Ion driver containing ion channel interface and method of making same

Abstract

The application discloses an ion driver containing an ion channel interface and a preparation method thereof. The ion driver comprises an electrolyte layer, an electrode layer and an ion channel interface, the ion channel interface is arranged between the electrolyte layer and the electrode layer, and the ion channel interface is prepared by self-assembly of a compound with a ring structure and a polymer chain. The preparation method of the ion driver comprises the following steps: firstly, assembling the ion channel interface material to the electrode film by using a flow casting method; secondly, preparing an electrolyte film; and thirdly, assembling the electrolyte film and the electrode film by using a hot pressing method, so as to obtain the ion driver. By adding the interface material with a slip ring effect to the surface layer of the electrode, the energy barrier of ion transportation is reduced, so that the ion driver has higher energy conversion efficiency and power density.

Description

Technical Field

[0001] This invention relates to an ion actuator and its preparation method, and more particularly to an ion actuator containing an ion channel interface and its preparation method. Background Technology

[0002] In recent years, soft actuation materials, as intelligent materials capable of responding to external stimuli, have shown broad application prospects in soft robotics, wearable devices, and healthcare. Among them, flexible ion actuators, a type of ion-electroactive polymer (iEAP) actuator, have promising applications in flexible robots, wearable tactile feedback devices, and flexible intelligent devices due to their advantages such as light weight, scalability, low power consumption, fast response, and large deformation. However, at present, the actuation performance of flexible ion actuators is limited by ion transport at the electrode interface, resulting in poor actuation performance and making it difficult to meet the application needs of flexible ion actuators in more fields.

[0003] Currently, the intermediate layers of ion actuators mainly include perfluorosulfonic acid ionomers, polymer-inorganic hybrid materials, ionic hydrogels, and ionogel materials. Ionogels are polymer networks that expand with electrolyte solutions or ionic liquids. They are conductive solids with high stretchability and transparency. They possess ionic conductivity and electronic insulation, allowing the formation of an electrical double layer (EDL) at the interface between the electrode and the ionogel. Relatively speaking, ion actuators using ionogels can exhibit greater displacement during bending motion, faster switching response, lower operating voltage, and lower manufacturing costs.

[0004] Electrodes include traditional noble metal electrodes (palladium, platinum, silver, gold) and carbon-based nanomaterial electrodes. Traditional noble metal electrodes are deposited on both sides of polymer films through methods such as chemical plating, electroplating, and sputtering. Their advantages include excellent conductivity, which can reduce surface resistance and achieve better actuation performance. However, these metal electrodes are expensive to produce and prone to cracking under multiple cycles, reducing actuation performance. Carbon-based nanomaterials are an emerging electrode material. Compared with other electrode materials, carbon-based nanomaterial electrodes have the advantages of abundant and stable carbon elements and low cost. Furthermore, carbon-based nanomaterial electrodes are created using various environmentally friendly and mature synthetic techniques, and good actuation performance can often be obtained using simple methods such as casting or hot pressing when fabricating ion actuators.

[0005] Electrical conductivity and reversible ion intercalation are crucial factors influencing the driving performance of ion actuators. They affect the actuator's characteristics, including response time, tip displacement, and bending strain, by influencing the rate at which charged ions exchange from the electrolyte to the electrode. The main driving mechanism of ion actuators is based on the reversible intercalation of ions into the electrode layer. Ions need to overcome an interfacial energy barrier during intercalation, which is manifested in ionic conductivity. The higher the energy barrier, the lower the ionic conductivity, and the more difficult the reversible intercalation of ions into the electrode. A lower interfacial energy barrier favors the ion diffusion rate, thereby improving the actuator's response speed. Graphene is a two-dimensional (2D) nanostructure sp... 2 Carbon materials, due to their unique structure and fascinating electronic and mechanical properties, are widely studied carbon-based nanomaterial electrodes. Theoretical calculations predict that the quantum mechanical strain in the basal plane of graphene can reach 0.2%, and the electrostatic bilayer strain during charge injection can reach 1%, far exceeding that of carbon nanotubes (CNTs). However, the initial graphene-based bicrystalline ion actuators suffered from high interfacial ion energy barriers and low ion conductivity, making it difficult for ions to migrate to the interlayer spacing parallel to the graphene nanosheets, resulting in a very slow actuation speed. Furthermore, the re-stabilization of graphene electrodes during bulk electrode fabrication also increases the energy barrier, causing slow and difficult ion insertion. In fact, many other materials (such as g-C3N4, MoS2, etc.) require solutions to the interfacial energy barrier problem for applications in the actuator field. Currently, many studies are dedicated to improving the performance of ion actuators by increasing conductivity and forming stable ion channels in the electrode layer.

