IL-coated PVDF-HFP / PU flexible ionic gel electrode and preparation method and application thereof

Abstract

The invention discloses an IL-coated PVDF-HFP / PU flexible ionic gel electrode and a preparation method and application thereof, and belongs to the technical field of composite flexible materials and neural interfaces. The IL-coated PVDF-HFP / PU flexible ionic gel electrode provided by the invention has high ionic conductivity, stretchability, flexibility and excellent signal stability and sensitivity, and can be used as a neural interface for monitoring epidermal and deep muscle electric signals. The two-component ionic liquid has movable anions and cations with different volumes, under the action of biological tissue electric signals, migration distribution of the anions and the cations in the two-component ionic liquid is remarkably changed, ionic current is generated, and sensitive signal conduction is achieved. Besides, the flexible ionic gel electrode and biological tissues have good dynamic compliance and stability in a physiological environment, long-term stable signal monitoring and electric signal input can be carried out on deep electromyographic signals, and bidirectional signal transmission is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite flexible materials and neural interfaces, and in particular relates to an IL@PVDF-HFP / PU flexible ion gel electrode and a preparation method and application thereof. Background Art

[0002] Neural interfaces are the key bridge between biological tissues and external electronic devices. Among them, neural microelectrodes are the core components for recording bioelectric signals to capture movement patterns or injecting charges into biological tissues to regulate biological functions. In the past few decades, neural interfaces have developed rapidly, and several typical implantable neural electrodes have been successfully implemented in human applications. Due to the different charge transfer behaviors between neural electrodes and biological tissues / cells, effective and stable charge transfer is crucial to the construction of neural interfaces.

[0003] Conventional neural electrodes made of metal or carbon materials mainly rely on free electrons as mobile charges to communicate with biological tissues. Although they perform well in terms of conductivity, the effective interfacial charge transfer between electrons and biological tissues is limited. This limitation stems from the fact that signal transmission in human biological systems mainly involves the transport of ions and small molecules. When ions are used as charge carriers in biological tissues, the conductivity of the tissue is significantly higher than using electrons and holes as charge carriers.

[0004] Ion-conducting hydrogel (ICHs) electrodes exhibit ionic conductivity similar to that of biological tissues, enabling the exchange of material information with surrounding tissues through ion transfer. This fundamentally avoids the need for conversion between electronic and ionic signals, thereby avoiding the above-mentioned problems. However, the disadvantage of ICH electrodes is that they dehydrate rapidly, often resulting in a loss of flexibility and conductivity, significantly limiting their effectiveness and reliability in practical applications. Ion-conducting gels (ICGs) are prepared by introducing ionic liquids (ILs) into polymer networks. The mechanical properties and stability of the gel can be adjusted by utilizing the interaction between ILs and polymer networks, thereby overcoming the shortcomings of ICHs due to their complete non-volatility and high chemical stability. However, the ionic conductivity of existing ICHs is low, which restricts the development of highly reliable neural electrode interfaces.

[0005] Therefore, there is an urgent need for an ion conductive gel with high ionic conductivity to solve the above problems. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes an IL@PVDF-HFP / PU flexible ion gel electrode and a preparation method and application thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The invention provides an IL@PVDF-HFP / PU flexible ion gel electrode, comprising a polymer substrate and a two-component ionic liquid; the polymer substrate is polyvinylidene fluoride-hexafluoropropylene / polyurethane, and the two-component ionic liquid is 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide ([EMIOTf]) and 1-vinyl-3-butylimidazole chloride ([VBIM][Cl]).

[0009] Preferably, the mass proportion of the two-component ionic liquid in the IL@PVDF-HFP / PU flexible ion gel electrode is 30%.

[0010] Preferably, the mass ratio of polyvinylidene fluoride-hexafluoropropylene to polyurethane in the polyvinylidene fluoride-hexafluoropropylene / polyurethane is 4:1.

[0011] Preferably, the mass ratio of the 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide to 1-vinyl-3-butylimidazolium chloride is 1:1.

