Underwater sensing conductive gel and preparation method and application thereof

Abstract

The invention belongs to the crossing field of biomedical engineering, material science and communication technology, and discloses an underwater sensing conductive gel and a preparation method and application thereof. The conductive gel disclosed by the invention is prepared from hexyltrimethyl ammonium bromide, silver nanoparticle loaded polydopamine nanoparticles, polyacrylic acid, gelatin and water. According to the invention, not only can underwater adhesion of various substrate materials be realized, but also durability and repeatability of adhesion performance can be realized. The conductive gel prepared by the method disclosed by the invention can be used for monitoring underwater human body movement and promoting the development of flexible wearable underwater sensing materials.

Description

Technical Field

[0001] The invention belongs to the intersecting field of biomedical engineering, material science and communication technology, and specifically relates to a conductive gel for underwater sensing and a preparation method and application thereof. Background Art

[0002] Conductive hydrogel is developing rapidly in the field of wearable sensing materials due to its unique conductivity, excellent softness, excellent stretchability and good biocompatibility. It has shown remarkable potential in many application scenarios, whether in the field of medical health monitoring, it can fit closely to human skin and accurately sense various physiological signals of the human body, such as heart rate, blood pressure, muscle movement, etc., to facilitate telemedicine and personal health management; or in sports assistance and monitoring, wearable conductive hydrogel sensors can track athletes' movements and muscle strength in real time, helping to optimize sports training and prevent sports injuries; or in the field of intelligent interaction, by sensing the subtle movements and touch of the human body, people and smart devices can achieve more natural and convenient interaction.

[0003] However, conductive hydrogels show significant differences in land and underwater application scenarios. On land, it has been widely used due to its own advantages and can perform sensing performance relatively stably. However, it faces many severe challenges when used underwater. Due to the interfacial diffusion phenomenon between hydrogels and water, hydrogels are very easy to swell in water environments. This may lead to structural deformation, deterioration of mechanical and adhesion properties, and distortion or interruption of the output signal as a sensor. Therefore, the stability of underwater environmental performance is destroyed, and it is impossible to achieve accurate and stable sensing on land, which seriously restricts its further application and development in the field of underwater wearable sensing. The underwater stability of mechanical properties, adhesion properties and sensing properties is the core performance for realizing the underwater application of conductive hydrogels. The development of a conductive hydrogel that can stably sense underwater is of great significance for the development of flexible wearable sensors for motion monitoring, physiological signal monitoring, and underwater communication in underwater sports such as swimming, diving and ocean exploration. Summary of the invention

[0004] In order to overcome the shortcomings and deficiencies in the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing a conductive gel for underwater sensing; the method constructs a Gelatin / PAA / PDA@Ag / HTAB hydrogel, in which acrylic acid (AA) and gelatin (Gelatin) help to improve the biocompatibility and tissue adhesion of the hydrogel.

[0005] Another object of the present invention is to provide a conductive gel for underwater sensing prepared by the above-mentioned preparation method; the conductive gel has the following characteristics: on the one hand, hexyltrimethylammonium bromide (HTAB) can stabilize the hydrophobic segments of polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles and form hydrophobic binding regions, which serve as physical cross-linking sites of the hydrogel network; on the other hand, the positively charged HTAB is attached to the negatively charged carboxyl groups on the PAA segments through strong electrostatic interactions, and further enhances the hydrophobicity of the hydrogel; in addition, the interaction between HTAB and PAA promotes the hydrophobicity of the hydrogel. + The dissociation of ions improves the ionic conductivity of the hydrogel; therefore, the hydrophilic groups in the conductive gel can destroy the hydration layer, and the hydrophobic groups are expelled from the hydration layer, thereby achieving the stability of underwater adhesion and mechanical properties, etc., and combined with the function of ion conduction, the underwater sensing function is realized.

