Ion-exchange Polymer Metal Composite Research Articles

Preparation and Electrochemical Performance Analysis of Flexible Ionic Polymers by Freeze-Drying Technology

With the development of bionics and marine science, a new artificial muscle material, IPMC (ion-exchange polymer metal composite), has attracted significant attention. However, the performance issues, as well as problems associated with the preparation of IPMC, have limited its development. In this study, we use the freeze-drying technique, successfully creating a new type of enhanced carbon nanotube IPMC material. Moreover, we also use the method of cyclic voltammetry, ac impedance, and the constant current charge and discharge method to analyze and evaluate the multiwalled carbon nanotube (MWCNT)-reinforced IPMC produced by freeze-drying technology. Freeze-dried IPMC has a higher moisture content, which is 1.58 times higher than that of ordinary IPMC. The pore and multiwalled carbon nanotube (MWCNT) in the ion exchange membrane are distributed more homogeneously. The technology prepared by IPMC has superior electrical performance. Under a 2 v scanning interval and a scanning speed of 50 mV/s, its specific capacitance can reach 247.5335 mF/cm−2, which is 24 times that of normal IPMC. Under the same conditions, its conductivity can reach 0.29391 mS/cm, far higher than that of ordinary IPMC. Furthermore, the preparation process is also safer. This method provides a new strategy for the future preparation and usage of IPMC.

Hydrophilic Poly(vinylidene Fluoride) Film with Enhanced Inner Channels for Both Water- and Ionic Liquid-Driven Ion-Exchange Polymer Metal Composite Actuators.

This study presents a novel and facile strategy to fabricate a hydrophilic poly(vinylidene fluoride) (PVDF) electrolyte film with enhanced inner channels for a high-performance and cost-effective ion-exchange polymer metal composite (IPMC) actuator. The resultant PVDF composite film is composed of hierarchical micro/nanoscale structures: well-defined polymer grains with a diameter of ∼20 μm and much finer particles with a diameter of ∼390 nm, producing three-dimensional interconnected, hierarchical inner channels to facilitate ion migration of IPMC. Interestingly, the electrolyte matrix film has a high porosity of 15.8% and yields a high water uptake of 44.2% and an ionic liquid (IL, [EMIm]·[BF4]) uptake of 38.1% to make both water-driven and IL-driven IPMC actuators because of the introduction of polar polyvinyl pyrrolidone. Compared to the conventional PVDF/IL-based IPMC, both water-driven and IL-driven PVDF-based IPMCs exhibit high ion migration rates, thus effectively improving the actuation frequency and producing remarkably higher levels of actuation force and displacement. Specifically, the force outputs are increased by 13.4 and 3.0 folds, and the displacement outputs are increased by 2.2 and 1.9 folds. Using an identical electrolyte matrix, water-driven IPMC exhibits stronger electromechanical performance, benefiting to make IPMC actuator with high levels of force and power outputs, whereas IL-driven IPMC exhibits a more stable electromechanical performance, benefiting to make long lifetime IPMC actuator in air. Thus, the resultant IPMCs are promising in the design of artificial muscles with tunable electromechanical performance for flexible actuators or displacement/vibration sensors at low cost.

Polymer actuators of fluorene derivatives with enhanced inner channels and mechanical performance

A novel ion-exchange polymer-metal composite (IPMC) actuator is fabricated by sandwiching sulfonated fluorene blocked polysulfone (SDPF-b-PSU) between two Pt nanograin sheets. With increased concentration of chlorosulfonic acid, the SDPF-b-PSU film with more sulfonic groups exhibits strong ion exchange capacity, high Li+ ion conductivity, and ordered phase separation, which may contain an increased number of cations and possess larger and better interconnected inner channels for ion migration, thus providing the power to produce large force and power outputs. The SDPF-b-PSU film also exhibits enhanced mechanical performance and water uptake when compared to the pure Nafion film, providing a strong, hydrated matrix to support IPMC functions. At the driving voltage of 4V, the SDPF-b-PSU actuator exhibits a strong force output which is 11 folds higher than that of the pure Nafion actuator.

Reverse adhesion of a gecko-inspired synthetic adhesive switched by an ion-exchange polymer-metal composite actuator.

