Electro-morphing of particle rafts*

Materials that turn their shapes in response to external stimuli are actively sought for in soft matter physics, soft robotics, and architecture. Conventional approaches adopting patterns of stretchable soft solids, folds, or cuts have succeeded in inducing dramatically large deformations, but only in a preprogrammed manner at specified locations. Therefore, expanding the realm of shape-morphing technologies strongly requires material systems that can undergo significant shape-shifting without prescribed patterns. Here we present a liquid interface covered by dielectric particles, or a particle raft, which can rapidly and reversibly morph under the external electric field. The initially flat rafts transform to a mound and a tower within seconds and then move horizontally, driven by electrostatic attraction between electrodes and particles, while stabilized by electric discharge. Our study presents a highly deformable and electrically controllable soft material system with potential applications including the human-machine interface.