Suppression of electrochemical creep by cross-link in polypyrrole soft actuators

In soft actuators, the creep under tensile loads is a serious problem for the positioning. The creep during electrochemical cycle (electrochemical creep) in conducting polymers is remarkable compared with the static creep under tensile loads. Correlation between the electrochemical creep and the actuating strain in polypyrrole films doped with docecylbenzene sulfonic (DBS) anion has been studied in NaCl aqueous electrolyte. It has been found that chemical cross-link in polypyrrole with di-pyrrole alkanes suppressed the creep, however, the actuator strain also decreased. The creep in crossliked PPy saturated after several cycles, keeping the strain of actuation constant. The result indicates the creep can be minimized by idling before use. Scan rate dependences of the electrochemical creep and actuation were also examined to find the ways to depress the creep.