Ionic actuators with ternary electrodes

Abstract

An actuator system includes an ionic actuator having a pair of electrodes and an electrolyte. The ionic actuator is deformable in response to a voltage applied across the pair of electrodes. The electrolyte is a flexible film laterally disposed between the pair of electrodes. The electrolyte includes Nafion and an ionic liquid. Each of the pair of electrodes is formed of a ternary electrode system including the ionic liquid; single-walled carbon nanotubes (SWCNTs); and DMSO-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), in which the SWCNTs and the PEDOT:PSS are respectively a core and a shell of a core-shell structure.

Description

IONIC ACTUATORS WITH TERNARY ELECTRODESRELATED APPLICATION

[0001] This application claims the benefit of priority to the Singapore patent application no. 10202403082R filed October 3, 2024, the contents of which are incorporated herein by reference in entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to ionic actuators and more particularly to ionic actuators with ternary electrodes.BACKGROUND

[0003] Ionic actuators operate by converting electrical energy into mechanical motion through ion migration within an electrolyte. The ionic actuator can offer advantages of being lightweight, flexible, and generally free of mechanical creep. However, the flexibility of the conventional ionic actuator also means that it inherently suffers from a relatively low blocking force that renders the conventional ionic actuator incapable of providing the required strength to perform many tasks such as gripping, lifting, holding, and stable releasing.SUMMARY

[0004] The present application discloses various embodiments of an actuator system having one or more ionic actuators. The ionic actuator of the present disclosure includes an electrolyte and a pair of electrodes, with each of the pair of electrodes being of a ternary electrode system. The electrolyte is a flexible film laterally disposed between the pair of electrodes. The ionic actuator is deformable in response to a voltage applied across the pair of electrodes. The electrolyte may include Nafion and an ionic liquid. The ternary electrode system may include the ionic liquid. The ternary electrode system may include single-walled carbon nanotubes (SWCNTs). The ternary electrode system may include DMSO-treated poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOTPSS). The ternary electrode system may be configured with the SWCNTs and the PEDOT:PSS being respectively a core and a shell of a core-shell structure.

[0005] The actuator system may include a plurality of the ionic actuators in which a first ionic actuator of the plurality of ionic actuators and a second ionic actuator of the plurality ofionic actuators are coupled to one another longitudinally in a series to form a multi -segment actuator.

[0006] According to various embodiments, the actuator system may further include a controller, in which the controller is configured to simultaneously apply a first voltage signal to the first ionic actuator and a second voltage signal to the second ionic actuator. The actuator system may be configured to enable the following: in response to the first voltage signal having a same polarity as the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in a same direction, and in response to the first voltage signal having an opposite polarity to the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in opposing directions.

[0007] According to various embodiments, the actuator system may be configured to enable the following: in response to the first voltage signal and the second voltage signal having a positive polarity, the first ionic actuator and the second ionic actuator may be configured to deform in a first direction, and in response to the first voltage signal and the second voltage signal having a negative polarity, the first ionic actuator and the second ionic actuator may be configured to deform in a second direction opposite to the first direction.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various embodiments of the present disclosure are described below with reference to the following drawings:

[0009] FIG. 1 illustrates the fabrication and structure of a ternary electrode system in accordance with embodiments of the disclosure;

[0010] FIG. 2 and FIG. 3 illustrate the characterization of the performance of the ternary electrode system in accordance with embodiments of the disclosure;

[0011] FIG. 4 illustrates energy dispersive spectroscopy of Opt-SWCNTs / PEDOT: PSS / IL electrode in accordance with embodiments of the disclosure;

[0012] FIG. 5 shows TEM images of SWCNTs mixed solely with PEDOT: PSS in accordance with embodiments of the disclosure;

[0013] FIG. 6 illustrates an analysis of ion migration performance in the electrode in accordance with embodiments of the disclosure;

[0014] FIG. 7 illustrates impedance variation of different electrodes in the three-electrode systems in accordance with embodiments of the disclosure;

[0015] FIG. 8 illustrates a method for fabricating a flexible ionic actuator in accordance with embodiments of the disclosure;

[0016] FIG. 9 illustrates XPS N Is spectra of ternary electrode under different voltages in accordance with embodiments of the disclosure;

[0017] FIG. 10 and Fig 11 illustrate the ionic actuator performance of the ternary electrode system in accordance with embodiments of the disclosure;

[0018] FIG. 12 illustrates the performance variation of composite electrodes and actuators as a function of varying ratios of single-walled carbon nanotubes (SWCNTs), PEDOT:PSS, and ionic liquid in accordance with embodiments of the disclosure;

[0019] FIG. 13 and FIG. 14 illustrate an analysis of device structure optimization in accordance with embodiments of the disclosure;

[0020] FIG. 15 illustrates the simulated results of ion migration within the electrode and the corresponding actuator bending behavior in accordance with embodiments of the disclosure;

[0021] FIG. 16 illustrates the performance enhancement achieved by incorporating DMSO into the electrode material in accordance with embodiments of the disclosure;

[0022] FIG. 17 illustrates the performance variation resulting from different contents of Triton X-100 used to disperse SWCNTs in accordance with embodiments of the disclosure;

[0023] FIG. 18 illustrates the structural evolution of Nafion doped with ionic liquid and subjected to annealing in accordance with embodiments of the disclosure;

[0024] FIG. 19 illustrates the influence of DMAC content on the performance of Nafion films in accordance with embodiments of the disclosure;

[0025] FIG. 20 illustrates the performance exploration of Nafion / ionic liquid (IL) membranes with different ionic liquid concentrations and annealing processes in accordance with embodiments of the disclosure;

[0026] FIG. 21 illustrates the tensile properties of Nafion / ionic liquid (IL) membranes in accordance with embodiments of the disclosure;

[0027] FIG. 22 illustrates the structural analysis of Nafion / ionic liquid (IL) membranes via small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and two- dimensional (2D) SAXS diffraction in accordance with embodiments of the disclosure;

[0028] FIG. 23 illustrates the Fourier-transform infrared (FTIR) spectra of Nafion / ionic liquid (IL) membranes under annealing process and different concentrations in accordance with embodiments of the disclosure;

[0029] FIG. 24 illustrates the influence of electrolyte thickness and electrode thickness on the performance of the electrochemical actuator in accordance with embodiments of the disclosure,

[0030] FIG. 25 illustrates the electrochemical and mechanical performance of the actuator as a function of ionic liquid concentration in accordance with embodiments of the disclosure;

[0031] FIG. 26 illustrates the effect of electrode thickness on device performance in accordance with embodiments of the disclosure;

[0032] FIG. 27 illustrates the effect of electrolyte thickness on actuator performance in accordance with embodiments of the disclosure;

[0033] FIG. 28 illustrates the blocking force variation of the device under different voltages in accordance with embodiments of the disclosure;

[0034] FIG. 29 is a schematic diagram of an actuator system in accordance with embodiments of the present disclosure;

[0035] FIG. 30 is a schematic diagram of an actuator system having a multi-segment ionic actuator in accordance with embodiments of the disclosure;

[0036] FIG. 31 illustrates the actuator system of FIG. 30 in which opposing electrical polarities are applied to the electrodes on the same side of adjacent segments in accordance with embodiments of the disclosure;

[0037] FIG. 32 illustrates an embodiment of the present disclosure in which the ionic actuators are mounted on a base;

[0038] FIG. 33 illustrates an embodiment of the present disclosure in which two or more ionic actuators in the multi-segment system are mounted on a base;

[0039] FIG. 34 illustrates an embodiment of the present disclosure in which four ionic actuators are radially arranged on a circular base;

[0040] FIG. 35 illustrates an embodiment of the present disclosure in which four pairs of ionic actuators are radially arranged on a circular base;

[0041] FIG. 36 illustrates an embodiment of the present disclosure in which four ionic actuators are arranged along a linear base;

[0042] FIG. 37 illustrates an embodiment of the present disclosure in which four pairs of ionic actuators are arranged along a linear base; and

[0043] FIG. 38 and FIG. 39 illustrate various applications of the multi-segment ionic actuator in accordance with embodiments of the disclosure.DETAILED DESCRIPTION

[0044] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes of illustration and to aid understanding, and not to be limiting. Features that are described in thecontext of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments, even if not explicitly described in these other embodiments. Additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0045] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0046] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0047] As used herein, the singular ‘a’ and ‘an’ may be construed as including the plural “one or more” unless apparent from the context to be otherwise.

[0048] The terms "about" and "approximately" as applied to a stated numeric value encompasses the exact value and a reasonable variance as will be understood by one of ordinary skill in the art, and the terms “generally” and “substantially” are to be understood in a comparable manner, unless otherwise specified.

[0049] Some processes may be described in terms of steps merely to aid understanding and / or for convenient reference. The delineation between one step and another step may be described as such merely for convenient reference in the present disclosure. It will be understood that in actual implementation there may not be a clear division or transition from one step to another subsequent step. There may be a certain amount of overlap among the steps and / or more than one step may occur or be performed concurrently in time, etc.

[0050] As used herein, the term “concurrent”, or “concurrently”, is used loosely to refer to two or more occurrences (or events) that at least partially overlap in time. The occurrences may or may not start at the same time instant and / or end at the same time instant

[0051] Terms such as “first” and “second” are used in the description and claims only for the sake of brevity and clarity, and do not necessarily imply a priority or order, unless required by the context.

