Hydrophobic adhesion ionic gel human epidermis multi-physiological signal sensor, preparation method and application

Abstract

The invention belongs to the technical field of functional gel, and provides a hydrophobic adhesion ionic gel human epidermis multiple physiological signal sensor, a preparation method and application. The preparation method of the ionic gel provided by the invention comprises the following steps: mixing monomers 2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide and diacetone acrylamide, a cross-linking agent and a photoinitiator in an ionic liquid 1-hexyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imine salt; heating and dissolving to form a precursor solution; and carrying out polymerization reaction on the precursor solution under the initiation of ultraviolet light, and curing to obtain the ionic gel. The ionic gel is simple in preparation method, has excellent hydrophobicity, adhesiveness, conductivity, mechanical performance, sensing performance and the like, and can be used as a flexible strain sensor and a flexible epidermal electrode to be applied to the fields of human physiological signal monitoring, medical health, soft robots and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional gel technology, and specifically relates to a hydrophobic adhesive ion gel human epidermal multi-physiological signal sensor, its preparation method and application. Background Technology

[0002] Traditional rigid electronic devices have limited application scenarios. However, with the continuous advancement and development of science and technology, flexible electronic devices have gradually entered people's daily lives and are widely used in fields such as soft robots, wearable electronic devices, medical and health care, and human-computer interaction. As flexible electronic devices continue to develop in production practice, people have put forward higher requirements for their performance: higher transparency, better adhesion, stronger mechanical properties, better conductivity, higher stability, faster response speed, lower signal-to-noise ratio, and a wider range of applications.

[0003] Currently, hydrogels are the most widely used gel materials in flexible strain sensors and flexible skin electrodes. However, their insufficient mechanical properties and environmental adaptability severely limit their application scenarios. In recent years, ionogels, composed of conductive ionic liquids as dispersion media and three-dimensional polymer networks, have been considered ideal materials for constructing flexible skin sensors due to their excellent mechanical properties, conductivity, and environmental stability. However, most skin sensors based on ionogels still suffer from poor conformal adhesion, low sensitivity and signal-to-noise ratio, and limited application scenarios. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for preparing a hydrophobic adhesive ionogel multi-physiological signal sensor for human epidermis. The method mainly includes the following steps: mixing [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide, diacetone acrylamide, a crosslinking agent, and a photoinitiator in a hydrophobic ionic liquid; heating to form a precursor solution; and then curing via ultraviolet light-initiated polymerization to obtain the hydrophobic adhesive ionogel. This preparation method is simple, and the resulting gel exhibits excellent hydrophobicity, adhesion, conductivity, mechanical properties, and sensing performance.

[0005] The technical approach of this invention is as follows: a hydrophobic adhesive ion gel human epidermal multi-physiological signal sensor, which is an ion gel composed of a polymer cross-linking network formed by the copolymerization of an amphoteric monomer and a nonionic monomer and an ionic liquid with hydrophobic properties.

[0006] The technical solution of this invention is:

[0007] A method for preparing a hydrophobic adhesive ionogel multi-physiological signal sensor for human epidermis includes the following steps:

[0008] (1) Add amphoteric monomers and nonionic monomers to a hydrophobic ionic liquid, and add crosslinking agent and photoinitiator. Heat and stir to dissolve, cool, and obtain precursor solution;

[0009] The mass ratios of each raw material are as follows: the sum of the masses of amphoteric monomers and nonionic monomers: hydrophobic ionic liquid: crosslinking agent: photoinitiator is 100: 200-500: 0.5-2: 1;

[0010] The mass ratio of amphoteric monomer to nonionic monomer is any one of 1:9, 2:8, or 3:7.

[0011] (2) The precursor solution obtained in (1) is injected into the mold and hydrophobic adhesive ion gel is prepared by ultraviolet light initiation.

[0012] Preferably, in (1), the hydrophobic ionic liquid includes, but is not limited to, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. Any similar ionic liquid with hydrophobic properties can be used in the method of the present invention.

[0013] The hydrophobic ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt is well compatible with the amphoteric monomer [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide and the nonionic monomer diacetone acrylamide, thus enabling the ionic gel to possess excellent hydrophobicity, conformal adhesion, mechanical properties and sensing properties.

[0014] Preferably, in (1), the amphoteric monomer is not limited to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide; any similar amphoteric monomer can be used in the method of the present invention.

[0015] The nonionic monomer is diacetone acrylamide;

[0016] The crosslinking agent is selected from any one of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and polyethylene dimethacrylate;

[0017] The photoinitiator is selected from any one of 1-hydroxycyclohexylphenyl ketone, α-hydroxyisobutyrophenyl, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

[0018] Preferably, (1) the heating and stirring temperature is 115 °C and the time is 15 min. After cooling to room temperature, the precursor solution is obtained; (2) the ultraviolet light wavelength is 365 nm and the ultraviolet light irradiation time is 10 min.

