A multifunctional conductive organic hydrogel and its preparation method and application

Abstract

The present invention discloses a multifunctional conductive organic hydrogel and a preparation method and application thereof, and belongs to the technical field of polymer materials. The raw materials for preparing the multifunctional conductive organic hydrogel provided by the present invention include gelatin, liquid metal, 2,3,4-trihydroxybenzaldehyde and glycerol. The multifunctional conductive organic hydrogel provided by the present invention has good mechanical properties, conductive properties, moisturizing properties, low-temperature performance, antibacterial properties, biocompatibility and external action responsiveness. The present invention also provides a preparation method and application of the multifunctional conductive organic hydrogel.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a multifunctional conductive organic hydrogel and a preparation method and application thereof. Background Art

[0002] Conductive organic hydrogels have become an important candidate material for wearable and flexible electronics due to their advantages such as high flexibility, biocompatibility and excellent drug loading capacity. However, the development of new soft materials (conductive organic hydrogels) for flexible electronics is an ongoing challenge because high conductivity and strong mechanical properties are rarely achieved at the same time. For example, when solid conductive fillers are added to hydrogels, the hydrogel matrix becomes hard and reduces stretchability. Compared with traditional solid conductive fillers, the use of gallium-based room temperature liquid metals as conductive fillers can overcome the problem of hardening of the hydrogel matrix and give the resulting material ideal electrical and thermal conductivity.

[0003] With the growing demand for eco-sustainable and environmentally friendly materials, biopolymers are encouraged to replace synthetic polymers because they inherit different topological structures found in nature, thus avoiding the toxic and complicated polymer synthesis process. In addition, biopolymers are also biodegradable and biocompatible, making them very suitable for wearable devices. Gelatin is one of the commonly used materials for making hydrogels for biomedical applications. It is a degradation product of collagen and has many excellent biological activities such as biodegradability, biocompatibility, and non-immunogenicity. In addition, gelatin itself can form physically cross-linked hydrogels below the sol-gel transition temperature.

[0004] Based on the above-mentioned related technologies, some studies have attempted to combine biopolymers and liquid metals to obtain multifunctional hydrogels with flexibility, conductivity and certain strength. However, the resulting hydrogels still have disadvantages such as hardening under low temperature conditions, being easily damaged by external environments such as bacteria, and being easy to break. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a multifunctional conductive organic hydrogel having good mechanical properties, conductive properties, moisturizing properties, low temperature performance and antibacterial properties.

[0006] The present invention also provides a method for preparing the multifunctional conductive organic hydrogel.

[0007] The present invention also provides application of the multifunctional conductive organic hydrogel.

[0008] According to an embodiment of the first aspect of the present invention, a multifunctional conductive organic hydrogel is provided, wherein raw materials for preparing the multifunctional conductive organic hydrogel include gelatin, liquid metal, 2,3,4-trihydroxybenzaldehyde and glycerol.

[0009] The multifunctional conductive organic hydrogel according to the embodiment of the present invention has at least the following beneficial effects:

[0010] Among the preparation raw materials, 2,3,4-trihydroxybenzaldehyde contains a structure of phenolic hydroxyl and aldehyde groups, which can be used as a connecting medium between liquid metal and gelatin, improve the dispersion uniformity of liquid metal, effectively dissipate mechanical energy, and improve the mechanical properties of the multifunctional conductive organic hydrogel, ensuring that it still has the mechanical stability of the gel above the physiological temperature; at the same time, 2,3,4-trihydroxybenzaldehyde has both antibacterial and antioxidant properties; liquid metal is used as a filler to improve the electrical conductivity, thermal conductivity and antibacterial properties; 2,3,4-trihydroxybenzaldehyde and liquid metal work together to ensure that the multifunctional conductive organic hydrogel is not easily destroyed by bacteria and can also prevent the formation of biofilms; glycerol is used as a solvent and also has moisturizing and antifreeze effects. Compared with pure solvent water, it is not easy to condense at low temperatures, and can maintain the ion transport and mechanical properties of the multifunctional conductive organic hydrogel. In addition, hydrogen bonds are easily formed between glycerol and water molecules, so that the organic gel has special freezing and drying tolerance and maintains deformability and conductivity.

[0011] According to the above preparation raw materials, it can be known that the multifunctional conductive organic hydrogel provided by the present invention has lower biotoxicity and higher biocompatibility.

[0012] In summary, by adjusting the preparation raw materials, the multifunctional conductive organic hydrogel provided by the present invention has high toughness (elongation at break), mechanical properties (strength), high and low temperature performance, conductivity, electrical sensitivity, thermal conductivity, moisture retention and antibacterial properties, and has good biocompatibility.

[0013] According to some embodiments of the present invention, the multifunctional conductive organic hydrogel comprises:

[0014] Gelatin, wherein the gelatin contains an amino group;

[0015] liquid metal, the liquid metal being dispersed in the gelatin;

[0016] 2,3,4-trihydroxybenzaldehyde, the 2,3,4-trihydroxybenzaldehyde is complexed with the liquid metal and reacts and bonds with the amino groups on the gelatin;

[0017] Glycerin, the glycerin being dispersed in the gelatin.