[0006] Current typical ion actuators consist of a layer of electrolyte and a layer of symmetrical electrodes, and rely on reversible ion migration between the electrolyte and electrodes to generate actuation deformation. These solid-state actuators suffer from low internal ion transport efficiency and lack effective modulation of the actuator interface. A similar technical approach is illustrated by patent publication number CN117228794A, which describes a flexible ion actuator based on an MXene / Ni-PBAs composite material. The composite electrode material is prepared by adding nickel nitrate, sodium citrate, and MXene dropwise with a potassium ferricyanide solution under stirring. After addition, the material is sealed and aged, and the precipitate is separated. The polyelectrolyte material is prepared by adding an ionic liquid and a Nafion membrane solution to an organic solvent, heating and stirring, then vacuum drying in a mold, followed by heat treatment. The device is assembled using a hot-pressing method. This method improves ion transport rate and achieves better actuation performance by perforating the electrolyte layer.

[0007] Ion transport largely determines the actuation performance of ion actuators. The above discussion has explained the impact of device conductivity and ion exchange capacity on actuator performance; further research indicates that actuator performance is primarily determined by electrochemical and electromechanical dynamics within the electrodes. In actuator systems, ion diffusion is the rate-limiting step in actuation performance. A voltage drop exists at the actuator electrode interface, and ions must overcome an interfacial energy barrier during reversible intercalation / delamination, resulting in low ionic conductivity. Previous research has mainly focused on optimizing electrode and electrolyte materials, without substantially addressing the high energy barrier caused by differences in actuator interfacial materials, i.e., low ionic conductivity. This leads to low energy conversion efficiency and insufficient power density in ion actuators, limiting their actuation performance and reaction rate. Summary of the Invention

[0008] Objective of the Invention: This invention aims to provide an ion actuator containing an ion channel interface, which utilizes an interface material with a slip ring driving effect to reduce the energy barrier of ion transport during the ion actuator's operation and improve ion conductivity; this invention also aims to provide a method for preparing the aforementioned ion actuator containing an ion channel interface.

[0009] Technical solution: The ion actuator containing an ion channel interface of the present invention includes an electrolyte layer and an electrode layer. The ion actuator further includes an ion channel interface disposed between the electrolyte layer and the electrode layer. The ion channel interface is prepared by self-assembly of a compound with a cyclic structure and a polymer chain.

[0010] Furthermore, the method for preparing the ion channel interface includes the following steps:

[0011] A compound with a cyclic structure is reacted with a polymer or polymer monomer to attach the cyclic compound to a polymer chain segment; the cyclic compound is selected from at least one of α-cyclodextrin, hydroxypropylated α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin or 18-crown ether-6, and the polymer chain is at least one of polyvinyl alcohol, polypropylene glycol or polyaniline.

[0012] Furthermore, the mass ratio of the compound with the cyclic structure to the polymer or polymer monomer is 5 to 10:1.

[0013] Furthermore, the reaction temperature for the self-assembly is 0-50℃.

[0014] Furthermore, after self-assembly, the ends of the polymer chains are capped.

[0015] The method for preparing the ion actuator containing the ion channel interface includes the following steps:

[0016] First, the ion channel interface material is assembled onto the electrode membrane using a casting method, then an electrolyte membrane is prepared, and finally the electrolyte membrane and the electrode membrane are assembled using a hot pressing method to obtain the ion actuator.

