Polyurethane ionic gel, preparation method, biological electrode and application

Abstract

The invention relates to polyurethane ionic gel, a preparation method, a biological electrode and application, the preparation method comprises the following steps: preparing a polyurethane elastomer by using small molecule diol as a hard segment and polycaprolactone-polytetrahydrofuran-polycaprolactone as a soft segment, and then preparing the polyurethane ionic gel by using the characteristic that polyurethane and ionic liquid are uniformly blended. The polyurethane ionic gel has good biocompatibility and environmental stability, and compared with polyurethane ionic gel independently taking polycaprolactone or polytetrahydrofuran as a soft segment, the prepared polyurethane ionic gel is lower in modulus, has better flexibility, and can be used for preparing the polyurethane ionic gel. And meanwhile, the material has the advantages of high mechanical property, ionic conductivity, biocompatibility, environmental stability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a polyurethane ion gel, a preparation method, a bioelectrode and an application thereof. Background Art

[0002] With the booming development of flexible wearable health monitoring devices, flexible bioelectrodes, as an important part thereof, have attracted wide attention. Hydrogels have become one of the important research directions in the field of flexible bioelectrode research in recent years due to their good ionic conductivity and biocompatibility. However, due to their high water content, most hydrogels can only maintain good conductivity and flexibility under mild conditions, and cannot cope with the performance degradation or even failure caused by water evaporation during long-term exposure or water freezing in a low-temperature environment, which severely limits the application of hydrogels in the field of bioelectrodes. Therefore, how to endow gels with good ionic conductivity, flexibility, biocompatibility and environmental stability has become one of the current research focuses.

[0003] Ionic liquids have a low freezing point, a low vapor pressure and good ionic conductivity, and have good compatibility with most polymers. Ionic liquids can be fixed in a polymer network through strong interactions with polymer segments to form a stable conductive ion gel. Some polymer materials, such as block copolymers of polyvinylidene fluoride, polyacrylates, polyzwitterions, polymethyl acrylate and polystyrene, have been used to prepare ion gel bioelectrodes to effectively solve the dilemmas faced by hydrogel bioelectrodes. However, most of the currently reported ion gels do not have good biocompatibility due to their polymer matrices, so it is difficult to be used as a bioelectrode for long-term wearing for physiological health monitoring. Polyurethane elastomer is a polymer material with high mechanical properties. Due to its adjustable molecular structure and simple synthesis, it has attracted wide attention from researchers as a substrate for bioelectrodes. For example, introducing polylactic acid into the polyurethane structure can prepare a biocompatible polyurethane material. In addition, many scholars have modified polyurethane with chitosan to obtain a new biomaterial with high mechanical properties and biocompatibility. However, this new biocompatible polyurethane material has a high modulus and poor flexibility and does not have ionic conductivity. Therefore, it is urgent to design a new polyurethane ion gel and its preparation method to endow the new polyurethane ion gel with good ionic conductivity, flexibility, biocompatibility and environmental stability, so as to meet the requirements of wearable health monitoring applications. Summary of the Invention

[0004] In order to overcome the above problems existing in the prior art, the present invention provides a polyurethane ion gel, a preparation method, a bioelectrode and an application thereof to solve the above problems existing in the prior art.

[0005] A preparation method of a polyurethane ion gel, comprising the following steps: S1. React polycaprolactone-poly(tetrahydrofuran)-polycaprolactone and diisocyanate in a solvent by heating to obtain polycaprolactone-poly(tetrahydrofuran)-polycaprolactone capped with isocyanate groups; S2. React the obtained polycaprolactone-poly(tetrahydrofuran)-polycaprolactone capped with isocyanate groups and a small molecule diol in a solvent by heating to obtain a polyurethane elastomer; S3. Dissolve the obtained polyurethane elastomer in a solvent, then mix it with an ionic liquid, and then remove the solvent to prepare a polyurethane ion gel; The small molecule diol includes at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 2,3-butanediol.

[0006] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The solvent includes at least one of acetone, tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform, or dichloromethane.

