An ionic liquid conductive hydrogel, and a preparation method and application thereof

Abstract

The application relates to an ionic liquid conductive hydrogel as well as a preparation method and application thereof, and belongs to the technical field of polymer hydrogels. The ionic liquid conductive hydrogel has a three-dimensional network structure formed by polyvinyl alcohol and poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT:PSS) treated by imidazole salt ionic liquid, wherein the imidazole salt ionic liquid is 1-ethyl-3-methyl imidazole acetate. The ionic liquid is introduced into the hydrogel system formed by PEDOT:PSS and polyvinyl alcohol as a dopant, freezing crosslinking, solvent replacement and salting-out technology are combined, and the mechanical and electrical properties of the hydrogel are synergistically controlled. The strain sensor prepared based on the ionic liquid conductive hydrogel has excellent tensile property and fatigue resistance, high mechanical strength, low hysteresis and repeatability, and can be widely applied to the wearable sensor field such as rehabilitation training of patients with hand dysfunction, human motion state sensing and interactive control.

Description

TECHNICAL FIELD

[0001] The present application relates to an ionic liquid conductive hydrogel, a preparation method and application thereof, in particular, application in many fields such as human health monitoring, soft robot and wearable device, and belongs to the technical field of polymer hydrogel. BACKGROUND

[0002] With the rapid development of modern rehabilitation medicine and intelligent wearable technology, flexible wearable rehabilitation training devices have been widely used in the training of patients with hand dysfunction. Especially in the rehabilitation process of sequelae of cerebral apoplexy, post-traumatic hand dysfunction and senile degenerative diseases, early intervention and precise training of finger function become the key factors of rehabilitation effectiveness. Therefore, the demand for high-stretch, super-tough and low-hysteresis rehabilitation auxiliary devices in the current clinical and family rehabilitation training process is increasing. However, traditional finger rehabilitation training devices are usually rigid and heavy, which makes the user's comfort and experience poor, limiting their widespread use in rehabilitation medicine. Most of the current flexible sensors still use rigid metal electrodes or conductive metal films as functional layers, which often have problems such as incompatible mechanical and electrical properties, mismatch between high mechanical strength and human tissues, and large hysteresis. Ionic conductive hydrogel has become a research hotspot in flexible electronic materials due to its excellent softness, biocompatibility and controllable mechanical and electrical properties.

[0003] However, the current reported hydrogel-based flexible electronic devices generally have low stretchability, weak tear resistance and large hysteresis, which limits their practical application in high-frequency dynamic monitoring such as human motion monitoring and rehabilitation training detection. Therefore, it is urgent to develop an ionic liquid conductive hydrogel material with high stretchability, super toughness and low hysteresis. SUMMARY

[0004] In view of the problems of poor mechanical properties, short fatigue life and large hysteresis of the existing flexible strain sensor, the present application provides a preparation method and application of an ionic liquid conductive hydrogel. Specifically, an ionic liquid (ILs) is introduced into the hydrogel system of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) and polyvinyl alcohol (PVA) as a dopant, and the mechanical and electrical properties of the hydrogel are synergistically controlled by solvent replacement and salting-out technology. The strain sensor prepared based on the ionic liquid conductive hydrogel exhibits excellent stretchability, high mechanical strength, excellent fatigue resistance, low hysteresis and good repeatability, and can be widely used in the fields of wearable sensors such as rehabilitation training of patients with hand dysfunction and human motion state sensing and interactive control.

[0005] The technical scheme of the present application is as follows:

[0006] An ionic liquid conductive hydrogel has a three-dimensional network structure formed by polyvinyl alcohol and poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT:PSS) treated with an imidazole-based ionic liquid, wherein the imidazole-based ionic liquid is 1-ethyl-3-methylimidazolium acetate.

[0007] Further, the imidazole salt ionic liquid, as a dopant, on one hand, induces phase separation of poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid to enhance conductivity, and on the other hand, forms a hydrogen bond interaction with polyvinyl alcohol to reduce the crosslinking density of polyvinyl alcohol.

[0008] Further, the PEDOT:PSS treated with the imidazole salt ionic liquid is an ILs-PEDOT:PSS aqueous dispersion obtained by fully mixing the imidazole salt ionic liquid and the PEDOT:PSS aqueous dispersion by using a push-pull syringe method.

[0009] Further, the push-pull syringe method is to place the imidazole salt ionic liquid and the PEDOT:PSS aqueous dispersion in two syringes respectively, connect the luer adapters, and alternately push 150-200 times.