[0017] Furthermore, the preparation method of the electrode membrane includes: ultrasonically dispersing graphene and polyvinylidene fluoride, then vacuum filtering the dispersion onto a microfiltration membrane, and drying it to obtain a graphene electrode membrane.

[0018] Furthermore, the electrolyte is a thermoplastic polyurethane (TPU) electrolyte.

[0019] Furthermore, the heating temperature during the hot-press assembly of the ion actuator is 50-90℃, and the pressure loading time is 3-5h.

[0020] Furthermore, the synthesis process of the interface material using polyvinyl alcohol (PEG) as the polymer segment includes: mixing a cyclic compound, aminated PEG, and phosphate buffer at room temperature with stirring, and then self-assembling at low temperature. Next, a PBS solution of 3-hydroxy-1-adamantaneacetic acid and 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methylacylchloramine (DMTMM) is added dropwise to the precursor solution to complete the end-capping reaction with the polymer chain. After removing residual cyclic molecules and PEG polymer, the mixture is freeze-dried to obtain the interface material using polyvinyl alcohol as the polymer segment.

[0021] Furthermore, the synthesis process of the interface material with polypropylene glycol (PPG) as the polymer segment includes: adding tetraamino-modified PPG to an aqueous solution of a cyclic compound, and completing self-assembly under heating conditions. Then, adding an aqueous solution of 2,4,6-trinitrobenzenesulfonic acid (TNBS) and NaHCO3 to the mixed solution, stirring under dark conditions, dialyzing, and freeze-drying to obtain the interface material with polypropylene glycol as the polymer segment.

[0022] Furthermore, the synthesis process of the interface material with polyaniline as the polymer segment includes: mixing aniline, a cyclic compound and water, adding concentrated hydrochloric acid and ammonium persulfate and continuing to stir, filtering, collecting the precipitate, washing and freeze-drying to obtain the interface material with polyaniline as the segment.

[0023] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: By utilizing an interface material with a slip-ring effect added to the electrode surface, the energy barrier for ion transport is reduced, thereby enabling the ion actuator to achieve higher energy conversion efficiency and power density. The ion channel interface material contains a ring-shaped structure with cavities that slides on the polymer chain, moving freely with the deformation of the polymer chain under applied strain to control the opening and closing of the ion channel, thus reducing the energy barrier for ion transport during the ion actuator's operation and amplifying the driving effect. The actuator described in this invention achieves sensitive control of bending strain on the interface ion transport mechanism, allowing the ion conductivity to be adjusted by controlling the bending strain. By applying positive and negative bending degrees, the expansion and contraction state of the interface can be easily controlled. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the driving mechanism;

[0025] Figure 2 This is a schematic diagram of the structure of an ion-type actuator and a surface morphology diagram of the ion channel interface.

[0026] Figure 3 This is a graph showing the change in ionic conductivity as a function of the degree of tortuosity at the ion channel interface.

[0027] Figure 4 This is a schematic diagram illustrating the working mechanism of the ion channel interface;

[0028] Figure 5 Chemical structure diagram of α-cyclodextrin threaded onto polymer chain and 1H NMR spectrum of PEG-based interface material;

[0029] Figure 6 This diagram shows the interface of ion channels in an electrochemical cell at different degrees of curvature, used for evaluating ion conductivity.

[0030] Figure 7 (a) shows the electro-induced strain of the actuator under a driving voltage of 1.0V, and (b) shows the relationship between the driving voltage and the strain displacement. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0032] Example 1

[0033] (1) Preparation of polyvinyl alcohol-based interface materials with slip ring effect