[0007] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The diisocyanate includes at least one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or methylcyclohexyl diisocyanate; The molar amount of the diisocyanate is 2.0 to 2.2 times the molar amount of polycaprolactone-poly(tetrahydrofuran)-polycaprolactone.

[0008] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The ionic liquid is 1-ethyl-3-methylimidazolium hexafluorophosphate or 1-butyl-3-methylimidazolium hexafluorophosphate; the addition amount of the ionic liquid is 2% to 50% of the mass of the polyurethane elastomer.

[0009] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. In step S2, the conditions of the heating reaction are as follows: In a vacuum environment, react at 70 to 90 °C for 0.5 to 48 hours; The molar amount of the small molecule diol is 1.0 to 1.05 times the molar amount of polycaprolactone-poly(tetrahydrofuran)-polycaprolactone.

[0010] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. In step S1, the conditions of the heating reaction are as follows: Under a protective atmosphere, react at 70 to 90 °C for 0.5 to 24 hours.

[0011] For the aspects and any possible implementation manners described above, a further implementation manner is provided, wherein the solvent is removed by vacuum pumping or by adding a poor solvent; The poor solvent includes at least one of methanol, petroleum ether, ether, n-pentane or n-hexane.

[0012] The present invention also provides a polyurethane ion gel, which is prepared by using the preparation method described above.

[0013] The present invention also provides a polyurethane ion gel bioelectrode, which includes a conductive PET and the polyurethane ion gel; the polyurethane ion gel is attached to the surface of the conductive PET.

[0014] The present invention also provides an application of the polyurethane ion gel bioelectrode in a flexible wearable device.

[0015] Advantages of the present invention For the polyurethane ion gel, preparation method, bioelectrode and application of the present invention, the preparation method uses small molecule diol as the hard segment and polycaprolactone-poly(tetrahydrofuran)-polycaprolactone as the soft segment to prepare a polyurethane elastomer, and then utilizes the characteristic of uniform blending of polyurethane and ionic liquid to prepare a polyurethane ion gel. The polyurethane ion gel has good biocompatibility and environmental stability, and compared with the polyurethane ion gel with polycaprolactone or poly(tetrahydrofuran) alone as the soft segment, the polyurethane ion gel prepared by the present invention has a lower modulus, better flexibility, and at the same time has the advantages of high mechanical properties, ionic conductivity, biocompatibility, environmental stability, etc. Description of the drawings

[0016] Figure 1 Schematic diagram of the appearance of the materials in Example 1 and Comparative Examples 1-2; Figure 2 Schematic diagram of the stress-strain curves in Example 1 and Comparative Examples 1-2; Figure 3 EIS impedance spectra of Examples 1-3 and Comparative Examples 3-4; Figure 4 Cell culture results of the control group and the material group observed by a 40-fold microscope of an application microscope; Figure 5 Detection results of cell line survival rate; Figure 6 Detection results of rat blood routine and biochemistry; Figure 7 Detection results of electromyogram signals; Figure 8 Flow chart of the method of the present invention. Detailed implementation manners

[0017] It should be clear that the embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0019] Similar technologies and methods should be regarded as falling within the scope of protection of the present invention. To make the technical problems to be solved, technical solutions and advantages of the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0020] As Figure 8 shown, the present invention provides a method for preparing a polyurethane ion gel, comprising the following steps: a. Heating and reacting polycaprolactone-poly(tetrahydrofuran)-polycaprolactone and diisocyanate in a solvent to obtain polycaprolactone-poly(tetrahydrofuran)-polycaprolactone capped with isocyanate groups; b. Heating and reacting the polycaprolactone-poly(tetrahydrofuran)-polycaprolactone capped with isocyanate groups obtained in step a and a small molecule diol in a solvent to obtain a polyurethane elastomer; c. Dissolving the polyurethane elastomer obtained in step b in a solvent, then mixing it with an ionic liquid, and then removing the solvent to prepare a polyurethane ion gel.

