Light-driven lattice soft microrobot with multimodal locomotion

Abstract Untethered microrobots hold significant promise in fields such as bionics, biomedicine, and micromechanics. However, replicating the diverse movements of natural microorganisms in artificial microrobots presents a considerable challenge. This paper introduces a laser-based approach that utilizes lattice metamaterials to enhance the deformability of hydrogel-based microrobots, resulting in untethered light-driven lattice soft microrobots (LSMR). Constructed from poly(N-isopropylacrylamide)-single-walled carbon nanotubes (PNIPAM-SWNT) hydrogels and a truncated octahedron lattice structure, the LSMR benefits from reduced relative density, which increases flexibility and accelerates light-driven deformation. By employing sequential laser scanning, the LSMR achieves various locomotion modes, including linear peristalsis, in situ rotation, and hopping, through adjustments in scanning frequency, trajectory, and laser power. The LSMR achieves a continuous in situ rotation speed of 29.38°/s, nearly 30 times faster than previous studies, and exhibits a peristaltic locomotion speed of 15.15 μm/s (0.14 body lengths per second). The LSMR can autonomously perform programmed motions under closed-loop feedback control and navigate through narrow openings as small as 75% of its resting width by actively deforming. Compared to a solid microrobot, the lattice microrobot requires only one-sixth of the laser energy to achieve three times the motion speed, under otherwise identical conditions. These advancements mark a significant leap forward in the design and functionality of light-driven soft microrobots, offering promising avenues for future research in biomedicine, bionics, and micromechanical engineering.