Ionic Polymer Metal Composite Research Articles

Effect of doping polyethylene oxide on the properties of Nafion-IPMC actuators

In order to improve the actuation stability and non-water working time (NWT) of ionic polymer-metal composites (IPMCs) in the air, polyethylene oxide (PEO) with superior water retention ability was firstly blended into the Nafion matrix to enhance the water uptake capacity of the corresponding IPMCs. The influences of molecular weight of PEO on the water uptake ration, ion exchange ability and micromorphology of PEO/Nafion membranes, and the electromechanical properties of IPMCs were investigated in detail. The results showed that the water uptake ration of the Nafion membranes and the working stability of the IPMCs in the air were greatly improved. The IPMC with 200k molecular weight of PEO exhibited the optimal deformation properties, the highest volumetric work density, and a prolonged NWT. In addition, the high content substitution of Nafion by PEO can reduce the preparation cost of IPMC to some extent. Thus, we hope that the developed PEO/Nafion-IPMCs can be promising candidates for actuation applications in the fields of bionic robotics, space explorations, and medical devices.

On Maxwell stress and its relationship with the dielectric constant in the actuation of ionic polymer metal composites

Ionic polymer metal composites (IPMCs) are unique electroactive polymers that show promise as actuators in soft robotics and biomedical applications. The modeling and numerical simulation of the behavior of these materials are significantly complicated by the nature of the underlying electrochemical phenomena, which occur in nanometer-thick layers in the proximity of the electrodes. Hence, the dielectric constant of IPMCs is often rescaled to help numerically resolve the electric double layers. However, the effect of such a rescaling on IPMC actuation has never been systematically assessed. Motivated by recent efforts on the effect of the rescaling on Maxwell stress, we put forward a physically based analysis of the role of dielectric constant on IPMC actuation. We demonstrate that an increase of the dielectric constant decreases the magnitude of the electric field during actuation, due to the widening of the electric double layers. The decrease in the electric field intensity perfectly balances the increase of the dielectric constant scaling Maxwell stress, such that Maxwell stress is independent of the IPMC dielectric constant. The bending moment generated by Maxwell stress increases with the dielectric constant, since the thickness of the electric double layers where Maxwell stress is relevant is larger. However, the same scaling is common to all the bending moments associated with the electrochemistry, so that the relative importance of each term on IPMC actuation does not depend on the dielectric constant. This study contributes an important analysis that can support feasible and faithful numerical implementations of theories on IPMC mechanics and electrochemistry.

Preparation and Modification Technology Analysis of Ionic Polymer-Metal Composites (IPMCs).

As a new type of flexible smart material, ionic polymer-metal composite (IPMC) has the advantages of being lightweight and having fast responses, good flexibility, and large deformation ranges. However, IPMC has the disadvantages of a small driving force and short lifespan. Based on this, this paper firstly analyzes the driving mechanism of IPMC. Then, it focuses on the current preparation technology of IPMC from the aspects of electroless plating and mechanical plating. The advantages and disadvantages of various preparation methods are analyzed. Due to the special driving mechanism of IPMC, there is a problem of short non-aqueous working time. Therefore, the modification research of IPMC is reviewed from the aspects of the basement membrane, working medium, and electrode materials. Finally, the current challenges and future development prospects of IPMC are discussed.

Platinum-coated silicotungstic acid-sulfonated polyvinyl alcohol-polyaniline based hybrid ionic polymer metal composite membrane for bending actuation applications

An electro-stimulus-responsive bending actuator was developed by synthesizing a non-perfluorinated membrane based on silicotungstic acid (SA), sulfonated polyvinyl alcohol (SPVA), and polyaniline (PANI). The membrane was developed via solution casting method. The dry membrane SA/SPVA showed a sufficient ion-exchange potential of 1.6 meq g−1 dry film. The absorption capacity of the membrane after almost 6 h of immersion was found to be ca. 245% at 45 °C. The electroless plating with Pt metal was carried out on both sides of the membrane that delivered an excellent proton conductivity of 1.9 × 10−3 S cm−1. Moreover, the scanning electron microscopy (SEM) was conducted to reflect the smooth and consistent surface that can prevent water loss. The water loss capacity of the membrane was found to be ca. 33% at 6 V for 16 min. These results suggest a good actuation output of the ionic polymer metal composite (IPMC) membrane once the electrical potential is applied. The electromechanical characterization displayed a maximum tip displacement of 32 mm at 3 V. A microgripping device based on multifigure IPMC membrane may be developed showing a good potential in micro-robotics.