Inspired by how geckos abduct, rotate, and adduct their setal foot toes to adhere to different surfaces, we have developed an artificial muscle material called ion-exchange polymer-metal composite (IPMC), which, as a synthetic adhesive, is capable of changing its adhesion properties. The synthetic adhesive was cast from a Si template through a sticky colloid precursor of poly(methylvinylsiloxane) (PMVS). The PMVS array of setal micropillars had a high density of pillars (3.8 × 10(3) pillars/mm(2)) with a mean diameter of 3 μm and a pore thickness of 10 μm. A graphene oxide monolayer containing Ag globular nanoparticles (GO/Ag NPs) with diameters of 5-30 nm was fabricated and doped in an ion-exchanging Nafion membrane to improve its carrier transfer, water-saving, and ion-exchange capabilities, which thus enhanced the electromechanical response of IPMC. After being attached to PMVS micropillars, IPMC was actuated by square wave inputs at 1.0, 1.5, or 2.0 V to bend back and forth, driving the micropillars to actively grip or release the surface. To determine the adhesion of the micropillars, the normal adsorption and desorption forces were measured as the IPMC drives the setal micropillars to grip and release, respectively. Adhesion results demonstrated that the normal adsorption forces were 5.54-, 14.20-, and 23.13-fold higher than the normal desorption forces under 1.0, 1.5, or 2.0 V, respectively. In addition, shear adhesion or friction increased by 98, 219, and 245%, respectively. Our new technique provides advanced design strategies for reversible gecko-inspired synthetic adhesives, which might be used for spiderman-like wall-climbing devices with unprecedented performance.

Study on Micro-Force Sensor of Cantilever Structure Based on IPMC

IPMC (Ion-exchange polymer metal composite) is a kind of novel artificial intelligent materials. It has a lot of good properties, such as light weight, good flexibility, easily cut in any size and shape, and can be used as both an actuator and sensor. A micro-force sensor based on the theory model of cantilever beam structure of IPMC is built up, which is applied to measure probe force during the micro operations under the environment of the cell injection.

Preparation and self‐assembly of polyaniline nanorods and their application as electroactive actuators

AbstractTo improve the performance of ion‐exchange polymer–metal composite (IPMC) actuators, an electrical pathway material for enhancing the surface adhesion between the membrane and the metal electrodes of the IPMC was studied. As an efficient electrical pathway material, polyaniline nanorods (PANI‐NRs) doped with p‐toluene sulfonic acid (TSA) were synthesized with a template‐free method. The factors affecting polyaniline morphology were studied with various dopant concentrations and oxidant feeding rates. Highly conductive PANI‐NRs were formed when they were synthesized with ammonium persulfate at a 5.0 mL/min oxidant feeding rate and doped with 0.125M TSA. The conductivity of the PANI‐NRs was 1.15 × 10−1 S/cm, and their diameters and lengths were 120–180 nm and 0.6–2 μm, respectively. To apply the membrane as an actuator, perfluorosulfonated ionomer (Nafion)/PANI‐NR blends were prepared by solution blending and casting. The actuating ability of the three‐layered membrane consisting of Nafion/PANI‐NR blends was then examined and compared with that of Nafion only. The actuating ability of the IPMC was improved when Nafion/PANI‐NRs were used as electrical pathways. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A highly porous nafion membrane templated from polyoxometalates-based supramolecule composite for ion-exchange polymer-metal composite actuator

This paper reports a new technique for fabricating a highly porous hybrid SiO2/Nafion membrane, from which a high electromechanical performance ion-exchange polymer-metal composite (IPMC) actuator is achieved. This technique uses polyoxometalate (POM)-based supramolecule composite carried by amorphous SiO2 particles to form a hybrid membrane with the polar Nafion ionomer. The resultant composite (POM-Nafion) is then incubated and degraded in a base solution, forming a porous membrane. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) were used to monitor the degradation process. ATR-FTIR results demonstrated that the POM-based composite was removed while SiO2 remained in the porous membrane after degradation. SEM images showed that there were a great quantity of channels with sizes of 0.4–1.4 μm and pores with sizes of 300–700 nm in the newly-formed porous Si-Nafion membrane. With the same Nafion content, the porous Si-Nafion membrane and self-casting Nafion membrane were both made into IPMC actuators. A laser displacement sensor, a force sensor and a high speed camera were assembled into a measurement system to evaluate the performance of the IPMC actuator. Results showed that the maximum blocking forces from the Si-Nafion membrane actuator were 3.78 g for 2.5 V driving voltage and 2.39 g for 1.5 V, which increase by 2.97 and 4.19 times, respectively, when compared to the self-casting Nafion membrane actuator. The maximum displacement outputs were 7.2 mm for 2.5 V driving voltage and 5.9 mm for 1.5 V. Compared to the self-casting Nafion membrane actuator, these outputs increased by 4.8 and 9.7 times, respectively. When actuated in the air, the Si-Nafion membrane actuator exhibited stable working time of 480 s and 710 s for the voltages of 2.5 V and 1.5 V, respectively. Compared to the self-casting Nafion membrane actuator, these data increased by 4.36 and 2.22 times, respectively.