[0010] The present application provides a preparation method of the above-mentioned ionic liquid conductive hydrogel, comprising the following steps: mixing the imidazole salt ionic liquid and the PEDOT:PSS aqueous dispersion by using a push-pull syringe method to obtain an ILs-PEDOT:PSS aqueous dispersion; then mixing the ILs-PEDOT:PSS aqueous dispersion with a polyvinyl alcohol aqueous solution, and obtaining an ILs-PEDOT:PSS-PVA precursor by ultrasonicating and vigorously stirring for 20-30 min; and then performing a freeze-thaw step, and repeating the freeze-thaw step for 2-3 times to obtain the ionic liquid conductive hydrogel.

[0011] In the above technical solution, the mass concentration of the PEDOT:PSS aqueous dispersion is 7.4 wt.%.

[0012] In the above technical solution, the mass concentration of the polyvinyl alcohol aqueous solution is 10 wt.%.

[0013] Further, the preparation process of the polyvinyl alcohol aqueous solution is as follows: placing polyvinyl alcohol in deionized water, heating and stirring in a water bath at 90°C, and obtaining the polyvinyl alcohol aqueous solution.

[0014] Preferably, the mass ratio of the imidazole salt ionic liquid to the PEDOT:PSS aqueous dispersion is 1.3:2.7.

[0015] Preferably, the mass ratio of the ILs-PEDOT:PSS aqueous dispersion to the polyvinyl alcohol aqueous solution is 1:2-9.5.

[0016] Preferably, the freeze-thaw condition is freezing at -20℃ for 8 hours and thawing at room temperature for 3 hours, and the number of repetitions is 3.

[0017] In the technical solution, the preparation method further comprises a binary solvent replacement treatment and a salting-out treatment.

[0018] Further, the binary solvent replacement treatment specifically comprises soaking the obtained hydrogel in a glycerol / ethanol binary solvent for 4-5 hours, drying at room temperature for 5 hours, and then placing the hydrogel in deionized water until saturation is reached, wherein the volume ratio of glycerol to ethanol in the glycerol / ethanol binary solvent is 1:1-4.

[0019] Further, the salting-out treatment specifically comprises soaking the obtained hydrogel in a salt solution until saturation is reached, wherein the salt solution is a 0.5-2 mol / L sodium citrate solution.

[0020] Preferably, the volume ratio of glycerol to ethanol in the glycerol / ethanol binary solvent is 1:4.

[0021] Preferably, the salt solution is a 1 mol / L sodium citrate solution.

[0022] Preferably, the obtained hydrogel is soaked in the salt solution for 12 hours.

[0023] The application also provides a high-stretch, super-tough, and low-hysteresis ionic liquid conductive hydrogel, which is obtained by subjecting the ionic liquid conductive hydrogel to the above-mentioned binary solvent replacement treatment and the above-mentioned salting-out treatment.

[0024] Further, the stretch rate of the hydrogel is 656%-1336%, the toughness is 21.2-68 MJ m -3 , and the conductivity is 0.45-2.4 S / m.

[0025] Further preferably, the stretch rate of the hydrogel is 1140%, the toughness is 54 MJ m -3 , and the conductivity is 2.4 S / m.

[0026] Preferably, one of the technical solutions of the application comprises the following steps:

[0027] (1) Polyvinyl alcohol is added to deionized water, and stirred in a 90℃ hot water bath for 1-2 hours to obtain a transparent and viscous PVA solution;

[0028] (2) PEDOT:PSS and deionized water are placed in two syringes, connected by a luer joint in the middle, and then the needle tubes are pushed alternately 200-300 times to prepare a PEDOT:PSS aqueous dispersion;

[0029] (3) PEDOT:PSS aqueous dispersion and imidazole salt ionic liquid are respectively placed in two syringes, connected with luer joint, and pushed 150-200 times alternately to obtain ILs-PEDOT:PSS aqueous dispersion;

[0030] (4) PVA solution and ILs-PEDOT:PSS aqueous dispersion are placed in a beaker, and are stirred under a numerical control ultrasonic generator to obtain uniformly mixed ILs-PEDOT:PSS-PVA precursor solution;

[0031] (5) The ILs-PEDOT:PSS-PVA precursor solution is poured into a PMMA mold, and then is placed in a-20℃ refrigerator for freezing, and is thawed at room temperature, and the freezing-thawing step is repeated to obtain ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A;

[0032] (6) The ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A is soaked in a glycerol / ethanol binary solvent, and is dried at room temperature and then placed in deionized water until saturation is reached to obtain ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel B;

[0033] (7) The ionic liquid conductive hydrogel obtained after drying in step (6) is soaked in a sodium citrate solution until saturation is reached to obtain ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel C.