[0052] The term "blocking force" (or "blocked force") is used in the present disclosure in a which would be understood by the person skilled in the art to refer to a maximum force that can be applied by an actuator when generating zero displacement or, as the case may be, the force required to return an actuator from a state of maximum displacement to a default state of zero displacement.

[0053] The present disclosure describes a ternary electrode system that includes three components: Single-Walled Carbon Nanotubes (SWCNTs), poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and an ionic liquid (IL).

[0054] SWCNTs serve as the primary conductive filler, providing high electrical conductivity, mechanical strength, and flexibility. SWCNTs are dispersed in an aqueous medium using a surfactant to prevent aggregation and facilitate uniform or substantially uniform distribution in the aqueous medium.

[0055] PEDOT:PSS is a conductive polymer employed not only as a dispersing agent for SWCNTs but also as a matrix -forming component that enhances the film's mechanical integrity and flexibility. The PEDOT:PSS component contributes to the overall conductivity and facilitates the formation of a free-standing, flexible film.

[0056] The IL is incorporated to improve ion transport within the electrode and enhance the electrochemical stability of the system. The IL may also contribute to the mechanical flexibility of the final film by acting as a plasticizing agent.

[0057] The fabrication process of the ternary electrode system involves the following steps:(1) Dispersion of SWCNTs: SWCNTs are dispersed in a solvent, such as deionized water, using a probe sonicator. Specifically, this step involves dissolving 10 milligrams (mg) of SWCNTs and 50 mg of Triton X-100 in 100 milliliters (ml) of deionized water and subsequently use a probe sonicator to initially disperse the SWCNTs in an ice water bath. The probe sonicator may be operated at 600 Watts (W) for 15 minutes (e.g., alternating between being switched on for 2 seconds and switched off for 1 second).(2) Addition of PEDOT:PSS: PEDOT:PSS is added to the SWCNT dispersion and mixed using ultrasonic treatment. Specifically, this step involves adding 5 wt% of DMSO to the PEDOT: PSS solution and mix thoroughly in a planetary mixer, then take 0.65 gram (g) of the solution to the SWCNTs solution, followed by further combining the two components by using a probe sonicator, operating at 600 W for 15 minutes and alternating between being switched on for 2 seconds and switched off for 1 second to ensure uniform blending. The dispersion is subject to centrifugation at a speed of 4000 revolutions per minute (rpm) for 30min and 80% of the supernatant is collected.(3) Addition of IL: IL is added to the PEDOT:PSS-SWCNT mixture and mixed using ultrasonic treatment. Approximately 10 mg of IL is then added, and then these materials are mixed again using ultrasonic treatment at 600 W for 15 minutes and alternating between being switched on for 2 seconds and switched off for 1 second.(4) Vacuum filtration: The resulting mixture is filtered using a vacuum filtration apparatus to create a high-conductivity flexible electrode. Vacuum filtration is performed using a 0.22 gm (micrometer) filtration membrane. The filtration time increases with the amount of material used, resulting in thicker films. Once the solution is completely dried, the film is initially cleaned using an IPA / acetone solution (volume ratio 1 : 1) to remove Triton X-100. Subsequently, extensive rinsing of the above film is conducted using deionized water.

[0058] After the film is thoroughly cleaned, it is placed in a vacuum oven for drying at about 80 °C for about 4 hours. Then, the film is fixed between two plates to obtain a flat film. The flexible electrode could be easily peeled off from the PVDF membrane after it is completely dry to achieve a high conductivity flexible electrode.

[0059] By incorporating DMSO and Triton X-100, the high conductivity flexible electrodes could be fabricated via vacuum filtration, offering advantages such as low cost, simple operation, and high efficiency.

[0060] The ternary electrode system fabricated by this fabrication method exhibits high conductivity, flexibility and durability. Specifically, the combination of SWCNTs, PEDOT ESS, and IL provides high electrical conductivity, enabling efficient ion migration and mechanical motion. The use of SWCNTs and PEDOT:PSS allows for the creation of flexible electrodes that can withstand bending and stretching without compromising their conductivity. The ternary electrode system exhibits improved durability compared to conventional electrodes, withstanding repeated cycles of ion migration and mechanical motion.

[0061] FIG. 1 illustrates the fabrication and structure of a ternary electrode system according to embodiments of the present disclosure. Part A of FIG. 1 illustrates a schematic illustration of multilayer fiber electrode preparation using vacuum filtration. Part B of FIG. 1 illustrates an optical photograph of the fabricated high conductivity flexible electrode Part C of FIG. 1 illustrates a Raman spectroscopy of the sequential optimization of the electrode. Part D of FIG. 1 illustrates the tensile properties of the electrode exhibit its excellent toughness.

[0062] The ternary electrode is modeled as a core-shell structure, where SWCNTs form the internal core and PEDOT:PSS forms the surrounding shell. This architecture facilitates both electronic and ionic transport where the SWCNTs serve as primary electron-conducting pathways; PEDOT:PSS matrix provides a continuous conductive network and enhances the film’s mechanical robustness; and IL fills the interstitial spaces and acts as a mobile ion reservoir, enabling rapid ion diffusion during actuation. In other words, the SWCNTs serve as a conductive scaffold and provide mechanical strength, while PEDOT:PSS functions as apseudocapacitive matrix that facilitates ion intercalation. The ionic liquid enhances ionic conductivity and expands the electrochemical window.

[0063] Simulations and experimental data confirm that the ion migration within the electrode is significantly enhanced by the presence of IL, which reduces ion diffusion barriers and improves charge balance during electrochemical cycling. The optimized structure minimizes resistance and enables fast, reversible actuation.

[0064] FIG. 2 and FIG. 3 illustrate the characterization of ternary electrode system performance. Parts A and B of FIG. 2 show scanning electron microscopy (SEM) images of CNT / Triton X-100 and PEDOT: PSS / DMSO films, respectively, prepared via vacuum filtration onto a PVDF support membrane. However, these films exhibited poor delamination characteristics, remaining firmly adhered to the substrate and proving unsuitable for independent, freestanding operation. In contrast, when CNT was combined with DMSO- modified PEDOT: PSS and subjected to the same vacuum filtration process, freestanding, flexible films were successfully fabricated. As illustrated in Part C of FIG. 2, varying the CNT- to-PEDOT: PSS ratio significantly influences the film morphology: at lower PEDOT: PSS content, a fibrous network structure is observed, while increasing the PEDOT: PSS ratio leads to a transition toward a granular or blocky morphology, indicating progressive coating and encapsulation of CNTs by the conductive polymer matrix This morphological evolution correlates with enhanced interfacial contact and improved mechanical integrity. X-ray diffraction (XRD) analysis (Part A of FIG. 3) and Fourier-transform infrared spectroscopy (FTIR) (Part B of FIG. 3) revealed no significant changes in the crystalline structure or chemical bonding features across different CNT / PEDOT: PSS ratios, suggesting the absence of covalent interactions between the components and confirming the formation of a physically blended, non-reactive composite. Notably, mechanical testing (Part C of FIG. 3) demonstrated a progressive increase in both Young’s modulus and maximum tensile strain with higher PEDOT: PSS content, indicating a marked enhancement in toughness and stretchability of the ternary electrode system. This improved mechanical performance, combined with the ability to form freestanding films, underscores the critical role of the DMSO-modified PEDOT: PSS in enabling both structural stability and processability, thereby facilitating scalable fabrication of flexible, high-performance electrodes.

[0065] FIG. 4 illustrates energy dispersive spectroscopy of Opt-SWCNTs / PEDOT: PSS / IL electrode. Part A of FIG. 4 depicts Sulfur (S) is uniformly distributed across the electrode, indicating homogeneous dispersion of PEDOT: PSS. The presence of carbon (C) (Part B of FIG. 4) elements corresponds to the SEM morphology, confirming the main component of thefiber is CNT Moreover, the detection of boron (B) (Part C of FIG. 4) and fluorine (F) (Part D of FIG. 4) elements suggests successful incorporation of the ionic liquid into the electrode.

[0066] FIG. 5 illustrates TEM images of SWCNTs mixed solely with PEDOT: PSS, showing poor dispersion (as shown in Part A of FIG 5), but SWCNTs and PEDOT: PSS after sequential optimization through the two-step dispersion process results in improved dispersion and a distinct core-shell structure (as shown in Part B of FIG. 5).

[0067] FIG. 6 illustrates an analysis of ion migration performance in the electrode. Part A of FIG. 6 illustrates a schematic diagram of the three-electrode measurement setup. Parts B and C of FIG. 6 illustrate specific capacitance of different electrodes with different ionic liquid contents and PEDOT: PSS respectively. Part D of FIG. 6 illustrates XPS spectra N Is, F Is and S 2p in the ternary electrode under different voltages.

