Speaker: Dr. Alessandro Leronni, Cambridge University

Room: A-133

Abstract: Ionic polymer metal composites (IPMCs) are microscale devices consisting of an ionic polymer membrane sandwiched between metal electrodes. The motion of ions along the membrane thickness as a result of an electrical or mechanical stimulus provides IPMCs with actuation and sensing capabilities. The response of IPMCs is difficult to predict, as it depends on the complex interaction of different physical phenomena at multiple scales. In this talk, I first present a minimal continuum model able to qualitatively describe the time-dependent actuation and sensing of IPMCs through ion electro-diffusion and related osmotic pressure gradients. Then, I introduce some complexities in the mechanics and discuss their effect in detail. In actuation, I focus on the role of Maxwell stress due to voltage gradients at the membrane/electrode interfaces, and on the competition between electro-osmosis and pressure-driven solvent flow. In sensing, I consider the shear deformation of the membrane ensuing from the IPMC sandwich structure, and I study the interplay between convective and electro-diffusive ion transport. I expect this non-trivial mechanics to be helpful in explaining non-intuitive experimental observations.