[0012] The present invention provides a method for preparing the IL@PVDF-HFP / PU flexible ion gel electrode described in the above technical solution, comprising the following steps:

[0013] (1) mixing polyvinylidene fluoride-hexafluoropropylene and polyurethane with N,N-dimethylacetamide, and heating and stirring to obtain a PVDF-HFP / PU transparent solution;

[0014] (2) adding a two-component ionic liquid to the PVDF-HFP / PU transparent solution obtained in step (1), and stirring to obtain a mixed solution;

[0015] (3) Pour the mixed solution obtained in step (2) into a culture dish, let it stand and dry it to obtain the IL@PVDF-HFP / PU flexible ion gel electrode.

[0016] Preferably, in step (1), the concentration of PVDF-HFP / PU in the PVDF-HFP / PU transparent solution is 0.083 g / mL.

[0017] Preferably, in step (1), the heating and stirring temperature is 80° C., and the heating and stirring time is 2 h.

[0018] Preferably, in step (2), the stirring time is 12 hours.

[0019] Preferably, in step (3), the drying temperature is 80° C. and the drying time is 2 h.

[0020] The present invention also provides the use of the IL@PVDF-HFP / PU flexible ion gel electrode described in the above technical solution in monitoring electromyographic signals.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] (1) The present invention uses a polymer composite material as a substrate, which has prolonged in vivo stability and excellent thin thickness and stretchability.

[0023] (2) The flexible ion gel electrode provided by the present invention can transmit electrophysiological and electrical stimulation signals during conscious and autonomous movements for up to 7 days.

[0024] (3) The complex but balanced intermolecular interactions within the flexible ion gel electrode provided by the present invention can stably and weakly capture ionic species while enabling them to have high mobility in the electric field and to be transmitted with high sensitivity in the AC electric field.

[0025] (4) The flexible ion gel electrode provided by the present invention has a thin thickness and high flexibility, enabling it to be seamlessly attached to the muscle during cyclic flexion and contraction.

[0026] (5) When the flexible ion gel electrode provided by the present invention is used as a stimulation electrode, the high charge storage and injection capabilities make the pacing threshold voltage low (<0.5V). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 Schematic diagram of the conductive mechanism of the flexible ion gel electrode prepared in Example 1;

[0029] Figure 2 Surface scanning electron microscopy images of the flexible ion gel electrodes prepared in Example 1 and Comparative Examples 1-2;

[0030] Figure 3 The conductivity diagram of the flexible ion gel electrodes prepared in Example 1 and Comparative Examples 3-6;

[0031] Figure 4 The stretchability and bendability diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1;

[0032] Figure 5 This is a monitoring diagram of the epidermal electromyographic signal of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1;

[0033] Figure 6 This is a deep electromyographic signal monitoring diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1;

[0034] Figure 7 This is the electrophysiological stimulation diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] An embodiment of the present invention provides an IL@PVDF-HFP / PU flexible ion gel electrode, comprising a polymer substrate and a two-component ionic liquid; the polymer substrate is polyvinylidene fluoride-hexafluoropropylene / polyurethane, and the two-component ionic liquid is 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and 1-vinyl-3-butylimidazole chloride.

[0038] The IL@PVDF-HFP / PU flexible ion gel electrode provided by the present invention has high ionic conductivity, stretchability, flexibility, excellent signal stability and sensitivity, and can be used as a neural interface for monitoring epidermal and deep muscle electrical signals. Compared with the single-component electrolyte using only [EMIOTf] or [VBIM][Cl], the two-component ionic liquid has movable anions and cations of different volumes. Under the action of the electrical signal of the biological tissue, the migration distribution of the anions and cations in the two-component ionic liquid changes significantly, generating ion current and realizing sensitive signal conduction. In addition, the flexible ion gel electrode has good dynamic compliance with biological tissue and stability in the physiological environment, and can perform long-term stable signal monitoring and electrical signal input of deep electromyographic signals, realize bidirectional signal transmission, and provide a new platform for the development of ion neural electrodes suitable for long-term stable implantation.