[0068] FIG. 6 depicts the schematic diagram of the three-electrode measurement setup, which was used for measuring the specific capacitance. Pt, thicker silver wire, and Opt- SWCNTs / PEDOT: PSS / IL film serves as the counter electrode, reference electrode, and working electrode, respectively, with the non-aqueous 1.0 M EMIM: BF4 / acetonitrile solution as the electrolyte. The increase in ionic liquid and PEDOT: PSS content will lead to a decline in specific capacitance (as shown in Parts B and C of FIG. 6). The former may be attributed to excessive ionic liquid content causing SWCNTs aggregation, while the latter is the increase in the electrode thickness. Furthermore, XPS spectra of N Is, F Is and S 2p at different voltages were analyzed (as shown in Part D of FIG. 6), and the overall peak position shifted leftward when voltage changes from -1 V to 1 V. At the positive voltage, the electrode absorbs the anions (BF4-) and repels cations (EMIM+), so the N Is peak position of imidazolium does not change significantly. Conversely, interaction between EMIM+ and PSS- occurs with the negative voltage, resulting in the peak shifting rightward. The appearance of two groups of N I s peak can be attributed to the migration of interfacial cations near the SWCNTs, and overlaid bulk cations stabilized by the surrounding IL molecules. Meanwhile, F Is was selected to observe the movement of anions, due to the presence of F element in the BF4- anion. Under positive voltage, a large number of anions are attracted, forming numerous B-F bonds. Nevertheless, abundant electrons are injected into the electrode, producing the F ions, resulting in the appearance of two groups of F Is peaks. The peak shift of S elements is similar to the above analysis, indicating that ions migrate into the interior of the electrode under voltage, resulting in different deformations of the electrode.

[0069] Analysis is conducted on the impedance variation of different electrodes in the 1.0 M EMIM: BF4 / acetonitrile electrolyte solutions. This is illustrated in FIG. 7. For filmscomposed of SWCNTs, the electrodes exhibit only double layer capacitance, resulting in minimal impedance In contrast, there will be the interaction between ionic liquid with PEDOT : PSS, so it will show a higher impedance. The free-standing film comprising a mixture of SWCNTs and PEDOT: PSS, impedance significantly decreases, and its value is further reduced after adding the ionic liquid, comparable to that of pure SWCNTs electrode. This suggests that the ternary electrode system could better accommodate ionic liquids, leading to the fabrication of high-performance actuators.

[0070] The ternary electrode system is integrated into an ionic actuator of the present disclosure by sandwiching a thin layer of ionic electrolyte (e.g., Nafion / IL composite) disposed laterally between two electrodes. The resulting device is capable of generating large deformations under low driving voltages (typically below 5 V), with high actuation speed and repeatability.

[0071] A method for fabricating a flexible ionic actuator comprising a Nafion-based electrolyte film doped with an ionic liquid (IL), integrated with ternary electrode system in a sandwich structure will now be described. The method enables the production of a transparent, flexible, and highly ionically conductive composite film suitable for use in electroactive devices, such as ionic actuators, sensors, or artificial muscles.

[0072] The fabrication process begins with the preparation of a solid Nafion film. Specifically, 1 gram of a Nafion solution is cast onto a suitable substrate (e g., a petri dish) and dried in an oven at 80 °C for more than 12 hours to remove residual solvents and form a solid Nafion film. For applications requiring a thicker electrolyte layer, a larger volume of Nafion solution may be used, proportionally adjusting the drying time to ensure complete solvent evaporation.

[0073] The dried Nafion film is then subjected to vacuum drying to further remove any residual moisture, ensuring high purity and enhanced ionic conductivity in the final device. This step is particularly important to prevent the formation of microvoids or defects during subsequent processing.

[0074] Next, the dried Nafion film is dissolved in dimethylacetamide (DMAC) at a volume of 20 mL, using an oil bath maintained at 75 °C for more than 24 hours to ensure complete dissolution. During this dissolution step, a predetermined amount of ionic liquid (IL) is added to the solution, with the quantity being adjustable based on the desired ionic conductivity, flexibility, or actuation performance of the final device The mixture is stirred continuously for over 12 hours to achieve a homogeneous solution, ensuring uniform distribution of the ionic liquid within the Nafion matrix.

[0075] The homogeneous Nafion / IL / DMAC solution is then poured into a clean petri dish or other suitable mold and allowed to cure at about 80 °C for more than 24 hours, enabling the solvent to evaporate gradually and form a cohesive, flexible film. Following curing, the film is transferred to a vacuum oven for annealing treatment at about 150 °C for about 2 hours. This annealing step promotes molecular reorganization, enhances film transparency, reduces residual stress, and improves mechanical integrity and long-term stability.

[0076] After annealing, the resulting transparent, flexible Nafion / IL composite film is ready for integration with electrodes. The film is stacked with a pair of conductive electrodes such as the ternary electrode system as described above in a sandwich structure, with the Nafion / IL film positioned between the two electrodes.

[0077] To secure the layered structure, the assembly is placed between compression molds, with non-adhesive paper applied to both outer surfaces to facilitate clean device removal after processing. The stacked structure is then subjected to a hot-pressing step at about 120 °C under a pressure of 90 psi (pounds per square inch) for about 20 minutes, which ensures strong interfacial bonding between the electrodes and the electrolyte film without damaging the underlying materials.

[0078] Finally, the integrated device is cut into the desired shape using a precision blade, enabling fabrication of individual actuators or sensor units suitable for testing and application. The resulting ionic actuator exhibits high flexibility, transparency, excellent ionic conductivity, and reliable electrochemical performance.

[0079] The entire process is schematically illustrated in FIG. 8, which provides a step-by- step overview of the fabrication method, highlighting the sequential stages from solution preparation to final device formation.

[0080] A probable mechanism of ion migration in electrodes with various ratios of PEDOT : PSS to SWCNTs is shown in FIG 9 illustrating an analysis of ion migration in ternary electrode and simulation analysis of ion migration. Parts A and B of FIG. 9 illustrate simplifying the electrode to the core-shell structure with internal SWCNTs and external PEDOT: PSS reveals that thinner film enables rapid ion infiltration, but thicker electrodes predominantly accumulate ions at the boundaries. Part C of FIG. 9 illustrates X-ray Photoelectron Spectra (XPS) N Is spectra of ternary electrode under different voltages.

[0081] In case of low PEDOT: PSS content mixed with SWCNTs, inadequate binding of SWCNTs may lead to insufficient polymeric chain interactions and poor electrode cohesion, rendering the electrode prone to tearing. In contrast, excessive PEDOT: PSS results in a significant increase in electrode thickness and reduced conductivity. As ions migrate to theelectrode, the predominance of faradaic capacitance hinders rapid transference to the interior. To further validate the above hypothesis, ion migration simulations were conducted on electrodes with different compositions by the finite element analysis method (COMSOL Multiphysics), and the electrode was simplified to consist of internal SWCNTs encased by external PEDOT: PSS shells. The results reveal that ions rapidly permeate the entire thinner electrode, while they merely diffuse to the boundaries of the thicker electrodes. For the moderate content of PEDOT: PSS, ions migrate into the inner SWCNTs after passing through the outer layer, fully harnessing the electrochemical activity of the electrode structure. These simulation results are consistent with theoretical analysis.

[0082] The ionic actuator was tested under various voltage and frequency conditions. FIG.10 and FIG. 1 1 illustrates the ionic actuator performance of the ternary electrode system Part A of FIG. 10 presents a schematic diagram of the ionic actuator structure and its bending model under voltage. Part B of FIG. 10 presents bending strain of the ionic actuator using different electrodes. Parts A and B of FIG. 11 present voltage and frequency response of ionic actuators based on the ternary electrode with different PEDOT: PSS and SWCNTs ratios. Part C of FIG.11 presents bending response of ionic actuators with square wave input potentials varying from 0.05 Hz to 10 Hz at ±2 V. Parts D and E of FIG. 11 present Voltage and frequency response of ionic actuators based on the ternary electrode with different ionic liquid content. Part F of FIG. 11 illustrates stability measurement of the ionic actuator.

[0083] The results show that the ionic actuator initially exhibits a linear strain response to voltage, gradually reaching saturation, likely influenced by ion concentration and its electrochemical window. Voltages exceeding 2 V may induce the decomposition of the ionic liquids, leading to performance tapering off. Meanwhile, the strain gradually decreases with higher frequency, and the corresponding decline in peak-to-peak displacement from 0.05 Hz to 10 Hz is shown in Part C of FIG. 1 1 , which could be attributed to the insufficient duration of ion migration to the electrode at higher frequencies. However, both datasets suggest that the actuator achieves maximum strain at SWCNTs to PEDOT: PSS ratio of 0.8, suggesting optimal synergistic effects between the two components. Then additional ionic liquid was introduced at different ratios relative to SWCNTs (0.2, 0.5, 1.0, 2.0 and 5.0), and their voltage and frequency response are shown in Parts D and E of FIG. 11. It can be seen that ionic liquid minimally impacts actuator performance, showing enhancement with the addition of small quantities, but excessive ionic liquid leads to a slight decline, possibly due to induced carbon nanotube aggregation. Hence, the optimal ratio of SWCNTs, PEDOT: PSS and ionic liquid in the ternary electrode is estimated to be 1 : 0.8: 1, serving as the basis for the subsequentexperiments. Part F of FIG. 11 shows that the ternary electrode system actuators possess excellent stability, maintaining stable performance even after one million cycles, thus making them reliable for practical applications.

