molar ratio LA:LANa=1.9:1.

[0014] Preferably, the mass concentration range of the sodium ethoxide solution is 24-34 g / L; the mass concentration range of the lipoic acid (LA) solution is 5.3-10.3 g / L.

[0015] Preferably, the mass range of SBMA added in step b is 30-60 mg, and the concentration range is 30-60 g / L.

[0016] Preferably, the preparation method comprises the following steps:

[0017] a. Preparation of sodium lipoate: 1.7 g of sodium ethoxide and 5.15 g of lipoic acid were dissolved in 50 mL of anhydrous ethanol, then the sodium ethoxide solution was added dropwise to the lipoic acid (LA) solution, stirred for 12 h, centrifuged, and vacuum dried to obtain yellow sodium lipoate (LANa) powder, which was stored at -20 °C;

[0018] b. Add 240 mg LA and 140 mg LANa powder into 1 mL deionized water to form a LA / LANa mixed dispersion to prepare a PLL hydrogel prepolymer, which was stirred at 90°C until melted, SBMA was added, and cooled at room temperature to obtain a poly(LA-LANa-SBMA-n)(PLLS-n) hydrogel.

[0019] A PLLS hydrogel, and a gel wireless strain sensor prepared by the preparation method.

[0020] A wireless wearable sensor made by integrating the above-mentioned gel wireless strain sensor with a Bluetooth system

[0021] The preparation method of the degradable polylipoic acid zwitterionic gel wireless strain sensor provided in this case has the following beneficial effects:

[0022]

[0023] 1) The PLLS hydrogel prepared by the present invention has necessary material properties, such as high stretchability, excellent self-healing property, high adhesion, water retention, good electrical conductivity and low swelling.

[0024] 2) The PLLS hydrogel prepared by the present invention has biological properties, such as high water content, easy degradation, high antibacterial property, antioxidant property and excellent biocompatibility;

[0025] 3) The PLLS hydrogel prepared by the present invention can be used for wireless wearable sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is the Raman spectrum of the PLLS gel;

[0027] Figure 2 The present invention is the S2p XPS high-resolution scanning spectrum of the PLLS gel;

[0028] Figure 3 is the infrared spectrum of the PLLS gel of the present invention;

[0029] Figure 4 The scanning electron microscope image of the PLLS gel of the present invention (PLLS-30 is 30 mg of SBMA added; PLLS-45 is 45 mg of SBMA added; PLLS-60 is 60 mg of SBMA added);

[0030] Figure 5 The present invention provides the in vitro biocompatibility, antioxidant and antibacterial properties of the PLLS gel;

[0031] Figure 6 The present invention is the conductivity and sensing properties of the PLLS gel;

[0032] Figure 7 The mechanical properties of the PLLS gel of the present invention ((a) Photo of PLLS-30 hydrogel with high elongation. (b) Tensile stress-strain curve; (c) Tensile strength and tensile capacity; (d) Young's modulus and toughness; (e) XRD pattern; (f) Photo of PLLS-60 hydrogel);

[0033] Figure 8 The anti-swelling and degradation properties of the PLLS hydrogel of the present invention ((a) swelling; (b) degradation; (c) water content; (d) water loss; (e) scanning electron microscope images of the hydrogel before and after 7 days of degradation);

[0034] Fig. 9 The present invention provides that the PLLS gel is used as a wireless wearable sensor to monitor various human activities. DETAILED DESCRIPTION

[0035] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0036] Embodiment 1:

[0037] The present invention also aims to provide a method for preparing a degradable polylipoic acid zwitterionic gel wireless strain sensor, wherein lipoic acid is neutralized with sodium ethoxide to form sodium lipoate, and then the sodium lipoate and lipoic acid are reacted through a ring-opening reaction (ROP) to prepare a Poly (LA-LANa) polyhydrogel prepolymer; finally, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl) ammonium hydroxide (SBMA) is introduced into the polyhydrogel prepolymer to form a stable Poly (LA-LANa-SBMA-n) (PLLS-n) hydrogel through a nucleophilic addition reaction, wherein n is the mass of SBMA; the reaction formula of the preparation method is:

[0038]

[0039] The preparation steps of the preparation method are:

[0040] a. Preparation of sodium lipoate: Sodium ethoxide and lipoic acid were dissolved in quantitative anhydrous ethanol respectively, then the sodium ethoxide solution was added dropwise to the lipoic acid (LA) solution, stirred for 12 h, centrifuged, and vacuum dried to obtain yellow sodium lipoate (LANa) powder and stored at -20 °C;