[0034] The stirring operation in the above step (1) is preferably completed in a heat collecting constant temperature magnetic stirrer.

[0035] The above ionic liquid conductive hydrogel is applied as a sensing unit in human health monitoring, soft robot or wearable device.

[0036] The application further provides an ionic liquid conductive hydrogel-based flexible strain sensor, comprising the above provided ionic liquid conductive hydrogel, further comprising VHB tape and copper wires; the ionic liquid conductive hydrogel serves as a sensing layer, copper wires are respectively installed at both ends of the ionic liquid conductive hydrogel, and then the VHB tape is used for packaging.

[0037] The application provides application of the above ionic liquid conductive hydrogel-based flexible strain sensor in rehabilitation training of patients with hand dysfunction.

[0038] The application also provides a sensing glove capable of monitoring finger bending data in real time, comprising the ion liquid conductive hydrogel-based flexible strain sensor provided in the above, and further comprising a textile glove, a VHB tape and an ESP32 microcontroller; the flexible strain sensor is attached to the middle joint part of the textile glove through the VHB tape, and the analog input interface of the ESP32 microcontroller is connected with the copper wire of the flexible strain sensor.

[0039] Specifically, the flexible strain sensor made of the ion liquid conductive hydrogel is taken as a strain sensing unit, integrated on a textile glove, prepared into a 5-channel data sensing glove, and connected to the analog input interface of the ESP32 microcontroller through a copper wire. When the hydrogel is strained with the bending of fingers or joints, the resistance value changes, and the change can be converted into a voltage signal input to the ADC channel of the ESP32 through the constructed partial pressure circuit. The program written on the Arduino platform is burned, including core function modules such as ADC data acquisition, data caching, Bluetooth communication initialization and data packaging and sending. The ESP32 works in the Bluetooth low power consumption mode, encapsulates the real-time collected voltage data as BLE characteristic values and sends them to the remote host through a wireless link. The computer end is taken as a BLE center end, runs a data receiving program based on Python, establishes a connection with the ESP32 through a serial Bluetooth module and continuously receives the hydrogel sensing signal. The program can realize real-time waveform display, data storage, strain-time curve drawing, and supports further data preprocessing such as filtering, normalization and gesture signal feature extraction for deep learning models.

[0040] The imidazole salt ionic liquid and poly(3,4-ethylenedioxythiophene): polystyrene sulfonate are uniformly dispersed by the push needle tube method, and then fully mixed with polyvinyl alcohol under ultrasonic conditions to obtain a stable ionic conductive polymer dispersion liquid. The physical crosslinking of the PVA chain is induced by freeze-thaw cycle, and the water gel micro network density and pore structure are adjusted by solvent replacement and salting-out treatment. The doping of the imidazole salt ionic liquid promotes the synergistic construction of the PEDOT:PSS conductive network and the PVA support, not only enhances the overall mechanical strength of the composite hydrogel, but also significantly improves the conductive performance and structural stability. In addition, sodium citrate is introduced as a functional auxiliary agent to strengthen the mechanical toughness and strain durability of the hydrogel by Hofmeister effect. The ionic liquid conductive hydrogel material obtained by the application exhibits excellent tensile property, high toughness, low hysteresis response characteristics and stable conductivity. Based on the above performance advantages, it is integrated in a glove for real-time monitoring of finger bending behavior. The system can be widely applied in the fields of wearable sensors such as rehabilitation training of patients with hand dysfunction, human motion state sensing and interactive control.

[0041] The application has the following beneficial effects:

[0042] The application realizes the construction of conductive hydrogel with high tensile property, super high toughness and low hysteresis response characteristics by introducing functional ionic liquid to systematically regulate the molecular interaction mechanism between PEDOT:PSS and PVA, thereby significantly improving the mechanical and electrical properties. After the introduction of ionic liquid as a functional additive into the hydrogel network, the orientation arrangement and pi-pi stacking conformation of the PEDOT segment can be promoted at the molecular level, thereby improving the effective path of electron transfer between PEDOT:PSS conductive polymer chains and significantly improving the electronic conductivity of the hydrogel. At the same time, the ions in the ionic liquid (such as EMIM + 、Ac - ) can form multiple hydrogen bond forces with the PVA molecular chain, thereby enhancing the crosslinking density and stability of the three-dimensional network structure of the hydrogel. The physical and chemical synergistic crosslinking effect improves the tensile property, toughness and fatigue resistance of the hydrogel, so that it can maintain structural integrity and functional stability after multiple cycle stretching or bending, meeting the demand for high flexibility and rapid recovery materials in wearable devices.

