Silver-Nanowires Coated Pitch-Tuned Coiled Polymer Actuator for Large Contractile Strain under Light-Loading

We report a pitch-tuned coiled polymer actuator (CPA) with a compliant silver-nanowires (AgNWs) electrode. For a pitch-tuning of the CPA, we sequentially implement a twist-insertion for coiling a nylon-6 fiber, mechanical pre-stretching, and a couple of thermal treatments. When heated under a light-loading, the pitch-tuned CPA can produce a contractile strain far beyond the original one with a limited space to contract. Since the silver-nanowires electrode established on the coiled structure retains a fairly consistent electrical property allowing repetitive Joule-heating under a large uniaxial elongation with loading, the synergetic benefits from pitch-tuning and adopting the AgNWs as a Joule-heating electrode enables the CPA to produce electrically-controllable and large contractile strain under a light-loading that can be utilized for an artificial muscle of soft micro-robot.