[0018] According to some embodiments of the present invention, in the raw materials for preparing the multifunctional conductive organic hydrogel, the mass ratio of 2,3,4-trihydroxybenzaldehyde to liquid metal is 1:2 to 10. For example, it can be about 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or about 1:9.

[0019] According to some embodiments of the present invention, the liquid metal comprises a eutectic gallium-indium alloy, wherein the molar ratio of gallium to indium is 2.5 to 3.5:1, for example, specifically about 3:1.

[0020] According to some embodiments of the present invention, in the raw materials for preparing the multifunctional conductive organic hydrogel, the mass ratio of 2,3,4-trihydroxybenzaldehyde to gelatin is 0 to 8:15 to 25. For example, it can be 2 to 8:20. Further specifically, it can be about 1:10, 1:5, 1:4, 1:3 or about 2:5.

[0021] According to some embodiments of the present invention, the multifunctional conductive organic hydrogel has the function of inhibiting bacterial growth and / or killing bacteria. The multifunctional conductive organic hydrogel has a spectrum of antibacterial properties.

[0022] According to some embodiments of the present invention, the bacteria include at least one of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coil).

[0023] According to some embodiments of the present invention, the multifunctional conductive organic hydrogel has the ability to promote cell growth. This ability is derived from its good biocompatibility, which provides the possibility for the multifunctional conductive organic hydrogel to be used as a raw material for preparing skin sensors.

[0024] According to some embodiments of the present invention, the use temperature of the multifunctional conductive organic hydrogel is ≥ -20°C. For example, it can be -18°C to 25°C. Within this temperature range, the multifunctional conductive organic hydrogel exhibits similar mechanical properties and electrical sensitivity. Therefore, it provides an application basis for the physiological signal monitoring of the sensor including the multifunctional conductive organic hydrogel in extreme environments.

[0025] According to an embodiment of the second aspect of the present invention, a method for preparing a multifunctional conductive organic hydrogel is provided, the preparation method comprising the following steps:

[0026] S1. Providing an aqueous solution comprising the 2,3,4-trihydroxybenzaldehyde, and an aqueous dispersion comprising the gelatin;

[0027] After dispersing the liquid metal in the aqueous solution, the obtained mixture is mixed with the aqueous dispersion to obtain a pre-gel suspension;

[0028] S2. Cooling the pre-gel suspension and soaking it in a solvent replacement system at room temperature; the solvent replacement system includes the glycerol.

[0029] The mechanism of the preparation method is as follows:

[0030] During the dispersion in step S1, coordination is formed between 2,3,4-trihydroxybenzaldehyde and the liquid metal, mainly through hydroxyl groups;

[0031] During the mixing in step S1, the aldehyde group in 2,3,4-trihydroxybenzaldehyde and the amino group in gelatin undergo a Schiff base reaction; and hydrogen bonds are generated between the hydroxyl groups in 2,3,4-trihydroxybenzaldehyde.

[0032] In step S2, glycerol partially or completely replaces the water in the pre-gel suspension to complete the solvent replacement, that is, in the preparation method, the solvent in the multifunctional conductive organic hydrogel is converted from water to a mixture of water and glycerol.

[0033] However, during the solvent replacement process, the total amount of solvent that can remain in the multifunctional conductive organic hydrogel is almost unchanged. Therefore, the mass proportion of gelatin, 2,3,4-trihydroxybenzaldehyde and liquid metal in the obtained product is almost unchanged compared with the pre-gel suspension.

[0034] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0035] The preparation method provided by the invention is simple to operate, easy to implement and convenient for industrial promotion.

[0036] The present invention adjusts the internal crystal state of the obtained multifunctional conductive organic hydrogel through a reasonable order of adding materials, thereby improving its comprehensive properties such as mechanical properties and conductive properties. In traditional technologies, glycerol is often used directly as a solvent, which will destroy the degree of cross-linking inside the obtained hydrogel. A higher glycerol concentration during the preparation process will lead to a high crystal density, which will weaken the Hofmeister effect during the solvent replacement process, thereby causing the mechanical properties of the obtained hydrogel to deteriorate. The present invention first uses water as a solvent and then uses glycerol for solvent replacement, which can obtain similar performance while significantly improving the mechanical properties of the obtained multifunctional conductive organic hydrogel.

[0037] According to some embodiments of the present invention, in step S1, the mass concentration of 2,3,4-trihydroxybenzaldehyde in the raw materials for preparing the pre-gel suspension is 0-8%, for example, about 1%, 2%, 3%, 4%, 5%, 6% or about 7%.

[0038] According to some embodiments of the present invention, in step S1, the mass concentration of gelatin in the raw materials for preparing the pre-gel suspension is 15-25%, for example, about 18%, 20% or about 22%.

[0039] According to some embodiments of the present invention, in step S1, in the raw materials for preparing the pre-gel suspension, the mass ratio of 2,3,4-trihydroxybenzaldehyde to liquid metal is 1:2 to 10. For example, it can be about 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or about 1:9.

[0040] According to some embodiments of the present invention, in step S1, the volume ratio of the aqueous solution to the aqueous dispersion is 0.8-1.2:1; for example, it may be specifically about 1:1.

