Long-term stable self-healing conductive gel as well as preparation method and application thereof
By introducing esterification reactions containing phenylborate groups and ortho-diphenol groups into the flexible sensor and metal salt coordination bonds, a long-term and stable self-healing conductive gel is prepared, which solves the instability of the sensor in harsh environments, improves the mechanical performance and self-repair capabilities of the sensor, and is suitable for long-term applications of wearable sensors.
Patent Information
- Application Number
- CN202510396159.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-04
AI Technical Summary
Existing flexible sensors are unstable in harsh environments, are susceptible to contaminants and microbial erosion, and are vulnerable to damage during repeated tensile bending, resulting in reduced performance, limiting their long-term application in wearable strain sensors.
Borate ester bonds are formed by reacting a gelling agent containing a phenylborate group and an organic substance containing an ortho-diphenol group, and forming a metal coordination bond with a metal salt to form a double coordination structure to prepare a long-term stable self-healing conductive gel.
It has achieved improvements in the mechanical properties, self-healing properties and adhesion properties of conductive gels, and has temperature responsiveness, recyclability and long-term stability. It is suitable for wearable flexible sensors and can monitor human movements and micro-expressions.
Smart Images
Figure CN120248443A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of preparation of conductive gels, and particularly to a long-term stable self-healing conductive gel, a preparation method and an application thereof. Background Art
[0002] Flexible sensors have rapidly become a hot spot in applications due to their characteristics of flexibility, low cost, versatility and high sensitivity. Flexible sensors can convert external stimuli such as pressure, temperature and humidity into electrical signals, showing broad application prospects in the fields of wearable electronics, intelligent healthcare, electronic skin, etc.
[0003] However, traditional sensor materials have obvious deficiencies in terms of moisture retention and long-term stability. For example, in a harsh environment with pollutants such as dust and sludge, the conductivity and sensing behavior of the sensor will be unstable, and at the same time, being invaded by microorganisms such as bacteria will cause corruption, limiting long-term applications. It is easy to lose water and dry in the natural environment, resulting in performance degradation; it is easily damaged during repeated stretching and bending processes, thus losing performance. These shortcomings seriously limit the practical application of gels in wearable strain sensors. Therefore, designing and developing new conductive gels with excellent environmental stability and self-healing ability is crucial for extending the service life of flexible sensors and improving the stability of sensing performance.
[0004] Ma Chongbo et al. from Northeast Normal University prepared a new type of conductive organic gel based on polyvinyl alcohol (PVA) and polypyrrole (PPy). Taking this organic gel as a wearable strain sensor, it demonstrated excellent sensitivity and responsiveness, but it still has limitations in terms of environmental adaptability and long-term usability. Summary of the Invention
[0005] Aiming at the problems existing in the prior art, the present invention provides a long-term stable self-healing conductive gel, a preparation method and an application thereof, so as to solve the problems that the current new conductive organic gels have limitations in terms of environmental adaptability and long-term usability, show stable chemical properties in different environments, can be used stably for a long time and are applied to wearable flexible sensors.
[0006] The present invention is realized through the following technical solutions:
[0007] A preparation method of a long-term stable self-healing conductive gel, comprising the following steps:
[0008] S1, carrying out an esterification reaction on a gelling agent containing a phenylboronic acid group and an organic substance containing an o-diphenol group in an organic solvent at 45-60 °C according to a molar ratio of (0.7-4.5):(0.2-0.8), and then standing and cooling to room temperature to obtain an organic gel;
[0009] S2. Heat the organogel to the sol state, then add a metal salt and mix evenly. The mass ratio of the metal salt to the gelling agent containing a phenylboronic acid group in S1 is 1:(2.5 - 6). Finally, let it stand and cool to obtain a long-term stable self-healing conductive gel.
[0010] A further improvement of the present invention lies in:
[0011] The gelling agent containing a phenylboronic acid group in S1 is terpyridine boronic acid, 3-acrylamidophenylboronic acid, or (3-dihydroxyboron benzoic acid) cystamine.
[0012] The organic compound containing an o-diphenol group in S1 is tannic acid, 3-methacrylamidodopamine, dopamine-grafted hyaluronic acid, 4-tert-butylcatechol, polyvinyl alcohol containing diol, or 2,3-dihydroxybenzoic acid.
[0013] The organic solvent in S1 is N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, N-dimethylacetamide, methanol, or tetrahydrofuran.
[0014] In S1, first pour the gelling agent containing a phenylboronic acid group into the organic solvent and stir evenly. Subsequently, add the organic compound containing an o-diphenol group, mix, and heat to 45 - 60 °C and then keep warm for 25 - 35 min. While heating and keeping warm, oscillation is also carried out. Then, let it stand and cool.
