A photocurable stretchable conductive hydrogel electrode for physiological signal detection

Abstract

The present invention is a light-curable stretchable conductive hydrogel electrode for physiological signal detection. The preparation method of the electrode comprises the following steps: (1) mixing acrylamide, sodium acrylate and sodium alginate and stirring for 0.5 to 2 hours to obtain a mixed solution; (2) adding glycerol, carboxylated cellulose nanofibers and MXene to the mixed solution to obtain a MXene / polyacrylamide composite solution; (3) adding 2-hydroxy-2-methyl-1-phenyl-1-acetone to obtain a MXene / polyacrylamide composite sol; (4) adding the MXene / polyacrylamide composite sol to a silica gel mold and photocuring under ultraviolet light to obtain a MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode. The method of the present invention is simple and easy to operate, and the mechanical properties of the prepared hydrogel are significantly improved.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic materials, and in particular relates to a stretchable conductive hydrogel electrode for physiological signal detection and a preparation method thereof. Background Art

[0002] The advent of the 5G era and the development of artificial intelligence have fueled a surge in interest in flexible electronics. Flexible epidermal electrodes, modeled after human skin, can accurately detect external stimuli and physiological signals, leading to their widespread application in fields such as tactile sensors and wearable electronics. Currently, the most common electrodes are made of various metals, alloys, and oxide semiconductors, but they are unable to meet the high-strain mechanical flexibility requirements of future wearable flexible electronics, such as bending, folding, twisting, and even stretching.

[0003] Hydrogels are flexible polymers composed of a three-dimensional cross-linked hydrophilic polymer network and water. They possess excellent flexibility, a tunable elastic modulus, and unique biological properties. Based on this, conductive hydrogels combined with conductive polymers or conductive nanofillers exhibit tunable electrical conductivity, which can improve the conductivity of traditional hydrogels to a certain extent. Therefore, they are considered an ideal choice for high-performance flexible epidermal electrodes.

[0004] According to the design requirements of flexible electronic devices, the matching electrodes must also have flexible and stretchable properties and maintain their original conductivity in the stretched state. However, in actual use, many problems such as poor mechanical properties and easy damage make it difficult for traditional conductive hydrogels to meet the increasingly high performance requirements of people for flexible epidermal electrodes, resulting in greatly limited applications of electrodes prepared with them. Therefore, it is of great significance to study a stretchable conductive hydrogel electrode with good mechanical properties and conductive properties for physiological signal detection. Summary of the Invention

[0005] The present invention aims to address the shortcomings of existing technologies by providing a stretchable conductive hydrogel electrode for physiological signal detection and a method for its preparation. This method involves pouring a MXene / polyacrylamide composite sol into silica gel to control the thickness. The resulting MXene / polyacrylamide composite gel is then cross-linked via UV curing to form a photocurable stretchable conductive hydrogel electrode for physiological signal detection. This method is simple and easy to operate, and the resulting hydrogel exhibits significantly improved mechanical properties.

[0006] The technical solution of the present invention is:

[0007] A stretchable conductive hydrogel electrode for physiological signal detection, wherein the preparation method of the electrode comprises the following steps:

[0008] (1) mixing acrylamide, sodium acrylate and sodium alginate and stirring the mixture at 60 to 90° C. for 0.5 to 2 hours to obtain a mixed solution;

[0009] Wherein, 0.1-0.44g sodium alginate is added for every 1.44g acrylamide and 0.24-0.36g sodium acrylate;

[0010] (2) adding glycerol, carboxylated cellulose nanofibers, and MXene to the above mixed solution, stirring at 60-90° C. for 6-12 hours to obtain a MXene / polyacrylamide composite solution;

[0011] For every 1.5-2.5 g of composite solution, add 0.01-0.66 g of glycerol, 0.01-0.07 g of carboxylated cellulose nanofibers, and 0.01-0.05 g of MXene;

[0012] (3) The composite solution was cooled to room temperature, 2-hydroxy-2-methyl-1-phenyl-1-propanone was added, and the mixture was dissolved by shaking and ultrasonication, and then deoxygenated with nitrogen to obtain a MXene / polyacrylamide composite sol;

[0013] Add 0.01-0.07g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to every 1.8-2.7g of composite sol;

[0014] (4) The MXene / polyacrylamide composite sol is added to a silicone mold and photocured under ultraviolet light for 5 to 30 minutes to obtain a MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

[0015] The stirring rate in steps (1) and (2) is 500-1000 rpm;

[0016] The light curing parameters are light intensity 10000~30000uW / cm 2 , distance 10-20cm, wavelength 405nm;

[0017] In step (3), the solution is dissolved by oscillation for 5 to 10 minutes; the solution is dissolved by ultrasonication for 20 to 30 minutes; and the solution is degassed with nitrogen for 5 to 30 minutes.

