Pitch-tuned coiled polymer actuator for large contractile strain under light-loading

Abstract

We demonstrate a pitch-tuned coiled polymer actuator that can produce a large thermally-induced-contractile-strain under a light-loading. For a pitch-tuning of the coiled polymer actuator (CPA), we sequentially implement a twist-insertion for coiling a nylon-6 fiber, mechanical pre-stretching, and a couple of thermal treatments. By adopting our pitch-tuning methodology, geometric structure of the original CPA can be consistently modulated with a pre-stretching ratio. When heated under a light-loading, the pitch-tuned CPA can produce a contractile strain far beyond the original CPA with a limited space to contract. Due to the benefit, pitch-tuning for the CPA can open an opportunity to utilize the CPA as an artificial muscle for soft micro-robot.