CN115894966A - Solution-regulated modified ion-conductive hydrogel and preparation method and application thereof - Google Patents

Abstract

The invention provides a solution-regulated modified ion-conductive hydrogel and a preparation method and application thereof, wherein the preparation method of the solution-regulated modified ion-conductive hydrogel comprises the following steps: adding a PVA aqueous solution into a carboxylated chitosan solution, adding acrylamide, a water-soluble initiator and a covalent cross-linking agent, mixing and stirring, and heating to react to obtain a hydrogel precursor; repeatedly and circularly freezing the hydrogel precursor to obtain a triple-network hydrogel matrix; and (3) aging the completely swollen triple-network hydrogel matrix, placing the matrix into water immersion liquid containing lithium chloride and glycerol for ion exchange, and taking out the matrix. The preparation method realizes the monitoring of double signals by separating the temperature-mechanical signals within a certain temperature range in a delayed manner, and the flexible sensor after subsequent assembly can simultaneously monitor the motion of a human body and the temperature of the skin.

Description

Solution-regulated modified ion-conductive hydrogel and preparation method and application thereof

Technical Field

The invention relates to the field of preparation of ionic conductive hydrogel, and particularly relates to solution-regulated modified ionic conductive hydrogel and a preparation method and application thereof.

Background

In recent years, with the rapid development of the internet and the internet of things, flexible sensors have gradually become a research hotspot due to the characteristics of high sensitivity, quick response, portability, comfort and the like, the application in the fields of emerging smart homes, wearable equipment, smart mobile terminals and the like is rapidly advanced, the application space is greatly expanded, and the country pays more attention to the application, develops a series of policies and supports the development of the flexible sensor industry. The flexible sensor overcomes the defect that the traditional rigid electronic sensor is hard and brittle, has better flexibility, ductility, sensitivity and smaller volume, converts parameters in the environment such as temperature, humidity, pressure, deformation and the like into electric signals by detecting the parameters, and has important significance for meeting the increasing requirements of bioelectronics, electronic skins, health monitoring and other modern electronic equipment.

Different from the traditional flexible conductive material, the conductive hydrogel has a network structure similar to natural biological tissues, shows similar mechanical properties and physiological characteristics to human skin and organs, and becomes one of ideal carriers of human-computer interfaces. The main strategy to impart electrical conductivity to hydrogels is to introduce electrical conductivity into the material, mainly classified into electronically conductive hydrogels and ionically conductive hydrogels.

The electronic conductive hydrogel realizes electric conduction by directional movement of free electrons in the hydrogel under the action of an electric field, and the preparation method of the electronic conductive hydrogel mainly comprises the following two steps: firstly, conducting polymers are used as monomers to construct a conducting hydrogel network, and the conducting polymers can form the conducting hydrogel network through covalent bonds or a physically crosslinked hydrophilic structure; and secondly, introducing electron conductive nano materials such as graphene, carbon nano tubes, silver nano wires and the like into the hydrogel. However, for hydrogels with doped electronically conductive materials, the conductive material in the system cannot withstand as much strain as the hydrogel network matrix during deformation. When the deformation is too large, irreversible separation can occur between the connected conductive polymer networks or the bridged nano materials, so that the conductivity of the system is remarkably reduced and is difficult to recover.

In order to adapt to the application of sensors and energy storage directions and widen the application range of the hydrogel, the ion-conductive hydrogel attracts the attention of researchers. When the hydrogel is deformed in a certain direction scale under pressure, the distance of the upper end surface in the direction is changed, so that the ion movement distance is changed, and the resistance is changed along with the change; the shape of the hydrogel is recovered after the pressure is removed, and the resistance value is recovered; in addition, compared with hydrogel coated or doped with an electronic conductive material, the ionic conductive hydrogel has higher biocompatibility, so that the ionic conductive hydrogel has potential application in the field of biomedicine.

However, in the prior art, there are many preparation methods for ion-conducting hydrogel flexible strain and pressure sensors, but the problems of many preparation raw materials, complex preparation process and low production efficiency generally exist, and the functional application aspect of the hydrogel composite material is single, so that the application value is not high.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a preparation method of solution regulation and control modified ion-conducting hydrogel, which prepares a sensor capable of meeting the pressure-temperature dual-signal sensing requirement by modifying a conducting phase and a solvent phase in a high-strength multi-network hydrogel system solution and relying on an adjustable ion-conducting signal, thereby not only improving the durability of the sensor in the practical application environment process, but also having important research significance and practical application value in the aspects of multifunction and application of hydrogel composite materials.

