Ionic Polymer Metal Composite Transducers Research Articles

A comprehensive survey of ionic polymer metal composite transducers: preparation, performance optimization and applications

The past decade has witnessed an emerging and fast-growing field on mechanically soft systems, ranging from soft materials (e.g. hydrogels) to soft devices (e.g. flexible electronics), and to soft functional systems (e.g. soft robotics). It is envisioned that soft systems will continue to thrive in the coming decades in academia and industrial communities. The launch of Soft Science is to provide the first dedicated platform for publishing research findings and to share the knowledge among the communities.

Physics-based modeling of mechano-electric transduction of tube-shaped ionic polymer-metal composite

In this study, tube-shaped ionic polymer-metal composite (IPMC) mechanoelectrical transducers have been examined through simulation and experimental investigation for use as multi-directional sensor devices. It should be noted that cation migration simulations provide keen insight into the differences in actuation and sensing phenomena in IPMC transducers. COMSOL Multiphysics 4.3b is used to achieve 3D time-based finite element simulations, including all relevant physics. A physics-based model is proposed to simulate mechanoelectrical transduction of 3D shaped IPMCs. Configuration of interest is a tube-shaped IPMC with multi-directional transducer capabilities. Also, the fabricated IPMCs have an outer diameter of 1 mm and a length of 20–25 mm. Multi-directional sensing results are presented. The cation rise in a very small (roughly 10 micrometers) sub-surface layer near the electrodes is several orders of magnitude larger in case of actuation than in case of sensing. Furthermore, the signal produced from sensing is of opposite charge direction as that provided as input for actuation to achieve the same displacement. However, cation rise is in the same direction, indicating anion concentration change as the primary effect in sensing. The proposed model is independent of general geometry and can be readily applied to IPMC sensors of other complex 3D shapes.

Bio-applications of ionic polymer metal composite transducers

Traditional robotic actuators have advanced performance which in some aspects can surpass that of humans, however they are lacking when it comes to developing devices which are capable of operating together with humans. Bio-inspired transducers, for example ionic polymer metal composites (IPMC), which have similar properties to human tissue and muscle, demonstrate much future promise as candidates for replacing traditional robotic actuators in medical robotics applications. This paper outlines four biomedical robotics applications, an IPMC stepper motor, an assistive glove exoskeleton/prosthetic hand, a surgical robotic tool and a micromanipulation system. These applications have been developed using mechanical design/modelling techniques with IPMC ‘artificial muscle’ as the actuation system. The systems are designed by first simulating the performance using an IPMC model and dynamic models of the mechanical system; the appropriate advanced adaptive control schemes are then implemented to ensure that the IPMCs operate in the correct manner, robustly over time. This paper serves as an overview of the applications and concludes with some discussion on the future challenges of developing real-world IPMC applications.

Novel sulfonated styrenic pentablock copolymer/silicate nanocomposite membranes with controlled ion channels and their IPMC transducers

A novel ionic thermoplastic elastomer, poly((t-butyl-styrene)-b-(ethylene-r-propylene)-b-(styrene-r-styrene sulfonate)-b-(ethylene-r-propylene)-b-(t-butyl-styrene)) (tBS-EP-SS-EP-tBS; SSPB) pentablock copolymer, and its nanocomposites with sulfonated montmorillonite (s-MMT) have been investigated as polymer electrolytes for ionic polymer–metal composite (IPMC) actuators. The SSPB pentablock copolymer formed a well-defined microphase-separated nanodomain morphology on the several tens nanometer scale. Selectively sulfonated styrene (SS) middle blocks formed ionic conduction channels through which mobile ions are transported. The glassy hard tBS end blocks and the rubbery aliphatic EP inner blocks impart mechanical strength and mechanical toughness in the thermoplastic elastomer, respectively. The functionalized MMTs were homogeneously distributed in the SSPB/s-MMT nanocomposites and had the intercalated morphology. The resulting SSPB and SSPB/s-MMT nanocomposite IPMCs revealed not only higher tensile moduli but also higher ionic conductivities than conventional Nafion polymer electrolyte IPMCs. Among the IPMCs, the SSPB/s-MMT nanocomposite-based IPMCs with the developed morphology registered the best actuation performance in terms of bending displacement and blocking force, comparable to a typical Nafion-IPMC. Consequently, the SSPB/s-MMT-IPMCs are expected as a solution not only on the price concern but also on the physical drawback of conventional IPMCs such as fast back relaxation.

Characterization of the Temperature and Humidity Influence on Ionic Polymer–Metal Composites as Sensors

In this paper, the characterization of ionic polymer-metal composite (IPMC)-based sensors, for possible applications related to biological systems, with respect to the influence of environmental temperature and relative humidity is investigated. This paper is second in a row devoted to the characterization of IPMC transducers with respect to the aforementioned influencing quantities. The characterization is performed by statistically investigating sensing signals in typical working conditions, and the experiments performed show that, for the investigated ranges, the effects of relative humidity are much more evident than the corresponding effects produced by temperature changes. The results reported give information that integrated IPMC transducer models, which are introduced so far, contribute to better exploit this novel technology.