[0019] The hydrophobic adhesive ionogel of the present invention can be applied to the following aspects:

[0020] (1) It is used to make a human mechanical and physiological signal sensor. The specific method is to install conductive wires on the above-mentioned hydrophobic adhesive ion gel to obtain a hydrophobic adhesive ion gel human mechanical and physiological signal sensor.

[0021] This human biomechanical physiological signal sensor can be used to monitor physiological signals, including: distinguishing different angles of finger bending, monitoring joints at a fixed angle of continuous bending, recording knee joint movement in real time, distinguishing the speed of knee flexion, monitoring larynx vibration during phonation, monitoring pulse waves in different parts of the human body, and monitoring weak pulse signals under motion interference.

[0022] (2) Used to prepare a flexible epidermal electrode, which is an electrode for monitoring human electrophysiological signals; wherein, the human electrophysiological signals include: electrocardiogram signals and electromyogram signals;

[0023] Monitoring of electrocardiogram (ECG) signals also includes monitoring of ECG signals during underwater activities;

[0024] When monitoring electromyographic signals, the scenarios in which it is applied include: monitoring scenarios where severe external force vibration causes interference, and monitoring scenarios where sweating causes interference.

[0025] The present invention has the following advantages and effects compared with the prior art:

[0026] (1) Hydrophobic adhesive ion gel and flexible epidermal sensor prepared with it have good adaptability to different application environments. They can not only maintain good adhesion in a wide temperature range (-20~50 ℃), but also realize the measurement of weak pulse signals under external force interference during exercise, and be used for electrophysiological signal monitoring in multiple scenarios such as violent external force vibration, sweating and underwater.

[0027] (2) The ion gel of the present invention also has the following characteristics:

[0028] Excellent light transmittance: >97% on average at different wavelengths; Excellent adhesion: the adhesion strength at overlap shear is close to that of commercial tapes.

[0029] Good mechanical properties: its tensile stress at break is about 42 kPa, its tensile strain at break is about 320%, and the prepared ion gel has excellent resilience. After being subjected to more than 3000 cycles of stretching, it can still maintain good resilience and electromechanical properties, and can be used for a long time (more than a week) and repeatedly (the same piece of gel is repeatedly pasted 20 times).

[0030] Excellent conductivity: The excellent ionic conductivity meets the requirements of ion gel as a sensor, and the electrical signal conduction mode similar to human electrical signals is conducive to signal acquisition.

[0031] (3) Flexible skin sensors are used to monitor various mechanical signals of the human body. They not only show advantages such as high sensitivity (sensitivity coefficient GF=1.60 under low strain and GF=2.55 under high strain), wide linear range (good linear range from 1% to 200% under tensile strain), fast signal response and recovery speed (signal response time is 228 ms and signal recovery time is 198 ms), but also have excellent strain sensitivity. They can be attached to different parts of the human body (neck, wrist, fingertips and feet, etc.) to sensitively capture different pulse signals, and can still accurately collect pulse waves under external force interference.

[0032] (4) Compared with commercial electrodes, flexible epidermal electrodes can be used to monitor electrophysiological signals such as ECG and electromyography in various scenarios such as vibration, sweating and underwater. The measured electrophysiological signals have lower baseline noise and higher resistance to interference. They are less irritating to the skin during use and can accurately collect electrophysiological signals for a long time (the example has an experimental record of up to eight days). They can also continuously and stably monitor ECG signals underwater for more than 2300 seconds. Attached Figure Description

[0033] Figure 1 The transmittance of the ion gel in Example 1 is shown in the illustration, which is a photograph of the gel applied to the skin surface.

[0034] Figure 2 The tensile stress-strain curves of the ion gels are shown below. (A) are the tensile stress-strain curves of the ion gels with different mass ratios of two monomers in Examples 1, 5 and 6. (B) are the tensile stress-strain curves of the ion gels with different mass ratios of ionic liquid to total monomer in Examples 1, 2, 3 and 4. (C) are the tensile stress-strain curves of the ion gels with different crosslinking agent concentrations in Examples 1, 7 and 8.

[0035] Figure 3 The figures show the cyclic tensile stress-strain curves of the ionogel under different stretching cycles in Example 1.

[0036] Figure 4 Photographs showing the adhesion of the ionogel to different materials in Example 1;

[0037] Figure 5The content related to the overlap shear in the adhesion test includes: (A) is a schematic diagram of overlap shear; (B) is the overlap shear adhesion force-displacement curve of iontophoresis gel and commercial 3M tape in Example 1 (the substrate material is paper); and (C) is the adhesion strength diagram calculated from the overlap shear test of iontophoresis gel and commercial 3M tape in Example 1 (the substrate material is paper).

[0038] Figure 6 The content is about repeated 90° peeling of ion gel on the surface of human skin. Among them, (A) is a test diagram and (B) is a graph showing the change of peeling strength under different peeling times.

[0039] Figure 7 For the adhesion test of the ionogel in Example 1 at different temperatures, the ambient temperatures from left to right are -20, 25 and 50 °C, and the weight masses are 1000, 1700 and 1000 g respectively.