The second purpose of the invention is to provide the solution-regulated modified ion-conductive hydrogel prepared by the preparation method, the hydrogel material has linear sensitivity in a pressure range of 0-9kPa through solution regulation, and the coefficient can reach 4.165kPa ^-1 The material has good multi-cycle stability and restorability, shows linear change of resistance signals in a temperature range of 25-50 ℃, has sensitivity reaching 2.042%/DEG C, and improves the further application value of the material.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

the invention provides a preparation method of solution-regulated modified ion-conductive hydrogel, which comprises the following steps:

adding a PVA aqueous solution into a carboxylated chitosan solution, adding acrylamide, a water-soluble initiator and a covalent cross-linking agent, mixing and stirring, and heating to react to obtain a hydrogel precursor;

repeatedly and circularly freezing the hydrogel precursor to obtain a triple-network hydrogel matrix;

and (3) aging the completely swollen triple-network hydrogel matrix, placing the matrix into water immersion liquid containing lithium chloride and glycerol for ion exchange, and taking out the matrix.

Although glycerin can play a role in maintaining the humidity of the hydrogel, if the glycerin is directly added by a one-pot method, the gelling effect of the hydrogel is affected, so that in order to avoid the situation, the scheme of the invention selects a mode of carrying out immersion after the hydrogel matrix is aged, thereby not only ensuring the humidity of the hydrogel, but also providing a new function of the conductive hydrogel through the preparation method, and improving the application value of the conductive hydrogel.

Preferably, as a further implementable solution, the water-soluble initiator is potassium persulfate, and the content is 0.2-0.5% of the mass of the acrylamide; the covalent cross-linking agent is N, N' -methylene-bisacrylamide, and the content of the covalent cross-linking agent is 0.1-0.3 percent of the mass of the acrylamide.

Preferably, as a further implementable solution, the PVA solution has a polyvinyl alcohol concentration of 10 to 12% by weight. Prepared by dissolving polyvinyl alcohol (molecular weight greater than 100000, degree of alcoholysis greater than 98% mol/mol) in deionized water at 90 ℃.

Preferably, as a further implementable aspect, the carboxylated chitosan solution has a solute concentration of 25 to 30wt%, the mass of citric acid consumed to the mass of chitosan being in a ratio of (1 to 1.25): 1.

preferably, as a further practicable aspect, in the solution for performing the heating reaction, the mass ratio of acrylamide, polyvinyl alcohol and chitosan is 3. The total mass fraction of the total solute is between 25 and 35 percent.

Preferably, as a further practicable scheme, the freezing temperature is-20 to-15 ℃, and the freezing time is 4 to 6 hours; the time for recovering to the normal temperature is equal to the freezing time; the number of freeze-thaw cycles is 3-5.

Preferably, as a further implementable solution, the temperature of the aging treatment is from 20 to 30 ℃.

Preferably, as a further implementable solution, the aging treatment time is 24 to 48h.

Preferably, as a further practical scheme, the molar concentration of lithium chloride in the water immersion liquid is 1.0-1.3mol/L.

Preferably, as a further implementable aspect, the water immersion liquid has a volume fraction of glycerol of 10-30%.

Preferably, as a further implementable aspect, the time for placing in the water immersion fluid for ion exchange is 48 hours or more.

In the steps of aging and subsequent soaking in water soaking solution, the operation parameters are practically optimized, so that the finally prepared ion-conductive hydrogel has the due performance.

The invention also provides the solution regulation and control modified ion-conducting hydrogel prepared by the method, and the ion-conducting hydrogel realizes monitoring of double signals by separating temperature-mechanical signals within a certain temperature range in a delayed manner.

In conclusion, the solution-regulated modified ion-conductive hydrogel prepared by the invention has good application in pressure-temperature dual-signal sensors. The double-signal sensor is a non-volume temperature-sensitive resistance type temperature-pressure double-signal sensor, and the assembly method of the resistance type double-signal flexible sensor is formed by attaching copper foils on two sides of a coin-shaped hydrogel and sealing the two sides of the coin-shaped hydrogel with VHB adhesive tapes after connecting with a lead.