[0015] The mass ratio of the gelling agent containing a phenylboronic acid group to the organic solvent in S1 is 1:(2 - 5).
[0016] The metal salt in S2 is sodium chloride, lithium chloride, KCl, CuCl2, ZnCl2, AlCl3, CuSO4·5H2O, Al2(SO4)3, MgSO4, Na2SO4, FeSO4·7H2O, Li2SO4, LiNO3, Al(NO3)3, Cd(NO3)2, Cr(NO3)3, Cu(NO3)2, Ba(NO3)2, NaNO3, or KNO3, and the corresponding metal ions are K + , Cu 2+ , Zn 2+ , Al 3+ , Mg 2+ , Na + , Fe 2+ , Li + , Cd 2+ , Cr 3+ or Ba 2+ .
[0017] A long-term stable self-healing conductive gel obtained by the preparation method of the long-term stable self-healing conductive gel described in any one of the above.
[0018] Application of Long-Term Stable Self-Healing Conductive Gel in Wearable Flexible Sensors
[0019] Compared with the prior art, the present invention has the following beneficial technical effects:
[0020] A preparation method of a long-term stable self-healing conductive gel of the present invention utilizes the esterification reaction between the catechol groups in the organic compound containing catechol groups and the phenylboronic acid groups in the gelling agent containing phenylboronic acid groups to generate borate ester bonds, and multiple hydrogen bonds are formed between the hydroxyl groups intermolecularly. Combining with the characteristics of the gelling agent containing phenylboronic acid groups, an organic gel containing borate ester bonds is formed. Then, a metal is introduced into the organic gel, and metal coordination bonds are formed between the metal ions and the organic gel to form a double coordination structure, which helps to improve the mechanical properties and self-repair properties of the gel, and finally a long-term stable self-healing conductive gel is obtained. This gel has good mechanical properties, self-repair properties and adhesion properties, and also has temperature responsiveness, recyclability, long-term stability and conductivity. These characteristics can be used as flexible sensors to monitor human movements (large-scale movements, small-scale movements, micro-expressions, simple handwriting recognition). The reaction conditions of the present invention are mild, the synthesis process is simple, the energy consumption is small, the post-treatment is simple, and the biocompatibility is excellent. The present invention solves the problems of poor mechanical properties of the gel and poor durability and stability in applications. Using compounds containing phenylboronic acid groups and compounds containing catechol groups as raw materials and complexing with metals, a long-term stable self-healing organic gel with flexibility, self-repair, self-adhesion and biocompatibility is prepared. Due to the introduction of dynamic borate ester bonds, it has the advantages of dynamic reversibility, mild reaction conditions and multiple responses to external stimuli. Different from traditional hydrogels, the organic gel containing borate ester bonds not only maintains a certain sensitivity and stability, but also greatly improves the mechanical properties and self-repair properties of the hydrogel due to the presence of borate ester bonds, and can be applied to intelligent wearable flexible sensors for human movement detection.
[0021] The self-healing conductive gel of the present invention is an intelligent wearable flexible sensor that can be applied to human movement detection. In practical applications, it ensures the sensitivity and reliability of sensing signals, and also has certain durability, mechanical properties and fatigue resistance, and can ensure long-term normal use. Description of the Drawings
[0022] Figure 1 Adhesion test diagram of the self-healing conductive gel prepared in Example 1;
[0023] Figure 2 Performance test diagram of cutting / self-healing of the self-healing conductive gel prepared in Example 1 at room temperature;
[0024] Figure 3Test diagram of the sensing characteristics of the self-healing conductive gel prepared in Example 1 stored for 5 days;
[0025] Figure 4 Test diagram of the sensing characteristics of the self-healing conductive gel prepared in Example 1 stored for 10 days;
[0026] Figure 5 Test diagram of the sensing characteristics of the self-healing conductive gel prepared in Example 1 stored for 20 days;
[0027] Figure 6 Test diagram of the sensing characteristics of the self-healing conductive gel prepared in Example 1 stored for 30 days;
[0028] Figure 7 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 in the finger bending state.
[0029] Figure 8 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 in the knee bending state.
[0030] Figure 9 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 in the ankle bending state.
[0031] Figure 10 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 in the state of subtle muscle movement in the throat.
[0032] Figure 11 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 in the state of subtle muscle movement in the face and the corners of the mouth.