[0041] According to some embodiments of the present invention, in step S2, the temperature after cooling is 0-5°C. For example, it may be about 3°C ​​or about 4°C.

[0042] According to some embodiments of the present invention, step S2 further includes keeping the temperature at the cooled temperature for 0.5 to 1.5 hours, for example, about 1 hour.

[0043] According to some embodiments of the present invention, in step S2, in the solvent replacement system, the concentration of glycerol is 50-70%, for example, specifically about 60%.

[0044] According to some embodiments of the present invention, in step S2, the solvent replacement system further includes ammonium sulfate, thereby inducing the Hofmeister effect while the solvent is replaced, further optimizing the mechanical properties and conductive properties of the obtained multifunctional conductive organic hydrogel.

[0045] According to some embodiments of the present invention, in step S2, the mass concentration of ammonium sulfate in the solvent replacement system is 20-30%, for example, about 25%.

[0046] According to some embodiments of the present invention, in step S2, the solvent replacement system further includes water, wherein the amount of water used is the difference between 100% and the sum of the mass percentages of the glycerol and ammonium sulfate, for example, specifically about 20%.

[0047] According to some embodiments of the present invention, the volume ratio of the pre-gel suspension to the solvent replacement system is 1:5-7. For example, it can be about 1:6.

[0048] According to some embodiments of the present invention, in step S2, the soaking time is ≥ 1 hour, for example, it can be about 6 hours, 5 hours, 4 hours, 3 hours or about 2 hours.

[0049] According to some embodiments of the present invention, in step S2, the soaking temperature is 20-30° C. For example, it may be about 25° C. (also called room temperature).

[0050] According to an embodiment of the third aspect of the present invention, a flexible sensing product is provided, wherein raw materials for preparing the flexible sensing product include multifunctional conductive organic hydrogel.

[0051] Since the flexible sensing product adopts all the technical solutions of the multifunctional conductive organic hydrogel of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment.

[0052] According to some embodiments of the present invention, the application temperature of the flexible sensing product is -20°C to 40°C, for example, specifically -18°C to 40°C. This includes the normal body surface temperature of mammals, as well as the extreme low temperature at which they may be active. Further specifically, it may be about 0°C, 10°C, 20°C, 30°C or about 35°C.

[0053] According to some embodiments of the present invention, the application humidity of the flexible sensing product is 10-90%, for example, about 20%, 30%, 40%, 50%, 60%, 70% or about 80%.

[0054] According to an embodiment of the fourth aspect of the present invention, there is provided an application of the flexible sensing product in motion monitoring and pressure monitoring.

[0055] Since the application adopts all the technical solutions of the flexible sensing product of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0056] Furthermore, the flexible sensing product monitors motion and pressure quickly and accurately.

[0057] According to some embodiments of the present invention, the motion in the motion monitoring includes at least one of joint bending, muscle movement and pulse beating, such as finger bending, fisting, wrist bending, neck muscle movement, finger tapping and walking.

[0058] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0059] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0060] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0062] Figure 1 The figure is a schematic diagram of the process of preparing a multifunctional conductive organic hydrogel according to the preparation method of the present invention.

[0063] Figure 2 are (a) stress-strain curves and (b) tensile elastic modulus of the multifunctional conductive organic hydrogels obtained in Examples 1 to 4 of the present invention;

[0064] Figure 3 (a) stress-strain curve and (b) tensile elastic modulus of the multifunctional conductive organic hydrogel obtained in Examples 5 to 9 of the present invention;

[0065] Figure 4 are (a) stress-strain curves and (b) tensile elastic modulus of the multifunctional conductive organic hydrogels obtained in Examples 10 to 15 of the present invention;

[0066] Figure 5 The present invention (a) is the conductivity of the multifunctional conductive organic hydrogel obtained in Examples 5 to 9; (b) the conductivity-strain curve of the multifunctional conductive organic hydrogel obtained in Example 6; (c) the response and recovery time of the multifunctional conductive organic hydrogel obtained in Example 6 under 30% strain; (d) the relative resistance change of the multifunctional conductive organic hydrogel obtained in Example 6 under different stretching frequencies; (e) the relative resistance change of the multifunctional conductive organic hydrogel obtained in Example 6 under different strains and (f) the loading-unloading cycle response of the multifunctional conductive organic hydrogel obtained in Example 6;

[0067] Figure 6 The multifunctional conductive organic hydrogel obtained in Example 6 of the present invention has (a) surface changes before and after swelling; (b) swelling degree-time curve; (c) mechanical properties at different swelling rates; (d) tensile elastic modulus at different swelling rates; and (e) moisture retention;

[0068] Figure 7 The strain sensing properties of the multifunctional conductive organic hydrogel obtained in the specific embodiment of the present invention at -18°C are (a) mechanical properties at room temperature and -18°C (b) conductivity-strain curve, (c) different strain responses, (d) response time, and (e) loading-unloading cycle response;

[0069] Figure 8The performance of the flexible sensor comprising the multifunctional conductive organic hydrogel obtained in Example 6 of the present invention in monitoring human motion and pressure (a) finger bending; (b) fisting; (c) wrist bending; (d) neck muscle movement; (e) pressure sensor finger tapping and (f) walking;

