A foldable small-scale soft electromagnetic robot for multimodal navigation in confined and unstructured environments

Multimodal locomotion is crucial for an animal's adaptability in unstructured wild environments. Analogously, in the human gastrointestinal tract, characterized by viscoelastic mucus, complex rugae, and narrow openings like the cardia, multimodal locomotion is also essential for a small-scale soft robot to conduct tasks. Here, we introduce a small-scale, compact, foldable, and robust soft electromagnetic robot with more than nine locomotion modes designed for such a scenario. Featuring a six-spoke elastomer body embedded with liquid metal channels and driven by Laplace forces under a static magnetic field, the robot is capable of rapid transitions ( < 0.35 s) among different locomotion modes. It achieves exceptional agility, including high-speed rolling (818 mm/s, 26 body lengths per second), omnidirectional crawling, jumping, and swimming. Notably, the robot can fold to reduce its occupied volume by 79%, enabling it to traverse confined spaces. We further validate its navigation capabilities in unstructured environments, including discrete obstacles, viscoelastic gelatin surfaces, viscous fluids, 3D-printed gastric surfaces, and a porcine gastric environment. This system offers a versatile strategy for developing high-mobility soft robots for future biomedical applications.