[0039] In a preferred embodiment, the mass proportion of the two-component ionic liquid in the IL@PVDF-HFP / PU flexible ion gel electrode is 30%. The doping of the two-component ionic liquid (IL) of the present invention can make the flexible ion gel electrode have uniform microphase separation and amorphous structure, and this microphase separation structure shows a positive correlation with the addition of IL; at the same time, the doping of IL increases the density of charge carriers and improves the conductivity of the flexible ion gel electrode. With the increase of IL content, the conductivity shows a significant upward trend, and the optimal conductivity is shown when the content is 30%.

[0040] In a preferred embodiment, the mass ratio of polyvinylidene fluoride-hexafluoropropylene to polyurethane in the polyvinylidene fluoride-hexafluoropropylene / polyurethane is 4: 1. The present invention uses the electrochemical stability and good film-forming properties of polyvinylidene fluoride-hexafluoropropylene to give the flexible ion gel electrode excellent electrochemical stability and mechanical strength, and uses the flexibility of polyurethane to give the flexible ion gel electrode a stretchable effect.

[0041] In a preferred embodiment, the mass ratio of 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide to 1-vinyl-3-butylimidazolium chloride is 1: 1. In the present invention, the amount of 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and 1-vinyl-3-butylimidazolium chloride is controlled within the above ratio, so that the IL@PVDF-HFP / PU flexible ion gel electrode contains mobile anions and cations of different volumes.

[0042] The present invention provides a method for preparing the IL@PVDF-HFP / PU flexible ion gel electrode described in the above technical solution, comprising the following steps:

[0043] (1) mixing polyvinylidene fluoride-hexafluoropropylene and polyurethane with N,N-dimethylacetamide, and heating and stirring to obtain a PVDF-HFP / PU transparent solution;

[0044] (2) adding a two-component ionic liquid to the PVDF-HFP / PU transparent solution obtained in step (1), and stirring to obtain a mixed solution;

[0045] (3) Pour the mixed solution obtained in step (2) into a culture dish, let it stand and dry it to obtain the IL@PVDF-HFP / PU flexible ion gel electrode.

[0046] The present invention prepares the IL@PVDF-HFP / PU flexible ion gel electrode by a tape casting method, which has simple operation and low raw material cost.

[0047] In a preferred embodiment, in step (1), the concentration of PVDF-HFP / PU in the PVDF-HFP / PU transparent solution is 0.083 g / mL.

[0048] In a preferred embodiment, in step (1), the heating and stirring temperature is 80° C., and the heating and stirring time is 2 h.

[0049] In a preferred embodiment, in step (2), the stirring time is 12 hours.

[0050] In a preferred embodiment, in step (3), the temperature of the standing still is room temperature and the standing still time is 1 hour. In the present invention, bubbles in the mixed solution are removed by standing still.

[0051] In a preferred embodiment, in step (3), the drying temperature is 80° C. and the drying time is 2 h.

[0052] The present invention also provides the use of the IL@PVDF-HFP / PU flexible ion gel electrode described in the above technical solution in monitoring electromyographic signals.

[0053] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0054] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0055] Example 1

[0056] A method for preparing an IL@PVDF-HFP / PU flexible ion gel electrode, the specific steps are as follows:

[0057] (1) mixing polyvinylidene fluoride-hexafluoropropylene and polyurethane with N,N-dimethylacetamide, and then heating and stirring at 80° C. for 2 h to obtain a PVDF-HFP / PU transparent solution with a PVDF-HFP / PU concentration of 0.083 g / mL; wherein the mass ratio of polyvinylidene fluoride-hexafluoropropylene to polyurethane is 4:1;

[0058] (2) adding [EMIOTf] and [VBIM][Cl] to the PVDF-HFP / PU transparent solution obtained in step (1), stirring for 12 hours to obtain a mixed solution; wherein the mass ratio of [EMIOTf] to [VBIM][Cl] is 1:1, and the total mass proportion of [EMIOTf] and [VBIM][Cl] in the mixed solution is 30wt%;

[0059] (3) The mixed solution obtained in step (2) was poured into a glass culture dish, allowed to stand at room temperature for 1 h, and then dried in an oven at 80° C. for 2 h to obtain an IL@PVDF-HFP / PU flexible ion gel electrode.

