In this paper, we developed a new kind of ionic polymer metal composite (IPMC) actuator by doping sulfonated carbon nanotube (SCNT) into Nafion matrix to overcome some major drawbacks, such as low output force and short air-operation time, which restrict applications of conventional Nafion IPMC actuators. Firstly, SCNT was synthesized by coupled reaction of multi-walled carbon nanotubes and azo compounds and then doped into Nafion matrix by casting method. Subsequently, several key parameters of the SCNT-reinforced Nation matrix, water uptake ratio and equivalent stiffness, were revealed and the inner morphology of the membranes were observed by scanning electron microscopy. Finally, the effects of the SCNT on the electromechanical properties of IPMC actuators, especially the actuating performance, were evaluated experimentally and analyzed systematically. The results showed that SCNT was evenly dispersed in Nafion matrix and a small amount of SCNT could improve the performance of IPMC actuators significantly.
Ionic Polymer-Metal Composite (IPMC) actuators have been attracting a growing interest in extensive applications, which consequently raises the demands on the accuracy of its theoretical modeling. For the last few years, rough landscape of the interface between the electrode and the ionic membrane of IPMC has been well-documented as one of the key elements to ensure a satisfied performance. However, in most of the available work, the interface morphology of IPMC was simplified with structural idealization, which lead to perplexity in the physical interpretation on its interface mechanism. In this paper, the quasi-random rough interface of IPMC was described with fractal dimension and scaling parameters. And the electro-chemical field was modeled by Poisson equation and a properly simplified Nernst–Planck equation set. Then, by simulation with Finite Element Method, a comprehensive analysis on he inner mass and charge transportation in IPMC actuators with different fractal interfaces was provided, which may be further adopted to instruct the performance-oriented interface design for ionic electro-active actuators. The results also verified that rough interface can impact the electrical and mechanical response of IPMC, not only from the respect of the real surface increase, but also from mass distribution difference caused by the complexity of the micro profile.
IPMC was considered as a polyelectrolyte membrane sandwiched between two flat electrodes in most of its theoretical
models. However, structural idealization (ignorance of the interface) may lead to problematic predictions; therefore a
proper model to characterize IPMC structures is expected for a more sophisticated electrochemistry or deformation
theory. This paper proposed a geometrical model for the electroless-plated palladium-electroded IPMC (Pd-IPMC),
where it's treated as a composite containing three distinguished layers: upper electrode, interface layer, and the substrate
membrane. Especially, fractal dimension was adopted to describe the rough contact surface between the upper electrode
and the substrate membrane. And the interface was determined by the volume fraction of the palladium particles. Based
on this model, we estimated the elastic modulus of Pd electrode, and the value was found to be far less than Pd metal.
Furthermore, we estimated the tensile elastic modulus of Pd-IPMC, the result agrees well with the experimental one,
which proved the applicability of the structure model.
The electrode of Ionic polymer-metal composites (IPMCs) is the key to understand their working mechanisms and
mechano-electrical properties; however, there is little experimental report on the electrode morphologies and their
forming mechanisms. In this paper, several typical IPMC samples with different electrode morphologies are fabricated
by combining various process steps. The influence of the process steps, such as roughing treatment, immersing reduction
and chemical plating, on the electrode surface and cross-section morphologies is investigated by SEM study, where the
reaction principles are employed to explain that how the metal particles generate and grow at different directions of the
electrode. The current and deformation responses of the samples are measured at the present of a voltage to characterize
the mechano-electrical properties. Then it is concluded that immersing reduction is only suitable as a pre-deposition
process step, and chemical plating is necessary for IPMC with desirable performance.