An IL@PVDF-HFP / PU Flexible Ionic Gel Electrode and Its Preparation Method and Application

Abstract

The present invention discloses an IL@PVDF-HFP / PU flexible ion gel electrode and its preparation method and application, belonging to the technical fields of composite flexible materials and neural interface technologies. The IL@PVDF-HFP / PU flexible ion gel electrode provided by the present invention has high ionic conductivity, stretchability, flexibility, as well as excellent signal stability and sensitivity, and can be used as a neural interface for monitoring epidermal and deep muscle electrical signals. The present invention adopts a binary ionic liquid with movable anions and cations of different volumes. Under the action of the electrical signals of biological tissues, the migration and distribution of anions and cations in the binary ionic liquid change significantly, generating an ionic current to achieve sensitive signal conduction. In addition, the flexible ion gel electrode has good dynamic compliance with biological tissues and stability in a physiological environment, and can perform long-term stable signal monitoring and electrical signal input on deep muscle electrical signals to achieve bidirectional signal transmission.

Description

Technical Field

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

[0002] A neural interface is a key bridge between biological tissues and external electronic devices. Among them, a neural microelectrode is a core component for recording bioelectrical 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 realized in human applications. Due to the different charge transfer behaviors between neural electrodes and biological tissues / cells, effective and stable charge transfer is crucial for the construction of neural interfaces.

[0003] Traditional neural electrodes made of metal or carbon materials mainly rely on free electrons as mobile charges for communicating with biological tissues. Although they exhibit excellent electrical conductivity, the effective interfacial charge transfer between electrons and biological tissues is limited. This limitation stems from the fact that signal transmission in the human biological system mainly involves the transmission of ions and small molecules. When ions are used as charge carriers in biological tissues, the electrical conductivity of the tissue is significantly higher than when electrons and holes are used as charge carriers.

[0004] Ion-conductive hydrogel (ICHs) electrodes exhibit ion conductivity similar to biological tissues, enabling the exchange of material information with surrounding tissues through ion transfer. This fundamentally avoids the need for conversion between electronic signals and ion signals, thus avoiding the above problems. However, ICH electrodes have the disadvantage of rapid dehydration, which often leads to the loss of flexibility and conductivity, significantly limiting their effectiveness and reliability in practical applications. By introducing ionic liquid (IL) into the polymer network to prepare ion-conductive gel (ICG), the mechanical properties and stability of the gel can be adjusted by the interaction between IL and the polymer network, thereby overcoming the disadvantages of ICH due to its completely non-volatile and high chemical stability. However, the existing ICHs have low ion conductivity, thus restricting the development of highly reliable neural electrode interfaces.

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

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

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

[0008] The present invention provides an IL@PVDF-HFP / PU flexible ionic gel electrode, which comprises a polymer substrate and a binary ionic liquid; the polymer substrate is polyvinylidene fluoride-hexafluoropropylene / polyurethane, and the binary ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIOTf]) and 1-vinyl-3-butylimidazolium chloride ([VBIM][Cl]).

[0009] Preferably, the mass ratio of the binary ionic liquid in the IL@PVDF-HFP / PU flexible ionic 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 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide to 1-vinyl-3-butylimidazolium chloride is 1:1.

[0012] The present invention provides a preparation method of the IL@PVDF-HFP / PU flexible ionic gel electrode described in the above technical solution, which comprises the following steps:

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

[0014] (2) Add the binary ionic liquid to the PVDF-HFP / PU transparent solution obtained in step (1), and obtain a mixed solution through stirring.

[0015] (3) Pour the mixed solution obtained in step (2) into a petri dish, and obtain the IL@PVDF-HFP / PU flexible ionic gel electrode through standing and drying.

[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 temperature of the heating and stirring is 80 °C, and the time of the heating and stirring is 2 h.

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

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

[0020] The present invention also provides an application of the IL@PVDF-HFP / PU flexible ion gel electrode described in the above technical solution in monitoring myoelectric 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 the substrate, which has extended 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 up to 7 days of conscious and voluntary movement.

[0024] (3) The complex but balanced intermolecular interactions in 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 an electric field and can be transmitted with high sensitivity in an alternating current electric field.

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

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

[0027] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

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

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

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

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

[0032] Figure 5 Epidermal myoelectric signal monitoring diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1;

[0033] Figure 6 Monitoring diagram of deep electromyogram signals of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1;

[0034] Figure 7 Electrophysiological stimulation diagram of the IL@PVDF-HFP / PU flexible ion gel electrode prepared in Example 1. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

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

[0038] The IL@PVDF-HFP / PU flexible ion gel electrode provided by the present 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 electrical signals. Compared with single-component electrolytes using only [EMIOTf] or [VBIM][Cl], the binary ionic liquid has movable anions and cations of different volumes. Under the action of bio-tissue electrical signals, the migration distribution of anions and cations in the binary ionic liquid changes significantly, generating ionic current and realizing sensitive signal conduction. In addition, the flexible ion gel electrode has good dynamic compliance with biological tissues and stability in the physiological environment, can perform long-term stable signal monitoring and electrical signal input on deep electromyogram signals, realize bidirectional signal transmission, and provides a new platform for developing ion neural electrodes suitable for long-term stable implantation.