[0018] The thickness of the MXene / polyacrylamide composite gel obtained in step (4) ranges from 2 to 10 mm.

[0019] The stretchable conductive hydrogel electrode prepared by the method is used as an electrode patch in motion detection or medical detection sensors.

[0020] The essential features of the present invention are:

[0021] The raw materials used in the preparation of a photocurable, stretchable conductive hydrogel electrode for physiological signal detection—acrylamide, sodium acrylate, sodium alginate, MXene, glycerol, carboxylated cellulose nanofibers, and 2-hydroxy-2-methyl-1-phenyl-1-propanone—are all biocompatible and harmless to the human body. The MXene in the material provides excellent conductivity and stretchability, enabling high electrical signal transmission efficiency and a wide detection range within the electrode.

[0022] The MXene / polyacrylamide composite sol was added to a silicone mold and photocured under ultraviolet light for 5 minutes to obtain a MXene / polyacrylamide composite gel. This step uses photocuring to achieve rapid preparation.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Improved electrical properties: MXene is used in the preparation process. MXene is an excellent two-dimensional conductive filler that constructs a three-dimensional conductive network for electronic conductivity, greatly improving the electrical conductivity and increasing the efficiency of electrical signal conduction between the electrode and the organism;

[0025] (2) Improved mechanical properties: Stretchable conductive hydrogel electrodes are prepared. Unlike commercial metal electrodes and solid polymer electrodes, they use polyacrylamide as a flexible skeleton and have a wide detection range. MXene has good mechanical properties and can be stably dispersed in the hydrogel. The two provide the composite hydrogel with better flexibility.

[0026] (3) Improved adhesion properties: Acrylamide and glycerol are used in the preparation process, both of which can provide a large number of hydrogen bonds, thereby enhancing the adhesion of the hydrogel to biological tissues, and ultimately improving the stability and reliability of the electrode on the organism;

[0027] (4) Provide biocompatibility: The prepared hydrogel electrode has a uniform porous structure, which gives the hydrogel electrode excellent air permeability. Combined with the photothermal therapeutic effect of MXene itself, it avoids the problem of skin itching and redness caused by the airtightness when wearable electronic devices are in contact with human skin for a long time, and can provide a more comfortable wearing experience.

[0028] (5) Provides simplicity and energy saving: Unlike other preparation methods such as freeze-thaw curing, thermal curing, and ion curing, the UV curing method is used to prepare stretchable conductive hydrogel electrodes. The method is simple, easy to operate, fast curing, precise control, and does not require the addition of additional chemical reagents. At the same time, the main raw materials involved in the preparation process are simple and easy to obtain, low cost, and resource-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a scanning electron microscope image of the stretchable hydrogel electrode prepared in Example 1 of the present invention.

[0030] Figure 2 This is the stress-strain diagram of the stretchable hydrogel prepared in Example 2 of the present invention.

[0031] Figure 3 This is the tensile strain response diagram of the stretchable hydrogel electrode prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0033] The sources or properties of the raw materials used in the specific embodiment of the present invention are as follows: acrylamide was purchased from Beijing Inokai Technology Co., Ltd. with the item number A24881; sodium acrylate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with the item number S833838; sodium alginate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with the item number S100128; glycerol was purchased from Beijing Inokai Technology Co., Ltd. with the item number G1100; carboxylated cellulose nanofibers were purchased from Beijing Inokai Technology Co., Ltd. with the item number C916412; titanium carbide (Ti3C2T x MXene was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., item number 102508; 2-hydroxy-2-methyl-1-phenyl-1-propanone was purchased from Beijing Inotech Technology Co., Ltd., item number H70001.

[0034] Example 1

[0035] (1) 1.44 g acrylamide, 0.36 g sodium acrylate, and 0.11 g sodium alginate were dissolved by stirring at 60° C. for 2 hours at a stirring rate of 600 rpm to obtain a mixed solution;

[0036] (2) 0.22 g of glycerol, 0.035 g of carboxylated cellulose nanofibers, and 0.01 g of MXene were added to the solution obtained in step 1), and the temperature was adjusted to 90° C. and stirred at 600 rpm for 12 hours to obtain a MXene / polyacrylamide composite solution;

[0037] (3) The MXene / polyacrylamide composite solution of step 2) was cooled to room temperature, and 0.035 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone was added. The solution was dissolved by shaking for 10 minutes, and then ultrasonically dissolved for 30 minutes until the added material was completely dissolved to form a completely transparent, slightly yellow liquid that did not contain any impurities or suspended matter. After complete dissolution, the solution was degassed with nitrogen for 20 minutes to remove dissolved oxygen in the solution and prevent incomplete polymerization. After the above solution was deoxygenated with nitrogen, a MXene / polyacrylamide composite sol was obtained.