[0084] FIG. 12 illustrates the performance variation of composite electrodes and ionic actuators as a function of varying ratios of single-walled carbon nanotubes (SWCNTs), PEDOT PSS, and ionic liquid. Part A of FIG. 12 shows the cyclic voltammetry (CV) curves of electrodes with different SWCNTs to PEDOT:PSS ratios. As the PEDOT:PSS content increases, the area under the CV curve decreases, indicating a reduced electrochemical active surface area and diminished ion accommodation capacity. This trend suggests that an excess of PEDOT:PSS may hinder ion transport or block accessible sites within the composite.

[0085] Optimization studies revealed that the highest actuation performance is achieved at a SWCNTs to PEDOT:PSS ratio of 0.8. The corresponding CV curve and electrochemical impedance spectroscopy (EIS) data for the actuator fabricated under these conditions are presented in Parts B and C of FIG. 12, respectively. These results confirm enhanced charge transfer kinetics and an improved electrochemical stability at this ratio.

[0086] Part D of FIG 12 shows the CV curves of electrodes with varying ionic liquid contents, indicating only minor variations in electrochemical response. This suggests that the ionic liquid content has a limited influence on the overall electrode performance within the tested range. Parts E and F of FIG. 12 present the CV curve and EIS data of the ionic actuator prepared using the optimized composition of SWCNTs:PEDOT:PSS:ionic liquid = 1:0.8:1, demonstrating consistent and stable electrochemical behavior.

[0087] FIG. 13 and FIG. 14 illustrate an analysis of device structure optimization. Part A of FIG. 13 provides a schematic representation of the design concept for a smart ionic actuator, which is engineered to simultaneously achieve high actuation strain and significant blocking force — two performance parameters that are typically in conflict due to inherent trade-offs in device mechanics. As illustrated in Part B of FIG. 13, a cantilever beam model analysis confirms that increasing the overall device thickness and width enhances the blocking force, while excessive device length leads to increased energy dissipation along the free end, thereby reducing effective force output.

[0088] The performance of the actuator was systematically evaluated with respect to four key structural parameters: (i) ionic liquid concentration in the electrolyte (Part A of FIG. 14), (ii) the ratio of electrolyte thickness to electrode thickness (Parts B and C of FIG. 14), (iii) device width (Part D of FIG. 14), and (iv) the number of stacked actuator layers (Part E of FIG. 14). The results demonstrate that optimal performance is achieved within a specific range ofeach parameter, with deviations leading to reduced actuation efficiency. Notably, the ionic actuator configuration disclosed achieves a strain of 2.59% and a blocking force of 2.2 mN, as confirmed by experimental data.

[0089] Part F of FIG. 14 compares the strain and normalized blocking force of the proposed ionic actuator with representative literature data, demonstrating superior performance of the present ionic actuator relative to conventional actuators. This comparison underscores the technical advantage of the proposed ionic actuator, particularly in balancing high strain with high blocking force.

[0090] Parts A and B of FIG. 15 illustrate simulated results of ion migration within the electrode and the corresponding actuator bending behavior as a function of time and applied voltage, respectively. Part A of FIG. 15 shows the simulated distribution of ions at the electrode-electrolyte interface and their progressive diffusion into the electrode bulk upon application of an electric field. The simulation assumes an initial ion concentration at the interface, with ion migration driven by the applied voltage. As the voltage is sustained, ions gradually penetrate the electrode material, leading to volumetric expansion of the electrode layer.

[0091] Part B of FIG. 15 depicts the time-dependent bending strain of the ionic actuator under varying voltage levels. The results indicate that higher applied voltages accelerate the ion migration rate, resulting in a more rapid and extensive ion influx into the electrode. This enhanced ion incorporation leads to greater electrochemical expansion of the electrode, thereby increasing the bending strain. The correlation between voltage magnitude, ion migration kinetics, and mechanical deformation is consistent with the underlying principle of ionic actuation, where the degree of bending is directly governed by the extent of ion insertion and the resulting volume change in the active material.

[0092] FIG. 16 illustrates the performance enhancement achieved by incorporating DMSO into the electrode material. Parts A and B of FIG. 16 show the cyclic voltammetry (CV) curves and specific capacitance variation of electrodes after DMSO integration, demonstrating a significant increase in both parameters. The CV curve of an electrode with a DMSO-to- PEDOT:PSS ratio of 0.8, recorded at varying scan rates (Part C of FIG. 16), exhibits two distinct peaks, which are attributed to the interaction between the ionic liquid and the PEDOT:PSS matrix. Parts D and E of FIG. 16 depict the voltage and frequency response of electrochemical actuators fabricated using DMSO-modified electrodes, respectively, revealing superior actuation performance compared to unmodified counterparts. The corresponding CV curve of the ionic actuator based on the DMSO-modified electrode is shown in Part F of FIG.16, confirming enhanced electrochemical activity and ion accessibility. These results collectively indicate that DMSO modification improves the ion transport properties and electrochemical performance of PEDOT:PSS-based electrodes, thereby enabling enhanced actuation efficiency and stability.

[0093] FIG. 17 illustrates the performance variation resulting from different contents of Triton X-100 used to disperse SWCNTs. Part A of FIG. 17 shows the CV curves of electrodes prepared with different Triton X-100 concentrations, while Part B of FIG. 17 presents the corresponding variation in specific capacitance. Part C of FIG. 17 displays the CV curves of an electrode treated with 50 mg of Triton X-100 at different scan rates. Parts D and E of FIG. 17 show the voltage and frequency response, respectively, of electrochemical actuators fabricated using electrodes prepared with varying amounts of Triton X-100 Part F of FIG. 17 illustrates the CV curve of an ionic actuator prepared using an electrode with 50 mg of Triton X-100.

[0094] In the present work, Triton X-100 was employed as a dispersing agent for SWCNTs during electrode fabrication. However, it was observed that residual surfactant may adversely affect the electrochemical performance of the resulting electrode. To remove the Triton X-100, various organic solvents were evaluated, and a 1: 1 volume ratio mixture of acetone and isopropyl alcohol (IPA) was identified as the most effective cleaning agent. Despite the variation in Triton X-100 content used during dispersion, no significant changes were observed in the CV curves across different samples. Nevertheless, a slight reduction in specific capacitance was noted with increasing Triton X-100 content, suggesting that excess surfactant may hinder ion accessibility or reduce active surface area.

[0095] Based on these findings, a dispersion ratio of 50 mg Triton X-100 per 10 mg of SWCNTs was selected as the optimal condition. The CV curves of the resulting electrode at different scan rates (as shown in Part C of FIG. 17) exhibit consistent behavior, confirming reproducibility. While the voltage response of the ionic actuators showed minimal variation across different Triton X-100 loadings, the frequency response was improved when lower amounts of Triton X-100 were used.

[0096] FIG. 18 illustrates the structural evolution of Nafion doped with ionic liquid and subjected to annealing, as observed from mesoscopic (Part A of FIG. 18) and microscopic (Parts B to E of FIG. 18) perspectives.

[0097] Nafion, a sulfonated tetrafluoroethylene-based fluoropolymer copolymer, is selected for its mechanical properties and high ionic conductivity. Upon incorporation of an ionic liquid (IL), Nafion exhibits a characteristic two-phase microstructure at the mesoscopic scale,consisting of a hydrophilic ionic phase enriched with the IL and a hydrophobic non-ionic phase composed of the fluorocarbon backbone. This phase-separated morphology is stabilized by solvation effects and is critical to the material’s ion transport performance.

[0098] The addition of ionic liquid enhances the volume fraction of the conductive ionic phase, thereby improving the overall ionic conductivity of the film. However, the incorporation of IL also induces significant swelling, leading to an increase in film thickness. Excessive IL content, particularly when combined with low Nafion concentration, may disrupt polymer chain entanglement and hinder proper polymerization, resulting in mechanical instability and film tearing.

[0099] To address these limitations, an annealing treatment was applied to the Nafion / IL films. Annealing enhances the crystallinity of the Nafion matrix, leading to improved mechanical strength and increased Young’s modulus. However, this process also promotes the expulsion of IL from the bulk, resulting in surface precipitation and a concomitant reduction in ionic conductivity. Additionally, the annealing-induced contraction in lateral dimensions leads to a net increase in film thickness, attributed to longitudinal shrinkage.

[0100] At the microscopic level, Nafion is a random copolymer comprising a semicrystalline polytetrafluoroethylene backbone and randomly grafted side chains terminating in sulfonic acid groups (-SCLH), which may be associated with counterions. The inherent chemical incompatibility between the hydrophobic backbone and hydrophilic side chains drives spontaneous phase separation, which is further amplified by solvation in the presence of ionic liquid. In this study, the ionic liquid employed is l-ethyl-3- methylimidazolium tetrafluoroborate (EMIM / BF4), where the EMIM cations interact electrostatically with the sulfonic acid groups on the side chains.