[0034] 2g of α-cyclodextrin and 0.4g of PEG-NH2 (M W=4000) was dissolved in 15 mL of phosphate buffer (PBS, 0.1 M, pH = 8), stirred at room temperature, and then the solution was cooled to 3-5 °C and stored for 48 hours to obtain the precursor solution. 30 mg of 3-hydroxy-1-adamantaneacetic acid (OH-Ada-COOH) and 33 mg of 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methylacylchloramine (DMTMM) were added to 3 mL of PBS solution and stirred continuously at room temperature. The solution was added dropwise to the precursor solution, and the reaction was carried out at room temperature for 24 hours to complete the end-capping reaction. Then, 35 mg of DMTMM was added to complete the reaction at room temperature for another 24 hours. The reactants were dispersed in 50 mL of dimethyl sulfoxide (DMSO), and then precipitated in 100 mL of deionized water to remove residual cyclic molecules and PEG polymers. Finally, the mixture was freeze-dried to obtain the interface material with a slip ring structure. Figure 5 A schematic diagram and 1H NMR spectrum of a PEG-based interface material prepared using α-cyclodextrin.

[0035] (2) Preparation of graphene electrodes containing interface materials

[0036] First, 0.1 g of graphene and 0.01 g of polyvinylidene fluoride (PVDF) were dispersed in 20 mL of dimethylformamide (DMF) under ultrasonication. The dispersion was then vacuum filtered onto a microfiltration membrane and dried at 80 °C for 12 h to obtain a graphene electrode membrane. The interface layer with slip ring effect prepared in step (1) was then dispersed at a height of 200 μm and a depth of 0.5 cm s. -1 At a high speed, it is assembled onto the electrode film using a casting method. Finally, after complete drying, the electrode film is obtained.

[0037] (3) Preparation of thermoplastic polyurethane electrolyte and assembly of actuator

[0038] First, 0.5g of TPU was dissolved in 20ml of LDM and stirred at 60℃ for 10h. Then, 1g of ionic liquid [EMIM][BF4] was added dropwise to the above solution, and stirring was continued for 5h. The solution was then poured into a Teflon mold under heating at 85℃. After drying, the freestanding electrolyte membrane was peeled off the mold. The electrolyte membrane and electrode membrane were then assembled into an ion actuator using a hot-pressing method. The assembly conditions were a heating temperature of 80℃ and a pressure loading time of 5h. A schematic diagram of the structure of the ion actuator prepared in this embodiment and the surface morphology of the ion channel interface are shown in [reference needed]. Figure 2 .

[0039] Example 2

[0040] (1) Preparation of polypropylene glycol-based interface materials with slip ring effect.

[0041] 0.6 g of α-cyclodextrin was dissolved in 5 mL of deionized water, followed by the addition of 60 mg of tetraamino-modified PPG (M). W =4000), sonicated for 15 min, then heated and stirred at 50℃ for 2 h. Then, TNBS solution (1M, 150 μL) and 44 mg NaCO3 were added to the solution and stirred in the dark for 3 h. The sample was dialyzed in deionized water to remove excess sample (MMCO: 8000), with the water changed every 2 h. After freeze-drying, an interface material with polypropylene glycol as the chain segment was obtained.

[0042] Steps (2) and (3) are the same as in Example 1.

[0043] Example 3

[0044] (1) Preparation of polyaniline-based interface materials with slip ring effect.

[0045] 93 mg of freshly distilled aniline was added to 50 mL of an aqueous solution of α-cyclodextrin (1 mmol of α-cyclodextrin in the aqueous solution), and the mixture was stirred at 0 °C for 4 hours to obtain a clear solution. Then, 5 mL of concentrated hydrochloric acid and 228 mg of ammonium persulfate were added sequentially, and the mixture was stirred at 0 °C for 12 hours. The precipitate was collected by filtration, washed with ice water and ethanol, and then freeze-dried.

[0046] Steps (2) and (3) are the same as in Example 1.

[0047] Figure 1 This is a schematic diagram of the driving mechanism of the ion actuator described in this invention. When an electric field is applied to the actuator, the electrostatic double-layer effect causes ion diffusion and intercalation, resulting in volume expansion of the cathode and anode. Figure 1 As shown, positive and anions in the interlayer electrolyte diffuse into the electrode layer under the influence of an electric field. After reversible intercalation / delamination of the electrode layer, its volume changes. Due to the size difference between cations and anions (usually cations are larger), the actuator bends towards the positive electrode side.

