Conducting Polymers as EAPs: Fundamentals and Materials

Abstract

Films of conducting polymers (CPs) follow reversible volume variations by electrochemical oxidation/reduction in liquid electrolytes: the actuation principles are presented. Actuators, or artificial muscles, transducing those volume variations into large macroscopic movements are presented here. The same reaction gives exchange of anions, or cations, and opposed film volume variations (here described) from different families of CPs. Transduction from the small local volume changes to macroscopic movements has required different designs and structures. A good control of the movement requires a good theoretical description. Two different approaches, as mechanical-based devices or as electrochemical devices, are presented. Moreover the electrochemical reaction driving the muscles movement also senses any physical or chemical variable acting on the reaction energy. The sensing principle is presented giving dual sensing-actuators: an actuator, a mechanical sensor, a chemical sensor, a thermal sensor, and an electrical sensor work simultaneously, driven by the same reaction, in a physically uniform device. Only haptic muscles from mammals are dual actuating-sensor originating proprioception: the mammal brain is aware of position, movement rate and direction, trailed weight, muscle fatigue state, or working temperature during movements. The artificial proprioceptive equations, attained from electrochemical, mechanical, and polymeric principles, allow an easy description and control of the multi-tool device.