Harnessing Unidirectional Deformation Driven by Light and Temperature: Towards Untethered Soft Microgripper in Diverse Environments

Abstract

Stimuli-responsive soft actuators have gained significant attention in soft robotics, biomedical devices, microfluidics, etc. However, most existing designs rely on a single stimulus or focus on bidirectional actuation, limiting their ability to mimic natural organisms that adapt seamlessly to both dry and wet environments. Actuators capable of reversible, unidirectional motion in response to multiple independent stimuli remain largely unexplored. In this work, we present a bilayer actuator composed of polyvinyl alcohol, functionalized anthracene, and poly N-isopropylacrylamide (PVA-An/PNIPAM).The system exhibits unidirectional actuation triggered by two distinct stimuli: blue light (455 nm) in dry conditions and temperature changes (physiological range) underwater. Under blue light, the actuator shows reversible bending, while heating above the LCST induces reversible film scrolling. The actuation response is tunable through variations in dye concentration, PNIPAM content, light intensity, and temperature.The hydrogen bonding between hydrophilic PVA and PNIPAM matrix ensures excellent interlayer adhesion, preventing delamination even after multiple actuation cycles. This work is poised to address the underexplored multi-stimuli unidirectional actuator where both independent stimuli produce a cooperative rather than antagonistic response. This work's robust and straightforward approach could be attractive for biomedical, microfluidics, and marine research, offering enhanced efficiency, functionality, and sustainability.