[0039] In a preferred embodiment, the mass ratio of the binary ionic liquid in the IL@PVDF-HFP / PU flexible ion gel electrode is 30%. The doping of the binary ionic liquid (IL) in the present invention can endow the flexible ion gel electrode with a uniform microphase separation and an 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, improves the conductivity of the flexible ion gel electrode, and the conductivity shows an obvious upward trend with the increase of the IL content, and the optimal conductivity is presented 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 utilizes the electrochemical stability and good film-forming performance of polyvinylidene fluoride-hexafluoropropylene to endow the flexible ion gel electrode with excellent electrochemical stability and mechanical strength, and utilizes the flexible performance of polyurethane to endow the flexible ion gel electrode with a stretchable effect.

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

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

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

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

[0045] (3) Pour the mixed solution obtained in step (2) into a petri dish, and obtain the IL@PVDF-HFP / PU flexible ion gel electrode through standing and drying.

[0046] The present invention prepares the IL@PVDF-HFP / PU flexible ion gel electrode by a casting method, with simple operation and low cost of required raw materials.

[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 temperature of the heating and stirring is 80 °C, and the time of the heating and stirring is 2 h.

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

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

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

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

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

[0054] Unless otherwise specified, the raw materials in the embodiments of the present invention are all obtained through commercial channels.

[0055] Example 1

[0056] A preparation method of an IL@PVDF-HFP / PU flexible ion gel electrode comprises the following specific steps:

[0057] (1) Mix polyvinylidene fluoride-hexafluoropropylene and polyurethane with N,N-dimethylacetamide, and then heat and stir 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) Add [EMIOTf] and [VBIM][Cl] to the PVDF-HFP / PU transparent solution obtained in step (1), and stir for 12 h to obtain a mixed solution; wherein, the mass ratio of [EMIOTf] to [VBIM][Cl] is 1:1, and the total mass percentage of [EMIOTf] and [VBIM][Cl] in the mixed solution is 30 wt%;

[0059] (3) Pour the mixed solution obtained in step (2) into a glass petri dish, stand at room temperature for 1 h, and then dry 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 preparation method of a PVDF-HFP flexible ionic gel electrode is as follows:

[0062] (1) Mix polyvinylidene fluoride-hexafluoropropylene with N,N-dimethylacetamide, and then heat and stir at 80 °C for 2 h to obtain a transparent solution of polyvinylidene fluoride-hexafluoropropylene with a concentration of 0.083 g / mL;

[0063] (2) Pour the transparent solution of polyvinylidene fluoride-hexafluoropropylene obtained in step (1) into a glass petri dish, let it stand at room temperature for 1 h, and then dry it in an oven at 80 °C for 2 h 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] to [VBIM][Cl] is 1:1, and the total mass ratio of [EMIOTf] and [VBIM][Cl] in the mixed solution is 10 wt% to obtain a 10% IL@PVDF-HFP / PU flexible ionic gel electrode.

[0068] Comparative Example 4

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

[0070] Comparative Example 5

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

[0072] Comparative Example 6

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

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

[0075] Figure 2 Scanning electron microscope images of the surfaces of the flexible ionic gel electrodes prepared in Example 1 and Comparative Examples 1 - 2; among them, A is Comparative Example 1 (PVDF - HFP), B is Comparative Example 2 (PVDF - HFP / PU), and C is Example 1 (IL@PVDF - HFP / PU). It can be known that Figure 2 the doping of IL can endow the flexible ionic gel electrode with a 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 conductivities of the flexible ionic gel electrodes prepared in Example 1 and Comparative Examples 3 - 6 are tested, and the results are shown in Figure 3 . Figure 3 Conductivity diagrams of the flexible ionic gel electrodes prepared in Example 1 and Comparative Examples 3 - 6. It can be known that Figure 3 the doping of IL increases the density of charge carriers, improves the conductivity of the flexible ionic gel electrode, and the conductivity shows an obvious upward trend with the increase of IL content, presenting the optimal conductivity at a mass fraction of 30%.

[0077] According to ASTM D638 "Test Method for Tensile Properties of Plastics", the stretchability and bendability of the IL@PVDF - HFP / PU flexible ionic gel electrode prepared in Example 1 are tested, and the results are shown in Figure 4 . Figure 4 Stretchability and bendability diagrams of the IL@PVDF - HFP / PU flexible ionic gel electrode prepared in Example 1; among them, the left figure is the stretchability and the right figure is the bendability. It can be known that Figure 4 the IL@PVDF - HFP / PU flexible ionic gel electrode prepared in Example 1 has high stretchability and deformability. The flexible ionic gel electrode with an original length of 2 cm can be stretched to 9 cm without breaking, and can be bent arbitrarily 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, wherein 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 the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A IL@PVDF-HFP / PU flexible ion gel electrode, characterized in that: It includes 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; the mass ratio of the two-component ionic liquid in the IL@PVDF-HFP / PU flexible ion gel electrode is 30%; the mass ratio of polyvinylidene fluoride-hexafluoropropylene and polyurethane in the polyvinylidene fluoride-hexafluoropropylene / polyurethane is 4:1; the mass ratio of 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and 1-vinyl-3-butylimidazole chloride is 1:

1.

2. A method for preparing the IL@PVDF-HFP / PU flexible ion gel electrode according to claim 1, 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.

3. The preparation method according to claim 2, characterized in that: In step (1), the concentration of PVDF-HFP / PU in the PVDF-HFP / PU transparent solution is 0.083 g / mL.

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

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

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

7. Use of the IL@PVDF-HFP / PU flexible ion gel electrode according to claim 1 in monitoring electromyographic signals.

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