[0006] Another object of the present invention is to provide an application of the above-mentioned conductive gel for underwater sensing.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a conductive gel for underwater sensing comprises the following steps:

[0009] (1) dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into an ethanol / water mixed solution of dopamine hydrochloride by a solution oxidation method, the pH value of the ethanol / water mixed solution of dopamine hydrochloride is adjusted with an alkali solution, the reaction is stirred, and the dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles, which are washed by centrifugation with a detergent, and freeze-dried to obtain polydopamine freeze-dried powder (PDA);

[0010] (2) using a reduction deposition method, adjusting the pH value of the silver salt aqueous solution to alkaline with an alkali solution, and then adding the polydopamine freeze-dried powder obtained in step (1) to the silver salt aqueous solution; stirring the reaction at a temperature of 20-30° C. and a speed of 400-700 rpm for 1-3 hours, in situ reducing the silver salt on the surface of the polydopamine nanoparticles to generate silver nanoparticles, washing with a detergent by centrifugation, and freeze-drying to obtain polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles;

[0011] (3) Add gelatin to pure water and stir to dissolve in a water bath to obtain a gelatin solution;

[0012] (4) using a one-pot mixing method, adding the lyophilized powder of polydopamine nanoparticles loaded with silver nanoparticles obtained in step (2), polymer monomers, crosslinking agents, initiators and surfactants to the gelatin solution obtained in step (3), and mixing them evenly to obtain a prepolymer solution; filling the prepolymer solution into a mold, heating and inducing polymerization, and obtaining a conductive gel for underwater sensing;

[0013] The pH value of step (1) is adjusted to 9-12; the stirring reaction temperature is 20-30°C, the stirring reaction time is 12-36h, and the stirring speed is 400-700rpm; the alkali solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; and the detergent is pure water and anhydrous ethanol.

[0014] In step (1), the molar ratio of dopamine hydrochloride to ammonium persulfate is 2:1; and the volume ratio of anhydrous ethanol to pure water is 2:7.

[0015] The silver salt in step (2) is silver nitrate.

[0016] The mass ratio of the silver salt to the polydopamine freeze-dried powder in step (2) is 2:3.

[0017] The temperature of the water bath in step (3) is 40-60° C.; the concentration of gelatin in the gelatin solution is 2.5-3.0 wt %.

[0018] In step (4), the polymer monomer is one of acrylic acid and methacrylic acid; the cross-linking agent is one of N,N'-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate and polyethylene glycol dimethacrylate; the initiator is potassium persulfate or ammonium persulfate; and the surfactant is ethyltrimethylammonium bromide, hexyltrimethylammonium bromide or dodecyltrimethylammonium bromide.

[0019] In step (4), the amount of the lyophilized powder of polydopamine nanoparticles loaded with silver nanoparticles is 0.10wt% of the conductive gel; the amount of the polymer monomer is 20.00-30.00wt% of the conductive gel; the amount of the crosslinking agent is 0.01-0.05wt% of the conductive gel; the amount of the initiator is 1.10-1.20wt% of the conductive gel; and the amount of the surfactant is 3.75wt%-11.25wt% of the conductive gel.

[0020] The heat-induced polymerization in step (4) is performed by heating at 60-80°C for 30-360 minutes; the mold is a square polytetrafluoroethylene or silicone mold; and the thickness of the conductive gel obtained by filling the prepolymer liquid into the mold is controlled by controlling the amount of prepolymer liquid added.

[0021] A conductive gel for underwater sensing prepared by the above-mentioned preparation method, wherein the conductive gel for underwater sensing has stretchability, stability and durability of underwater adhesion, and can be used as a wearable flexible sensor to monitor human body movement in water.

[0022] The above-mentioned conductive gel for underwater sensing is used in the preparation of underwater adhesives and underwater sensors.

[0023] The above-mentioned underwater sensing conductive gel is used to prepare a wearable flexible sensor for monitoring human body movement in water.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The conductive gel for underwater sensing of the present invention has excellent underwater stretchability.

[0026] (2) The conductive gel for underwater sensing of the present invention has excellent underwater adhesion properties.

[0027] (3) The conductive gel for underwater sensing of the present invention has excellent underwater sensing performance.