An Antifatigue Liquid Metal Composite Electrode Ionic Polymer-Metal Composite Artificial Muscle with Excellent Electromechanical Properties.

Ionic polymer-metal composites (IPMC), one of the most popular materials in the field of artificial muscle research, have attracted much attention because of their high flexibility, low drive voltage (<10 V), high force density, large deformation, and so forth. However, the results show that the serious electrode fatigue crack and water loss of traditional IPMC greatly decrease its fatigue life and limit the practical application. In this study, we developed a novel liquid metal composite electrode. A layer of eutectic gallium-indium alloy (EGaIn) liquid metal was applied to the surface of the platinum electrode of the IPMC using a mask. Because of the good self-healing performance of the liquid metal, it is expected to solve the above problems of resistance increase and water loss caused by cracks. It turns out that the prepared EGaIn/Pt-IPMC exhibits a driving force up to 120 mN and maximum fatigue life of about 25,000 s at a driving voltage of 3 V. Compared with the best work reported, the fatigue strength of EGaIn/Pt-IPMC was increased by about 210%, and the maximum driving force of EGaIn/Pt-IPMC prepared by a single-layer basement membrane was between the IPMC prepared by 4-6 layer basement membrane. The electromechanical properties were significantly improved, and it is expected to realize a series of bionic applications.

Velocity control and dynamic modeling of biomimetic underwater propulsor actuated by ionic polymer metal composite

Velocity control and dynamic modeling of biomimetic underwater propulsor actuated by ionic polymer metal composite

Enhanced performance of IPMC actuator based on macroporous multilayer MCNTs/Nafion polymer

The structure and additives of ionic polymer-metal composite (IPMC) are important factors affecting its performance. Macropores and multi-walled carbon nanotubes (MCNTs) were introduced into multilayered IPMC actuators by an orderly mesh of silica spheres to enhance the IPMC actuator’s performance. The mechanical of membranes is improved a lot by the uniform combination of MCNTs and macroporous multilayered MCNTs/Nafion membrane. In particular, Young’s modulus for the macroporous multilayered MCNTs/Nafion membrane increases by 3.3 folds (from 262.6 MPa to 858.1 MPa), and the hardness increases by 4.4 folds (from 28.2 MPa to 123.9 MPa). Electromechanical results of the IPMC actuator increase respectively by 1.41 (33.5 mm) and 2.2 (19.2 mN) folds in the air under a DC voltage of 5 V, compared with typical IPMC actuators.

Purcell's three-link microswimmer based on IPMC: Simulations in COMSOL Multiphysics

One of the few possible mechanisms for self-propulsion at low Reynolds number (henceforth, Re) is undulations of an elastic tail, as proposed in the classical work of Purcell in 1977. This paper studies this effect by investigating a variant of Purcells three-link swimmer model where the lateral links are flexible, specifically fabricated by ionic polymer metal composite (IPMC), by means of simulations in COMSOL Multiphysics. Firstly, a model of the material is developed in COMSOL and simulated in comparison with results that can be found in the literature. The proposed model presents some benefits against other existing models: 1) it allows actuator displacement, so it can be integrated in the model of a mobile robot; 2) it satisfies Euler-Bernoulli theorem; and 3) it incorporates the interaction of the actuator with a fluid in which the robot is immersed. Based on this model, a Purcell's three-link microswimmer is built whose lateral links are of IPMC within a fluid under low Re conditions. The displacement of the robot is analyzed for one of the classical primitives of motion, namely, the circular primitive. The results demonstrate that the swimmer is able to perform a non-reciprocal motion and, consequently, propel itself within the fluid.

