Highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite and its preparation method and application

Abstract

The embodiment of the present application relates to a highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite, and its preparation method and application, which belongs to the field of polymer material technology. The preparation method of the embodiment of the present application comprises the following steps: S1, adding nanohydroxyapatite to water, then adding acrylic acid, and adding chitosan after complete dissolution to obtain a mixed solution A; S2, adding acrylamide monomer, inorganic salt and initiator to the mixed solution A to obtain a mixed solution B; S3, subjecting the mixed solution B to a polymerization reaction to obtain a hydrogel. The hydrogel provided in the embodiment of the present application has a network structure containing multiple physical interactions such as hydrogen bonds, electrostatic interactions, and interactions between polymer chains, which gives it excellent mechanical properties and fast self-healing properties.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of functional polymer materials, and in particular to a highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite, and a preparation method and application thereof. Background Art

[0002] Conductive hydrogels, as an important flexible polymer material, have attracted widespread attention in fields such as electronic skin, wearable devices, and biomedicine. However, if traditional conductive hydrogels are damaged by external stress, further expansion of the damaged area will destroy the integrity of their network structure, leading to loss of functionality and shortening their service life. This poses a significant obstacle to the development of sensors.

[0003] Studies have shown that the reversible physical cross-linking network formed by dynamic bonds (including hydrogen bonds, ionic interactions, hydrophobic interactions, etc.) can give gel materials self-healing properties and restore their original mechanical properties and other functions to a certain extent. However, conductive hydrogels with a single reversible physical cross-linking network often have problems with low repair efficiency and poor sensitivity. Nanohydroxyapatite is the main component of human teeth and bones. It has good biocompatibility and is widely used in fields such as bone defect repair. Therefore, applying it to a conductive hydrogel system with multiple physical cross-linking is expected to improve its self-healing efficiency while improving its conductive properties. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite, and its preparation method and application, which achieve rapid self-healing performance and high sensitivity, and have potential application value in the fields of health monitoring, deformation sensors and wearable devices, and can effectively solve the problems of slow repair efficiency, poor mechanical properties and low sensitivity of existing conductive hydrogel materials.

[0005] The first aspect of the present invention provides a method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0006] S1. Add nanohydroxyapatite to water and stir it magnetically to form a uniform suspension. Then add acrylic acid. After it is completely dissolved, add chitosan and continue stirring until it is evenly dispersed to obtain a mixed solution A.

[0007] S2, adding acrylamide monomer, inorganic salt and initiator to the mixed solution A, stirring until all are dissolved, to obtain a mixed solution B;

[0008] S3. Pour the mixed solution B into a mold and perform a polymerization reaction to obtain a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite.

[0009] In some embodiments that may include the above embodiments, step S2 further includes: ultrasonically treating the mixed solution B to remove bubbles therein.

[0010] In some embodiments, which may include the above embodiments, the ultrasound time is 5-10 minutes; or

[0011] The ultrasonic time was 5 min.

[0012] The ultrasonic time is preferably 5 minutes, which ensures that bubbles can be removed while also preventing the hydrogel from gelling in the container due to the thermal effect generated by the ultrasonic wave.

[0013] In some embodiments that may include the above embodiments, in step S3, the polymerization reaction temperature is 40-80° C., and the polymerization reaction time is 2-4 hours.

[0014] In some embodiments that may include the above embodiments, in step S3, the polymerization reaction temperature is 60° C., and the polymerization reaction time is 3 hours.

[0015] The polymerization reaction temperature is preferably 60° C., and the polymerization reaction time is preferably 3 h to ensure complete gelation.

[0016] In some embodiments that may include the above embodiments, in step S1, the mass ratio of nanohydroxyapatite:chitosan:water is (0.25-1):(0.2-0.8):(50-100), the magnetic stirring time is 15-30 minutes, and the stirring time is continued for 5-15 minutes; or

[0017] The magnetic stirring time was 20 min, and the stirring time was continued for 10 min.

[0018] The introduction of nano-hydroxyapatite can serve as the physical cross-linking point of the hydrogel, giving it a uniform network structure and combining it with the free-moving ions of inorganic salts to achieve its good conductive properties; the addition of acrylic acid can promote the dissolution of chitosan polymer chains and form more hydrogen bonds. The semi-interpenetrating network structure in the system gives the hydrogel excellent self-healing properties.

[0019] In some embodiments that may include the above embodiments, in steps S1 and S2, the molar percentage of acrylic acid:acrylamide is 10-25%, the mass ratio of initiator:inorganic salt:water is (0.1-0.4):(0.2-0.8):(50-100), and the stirring time is 20-40s; or

[0020] The stirring time is 30s.