[0041] b. Add LA powder and LANa powder into 1 mL of deionized water to form a LA / LANa mixed dispersion to obtain PLL hydrogel prepolymer, stir it at 90°C until it melts, add SBMA, and cool it at room temperature to obtain Poly

[0042] (LA-LANa-SBMA-n)(PLLS-n) hydrogel, i.e., the degradable polylipoic acid zwitterionic gel with wireless strain

[0043] Sensor. In step a, the mass ratio of sodium ethoxide to lipoic acid is 2.5-3.5. In step b, the mass ratio of LA:LANa is 1.5-2; the molar ratio of LA:LANa in step b is 1.5-2.0. In step b, the molar ratio LA:LANa=1.9:1. The mass concentration range of sodium ethoxide solution is 24-34 g / L; the mass concentration range of lipoic acid (LA) solution is 5.3-10.3 g / L. In step b, the mass range of SBMA added is 30-60 mg, and the concentration range is 30-60 g / L.

[0044] Embodiment 2:

[0045] A method for preparing a degradable polylipoic acid zwitterionic gel wireless strain sensor:

[0046] 1. Material preparation:

[0047] DL-lipoic acid (LA, 99%), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonatepropyl)ammonium hydroxide (SBMA, ≥97%), anhydrous ethanol, sodium ethoxide (CH3CH2ONa, 96%), and 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH, 97%) were purchased from Aladdin, and phosphate buffered saline powder (PBS, 0.01 M) was purchased from Solebol.

[0048] 2. Preparation of sodium lipoate (LANa):

[0049] First, 1.7 g of sodium ethoxide and 5.15 g of lipoic acid were dissolved in 50 mL of anhydrous ethanol respectively; the sodium ethoxide solution was added dropwise to the LA solution, and the mixed solution was stirred at room temperature for 12 h. Finally, it was centrifuged and vacuum dried to obtain yellow sodium lipoate (LANa) powder, and the yellow powder was stored at -20°C.

[0050] 3. Preparation of PLLS hydrogel:

[0051] First, 240 mg LA and 140 mg LANa powder were added to 1 mL deionized water to form a LA / LANa mixed dispersion (nLA:LANa=1.9:1), which was stirred at 90°C until melted, and different amounts of SBMA were added, and the mixture was cooled at room temperature to obtain poly(LA-LANa-SBMA-n) (PLLS-n) hydrogel; where n is the mass of SBMA.

[0052] The following tests were performed on the poly(LA-LANa-SBMA-n) (PLLS-n) hydrogel:

[0053] A. Gelation, structure and morphology of PLLS hydrogel (abbreviation of poly(LA-LANa-SBMA-n)(PLLS-n) hydrogel, hereinafter)

[0054] After adding SBMA to the LA / LANa dispersion undergoing ring-opening polymerization (ROP) at 90°C, a nucleophilic addition reaction occurred, and a yellow and stable PLLS hydrogel was formed at room temperature; the successful occurrence of the polymerization reaction can be confirmed by Raman spectroscopy ( Figure 1 ) and XPS spectra ( Figure 2 ) to confirm. The cyclic disulfide bond in LA exhibits a single absorption vibration peak (513 cm -1 ), this peak splits into two shoulders (506 and 522 cm) after ROP due to the presence of linear disulfide bonds in the gel. -1 ). In addition, in the Raman spectrum, 673 cm -1 A new CS bond peak appeared at 162.8 eV in the XPS spectrum, indicating that the SBMA double bond underwent a nucleophilic addition reaction with the thiol group at the end of the PLL chain.

[0055] Further analysis by FT-IR spectroscopy ( Figure 3 ) characterized the chemical structure of the hydrogel. -1 The absorption peak at 1034 cm is attributed to the stretching vibration of C=O in LA and SBMA. -1 The absorption peak of S=O stretching vibration on the SBMA sulfonic acid group is shown at , which indicates that SBMA was successfully introduced into the hydrogel. Compared with PLL gel, the CS characteristic peak in PLLS gel is blue-shifted, which is due to the formation of hydrogen bonds in the gel matrix.

[0056] Figure 4 The SEM images in the figure show that the surface of the PLL hydrogel presents a lamellar structure. After the introduction of SBMA, the microscopic surface of the PLLS gel becomes compact. With the increase of SBMA content, the gel structure becomes smoother and more uniform due to the enhanced hydrogen bonding and electrostatic interaction in the gel network. The increase in the number of non-covalent bonds shortens the distance between polymer chains, thus forming a more stable and compact polymer structure. EDS results show that the elements C, N, O, S and Na are evenly distributed in the gel matrix.