[0040] Figure 8 These are photographs showing the adhesion of the ionogel to different materials underwater in Example 1.

[0041] Figure 9 The water contact angles of the ion gels are as follows: (A) represents the water contact angles of ion gels with different total monomer mass to ion liquid mass ratios, from left to right: Example 1, Example 3, and Example 4; (B) represents the water contact angles of ion gels prepared with different hydrophobic ion liquids, from left to right: Example 1, Example 9, and Example 10; and (C) represents the water contact angles of the ion gels of Example 1 stored for different times.

[0042] Figure 10 The relative resistance change of the ion gel in Example 1 is shown in Figure 1. (A) is the response time of the ion gel under tensile stress, (B) is the relative resistance change value of the ion gel under different tensile strains, (C) is the change of ΔR / R0 of the ion gel under different strains, and the segmented sensitivity coefficient.

[0043] Figure 11 The graph shows the relative resistance change of the ionogel in Example 1 during a durability test of 3000 tensile cycles at 75% strain.

[0044] Figure 12The graphs show the relative resistance changes of the ion gel flexible strain sensor attached to different parts of the human body in Example 1. Among them, (A) is the relative resistance change curve when attached to the finger joint and repeatedly bent at 30°, 60° and 90° respectively; (B) is the relative resistance change curve when attached to the finger joint and maintained at bending angles of 30°, 60° and 90° respectively; (C) is the relative resistance change curve when the ion gel flexible strain sensor monitors the movement of the knee joint; and (D) is the relative resistance change curve when the ion gel flexible strain sensor monitors the speaking process.

[0045] Figure 13 The graphs are relative resistance change curves when the ion gel is used as a flexible strain sensor in Example 1. Among them, (A) is the relative resistance change curve for monitoring carotid pulse, (B) is the relative resistance change curve for monitoring radial pulse, (C) is the relative resistance change curve for monitoring fingertip pulse, and (D) is the relative resistance change curve for monitoring dorsalis pedis pulse.

[0046] Figure 14 The graph shows the relative resistance change of the radial artery pulse during the squatting and standing exercise of the experimenter, using the ion gel as a flexible strain sensor in Example 1.

[0047] Figure 15 The content related to the ion gel as a flexible epidermal electrode in Example 3 includes: (A) a photo of the ion gel as a flexible epidermal electrode with good adhesion to the skin surface; (B) a comparison of the ion gel as a flexible epidermal electrode and a commercial electrode simultaneously monitoring human electrocardiogram signals; and (C) a comparison of the ion gel as a flexible epidermal electrode and a commercial electrode monitoring human electrocardiogram signals underwater.

[0048] Figure 16 The following is an example of monitoring human electrocardiogram (ECG) signals using ion gel as a flexible epidermal electrode in Example 3. (A) ECG signal monitoring was performed under conditions of underwater stillness and underwater activity, respectively. (B) ECG signal monitoring was performed over a long period of time. (C) ECG signal monitoring was performed after repeated application.

[0049] Figure 17 Example 3 shows the use of ion gel as a flexible epidermal electrode to monitor human electromyography (EMG) signals. (A) shows the monitoring of human EMG signals by ion gel as a flexible epidermal electrode and commercial electrodes during rest, vibration, and sweating. (B) shows the baseline noise of human EMG signals by ion gel as a flexible epidermal electrode and commercial electrodes during rest, vibration, and sweating. (C) shows the monitoring and recognition of EMG signals by ion gel as a flexible epidermal electrode for different hand gestures.

[0050] Figure 18The results in Example 3 show the skin irritation response and changes in body surface temperature after the ion gel and commercial electrode have been attached to the human skin surface for an extended period of time. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0052] Examples 1-14

[0053] A method for preparing a hydrophobic adhesive ionogel multi-physiological signal sensor for human epidermis includes the following steps:

[0054] (1) Add amphoteric monomers and nonionic monomers to the hydrophobic ionic liquid, and continue to add crosslinking agent and photoinitiator. Heat and stir to dissolve (heating temperature is 115 °C, heating time is 15 min). After complete dissolution, cool to room temperature to obtain the precursor solution.

[0055] (2) Pour the cooled precursor solution from (1) into a mold and place it under a UV light source for photoinitiation for 10 min (the wavelength of the UV light is 365 nm) to obtain a hydrophobic adhesive ion gel.

[0056] The hydrophobic adhesive ionogel was prepared according to the steps described above, with the raw materials and their amounts as shown in Table 1. Note: In Table 1, " / " indicates that the raw materials and amounts are the same as in Example 1.