[0021] The addition of inorganic salts can give hydrogels electrical conductivity and antifreeze properties.

[0022] In some embodiments that may include the above embodiments, in step S2, the inorganic salt is selected from sodium perchloride and / or lithium chloride; and the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0023] The second aspect of the embodiment of the present application also provides a highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite, which is prepared by the above method. The highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite has a strength of 174kPa, an elongation at break of 1285%, a strain response sensitivity value GF>8, and the hydrogel can withstand its own weight after being cut and re-contacted for 10s. After 10 minutes of contact, it can withstand the weight of a 55g weight without breaking.

[0024] The third aspect of the embodiments of the present application also provides the application of the highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite as described above in health monitoring, deformation sensors and wearable devices.

[0025] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0026] (1) This application introduces nano-hydroxyapatite as a physical cross-linking point in the gel system, combined with the semi-interpenetrating network formed by the chitosan polymer chain. The synergistic enhancement of the two greatly improves the self-healing and mechanical properties of the hydrogel (strength of 174 kPa and elongation at break of 1285%).

[0027] (2) The chitosan molecular chain in the present application contains a large number of amino and hydroxyl groups, which can form rich hydrogen bond interactions. The addition of acrylic acid can promote the dissolution of the chitosan polymer chain to form more hydrogen bonds, while giving the hydrogel excellent transparency. The semi-interpenetrating network structure in the system enables the hydrogel to have rapid self-healing properties (the cut hydrogel can withstand its own weight after re-contact for 10 seconds, and can withstand the weight of a 55g weight after only 10 minutes of contact);

[0028] (3) The presence of freely movable ions in the hydrogel of the present application gives the hydrogel high sensitivity (strain response sensitivity value: GF>8), which can monitor the state changes of different parts of the human body (fingers, wrists, elbows and leg bending), and can distinguish the action that generates the signal by analyzing the relative resistance change curve, showing good sensing performance;

[0029] (4) In this application, nanohydroxyapatite is used as a physical cross-linking point, and acrylic acid is added to promote the dissolution of chitosan to form a semi-interpenetrating network system. The freely moving ions make it have excellent conductivity; at the same time, the preparation method provided by this application is simple and easy to achieve industrial mass production; the prepared conductive hydrogel has rapid self-healing performance, high sensitivity and good mechanical properties, and has broad application prospects in the fields of health monitoring, deformation sensors and wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 Figure 1 is a graph showing the mechanical properties of the highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite in this application, wherein Figure a is the tensile stress-strain curve corresponding to different chitosan contents, and Figure b is the tensile stress-strain curve corresponding to different nanohydroxyapatite contents;

[0032] Figure 2 Graphs showing the self-healing performance of the highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 of the present application, wherein Figure a shows the hydrogel after being severed, able to withstand its own weight and the weight of a 55g weight upon re-contact, and Figure b is an optical micrograph of the highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite;

[0033] Figure 3 Graphs showing the conductivity of the highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 of the present application, wherein Figures A and B are graphs showing the relative resistance change of the conductive hydrogel at different bending angles of the finger, wrist, elbow, and knee, respectively;

[0034] Figure 4 This is the strain response sensitivity spectrum of the highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite under different strains in Example 3 of the present application;

[0035] Figure 5 This is the transmittance spectrum of the highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 of the present application and the hydrogel in Comparative Example 2. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] In the following examples and comparative examples, unless otherwise specified, all raw materials can be purchased commercially or prepared by conventional methods.

[0038] Example 1

[0039] A method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0040] S1. Add 25 mg of nanohydroxyapatite to 5 ml of deionized water and stir magnetically for 20 minutes to form a uniform suspension. Add 0.378 g of acrylic acid to the suspension. After it is completely dissolved, add 20 mg of chitosan and continue stirring for 5 minutes until it is evenly dispersed to obtain a mixed solution A. The addition of acrylic acid can promote the dissolution of chitosan molecular chains and form more hydrogen bonding interactions.

[0041] S2. Add 2.48 g of acrylamide monomer, 0.1 g of lithium chloride, and 10 mg of potassium persulfate initiator to mixed solution A, and stir for 20 seconds to dissolve them completely. Ultrasonicate for 5 minutes to remove bubbles in the solution to obtain mixed solution B.

[0042] S3. Pour the mixed solution B into a mold, put it into an oven at 40°C for polymerization reaction for 2 hours, and then take it out to obtain a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite.