Complex of Miniature Bionic Robotic Systems

The developed and implemented complex of miniature bionic robotic systems is presented, including swimming and walking miniature biosimilar robots with low-voltage energy-efficient motion drives based on ionic polymer-metal composites; miniature autonomous robotized probes with a vibration propulsor for moving through small-diameter pipes and transmitting a video signal over a two-frequency radio channel; an ultralight zoomorphic flying platform with a movable wing — a robot ornithopter "Hummingbird".

Formation and characterization of Pt-Cu-IPMC with high specific surface area and dendritic electrode

ABSTRACT Ionic polymer–metal composite (IPMC) is a kind of electroactive intelligent material. The dendritically interfacial electrodes (DIEs) is very important to the performance of IPMC. Herein, the copper–platinum composite electrode (Pt-Cu-IPMC) with a high specific area DIEs was prepared by combining impregnation-reduction plating platinum (IRP-Pt), autocatalytic plating platinum (ACP-Pt) and chemical reduction plating copper (CRP-Cu). The effects of DIEs and the cycles of ACP-Pt have been systematically investigated on the electrode’s thickness, micro-morphology and electromechanical response characteristics of all samples. Importantly, when the cycles of ACP-Pt increases, the platinum and copper particles in the ionomer membrane are highly dispersed. For example, when the cycles of ACP-Pt is 4, the penetration depth of the DIEs reaches 31.98 µm. Thus, copper and platinum dendrites were clearly observed in the samples. Combined with the analysis of the strain energy density, it showed that the presence of DIEs has some impact on the driving performance of the IPMC, the tip displacement, and blocking force of 67.27 mm and 27.21 mN have been achieved in the Pt-Cu-IPMC after three cycles of ACP-Pt.

Interface electrode and enhanced actuation performance of SiO2-GO/PFSA-based IPMC soft actuators

In this study, ‘three-dimensional structure’ nanohybrid particle (SiO2-GO) were synthesized by in situ hydrolysis and composited with perfluorosulfonic acid (PFSA) to increase the water uptake (WUP) and ion exchange capacity (IEC) of the cast membranes. Ionic polymer metal composite (IPMC) soft actuators were fabricated based on the cast pure PFSA, GO/PFSA and SiO2-GO/PFSA membranes. The morphology and properties of IPMC were researched, and the relationship between them was analyzed in this article. The mechanism of SiO2-GO particles enhancing the properties of IPMC was revealed. The effects of incorporating GO and SiO2-GO on IPMC actuators were analyzed using physicochemical and electromechanical measurements comparing with the corresponding behavior of pure PFSA-based IPMC actuators. Morphology of IPMC showed effective incorporation of GO and SiO2-GO and clarified the dependency of Pt interface electrode on the SiO2-GO content of the PFSA membranes. The addition of SiO2-GO increased dramatically the WUP and IEC of the PFSA membranes and autuation performance of the IPMC actuators. The IPMC with 1 wt% SiO2-GO showed superb properties. The displacement of 1 wt% SiO2-GO under 3 V AC voltage reached 28.4 mm, which is 3.2 times higher than that of the pure PFSA. The maximum displacement under DC voltage reached 44.7 mm (5.5 V), and the blocking force reached 43.2 mN (5 V), which increased respectively 1.1 times and two times.

Modeling the actuation of curved ionic polymer metal composites

An ionic polymer metal composites (IPMC) is a soft actuator that consists of an ionomer membrane, neutralized by mobile counterions and plated by metal electrodes. Despite their early promise in robotics, medical devices, and microsystem technologies, widespread application of IPMC actuators is far from being reached. Recent advancements in additive manufacturing technologies have the potential to expand the reach of IPMCs by affording the realization of complex, design-specific geometries that were impossible to attain with standard manufacturing techniques. For this potential to be attained, it is critical to establish physically-based models that could inform 3D printing, beyond the flat, thin, non-tapered geometries that have been the object of investigation for almost three decades. Here, we bridge this gap by presenting an analytical framework to study actuation of a double-clamped IPMC arch under an applied voltage. We adopt a thermodynamically the consistent continuum model to describe the coupled electrochemo-mechanical phenomena taking place within the IPMC. We establish an analytical solution for the electrochemistry using the method of matched asymptotic expansions, which is, in turn, utilized to compute osmotic pressure and Maxwell stress. The mechanical response of the IPMC arch is modeled as a plane strain problem with an induced state of eigenstress, which is solved with the use of a smooth Airy function. The accuracy of our analytical solution is validated through finite element simulations. Through a parametric analysis, we investigate the effect of curvature on the deformation and the reaction forces exerted by the clamps. The proposed analytical framework offers new insight into the response of curved IPMCs, in which progress on 3D printing should be grounded.