[0057] Table 1. Raw materials and their amounts in each embodiment Example Hydrophobic ionic liquids and dosage Amphoteric monomers and dosage Nonionic monomers and dosage Crosslinking agent and dosage Photoinitiator and dosage 1 3 g of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide 0.2 g Diacetone acrylamide 0.8g N,N'-Methylenebisacrylamide 0.005 g 0.01 g of 1-hydroxycyclohexylphenyl ketone 2 2 g of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt / / / / 3 4 g of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt / / / / 4 5 g of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt / / / / 5 / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide 0.1 g Diacetone acrylamide 0.9g / / 6 / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide 0.3 g Diacetone acrylamide 0.7g / / 7 / / / N,N'-Methylenebisacrylamide 0.01 g / 8 / / / N,N'-Methylenebisacrylamide 0.02 g / 9 3 g of 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt / / / / 10 3 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt / / / / 11 / / / / α-Hydroxyisobutyrylbenzene 0.01 g 12 / / / / 0.01g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone 13 / / / 0.005 g of polyethylene glycol diacrylate / 14 / / / 0.005 g of ethylene glycol dimethacrylate /

[0058] The elasticity and adhesive properties of the ionogels prepared in the above embodiments were tested, and the methods for testing the elasticity and adhesive properties were as follows:

[0059] Elasticity: Tensile cycle tests were conducted, and the resilience of the ionogel was evaluated based on the degree of overlap between the upward and downward curves and the calculated area of ​​the hysteresis curve.

[0060] Adhesion performance: Using glass as the adhesion substrate, an overlap shear test was conducted to calculate the gel adhesion strength and evaluate its adhesion performance.

[0061] The test results for the two indicators mentioned above are shown in Table 2 below.

[0062] Table 2. Elastic and adhesive properties of the ionogels prepared in Examples 1-14 Example Gel fracture tensile stress / kPa Fracture tensile strain elasticity Maximum adhesion strength on glass under lap shear test / kPa Adhesion properties 1 42.7 326% Excellent elasticity 44.6 Excellent adhesion properties 2 43.7 220% General elasticity 41.2 Excellent adhesion properties 3 25.8 389% Excellent elasticity 5.5 Adhesion performance is average 4 15.5 287% Excellent elasticity 1.5 Poor adhesion 5 26.7 159% Good elasticity 11.1 Good adhesion 6 109.9 357% General elasticity 8.9 General adhesion 7 40.1 146% Good elasticity 11.9 Good adhesion 8 42.8 55% Good elasticity 11.9 Good adhesion 9 42.3 218% Good elasticity 20.7 Good adhesion 10 40.7 167% Good elasticity 13.8 Good adhesion 11 44.3 234% Good elasticity 44.6 Excellent adhesion 12 39.9 220% Good elasticity 28.2 Good adhesion 13 76.9 824% Good elasticity 10.4 Good adhesion 14 86.2 846% Good elasticity 8.8 General adhesion

[0063] An adhesion strength > 30 kPa indicates excellent gel adhesion performance; an adhesion strength between 10 and 30 kPa indicates good gel adhesion performance; and an adhesion strength < 10 kPa indicates average gel adhesion performance.

[0064] In Table 2, the ionogel in Example 1 has suitable tensile stress and strain at break, and has excellent resilience and adhesion properties, which helps to achieve a rapid response to mechanical signals and is more suitable for use as a flexible strain sensor.

[0065] In Table 2, although the ion gel in Example 3 has a lower adhesion strength, the suitable stress and strain enable it to form a better conformal contact with the skin surface, thereby achieving high-quality transmission of electrophysiological signals and having a more significant advantage in the application of flexible epidermal electrodes.

[0066] Comparative Examples 1-16

[0067] Ion gels were prepared according to the raw materials and amounts in Table 3 below, where “ / ” indicates that the raw materials and amounts are the same as in Example 1.