[0057] B. In vitro biocompatibility, antioxidant and antibacterial properties of PLLS hydrogels

[0058] As a bridge between the human body and electrodes, hydrogel sensors need to have good biocompatibility. Figure 5The CCK-8 test results in ac showed that the survival rate of L929 cells co-cultured with the hydrogel extract was not significantly different from that of the control group, indicating that these hydrogels were not cytotoxic. In addition, the experimental cells showed the same cell morphology as the control group. The results of Calcein-AM / PI staining showed that most cells showed strong green fluorescence (living cells), while no obvious red fluorescence (dead cells) was observed, further proving that the hydrogel has good biocompatibility and will not cause adverse effects on the skin when used as a sensor ( Figure 5 d).

[0059] To protect the skin from bacterial invasion, the hydrogel must also have antibacterial properties. As expected, PLLS-60 showed higher inhibition against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) compared to PLL gel, reaching 97.72% and 98.57%, respectively. Figure 5 ef). The excellent antibacterial properties of the hydrogel are mainly attributed to the synergistic effects of LA, LANa and SBMA: (1) LA-based monomers kill bacteria by depolarizing and increasing the permeability of bacterial cell membranes, leading to leakage of intracellular substances. (2) There is a strong electrostatic attraction between the positively charged part of SBMA and the negatively charged components in the bacterial phospholipid membrane, which causes the bacterial membrane to disintegrate and inactivate the bacteria.

[0060] Due to the hydrophobic nature of LA monomers, they cannot effectively exert antioxidant activity in an aqueous environment. However, hydrophilic LANa can effectively scavenge reactive oxygen species (ROS) due to the strong reducing property of disulfide bonds. Figure 5 As shown in Figures 5g and 5h, the PLLS gel exhibited a high DPPH radical scavenging efficiency, reaching 82.3% after 0.5 h. The color of the DPPH solution changed from dark purple to yellow after 0.5 h of incubation. This is because the water-soluble LANa small molecules released during the degradation of the gel matrix effectively scavenged ROS. This suggests that the PLLS gel can be used as an antioxidant and has great potential in the biomedical field.

[0061] C. Conductive and sensing properties of PLLS hydrogel

[0062] Electrochemical impedance spectroscopy (EIS) was used to investigate the effect of SBMA on the ionic conductivity of PLLS hydrogels. Compared with PLL gels, PLLS gels have higher conductivity. Figure 6 The electrochemical impedance spectroscopy (EIS) graph in a shows that the conductivity of the PLL gel is limited (0.04 mS / cm) due to the crystalline phase restricting the movement of ions. The maximum conductivity of the PLLS gel reaches 1.72 mS / cm ( Figure 6b), this improvement is mainly due to the amorphous structure of the PLLS gel. The zwitterionic structure also facilitates ion migration. However, when the SBMA content exceeds 45 mg, the ionic conductivity decreases due to the increased crosslinking density of the gel network, which hinders the free transport of ions.

[0063] Due to its excellent stretchability, adhesion, elasticity, and conductivity, PLLS-60 hydrogel is an ideal candidate for strain, compression, and temperature sensing. Figure 6 c, within the strain range of 0-400%, the gel exhibited two distinct gauge factor (GF) values: 1.14 (0-200%) and 2.21 (200-400%), indicating excellent strain sensitivity over a wide strain range. 400 dynamic cyclic tensile tests demonstrated its good durability, stability, and repeatability ( Figure 6 d). These properties are mainly attributed to the presence of various dynamic bonds (such as disulfide bonds, hydrogen bonds, and electrostatic interactions) in the gel network. Figure 6 e shows the significant relative resistance changes of the gel under different strains (25%, 50% and 100%).

[0064] In addition, the compression and temperature response properties of the gels were investigated. Figure 6 f shows that the signal response of the gel changes with the change of finger pressure. From 20℃ to 80℃, the ΔR / R0 of the gel gradually decreases, and its temperature coefficient of resistance (TCR) values ​​are -1.76% / ℃ (20-50℃) and -1.02% / ℃ (50-60℃) respectively ( Figure 6 g). Cyclic thermal simulation experiments in the temperature range of 35-45°C showed that it has excellent repeatability ( Figure 6 h), and the temperature changes were monitored by infrared imaging (Figure S11). These results indicate that the hydrogel has good strain, compression, and temperature sensing properties and can be used to detect human activities. Figure 6 As shown in Fig. i, compared with other PLA or PSBMA-based sensors, the PLLS-60 hydrogel sensor exhibits excellent overall performance in terms of stretchability, degradation, self-adhesion, self-healing, anti-swelling, antibacterial, antioxidant and GF[4,14,17,23,24,35,45].