[0038] (4) The prepared MXene / polyacrylamide composite sol was poured into silica gel and the thickness was controlled to be 2 mm. The sol poured into the mold was placed in a UV curing box (light intensity 20000uW / cm 2 , distance 16 cm, wavelength 405 nm), and cross-linked for 5 min to obtain MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

[0039] Example 2

[0040] (1) 1.44 g acrylamide, 0.36 g sodium acrylate, and 0.22 g sodium alginate were dissolved by stirring at 60° C. for 2 hours at a stirring rate of 600 rpm to obtain a mixed solution;

[0041] (2) 0.22 g of glycerol, 0.035 g of carboxylated cellulose nanofibers, and 0.01 g of MXene were added to the solution obtained in step 1), and the temperature was adjusted to 90° C. and stirred at 600 rpm for 12 hours to obtain a MXene / polyacrylamide composite solution;

[0042] (3) The MXene / polyacrylamide composite solution of step 2) was cooled to room temperature, and 0.035 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone was added. The solution was dissolved by shaking for 10 minutes, and then ultrasonically dissolved for 30 minutes until the added material was completely dissolved to form a completely transparent, slightly yellow liquid that did not contain any impurities or suspended matter. After complete dissolution, the solution was degassed with nitrogen for 20 minutes to remove dissolved oxygen in the solution and prevent incomplete polymerization. After the above solution was deoxygenated with nitrogen, a MXene / polyacrylamide composite sol was obtained.

[0043] (4) The prepared MXene / polyacrylamide composite sol was poured into silica gel and the thickness was controlled to be 2 mm. The sol poured into the mold was placed in a UV curing box (light intensity 20000uW / cm 2 , distance 16 cm, wavelength 405 nm), and cross-linked for 5 min to obtain MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

[0044] Example 3

[0045] (1) 1.44 g acrylamide, 0.36 g sodium acrylate, and 0.33 g sodium alginate were dissolved by stirring at 60° C. for 2 hours at a stirring rate of 600 rpm to obtain a mixed solution;

[0046] (2) 0.22 g of glycerol, 0.035 g of carboxylated cellulose nanofibers, and 0.01 g of MXene were added to the solution obtained in step 1), and the temperature was adjusted to 90° C. and stirred at 600 rpm for 12 hours to obtain a MXene / polyacrylamide composite solution;

[0047] (3) The MXene / polyacrylamide composite solution of step 2) was cooled to room temperature, and 0.035 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone was added. The solution was dissolved by shaking for 10 minutes, and then ultrasonically dissolved for 30 minutes until the added material was completely dissolved to form a completely transparent, slightly yellow liquid that did not contain any impurities or suspended matter. After complete dissolution, the solution was degassed with nitrogen for 20 minutes to remove dissolved oxygen in the solution and prevent incomplete polymerization. After the above solution was deoxygenated with nitrogen, a MXene / polyacrylamide composite sol was obtained.

[0048] (4) The prepared MXene / polyacrylamide composite sol was poured into silica gel and the thickness was controlled to be 2 mm. The sol poured into the mold was placed in a UV curing box (light intensity 20000uW / cm 2 , distance 16 cm, wavelength 405 nm), and cross-linked for 5 min to obtain MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

[0049] Example 4

[0050] (1) 1.44 g of acrylamide, 0.36 g of sodium acrylate, and 0.44 g of sodium alginate were dissolved by stirring at 60° C. for 2 hours at a stirring rate of 600 rpm to obtain a mixed solution;

[0051] (2) 0.22 g of glycerol, 0.035 g of carboxylated cellulose nanofibers, and 0.01 g of MXene were added to the solution obtained in step 1), and the temperature was adjusted to 90° C. and stirred at 600 rpm for 12 hours to obtain a MXene / polyacrylamide composite solution;

[0052] (3) The MXene / polyacrylamide composite solution of step 2) was cooled to room temperature, and 0.035 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone was added. The solution was dissolved by shaking for 10 minutes, and then ultrasonically dissolved for 30 minutes until the added material was completely dissolved to form a completely transparent, slightly yellow liquid that did not contain any impurities or suspended matter. After complete dissolution, the solution was degassed with nitrogen for 20 minutes to remove dissolved oxygen in the solution and prevent incomplete polymerization. After the above solution was deoxygenated with nitrogen, a MXene / polyacrylamide composite sol was obtained.