[0070] Fig. 9 The multifunctional conductive organic hydrogels obtained in (a) Examples 6 and 14 of the present invention and the inhibition zones of the blank control group against Staphylococcus aureus and Escherichia coli and (b) the hemolytic toxicity test of the multifunctional conductive organic hydrogel obtained in Example 6;

[0071] Fig.10 The results of biocompatibility testing of the multifunctional conductive organic hydrogel obtained in Example 6 of the present invention on (a) HUVEC cells, (b) PC12 cells and (c) RAW 264.7 cells;

[0072] Fig.11 These are the results of cytotoxicity testing of the multifunctional conductive organic hydrogel soaking solution obtained in Example 6 of the present invention on HUVEC cells, PC12 cells and RAW 264.7 cells. DETAILED DESCRIPTION

[0073] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0074] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0075] In the present invention, "room temperature" means 25°C±5°C.

[0076] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0077] Preparation method example

[0078] refer to Figure 1 In this example, a multifunctional conductive organic hydrogel is prepared, and the specific steps are as follows:

[0079] S1. Provide an aqueous solution of 2,3,4-trihydroxybenzaldehyde (TBA, CAS: 2144-08-3) and an aqueous dispersion of gelatin (Gelatin, abbreviated as Gel, CAS: 9000-70-8; purchased from Sigma-Aldrich, which is gelatin made from pig skin); wherein the volume ratio of the aqueous solution to the aqueous dispersion is approximately 1:1.

[0080] After dispersing liquid metal (LM, specifically EGaIn, i.e., eutectic gallium-indium alloy, in which the molar ratio of Ga to In is 3:1) in the aqueous solution, the obtained mixture and the aqueous dispersion are mixed uniformly at room temperature to obtain a pre-gel suspension;

[0081] S2. Cool the pre-gel suspension to 4°C and keep it warm for 1 hour, and soak it in a solvent replacement system at room temperature for 1 hour; the solvent replacement system is a mixed aqueous solution of glycerol (gly) and ammonium sulfate, wherein the mass concentration of glycerol is 50% and the mass concentration of ammonium sulfate (AS) is 30%. The volume ratio of the pre-gel suspension to the solvent replacement system is 1:6.

[0082] Referring to the steps of the above-mentioned preparation method example, the specific implementation method studies the effects of the above parameters on the performance of the obtained multifunctional conductive organic hydrogel by changing the amount of liquid metal, 2,3,4-trihydroxybenzaldehyde and gelatin in the pre-gel suspension in step S1, and whether the solvent replacement system contains ammonium sulfate; specifically, the amount of aqueous solution, aqueous dispersion and liquid metal added during mixing in step S1 is controlled to control the above parameters. For example, in Example 1, Gel-TBA0-LM represents an aqueous solution without adding TBA. The specific parameters of Examples 1 to 21 are shown in Table 1; the parameters not shown in Table 1 are the same as those of the preparation method example.

[0083] Table 1 Partial parameters in the specific implementation

[0084]

[0085]

[0086] In Table 1, some examples are repeated for the convenience of numbering and intra-group comparison, for example, Examples 3, 5, and 15-16 are repeated.

[0087] The freezing of Examples 17, 19 and 21 only means that the test condition is -18°C, and the actual preparation process is the same as that of Examples 16, 18 and 20, respectively.

[0088] The difference between Examples 18 to 19 and Example 3 is that the soaking process in the solvent replacement system in step S2 is not included;

[0089] The steps of Examples 20 and 21 are as follows:

[0090] A1. Provide a solution comprising 2,3,4-trihydroxybenzaldehyde (TBA, CAS: 2144-08-3) and a dispersion comprising gelatin (Gelatin, referred to as Gel, CAS: 9000-70-8; purchased from Sigma-Aldrich, and is gelatin made from pig skin); wherein the volume ratio of the solution to the dispersion is about 1:1. The solvent used in the solution and the dispersion is a mixed solution of water and glycerol in a volume ratio of 1:1.

[0091] After dispersing liquid metal (LM, specifically EGaIn, i.e., eutectic gallium-indium alloy, in which the molar ratio of Ga to In is 3:1) in a TBA solution, the resulting mixture and a gelatin dispersion are uniformly mixed at room temperature to obtain a pre-gel suspension;

[0092] A2. Cool the pre-gel suspension to 4°C.

[0093] Test Example 1

[0094] In this example, the mechanical properties of the multifunctional conductive organic hydrogel obtained in the specific implementation method are tested. The specific testing method is as follows: a universal tensile testing machine is used to perform the following steps. In the tensile test, the multifunctional conductive organic hydrogel is prepared into a dumbbell-shaped sample with a middle part width of 4.0 mm, a measuring length of 20.0 mm, and a thickness of 2 mm. -1 The obtained stress-strain curve.