[0065] D. Mechanical properties of PLLS hydrogels

[0066] High stretchability and toughness are essential properties for hydrogel strain sensors. As expected, PLLS hydrogels exhibit high stretchability and elastic recovery. Figure 7As shown in Figures ac, although the PLL hydrogel exhibited high tensile strength, its elongation at break was limited. In contrast, the tensile strength of the PLLS hydrogel decreased, but its elongation at break was improved. In particular, the PLLS-30 hydrogel was able to be stretched to 22 times its original length without breaking. The cylindrical PLLS-60 hydrogel can return to its original shape after being pressed by a finger or a sharp blade, indicating that it has excellent compressive resistance and toughness ( Figure 7 d and 7f). With the increase of SBMA content, the elongation at break decreased, which is related to the aggregation structure of the hydrogel. The crystalline phase in the PLL gel is beneficial to improve its tensile strength and modulus, but it also restricts the movement of molecular segments, resulting in poor flexibility and elongation at break. From the XRD spectrum ( Figure 7 e) It can be seen that LA shows a sharp diffraction peak at 23.2°, indicating that it has a highly ordered crystalline structure. The PLL gel shows a diffraction peak with a lower intensity. The macroscopic dendritic crystal morphology also indicates that it is a semicrystalline polymer. This is because the ROP of LA and LANa destroys the ordered structure of LA, and LANa does not stabilize all PLA chains, causing the PLL gel to partially depolymerize at room temperature. However, no diffraction peak was observed in the PLLS-30 gel, indicating that the introduced SBMA effectively quenched the thiol groups at the ends of the PLL chains and disrupted the ordered arrangement of the macromolecular chains, forming an amorphous phase. This phase structure transition gives the PLLS hydrogel good transparency, in sharp contrast to the opaque PLL hydrogel. Transparency is particularly useful for human-computer interaction devices, especially in the biomedical field, making it possible to visualize internal conditions.

[0067] E. Anti-swelling and degradation properties of PLLS hydrogel

[0068] The widespread use of low-degradable electronic waste has placed a significant burden on the environment, thereby increasing the demand for biodegradable hydrogels. As expected, PLLS hydrogels exhibited a low swelling ratio and a high degradation rate ( Figure 8 ab). With the increase of SBMA content, the swelling rate and degradation rate also increased, reaching 3.34% and 71.63% after 14 days of degradation, respectively. These hydrogels reached swelling equilibrium in PBS solution within 5 hours, and their swelling rate was less than 5%. The cross-sectional morphology of PLLS-60 hydrogel before and after degradation showed large erosion holes, which was different from the compact and non-porous network structure of the original sample ( Figure 8 e). The weak alkalinity of PBS solution can destroy the disulfide bonds in the PLLS macromolecular chain, leading to degradation8.

[0069] In addition, PLLS hydrogel also has high water content and good water retention capacity. The water content of PLL hydrogel is only 48.66%, while the water content of PLLS hydrogel increases significantly to 70.87%, retaining most of the water ( Figure 8 c). PLLS hydrogel exhibits a low water loss rate, the lowest being 44.04%, and has good environmental stability ( Figure 8 d). This is because SBMA can induce electrostatic hydration of water molecules, thereby enhancing the water retention performance.

[0070] Embodiment 3:

[0071] PLLS hydrogel-based wireless wearable sensor for human motion detection:

[0072] Based on the excellent sensing performance of PLLS-60 hydrogel, it was integrated with the Bluetooth system to construct a wireless wearable sensor ( Fig. 9 a). Due to its excellent adhesion, the sensor can be directly attached to various parts of the human body without the use of glue. The PLLS-60 hydrogel wireless sensor is able to detect large and small ranges of body movements. The sensor can not only accurately distinguish different degrees of finger bending ( Fig. 9 In addition, the wireless sensor also monitored the movement of other human joints, showing stable and repeatable signals, such as wrist ( Fig. 9 d) Elbow and knee joint movements ( Fig. 9 f). When the sensors were attached to the volunteers’ eyebrows and mouth corners, significant signal changes occurred when the volunteers smiled and frowned ( Fig. 9 When the sensor was attached to the volunteer's throat, the change in relative resistance showed similar curves when the volunteer said "Hydrogel", "Hi" and "Hello" respectively ( Fig. 9 i). The results show that the sensor has great potential in facial expression and speech recognition, and can be used for human-computer interaction and pronunciation rehabilitation training for the deaf and mute.