Frequency Reconfigurable Smart Antenna With Integrated Electroactive Polymer for Far-Field Communication

For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a radio frequency identification (RFID) tag antenna for achieving frequency reconfiguration in the ultrahigh-frequency (UHF) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a two-layer-crenelated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the two-layer-crenelated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.

Approximate field measures for ionic polymer-metal composite materials and a simplified order-of-magnitude actuator model

As the field of soft robotics grows and new applications for this technology are discovered, the use of simplified models for the soft actuators found in these devices will be critical. In this study we explore arguments based on the magnitude of field gradients that arise in the ionic polymer-metal composite (IPMC) under large applied voltages and their use for approximating measures of the fields inside the polymer. Using the order-of-magnitude based arguments provides exceptional results for quantifying the field measures of maximum ionic concentration and electric potential within the bulk of the polymer. These measures are leveraged to reconstruct the fields themselves in such a way that the internal bending moments generated inside the actuator may be approximated. With the internal moments, a simplified kinematic model may be used to formulate the steady-state actuator response of the IPMC. This actuator model shows a great deal of accuracy as compared to a full multiphysics model, and we discuss the prospects for future development of this model to account for dynamic actuation.

Design and test of wirelessly powered IPMC artificial muscle for aquatic ecosystem health applications

Aquatic environments and water resources face a variety of risks from numerous sources of pollution. In this paper, we propose a preliminary mechanism for realizing robotic technology practically and cost-effectively for monitoring these pollutions. The presented system is a small robotic fish propelled by a beam of ionic polymer-metal composite (IPMC) artificial muscle that imitates the motion of a small Scorpis Georgiana fish. One of the superiorities of the proposed model is the IPMC actuation mechanism powered by a battery that is charged wirelessly from a solar panel source. This approach enables us to produce a robotic fish that works ceaselessly without being forced to carry the solar panel load. Moreover, we present a method to control the flapping motion of a robotic fish by taking advantage of a tiny Wi-Fi module that yields more working range, bulky data sending, low power consumption, simple programing, and convenient communication for creating a network with other similar robots. All these beneficial characteristics make the proposed structure a promising candidate for detecting pollution on the surface of aquatic environments and sending/recording necessary data in collaboration with desirable sensors. Theoretical considerations support experimental results reported in the paper.

Energy-Based Modeling and Hamiltonian LQG Control of a Flexible Beam Actuated by IPMC Actuators

The control of a flexible beam using ionic polymer metal composites (IPMCs) is investigated in this paper. The mechanical flexible dynamics are modelled as a Timoshenko beam. The electric dynamics of the IPMCs are considered in the model. The port-Hamiltonian framework is used to propose an interconnected control model of the mechanical flexible beam and IPMC actuator. Furthermore, a passive and Hamiltonian structure-preserving linear quadratic Gaussian (LQG) controller is used to achieve the desired configuration of the system, and the asymptotic stability of the closed-loop system is shown using damping injection. An experimental setup is built using a flexible beam actuated by two IPMC patches to validate the proposed model and show the performance of the proposed control law.