[0068] Table 3. Raw materials, dosages, and results for Comparative Examples 1-16 Comparative Example Hydrophobic ionic liquids and dosage Amphoteric monomers and dosage Nonionic monomers and dosage Crosslinking agent and dosage Photoinitiator and dosage Product characteristics and others Example 1 3 g of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propionic acid)ammonium hydroxide 0.2g Diacetone acrylamide 0.8g N,N'-Methylenebisacrylamide 0.005g 0.01g of 1-hydroxycyclohexylphenyl ketone Excellent elasticity and excellent adhesion. 1 / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide 1 g No addition / / Ionogels are hard, brittle, and have extremely poor mechanical properties, making them unsuitable for use as flexible epidermal sensors. 2 / No addition 1 g of nonionic monomeric diacetone acrylamide / / The ionogel exhibits a tensile stress of 42.2 kPa at break and a tensile strain of 317%, demonstrating good elasticity. Its maximum adhesion strength to glass, tested under lap shear stress, is 11.6 kPa. 3 / 0.2g of 2-acrylamide-2-methylpropanesulfonic acid / / / Ionogels are milky yellow solids with a hard texture and no extensibility, making them unsuitable for use as flexible epidermal sensors. 4 / 0.2g of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate / / / 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate is not completely soluble, and a homogeneous precursor solution cannot be obtained. 5 / / N,N-Dimethylacrylamide 0.8 g / / The ionogel exhibits a tensile stress of 69.5 kPa and a tensile strain of 326% at fracture, but exhibits poor elasticity. Its maximum adhesion strength on glass, measured by lap shear test, is 40.8 kPa, indicating good adhesion. However, its poor resilience limits its application in flexible strain sensors. 6 / / Acrylamide 0.8 g / / Ionogels are white solids that are fragile and cannot be used as flexible epidermal sensors. 7 / / 0.8 g of 2-hydroxyethyl acrylate / / Ionogels are milky white solids that are fragile and cannot be used as flexible epidermal sensors. 8 / / Methyl acrylate 0.8 g / / Unable to form ionic gel after initiation 9 / / 0.8 g of ethyl acrylate / / Unable to form ionic gel after initiation 10 / / Anionic monomer acrylic acid 0.8 g / / Ionogels are white solids that are fragile and cannot be used as flexible epidermal sensors. 11 1-Hexyl-3-methylimidazolium tetrafluoroborate 3 g / / / / Some substances remained undissolved, making it impossible to obtain a homogeneous precursor solution. 12 1-Hexyl-3-methylimidazolium hexafluorophosphate 3 g / / / / Some substances remained undissolved, making it impossible to obtain a homogeneous precursor solution. 13 3 g of 1-hexyl-3-methylimidazolium chloride / / / / Unable to form ionic gel after initiation 14 3 g of 1-hexyl-3-methylimidazolium bromide / / / / Ionic gels are too soft and lack elasticity. 15 1-Ethyl-3-methylimidazolium trifluoromethane sulfonate 3 g / / / / The ionogel exhibits a tensile stress of 42.2 kPa at break and a tensile strain of 317%, demonstrating good elasticity. Its maximum adhesion strength to glass, tested under lap shear stress, is 11.6 kPa. 16 / / / No addition / Ionogels cannot form after photoinitiation.

[0069] Test Example 1: Light Transmittance

[0070] The transmittance of the ionogel prepared in Example 1 was measured using a UV-Vis spectrophotometer. The results are as follows: Figure 1 As shown, the ion gel has an average transmittance of up to 97% in the visible light wavelength range (400~800 nm), and the illustration shows that the texture of the skin surface can be clearly observed through the ion gel.

[0071] Test Example 2 Mechanical Properties

[0072] The mechanical properties of the ion gel were determined using a universal testing machine. Figure 2 (A) shows the fracture tensile stress-strain curves for Examples 1, 5, and 6. Figure 2 As shown in (A), with the increase of the proportion of the amphoteric monomer [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide, the fracture stress and strain of the ion gel are improved. Among them, the mechanical strength of Example 1 makes the gel more suitable for use as a flexible epidermal sensor.

[0073] Figure 2(B) shows the fracture tensile stress-strain curves of Examples 1, 2, 3 and 4. The four curves represent changes in the ratio between the total monomer and the ionic liquid. Examples 1 and 3 have moduli that are more compatible with the skin and have better mechanical properties.

[0074] Figure 2 (C) shows the fracture tensile stress-strain curves of Examples 1, 7, and 8. It can be seen from the figure that as the crosslinking agent content increases, the fracture strain of the ion gel decreases significantly and cannot meet the requirements of the ion gel as a flexible strain sensor.

[0075] Figure 3 The image shows the cyclic tensile stress-strain curve of the ionogel prepared in Example 1 (tensile strain is 100%). Figure 3 It can be seen that the loading-unloading curves of the ionogel almost overlap, indicating excellent resilience. Furthermore, after 300 cycles of cyclic stretching, the tensile stress-strain curve basically overlaps with that of the first cycle, maintaining resilience and stable mechanical properties.

[0076] Test Example 3 Adhesion Properties

[0077] The ionogel obtained in Example 1 of this invention was adhered to the surfaces of different objects, such as... Figure 4 As shown in the photos, the obtained ionogel exhibits good self-adhesion on surfaces of different materials.

[0078] Through the overlap shear test ( Figure 5 The adhesive properties of the ionogel obtained in Example 1 were analyzed in (A), and it was compared with the commercial adhesive 3M. TM VHB TM Compare with tape 4910 (using paper as the base material). Figure 5 (B) is the overlap shear adhesion force-displacement curve. Figure 5 The middle (C) is composed of Figure 8 The calculated maximum adhesion strength at the overlap shear is shown in the figure. As can be seen from the figure, the adhesion strength of the ionogel prepared in Example 1 is only slightly lower than that of commercial 3M tape.

[0079] The peel strength of the ionic gel in Example 1 was tested by repeatedly attaching it to the surface of human skin using a 90° peel test. Figure 6 Image (A) shows an experimental photograph of repeated pasting of materials onto the surface of human skin. Figure 6 (B) represents the peel strength of repeated adhesion to human skin surface, from... Figure 6 As can be seen in (B), after the ion gel is repeatedly peeled at 90° three times on the surface of human skin, the peel strength of the gel remains stable thereafter, demonstrating excellent repeatability.

