Light-Driven Undulatory Locomotion of a Liquid Crystal Gel Robot for Programmable 3D Navigation

Untethered, soft robots that replicate the undulatory swimming of aquatic organisms could transform minimally invasive medicine, yet no existing material system simultaneously affords continuous, reconfigurable curvature, rapid actuation and aqueous autonomy. Here we introduce a leech-inspired robot composed of a single liquid-crystal gel (LCG) sheet whose twist-nematic director field encodes traveling-wave kinematics. Under remote laser scanning, the sheet generates metachronal waves that drive forward propulsion at 0.5 mm s^-1; localized head illumination reorients the body vector to program upward, upper-left and upper-right trajectories, yielding full-space swimming in saline media. Thus, a LCG leech navigating through a tunnel in three-dimensional (3D) space is enabled. We further expand this capability by integrating two LCG leeches into a single monolithic LCG construct. Through spatiotemporal control of light irradiation, this integrated system demonstrates both forward and rotating swimming modes. Consequently, we achieve underwater locomotion with the functionality of transporting cargo along any predesigned path. Molecular-level patterning of the nematic order thus translates optical commands into complex, biomimetic locomotion without on-board electronics, offering a versatile platform for smart soft microrobots in fluidic environments.