[0043] In addition, the ionic liquid mentioned in the application as a dopant has a good adjusting effect on the PEDOT:PSS-PVA hydrogel system and can be applied to similar polymer materials. Not only does it break through the technical bottleneck of traditional hydrogel "soft but not tough", but also expands its application prospects in high-end fields such as intelligent sensing, soft robot, rehabilitation medicine, etc., with obvious innovation and practicality, providing strong technical support for the invention patent. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The stress-strain curve of the ionic liquid conductive hydrogel prepared in Example 1 is shown in the figure.

[0045] Figure 2 The conductivity data graph of the ionic liquid conductive hydrogel prepared in Example 1 is shown in the figure.

[0046] Figure 3 The conductivity data graph of the ionic liquid conductive hydrogel (ILs-PEDOT:PSS-PVA) prepared in Example 3 and the hydrogel (PEDOT:PSS-PVA) without adding ionic liquid is shown in the figure.

[0047] Figure 4 The Raman spectrum of the ionic liquid conductive hydrogel (ILs-PEDOT:PSS-PVA) prepared in Example 3 and the hydrogel (PEDOT:PSS-PVA) without adding ionic liquid is shown in the figure.

[0048] Figure 5Figure showing the binding energy results of the ionic liquid conductive hydrogel prepared in Example 3 and the hydrogel without the addition of ionic liquid, where PVA-PVA refers to polyvinyl alcohol-polyvinyl alcohol, and PVA-Anion refers to polyvinyl alcohol-anion.

[0049] Figure 6 Figure showing the mechanical property results of the ionic liquid conductive hydrogel prepared in Example 5 after replacement in different proportions of glycerol / ethanol binary solvents, where PVA hydrogel refers to the hydrogel without glycerol / ethanol binary solvent and salting-out treatment, S-PVA hydrogel refers to the hydrogel without glycerol / ethanol binary solvent but with salting-out treatment, and ES-PVA hydrogel refers to the hydrogel with glycerol / ethanol binary solvent and salting-out treatment.

[0050] Figure 7 Figure showing the stress-strain curves of the ionic liquid conductive hydrogel prepared in Example 6 after immersion in different concentrations of sodium citrate solution.

[0051] Figure 8 Figure showing the preparation flowchart of the ionic liquid conductive hydrogel prepared in Example 6.

[0052] Figure 9 Figure showing the stress-strain curves, Young's modulus, and toughness data of the ionic liquid conductive hydrogel prepared in Examples 3, 5, and 6, where ILs-PEDOT:PSS-PVA, E-ILs-PEDOT:PSS-PVA, and ES-ILs-PEDOT:PSS-PVA refer to the ionic liquid conductive hydrogels obtained in Examples 3, 5, and 6, respectively.

[0053] Figure 10 Figure showing the fatigue threshold curve of the ionic liquid conductive hydrogel prepared in Example 6.

[0054] Figure 11 Figure showing the relative resistance change of the ionic liquid conductive hydrogel-based flexible strain sensor prepared in Example 7 under different strains.

[0055] Figure 12 Figure showing the hysteresis results of the ionic liquid conductive hydrogel-based flexible strain sensor prepared in Example 7.

[0056] Figure 13 Figure showing the results of the ionic conductive liquid hydrogel-based flexible strain sensor prepared in Example 7 in finger bending motion detection.

[0057] Figure 14 Figure showing the results of the ionic conductive liquid hydrogel-based flexible sensor prepared in Example 7 in different human motion detection.

[0058] Figure 15The device of the sensing glove for real-time monitoring of finger bending data prepared in Example 8 is shown in the figure. The figure shows that 1 is the textile glove body, and 2 is the hydrogel.

[0059] Figure 16 The data acquisition diagram of the sensing glove for real-time monitoring of finger bending data prepared in Example 8 for different gestures is shown in the figure. DETAILED DESCRIPTION

[0060] The following non-limiting examples can make those skilled in the art more fully understand the present application, but do not limit the present application in any way.

