Stimuli-responsive hydrogel microsprings for multiple and complex actuation

Abstract

This paper describes stimuli-responsive hydrogel microsprings (SR springs) for realizing multiple and complex actuation. SR springs, made of double network hydrogel of p(NIPAM-co-AAc) and calcium alginate, were continuously formed by using a bevel-tip capillary. The size, pitch and cross-sectional pattern of SR springs were variable by controlling flow rate, buoyancy force and laminar flow patterns during the spring formation process. By heating single-layered or double-layered SR springs, we achieved five different types of complex spring movements: cross-sectional compression, axial compression, axial expansion, winding up and winding down. We believe that our SR springs could pave the way to various microscale chemomechanical applications such as autonomous soft machines/robots and drug release systems.