Marangoni-Effect-Driven Locomotion of Patterned Gels with Evolved Shape Changes and Varied Motion Modes.

The Marangoni effect, driven by interfacial tension gradients, provides a powerful mechanism for achieving autonomous motion in robotics. In gels containing low-surface-tension solvents, motion behavior is primarily governed by solvent-release dynamics and gel's body geometry, which together define the interfacial net force or torque and thus the resulting motion mode. However, conventional systems based on such Marangoni effect exhibit a single, fixed motion mode because the shape and composition of the material are predetermined. Here, we demonstrate a patterned gel with ethanol as the solvent that integrates two types of gels with distinct solvent-release and swelling behaviors in water, enabling spontaneous changes in shape and motion mode during Marangoni-effect-driven propulsion. When the gel is placed on water, ethanol release from the gel generates a tension gradient that drives motion. The initial geometry of the patterned gel determines the early propulsion mode, while time-dependent solvent diffusion and swelling continuously reshape the gel and thus alter the surface-tension gradient. These evolved variations enable autonomous transition between distinct motion modes, such as spontaneous switching from clockwise to anticlockwise rotation, or from rotation to translation. Such locomotion with time-variant motion modes establishes a new paradigm for programmable and adaptive motion, expanding opportunities in soft robotics and cargo transportation.