[0061] The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0062] Example 1

[0063] A method for preparing an ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A, comprising the following steps:

[0064] (1) 3 g of polyvinyl alcohol (PVA) powder was added to 27 g of deionized water, and continuously stirred in a constant temperature stirring water bath at 90°C for 2 h, to obtain a viscous and transparent 10 wt.% PVA solution;

[0065] (2) 0.2 g of PEDOT:PSS particles and 2.5 g of deionized water were respectively placed in two syringes, connected by a luer adapter in the middle, and then the needle tubes were pushed alternately 200 times to obtain a well-mixed 7.4 wt.% PEDOT:PSS aqueous dispersion;

[0066] (3) 1.3 g of 1-ethyl-3-methylimidazole acetate and 2.7 g of 7.4 wt.% PEDOT:PSS aqueous dispersion were mixed according to the needle tube pushing method described in step (2) to obtain a uniformly dispersed ILs-PEDOT:PSS aqueous dispersion, and the solid content of PEDOT:PSS in the system was 5 wt.%;

[0067] (4) 1 g of ILs-PEDOT:PSS aqueous dispersion and 9.5 g of PVA solution were placed in a beaker and stirred vigorously under a numerical control ultrasonic generator for 20 min to obtain a completely mixed 5 wt.% ILs-PEDOT:PSS-PVA precursor solution;

[0068] (5) Pour the ILs-PEDOT:PSS-PVA precursor solution into the acrylic mold, freeze at -20 °C for 8 h, then thaw at room temperature for 3 h, repeat the freezing-thawing for 3 times, and obtain the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A.

[0069] Example 2

[0070] The difference between this example and Example 1 is that in step (4), 2 g of ILs-PEDOT:PSS aqueous dispersion and 9 g of PVA solution are placed in a beaker and stirred vigorously under a numerical control ultrasonic generator for 20 min to obtain a completely mixed 10 wt.% ILs-PEDOT:PSS-PVA precursor solution.

[0071] Example 3

[0072] The difference between this example and Example 1 is that in step (4), 3 g of ILs-PEDOT:PSS aqueous dispersion and 8.5 g of PVA solution are placed in a beaker and stirred vigorously under a numerical control ultrasonic generator for 20 min to obtain a completely mixed 15 wt.% ILs-PEDOT:PSS-PVA precursor solution.

[0073] Example 4

[0074] The difference between this example and Example 1 is that in step (4), 2 g of ILs-PEDOT:PSS aqueous dispersion and 4 g of PVA solution are placed in a beaker and stirred vigorously under a numerical control ultrasonic generator for 20 min to obtain a completely mixed 20 wt.% ILs-PEDOT:PSS-PVA precursor solution.

[0075] Result analysis:

[0076] Reference Figure 1 and Figure 2 The ionic liquid conductive hydrogel in Example 1 of the present application can realize the adjustable tensile properties and conductivity of the ionic conductive hydrogel by changing the solid content of the ILs-PEDOT:PSS aqueous dispersion. From Figure 1 and Figure 2As can be seen from the above table, with the increase of the solid content of ILs-PEDOT:PSS, the elongation at break of the ILs-PEDOT:PSS-PVA hydrogel first increases and then decreases, and the stress gradually increases; at the same time, with the increase of the solid content of ILs-PEDOT:PSS, the conductivity of the ILs-PEDOT:PSS-PVA hydrogel gradually increases. In combination with the mechanical and electrical properties of the ILs-PEDOT:PSS-PVA hydrogel, the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel prepared when the mass concentration of ILs-PEDOT:PSS is 15 wt.% has the best performance.

[0077] 1.3 g of 1-ethyl-3-methylimidazole acetate in Example 3 is replaced by 1.3 g of H2O solution, and the rest of the operation is the same as that in Example 3 to prepare a hydrogel named PEDOT:PSS-PVA conductive hydrogel. Figure 3 For the conductivity data graph of the PEDOT:PSS-PVA conductive hydrogel and the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A obtained in Example 3, it can be seen that the introduction of the ionic liquid can significantly enhance the conductivity of the PEDOT:PSS-PVA hydrogel. Figure 4 For the Raman spectrum graph of the PEDOT:PSS-PVA conductive hydrogel and the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A obtained in Example 3, the conformational change of the PEDOT molecular chain is studied, and it can be seen that after the introduction of the ionic liquid, the C α = C β stretching vibration peak of the thiophene ring corresponding to PEDOT is shifted and the peak width is narrowed, indicating the structural transition of PEDOT from the phenolic configuration to the quinone configuration. The quinone configuration has higher intrachain conjugation and molecular chain flatness, which can effectively reduce the carrier migration energy barrier, promote the interchain π-π stacking and charge delocalization, and finally improve the transmission efficiency of electrons in the PEDOT chain and between the chains. Figure 5 For the binding energy result graph of PVA-PVA and PVA-Anion in the PEDOT:PSS-PVA conductive hydrogel and the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A obtained in Example 3, the binding energy between the ionic liquid and PVA is calculated by molecular dynamics simulation, and it can be seen that the binding energy between the anion in the ionic liquid and the PVA chain hydroxyl group is greater than the binding energy between the hydroxyl groups in the PVA molecular chain, thereby reducing the entanglement of the PVA chain in the freeze-thaw process and reducing the crystalline domain.