Actuation characteristics and experimental identification of IPMC actuator for underwater biomimetic robotic application

Traditionally underwater robotic devices are driven with the help of hydraulic systems or motors. However, with the current advancement in technology and inclination towards smart structures and miniature designs, various new actuators are being utilized. Ionic polymer-metal composites (IPMC) are the smart materials that come under the category of Ionic Electro-active polymers are considered as the best suitable soft actuator material for robotic devices in the field of military, aerospace and medical applications. The soft actuator’s actuation characteristics are explored in an underwater environment using data acquisition from LabView and laser vibrometer for providing the input voltage to the IPMC and to measure the tip deflection of IPMC actuator respectively. Proportional, Integral and Derivative (PID) closed-loop response using Ziegler Nichols tuning method for getting controller gains is presented through MATLAB/Simulink simulation for better actuation based on desired output response of the actuated IPMC. An evolutionary optimization technique, Particle swarm optimization (PSO) technique has been used to tune the PID controller gains to get a snappier response. The results suggested that the IPMC actuator achieved the desired actuation response of 4 mm under the applied sinusoidal voltage. Also, it is concluded that the proposed experimental model can help researchers in getting proper actuation response from different RC characteristics of IPMC under electric potential in an underwater environment that can be used for application in the underwater biomimetic robotic devices.

Fabrication of a multilayered SGO/macroporous Nafion-based IPMC with enhanced actuation performance

Ionic polymer-metal composites (IPMCs) composed of Nafion film and platinum deposited on both faces have gained much attention in biomedical engineering as actuators because it can show large bending motion under an electric field. This study focuses on the design of a multilayered IPMC actuator based on sulfonated graphene oxide (SGO) modified macroporous Nafion film. The Nafion film is firstly fabricated via templating technique by using silica spheres as template and SGO as a conductive agent dispersed in Nafion film. Then, Pt nanoparticles are deposited on both faces of the as-prepared Nafion film to fabricate the actuator (denoted as IPMC-SGO-M). In the IPMC-SGO-M, macropores and SGO co-exist in the Nafion film, which can effectively enhance the rapid transport of ions and electrons. In addition, small Pt nanoparticles are uniformly dispersed on the surface of the Nafion film, which can improve the water-uptake capability and charge redistribution between two layers of electrode regions. As a result, the tip displacements of the IPMC-SGO-M are 1.7-fold and 1.9-fold higher than that of the IPMC based on macroporous Nafion film (IPMC-M) under 6.2 and 6.6 V, respectively. The blocking forces of the IPMC-SGO-M are about 2.6-fold and 2.3-fold higher than that of IPMC-M under 6.2 and 6.6 V, respectively.

Performance Enhancement of Ionic Polymer-Metal Composite Actuators with Polyethylene Oxide.

Current ionic polymer-metal composite (IPMC) always proves inadequate in terms of large attenuation and short working time in air due to water leakage. To address this problem, a feasible and effective solution was proposed in this study to enhance IPMC performance operating in air by doping polyethylene oxide (PEO) with superior water retention capacity into Nafion membrane. The investigation of physical characteristics of membranes blended with varying PEO contents revealed that PEO/Nafion membrane with 20 wt% PEO exhibited a homogeneous internal structure and a high water uptake ratio. At the same time, influences of PEO contents on electromechanical properties of IPMCs were studied, showing that the IPMCs with 20 wt% PEO presented the largest peak-to-peak displacement, the highest volumetric work density, and prolonged stable working time. It was demonstrated that doping PEO reinforced electromechanical performances and restrained displacement attenuation of the resultant IPMC.

Characterizing the transduction behavior of ionic polymer-metal composite actuators and sensors via dimensional analysis

Ionic polymer-metal composites (IPMCs) are functional smart materials that exhibit both electromechanical and mechanoelectrical transduction properties, and the physical phenomenon underlying the transduction mechanisms have been studied across the literature extensively. Here we use a new modeling framework to conduct the most comprehensive dimensional analysis of IPMC transduction phenomena, characterizing the IPMC actuator displacement, actuator blocking force, short-circuit sensing current, and open-circuit sensing voltage under static and dynamic loading. The information obtained in this analysis is used to construct nonlinear regression models for the transduction response as univariant and multivariant functions. Automatic differentiation techniques are leveraged to linearize the nonlinear regression models in the vicinity of a typical IPMC description and derive the sensitivity of the transduction response with respect to the driving independent variables. Further, the multiphysics model is validated using experimental data collected for the dynamic IPMC actuator and voltage sensor. With data collected from physical samples of IPMC materials in-lab, the regression models developed under the new computational framework are verified.