[0021] Among them, polycaprolactone is an organic polymer with good biocompatibility, biodegradability, thermal stability, thermoplasticity and molding processability, etc. Poly(tetrahydrofuran) is a polyether diol with good flexibility and water resistance, etc. The present invention uses a polycaprolactone-poly(tetrahydrofuran)-polycaprolactone block copolymer formed by combining the two to prepare a polyurethane ion gel.

[0022] The small molecule diol includes but is not limited to at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol or 2,3-butanediol, and they are all low molecular weight aliphatic diols, and the synthesized polyurethane has good mechanical properties and biocompatibility.

[0023] The preparation method of the polyurethane ion gel provided by the present invention uses small molecule diols as the hard segments and polycaprolactone-poly(tetrahydrofuran)-polycaprolactone as the soft segments to prepare a polyurethane elastomer. The hard segments used are aliphatic diols, which endow the polyurethane with good mechanical properties and biocompatibility. The soft segments used are block copolymers of polycaprolactone and poly(tetrahydrofuran), which have good biocompatibility and can avoid the crystallization of polyurethane at room temperature, thereby ensuring that the polyurethane elastomer has high flexibility and biocompatibility. Then, the polyurethane ion gel is prepared by utilizing the characteristic of uniform blending of polyurethane and ionic liquid, so that the prepared polyurethane ion gel has good biocompatibility and environmental stability. Moreover, compared with the polyurethane ion gel using polycaprolactone or poly(tetrahydrofuran) alone as the soft segment, the polyurethane ion gel prepared by the present invention does not crystallize and thus has a lower modulus, better flexibility and ionic conductivity.

[0024] In some alternative embodiments, the solvent includes but is not limited to at least one of acetone, tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform or dichloromethane. These are all good solvents for polyurethane and can dissolve polyurethane well.

[0025] It should be noted that the solvent in the present invention is used to dissolve the reactants to provide a solution environment, and other well-known solvents can also be selected, which is not limited in the present invention.

[0026] In some alternative embodiments, the diisocyanate includes but is not limited to at least one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or methylcyclohexyl diisocyanate. These are all aliphatic or cycloaliphatic diisocyanates and do not contain benzene rings, thereby ensuring the biocompatibility of the polyurethane; The molar amount of the diisocyanate is 2.0 - 2.2 times the molar amount of polycaprolactone-poly(tetrahydrofuran)-polycaprolactone. For example, it can be 2.0 times, 2.1 times or 2.2 times. At this ratio, the isocyanate can more fully cap the polycaprolactone-poly(tetrahydrofuran)-polycaprolactone and there will be no excessive unreacted diisocyanate remaining.

[0027] In some alternative embodiments, in step a, the conditions for the heating reaction are as follows: Under a protective atmosphere, react at 70 - 90 °C for 0.5 - 24 hours. The temperature for the heating reaction can be, for example, but not limited to 70 °C, 80 °C or 90 °C. At this temperature, the diisocyanate can fully react with polycaprolactone-poly(tetrahydrofuran)-polycaprolactone without self-polymerization. According to different reaction temperatures, the reaction time can be, for example, but not limited to 0.5 hours, 10 hours, 20 hours or 24 hours.

[0028] In some alternative embodiments, the protective atmosphere can be, for example, but not limited to, nitrogen or argon.

[0029] In some alternative embodiments, in step b, the conditions for the heating reaction are as follows: In a vacuum environment, the reaction is carried out at 70 - 90 °C for 0.5 - 48 hours. The temperature for the heating reaction can be, for example, but not limited to, 70 °C, 80 °C or 90 °C. At this temperature, the small molecule diol can react fully with the isocyanate end-capping. According to different reaction temperatures, the reaction time can be, for example, but not limited to, 0.5 hour, 10 hours, 24 hours or 48 hours.

[0030] The molar amount of the small molecule diol is 1.0 - 1.05 times the molar amount of polycaprolactone - polytetrahydrofuran - polycaprolactone. It can be, for example, 1.0 times, 1.03 times or 1.05 times. The polyurethane elastomer synthesized at this ratio has a high enough molecular weight to ensure the flexibility and stability of the material.