[0095] Comparative Examples 10 and 13 show that gelatin alone has poor mechanical strength (tensile modulus) and elongation. After the Hofmeister effect is induced by ammonium sulfate, the mechanical strength and elongation of the gel are significantly improved. On the basis of the Hofmeister effect, adding TBA to gelatin can increase the elongation of the gel, but the mechanical strength is reduced (Examples 10 to 15). On this basis, the addition of EGaIn can increase the mechanical strength and make the elongation and mechanical strength of the gel reach an ideal state; the specific results are as follows: Figure 4 As shown, (a) is the stress-strain curve, from which the elongation at break can be read; (b) is the result of the tensile modulus.

[0096] Comparative Examples 1 to 4 show that as the concentration of TBA increases, the elongation at break of the obtained multifunctional conductive organic hydrogel increases first and then decreases, reaching a maximum at a TBA concentration of about 5%. Figure 2As shown in Figure (a); in addition, as the concentration of TBA increases, the tensile modulus decreases and the ductility increases. Figure 2 As shown in Figure (b).

[0097] The concentration of TBA was fixed at 5% to explore the effect of different mass ratios of TBA to EGaIn on the mechanical properties (Examples 5-9). With the increase of EGaIn content, the tensile modulus increased significantly, such as Figure 3 As shown in Figure (b). However, it cannot be ignored that with the addition of EGaIn, the elongation of the obtained multifunctional conductive organic hydrogel decreases. This may be because the larger liquid metal droplets lead to more porous structures in the multifunctional conductive organic hydrogel, thereby reducing the stretching rate. The specific results are shown in Figure 3 As shown in Figure (b).

[0098] Comparative Examples 16, 18 and 20 show that, compared with using water alone as a solvent or a water / glycerol mixed system as a solvent, the preparation method provided by the present invention uses a solvent replacement method, which can significantly improve the mechanical properties of the obtained multifunctional conductive organic hydrogel.

[0099] From the conventional group and the frozen group of Comparative Examples 16 to 21, it can be seen that under low-temperature freezing conditions, the mechanical properties of the multifunctional conductive organic hydrogels obtained in Examples 16 and 18 decrease; while the mechanical properties of the multifunctional conductive organic hydrogel obtained in Example 20 are slightly improved. The reason is that the original mechanical properties of the multifunctional conductive organic hydrogel obtained by the binary solvent method are very poor. After freezing, the elastic modulus is enhanced, the strength is increased, and the ductility is also slightly enhanced.

[0100] The test results of the mechanical properties of the above examples are summarized in Table 2.

[0101] Table 2 Mechanical properties of multifunctional conductive organic hydrogels obtained in Examples 1 to 21

[0102]

[0103]

[0104] Test Example 2

[0105] This example tests the strain sensing performance of the multifunctional conductive organic hydrogel obtained in Examples 5 to 9. The specific test method is: connect the two ends of the multifunctional conductive organic hydrogel (L×W×H=3cm×1cm×0.5cm) to the red and black test leads of a multimeter (DELIXI, DEM22) to measure the resistance, recorded as R (Ω). The conductivity measurement formula is σ(mS / cm)=(L×W×H) / R. The results show that with the increase in the amount of liquid metal added, the resistance of the obtained multifunctional conductive organic hydrogel first rises and then tends to stabilize, reaching a peak value at about 4%. The calculation results are as follows Figure 5As shown in Figure (a).

[0106] In this example, the KEITHLEY DMM7510 multimeter and the universal tensile machine were used to evaluate the electromechanical behavior of the multifunctional conductive organic hydrogel obtained in Example 6. The sample (width 4.0mm, length 20.0mm, thickness 2mm) was sandwiched between two copper foils to form a sandwich structure (same as test example 5, the copper foil was used as an electrode and subsequently stretched in the length direction). The relative resistance change of the multifunctional conductive organic hydrogel after the strain was applied was recorded. The calculation formula for the relative resistance change rate is as follows: ΔR / R0=(R-R0) / R0×100%, where R0 and R are the resistance of the multifunctional conductive organic hydrogel before and after being stretched, respectively. The results show that when the TBA:LM mass ratio is 1:4, the resistance of the multifunctional conductive organic hydrogel increases rapidly and the sensitivity increases with stretching, which may be attributed to the local and reversible interruption of the percolation network during the stretching process. The specific test results are as follows. Figure 5 As shown in (b).

[0107] In addition to high sensitivity, the multifunctional conductive organic hydrogel obtained in Example 6 also exhibits a fast response speed: the response time is 173ms; under the freezing condition of -18°C (Example 17), the response time is only 631ms; the test method of the response time is based on the display of the KEITHLEY multimeter, starting from the change of the relative resistance change rate to the end after stabilization. The specific test results are as follows Figure 5 As shown in Figure (c).

[0108] By applying different test frequencies (0.7Hz-3Hz) and strains (different elongation) (20-100%) to the sensor (i.e. the sandwich structure mentioned above), and testing the relative resistance change rate of the multifunctional conductive organic hydrogel during the external action. The results show that the multifunctional conductive organic hydrogel obtained in Example 6 has a stable / repeatable signal, indicating that it has good response and real-time performance as a strain sensor. The specific test results are as follows Figure 5 As shown in Figures (d) and (e).

[0109] When stretched to 100%, stretch-release experiments were performed to evaluate the durability and electrical signal reliability of the multifunctional conductive organic hydrogel, and the results showed a stable waveform with almost unchanged signal amplitude under continuous operation. Figure 5 As shown in Figure (f).