[0073] In addition, based on the good resilience of the hydrogel, it can be used as a pressure sensor to detect the writing of different English letters. Fig. 9 As shown in j, it can be observed that the relative resistance change of each letter is significantly different. PLLS-60 hydrogel can also be assembled into an electronic pen to simulate the hand-drawing process and perform various operations on smartphones, such as sliding and clicking ( Fig. 9 k). The results show that the sensor can effectively recognize handwriting and hand drawing as an intelligent electronic device. Interestingly, based on the temperature-sensitive behavior of the sensor, it can be used to monitor breathing in real time ( Fig. 9l), and is able to monitor finger movements in the temperature range of 35-45°C.

[0074] In conclusion, PLLS hydrogels demonstrated multifunctionality and could accurately monitor various human activities in daily life, showing great potential in wireless wearable devices for joint disease diagnosis, speech recognition, and facial expression recognition.

[0075] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a degradable polylipoic acid zwitterionic gel wireless strain sensor, characterized in that: Lipoic acid is neutralized with sodium ethoxide to form sodium lipoate, and then the sodium lipoate and lipoic acid are reacted through a ring-opening reaction (ROP) to prepare a Poly(LA-LANa) polyhydrogel prepolymer; finally, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SBMA) is introduced into the polyhydrogel prepolymer to form a stable Poly(LA-LANa-SBMA-n) (PLLS-n) hydrogel through a nucleophilic addition reaction, i.e., the degradable polylipoic acid zwitterionic gel wireless strain sensor; wherein n is the mass of SBMA; the reaction formula of the preparation method is:

2. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 1, characterized in that: The preparation steps of the preparation method are: a. Dissolve sodium ethoxide and lipoic acid (LA) in quantitative anhydrous ethanol respectively, then add the sodium ethoxide solution dropwise to the lipoic acid solution, stir for 12 hours, centrifuge, and vacuum dry to obtain yellow sodium lipoate (LANa) powder and store it at -20°C; b. Add LA powder and LANa powder to 1 mL of deionized water to form a LA / LANa mixed dispersion, stir it at 90°C until it melts to obtain a PLL hydrogel prepolymer, add SBMA, and cool it at room temperature to obtain a Poly(LA-LANa-SBMA-n)(PLLS-n) hydrogel, i.e., the degradable polylipoic acid zwitterionic gel wireless strain sensor.

3. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 2, characterized in that: In step a, the mass ratio of sodium ethoxide to thioctic acid is 2.5-3.

5.

4. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 2 or 3, characterized in that: The mass ratio of LA:LANa in step b is 1.5-2; the molar ratio of LA:LANa in step b is 1.5-2.

0.

5. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 4, characterized in that: In step b, the molar ratio of LA:LANa is 1.9:

1.

6. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 5, characterized in that: The mass concentration range of the sodium ethoxide solution is 24-34 g / L; the mass concentration range of the lipoic acid (LA) solution is 5.3-10.3 g / L.

7. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 6, characterized in that: The mass range of SBMA added in step b is 30-60 mg, and the concentration range is 30-60 g / L.

8. The method for preparing the degradable polylipoic acid zwitterionic gel wireless strain sensor according to claim 8, characterized in that: The preparation steps of the preparation method are: a. Preparation of sodium lipoate: 1.7 g of sodium ethoxide and 5.15 g of lipoic acid were dissolved in 50 mL of anhydrous ethanol, then the sodium ethoxide solution was added dropwise to the lipoic acid (LA) solution, stirred for 12 h, centrifuged, and vacuum dried to obtain yellow sodium lipoate (LANa) powder, which was stored at -20 °C; b. 240 mg LA and 140 mg LANa powder were added to 1 mL deionized water to form a LA / LANa mixed dispersion to prepare a PLL hydrogel prepolymer, which was stirred at 90°C until melted, SBMA was added, and the mixture was cooled at room temperature to obtain a Poly(LA-LANa-SBMA-n)(PLLS-n) hydrogel, i.e., the degradable polylipoic acid zwitterionic gel wireless strain sensor.

9. A degradable polylipoic acid zwitterionic gel wireless strain sensor, characterized in that: The gel wireless strain sensor is obtained by the preparation method of claim 1, 2 or 8.

10. An application of a degradable polylipoic acid zwitterionic gel wireless strain sensor, characterized in that: The gel wireless strain sensor prepared in claim 9 is integrated with a Bluetooth system to prepare a wireless wearable sensor.

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