7. Conducting Polymers

Soft actuators based on conducting polymers are discussed in terms of strain, stress and stability taking the mechanism into consideration. The actuation is generated by the insertion of anions from the electrolyte solution, which is triggered by electrochemical redox reactions. Characteristics of the actuation in polypyrrole, polyaniline, polythiophene, and poly(3,4-ethylenedioxythiophene) (PEDOT) are described. The maximum strain and stress are reported to be 39.9 % and 22 MPa, respectively, in polypyrrole actuator. However, the strain is usually less than 10 %. The stress (contraction force) originates from the elasticity of conducting polymers or Young’s modulus. Creeping under tensile loads, which is intimate issue in soft actuators, is discussed in terms of conformation change of polymer chains and shape memory effect. The actuation generated by sorption and desorption of moisture controlled with electrical heating is also introduced with the mechanism and characteristics.