[0110] According to the test results of this example, the multifunctional conductive organic hydrogel provided by the present invention has high electronic conductivity, deformation sensitivity, rapid response and can work stably for a long time.

[0111] The test results of the above conductivity are summarized in Table 3.

[0112] Table 3 Conductivity and response time of some examples of obtained multifunctional conductive organic hydrogels

[0113] serial number Abbreviation Conductivity S / m Response time ms Example 5 Gel-TBA-LM2 0.047687 / Example 6 Gel-TBA-LM4 673.7589 173ms Example 7 Gel-TBA-LM6 681.8182 / Example 8 Gel-TBA-LM8 346.8208 / Example 9 Gel-TBA-LM10 308.9431 / Example 17 Solvent exchange-freezing / 631ms

[0114] Test Example 3

[0115] This example tests the moisture retention, swelling and antifreeze properties of the multifunctional conductive organic hydrogel obtained in the specific implementation method.

[0116] 1. Swelling measurement

[0117] The prepared multifunctional conductive organic hydrogel was weighed to its initial mass, recorded as w0. Then the multifunctional conductive organic hydrogel was placed in water, taken out every 10 minutes, and the surface water was absorbed with filter paper and its mass was weighed, recorded as w1. The swelling degree was calculated according to the following formula:

[0118]

[0119] And test the stress-strain curves under different swelling degrees (the method is the same as that of Test Example 1);

[0120] The results show that the multifunctional conductive organic hydrogel obtained in Example 6 will swell when immersed in deionized water; the specific swelling degree will first increase and then stabilize with the increase of immersion time, and reach an inflection point around 20 hours, which shows that during this time, the cross-linked network of the multifunctional conductive organic hydrogel obtained in Example 6 maintains the shape before drying; the specific test results are as follows Figure 6 As shown in Figures (a) and (b) in the figure, the mechanical properties of the swollen multifunctional conductive organic hydrogel change with the increase of swelling degree. The specific test results are shown in Figure 6 As shown in Figures (c) and (d).

[0121] 2. Moisture retention measurement

[0122] After the multifunctional conductive organic hydrogels obtained in Examples 16, 18 and 20 were prepared, their initial masses were weighed, recorded as w0, and then placed in an incubator at 37°C and 60% humidity, and their masses were weighed again at 0h, 6h, 12h, 24h and 48h, recorded as w1. The moisture retention rate of the hydrogel was calculated according to the following formula:

[0123]

[0124] The results show that the multifunctional conductive organic hydrogels obtained in Examples 16 and 20 have excellent water retention capacity and can still maintain a 90% moisture retention rate after 48 hours; while the moisture retention performance of the multifunctional conductive organic hydrogel obtained in Example 18 has significantly decreased. The specific test results are as follows Figure 6 As shown in Figure (e).

[0125] Test Example 4

[0126] This example tests the antifreeze properties of the multifunctional conductive organic hydrogel obtained by the specific implementation method. The specific method is to freeze the sample in a -18°C environment overnight. When the multifunctional conductive organic hydrogel is removed from the -18°C environment, its mechanical properties and electromechanical properties are immediately studied.

[0127] The results show that the multifunctional conductive organic hydrogel obtained in Example 16 (corresponding to Figure 7 The "solvent replacement" group or "H2O / Gly" group) in the -18°C environment also has similar mechanical properties to those in the room temperature environment, and compared with the multifunctional conductive organic hydrogel obtained by the binary solvent method (Example 20) in which glycerol is directly added to the solvent, the solvent replacement method at room temperature or after freezing treatment shows better mechanical properties; the specific test results are as follows Figure 7 As shown in Figure (a).

[0128] The multifunctional conductive organic hydrogel prepared by the preparation method provided by the present invention showed excellent sensitivity and response sensitivity close to room temperature when different strains were applied. In addition, in extreme environments, the sensor produced a stable output signal during 100% deformation cycle operation. During repeated sensing, only small response changes were observed, showing good stability, repeatability and durability. The specific test results are as follows: Figure 7 As shown in the middle figures (b) to (e).

[0129] Test Example 5

[0130] The multifunctional conductive organic hydrogel prepared in Example 6 was used as the main sensing component for preparing the sensor. The specific method is as follows: the multifunctional conductive organic hydrogel was cut into regular strips of 20×4×1mm, and the conductive copper tape was adhered to both ends of the sensor. We used tape to fix the sensor to different parts of the body. The conductive copper tape was connected to a Keithley DMM7510 source meter, and its resistance change was recorded in real time together with the body movement. The results show:

[0131] The sensor is installed on the knuckle, and the finger is bent from 0° to 90°. When the finger undergoes multiple uninterrupted bending and recovery, different finger bending degrees and resistance change signals can be distinguished. The specific test results are as follows: Figure 8 Therefore, by detecting the resistance change rate, the strain sensor including the multifunctional conductive organic hydrogel prepared by the present invention can accurately track the different bending degrees of the finger in real time.