Compared with the prior art, the invention has the following beneficial effects:

1) The invention adopts the polyacrylamide/chitosan/polyvinyl alcohol triple network hydrogel with covalent-physical composite crosslinking as a substrate, and constructs at least 4 crosslinking modes comprising chemical crosslinking of polyacrylamide, microcrystal of polyvinyl alcohol, hydrogen bond between chitosan and polyacrylamide, physical crosslinking of chitosan and the like to form the composite hydrogel with a stepped energy dissipation mechanism, thereby greatly improving the tensile and compressive strength of the hydrogel and reserving the recoverability of the hydrogel to enable the hydrogel to be used for assembling a flexible sensor;

2) The triple composite cross-linked network substrate structure has excellent stability, so that the triple composite cross-linked network substrate structure can be soaked in a solution for a long time to perform complete ion exchange to finish the accurate regulation and control of ion concentration and solvent type, and the solvent regulation and control in the process of preparing the multi-network structure hydrogel by a one-pot method are separated, so that the blocking effect of the solvent (such as glycerol and the like) on the cross-linking of a gel substrate in the whole reaction process is avoided;

3) The method for regulating and controlling the solution ensures that the prepared hydrogel sensor has linear sensitivity in the pressure range of 0-9kPa, and the coefficient can reach 4.165kPa ^-1 The method has the advantages of good multiple cycle stability and recovery; on the other hand, the solution regulation and control of the invention enables the hydrogel sensor to present linear change of resistance signals in the temperature range of 25-50 ℃, and the sensitivity reaches 2.042%/DEG C;

4) The hydrogel sensor prepared by the preparation method can be used for a long time in an environment exposed to air, and the water content in the system can be self-regulated according to the humidity of the environment;

5) After the hydrogel material is subsequently applied and assembled to form the dual-signal sensor, the sensor has obvious signal delay separation phenomenon under the condition of being stimulated by pressure and temperature signals at the same time, the pressure signal has instantaneity, the response time is less than 0.5s, the temperature signal has certain time delay, and the separation interval of complete response is more than 90 seconds; by utilizing the flexibility and the sensitivity to pressure and temperature, the wearable device is further assembled, and the physiological activities such as human joint movement, skin temperature and respiration can be monitored.

Drawings

Various additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 shows the pressure-resistance change curves between comparative examples 1, 3-4;

(a) A pressure-resistance change curve of 0 to 15 kPa; (b) A resistance retention rate curve at a temperature gradient of 20,30,40,50 ℃;

FIG. 2 is an image of the surface topography of each of the examples and comparative triple-network hydrogel matrices using a scanning electron microscope (SEM, zeiss Merlin Compact);

FIG. 3 is a graph of resistance change versus pressure for a pressure sensor in the range of 0-15 kPa;

FIG. 4 is a resistance retention rate-temperature curve in the range of 25 to 50 ℃;

FIG. 5 shows the change in various parameters and macro-topography after aging of the examples and comparative examples after exposure of a room temperature fume hood to an air environment;

wherein (a) water retention-aging time curve; (b) After entering a dehydration balance period, a water retention rate-aging time curve and corresponding environment relative humidity; (c) macroscopic morphology of hydrogels with different aging times; (d) A resistance retention rate-aging time curve and a corresponding ambient relative humidity;

FIG. 6 is a graph showing the change in resistance signal of example 1 under 100 constant pressure cycles of 2.5kPa and the change and recovery curves of the resistance signal under the stimulus of temperature signals of 50 ℃ and 37 ℃;

(a) Resistance retention rate change curve after 100 times of pressure cycle of 2.5 kPa; (b) The change and recovery curve of the resistance retention rate with time under the temperature signals of 37 ℃ and 50 ℃;

FIG. 7 is a graph showing the resistance signal under the temperature-pressure dual signal stimulation in example 1;

(a) No temperature signal but a pressure signal of 3kPa circulates; (b) cycling the pressure signals at different temperatures;

FIG. 8 shows the resistance signal variation curves for monitoring relevant parameters and movements of a human body after assembly of the flexible device of example 1;

(a) Bending the finger joints; (b) forehead skin temperature; (c) nape bending; (d) respiration and thoraco-abdominal skin temperature.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