Hybrids perfluorosulfonic acid ionomer and silicon oxide membrane for application in ion-exchange polymer-metal composite actuators

This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid membrane is formed. Measurements of mechanical properties reveal that elastic modulus and hardness of the hybrid membrane are about 2 times compared to a commercial PFSA membrane. Scanning electron microscopy (SEM) results show that the hybrid membrane has a high porosity. Inside the membrane pores, there exists a great quantity of micro scale channels in the range of 100–300 nm. After fabrication of IPMC actuator, an electric current sensor, a force sensor, and a high speed camera are assembled and used to evaluate IPMC performance. It is shown that, compared to an IPMC actuator made from a commercial membrane, the electromechanical performance of the new actuator increases 6–8 times; when it is actuated in air, its stable non-water working time is prolonged for 6–7 times.

Soft actuator based on ion-exchange polymer-metal composite

Ion-exchange polymer-metal composite (IPMC) is a new electroactive material. It has large deformation and high force weight ratio in the presence of low voltage (<1.5 V). In this study a soft actuator known as artificial muscle based on IPMC was prepared. The IPMC actuator is composed of a perfluorinated ion-exchange membrane and platinum plated on both sides of the membrane by chemical means. Experiences and some key points are introduced in preparation of the IPMC. Electromechanical behaviors of the actuator are investigated. Factors related to the actuator performance are discussed.

Experimental Analysis of Current and Deformation of Ion-exchange Polymer Metal Composite Actuators

In this paper we describe the experimental analysis of a novel ion-exchange polymer metal composite (IPMC) actuator under large external voltage. The experimental analysis is supplemented with a coupled thermodynamic model, which includes mass transport across the thickness of the polymer actuator, chemical reactions at boundaries, and deformation as a function of the solvent (water) distribution. In this paper, the case of large electrode potentials (over 1.2 V) has been analyzed experimentally and theoretically. At these voltage levels, electrochemical reactions take place at both electrodes. These are used in the framework of overpotential theory to develop boundary conditions for the water transport in the bulk of polymer. The model is then simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. Among these species, water molecules are considered to be the dominant species responsible for the deformation of the IPMC actuators. Experiments conducted at different initial water contents are described and discussed in the context of the proposed deformation mechanism. Comparison of numerical simulations with experimental data shows good agreement.

Analysis of water and proton fluxes in ion-exchange polymer–metal composite (IPMC) actuators subjected to large external potentials

An analysis is conducted of a novel ion-exchange polymer–metal composite (IPMC) actuator under large external voltage. The model is simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. The proposed coupled model includes mass transport in the membrane, chemical reactions at boundaries, and deformation as a function of a concentration of water molecules. The electrochemical process occurring at both electrodes are the boundary conditions analyzed during the deformation of the actuator in a regime of large voltage (over 1.2 V). This coupled model successfully captures the stress relaxation phenomenon due to water redistribution governed by diffusion. The fabrication process and testing apparatus are also described. Comparison of simulations and experimental data showed good agreement.

Water uptake and migration effects of electroactive ion-exchange polymer metal composite (IPMC) actuator

The low actuating voltage and quick bending responses of ion-exchange polymer metal composite (IPMC) are considered very attractive for the construction of various types of actuators and sensors. The principle of IPMC actuation under electric field has been believed to be the ion cluster flux and electro-osmotic drag of water from the anode to cathode direction through the hydrophilic channels in the perfluorinated sulfonic acid polymer chains. In this study, the effect of water content residing in the perfluorinated polymer was investigated by electrochemical and thermal experiments as well as hydraulic mechanical modeling. The water residing in the IPMC actuator seemed to exist as free water and bound water, each corresponding to interstitial and hydrogen-bonded water molecules. Using the classical lamination theory (CLT), a modeling methodology was developed to predict the deformation, bending moment, and residual stress distribution of the anisotropic IPMC thin-plate actuators. In this modeling methodology, the internal stress evolved by the unsymmetric distribution of water in the IPMC was quantitatively calculated and subsequently the bending moment and the curvature were estimated for the IPMC actuator.

Investigations on actuation characteristics of IPMC artificial muscle actuator

Electromechanical response characteristics of ion-exchange polymer metal composite (IPMC), known as a material for artificial muscle actuators, varies extremely depending on the driving method. With respect to the power management the driving method is one of the important considerations though it has not been investigated sufficiently up to now. Its efficiency is critical to enhance the performance of an IPMC system, especially self-contained one. The primary objective of this paper is to investigate electromechanical response characteristics of the IPMC actuator according to driving methods. We begin with developing an equivalent electrical circuit model for the IPMC actuator using experimental data. Based on this model, discuss how the waveforms and frequencies of driving inputs have effect on the characteristic features of the IPMC actuator. Typically square, triangular and harmonic waves are applied as the driving waveform of the IPMC actuator. By employing Fourier techniques, the responses of the IPMC actuator on each input waveform are mathematically analyzed. From this study, we conclude that large consumption of current during actuation is caused by the high frequency components of the driving waveforms because the IPMC actuator has the characteristics of damped high pass filter. A desirable method of driving the IPMC actuator is proposed and its validity is experimentally confirmed.