[0033] Figure 12 Test diagram of the electrical signal of the self-healing conductive gel of Example 1 after writing "z". Detailed implementation method
[0034] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0035] A preparation method of a long-term stable self-healing conductive gel of the present invention includes the following steps:
[0036] 1) Prepare a self-healing conductive gel with the gelling agent;
[0037] The specific process is as follows:
[0038] At room temperature, a certain amount of a gelling agent containing a phenylboronic acid group is poured into an organic solvent and stirred evenly. The mass ratio of the gelling agent containing a phenylboronic acid group to the organic solvent is 1:(2 - 5). Subsequently, a compound containing an o-diphenol group is added, and the mixture is heated at 45 - 60 °C for 30 min and shaken well. The molar ratio of the gelling agent containing a phenylboronic acid group to the compound containing an o-diphenol group is (0.7 - 4.5):(0.2 - 0.8) to make the mixture homogeneous. After standing and cooling to room temperature, an organic gel is formed. Subsequently, the organic gel is heated to the sol state, and a certain amount of metal salt is continuously added. The mass ratio of the metal salt to the organic solvent is 1:(5 - 30), and the mixture is made homogeneous and then allowed to stand and cool to finally obtain a self-healing conductive gel with long-term stability.
[0039] The organic solvent is: N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, methanol, tetrahydrofuran.
[0040] The gelling agent containing a phenylboronic acid group is: terpyridine boronic acid, 3-acrylamidophenylboronic acid, (3-dihydroxyboronbenzoic acid)cystamine.
[0041] The compound containing an o-diphenol group is: tannic acid, 3-methacrylamidodopamine, dopamine-grafted hyaluronic acid, 4-tert-butylcatechol, polyvinyl alcohol containing diol, 2,3-dihydroxybenzoic acid.
[0042] The metal salt is: sodium chloride, lithium chloride, KCl, CuCl2, ZnCl2, AlCl3, CuSO4·5H2O, Al2(SO4)3, MgSO4, Na2SO4, FeSO4·7H2O, Li2SO4, LiNO3, Al(NO3)3, Cd(NO3)2, Cr(NO3)3, Cu(NO3)2, Ba(NO3)2, NaNO3, KNO3.
[0043] 2) The self-healing conductive gel containing a borate ester bond is applied to a wearable flexible sensor.
[0044] The prepared conductive hydrogel is attached to the skin surface of different joints to test the electrical signals under different reaction states of the human body.
[0045] Different reactions of the human body are: the palm and fingers are bent at different angles (30°, 60°, 90°); the bending changes of the knee and ankle joints during walking or running; the changes in facial expressions (such as swallowing, smiling); simple handwritten recognition.
[0046] The following further describes the present invention in detail with reference to the accompanying drawings:
[0047] Example 1
[0048] Add 100 mL of ethanol to a round-bottom flask, and successively add 3.0 g of 4-formylphenylboronic acid and 4.8 mL of 2-acetylpyridine. After stirring the reaction at room temperature for 12 h, add 80 mL of ammonia water and heat under reflux for 24 h. Cool the reaction solution to room temperature, filter by suction, wash with isopropanol and chloroform, and dry to obtain the product terpyridine boronic acid.
[0049] At room temperature, pour terpyridine boronic acid into 150 μL of N,N-dimethylformamide and stir evenly to make its concentration 1.68 mol / L. Subsequently, add tannic acid and mix to make its concentration 0.48 mol / L. Heat at 50 °C and shake well to make it mix evenly. During this process, the reaction starts. After standing and cooling to room temperature, a gel is formed. The reaction formula between tannic acid and terpyridine boronic acid is as follows;
[0050]
[0051] Subsequently, heat the organic gel to the sol state, continue to add 0.12 mmol of lithium chloride, mix evenly, stand and cool, and finally obtain a long-term stable self-healing conductive gel;
[0052] See Figure 1 , photos of the conductive gel in Example 1 adhering to different substrates (glass, wood, finger, paper, plastic, ceramic, iron sheet, pigskin). The gel has good adhesion properties to the surfaces of these organic and inorganic materials such as glass, wood, finger, paper, plastic, ceramic, iron sheet, and pigskin.
[0053] See Figure 2 , performance test of the conductive gel in Example 1 for cutting / self-healing at room temperature. Cut the gel in the middle, and then make the cut surfaces contact each other to observe the self-healing situation of the gel. After 10 min, there were obvious changes in the crack in the middle of the gel, but the crack could still be clearly seen. After 30 min, the crack on the gel had completely disappeared, indicating its self-healing ability. At the same time, the lamp was on before the conductive gel was cut, off after cutting, and on again after self-healing, indicating its good conductivity.