Step 1: adding 10g of polyvinyl alcohol (PVA) into 90ml of deionized water, heating and stirring at 90 ℃ for 2 hours to completely dissolve the PVA to form a 10wt% PVA aqueous solution;

step 2: adding 10g of Chitosan (CS) into 350ml of deionized water, and stirring at 50 ℃ to form a suspension; maintaining the stirring state, and gradually adding 12g of citric acid until the citric acid is completely carboxylated and dissolved to form a transparent solution;

and step 3: sequentially adding the PVA solution obtained in the step 1 and 30g of acrylamide (AAm) into the solution obtained in the step 2, and uniformly stirring at 60 ℃ until all components are completely dissolved; then sequentially adding 120mg of initiator potassium persulfate and 30mg of cross-linking agent N, N' -methylene-bisacrylamide, violently stirring for 2 minutes, quickly transferring the mixture into a mold for sealing, and putting the sealed mold into a thermostat at 60 ℃ for reacting for 5 hours to obtain a composite hydrogel precursor;

and 4, step 4: cooling the precursor obtained in the step 3 to room temperature, and then performing freeze-thaw cycle treatment for 4 times, wherein the freezing temperature is-16 ℃, and the freezing time is 5 hours; unfreezing for 5 hours at room temperature; aging in a fume hood at room temperature of 30 deg.C for 48 hr;

and 5: preparing a water/glycerol solution of lithium chloride, wherein the concentration of the lithium chloride is 1mol/L, and the volume fraction of the glycerol is 30%;

step 6: and (4) placing the aged hydrogel in the step 4 into the impregnation liquid in the step 5 for ion exchange for 48 hours.

Example 2

The other operation steps were identical to those of example 1 except that the lithium chloride concentration in the solution in step 5 of example 1 was maintained at 1mol/L, the volume fraction of glycerin was adjusted to 10%, and the remaining steps were unchanged.

Example 3

The other steps were identical to those of example 1 except that the lithium chloride concentration in the solution of step 5 of example 1 was maintained at 1mol/L, the volume fraction of glycerin was adjusted to 20%, and the remaining steps were not changed.

Example 4

Step 1: adding 10g of polyvinyl alcohol (PVA) into 90ml of deionized water, heating and stirring at 90 ℃ for 2 hours to completely dissolve the PVA to form a 12wt% PVA aqueous solution;

and 2, step: adding 10g of Chitosan (CS) into 320ml of deionized water, and stirring at 50 ℃ to form a suspension; maintaining the stirring state, and gradually adding 125g of citric acid until the citric acid is completely carboxylated and dissolved to form a transparent solution;

and step 3: sequentially adding the PVA solution obtained in the step 1 and 30g of acrylamide (AAm) into the solution obtained in the step 2, and uniformly stirring at 60 ℃ until all components are completely dissolved; then, sequentially adding 120mg of initiator potassium persulfate and 30mg of cross-linking agent N, N' -methylene bisacrylamide, violently stirring for 2 minutes, quickly transferring to a mold for sealing, and putting the sealed mold into a thermostat at 60 ℃ for reacting for 5 hours to obtain a composite hydrogel precursor;

and 4, step 4: cooling the precursor obtained in the step 3 to room temperature, and then performing freeze-thaw cycle treatment for 5 times, wherein the freezing temperature is-20 ℃, and the freezing time is 6 hours; unfreezing for 5 hours at room temperature; aging in a fume hood at room temperature of 30 deg.C for 48 hr;

and 5: preparing a water/glycerol solution of lithium chloride, wherein the concentration of the lithium chloride is 1mol/L, and the volume fraction of the glycerol is 30%;

and 6: and (4) placing the aged hydrogel in the step 4 into the impregnation liquid in the step 5 for ion exchange for 48 hours.

Example 5

Step 1: adding 10g of polyvinyl alcohol (PVA) into 90ml of deionized water, heating and stirring at 90 ℃ for 2 hours to completely dissolve the PVA to form 11wt% of PVA aqueous solution;

step 2: adding 10g of Chitosan (CS) into 300ml of deionized water, and stirring at 50 ℃ to form a suspension; maintaining the stirring state, and gradually adding 100g of citric acid until the citric acid is completely carboxylated and dissolved to form a transparent solution;

and step 3: sequentially adding the PVA solution obtained in the step 1 and 30g of acrylamide (AAm) into the solution obtained in the step 2, and uniformly stirring at 60 ℃ until all components are completely dissolved; then, sequentially adding 120mg of initiator potassium persulfate and 30mg of cross-linking agent N, N' -methylene bisacrylamide, violently stirring for 2 minutes, quickly transferring to a mold for sealing, and putting the sealed mold into a thermostat at 60 ℃ for reacting for 5 hours to obtain a composite hydrogel precursor;