[0080] The adhesion ability of the ionogel prepared in Example 1 under different environments was also investigated. Figure 7 The ionogel was observed to be able to lift weights of 1000, 1700, and 1000 g respectively at -20, 25, and 50 °C using an overlapping method. This result demonstrates that the prepared ionogel maintains excellent adhesion at different temperatures. Figure 8 It is known that ionogels can maintain good adhesion to different materials underwater and have strong adaptability to the environment.

[0081] Test Example 4 Hydrophobic Properties

[0082] Figure 9 In Figure (A), the water contact angle of the ion gel surface obtained in Examples 1, 3, and 4 of this invention is shown. It can be seen that the contact angle of Example 1 (using 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, with a total mass ratio of the two monomers to the ion liquid of 1:3) is 103°, exhibiting good hydrophobicity. Furthermore, as the proportion of hydrophobic ion liquid in the ion gel increases, the water contact angle of the ion gel surface increases. The contact angle of Example 3 (with a total mass ratio of the two monomers to the ion liquid of 1:4) is 108.5°, and the contact angle of Example 4 (with a total mass ratio of the two monomers to the ion liquid of 1:5) is 112.5°.

[0083] Figure 9 In Figure (B), the water contact angle of the ion gel surface obtained in Examples 1, 9, and 10 of this invention is shown. The contact angle of Example 9 (using 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) is 102°, and the contact angle of Example 10 (using 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) is 103°. It can be seen that the ion gels prepared using different types of hydrophobic ion liquids all have good hydrophobic properties.

[0084] from Figure 9 As can be seen in (C), the gel prepared in Example 1 maintained good hydrophobic properties during the 10-day test, proving that the hydrophobic properties of the gel have long-term stability and can adapt to long-term working conditions.

[0085] Experimental Example 5: Sensing Performance of a Flexible Strain Sensor Constructed with Iongel

[0086] Figure 10Figure (A) shows the response time of the ionogel obtained in Example 1 of this invention as a flexible strain sensor for the change in relative resistance under tension ∆R / R0 (where R0 is the resistance of the ionogel in the initial state, and ∆R is the difference between the resistance under tension and R0). The instantaneous tension response time is 228 ms, and the instantaneous tension recovery time is 196 ms. As can be seen from the figure, the sensor has the ability to respond quickly to instantaneous tension and release. This fast response time enables the sensor to be used in the real-time monitoring of human mechanical signals.

[0087] Figure 10 Image (B) shows the response curves of the relative resistance change of the ionogel obtained in Example 1 of this invention as a flexible strain sensor under different tensile strains, relative to the degree of strain. It can be seen that the sensor has a stable relative resistance change value under different tensile strains.

[0088] Figure 10 In Figure (C), the values ​​of the relative resistance change of the ion gel obtained in Example 1 of this invention as a flexible strain sensor under different tensile strains, and the piecewise sensitivity coefficient GF (GF=(∆R / R0) / (∆L / L0)), where L0 is the initial length of the ion gel under no-pressure conditions, and ∆L is the change in the length of the ion gel. Figure 10 It can be seen that the GF of the ionogel is 1.60 at strains of 0%–50% and 2.55 at strains of 50%–200%, exhibiting high sensitivity and the ability to monitor extremely small strain signals. The R0 value is obtained by linear fitting of the sensitivity coefficient. 2 All values ​​are greater than 99%, indicating a good linear relationship and the ability to accurately distinguish signals of different strain magnitudes.

[0089] Figure 11 This is a durability test of the ionogel obtained in Example 1 of the present invention as a flexible strain sensor, measuring the relative resistance change after 3000 tensile cycles at 75% strain. As can be seen from the figure, the ionogel maintains a stable relative resistance change value after 3000 tensile cycles, exhibiting excellent signal stability.

[0090] Figure 12 Image (A) shows the relative resistance change of the flexible strain sensor constructed from the ionogel obtained in Example 1 of this invention, attached to the proximal interphalangeal joint of the index finger, monitoring the repeated flexion and extension angles of the joint. It can be seen that the sensor can accurately distinguish different angles of finger flexion and has a fast signal response speed and high repeatability.

[0091] Figure 12 Image (B) shows the electrical signal of the flexible strain sensor constructed from the ionogel obtained in Example 1 of this invention, attached to the proximal interphalangeal joint of the index finger, monitoring the joint's continuous bending at a fixed angle. It can be seen that the sensor exhibits high discrimination and signal stability under different bending angles due to the change in relative resistance.

[0092] The flexible strain sensor constructed from the ionogel obtained in Example 1 was used to monitor the strain signals generated by human joint movement. Figure 12 Image C is a signal graph showing the sensor attached to the knee joint monitoring knee flexion motion. It can be seen that the sensor prepared by this invention can record the signals generated by knee joint movement in real time and clearly distinguish the speed and angle of knee flexion. The graph shows that the relative resistance change changes synchronously with the bending and straightening of the joint, and the signal change remains stable in each cycle. This indicates that the ionogel has rapid response capability and ideal reversibility, and can be used as a flexible strain sensor to meet the needs of monitoring movements with large strain, such as those similar to human joint movements.