[0053] (4) The prepared MXene / polyacrylamide composite sol was poured into silica gel and the thickness was controlled to be 2 mm. The sol poured into the mold was placed in a UV curing box (light intensity 20000uW / cm 2 , distance 16 cm, wavelength 405 nm), and cross-linked for 5 min to obtain MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

[0054] Scanning electron microscopy test: The hydrogel samples were freeze-dried and sprayed with gold, and the surface morphology of the hydrogel was observed using a scanning electron microscope (AperoS).

[0055] Mechanical properties test: A tensile test was performed on a dumbbell-shaped stretchable conductive hydrogel electrode (35 mm long, 6 mm wide, and 1 mm thick) using an electronic universal tensile tester (AGS-X) to test its tensile properties.

[0056] Sensing performance test: A dumbbell-shaped stretchable conductive hydrogel electrode (35 mm long, 6 mm wide, and 1 mm thick) was subjected to a tensile sensing test using a flexible tensile tester at a stretching speed of 10 mm / min to measure its tensile strain response performance.

[0057] Figure 1 This is a scanning electron microscope image of the stretchable conductive hydrogel electrode prepared in Example 1. From the image, it can be seen that the hydrogel has a thick and continuous pore wall 3D network structure.

[0058] Figure 2 3 is a stress-strain diagram of the stretchable conductive hydrogel electrode prepared in Example 2. As can be seen from the figure, the maximum stretching rate of the stretchable conductive hydrogel electrode is 1150%.

[0059] Figure 3 This graph shows the tensile strain response of the stretchable conductive hydrogel electrode prepared in Example 3. As can be seen from the graph, it can achieve sensing detection under strain conditions of 0-200%. Therefore, it can be placed on the human skin as a strain sensor to accurately detect various body movements.

[0060] In summary, the hydrogel electrodes prepared in Examples 1, 2, and 3 have the advantages of stretchability and conductivity. Their maximum stretchability is 1150%, and stretch sensing performance detection is achieved under 0-200% strain conditions. In addition, since the hydrogel contains a large number of hydrogen bonds, it can adhere to human skin and therefore has the potential to be used as an electrode patch in sports detection or medical detection sensors.

[0061] Finally, it should be noted that the foregoing description is merely a preferred embodiment of the present invention, and the present invention is intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, and improvements that fall within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

[0062] Matters not covered by the present invention are known technologies.

Claims

1. A stretchable conductive hydrogel electrode for physiological signal detection, characterized by The preparation method of the electrode comprises the following steps: (1) mixing acrylamide, sodium acrylate and sodium alginate and stirring at 60 to 90° C. for 0.5 to 2 hours to obtain a mixed solution; Wherein, 0.1-0.44g sodium alginate is added for every 1.44g acrylamide and 0.24-0.36g sodium acrylate; (2) adding glycerol, carboxylated cellulose nanofibers, and MXene to the above mixed solution, stirring at 60-90° C. for 6-12 hours to obtain a MXene / polyacrylamide composite solution; For every 1.5-2.5 g of composite solution, add 0.01-0.66 g of glycerol, 0.01-0.07 g of carboxylated cellulose nanofibers, and 0.01-0.05 g of MXene; (3) The composite solution was cooled to room temperature, 2-hydroxy-2-methyl-1-phenyl-1-propanone was added, and the mixture was dissolved by shaking and ultrasonication, and then deoxygenated with nitrogen to obtain a MXene / polyacrylamide composite sol; Add 0.01-0.07g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to every 1.8-2.7g of composite sol; (4) The MXene / polyacrylamide composite sol is added to a silicone mold and photocured under ultraviolet light for 5 to 30 minutes to obtain a MXene / polyacrylamide composite gel, which is a stretchable conductive hydrogel electrode.

2. The stretchable conductive hydrogel electrode for physiological signal detection according to claim 1, characterized in that The stirring rate in steps (1) and (2) is 500-1000 rpm.

3. The stretchable conductive hydrogel electrode for physiological signal detection according to claim 1, wherein the light curing parameter is a light intensity of 10,000 to 30,000 uW / cm 2 , distance 10~20cm, wavelength 405nm.

4. The stretchable conductive hydrogel electrode for physiological signal detection according to claim 1, characterized in that In step (3), the solution is dissolved by oscillation for 5 to 10 minutes; the solution is dissolved by ultrasonication for 20 to 30 minutes; and the solution is degassed with nitrogen for 5 to 30 minutes.

5. The stretchable conductive hydrogel electrode for physiological signal detection according to claim 1, characterized in that The thickness of the MXene / polyacrylamide composite gel obtained in step (4) ranges from 2 to 10 mm.

6. The stretchable conductive hydrogel electrode for physiological signal detection according to claim 1, characterized in that Used as electrode patches in motion detection or medical detection sensors.

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