[0043] Example 2

[0044] A method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0045] S1. Add 50 mg of nanohydroxyapatite to 5 ml of deionized water and stir magnetically for 20 minutes to form a uniform suspension. Add 0.378 g of acrylic acid to the suspension. After it is completely dissolved, add 40 mg of chitosan and continue stirring for 10 minutes until it is evenly dispersed to obtain a mixed solution A. The addition of acrylic acid can promote the dissolution of chitosan molecular chains and form more hydrogen bonding interactions.

[0046] S2. Add 2.48 g of acrylamide monomer, 0.15 g of lithium chloride, and 20 mg of potassium persulfate initiator to mixed solution A, and stir for 30 seconds to dissolve them completely. Ultrasonicate for 5 minutes to remove bubbles in the solution to obtain mixed solution B.

[0047] S3. Pour the mixed solution B into a mold, put it into an oven at 50°C for polymerization reaction for 3 hours, and then take it out to obtain a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite.

[0048] Example 3

[0049] A method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0050] S1. Add 75 mg of nanohydroxyapatite to 5 ml of deionized water and magnetically stir for 20 minutes to form a uniform suspension. Add 0.378 g of acrylic acid to the suspension. After it is completely dissolved, add 60 mg of chitosan and continue stirring for 10 minutes until it is evenly dispersed to obtain a mixed solution A. The addition of acrylic acid can promote the dissolution of chitosan molecular chains and form more hydrogen bonding interactions.

[0051] S2. Add 2.48 g of acrylamide monomer, 0.2 g of lithium chloride, and 20 mg of potassium persulfate initiator to mixed solution A, and stir for 30 seconds to dissolve them completely. Ultrasonicate for 5 minutes to remove bubbles in the solution to obtain mixed solution B.

[0052] S3. Pour the mixed solution B into a mold, put it into an oven at 60°C for polymerization reaction for 3 hours, and then take it out to obtain a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite.

[0053] Example 4

[0054] A method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0055] S1. Add 75 mg of nanohydroxyapatite to 5 ml of deionized water and magnetically stir for 20 minutes to form a uniform suspension. Add 0.378 g of acrylic acid to the suspension. After it is completely dissolved, add 60 mg of chitosan and continue stirring for 15 minutes until it is evenly dispersed to obtain a mixed solution A. The addition of acrylic acid can promote the dissolution of chitosan molecular chains and form more hydrogen bonding interactions.

[0056] S2. Add 2.48 g of acrylamide monomer, 0.2 g of sodium chloride, and 20 mg of ammonium persulfate initiator to mixed solution A, stir for 40 seconds to dissolve them completely, and ultrasonicate for 10 minutes to remove bubbles in the solution to obtain mixed solution B.

[0057] S3. Pour the mixed solution B into a mold, put it into an oven at 60°C for polymerization reaction for 4 hours, and then take it out to obtain a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite.

[0058] Example 5

[0059] A method for preparing a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite, comprising the following steps:

[0060] S1. Add 100 mg of nanohydroxyapatite to 5 ml of deionized water and stir magnetically for 20 minutes to form a uniform suspension. Add 0.378 g of acrylic acid to the suspension. After it is completely dissolved, add 80 mg of chitosan and continue stirring for 15 minutes until it is evenly dispersed to obtain a mixed solution A. The addition of acrylic acid can promote the dissolution of chitosan molecular chains and form more hydrogen bond interactions.

[0061] S2. Add 2.48 g of acrylamide monomer, 0.2 g of lithium chloride, and 30 mg of potassium persulfate initiator to mixed solution A, and stir for 40 seconds to dissolve them completely. Ultrasonicate for 10 minutes to remove bubbles in the solution to obtain mixed solution B.

[0062] S3. Pour the mixed solution B into a mold, put it into an oven at 80°C for polymerization reaction for 3 hours, and then take it out to obtain a highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite.

[0063] Comparative Example 1

[0064] The hydrogel provided in this comparative example can refer to Example 3, except that no chitosan is added.

[0065] Comparative Example 2

[0066] The hydrogel provided in this comparative example can refer to Example 3, except that no acrylic acid monomer is added.

[0067] Application Examples

[0068] The highly sensitive, fast self-healing conductive hydrogels based on nanohydroxyapatite prepared in Example 1, Example 2, Example 3, Example 5 and Comparative Example 1 were cut into rectangular splines and subjected to mechanical property tests using a universal material testing machine. Figure 1This is a graph showing the mechanical properties of the highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite in this application. Figure a shows the tensile stress-strain curve for different chitosan contents, and Figure b shows the tensile stress-strain curve for different nanohydroxyapatite contents. The results show that the tensile strength and elongation at break of the hydrogel gradually increase with increasing chitosan and nanohydroxyapatite contents. When the chitosan and nanohydroxyapatite content are added at 60 mg and 75 mg, the hydrogel exhibits the best mechanical properties, with a mechanical strength of 174 kPa and an elongation at break of 1285%.