[0132] Similarly, the strain sensor provided in this example can detect various other human activities with high sensitivity and high repeatability, such as bending the hand, wrist ( Figure 8 Middle (b)) and knee ( Figure 8 In addition, by attaching the sensor to the throat, head movements can be effectively monitored ( Figure 8 (d)). These results show that the strain sensor provided by the present invention has broad application prospects in the detection of damaged joint recovery and motion detection. In addition, the strain sensor can also respond to pressure, such as tapping with a finger ( Figure 8 Middle (e)), with a reproducible and stable signal.

[0133] Test Example 6

[0134] This example tests the antibacterial activity and hemolytic toxicity of the multifunctional conductive organic hydrogel obtained in the specific implementation method.

[0135] 1. Antimicrobial activity measurement

[0136] The antibacterial activity of the multifunctional conductive organic hydrogel obtained in Example 6 was measured using the inhibition zone method. The specific method is as follows:

[0137] The multifunctional conductive organic hydrogel Gel-TBA-EGaIn was made into a disk (1 cm in diameter) and sterilized by ultraviolet light for 60 min. 20 mL of agar was poured into a 9 cm bacterial culture dish, and then 100 μL of broth containing Staphylococcus aureus and Escherichia coli (1×10 5 CFU / mL) were dispersed on different solidified agar media. Then the multifunctional conductive organic hydrogel disc was carefully placed on the agar surface. After incubation at 37°C for 24 hours, the inhibition zone around each group of samples was observed. The results showed that the multifunctional conductive organic hydrogel obtained by the present invention has excellent antibacterial effect, and the antibacterial effect is more prominent after TBA and liquid metal synergize. The specific measurement results are as follows Fig. 9 As shown in Figure (a), the CN group is a filter paper sheet soaked with an equal amount of PBS, Gel-TBA-EGaIn corresponds to Example 6, Gel-TBA corresponds to Example 14, E. coli is a Gram-negative bacterium, Escherichia coli, and S. aureus is a Gram-positive bacterium, Staphylococcus aureus.

[0138] 2. Hemolytic toxicity measurement

[0139] The whole blood collected from the vein was centrifuged (2500×g, 3min, 4°C), washed 3 times with PBS and resuspended to make the red blood cell suspension concentration 4%. The 4% red blood cell suspension and the multifunctional conductive organic hydrogel obtained in Example 6 were incubated in a 37°C constant temperature incubator for 1h, centrifuged after the incubation (2500×g, 3min, 4°C), the supernatant was collected, and the absorbance of the supernatant at 490nm was measured and recorded as experimental group 1. Pure water (ddH2O) was used as another experimental group, and the absorbance was measured and recorded as experimental group 2. The physiological saline treatment group was used as the negative control group, and the absorbance was measured and recorded as the negative control group. The Triton X-100 (1%) treatment group was used as the positive control group, and the absorbance was measured and recorded as 100%; the hemolysis rate was calculated as follows:

[0140]

[0141] The results show that the hemolytic toxicity of the multifunctional conductive organic hydrogel (Example 6) obtained by the present invention is below 5%, which meets the standards of medical biomaterials. Fig. 9 As shown in Figure (b), in this figure, Gel-TBA-LM and Gel-TBA both correspond to Example 6.

[0142] Test Example 7

[0143] This example tests the biocompatibility of the multifunctional conductive organic hydrogel obtained in Specific Implementation Example 6. The test method and results are as follows.

[0144] 1. Cell viability detection

[0145] The MTT method was used to detect the cytotoxicity of the multifunctional conductive organic hydrogel Gel-TBA-EGaIn. The specific method is as follows:

[0146] Human umbilical vein endothelial cells (HUVECs), rat adrenal medullary pheochromocytoma cells (PC 12), and mouse leukemia cells of monocyte macrophage (RAW 264.7) were cultured to the logarithmic growth phase and then seeded into 96-well microplates at a density of approximately 1×10 5 cells / cm 2. After being placed in a CO2 incubator (37°C, 5% CO2) for 24 hours, an equal volume of multifunctional conductive organic hydrogel soaking solution diluted with basal culture medium (final concentrations of 1.5625μg / mL, 3.125μg / mL, 6.25μg / mL, 12.5μg / mL, 25μg / mL, 50μg / mL and 100μg / mL) was added to the wells, with 3 parallel wells for each concentration. After continuing to culture for 24 hours, 100μL of MTT solution (1mg / mL) was added to each well and continued to incubate in a 37°C cell culture incubator for 4 hours. Finally, 150μL of dimethyl sulfoxide (DMSO) was added to each well containing cells to dissolve the formazan crystals, and then placed in a shaker at 37°C for 15 minutes away from light, and finally the absorbance at 490nm was measured using an enzyme reader. The absorbance of the experimental group, blank group (using only complete medium) and control group (using only complete medium to culture cells) was recorded as As, Ab, and Ac, respectively. The cell viability was calculated using the following formula:

[0147]

[0148] Test results such as Fig.10 When the concentration of the multifunctional conductive organic hydrogel soaking solution prepared by the present invention reaches 50 μg / mL, the survival rate of HUVECs, PC 12 and RAW 263.7 cells is greater than 90%, and the cell toxicity is relatively low.