and 4, step 4: cooling the precursor obtained in the step 3 to room temperature, and then performing freeze-thaw cycle treatment for 3 times, wherein the freezing temperature is-15 ℃, and the freezing time is 4 hours; unfreezing at room temperature for 5 hours; aging in a fume hood at room temperature of 30 deg.C for 48 hr;

and 5: preparing a water/glycerol solution of lithium chloride, wherein the concentration of the lithium chloride is 1mol/L, and the volume fraction of the glycerol is 30%;

step 6: and (4) placing the aged hydrogel in the step 4 into the impregnation liquid in the step 5 for ion exchange for 48 hours.

Comparative example 1

The other steps are consistent with the example 1, except that the concentration of lithium chloride in the solution in the step 5 of the example 1 is kept at 1mol/L, the volume fraction of glycerol is adjusted to be 0 percent, and the other steps are not changed;

comparative example 2

The other steps are identical to those of example 1 except that the solution of step 5 of example 1 is directly replaced by deionized water and the remaining steps are unchanged.

Comparative example 3

The other steps were identical to those of example 1 except that the lithium chloride concentration in the solution in step 5 of example 1 was maintained at 0.5mol/L, the volume fraction of glycerin was adjusted to 0%, and the remaining steps were unchanged.

Comparative example 4

The other steps were identical to those of example 1 except that the lithium chloride concentration in the solution in step 5 of example 1 was maintained at 1.5mol/L, the volume fraction of glycerin was adjusted to 0%, and the remaining steps were unchanged.

Experimental example 1

The ionic conduction hydrogel prepared according to each example and comparative example is compared from different performance levels, and the specific experimental results are shown in figures 1-8.

As seen from fig. 1, the samples prepared in comparative examples 1,3,4 were first subjected to a pressure sensing test and a temperature sensitive area test for electrical conductivity, as shown in (a) and (b) of fig. 8, with respect to the selection of the concentration of the solution conductive phase LiCl.

The results of comparative examples 1,3,4 in which conductive phase LiCl was introduced in the pressure-resistance change test of 0-15kPa showed that the sensitivity coefficient increased as the concentration of LiCl in the system increased, and the sensitivity coefficients of comparative examples 1,3,4 in the range of 0-6kPa were 4.9548,3.9521 and 5.1592, respectively; on the other hand, the result of the temperature sensitive interval test shows that in the comparative example 3, the resistance change amplitude of the temperature interval from 20-50 ℃ is smaller due to the lower LiCl concentration in the system; in the comparative example 4, due to the fact that the LiCl concentration in the system is higher, the resistance change is greatly shown in the temperature range of 30-40 ℃, and the temperature sensitive point is shown in the range, but the resistance change rate is obviously reduced after the temperature is increased to 50 ℃, and signal sensing in the temperature range is not facilitated; the LiCl concentration content in the comparative example 1 is proper, the resistance change is relatively stable within the temperature range of 20-50 ℃, and the temperature-resistance sensing behavior regulation and control in the whole temperature range are facilitated. In conclusion, it is appropriate to select the conductive phase concentration of comparative example 1 as a reference for each example.

As can be seen in fig. 2, the samples were freeze-dried for 24 hours after being fully swollen in deionized water. All the hydrogel surface morphologies present complicated porosity, indicating that a three-dimensional cross-linked network structure exists, relatively dense pore channel distribution exists, the pore channel sizes are smaller, the pore channel wall surfaces are smoother and smoother, no rough structure appears, indicating the formation of a stable three-dimensional structure.

As can be seen from FIG. 3, the various embodiments exhibit a typical three-stage signal profile for a pressure sensor, with a significantly higher sensitivity at low pressures than at high pressures; fitting gave sensitivity coefficients of 4.1651kPa for examples 1 to 3 and comparative example 1, respectively, in the range of 0 to 6kPa ^-1 ，3.2749kPa ^-1 ，3.5425kPa ^-1 ，4.9548kPa ^-1 。

As can be seen from FIG. 4, all the examples and comparative example 1 have nearly linear distribution and the temperature sensitivity of the system increases with the increase of the content of glycerin, wherein the temperature sensitivity coefficient of example 1 can reach 2.042%/DEG C.