[0101] This interaction facilitates two distinct ion transport mechanisms: (i) surface hopping of ions between adjacent sites, and (ii) bulk transport through interconnected ionconducting channels. The contribution of bulk transport to overall conductivity is significantly greater than that of surface hopping. At low IL concentrations, the structure exhibits an inverted micelle morphology. As the IL content increases, the ionic clusters grow in size and coalesce into percolating ion channels, thereby enhancing ion transport efficiency. The interchain spacing (d-spacing), measured via X-ray scattering, increases with IL concentration due to the enhanced electrostatic repulsion between sulfonate groups and the swelling effect of the IL, further facilitating ion mobility.

[0102] FIG. 19 illustrates the influence of DMAC content on the performance of Nafion films. Part A of FIG. 19 shows the Electrochemical Impedance Spectroscopy (E1S) data, PartB of FIG. 19 presents the ionic conductivity, and Part C of FIG. 19 depicts the film thickness of pure Nafion films prepared using varying concentrations of N,N-dimethylacetamide (DMAC) as solvent. To evaluate the effect of the solvent on the functional performance of Nafion, Nafion was dissolved in DMAC at different loadings, followed by solvent evaporation and recasting into freestanding films. As the Nafion concentration in DMAC increased, the resulting films exhibited a significant increase in thickness, which corresponded to a rise in measured impedance, as expected due to the increased ion transport path length. However, the calculated ionic conductivity remained substantially unchanged across the range of Nafion concentrations investigated. This result indicates that DMAC functions solely as a processing solvent and does not alter the intrinsic ionic transport properties of the Nafion matrix. The consistent conductivity, despite variations in film thickness and impedance, confirms that the solvent does not participate in or modify the ion-conducting network, provided that the recasting process is reproducible and residual solvent is effectively removed. Therefore, DMAC is confirmed to be an inert and suitable solvent for the fabrication of Nafion -based films without affecting their electrochemical performance.

[0103] FIG. 20 illustrates the performance exploration of Nafion / ionic liquid (IL) membranes with different ionic liquid concentrations and annealing processes. Part A of FIG. 20 summarizes the experimental parameters for the fabricated membranes, including varying ionic liquid concentrations and annealing conditions. Part B of FIG. 20 shows the mass variation of Nafion / IL membranes over time, reflecting the degree of ionic liquid migration or precipitation. Parts C and D of FIG. 20 present the thickness and ionic conductivity, respectively, of the membranes prepared with different ionic liquid concentrations.

[0104] As previously discussed, both the ionic liquid concentration and post-processing annealing significantly influence the structural and electrochemical performance of Nafion / IL membranes. To evaluate these effects, multiple films were prepared with varying ionic liquid loadings and subsequently annealed at 150 °C, as indicated in Part A of FIG. 20. Due to the limited solubility of ionic liquid in Nafion, phase separation and precipitation were observed, particularly at elevated concentrations.

[0105] Mass variation measurements (as shown in Part B of FIG. 20) revealed that all films exhibited progressive mass loss at room temperature, indicating ongoing ionic liquid precipitation. The extent of mass loss increased with higher ionic liquid content, confirming that excess IL tends to migrate out of the matrix. This phenomenon correlates with the observed increase in film thickness (as shown in Part C of FIG. 20), which is attributed to the formation of a surface-rich layer or phase-separated domains during precipitation.

[0106] At the same time, ionic conductivity (as shown in Part D of FIG. 20) increased with higher ionic liquid content, reflecting enhanced ion availability within the membrane matrix However, upon annealing at 150 °C, significant mass loss was observed — exceeding 20% in the 100% IL-loaded film after 2 hours — indicating accelerated removal of the volatile or less- stably bound ionic liquid. While film thickness remained elevated post-annealing, likely due to residual structural reorganization, ionic conductivity decreased slightly. This reduction is attributed to the partial loss of ionic liquid from the conductive pathways, thereby diminishing the number of mobile charge carriers.

[0107] These results demonstrate a trade-off between high ionic liquid loading, beneficial for conductivity, and thermal stability. Annealing can induce structural reorganization but may also lead to irreversible loss of ionic liquid, particularly at high concentrations. Thus, optimal performance requires balancing ionic liquid content and annealing conditions to maximize conductivity while minimizing long-term instability due to phase separation.

[0108] FIG. 21 illustrates the tensile properties of Nafion / ionic liquid (IL) membranes. Part A of FIG. 21 shows the stress-strain curves of membranes subjected to different annealing conditions, revealing a two-stage deformation behavior: (i) an initial elastic deformation region at low strains, and (ii) a subsequent plastic deformation region at higher strains. As shown in Parts B and C of FIG. 21, the Young’s modulus in the plastic deformation region increases significantly upon thermal treatment, indicating enhanced resistance to permanent deformation. While variations in Young’s modulus between different annealing temperatures were observed, the most consistent and pronounced improvement in mechanical toughness was achieved at 150 °C. Consequently, all samples were uniformly subjected to annealing at 150 °C after recasting to ensure reproducibility and optimal mechanical performance.

[0109] Subsequently, the influence of ionic liquid concentration on tensile properties was evaluated. Part D of FIG. 21 presents the stress-strain curves of membranes with varying IL content, revealing that, in the absence of annealing, increasing IL concentration leads to a marked deterioration in mechanical strength and stiffness. This degradation is attributed to the plasticizing effect of the IL, which disrupts hydrogen bonding and interchain interactions within the Nafion matrix, thereby inhibiting effective cross-linking and reducing structural integrity.

[0110] However, after annealing at 150 °C, the mechanical performance is substantially improved. Although the maximum tensile strain increases with higher IL concentration (Part F of FIG. 21), the Young’s modulus remains lower than that of pristine Nafion. Nevertheless, the annealing treatment effectively counteracts the detrimental effects of IL by promotingmolecular reorganization and enhancing intermolecular interactions. As shown in Parts E and F of FIG. 21, the Young’s modulus exhibits a non-monotonic dependence on IL concentration, with an optimal balance between stiffness and ductility achieved at intermediate IL loadings. This indicates that while IL enhances flexibility, annealing at 150 °C enables the formation of a more stable and mechanically robust network.

[0111] These results demonstrate that the mechanical performance of Nafion / IL membranes is not solely governed by IL content but is critically dependent on post-processing thermal treatment. The synergistic combination of controlled IL incorporation and optimized annealing at 150 °C enables the design of membranes with tailored mechanical properties — offering both enhanced toughness and tunable elasticity — thereby enabling practical application in flexible electroactive systems.

[0112] FIG. 22 illustrates the structural analysis of Nafion / ionic liquid (IL) membranes via small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and two- dimensional (2D) SAXS diffraction. Part A of FIG. 22 shows the SAXS spectra for the pure Nafion membrane before and after annealing, and the recasting film shows no significant peaks, but two distinct peaks could be observed at 0.058 and 0.217 A-1, corresponding to the matrix knee and ionomer peak, respectively. Part B of FIG. 22 shows the SAXS curves of Nafion / IL membranes with varying IL concentrations, where the matrix peak disappears, and the ionomer peak shifts to a lower scattering vector ( ), indicating a significant increase in the average interionic domain spacing. This shift reflects the disruption of the original nanostructure due to IL incorporation, leading to a reduction in crystallinity of the Nafion matrix and an enlargement of the ionic domain spacing. Notably, the WAXS data (as shown in Part C of FIG. 22) reveal two sharp peaks at 1.26 A1and 2.76 A '. corresponding to inter- and intracrystalline spacings of the fluorocarbon (-CF2-) chains in the crystalline structure, respectively. These peaks remain largely unchanged before and after annealing, indicating that the crystalline structure of the fluorocarbon backbone is preserved, even in the presence of IL.

[0113] Using Bragg’s equation, the d-spacing of the crystalline regions was calculated. As the IL concentration increases, the d-spacing significantly increases, reflecting the expansion of the ionic domains and the progressive disruption of the original ordered structure. A slight further increase in d-spacing is observed after annealing, which may be attributed to partial precipitation of IL and improved crystallinity of the fluorocarbon matrix, resulting in enhanced structural ordering in the non-ionic regions.

[0114] Two-dimensional SAXS patterns (as shown in Part G of FIG. 22) confirm the isotropic nature of the scattering, indicating that ionic clusters and crystallites are randomlyoriented within the membrane. The pure Nafion film exhibits two concentric rings, corresponding to the periodicity of the ionic and matrix phases. However, in membranes with 70 wt% IL, only a single ring is observed, suggesting a loss of long-range periodic order and the formation of a more homogeneous, disordered ionic network. This morphological evolution is consistent with the SAXS and WAXS data and supports the conclusion that IL incorporation modifies the nanostructure of Nafion by suppressing crystallinity and increasing ionic domain spacing.

[0115] These results demonstrate that the incorporation of ionic liquids induces a structural transformation in Nafion, characterized by reduced matrix crystallinity, expanded ionic domain spacing, and isotropic domain orientation. The ability to tune the nanoscale morphology via IL concentration and thermal treatment enables precise control over the membrane’s ionic conductivity, mechanical flexibility, and electrochemical performance — key attributes for advanced applications in electroactive devices and energy storage systems.

[0116] FIG. 23 illustrates the Fourier-transform infrared (FTIR) spectra of Nafion / ionic liquid (IL) membranes under annealing process and different concentrations. The spectra reveal two distinct peaks, one attributed to the -SO3- symmetric stretching vibration bands at about 1056 cm and the other to the asymmetric stretching of -SO3- groups at about 1201 cm . The positions of both peaks shift noticeably with increasing ionic liquid content, suggesting a stronger interaction between the ionic liquid and the sulfonic acid group.