[0093] The flexible strain sensor constructed using the ionogel obtained in Example 1 was used to monitor minute strain signals in the human body. Figure 12 In the middle (D), the sensor is attached to the throat to record the signal generated by the vocalization action. It can be seen that the sensor prepared by the present invention can identify the signal generated by speaking and can distinguish the response signal. Figure 13 (A) Figure 13 (B) Figure 13 (C) and Figure 13 The images (D) show the sensors attached to the carotid artery, radial artery, fingertip, and dorsalis pedis artery, respectively, recording the strain signals generated by the pulse. As can be seen from the four images, the sensors can very accurately and stably monitor the relative resistance changes generated by the pulse. Furthermore, the shock wave, tidal wave, and diastolic wave of the pulse are clearly visible in the images, demonstrating the high sensitivity of the ionogel sensor. Meanwhile, Figure 14 This is a graph showing the relative resistance change of the radial artery pulse during squatting exercises. It can be seen that even under other motion interference, the ion gel flexible strain sensor can still monitor the tiny pulse signal, proving that ion gel as a flexible strain sensor is advantageous for use in scenarios where the mechanical signal is extremely weak and a highly stable sensing interface is required (such as brain-computer interfaces, micro-expression recognition, etc.).

[0094] Experimental Example 6: Sensing Performance of Flexible Epidermal Electrodes Constructed with Iongels

[0095] Depending on the signal being monitored, the mechanical properties required for a gel as a flexible epidermal electrode differ from those required for a gel as a flexible strain sensor. The ion gel prepared in this invention possesses tunable mechanical properties, providing multiple options for different applications. When the ion gel is used as a flexible epidermal electrode, Example 3 better meets the application requirements. Figure 15 In Figure (A), it can be clearly seen that the ion gel of Example 3 adheres well to the skin surface, which is beneficial for recording the electrophysiological signals of the human body.

[0096] Figure 15 Image (B) shows the ion gel obtained in Example 3 of this invention used as a flexible epidermal electrode and a commercial electrode to simultaneously monitor human electrocardiogram (ECG) signals. It can be seen that the ECG signal recorded by the flexible epidermal electrode constructed from the ion gel is the same as that of the commercial electrode, providing a clear PQRST waveform. Because this invention uses a hydrophobic ionic liquid as the dispersion medium for the gel, it possesses certain hydrophobic properties. Figure 8 , Figure 9 This property has been verified in practice, enabling the ionogel obtained in Example 3 to be used underwater. Figure 15 In Figure (C), the ion gel obtained in Example 3 of this invention is compared with a commercial electrode for monitoring human electrocardiogram signals underwater. The commercial electrode began to detach from the skin surface after 1384 s of continuous underwater monitoring and could not record electrocardiogram signals normally, while the ion gel obtained in Example 1 could continuously and stably monitor for more than 2300 s. Figure 16 In Example 1, the ion gel was used as a flexible epidermal electrode to monitor electrocardiogram signals under both static and active conditions underwater. The ion gel electrode can record electrophysiological signals during human activity underwater, proving that the ion gel obtained in Example 3 of this invention has the potential for application in underwater monitoring.

[0097] Figure 16 Image (B) shows the ECG signal recorded over a long period of time using the ion gel obtained in Example 3 of this invention as a flexible epidermal electrode. It can be seen that the ECG signals monitored by the ion gel electrode on the third, sixth, and eighth days did not change significantly compared with the signal on the first day, proving that the ion gel electrode can be used for long-term monitoring of human electrocardiogram signals and has broad application prospects in the fields of medical health. Figure 16 In Figure (C), the ECG signal of the ion gel obtained in Example 3 of this invention was repeatedly attached to the skin surface as a flexible epidermal electrode. After being repeatedly attached 20 times, there was almost no change compared with the signal recorded the first time, which proves that the ion gel electrode can be reused repeatedly, truly realizing continuous sensing and monitoring, and effectively reducing the application cost.

[0098] Figure 17Image (A) shows the ion gel obtained in Example 3 of this invention used as a flexible epidermal electrode and a commercial electrode to simultaneously monitor the electromyography (EMG) signal of the human forearm. It can be seen that, in the resting state, the EMG signal recorded by the flexible epidermal electrode constructed from the ion gel is similar to that of the commercial electrode. Furthermore, it is clearly evident that the EMG signal measured by the ion gel in Example 3 has a finer baseline, lower noise, higher resolution, and can record the signal peak shape more faithfully. In robustness tests of the ion gel electrode and the commercial electrode in application, compared to the commercial electrode, the ion gel electrode maintains baseline stability under vibration and sweating, demonstrating higher resistance to external influences. Figure 17 (B) is composed of Figure 17 The baseline noise of the ionogel electrode of Example 3 and the commercial electrode, calculated in (A), under resting, vibrating, and sweating conditions, shows that compared to the resting condition, the commercial electrode exhibits a significant increase in noise when subjected to interference, while the ionogel electrode prepared in Example 3 shows little change in baseline amplitude under vibration and sweating. This demonstrates that the noise of the ionogel electrode interferes with the signal less and results in better signal quality.