[0031] In some alternative embodiments, the ionic liquid includes but is not limited to 1-ethyl-3-methylimidazolium hexafluorophosphate or 1-butyl-3-methylimidazolium hexafluorophosphate, both of which are ionic liquids with good biocompatibility; The addition amount of the ionic liquid is 2% - 50% of the mass of the polyurethane elastomer. It can be, for example, but not limited to, 2%, 25% or 50%. If the amount of the ionic liquid outside this range is too low, the polyurethane ion gel will not have ionic conductivity. If the amount of the ionic liquid is too high, the ionic liquid will overflow, affecting the adhesion of the polyurethane ion gel.

[0032] In some alternative embodiments, the method for removing the solvent includes vacuum pumping or removing the solvent by adding a poor solvent. After the solvent is removed, the polyurethane elastomer can be obtained. The poor solvent includes but is not limited to at least one of methanol, petroleum ether, ether, n-pentane or n-hexane.

[0033] In a second aspect, the present invention provides a polyurethane ion gel prepared by the above preparation method.

[0034] This polyurethane ion gel has good biocompatibility and environmental stability. Compared with the polyurethane ion gel using only polycaprolactone or polytetrahydrofuran as the soft segment, the polyurethane ion gel of the present invention has a polycaprolactone - polytetrahydrofuran - polycaprolactone soft segment, so it does not crystallize at room temperature and has a lower modulus, and has better flexibility and ionic conductivity.

[0035] Because the ionic liquid used in the preparation has a low freezing point and an extremely low vapor pressure, the polyurethane ion gel bioelectrode has good stability and can be used for electromyogram signal monitoring.

[0036] The present invention will be further illustrated by specific examples and comparative examples below. However, it should be understood that these examples are only for more detailed illustration and should not be construed as limiting the present invention in any way.

[0037] Example 1 A preparation method of polyurethane ion gel, comprising the following steps: 1) Dissolve PCL-PTHF-PCL (Mn≈2000, the polyurethane elastomer synthesized with this molecular weight has the best mechanical properties, and too large or too small molecular weight will lead to a decrease in the mechanical properties of the polyurethane elastomer, 2.0 g, 1.0 mmol) in dehydrated tetrahydrofuran, and react with 2.15 molar equivalents of isophorone diisocyanate IPDI (0.47 g, 2.1 mmol) at 75 °C under argon protection for 24 hours to prepare a prepolymer PCL-PTHF-PCL with isocyanate-terminated; 2) Dissolve the prepolymer obtained in step 1) in dehydrated tetrahydrofuran, add 1.05 molar equivalents of 1,4-butanediol (Mn≈90.12, 0.04506 g, 0.5 mmol) for chain extension, and react in a vacuum drying oven at 90 °C for 48 hours to obtain a polyurethane elastomer; 3) Dissolve the polyurethane elastomer obtained in step 2) in N,N-dimethylformamide, and then add 10% of [EMIM]PF6 ionic liquid of the polyurethane elastomer, and stir well to obtain a polyurethane ion gel solution.

[0038] 4) Cast the polyurethane ion gel solution obtained in step 3) on a polytetrafluoroethylene mold, and wait for the solvent to evaporate completely in a vacuum drying oven to prepare a polyurethane ion gel.

[0039] Example 2 A preparation method of polyurethane ion gel, which is different from Example 1 in that the addition amount of [EMIM]PF6 ionic liquid is 2% of the polyurethane elastomer.

[0040] Example 3 A preparation method of polyurethane ion gel, which is different from Example 1 in that the addition amount of [EMIM]PF6 ionic liquid is 50% of the polyurethane elastomer.