[0060] Comparative Example 1

[0061] A method for preparing a PVDF-HFP flexible ion gel electrode, the specific steps are as follows:

[0062] (1) mixing polyvinylidene fluoride-hexafluoropropylene and N,N-dimethylacetamide, and then heating and stirring at 80° C. for 2 h to obtain a polyvinylidene fluoride-hexafluoropropylene transparent solution having a polyvinylidene fluoride-hexafluoropropylene concentration of 0.083 g / mL;

[0063] (2) The polyvinylidene fluoride-hexafluoropropylene transparent solution obtained in step (1) was poured into a glass culture dish, left to stand at room temperature for 1 hour, and then dried in an oven at 80° C. for 2 hours to obtain a PVDF-HFP flexible gel electrode.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that step (2) is omitted to obtain a PVDF-HFP / PU flexible gel electrode.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that in step (2), the mass ratio of [EMIOTf] and [VBIM][Cl] is 1:1, and the total mass proportion of [EMIOTf] and [VBIM][Cl] in the mixed solution is 10wt%, obtaining a 10% IL@PVDF-HFP / PU flexible ion gel electrode.

[0068] Comparative Example 4

[0069] The difference from Example 1 is that in step (2), the mass ratio of [EMIOTf] and [VBIM][Cl] is 1:1, and the total mass proportion of [EMIOTf] and [VBIM][Cl] in the mixed solution is 15wt%, obtaining a 15% IL@PVDF-HFP / PU flexible ion gel electrode.

[0070] Comparative Example 5

[0071] The difference from Example 1 is that in step (2), the mass ratio of [EMIOTf] and [VBIM][Cl] is 1:1, and the total mass proportion of [EMIOTf] and [VBIM][Cl] in the mixed solution is 20wt%, obtaining a 20% IL@PVDF-HFP / PU flexible ion gel electrode.

[0072] Comparative Example 6

[0073] The difference from Example 1 is that in step (1), polyvinylidene fluoride-hexafluoropropylene is mixed with N,N-dimethylacetamide to obtain a 30% IL@PVDF-HFP flexible ion gel electrode.

[0074] Figure 1 Schematic diagram of the conductive mechanism of the flexible ion gel electrode prepared in Example 1; wherein A is a schematic diagram of the CAOMSOL conductive potential of the flexible ion gel electrode, and B is a schematic diagram of the ion conductive mechanism. Figure 1 It can be seen that complex but balanced intermolecular interactions can stably and weakly trap ionic species while enabling them to have high mobility in the electric field.

[0075] Figure 2 The surface scanning electron micrographs of the flexible ion gel electrodes prepared in Example 1 and Comparative Examples 1-2 are shown; A is Comparative Example 1 (PVDF-HFP), B is Comparative Example 2 (PVDF-HFP / PU), and C is Example 1 (IL@PVDF-HFP / PU). Figure 2 It can be seen that the doping of IL can make the flexible ion gel electrode have uniform microphase separation and amorphous structure, and this microphase separation structure shows a positive correlation with the addition of IL.

[0076] At 25±2°C, the conductivity of the flexible ion gel electrodes prepared in Example 1 and Comparative Examples 3-6 was tested. The results are shown in Figure 3 . Figure 3 The conductivity diagram of the flexible ion gel electrode prepared in Example 1 and Comparative Examples 3-6. Figure 3 It can be seen that the doping of IL increases the density of charge carriers and improves the conductivity of the flexible ion gel electrode. The conductivity shows an obvious upward trend with the increase of IL content, and presents the optimal conductivity at a mass fraction of 30%.

[0077] According to ASTM D638 "Test Method for Tensile Properties of Plastics", the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1 was tested for stretchability and bendability. The results are shown in Figure 4 . Figure 4 The stretchability and bendability diagrams of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1; the left diagram is the stretchability and the right diagram is the bendability. Figure 4 It can be seen that the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1 has high stretchability and deformability. The flexible ion gel electrode with an original length of 2 cm can be stretched to 9 cm without breaking, and can be bent at will without damage.

[0078] Human epidermal electromyographic signal monitoring: The IL@PVDF-HFP / PU flexible ion gel electrodes prepared in Example 1 and the original electrodes of the electromyographic tester were attached to the biceps of volunteers in batches, and the epidermal electromyographic signal was tested by upper arm movement. The results are shown in Figure 5 .