[0048] The test results of the ion driver prepared in Example 1 are as follows: Figure 3 As shown, when the sample bends to a negative degree (with an opposite voltage applied), the interface contracts, and the ring structure aggregates across the polymer chain. This aggregated ring structure blocks ion channels, leading to a decrease in ionic conductivity at the interface. Conversely, when the strip bends to a positive degree, the ring structure slides off the chain, opening the blocked ion channels and achieving faster ion conductivity at the material interface. This verifies that the interfacial slip ring effect is beneficial for improving the energy conversion efficiency of the ion actuator, and the actuation mechanism of the ion actuator is based on the expansion and contraction of the symmetrical electrodes.

[0049] like Figure 4As shown, conventional actuators generate contraction or expansion strain under voltage, while the focus of this invention is to reduce the energy barrier (manifested as conductivity) of ion transport during the ion actuator's operation by adding an interface material with a slip ring driving effect between the electrode and the electrolyte. Figure 3 This enhances the strain effect of the actuator. Under no strain conditions, the ion channel is a normal channel; it closes during contraction and opens during expansion. Fewer ions are present on the contraction side and more on the expansion side, thus amplifying the strain effect of the actuator.

[0050] Strain-modulated ion transport at the ion channel interface amplifies the driving effect of unbalanced ion insertion. In short, the expanding side of the actuator allows more ions to enter due to the open ion channels, while the contracting side prevents ion entry due to the closed ion channels. Strain-modulated ion transport caused by the interfacial sliding ring effect significantly improves the driving performance. Figure 6 and Figure 7 As shown in (a), this driver provides a large drive displacement of 16.7 mm at a low drive voltage of 1V. The drive voltage is maintained within a wide range of 1V to 0.1V, therefore, in addition to the drive frequency, the drive voltage can also be used to control the drive displacement. Figure 7 (b)

Claims

1. An ion actuator containing an ion channel interface, comprising an electrolyte layer and an electrode layer, characterized in that, The ion actuator further includes an ion channel interface disposed between the electrolyte layer and the electrode layer. The ion channel interface is prepared by self-assembly of a compound with a cyclic structure and a polymer chain. The preparation includes the following steps: reacting the compound with a polymer or polymer monomer to attach the compound with the cyclic structure onto the polymer chain segment; the compound with the cyclic structure is selected from at least one of α-cyclodextrin, hydroxypropylated α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, or 18-crown ether-6, and the polymer chain is at least one of polyvinyl alcohol, polypropylene glycol, or polyaniline.

2. The ion actuator containing an ion channel interface according to claim 1, characterized in that, The mass ratio of the compound with the cyclic structure to the polymer or polymer monomer is 5-10:

1.

3. The ion actuator containing an ion channel interface according to claim 1, characterized in that, The reaction temperature for the self-assembly is 0-50℃.

4. The ion actuator containing an ion channel interface according to claim 1, characterized in that, After self-assembly, the ends of the polymer chain are capped.

5. A method for preparing an ion actuator containing an ion channel interface as described in any one of claims 1-4, characterized in that, Includes the following steps: First, the ion channel interface material is assembled onto the electrode membrane using a casting method, then an electrolyte membrane is prepared, and finally the electrolyte membrane and the electrode membrane are assembled using a hot pressing method to obtain the ion actuator.

6. The method for preparing an ion actuator containing an ion channel interface according to claim 5, characterized in that, The method for preparing the electrode membrane includes: ultrasonically dispersing graphene and polyvinylidene fluoride, then vacuum filtering the dispersion onto a microfiltration membrane, and drying it to obtain a graphene electrode membrane.

7. The method for preparing an ion actuator containing an ion channel interface according to claim 5, characterized in that, The electrolyte is a thermoplastic polyurethane electrolyte.

8. The method for preparing an ion actuator containing an ion channel interface according to claim 5, characterized in that, The heating temperature for assembling the ion actuator using the hot pressing method is 50-90℃, and the pressure loading time is 3-5h.

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