[0041] Example 4 A preparation method of polyurethane ion gel, comprising the following steps: 1) Dissolve PCL-PTHF-PCL (Mn≈2000, 2.0 g, 1.0 mmol) in dehydrated acetone, and react with 2 molar equivalents of dicyclohexylmethane diisocyanate HMDI at 70 °C under argon protection for 20 hours to prepare a prepolymer, namely isocyanate-terminated PCL-PTHF-PCL; 2) Dissolve the prepolymer obtained in step 1) in dehydrated acetone, add 1.03 molar equivalents of ethylene glycol for chain extension, and react in a vacuum drying oven at 70 °C for 40 hours to obtain a polyurethane elastomer; 3) Dissolve the polyurethane elastomer obtained in step 2) in acetone, then add 2% of [BMIM]PF6 ionic liquid based on the polyurethane elastomer, and stir well to obtain a polyurethane ion gel solution.

[0042] 4) Cast the polyurethane ion gel solution obtained in step 3) on a polytetrafluoroethylene mold, and then remove the solvent in petroleum ether to prepare a polyurethane ion gel.

[0043] Example 5 A method for preparing a polyurethane ion gel, comprising the following steps: 1) Dissolve PCL-PTHF-PCL (Mn≈2000, 2.0 g, 1.0 mmol) in dehydrated N-methylpyrrolidone, and react with 2.2 molar equivalents of hexamethylene diisocyanate HDI at 90 °C under argon protection for 0.5 hour to prepare a prepolymer, namely isocyanate-terminated PCL-PTHF-PCL; 2) Dissolve the prepolymer obtained in step 1) in dehydrated N-methylpyrrolidone, add 1 molar equivalent of 1,3-propanediol for chain extension, and react in a vacuum drying oven at 80 °C for 0.5 hour to obtain a polyurethane elastomer; 3) Dissolve the polyurethane elastomer obtained in step 2) in N-methylpyrrolidone, then add 50% of [EMIM]PF6 ionic liquid based on the polyurethane elastomer, and stir well to obtain a polyurethane ion gel solution.

[0044] 4) Cast the polyurethane ion gel solution obtained in step 3) on a polytetrafluoroethylene mold, and wait for the solvent to evaporate completely in a vacuum drying oven to prepare a polyurethane ion gel.

[0045] Comparative Example 1 A method for preparing a polyurethane ion gel, which is different from Example 1 in that PCL-PTHF-PCL is replaced with an equal amount of polycaprolactone PCL-OH (Mn≈2000).

[0046] Comparative Example 2 A preparation method of a polyurethane ion gel, which is different from Example 1 in that PCL-PTHF-PCL is replaced with an equal amount of polytetrahydrofuran PTHF (Mn≈2000).

[0047] Comparative Example 3 A preparation method of a polyurethane ion gel, which is different from Example 2 in that PCL-PTHF-PCL is replaced with an equal amount of polycaprolactone PCL-OH (Mn≈2000).

[0048] Comparative Example 4 A preparation method of a polyurethane ion gel, which is different from Example 2 in that PCL-PTHF-PCL is replaced with an equal amount of polytetrahydrofuran PTHF (Mn≈2000).

[0049] Test Example 1: The appearances of the polyurethane ion gels of Example 1 and Comparative Examples 1-2 are as Figure 1 shown. Polyurethanes with PCL-OH (Comparative Example 1) and PTHF (Comparative Example 2) as soft segments crystallized and turned milky white at room temperature, while the polyurethane elastomer with PCL-PTHF-PCL (Example 1) as the soft segment did not crystallize and still had a certain transparency at room temperature. A universal testing machine was used to characterize the mechanical properties of the above materials (including the materials in the initial state, that is, the freshly prepared polyurethane ion gel, and the materials after being placed in air at room temperature for one month), such as the fracture stress, fracture strain, Young's modulus, toughness, fracture energy, etc. The results are as Figure 2 shown. The fracture stress of the PCL-PTHF-PCL polyurethane ion gel in the initial state was 5 MPa, the fracture strain was 8.4 mm / mm, the fracture stress of the PCL-OH polyurethane ion gel was 12 MPa, the fracture strain was 5 mm / mm, and the fracture stress of the PTHF polyurethane ion gel was 7.5 MPa, and the fracture strain was 2.9 mm / mm, as shown in Table 1.