[0079] Figure 5 This is a monitoring diagram of the epidermal electromyographic signal of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1. Figure 5 It can be seen that the IL@PVDF-HFP / PU flexible ion gel electrode can obtain the surface electromyographic signal of the human body. Moreover, when the volunteer lifted a weight of 1 kg, the peak intensity of the surface electromyographic signal increased significantly, indicating that the electrode has good sensitivity.

[0080] Deep myoelectric signal monitoring of rats: The IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1 was wrapped around the gastrocnemius muscle of rats, and deep myoelectric signals were monitored while the rats were in motion. Figure 6 .

[0081] Figure 6 This is a deep electromyographic signal monitoring diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1, where the right figure is an enlarged view of the dotted frame part in the left figure. Figure 6 It can be seen that the IL@PVDF-HFP / PU flexible ion gel electrode covers the gastrocnemius muscle of the rat, and can obtain deep electromyographic signals during the rat's awake movement state. And at 0 days, 3 days, 5 days and 7 days after implantation, the in vivo electromyographic signals can still be monitored during conscious movement.

[0082] Electrophysiological stimulation test: The IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1 was wrapped around the sciatic nerve of the rat, and a small section was exposed to facilitate the application of external voltage. Then electrical stimulation was applied, and the muscle movement state of the rat before and after electrical stimulation was recorded. The results are shown in Figure 7 .

[0083] Figure 7 The electrophysiological stimulation diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1; the left diagram is before applying electrical stimulation, and the right diagram is after applying electrical stimulation. Figure 7 It can be seen that during the 7-day implantation period, electrical stimulation of the sciatic nerve through the IL@PVDF-HFP / PU flexible ion gel electrode can induce muscle contraction and ankle flexion.

[0084] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A IL@PVDF-HFP / PU flexible ion gel electrode, characterized in that: The invention comprises a polymer substrate and a two-component ionic liquid; the polymer substrate is polyvinylidene fluoride-hexafluoropropylene / polyurethane, and the two-component ionic liquid is 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and 1-vinyl-3-butylimidazole chloride.

2. The IL@PVDF-HFP / PU flexible ion gel electrode according to claim 1, characterized in that: The mass proportion of the two-component ionic liquid in the IL@PVDF-HFP / PU flexible ion gel electrode is 30%.

3. The IL@PVDF-HFP / PU flexible ion gel electrode according to claim 1, characterized in that: The mass ratio of polyvinylidene fluoride-hexafluoropropylene to polyurethane in the polyvinylidene fluoride-hexafluoropropylene / polyurethane is 4:

1.

4. The IL@PVDF-HFP / PU flexible ion gel electrode according to claim 1, characterized in that: The mass ratio of the 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide to 1-vinyl-3-butylimidazolium chloride is 1:

1.

5. A method for preparing the IL@PVDF-HFP / PU flexible ion gel electrode according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) mixing polyvinylidene fluoride-hexafluoropropylene and polyurethane with N,N-dimethylacetamide, and heating and stirring to obtain a PVDF-HFP / PU transparent solution; (2) adding a two-component ionic liquid to the PVDF-HFP / PU transparent solution obtained in step (1), and stirring to obtain a mixed solution; (3) Pour the mixed solution obtained in step (2) into a culture dish, let it stand and dry it to obtain the IL@PVDF-HFP / PU flexible ion gel electrode.

6. The preparation method according to claim 5, characterized in that: In step (1), the concentration of PVDF-HFP / PU in the PVDF-HFP / PU transparent solution is 0.083 g / mL.

7. The preparation method according to claim 5, characterized in that: In step (1), the heating and stirring temperature is 80° C., and the heating and stirring time is 2 h.

8. The preparation method according to claim 5, characterized in that: In step (2), the stirring time is 12 hours.

9. The preparation method according to claim 5, characterized in that: In step (3), the drying temperature is 80° C. and the drying time is 2 h.

10. Use of the IL@PVDF-HFP / PU flexible ion gel electrode according to any one of claims 1 to 4 in monitoring electromyographic signals.

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