[0117] FIG. 24 illustrates the influence of electrolyte thickness (Part A of FIG. 24) and electrode thickness (Part B of FIG. 24) on the performance of the electrochemical actuator.

[0118] The results demonstrate a direct correlation between electrolyte thickness and device dynamics. Thinner electrolytes exhibit reduced ion transport resistance due to shorter migration pathways, enabling faster ion diffusion and quicker electrochemical response. This leads to enhanced actuation speed and larger displacement under applied voltage Additionally, the reduced mechanical stiffness of thinner electrolytes contributes to greater flexibility and improved responsiveness, making them particularly suitable for applications requiring high- frequency operation or rapid actuation cycles.

[0119] Conversely, thicker electrolytes exhibit increased mechanical stiffness and longer ion migration distances, resulting in higher ionic resistance and slower response times. However, this structural configuration enables the generation of a higher blocking force due to increased mechanical load-bearing capacity and greater stored electrochemical energy. Thus, thicker electrolytes are advantageous in applications where high force output and stability under load are prioritized over speed.

[0120] Similarly, electrode thickness plays a role in determining actuator performance. Increasing electrode thickness enhances the available volume for ion insertion and redox reactions, thereby increasing the total charge storage capacity and improving both displacement and blocking force Thicker electrodes provide a greater number of ion migration sites and facilitate more extensive electrochemical activity, which directly translates into improved actuation performance.

[0121] The ionic actuator is advantageously configurable in terms of relative thicknesses of the electrolyte and the electrode thickness. The ionic actuator may be configured to customize the device performance, e.g., in some applications, thinner configurations may be preferred for higher speed and responsiveness, while in other applications, thicker configurations may be preferred for greater force output and energy storage. This tunability enables the proposed ionic actuator to be specifically adapted to diverse application requirements, ranging from highspeed micro-actuators to high-force, low-speed systems, without requiring fundamental changes in material composition.

[0122] FIG. 25 illustrates the electrochemical and mechanical performance of the ionic actuator as a function of ionic liquid concentration, showing the cyclic voltammetry (CV) curve (Part A of FIG. 25), blocking force Part B of FIG. 25, and electrochemical impedance spectroscopy (BIS) data (Part C of FIG. 25). The CV curves of the actuators at different ionic liquid concentrations exhibit no significant variation, yet the impedance notably decreases, which could be attributed to the higher conductivity of membrane with higher ionic liquid content. Moreover, films with higher concentrations of ionic liquid possess smaller Young’s modulus, resulting in a reduction in device thickness under the hot pressing, which also contributes to the decline of impedance, and this reduction in thickness leads to a decrease in the blocking force.

[0123] FIG. 26 illustrates the effect of electrode thickness on device performance. Parts A to C of FIG. 23 show the cyclic voltammetry (CV) curve, specific capacitance, and electrical conductivity of electrodes fabricated with varying thicknesses, while Parts D to F of FIG. 26 present the corresponding CV curve, blocking force, and electrochemical impedance spectroscopy (EIS) data of the resulting actuators.

[0124] With the increased usage of SWCNTs in electrode fabrication, there is a corresponding decrease in the CV curve of the electrodes, resulting in a reduction of the specific capacitance. Concurrently, the thickness of electrodes gradually increases, while their conductivity remains relatively unchanged (as shown in Parts A to C of FIG. 26). Ionic actuators with thicker electrodes exhibit higher CV curves, indicating more ions migrating tothe electrodes, thereby increasing the blocking force. Hence, appropriately increasing the thickness of the actuator electrodes could improve its performance.

[0125] FIG. 27 illustrates the effect of electrolyte thickness on actuator performance. Parts A to C of FIG. 27 show the cyclic voltammetry (CV) curve, blocking force, and electrochemical impedance spectroscopy (EIS) data of ionic actuators fabricated with electrolytes of varying thicknesses. Part D of FIG. 27 provides a visual representation of the observed phenomenon: at higher ionic liquid concentrations, precipitation occurs during the hot-pressing process, leading to poor adhesion or local flattening of the electrolyte layer.

[0126] As shown in Part A of FIG. 27, the CV curve area increases with electrolyte thickness, indicating enhanced ion transport and greater electrochemical activity. However, the blocking force (Part B of FIG 27) does not increase monotonically with thickness; rather, it reaches a maximum at an intermediate thickness, with the lowest blocking force observed in the thickest electrolyte. This non-monotonic behaviour is attributed to the reduced mechanical compliance of thicker electrolyte layers, which exhibit higher stiffness and limited deformability under load. Consequently, the ionic actuator's ability to generate large displacement or high blocking force is diminished in thicker configurations.

[0127] Moreover, the increased ionic liquid content in thicker electrolytes promotes precipitation during hot pressing (as shown in Part D of FIG. 27), particularly when processing conditions are not precisely controlled. Precipitation compromises the homogeneity of the electrolyte layer and leads to interfacial defects, such as delamination or poor adhesion between the electrolyte and electrode layers. While lower pressing pressure results in insufficient interfacial bonding, excessive pressure may cause mechanical damage to the soft, porous electrolyte structure, further degrading performance.

[0128] FIG. 28 illustrates the blocking force variation of the proposed device under different voltages. It is observed that the blocking force increases linearly with the voltage, and the voltage for object grasping can be selected according to the object's weight.

[0129] Thicker electrolytes enhance ion availability and electrochemical response; the performance of ionic actuators would appear to be ultimately limited by mechanical rigidity and processing-induced defects. This highlights a critical trade-off in conventional ionic actuators: an optimal electrolyte thickness that exists that balances ionic conductivity, mechanical compliance, and interfacial integrity. Deviating from this optimum, particularly by increasing thickness beyond a certain threshold, results in reduced blocking force and degraded device reliability observed in conventional actuators.

[0130] This finding accounts for the challenges faced by conventional ionic actuators: electrolyte thickness must be carefully optimized to maximize ionic transport while preserving sufficient mechanical flexibility and interfacial adhesion. Excessive thickness, despite increased ion content, leads to performance degradation due to limited deformability and processing challenges.

[0131] It is proposed to provide a multi-segment actuator having two or more segments coupled to one another, in which each of the segments is an ionic actuator of the present disclosure. The deformation achievable by one such multi-segment actuator is contributed by the respective deformation of each ionic actuator (or segment) forming the multi-segment actuator. An actuator system of the present disclosure may be formed by one or more of the multi-segment actuator For example, the actuator system of the present disclosure may include two fmger-like multi-segment actuator, with each finger (each multi-segment actuator) having one or more segments, each segment having one ionic actuator of the present disclosure. It can be appreciated that the ionic actuator enables multi-segment actuation with large deformations. By applying different phase voltages to individual segments, the multi-segment actuator can achieve complex bending and multi-directional motion. This capability can be advantageously exploited in applications requiring precise spatial control. Further, it was experimentally verified that the ionic actuator is capable of achieving a maximum strain of over 10% and could generate sufficient force for micro-scale manipulation tasks. In other words, unlike the conventional ionic actuator where there is an unavoidable trade off between strength and flexibility, the multi-segment actuator based on the ionic actuator of the present disclosure could provide both the strength and the flexibility required for many micro-scale manipulation tasks. In addition, the electrode-electrolyte interface is capable of remaining stable over thousands of actuation cycles, with minimal degradation in performance, showing that it is a viable device for use in many practical applications

[0132] FIG. 29 illustrates an exemplary embodiment of an actuator system 2600. The actuator system 2600 includes an ionic actuator 2610 having a pair of electrodes 2611, a flexible electrolyte film 2612 disposed laterally between the electrodes 2611, and a voltage source 2620 connected to the electrodes 2611 to apply an electric field across the electrolyte. In this embodiment, the flexible electrolyte film 2612 extends longitudinally beyond the ends of the electrodes 2611, such that it is longer in the longitudinal direction than the electrodes themselves. The electrodes 261 1 are formed from the ternary electrode system as described above. Electrical connections are established between the voltage source 2620 and one end of each electrode 2611, located proximate to the terminal end of the electrode. Upon applicationof a voltage, ion migration occurs within the electrolyte film, leading to localized electrochemical reactions in the electrode materials. This results in differential swelling in regions where cations are inserted or contraction where counter-ions are extracted, inducing macroscopic mechanical deformation across the actuator’s cross-section This differential expansion and contraction generate a bending moment, causing curvature in the actuator body, with maximum deflection occurring at the free end of the actuator that is remote from the electrical connection point. The extent of bending is directly correlated to the magnitude of strain developed in the electrode layer. As described above the ternary electrode system achieves a strain of 2.59%. Furthermore, the actuator achieves a blocking force of 2.2 mN, which corresponds to the maximum mechanical resistance the device can sustain without deformation, demonstrating sufficient mechanical output for applications requiring precision motion control or load-bearing capability. The extended, monolithic electrolyte film ensures uniform ion transport throughout the active area, minimizing concentration gradients and enabling consistent actuation across the entire length of the actuator. This uniformity reduces localized stress concentrations at the electrode-electrolyte interface and at the electrical connection point, thereby enhancing long-term reliability and fatigue resistance. The combination of high strain, measurable blocking force, and controlled bending behaviour confirms that the disclosed actuator design achieves a favourable balance between actuation performance and structural integrity, enabling practical deployment in soft robotic systems, adaptive gripper and micro-positioning devices.

