Amphibious Movement of Microrobots Inspired by Water Spiders.

Magnetic actuation provides an effective means for tetherless control of microrobots in complex environments. Inspired by the morphology and interfacial flotation mechanism of water striders, we design a four-legged microrobot with small ribs on its feet to mimic the structure of water striders. Through an asymmetric magnetic response between its poles inside four legs, two bio-inspired motion modes and three extended modes are controlled by the magnetic field during complex amphibious locomotion. The microrobot can generate vortices for locomotion on the air-water interface like water striders; it also keeps the non-contact cargo-capturing and transporting capacity with the Rotate motion mode. When switched to the Swing mode, the microrobot can overcome surface tension and enter the liquid interior. In a liquid environment, the microrobot can keep continuous lateral oscillations like water striders; it breaks flow field symmetry to generate vertical displacement. Besides, the microrobot ultimately demonstrates the ability to cross the air-liquid interface and execute directional movement in sophisticated multi-element environments and within the complex gastric wall structure, thus ensuring precise controllability. This biomimetic microrobot offers a highly valuable design concept for microrobots requiring amphibious locomotion capabilities.