[0149] 2. Cell live and dead staining

[0150] HUVECs, PC 12 and RAW 264.7 cells were cultured to the logarithmic growth phase and then seeded into 96-well microplates at a density of approximately 1×10 5 cells / cm 2 After incubating in a CO2 incubator (37°C, 5% CO2) for 24 hours, cells were cultured with hydrogel immersion solution (50 μg / mL) diluted with basal culture medium. The solution was changed every other day, and the cells were stained with AM / PI staining solution on the 1st, 3rd, and 5th days of culture. After incubation in the dark for 30 minutes, the cell survival status was observed under a fluorescence microscope and photographed.

[0151] The test results showed that the multifunctional conductive organic hydrogel Gel-TBA-EGaIn had excellent biocompatibility. Compared with the control group, the cell growth in the experimental group was even more vigorous ( Fig.11 ).

[0152] Based on the experimental results of the above hemolytic toxicity and antibacterial activity, it can be seen that the multifunctional conductive organic hydrogel provided by the present invention can have good biocompatibility while having strong antibacterial activity, revealing its potential to explore various applications as an epidermal sensor.

[0153] According to the above test results, the multifunctional conductive organic hydrogel provided by the present invention has different effects on the results by each parameter. For example, the moisturizing and antifreeze properties are related to the addition method of glycerol. Compared with water as a solvent, the moisturizing properties of the binary solvent method and the solvent replacement method (the present invention) are similar, but the binary solvent method will destroy the degree of cross-linking inside the gel. The high Gly concentration in the binary solvent method leads to a high crystal density, which weakens the Hofmeister effect and thus causes the mechanical properties of the gel to deteriorate. The electrical properties are related to the content of EGaIn. The mechanical properties are related to the content of TBA, EGaIn and the concentration of ammonium sulfate that triggers the Hofmeister effect. However, the optimal effect can only be achieved when the preparation raw materials and the preparation method are coordinated with each other: for the internal cross-linked structure of the multifunctional conductive organic hydrogel, the addition of TBA will react with gelatin to undergo a Schiff base reaction to enhance the ductility of the gel, and Ga 3+ Complexation reaction occurs with TBA and Gel; the Hofmeister effect induced by ammonium sulfate increases the crosslinking density inside the gel, thereby enhancing the strength of the gel; excessive TBA will precipitate, resulting in poor ductility of the conductive hydrogel; a small amount of EGaIn has too low conductivity to meet the conductivity requirements; excessive EGaIn and excessively high ammonium sulfate concentrations will break the optimal crosslinking balance, resulting in excessive mechanical strength and affecting the ductility of the gel.

[0154] In summary, the multifunctional conductive organic hydrogel provided by the present invention has excellent elongation at break, tensile modulus, conductivity, sensor sensitivity, sensor stability, high and low temperature performance, moisture retention, biocompatibility and antibacterial properties through the coordination of raw materials and optimization of parameters. It is precisely because of the above advantages that the multifunctional conductive organic hydrogel is expected to be used in the preparation of flexible sensing products, and the flexible sensing products have broad application prospects in the fields of skin-friendly sports and pressure monitoring.

[0155] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A multifunctional conductive organic hydrogel, characterized in that: The raw materials for preparing the multifunctional conductive organic hydrogel include: Gelatin, wherein the gelatin contains an amino group; Liquid metal, the liquid metal is dispersed in the gelatin; the liquid metal comprises a eutectic gallium-indium alloy; 2,3,4-trihydroxybenzaldehyde, the 2,3,4-trihydroxybenzaldehyde is complexed with the liquid metal and reacts and bonds with the amino groups on the gelatin; the mass ratio of the 2,3,4-trihydroxybenzaldehyde to the liquid metal is 1:2-10; Glycerol, the glycerol dispersed in the gelatin; The multifunctional conductive organic hydrogel is prepared by a preparation method comprising the following steps: S1. Providing an aqueous solution comprising the 2,3,4-trihydroxybenzaldehyde, and an aqueous dispersion comprising the gelatin; After dispersing the liquid metal in the aqueous solution, the obtained mixture is mixed with the aqueous dispersion to obtain a pre-gel suspension; S2. Cooling the pre-gel suspension and soaking it in a solvent replacement system; the solvent replacement system includes the glycerol.

2. The multifunctional conductive organic hydrogel according to claim 1, characterized in that: In step S1, the mass concentration of 2,3,4-trihydroxybenzaldehyde in the raw materials for preparing the pre-gel suspension is 1-8%.

3. The multifunctional conductive organic hydrogel according to claim 1, characterized in that: In step S1, the mass concentration of gelatin in the raw materials for preparing the pre-gel suspension is 15-25%.

4. The multifunctional conductive organic hydrogel according to claim 1, characterized in that: In step S2, in the solvent replacement system, the concentration of glycerol is 50-70%.

5. The multifunctional conductive organic hydrogel according to claim 1, characterized in that: In step S2, the solvent replacement system further includes ammonium sulfate.

6. A flexible sensing product, characterized in that: The raw materials for preparing the flexible sensing product include the multifunctional conductive organic hydrogel according to any one of claims 1 to 5.

7. Application of the flexible sensing product as claimed in claim 6 in motion monitoring and pressure monitoring.

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