[0133] In the embodiment illustrated in FIG. 29, the application of voltage induces a directional deformation of the electrodes, as indicated by the arrow 2630, resulting in a bending or elongation motion of the actuator body in the region distal to the electrical connection. This deformation arises from asymmetric ion uptake and redistribution within the electrode materials, driven by the electric field applied across the flexible electrolyte film, thereby enabling controlled, reversible mechanical actuation.

[0134] FIG. 30 illustrates an exemplary embodiment of an actuator system 2700 including a multi-segment actuator made of a plurality of the proposed ionic actuator. The system 2700 includes two or more ionic actuators 2610, each constructed identically in principle but optionally differing in physical parameters such as length, thickness, or electrode density. The individual actuators 2610 are coupled longitudinally in series to form a continuous multisegment actuator structure. This is achieved by aligning the electrodes of adjacent ionic actuators in sequence, such that the flexible electrolyte film 2612 of a first ionic actuator 2610a is in direct lateral contact with the electrolyte film 2612 of a second ionic actuator 2610b. Thecontiguous arrangement of the electrolyte films forms a continuous, flexible ion-conductive pathway along the length of the actuator system, enabling uninterrupted ion transport across segment boundaries.

[0135] The contiguous electrolyte structure prevents interfacial delamination, enhances mechanical integrity, and ensures uniform ion distribution throughout the entire actuator system. As a result, the multi-segment actuator behaves as a single, continuous deformable body, capable of exhibiting complex, coordinated motion with multiple degrees of freedom. This configuration enables large-amplitude, spatially distributed actuation while maintaining structural robustness and reliable electrochemical performance across all segments.

[0136] In the embodiment illustrated in FIG. 30, the actuator system 2700 is configured such that the same electrical polarity is applied to corresponding electrode terminals on the same side of each individual ionic actuator 2610. This configuration ensures that all segments deform in a synchronized manner, resulting in uniform, directional motion, such as linear extension or bending, in the same direction along the actuator’s length when a voltage is applied. This enables the multi-segment system to function as a single, coordinated actuator with enhanced stroke length and force output.

[0137] In an alternative embodiment, as shown in FIG. 31, opposing electrical polarities are applied to the electrodes on the same side of adjacent segments. This differential actuation causes adjacent segments to deform in opposite directions, resulting in a curved, S-shaped deflection of the entire actuator system. This configuration enables complex, programmable motion profiles, such as bending, twisting, or shape morphing, and is particularly suited for applications requiring adaptive or biomimetic movement, such as soft robotics or artificial muscles.

[0138] The two or more ionic actuators 2610 in the multi-segment system may include segments with varying physical characteristics, such as differences in thickness, length, or cross-sectional geometry. These geometric variations enable tailored actuation responses across the system. For instance, thicker segments exhibit higher mechanical stiffness, resulting in greater force output but reduced strain and displacement, whereas thinner segments allow for larger actuation amplitude and greater flexibility. Similarly, longer segments are more prone to bending under applied actuation, enabling larger curvature and elongated deformation, while shorter segments exhibit faster response times due to reduced electrical and ionic transport path lengths. By strategically combining segments with differing dimensions, the actuator system can be engineered to achieve non-uniform deformation patterns, such as spatially varying curvature, localized bending, or complex shape morphing, thereby enablingcustomized motion profiles. This design flexibility allows for the realization of biomimetic or application-specific actuation behaviours, such as graded bending in soft robotic limbs or adaptive stiffness in responsive structures.

[0139] In other embodiments, the thickness ratio between the electrode layer and electrolyte layer may be independently varied across segments. Since electrode thickness directly influences ion accessibility, mechanical compliance, and electrical resistance, such variation allows fine-tuning of the actuation kinetics, stroke, and force output in a segment-specific manner. For instance, a thicker electrode may enhance charge storage capacity and force generation, while a thinner electrode may improve response speed and flexibility. The ability to spatially modulate both geometric parameters and electrode to electrolyte thickness ratios enables the design of highly adaptive, multi-functional actuator systems with programmable deformation behaviour.

[0140] In yet a further embodiment, the two serially connected ionic actuators 2610 may be fabricated as a monolithic structure comprising a single, continuous electrolyte film and two pairs of electrodes sequentially arranged along the length of the electrolyte film. The ionic actuator is formed by hot pressing the electrodes onto opposite surfaces of the electrolyte film, with a predefined gap maintained between the two electrode pairs. This gap serves as an electrically insulating region, preventing direct current flow between the segments while enabling the two ionic actuators to be connected in series. This fabrication method allows for scalable production of serially connected actuators with precise control over segment length, electrode alignment, and inter-segment gap, facilitating the design of multi-stage actuators for applications requiring large, stepwise deformations such as in soft robotics, adaptive prosthetics, or micro-positioning systems.

[0141] The voltage source 2620 may be a controller. The controller is a programmable electronic device configured to regulate the operation of the ionic actuator employing the ternary electrode system. It comprises a microprocessor-based circuit with input / output interfaces for receiving user-defined actuation signals and delivering precise voltage pulses to the actuator electrodes. The controller supports adjustable parameters including amplitude (±0.5 V to ±5 V), frequency (0.01 Hz to 50 Hz), and waveform type (square, sinusoidal, or pulsed), enabling dynamic control of bending strain and response speed. It may include feedback mechanisms, such as integrated strain sensors or capacitive monitoring, to enable closed-loop operation, allowing real-time adjustment of applied voltage to maintain desired actuation performance. The controller is further equipped with a memory module for storing predefined actuation profiles and a communication interface (e g., USB, Bluetooth) forintegration into larger systems, such as soft robotics or adaptive optical devices. By optimizing voltage and frequency inputs in real time, the controller enhances actuator efficiency, reduces energy consumption, and ensures long-term stability, particularly under repeated or high- frequency cycling.

[0142] The controller is electronically connected to each ionic actuator via individual electrode contacts. The controller is configured to apply independent voltage signals to each ionic actuator, enabling precise spatial and temporal control. When both voltage signals have the same polarity (e.g., both positive), the actuators deform in the same direction. When the voltage signals have opposite polarities, the actuators deform in opposing directions, enabling complex motion such as twisting or folding. This allows for bidirectional actuation within a single system.

[0143] The ionic actuators may be mounted on a base 2960 as shown in FIG. 32, which provides structural support and enables integration into larger devices. The electrodes of each actuator facing toward the central axis are electrically coupled to a common polarity of the voltage source. This ensures uniform actuation direction across all segments and synchronized motion during radial contraction / expansion. This is particularly useful for gripper or clamplike applications.

[0144] FIG. 33 shows an embodiment where two or more ionic actuators 2610 in the multisegment system are mounted on a base 2960. In this configuration, the electrodes of each actuator facing toward the central axis are electrically coupled to a common polarity of the voltage source. This ensures uniform actuation direction across all segments and synchronized motion during radial contraction / expansion. In an alternative embodiment, the electrodes of each actuator facing toward the central axis are electrically coupled to opposing polarity of the voltage source. This differential actuation causes adjacent segments to deform in opposite directions, resulting in a curved, S-shaped deflection of the entire actuator system. This configuration enables complex, programmable motion profiles, such as bending, twisting, or shape morphing, and is particularly suited for applications requiring adaptive or biomimetic movement, such as soft robotics or artificial muscles.

[0145] FIG. 34 shows an embodiment where four ionic actuators are radially arranged on a circular base 2960 spaced apart from one another at equal angular intervals (at 90° intervals in this embodiment) around the central axis. In this arrangement electrodes facing the center are connected to the positive terminal while outer electrodes to the negative.

[0146] FIG. 35 shows an embodiment where four pairs of ionic actuators are radially arranged on a circular base 2960 spaced at 90° intervals. In this arrangement electrodes facingthe center are connected to the positive terminal while outer electrodes to the negative. In an alternative embodiment, the electrodes of each actuator facing toward the central axis are electrically coupled to opposing polarity of the voltage source.

[0147] FIG. 36 shows an embodiment where four ionic actuators are arranged along a linear base 2960 and evenly arranged along the length of the base 2960. The controller applies voltage signals with varying phases to deform the ionic actuators in a wave-like pattern, simulating a sweeping motion for cleaning or scraping. FIG. 37 shows an embodiment where four pairs of ionic actuators are arranged along a linear base 2960 and evenly arranged along the length of the base 2960.

[0148] While FIG. 33 to FIG. 37 illustrate various embodiments employing an even number of ionic actuator pairs, an odd number of ionic actuator pairs may likewise be implemented.

[0149] The proposed actuator system is suitable for applications in soft robotics, medical devices (e.g., minimally invasive surgical tools), prosthetics, adaptive grippers and manipulators, microfluidic systems, and wearable technology.