[0028] (4) The underwater sensing conductive gel prepared by the present invention can be applied to the fields of underwater adhesion and underwater sensing; its excellent underwater adhesion performance can be used as an underwater adhesive. In addition, its excellent underwater sensing performance can be used for underwater human motion monitoring, physiological signal monitoring and distress signal transmission, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FTIR spectra of Gelatin, AA, PDA@Ag, HTAB and Gelatin / PAA / PDA@Ag / HTAB hydrogel;

[0030] Figure 2 The stress-strain curves of Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel after being immersed in water for 12 h;

[0031] Figure 3 is the adhesion strength of Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel to the steel plate;

[0032] Figure 4 The adhesion strength of Gelatin / PAA / PDA@Ag / HTAB hydrogel to different substrate materials;

[0033] Figure 5 The adhesion strength of Gelatin / PAA / PDA@Ag / HTAB hydrogel to pig skin at different adhesion cycles;

[0034] Figure 6 The adhesion strength of Gelatin / PAA / PDA@Ag / HTAB hydrogel to pig skin at different adhesion durations;

[0035] Figure 7After the Gelatin / PAA / PDA@Ag / HTAB hydrogel was immersed in water for 12 hours, it was used as a sensor to monitor the relative resistance change during underwater finger movement. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to specific embodiments, but they should not be construed as limiting the present invention.

[0037] The preparation process of the conductive gel for underwater sensing in the following embodiments is as follows:

[0038] Step 1: dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution by a solution oxidation method, the pH of the dopamine hydrochloride ethanol / water mixed solution is adjusted to 9-12 with an alkali solution, stirred at a stirring speed of 400-700 rpm at 20-30° C. for 12-36 hours, washed by centrifugation with pure water and anhydrous ethanol, and freeze-dried to obtain polydopamine freeze-dried powder (PDA);

[0039] Step 2: Use alkaline solution to adjust the pH value of the silver salt (0.22mmol / L) aqueous solution to 9-12 by reduction deposition method. Then, add the polydopamine freeze-dried powder obtained in step 1 to the above silver salt aqueous solution; stir and react at 400-700rpm for 1-3h at 20-30℃ to in-situ reduce the silver salt on the surface of polydopamine nanoparticles to generate silver nanoparticles, wash by centrifugation with pure water and anhydrous ethanol, and freeze-dry to obtain polydopamine nanoparticles (PDA@Ag) freeze-dried powder loaded with silver nanoparticles;

[0040] Step 3: Add 2.5-3.0 wt% gelatin to pure water, stir and dissolve in a 40-60°C water bath to obtain a gelatin solution;

[0041] Step 4: using a one-pot mixing method, the freeze-dried powder of polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles obtained in step 2, polymer monomers, crosslinking agents, initiators and surfactants are added to the gelatin solution obtained in step 3, and mixed evenly to obtain a prepolymer solution; the prepolymer solution is filled into a polytetrafluoroethylene or silicone mold, the thickness of the final gel patch is controlled by controlling the amount of prepolymer solution added, and heating is performed to induce polymerization to obtain a conductive gel for underwater sensing;

[0042] The conductive gel for underwater sensing prepared by the present invention can be applied to the fields of underwater adhesion and underwater sensing. Its excellent underwater adhesion performance can be used as an underwater adhesive. In addition, its excellent underwater sensing performance can be used for underwater human motion monitoring, physiological signal monitoring, and distress signal transmission.

[0043] Example 1

[0044] This embodiment provides a method for preparing Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0045] Step 1: Mix dopamine hydrochloride (225 mg), ammonium persulfate (139.5 mg), anhydrous ethanol (10 mL) and pure water (35 mL) evenly, adjust the pH to 9-12 by adding ammonia water, stir at 500 rpm at 25 ° C for 24 hours, and obtain polydopamine freeze-dried powder (PDA) after centrifugal washing with pure water and anhydrous ethanol and freeze-drying.

[0046] Step 2: Using the reduction deposition method, the pH value of the nitrate (0.22mmol / L) aqueous solution was adjusted to 9-12 with ammonia water. Then, the polydopamine freeze-dried powder (147mg) obtained in step 1 was added to the above silver salt aqueous solution; stirred at 500rpm at 25°C for 1h, and the silver salt was in situ reduced on the surface of the polydopamine nanoparticles to generate silver nanoparticles, which were washed by centrifugation with pure water and anhydrous ethanol and freeze-dried to obtain polydopamine nanoparticles (PDA@Ag) freeze-dried powder loaded with silver nanoparticles.