[0069] The highly sensitive, rapidly self-healing conductive hydrogel based on nanohydroxyapatite from Example 3 was prepared into two dumbbell-shaped hydrogels, one of which was dyed. The two hydrogels were cut in the middle, and the halves of each were taken and placed together. Their self-healing properties were observed after contact for a period of time. Figure 2 This is a self-healing performance diagram of the highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite in Example 3. As can be seen from the results in Figure a, the dumbbell-shaped hydrogel can quickly self-repair after being cut and re-contacted for 10 seconds, and can withstand its own weight. After 10 minutes of contact, it can withstand the weight of a 55g weight without breaking. Figure b is an optical microscope image of the highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite. The results also show that the hydrogel can quickly self-repair the cross-section after being cut and re-contacted for 10 seconds, indicating that the internal network structure of the hydrogel can quickly dissociate and reconstruct in a short period of time, further proving its fast self-healing performance.

[0070] The highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 was combined with a digital source meter and fixed to different parts of the human body, such as fingers, wrists, elbows and knees. The relative resistance change curve caused by the deformation of different parts was recorded in real time by a computer. Figure 3 The hydrogel sensor can clearly sense the bending changes of the wrist, elbow, and knee joints and convert them into repetitive and stable relative resistance changes. The waveform and peak value of the relative resistance changes are different. Therefore, the action that generates the signal can be distinguished by analyzing the relative resistance change curve. This makes it possible to monitor different movements of the human body.

[0071] The highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 was connected to a universal material testing machine to control different deformations and set the stretching rate at 100 mm / min. The relative resistance change curve caused by different deformations was recorded in real time by a computer. Figure 4 The strain response sensitivity value of the hydrogel sensor is greater than 8, indicating that it has very excellent conductive properties and sensitivity.

[0072] The highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite in Example 3 was tested for transmittance using a UV-2450 UV-visible spectrophotometer from SHIMADZU. The gel sample was placed in a sample cell, the analysis mode was adjusted to transmittance, and the test range was 400-900nm. The test results are shown in Figure 5 The transmittance of the highly sensitive and fast self-healing conductive hydrogel based on nanohydroxyapatite is greater than 85%, which is much higher than that of the hydrogel sample without the addition of acrylic monomer (the transmittance is less than 10%).

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite, characterized in that: The following steps are involved: S1. Add nanohydroxyapatite to water and stir it magnetically to form a uniform suspension. Then add acrylic acid. After it is completely dissolved, add chitosan and continue stirring until it is evenly dispersed to obtain a mixed solution A. S2, adding acrylamide monomer, inorganic salt and initiator to the mixed solution A, stirring until all are dissolved, to obtain a mixed solution B; S3, pouring the mixed solution B into a mold and performing a polymerization reaction to obtain a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite; In step S3, the polymerization reaction temperature is 40-80° C., and the polymerization reaction time is 2-4 h; In step S1, the mass ratio of nanohydroxyapatite:chitosan:water is (0.25-1):(0.2-0.8):(50-100), the magnetic stirring time is 15-30 min, and the stirring time is continued for 5-15 min; In steps S1 and S2, the molar percentage of acrylic acid:acrylamide is 10-25%, the mass ratio of initiator:inorganic salt:water is (0.1-0.4):(0.2-0.8):(50-100), and the stirring time is 20-40 s.

2. The method for preparing a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite according to claim 1, characterized in that: Step S2 further includes: subjecting the mixed solution B to ultrasonic treatment to remove bubbles therein.

3. The method for preparing a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite according to claim 2, characterized in that: The ultrasonication time is 5-10 min.

4. The method for preparing a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite according to claim 1, characterized in that: In step S3, the polymerization reaction temperature is 60° C. and the polymerization reaction time is 3 h.

5. The method for preparing a highly sensitive and fast self-repairing conductive hydrogel based on nanohydroxyapatite according to claim 1, characterized in that: In step S2, the inorganic salt is selected from sodium perchloride and / or lithium chloride; and the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

6. A highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite, characterized in that: The highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite is prepared by the method described in any one of claims 1 to 5. The strength of the hydrogel is 174 kPa, the elongation at break is 1285%, the strain response sensitivity value GF>8, and the hydrogel can withstand its own weight after being cut and re-contacted for 10 seconds. After 10 minutes of contact, it can withstand the weight of a 55g weight without breaking.

7. Application of the highly sensitive, fast self-healing conductive hydrogel based on nanohydroxyapatite as claimed in claim 6 in health monitoring, deformation sensors and wearable devices.

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