[0054] See Figures 3 to 6 , durability performance test of the conductive gel in Example 1. The strain sensor based on this organic gel could still monitor signals after 5 days ( Figure 3 ), 10 days ( Figure 4 ), 20 days ( Figure 5 ), 30 days ( Figure 6 ). Even after being exposed at room temperature for 30 days, the gel could still sense basic deformation actions such as pressing and bending, indicating its good durability.
[0055] See Figures 7 to 12, the self-healing conductive gel prepared in Example 1 was examined for its sensing ability through real-time relative resistance change testing, and the sensor was directly attached to the human body for activity monitoring. When monitoring large-scale human movements such as finger bending ( Figure 7 ), knee bending ( Figure 8 ) and ankle joint bending ( Figure 9 ) during walking or running), the strain sensor showed significant and repeatable responses under multiple flexion and release cycles, indicating that the organic gel sensor has high stability. Moreover, as the bending angle increases, the relative resistance change (ΔR / R0) also increases, suggesting that the sensor can detect the movement states of the human body under different conditions. The organic gel strain sensor can not only monitor large-scale human movements but also detect subtle human activities. Therefore, the sensor was fixed on the face, corners of the mouth and throat of volunteers to monitor subtle muscle movements close to the skin ( Figure 10 , Figure 11 ), and the response curves showed certain regularity. In addition, by writing on the strain sensor ( Figure 12 ), the response curve generated a special waveform due to local pressure, enabling the identification of different text information. It can be seen that the strain sensor based on this organic gel has broad application prospects in multiple fields such as medical and health monitoring, sports monitoring, information encryption, and human-computer interaction.
[0056] Example 2
[0057] At room temperature, terpyridine boronic acid was poured into 150 μL of N,N-dimethylacetamide and stirred evenly to a concentration of 1.92 mol / L. Subsequently, 3-methylacrylamidodopamine was added and mixed to a concentration of 0.4 mol / L. The mixture was heated at 50 °C and shaken thoroughly to make it evenly mixed. After standing and cooling to room temperature, a gel was formed; then the organic gel was heated to the sol state, and 0.12 mmol of zinc chloride was added and mixed evenly. After standing and cooling, a long-term stable self-healing conductive gel was finally obtained;
[0058] Example 3
[0059] 0.5 mL of acrylic acid was measured and dissolved in 5 mL of deionized water. Ammonia water was added to adjust the pH to 4.9, and the mixture was placed in an ice-water bath to obtain an aqueous acrylic acid solution. 20 mL of deionized water was added to a round-bottom flask, and 1.15 g of 3-aminobenzeneboronic acid and 1.18 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide were added in sequence. Ammonia water was used to adjust the pH to 4.9, and the mixture was stirred in an ice-water bath for 30 min. Then, the aqueous acrylic acid solution was slowly added dropwise and reacted for 12 h. The reaction solution was restored to room temperature, extracted with ether, filtered by suction, and dried in vacuo to obtain the product 3-acrylamidobenzeneboronic acid.
[0060] At room temperature, 3-acrylamidophenylboronic acid was poured into 150 μL of N-methylpyrrolidone and stirred evenly to make its concentration 1.68 mol / L. Subsequently, dopamine-grafted hyaluronic acid was added and mixed to make its concentration 0.34 mol / L. It was heated at 50 °C and shaken thoroughly to make it mix evenly. After standing and cooling to room temperature, a gel was formed. Subsequently, the organic gel was heated to the sol state, and 0.12 mmol of sodium chloride was continuously added and mixed evenly. After standing and cooling, a long-term stable self-healing conductive gel was finally obtained.
[0061] Example 4
[0062] At room temperature, 3-acrylamidophenylboronic acid was poured into 150 μL of dimethyl sulfoxide and stirred evenly to make its concentration 1.44 mol / L. Subsequently, 4-tert-butylcatechol was added and mixed to make its concentration 0.28 mol / L. It was heated at 50 °C and shaken thoroughly to make it mix evenly. After standing and cooling to room temperature, a gel was formed. Subsequently, the organic gel was heated to the sol state, and 0.12 mmol of copper nitrate was continuously added and mixed evenly. After standing and cooling, a long-term stable self-healing conductive gel was finally obtained.
[0063] Example 5
[0064] 100 mL of phosphate standard buffer solution was added to a round-bottom flask. 1.72 g of 3-carboxyphenylboronic acid, 1.53 g of N-hydroxysuccinimide, and 1.68 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide were added in sequence. The reaction was carried out at room temperature for 20 min, then 0.9 g of cystamine hydrochloride was added. After heating and reacting for 15 min, the solution became clear, and the heating was stopped. The reaction was carried out at room temperature for 12 h. After the reaction was complete, it was centrifugally washed with water and vacuum dried to obtain the product cystamine (3-dihydroxyboronbenzoate).