[0050] It can be seen from the above results that the polyurethane ion gel prepared with PCL-PTHF-PCL as the soft segment has better transparency and high flexibility. By calculating the linear change stage of the stress-strain curve, the Young's modulus of the PCL-PTHF-PCL polyurethane ion gel was 0.5 MPa, which was lower than that of the polyurethane ion gels with PCL-OH (2.4 MPa) and PTHF (10 MPa) as soft segments, and had better flexibility. In addition, after the PCL-PTHF-PCL polyurethane ion gel was placed in air at room temperature for 1 month, the mechanical properties of the material remained basically unchanged, indicating that it had high environmental stability.

[0051] Table 1 Performance comparison between Example 1 and Comparative Examples 1-2

[0052] Experimental Example 2: An electrochemical workstation was used to characterize the ionic conductivities of the materials of Examples 1 - 3 and Comparative Examples 3 - 4 (including the polyurethane ion gels prepared immediately in Examples 1 - 3 and Comparative Examples 3 - 4, and the materials of Example 3 after being placed in air at room temperature for one month). The results are as Figure 3 shown. When the ionic content was 2% (in Examples 2 and Comparative Examples 3 - 4), the ionic conductivity of the PCL - PTHF - PCL soft - segment polyurethane ion gel was 3.2×10 -6 S / cm, and the ionic conductivities of the PCL - OH (Comparative Example 3) and PTHF (Comparative Example 4) polyurethane ion gels were 1.75×10 -6 S / cm and 2.2×10 -6 S / cm, respectively. As shown in Table 2, it can be seen that the PCL - PTHF - PCL polyurethane ion gel has higher ionic conductivity, and the ionic conductivity of the PCL - PTHF - PCL polyurethane ion gel increases with the increase of the ionic liquid content. When the ionic liquid content is 50%, its ionic conductivity reaches 3×10 -5 S / cm (Example 3). After being placed in air at room temperature for 1 month, the ionic conductivity of the PCL - PTHF - PCL polyurethane ion gel (Example 3) remains basically unchanged.

[0053] Table 2. Performance comparison of Example 2 and Comparative Examples 3 and 4

[0054] Experimental Example 3 The polyurethane ion gel constructed in Application Example 4 was used for in vitro cell co - culture experiments and in vivo animal experiments on rats to verify the biocompatibility of the polyurethane ion gel. The experimental steps are as follows: The human biliary epithelial cell line (cultured in the laboratory, normally cultured in 10% FBS + MEM medium) was seeded on the bottom of a 24 - well plate. The polyurethane ion gel was placed in a transwell chamber, and the chamber was placed in the 24 - well plate. Each well was stratified, with the polyurethane ion gel placed in the upper layer and the human biliary epithelial cell line seeded in the bottom layer. The human biliary epithelial cell line and the polyurethane ion gel were co - cultured in a liquid medium and grouped. One group was the co - culture of the human biliary epithelial cell line and the polyurethane ion gel for 1 week (experimental group), and one group was the human biliary epithelial cell line cultured alone for 1 week (control group), that is, the polyurethane gel was not placed in this control group. On the 1st, 3rd, 5th, and 7th days, the morphological changes of the two cell lines were observed under a 40 - fold microscope and counted; meanwhile, on the 1st, 3rd, 5th, and 7th days, an apoptosis experiment was performed on the two cell lines using a cck8 kit.

[0055] The experimental results of the experimental group and the control group are as follows Figure 4 and Figure 5 shown. It indicates that although polyurethane gel was added to the experimental group, it did not cause apoptosis of cells. The mean CCK8 OD450 absorbance values of the control group on the 1st, 3rd, 5th, and 7th days were 0.1486, 0.4197, 1.0043, and 1.4704 respectively, and the mean CCK8 OD450 absorbance values of the experimental group on the 1st, 3rd, 5th, and 7th days were 0.2120, 0.4325, 0.9965, and 1.5118 respectively. There was no statistical difference between the two groups of data, and the p-value was 0.4169, which was greater than 0.05. The method of one-way ANOVA was used to perform statistical analysis on the two groups of data, and the obtained p-value was 0.4169. If this p-value was less than 0.05, it would prove that there was a statistical difference between the two groups of data; if it was greater than 0.05, it would prove that there was no statistical difference between the two groups of data. The two groups of experimental data proved that there was no significant difference in the absorbance values of the two groups of cells, that is, there was no significant difference in the number of cells, that is, polyurethane gel did not cause apoptosis of cells.