[0078] Example 5

[0079] A preparation method of an ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel B, comprising the following steps:

[0080] (1) 3 g polyvinyl alcohol (PVA) powder was added into 27 g deionized water, and stirred continuously for 2 h in a constant temperature stirring water bath at 90 °C, finally a viscous transparent 10 wt.% PVA solution was obtained;

[0081] (2) 0.2 g PEDOT:PSS particles and 2.5 g deionized water were placed in two syringes respectively, connected with a luer adapter in the middle, then the needle tubes were pushed alternately for 200 times, a well-mixed 7.4 wt.% PEDOT:PSS aqueous dispersion was obtained;

[0082] (3) 1.3 g 1-ethyl-3-methylimidazolium acetate and 2.7 g 7.4 wt.% PEDOT:PSS aqueous dispersion were mixed according to the needle tube pushing method described in step (2), a well-dispersed ILs-PEDOT:PSS aqueous dispersion was obtained, and the solid content of PEDOT:PSS in the system was 5 wt.%;

[0083] (4) 3 g ILs-PEDOT:PSS aqueous dispersion and 8.5 g PVA solution were placed in a beaker, and stirred vigorously under a numerical control ultrasonic generator for 30 min, a completely mixed ILs-PEDOT:PSS-PVA precursor solution was obtained;

[0084] (5) The ILs-PEDOT:PSS-PVA precursor solution was poured into a acrylic mold, frozen at -20 °C for 8 h, then thawed at room temperature for 3 h, the freezing-thawing cycle was repeated for 3 times, and an ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel A was obtained;

[0085] (6) The ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel A was soaked in a glycerol / ethanol binary solvent (V 甘油 :V 乙醇 =1 : 4) for 5 h, then dried at room temperature for 5 h, the dried ILs-PEDOT:PSS / PVA hydrogel was placed in deionized water until saturated, and an ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel B was obtained.

[0086] Result analysis: The mechanical property results of ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A after replacement with different proportions of glycerol / ethanol binary solvent are shown in Table 1. Figure 6As shown, it can be seen that the mechanical properties of the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A gradually increase with the increase of the ethanol content. The reason is mainly because the binary solvent replaces the free water in the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel A, so that the hydrogel contains a large amount of ethanol and glycerol, and at room temperature, the glycerol maintains the softness of the hydrogel, and the ethanol is volatilized, thereby reducing the network pores of the hydrogel and enhancing the mechanical strength of the hydrogel.

[0087] Example 6

[0088] A preparation method of an ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel C, comprising the following steps:

[0089] (1) 3 g of polyvinyl alcohol (PVA) powder was added to 27 g of deionized water, and continuously stirred in a constant temperature stirring water bath at 90°C for 2 h, to obtain a viscous and transparent 10 wt.% PVA solution;

[0090] (2) 0.2 g of PEDOT:PSS particles and 2.5 g of deionized water were respectively placed in two syringes, connected by a luer joint in the middle, and then the needle tubes were pushed alternately 200 times to obtain a well-mixed 7.4 wt.% PEDOT:PSS aqueous dispersion;

[0091] (3) 1.3 g of 1-ethyl-3-methylimidazole acetate and 2.7 g of 7.4 wt.% PEDOT:PSS aqueous dispersion were mixed according to the needle tube pushing method described in step (2) to obtain a uniformly dispersed ILs-PEDOT:PSS aqueous dispersion, and the solid content of PEDOT:PSS in the system was 5 wt.%;

[0092] (4) 3 g of ILs-PEDOT:PSS aqueous dispersion and 8.5 g of PVA solution were placed in a beaker and stirred vigorously under a numerical control ultrasonic generator for 30 min to obtain a completely mixed ILs-PEDOT:PSS-PVA precursor solution;

[0093] (5) The ILs-PEDOT:PSS-PVA precursor solution was poured into a acrylic mold, frozen at -20°C for 8 h, then thawed at room temperature for 3 h, and the freezing-thawing was repeated for 3 times to obtain an ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel A;

[0094] (6) The ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel A was placed in a glycerol / ethanol binary solvent (V 甘油 :V 乙醇Immerse in 1:4) for 5 h, then dry at room temperature for 5 h. Place the dried ILs-PEDOT:PSS / PVA hydrogel in deionized water until saturation is achieved to obtain ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel B.

