Biomimetic self-powered artificial muscle using tri-functional yarns that combine generator, supercapacitor, and actuator functions

Abstract

Artificial muscles, which should mimic the characteristics of natural muscles, have an energy integration system, a yarn structure, and tensile actuation ability. We present new tensile self-powered artificial muscle yarns (SPAM) with systemic, structural, and actuation characteristics similar to those of myofibrils. To biomimic the energy conversion process of natural muscles, the presented SPAM system converts chemical energy into me-chanical energy in a two-sequence stage. First, a generator converts the chemical energy into electrical energy, thereby creating an electrochemical ion gradient. Second, when the self-generated energy is applied to the actuator, the ions created by the electrochemical energy induce a change in the physical volume, which results in the contraction of the actuator. In this study, MWNT-coiled yarns were used as tri-functional yarns that simul-taneously act as a generator, supercapacitor, and an actuator. This SPAM system comprises a generator with MWNT-coiled yarns (i.e., the anode) and reduced graphene oxide (RGOx) (i.e., the cathode); in addition, the MWNT-coiled yarns use an electrochemical actuator. The presented SPAM has three advantages over previously presented systems: (1) the coiled yarn structure provides a high tensile stroke; (2) the supercapacitor enables fast contraction within 2.3 s; and (3) the self-charging system enables reversible actuation