[0047] Step 3: Add gelatin (0.5 g) to pure water (10 mL) and stir to dissolve in a 55°C water bath to obtain a gelatin solution;

[0048] Step 4: Using a one-pot mixing method, the freeze-dried powder (0.0135 g) of polydopamine nanoparticles loaded with silver nanoparticles (PDA@Ag), acrylic acid (5.25 g), N,N'-methylenebisacrylamide (0.0056 g), and ammonium persulfate (0.2 g) obtained in step 2 were added to the gelatin solution obtained in step 3, and mixed evenly to obtain a Gelatin / PAA / PDA@Ag prepolymer solution.

[0049] Alternatively, a one-pot mixing method is used, whereby the lyophilized powder (0.0135 g) of polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles obtained in step 2, acrylic acid (5.25 g), N,N'-methylenebisacrylamide (0.0056 g), ammonium persulfate (0.2 g) and ethyltrimethylammonium bromide (1.30 g) are added to the gelatin solution obtained in step 3, and the mixture is mixed evenly to obtain a Gelatin / PAA / PDA@Ag / HTAB prepolymer solution.

[0050] The Gelatin / PAA / PDA@Ag prepolymer solution and the Gelatin / PAA / PDA@Ag / HTAB prepolymer solution obtained above were filled into polytetrafluoroethylene or silicone molds respectively, and the thickness of the final gel patch was controlled by controlling the amount of prepolymer solution added. After heating at 80°C for 30 minutes, a conductive gel for underwater sensing was obtained, which was recorded as Gelatin / PAA / PDA@Ag hydrogel or Gelatin / PAA / PDA@Ag / HTAB hydrogel.

[0051] Experimental results: Figure 1 As shown, for gelatin, 1643cm -1 and 3300cm -1 The broad peaks at 2700–3400 cm are attributed to the combined peaks of the stretching vibrations of OH and CH from the spectrum data of acrylic acid (AA). The peak appears at 1639 cm -1 and 1722cm -1 They are attributed to C=C and C=O vibrations, respectively. For PDA@Ag, 3000-3500cm -1 The combined peak of OH and NH stretching vibration appeared at 1288 cm -1 The peak at 1508 cm is the stretching vibration peak of phenolic CO. -1 , 1570cm -1 It is the stretching vibration peak of aromatic C=C. 831cm -1 The peak is the out-of-plane vibration peak of the CH of aromatic hydrocarbons. For hexyltrimethylammonium bromide (HTAB), 2864 cm -1 and 2956cm -1 The peak is attributed to 2929cm -1 The peak is attributed to -CH 2 -Stretching vibration. 3010cm -1 Appeared For Gelatin / PAA / PDA@Ag / HTAB hydrogel, the peak is 3000-3500cm -1 There are broad and narrow peaks of OH and NH around 2956cm -1 is the stretching vibration of CH, 1639 cm -1 The double bond attributed to C=C disappears, proving that the C=C double bond undergoes polymerization.

[0052] This embodiment provides a method for evaluating the underwater tensile properties of Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0053] Step 1: Fill the Gelatin / PAA / PDA@Ag prepolymer solution and the Gelatin / PAA / PDA@Ag / HTAB prepolymer solution obtained in the above Example 1 into a grooved polytetrafluoroethylene mold with a length (50 mm) × width (10 mm) × height (2 mm), and heat at 80°C for 30 minutes to obtain 2 mm thick Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel.

[0054] Step 2: Soak the hydrogel obtained in step 1 in water for 12 hours.

[0055] Step 3: Use a universal testing machine to perform a tensile test on the hydrogel after immersion in step 2.

[0056] Experimental results: Figure 2 As shown in the figure, the elongation at break of Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel under water are 143.1% and 534.6%, respectively, indicating that the Gelatin / PAA / PDA@Ag / HTAB hydrogel with HTAB added can still maintain good tensile properties after being immersed in water for 12 hours, and has excellent underwater stability of mechanical properties.