[0095] (7) Place the ILs-PEDOT:PSS / PVA hydrogel obtained after drying in step (6) into a 1 mol / L sodium citrate solution until saturation is reached to obtain ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel C with high tensile strength, super toughness and low hysteresis.

[0096] Results Analysis: After placing hydrogel B in sodium citrate solution, the mechanical strength of the hydrogel increased, as shown in the following results. Figure 7 As shown, it can be seen that the stress of ILs-PEDOT:PSS / PVA ionic liquid conductive hydrogel B gradually increases with the increase of sodium citrate solution concentration. The main mechanism is that sodium citrate solution strongly associates with water molecules. In sodium citrate solution, its osmotic pressure is much greater than that of the solvent in the hydrogel, which leads to water expulsion and shrinkage of the hydrogel, thus increasing its mechanical strength.

[0097] Example 6 provides an ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel prepared by a freezing-binary solvent displacement-salting-out method. The preparation process is as follows: Figure 8 As shown.

[0098] The hydrogels obtained in Examples 3, 5, and 6 were all based on an ILs-PEDOT:PSS-PVA precursor solution with a solid content of 15 wt.%. Example 5 involved a binary solvent displacement treatment based on Example 3, and Example 6 involved a salting-out treatment based on Example 5, resulting in a significant enhancement of the mechanical strength of the ILs-PEDOT:PSS-PVA hydrogel. The results are shown in [Figure number missing]. Figure 9 .

[0099] The ionic liquid conductive hydrogel prepared in Example 6 exhibited the highest mechanical strength. Based on this, the fatigue properties of the hydrogel were investigated. The fatigue threshold was calculated using a single-notch test method, and the results are shown in [Figure Number]. Figure 10 It can be seen that the fatigue threshold of this ionic liquid conductive hydrogel is as high as 6.1 kJ / m. -2 .

[0100] An ionic liquid-induced bidirectional hydrogen bond enhancement strategy, combined with solvent displacement and salting-out techniques, produces an ionic liquid conductive hydrogel with high tensile strength and ultra-toughness, exhibiting significant fatigue resistance under cyclic stretching. The high-tensile, ultra-tough ionic conductive hydrogel obtained in this invention conforms to the laws governing human motion detection under high-frequency repeated stretching.

[0101] Example 7

[0102] A flexible strain sensor based on the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel C obtained in Example 6:

[0103] Preparation method: The ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel C obtained in Example 6 was wiped clean of surface moisture, copper wires were installed at both ends as conductive electrodes, and then packaged with VHB tape to obtain an ionic liquid conductive hydrogel-based flexible strain sensor.

[0104] Figure 11 The relative resistance change trend chart of the flexible strain sensor obtained in Example 7 under different tensile strains can be seen: as the tensile strain increases, the relative resistance value also increases. It is worth noting that the flexible strain sensor prepared by the present application can detect the relative resistance change in the range of small strain (10%~100%) and large strain (50%~300%).

[0105] Figure 12 The sensing signal hysteresis performance result chart of the flexible strain sensor obtained in Example 7 under 300% strain can be seen: the flexible strain sensor prepared by the present application has a relatively stable electrical signal under 300% stretching, good repeatability and low hysteresis (<1%), which is almost negligible.

[0106] Figure 13 The real-time detection result chart of the flexible strain sensor obtained in Example 7 for different degrees of finger bending can be seen: the sensing signal output can well distinguish the degree of finger bending, and the relative resistance value increases as the finger bending angle increases.

[0107] Figure 14 The real-time monitoring result chart of the flexible strain sensor obtained in Example 7 for different parts of the human body, such as the wrist, elbow and knee, can be seen: the ILs-PEDOT:PSS-PVA ionic liquid conductive hydrogel can respond to the joint movement of the human body in real time, and the relative resistance value increases as the joint movement amplitude increases.

[0108] Example 8

[0109] A sensing glove that can monitor finger bending data in real time, including an autonomous program for realizing data transmission and software and hardware joint control, the main hardware devices include the ionic liquid conductive hydrogel-based flexible sensor obtained in Example 7, a textile glove, VHB tape, an ESP32 module and a computer device, and the device schematic diagram is shown in Figure 15 .

