Mechanical response of twisted multifilament artificial muscles upon thermal actuation

Abstract

Recently-developed twisted multifilament artificial muscles are an intelligent material or device storing energy and outputing work under external stimuli. These muscles are fabricated by a twist-insertion procedure and share a two-step process in triggering rotation or contraction, that is volumetric expansion and tension-torsion coupling. The energy conversion efficiency of thermal actuation for the artificial muscles made of carbon nanotubes has attracted increasing attention due to the giant tensile stroke, record energy density, and easy controllability. In the present paper, the thermal actuation processes of artificial muscles are modeled by numerical simulations, in which the energy conversion efficiency is expressed as the ratio of work output to heat input. The Cosserat curve theory is introduced to analyze the geometric effect of cross-sectional shapes on the tensile TMFAM. The abilities of axial elastic deformation and stretching stable for the CNTBs with typical shapes are quantified. The work output and energy conversion efficiency are then evaluated, offering the opportunity to elevate the mechanical properties of artificial muscles. The strategy to improve the muscle performance is also outlined through their dependence on the geometrical and material parameters.