[0057] Example 3

[0058] This embodiment provides a method for evaluating the underwater lap shear adhesion performance of Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0059] Step 1: Fill the Gelatin / PAA / PDA@Ag prepolymer solution and the Gelatin / PAA / PDA@Ag / HTAB prepolymer solution obtained in the above Example 1 into a silicone mold with a length of (40 mm) × width of (20 mm) × height of (2 mm), and heat at 80°C for 30 minutes to obtain Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel.

[0060] Step 2: Soak the Gelatin / PAA / PDA@Ag hydrogel and Gelatin / PAA / PDA@Ag / HTAB hydrogel obtained in step 1 in water for 12 hours.

[0061] Step 3: Use steel plate as the adhesion substrate to evaluate the underwater adhesion performance of the two. Sandwich the soaked hydrogel between two identical substrates. Then, use a 1kg weight to pressurize the overlapping area of ​​the substrate and the hydrogel for 30s.

[0062] Step 4: Clamp the base material at both ends with the tensile fixture of the universal testing machine and test the adhesion performance using the lap shear method. The tensile rate is 15 mm / min.

[0063] Experimental results: Figure 3 As shown in the figure, the underwater adhesion strength of Gelatin / PAA / PDA@Ag / HTAB hydrogel (24.5 kPa) to the steel plate is greater than that of Gelatin / PAA / PDA@Ag hydrogel (7.8 kPa), indicating that the hydrophobic region formed by HTAB and PDA@Ag is an important factor in achieving the excellent underwater adhesion performance of Gelatin / PAA / PDA@Ag / HTAB hydrogel.

[0064] Example 4

[0065] This embodiment provides a method for evaluating the lap shear adhesion performance of Gelatin / PAA / PDA@Ag / HTAB hydrogel to different substrate materials in air and underwater, comprising the following steps:

[0066] When the operation steps are the same as those in Example 3, the adhesion substrate (steel plate) is replaced with glass, wood, PET and pig skin to achieve the test of the lap shear performance of different adhesion substrate materials. In addition, if step 2 in Example 3 is skipped, the remaining operation steps are the same as those in Example 3 to achieve the test of the lap shear performance of hydrogel on different substrate materials under air.

[0067] Experimental results: Figure 4 As shown in the figure, Gelatin / PAA / PDA@Ag / HTAB hydrogel can adhere to glass, wood, steel, PET and pig skin both above and below water. Meanwhile, underwater immersion has little effect on the adhesion properties of Gelatin / PAA / PDA@Ag / HTAB hydrogel.

[0068] Example 5

[0069] This embodiment provides a method for evaluating the stability of underwater lap shear adhesion performance of Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0070] The operation steps are consistent with those in Example 3. It should be added that after the first underwater lap shear adhesion test, the subsequent adhesion tests only need to repeat the operation steps of step 3 to step 4 in Example 3.

[0071] Experimental results: Figure 5 As shown, during 15 cycles of adhesion, Gelatin / PAA / PDA@Ag / HTAB hydrogel can maintain good adhesion stability.

[0072] Example 6

[0073] This embodiment provides a method for evaluating the durability of underwater lap shear adhesion performance of Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0074] Except for controlling the change of the underwater immersion time of the underwater lap shear sample and fixing the adhesion base material to pig skin, the other operation steps are consistent with Example 3.

[0075] Experimental results: Figure 6 As shown in the figure, Gelatin / PAA / PDA@Ag / HTAB hydrogel can maintain excellent adhesion properties under different underwater immersion times. Even after being immersed in water for 8 hours, it can still stably adhere to pig skin with an adhesion strength of 14.87 kPa.

[0076] Example 7

[0077] This embodiment provides an evaluation method for underwater human motion monitoring of Gelatin / PAA / PDA@Ag / HTAB hydrogel, which includes the following steps:

[0078] Step 1: Use conductive tape, wire and waterproof tape to fix the soaked Gelatin / PAA / PDA@Ag / HTAB hydrogel obtained in step 2 of Example 2 on the finger joint.

[0079] Step 2: Use a multimeter to record the resistance change signal of Gelatin / PAA / PDA@Ag / HTAB hydrogel during the underwater movement of the finger.