[0065] At room temperature, cystamine (3-dihydroxyboronbenzoate) was poured into 150 μL of methanol and stirred evenly to make its concentration 0.85 mol / L. Subsequently, polyvinyl alcohol containing diol was added and mixed to make its concentration 0.22 mol / L. It was heated at 50 °C and shaken thoroughly to make it mix evenly. After standing and cooling to room temperature, a gel was formed. Subsequently, the organic gel was heated to the sol state, and 0.12 mmol of cadmium nitrate was continuously added and mixed evenly. After standing and cooling, a long-term stable self-healing conductive gel was finally obtained.
[0066] Example 6
[0067] At room temperature, (3-dihydroxyboronylbenzoic acid) cystamine was poured into 150 μL of tetrahydrofuran and stirred evenly to make its concentration 1.26 mol / L. Subsequently, 2,3-dihydroxybenzoic acid was added and mixed to make its concentration 0.36 mol / L. It was heated at 50 °C and shaken sufficiently to make it mix evenly. After standing and cooling to room temperature, a gel was formed; subsequently, the organic gel was heated to the sol state, 0.12 mmol of aluminum chloride was continuously added, and it was mixed evenly. After standing and cooling, a long-term stable self-healing conductive gel was finally obtained;
[0068] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.
Claims
1. A preparation method of a long-term stable self-healing conductive gel, characterized in that, It includes the following steps: S1. Carry out an esterification reaction on the gelling agent containing a phenylboronic acid group and the organic substance containing an o-diphenol group in an organic solvent at 45 - 60 °C according to a molar ratio of (0.7 - 4.5):(0.2 - 0.8). Then let it stand and cool to room temperature to obtain an organic gel. S2. Heat the organic gel to a sol state, then add a metal salt and mix evenly. The mass ratio of the metal salt to the gelling agent containing a phenylboronic acid group in S1 is 1:(2.5 - 6). Finally, let it stand and cool to obtain a long-term stable self-healing conductive gel.
2. The preparation method of the long-term stable self-healing conductive gel according to claim 1, wherein, The gelling agent containing a phenylboronic acid group described in S1 is terpyridine boronic acid, 3-acrylamidophenylboronic acid, or (3-boronodibenzoic acid)cystamine.
3. The preparation method of the long-term stable self-healing conductive gel according to claim 1, characterized in that, The organic substance containing an o-diphenol group described in S1 is tannic acid, 3-methacrylamidodopamine, dopamine-grafted hyaluronic acid, 4-tert-butylcatechol, polyvinyl alcohol containing diol, or 2,3-dihydroxybenzoic acid.
4. The preparation method of the long-term stable self-healing conductive gel according to claim 1, wherein The organic solvent described in S1 is N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, N-dimethylacetamide, methanol, or tetrahydrofuran.
5. The preparation method of the long-term stable self-healing conductive gel according to claim 1, characterized in that, In S1, first pour the gelling agent containing a phenylboronic acid group into the organic solvent and stir evenly. Subsequently, add the organic substance containing an o-diphenol group, mix, heat to 45 - 60 °C, and then keep warm. Then let it stand and cool.
6. The preparation method of the long-term stable self-healing conductive gel according to claim 5, characterized in that, In S1, after adding the organic substance containing an o-diphenol group and mixing, heat to 45 - 60 °C and keep warm for 25 - 35 min. While heating and keeping warm, oscillation is also carried out. Then let it stand and cool.
7. The preparation method of the long-term stable self-healing conductive gel according to claim 6, characterized in that, The mass ratio of the gelling agent containing a phenylboronic acid group to the organic solvent in S1 is 1:(2 - 5).
8. The preparation method of the long-term stable self-healing conductive gel according to claim 1, characterized in that, The metal salts described in S2 are sodium chloride, lithium chloride, KCl, CuCl2, ZnCl2, AlCl3, CuSO4·5H2O, Al2(SO4)3, MgSO4, Na2SO4, FeSO4·7H2O, Li2SO4, LiNO3, Al(NO3)3, Cd(NO3)2, Cr(NO3)3, Cu(NO3)2, Ba(NO3)2, NaNO3 or KNO3, and the corresponding metal ions are K + , Cu 2+ , Zn 2+ , Al 3+ , Mg 2+ , Na + , Fe 2+ , Li + , Cd 2+ , Cr 3+ or Ba 2+ .
9. A long-term stable self-healing conductive gel obtained by the preparation method of the long-term stable self-healing conductive gel according to any one of claims 1 - 8.
10. Application of the long-term stable self-healing conductive gel according to claim 9 in a wearable flexible sensor.