[0056] 2) Three female SD rats, 4 - 6 weeks old, were selected. The polyurethane ion gel obtained in the embodiment of the present invention was used, and a rectangle with a size of 0.5 cm × 0.5 cm was cut. One piece was implanted in the muscle layer of each SD rat. One SD rat was selected at the 2nd week, 4th week, and 8th week respectively, and peripheral blood was collected for routine blood and biochemical tests.

[0057] The SD rats used in this part were provided by Beijing Vital River Laboratory Animal Technology Co., Ltd. The experimental results are as follows Figure 6It shows that the polyurethane gel does not cause abnormalities in the blood routine, liver and kidney functions of experimental animals. The mean white blood cell count at 2 weeks is 10.3×10^9 / L, at 4 weeks is 7.3×10^9 / L, and at 8 weeks is 6.9×10^9 / L, indicating that the white blood cell count is within the normal range (reference value: 5.0 - 15.0×10^9 / L); the neutrophil count (the mean neutrophil count at 2 weeks is 1.5×10^9 / L, at 4 weeks is 1.0×10^9 / L, and at 8 weeks is 1.4×10^9 / L) is also within the normal range (reference value: 1.1 - 4.0×10^9 / L); the lymphocyte count (the mean lymphocyte count at 2 weeks is 6.4×10^9 / L, at 4 weeks is 6.7×10^9 / L, and at 8 weeks is 5.6×10^9 / L) is also within the normal range (reference value: 4.0 - 10.0×10^9 / L), ALT (the mean alanine aminotransferase at 2 weeks is 58.00 U / L, at 4 weeks is 54.33 U / L, and at 8 weeks is 52.67 U / L) is also within the normal range (reference value: 41.47 - 195.65 U / L); serum albumin (the mean serum albumin at 2 weeks is 30.20 g / L, at 4 weeks is 27.80 g / L, and at 8 weeks is 28.67 g / L) is also within the normal range (reference value: 21.16 - 34 g / L); serum creatinine (the mean serum creatinine at 2 weeks is 30.33 μmol / L, at 4 weeks is 33.67 μmol / L, and at 8 weeks is 37.00 μmol / L) is also within the normal range (reference value: 10.90 - 118.07 μmol / L), and there is no inflammatory reaction such as redness, ulceration, and necrosis in the local tissue of the experimental animals with the polyurethane gel set, indicating that the polyurethane gel has good biocompatibility.

[0058] As a disclosed embodiment, the present invention also provides a polyurethane ion gel bioelectrode, which includes a conductive PET and the polyurethane ion gel described above; the polyurethane ion gel is attached to the surface of the conductive PET. The following is proved by Test Example 4: Use the polyurethane gel prepared in Application Example 5 to construct a bioelectrode, and connect this bioelectrode to an electromyogram signal acquisition device to collect the forearm muscle electrical signals of the human body. The experimental steps are as follows: 1) Dissolve the prepared polyurethane gel in DMF to obtain a polyurethane gel solution, and then drop it on the conductive PET and dry it for 6 hours to prepare a bioelectrode with the polyurethane gel. Paste 2 bioelectrodes on the human forearm and fix them, 1 piece is pasted on the proximal part of the forearm, and 1 piece is pasted on the distal part of the forearm.

[0059] 2) Connect two bioelectrodes to the electromyogram signal acquisition device and debug the parameters of the electromyogram signal acquisition device. The specific parameters are as follows: the signal acquisition frequency is 5 - 20 Hz. Move the human forearm by bending the fingers, making a fist, and releasing the fist, and record the changes and patterns of the electromyogram signals during the movement of the human forearm.