[0110] Five identical conductive hydrogel-based flexible sensors obtained from the ionic liquid of Example 7 were attached to the middle joint of a textile glove by VHB tape to detect the resistance channel signals of finger bending angle and different gestures.

[0111] ESP32 module: burn the program based on Arduino platform, including ADC data acquisition, data caching, Bluetooth BLE communication initialization and data packaging and sending core function module. ESP32 works in Bluetooth low power (BLE) mode, encapsulates the resistance data collected in real time as BLE characteristic value and sends it to the remote host through wireless link. The computer end as the BLE center, runs the data receiving program based on Python, establishes connection with ESP32 through serial Bluetooth module and continuously receives the hydrogel electric signal. The program can realize real-time waveform display, data storage, strain-time curve drawing (see Figure 16 ), and supports further data preprocessing, such as filtering, normalization and gesture signal feature extraction for deep learning model.

[0112] In summary, the application uses ionic liquid as a dopant to synergistically regulate the mechanical and electrical properties of hydrogel, and the solvent replacement and salting-out post-processing method can effectively adjust the polymer network structure, thereby realizing the enhancement of the mechanical strength of the hydrogel, and further obtaining a high-stretch, super-tough and low-hysteresis hydrogel, which has broad application prospects in human motion detection and rehabilitation training, etc.

Claims

1. An ionic liquid conducting hydrogel, characterized in that: The hydrogel has a three-dimensional network structure formed by polyvinyl alcohol and poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT:PSS) treated by an imidazole salt ionic liquid, wherein the imidazole salt ionic liquid is 1-ethyl-3-methylimidazole acetate; The hydrogel is prepared by the following method: mixing the imidazole salt ionic liquid and the PEDOT:PSS aqueous dispersion by using a push needle tube method to obtain an ILs-PEDOT:PSS aqueous dispersion; then mixing the ILs-PEDOT:PSS aqueous dispersion with a polyvinyl alcohol aqueous solution, and stirring vigorously while ultrasonicating for 20-30 min to obtain an ILs-PEDOT:PSS-PVA precursor solution; and then performing a freeze-thaw step on the ILs-PEDOT:PSS-PVA precursor solution for 2-3 times to obtain the ionic liquid conductive hydrogel.

2. The ionic liquid electroconductive hydrogel according to claim 1, characterized in that: The PEDOT:PSS aqueous dispersion has a mass concentration of 7.4 wt.%; the polyvinyl alcohol aqueous solution has a mass concentration of 10 wt.%; the mass ratio of the imidazole salt ionic liquid to the PEDOT:PSS aqueous dispersion is 1.3:2.7; and the mass ratio of the ILs-PEDOT:PSS aqueous dispersion to the polyvinyl alcohol aqueous solution is 1:2-9.

5.

3. The ionic liquid electroconductive hydrogel according to claim 1, wherein: The preparation method further comprises a binary solvent replacement treatment, specifically, immersing the obtained hydrogel in a glycerol / ethanol binary solvent for 4-5 h, drying at room temperature for 5 h, and then placing the hydrogel in deionized water until saturation is reached, wherein the volume ratio of glycerol to ethanol in the glycerol / ethanol binary solvent is 1:1-4.

4. The ionic liquid electroconductive hydrogel according to claim 3, characterized in that: The preparation method further comprises a salting-out treatment, specifically, immersing the obtained hydrogel in a salt solution until saturation is reached, wherein the salt solution is a 0.5-2 mol / L sodium citrate solution.

5. The ionic liquid electroconductive hydrogel according to claim 4, wherein: The tensile rate of the hydrogel is 656%~1336%, the toughness is 21.2~68 MJ m -3 , and the conductivity is 0.45~2.4 S / m.

6. An ionic liquid conductive hydrogel-based flexible strain sensor, characterized in that: The sensor comprises the ionic liquid conductive hydrogel of any one of claims 1-5, further comprises a VHB tape and copper wires; the ionic liquid conductive hydrogel serves as a sensing layer, and the copper wires are respectively mounted at both ends of the sensing layer, and then the sensing layer is packaged using the VHB tape.

7. A sensing glove capable of monitoring finger flexion data in real time, characterized by: The sensing glove comprises the ionic liquid conductive hydrogel-based flexible strain sensor of claim 6, further comprises a textile glove, a VHB tape and an ESP32 microcontroller; the flexible strain sensor is attached to the middle joint part of the textile glove through the VHB tape, and the analog input interface of the ESP32 microcontroller is connected to the copper wires of the flexible strain sensor.

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