As can be seen in fig. 5, all examples reached equilibrium for moisture loss within 4 days, with comparative example 2 having lost almost all moisture; due to the strong hygroscopicity of lithium chloride, the moisture content of each of examples 1-3 and comparative example 1 is different from the moisture retention of comparative example 1, and the moisture content of each example can fluctuate with the change of the environmental humidity; due to the introduction of glycerol into the solvent, the increased vapor pressure can effectively prevent the evaporation of water in the system; similarly, the resistance value of each embodiment can fluctuate with small amplitude along with the change of the environmental humidity after long-time aging;

as seen in fig. 6, the pressure signal exhibits a transient response and a rapid recovery over multiple cycles, while the temperature signal exhibits a response and a slow recovery over a longer period of time;

the results shown in fig. 7 show that the resistance signal of the hydrogel sensor shows a stable cyclic change in the case of only pressure signal cycling; under the condition of simultaneously applying different temperature signals and pressure signals, the output resistance signals show transient mechanical signal response and delayed temperature signal response; the response of the mechanical signal is also instantaneous recovery after the dual signals are simultaneously removed, the response of the temperature signal is gradually recovered in a period of time, and the resistance signal curves show corresponding peak values at different temperatures and pressures.

Figure 8 contains finger joint movement away from the core of the body, forehead temperature, nape movement slightly closer to the core of the body, and respiratory behavior monitoring. The resistance signal curve of the knuckle movement shows typical single mechanical signal response behavior as far away from the core of the human body, and the neck bending movement monitoring shows that the whole resistance signal change has the trend of slightly decreasing along with the monitoring time except for stable single mechanical signal response, and the temperature of the corresponding nape is slightly higher than the room temperature; the monitoring result of the human forehead temperature with higher temperature shows that the sensor can achieve complete temperature signal response within 90-100s, and the forehead skin temperature obtained by linear fitting according to the resistance signal is 34.28 ℃. The resistance signal-time curve for monitoring the respiration of a human body shows that the sensor is attached to the skin between the chest and the abdomen of a volunteer, the mechanical signal response is very weak in the stable respiration stage, the obvious mechanical signal response is shown in the deep respiration stage, and the fluctuation range of the resistance change reaches 10%; meanwhile, temperature signal response is finished within 90-100s, the skin temperature at the chest-abdomen junction is obtained by fitting to be 30.68 ℃, respiratory motion and the chest-abdomen skin temperature can be monitored simultaneously, and a complex signal separation calculation process is avoided.

While particular embodiments of the present invention have been illustrated and described, it would be obvious that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims (10)

1. A preparation method of solution-regulated modified ion-conductive hydrogel is characterized by comprising the following steps:

adding a PVA aqueous solution into a carboxylated chitosan solution, adding acrylamide, a water-soluble initiator and a covalent cross-linking agent, mixing and stirring, and heating to react to obtain a hydrogel precursor;

repeatedly and circularly freezing the hydrogel precursor to obtain a triple-network hydrogel matrix;

and (3) aging the completely swollen triple-network hydrogel matrix, placing the matrix into water immersion liquid containing lithium chloride and glycerol for ion exchange, and taking out the matrix.

2. The method for preparing according to claim 1, wherein the temperature of the aging treatment is 20 to 30 ℃.

3. The method according to claim 1, wherein the aging time is 24 to 48 hours.

4. A preparation method according to claim 1, wherein the molar concentration of lithium chloride in the water immersion liquid is 1.0-1.3mol/L.

5. The method according to claim 1, wherein the water immersion liquid contains glycerin in an amount of 10 to 30% by volume.

6. The method according to claim 1, wherein the time for ion exchange in the aqueous immersion fluid is 48 hours or more.

7. The method according to claim 1, wherein the PVA solution has a polyvinyl alcohol concentration of 10 to 12wt%.

8. The method according to claim 1, wherein the carboxylated chitosan solution has a solute concentration of 25 to 30wt%, and the mass ratio of the consumed citric acid to the chitosan is (1 to 1.25): 1.

9. the solution-controlled modified ion-conducting hydrogel prepared by the preparation method of any one of claims 1 to 8.

10. The solution-controlled modified ion-conducting hydrogel prepared by the preparation method of any one of claims 1 to 8 and the application of the solution-controlled modified ion-conducting hydrogel of claim 9 in a pressure-temperature dual-signal sensor.

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