[0060] The results are as Figure 7 shown: When the human forearm is placed flat on the table during the test, no obvious electrical signals are generated by the electromyogram signal acquisition device. When the human moves the middle finger, with each movement, obvious electrical signal changes can be seen on the electromyogram signal acquisition device as shown in Figure 7 (a). When the middle finger bends, the bioelectrode will collect the bioelectric pulse signal A, and then when the finger returns to the bent state, a bioelectric pulse signal B with a smaller peak value will be generated. Similarly, during the test, when the human makes a fist and releases the fist each time, obvious electrical signal changes can be seen on the acquisition device, as shown in Figure 7 (b). When making a fist, the bioelectrode will collect the bioelectric pulse signal C, and after releasing the fist, a pulse signal D with a comparable peak value will be generated. Through the above experiments, it is proved that the bioelectrode constructed with PCL - PTHF - PCL polyurethane gel has a relatively stable bioelectric signal acquisition ability and meets the requirements of flexible wearable health monitoring applications.

[0061] As an embodiment disclosed in the present invention, the present invention also discloses the application of the bioelectrode in flexible wearable devices. For example, it can be used in flexible electrocardiogram detection devices, muscle strength detection devices, etc., which can monitor the physical health and recovery status of postoperative patients at any time and promote the development of flexible wearable health monitoring technology.

[0062] The above description shows and describes several preferred embodiments of the present invention. However, as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the application concept described herein through the above teachings or the technology or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of a polyurethane ion gel, characterized in that, It includes the following steps: S1. Heat and react polycaprolactone - polytetrahydrofuran - polycaprolactone and diisocyanate in a solvent to obtain polycaprolactone - polytetrahydrofuran - polycaprolactone capped with isocyanate groups; S2. Heat and react the obtained polycaprolactone - polytetrahydrofuran - polycaprolactone capped with isocyanate groups and small molecule diol in a solvent to obtain a polyurethane elastomer; S3. Dissolve the obtained polyurethane elastomer in a solvent, then mix it with an ionic liquid, and then remove the solvent to prepare a polyurethane ion gel; The small molecule diol includes at least one of ethylene glycol, 1,3 - propanediol, 1,4 - butanediol or 2,3 - butanediol.

2. The preparation method according to claim 1, wherein The solvent includes at least one of acetone, tetrahydrofuran, N,N - dimethylformamide, N - methylpyrrolidone, dimethyl sulfoxide, chloroform or dichloromethane.

3. The preparation method according to claim 1, wherein The diisocyanate includes at least one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or methylcyclohexyl diisocyanate; The molar amount of the diisocyanate is 2.0 - 2.2 times the molar amount of polycaprolactone - polytetrahydrofuran - polycaprolactone.

4. The preparation method according to claim 1, characterized in that, The ionic liquid is 1 - ethyl - 3 - methylimidazolium hexafluorophosphate or 1 - butyl - 3 - methylimidazolium hexafluorophosphate; the addition amount of the ionic liquid is 2% - 50% of the mass of the polyurethane elastomer.

5. The preparation method according to claim 1, wherein In step S2, the conditions of the heat reaction are as follows: React at 70 - 90 °C for 0.5 - 48 hours in a vacuum environment; The molar amount of the small molecule diol is 1.0 - 1.05 times the molar amount of polycaprolactone - polytetrahydrofuran - polycaprolactone.

6. The preparation method according to claim 1, characterized in that, In step S1, the conditions of the heat reaction are as follows: React at 70 - 90 °C for 0.5 - 24 hours under a protective atmosphere.

7. The preparation method according to claim 1, wherein The solvent is removed by vacuum pumping or by adding a poor solvent; The poor solvent includes at least one of methanol, petroleum ether, ether, n - pentane or n - hexane.

8. A polyurethane ion gel, characterized in that, The polyurethane ion gel is prepared by the preparation method described in any one of claims 1 - 7.

9. A polyurethane ion gel bioelectrode, characterized in that, It includes conductive PET and the polyurethane ion gel described in claim 8; the polyurethane ion gel is attached to the surface of the conductive PET.

10. Application of the polyurethane ion gel bioelectrode described in claim 9 in a flexible wearable device.

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