Electro-chemo-mechanical characteristics of fullerene-reinforced ionic polymer–metalcomposite transducers

In this paper, the effects of fullerene as a reinforcing agent in Nafion-basedionic polymer–metal composite transducers were investigated in view of theelectro-chemo-mechanical characteristics including sensing capabilities, specificelectro-mechanical energy efficiency and blocking forces. Substantial variation inthe crystallinity of fullerene–Nafion membranes even with the addition of lowconcentrations was observed in the x-ray diffraction data. The flower-like fullereneagglomerations observed in the scanning electron microscope images of the directmixing samples between fullerenes and Nafion disappeared in the present solventrecasting method and good dispersions of fullerenes in the Nafion matrix wereobserved in the atomic force microscopy images. The Fourier transform infraredspectroscopy in conjunction with its complementary x-ray photon spectroscopy showedstrong electrostatic and chemical interactions between fullerenes and sulfonatedmoieties of Nafion. Present results show that the 0.5 wt% fullerene-reinforced ionicpolymer–metal composite transducer shows nearly three times the blocking force,twice the tip displacement, three times the sensed voltage and three times theelectro-mechanical energy efficiency in comparison with a pure Nafion-based IPMCtransducer.

Static and Dynamic Characterization of the Temperature and Humidity Influence on IPMC Actuators

Several models that describe the behavior of ionic polymer-metal composite (IPMC)-based actuators can be found in the literature. The response of IPMC transducers as a function of modifying quantities is a matter of interest; however, it has not been investigated. It is reasonable to argue that environmental humidity and temperature represent the main modifying parameters. In fact, humidity changes the behavior of IPMC transducers, working as both sensors and actuators, because it changes the Young modulus of the devices and, hence, their mechanical response. The influence of temperature is suspected, because polymer characteristics are often influenced by this quantity. In a previous paper, the authors proposed a dynamic model and investigated the scaling effect of geometrical parameters, giving evidence of the excellent agreement between estimations that were obtained using the proposed model and corresponding observations. In this paper, the response of IPMC actuators to both temperature and relative humidity is analyzed, giving interesting information that both integrates IPMC models and allows for a better exploitation of IPMCs.

Development of sensing/actuating ionic polymer–metal composite (IPMC) for active guide-wire system

The potential for large deformation of the ionic polymer–metal composite (IPMC) is useful in the developments of biomedical device and miniature robot. The goal of this study is to investigate the feasibility of developing a sensing/actuating IPMC transducer as the head of an active guide-wire for cardiac catheterization. The approach employs an amplitude modulation–demodulation technique to obtain a deformation-sensing signal converted from the variation of electrical resistances in the IPMC electrodes. According to solvents and uptake conditions, three types of IPMC were produced and tested for the sensing and the actuating functions. Besides, a simulation of catheterization procedure was demonstrated with an IPMC guide-wire. From the estimated and the experimental results, the relationship between the sensing signal and the tip-displacement representing the deformation of the IPMC was verified. The sensing signal was proportional to the tip-displacement in the small deformation. The tests of the three types of IPMC showed that the sensitivity of deformation depended on the condition of material processing and solvent in IPMC. In addition, there was a trade-off between the sensing and the actuating functions of the IPMC. In the design of sensing/actuating IPMC, the electric power applied on the IPMC for actuation may interrupt the sensing signal with the migration of solvent in the IPMC. Differentiating the deformation-sensing signals between the deformed IPMC and an undeformed IPMC may alleviate the interference. The demonstration of a simulated catheterization exhibited the potential for sensing/actuating IPMC in checking the bifurcation of blood vessels without integrating a bulky sensor or adjusting the curvature of an IPMC-based active guide wire.

Improved cost-effective fabrication of arbitrarily shaped μIPMC transducers

Conventional ionic polymer–metal composite (IPMC) production cuts individual transducers from bulk IPMC sheets. This paper presents a novel photolithographic technique that grows a large array of identical devices on a thin (∼µm range) parylene diaphragm supported on a perforated substrate of material that is immune to the subsequent processing liquids. In particular, the new technique relies on a unique wax fill-up and removal concept that can produce arbitrarily shaped Nafion films with micron feature size. The developed process is cheap and results in devices of high uniformity and reliability, with greater design flexibility. Microtensile testing characterizes the fracture profiles of the non-electroded Nafion film and IPMC. Young's modulus is characterized, as well as maximum displacement and current consumption under various loading, driving voltages, waveforms and frequencies. High product quality and low process costs make this process of interest for mass production of micromachined IPMC transducers.