[0080] Experimental results: Figure 7 As shown in the figure, after being immersed in water for 12 hours, the hydrogel sensor can still stably monitor the electrical signals generated during the flexion and extension movements of the fingers.

[0081] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a conductive gel for underwater sensing, characterized in that The steps include: (1) By a solution oxidation method, dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into an ethanol / water mixed solution of dopamine hydrochloride, the pH value of the ethanol / water mixed solution of dopamine hydrochloride is adjusted with an alkali solution, and the mixture is stirred for reaction, and the dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles, which are washed by centrifugation with a detergent, and freeze-dried to obtain polydopamine freeze-dried powder; (2) using a reduction deposition method, adjusting the pH value of the silver salt aqueous solution to alkaline with an alkali solution, and then adding the polydopamine freeze-dried powder obtained in step (1) to the silver salt aqueous solution; stirring the reaction at a temperature of 20-30° C. and a speed of 400-700 rpm for 1-3 hours, in situ reducing the silver salt on the surface of the polydopamine nanoparticles to generate silver nanoparticles, washing with a detergent by centrifugation, and freeze-drying to obtain a polydopamine nanoparticle freeze-dried powder loaded with silver nanoparticles; (3) Add gelatin to pure water and stir to dissolve in a water bath to obtain a gelatin solution; (4) Using a one-pot mixing method, the freeze-dried powder of polydopamine nanoparticles loaded with silver nanoparticles obtained in step (2), a polymer monomer, a cross-linking agent, an initiator, and a surfactant are added to the gelatin solution obtained in step (3), and the mixture is evenly mixed to obtain a prepolymer solution; the prepolymer solution is filled into a mold, and heating is performed to induce polymerization to obtain a conductive gel for underwater sensing.

2. The method for preparing a conductive gel for underwater sensing according to claim 1, characterized in that: The pH value of step (1) is adjusted to 9-12; the stirring reaction temperature is 20-30°C, the stirring reaction time is 12-36h, and the stirring speed is 400-700rpm; the alkali solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; and the detergent is pure water and anhydrous ethanol.

3. The method for preparing a conductive gel for underwater sensing according to claim 1, characterized in that: The silver salt in step (2) is silver nitrate.

4. The method for preparing a conductive gel for underwater sensing according to claim 1, characterized in that: The temperature of the water bath in step (3) is 40-60° C.; the concentration of gelatin in the gelatin solution is 2.5-3.0 wt %.

5. The method for preparing the conductive gel for underwater sensing according to claim 1, characterized in that: In step (4), the polymer monomer is one of acrylic acid and methacrylic acid; the cross-linking agent is one of N,N'-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate and polyethylene glycol dimethacrylate; the initiator is potassium persulfate or ammonium persulfate; and the surfactant is ethyltrimethylammonium bromide, hexyltrimethylammonium bromide or dodecyltrimethylammonium bromide.

6. The method for preparing the conductive gel for underwater sensing according to claim 1, characterized in that: In step (4), the amount of the lyophilized powder of polydopamine nanoparticles loaded with silver nanoparticles is 0.10wt% of the conductive gel; the amount of the polymer monomer is 20.00-30.00wt% of the conductive gel; the amount of the crosslinking agent is 0.01-0.05wt% of the conductive gel; the amount of the initiator is 1.10-1.20wt% of the conductive gel; and the amount of the surfactant is 3.75wt%-11.25wt% of the conductive gel.

7. The method for preparing the conductive gel for underwater sensing according to claim 1, characterized in that: The heat-induced polymerization in step (4) is performed by heating at 60-80°C for 30-360 minutes; the mold is a square polytetrafluoroethylene or silicone mold; and the thickness of the conductive gel obtained by filling the prepolymer liquid into the mold is controlled by controlling the amount of prepolymer liquid added.

8. A conductive gel for underwater sensing prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The underwater sensing conductive gel has stretchability, underwater adhesion stability and durability, and can be used as a wearable flexible sensor to monitor human body movements in water.

9. Use of the conductive gel for underwater sensing according to claim 8 in the preparation of underwater adhesives and underwater sensors.

10. The underwater sensing conductive gel according to claim 8 is used to prepare a wearable flexible sensor for monitoring human motion in water.

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