[0150] FIG. 38 and Fig 39 illustrate various applications of the multi-segment actuator based on the proposed ionic actuator, demonstrating its potential in precision manipulation and programmable motion control. Part A of FIG. 38 shows a two-claw gripper fabricated using the proposed actuator system, specifically designed for grasping a microlens, highlighting its suitability for microfabrication, optical assembly, and miniaturized manufacturing processes. The gripper exhibits reliable performance across the full operational cycle: effective gripping, precise lifting, stable holding, and controlled release, thereby validating the ionic actuator’s high strain capability and blocking force under real-world conditions. To further demonstrate the actuator system’s versatility, collaborative operation of multiple ionic actuators was investigated. PartB of FIG. 38 illustrates a schematic of two ionic actuators connected in series. When driven with in-phase voltages, the ionic actuators exhibit synchronized, co-directional motion, resulting in large-scale, uniform deformation. In contrast, applying reverse-phase voltages induces counter-directional actuation, enabling complex S-shaped deformation, demonstrating the actuator system’s ability to achieve tuneable, multi-mode motion through electrical control. For a more complex demonstration, a four-claw gripper was employed in a Tower of Hanoi puzzle, as shown in Part A of FIG. 39. This application requires at least seven independent grasping and releasing actions to complete a single transfer, illustrating the actuator system’s capacity for precise, sequential, and coordinated motion. These results collectively confirm the actuator system’s potential for advanced applications in robotics,automation, and micro-scale handling systems, leveraging its large strain, high blocking force, and programmable multi-segment actuation

[0151] The proposed actuator system, based on DMSO-modified PEDOT: PSS and exhibiting high flexibility, low operating voltage, and large reversible deformation, is broadly applicable across diverse technological fields. In robotics, the actuator system enables soft, adaptive, and biomimetic motion, facilitating the development of compliant robotic grippers and soft robotic systems capable of safe interaction with delicate or irregularly shaped objects. In the biomedical domain, the actuator system’s biocompatibility, low driving voltage, and high actuation strain make it particularly suited for advanced prosthetic devices, where precise and naturalistic movement is required, as well as for minimally invasive, injectable medical devices that can be deployed and activated in situ. As artificial muscles, the actuator system can be integrated into wearable exoskeletons and assistive devices to provide lightweight, flexible, and energy-efficient actuation for human motion support. Furthermore, the actuator system’s compatibility with flexible substrates enables integration into smart textiles and flexible displays, where it can provide responsive, shape-adaptive functionalities such as tactile feedback, dynamic surface modulation, or real-time display reconfiguration. In environmental control systems, the actuator system can be employed in adaptive windows with tunable transparency or dynamic ventilation systems that respond to environmental stimuli. Additionally, in microfluidic applications, particularly in lab-on-a-chip platforms, the actuator system enables precise, localized, and reversible fluid manipulation, such as valve actuation or pump control, thereby enhancing the functionality and autonomy of miniaturized diagnostic and analytical systems.

[0152] The present application discloses various embodiments of an actuator system having one or more ionic actuators. The ionic actuator of the present disclosure includes an electrolyte and a pair of electrodes, with each of the pair of electrodes being of a ternary electrode system. The electrolyte is a flexible film laterally disposed between the pair of electrodes. The ionic actuator may be described as having a thickness in a lateral orientation, the lateral orientation extending, in sequence, across one of the pair of electrodes, the electrolyte, and the other of the pair of electrodes. The lateral orientation may be defined relative to a longitudinal orientation that extends through the entire electrolyte without cutting across an interface between the electrolyte and any one of the pair of electrodes. The ionic actuator is deformable in response to a voltage applied across the pair of electrodes. The electrolyte may include Nafion and an ionic liquid. The ternary electrode system may include the ionic liquid. The ternary electrode system may include single-walled carbon nanotubes (SWCNTs). The ternary electrode systemmay include DMSO-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT PSS). The ternary electrode system may be configured with the SWCNTs and the PEDOT:PSS being respectively a core and a shell of a core-shell structure.

[0153] The actuator system may include a plurality of the ionic actuators in which a first ionic actuator of the plurality of ionic actuators and a second ionic actuator of the plurality of ionic actuators are coupled to one another longitudinally in a series to form a multi-segment actuator.

[0154] The electrolyte of the first ionic actuator and the electrolyte of the second ionic actuator may form a contiguous flexible film.

[0155] At least one of the electrodes of the first ionic actuator and the second ionic actuator may have a different thickness than the other

[0156] At least one of the first ionic actuator and the second ionic actuator may have a different length than the other.

[0157] According to some embodiments, the actuator system may further include a controller, in which the controller is configured to simultaneously apply a first voltage signal to the first ionic actuator and a second voltage signal to the second ionic actuator.

[0158] The actuator system may be configured to enable the following: in response to the first voltage signal having a same polarity as the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in a same direction, and in response to the first voltage signal having an opposite polarity to the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in opposing directions.

[0159] In response to the first voltage signal and the second voltage signal having a positive polarity, the first ionic actuator and the second ionic actuator may be configured to deform in a first direction, and in response to the first voltage signal and the second voltage signal having a negative polarity, the first ionic actuator and the second ionic actuator may be configured to deform in a second direction opposite to the first direction.

[0160] According to some embodiments, the actuator system may further include a controller, in which the controller is configured to apply a respective voltage signal to each of the plurality of the ionic actuators, wherein the plurality of the ionic actuators are configured to responsively defonn to form any one of the following configurations: a gripper, a hook, and a scraper.

[0161] The actuator system may further include a base, in which the plurality of the ionic actuator are coupled to the base, each of the plurality of the ionic actuators being orientedradially outward from a central axis of the base, and in which the plurality of the ionic actuators are spaced apart from one another at equal angular intervals around the central axis.

[0162] The electrodes of each of the plurality of the ionic actuators facing the central axis of the base may be electrically coupled to a common polarity of a voltage source.

[0163] The actuator system may further include a base, with which each of the plurality of the ionic actuators may be coupled along a longitudinal axis of the base.

[0164] The electrodes of each of the plurality of the ionic actuators oriented toward a common direction may be electrically coupled to a common polarity of a voltage source. Numerous other changes, substitutions, variations, and modifications may be ascertained by the skilled in the art and it is intended that the present application encompass all such changes, substitutions, variations, and modifications as falling within the scope of the appended claims.

Claims

CLAIMS1. An actuator system comprising: an ionic actuator including: a pair of electrodes, each of the pair of electrodes being of a ternary electrode system, and an electrolyte, the electrolyte being a flexible film laterally disposed between the pair of electrodes, wherein the ionic actuator is deformable in response to a voltage applied across the pair of electrodes, and wherein the electrolyte includes Nafion and an ionic liquid, and wherein the ternary electrode system includes: the ionic liquid; single-walled carbon nanotubes (SWCNTs); andDMSO-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOLPSS), the SWCNTs and the PEDOT:PSS being respectively a core and a shell of a core-shell structure.

2. The actuator system of claim 1, comprising a plurality of the ionic actuators, wherein a first ionic actuator of the plurality of ionic actuators and a second ionic actuator of the plurality of ionic actuators are coupled to one another longitudinally in a series to form a multi-segment actuator.

3. The actuator system of claim 2, wherein the electrolyte of the first ionic actuator and the electrolyte of the second ionic actuator form a contiguous flexible film.

4. The actuator system of any one of claims 2 to 3, wherein at least one of the electrodes of the first ionic actuator and the second ionic actuator has a different thickness than the other.

5. The actuator system of any one of claims 2 to 4, wherein at least one of the first ionic actuator and the second ionic actuator has a different length than the other6. The actuator system of any one of claims 3 to 5, further comprising a controller, wherein the controller is configured to simultaneously apply a first voltage signal to the first ionic actuator and a second voltage signal to the second ionic actuator.

7. The actuator system of claim 6, wherein in response to the first voltage signal having a same polarity as the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in a same direction, and in response to the first voltage signal having an opposite polarity to the second voltage signal, the first ionic actuator and the second ionic actuator are configured to deform in opposing directions.

8. The actuator system of claim 6, wherein in response to the first voltage signal and the second voltage signal having a positive polarity, the first ionic actuator and the second ionic actuator are configured to deform in a first direction, and in response to the first voltage signal and the second voltage signal having a negative polarity, the first ionic actuator and the second ionic actuator are configured to deform in a second direction opposite to the first direction.

9. The actuator system of any one of claims 3 to 5, further comprising a controller, wherein the controller is configured to apply a respective voltage signal to each of the plurality of the ionic actuators, wherein the plurality of the ionic actuators are configured to responsively deform to form any one of the following configurations: a gripper, a hook, and a scraper.

10. The actuator system of any one of claims 2 to 5, further comprising a base, wherein the plurality of the ionic actuator are coupled to the base, each of the plurality of the ionic actuators being oriented radially outward from a central axis of the base, and wherein the plurality of the ionic actuators are spaced apart from one another at equal angular intervals around the central axis.11 . The actuator system of claim 10, wherein the electrodes of each of the plurality of the ionic actuators facing the central axis of the base are electrically coupled to a common polarity of a voltage source.

12. The actuator system of any one of claims 2 to 5, further comprising a base, wherein each of the plurality of the ionic actuators is coupled along a longitudinal axis of the base.

13. The actuator system of claim 12, wherein the electrodes of each of the plurality of the ionic actuators oriented toward a common direction are electrically coupled to a common polarity of a voltage source.

Images