[0099] The above results show that the ion gel prepared by the present invention can perform high-quality signal sensing under adverse interference conditions such as human movement and skin sweating, significantly reducing the requirements for the monitoring environment and enabling high-quality collection of human physiological signals in various scenarios in daily life; it is especially suitable for use in scenarios with liquid interference (such as rain or sweat), scenarios involving strenuous exercise (such as sports or military operations), and scenarios requiring long-term, continuous monitoring (such as postoperative rehabilitation monitoring).

[0100] Figure 17 Image (C) shows the electromyographic signals generated by the forearm muscles during different hand gestures, recorded using the ionogel obtained in Example 1 of this invention as a flexible epidermal electrode. Figure 17 As can be seen from (C), the ion gel flexible epidermal electrode of the present invention can accurately distinguish the electromyographic signals generated by the forearm muscle groups under different hand gestures.

[0101] Figure 18 Compared to commercial electrodes, this study compares the changes in human skin surface temperature after prolonged application to the ionogel. Camera images show that the skin surface becomes reddish after prolonged application to the commercial electrode. Thermal imaging reveals that the skin temperature at the point where the commercial electrode was applied is significantly higher than the surrounding skin surface temperature. The ionogel, however, does not exhibit these two phenomena. This limitation of commercial electrodes hinders long-term, real-time monitoring of human electrical signals. The ionogel prepared in Example 3 avoids this drawback, further compensating for the existing deficiencies of commercial electrodes and broadening the application scenarios of flexible epidermal electrodes.

[0102] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a hydrophobic adhesive ionogel multi-physiological signal sensor for human epidermis, characterized in that, Includes the following steps: (1) Add amphoteric monomers and nonionic monomers to a hydrophobic ionic liquid, and add crosslinking agent and photoinitiator. Heat and stir to dissolve, cool, and obtain precursor solution; The mass ratios of each raw material are as follows: the sum of the masses of amphoteric monomers and nonionic monomers: hydrophobic ionic liquid: crosslinking agent: photoinitiator is 100: 200-500: 0.5-2: 1; The mass ratio of amphoteric monomer to nonionic monomer is any one of 1:9, 2:8, or 3:

7. (2) The precursor solution obtained in (1) is injected into the mold and hydrophobic adhesive ion gel is prepared by ultraviolet light initiation.

2. The preparation method according to claim 1, characterized in that, (1) The hydrophobic ionic liquid is selected from any one of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt.

3. The preparation method according to claim 1, characterized in that, In (1), the amphoteric monomer is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide; The nonionic monomer is diacetone acrylamide; The crosslinking agent is selected from any one of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and polyethylene dimethacrylate; The photoinitiator is selected from any one of 1-hydroxycyclohexylphenyl ketone, α-hydroxyisobutyrophenyl, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

4. The preparation method according to claim 1, characterized in that, (1) The heating and stirring temperature is 115 °C and the time is 15 min. After cooling to room temperature, the precursor solution is obtained. (2) The wavelength of ultraviolet light is 365 nm and the irradiation time is 10 min.

5. The application of hydrophobic adhesive ionogels in the preparation of human mechanical and physiological signal sensors, characterized in that, The hydrophobic adhesive ionogel is prepared by the method of claim 1.

6. A method for using hydrophobic adhesive ionogels to fabricate human mechanical and physiological signal sensors, characterized in that, Conductive wires are mounted on the hydrophobic adhesive ionogel prepared in claim 1 to obtain the physiological signal sensor.

7. A human biomechanical physiological signal sensor, characterized in that, The human biomechanical physiological signal sensor described herein comprises the hydrophobic adhesive ion gel prepared in claim 1, and is obtained by mounting conductive wires on the hydrophobic adhesive ion gel.

8. The application of the human biomechanical physiological signal sensor as described in claim 7 in monitoring physiological signals, characterized in that, The applications include: distinguishing different angles of finger bending, monitoring joints at a fixed angle of continuous bending, recording knee joint movement in real time, distinguishing the speed of knee flexion, monitoring larynx vibration during phonation, monitoring pulse waves in different parts of the human body, and monitoring weak pulse signals under motion interference.

9. The application of hydrophobic adhesive ionogels in the preparation of flexible epidermal electrodes, characterized in that, The flexible epidermal electrode is an electrode for monitoring human electrophysiological signals; the human electrophysiological signals include: electrocardiogram signals and electromyogram signals.

10. The application of the hydrophobic adhesive ionogel as described in claim 9 in the preparation of flexible epidermal electrodes, characterized in that, Monitoring of electrocardiogram (ECG) signals also includes monitoring of ECG signals during underwater activities; When monitoring electromyographic signals, the scenarios in which it is applied include: monitoring scenarios where severe external vibrations cause interference, and monitoring scenarios where sweating causes interference.

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