Bio-Inspired Fast-Moving and Steerable Insect-Scale Soft Aquatic Surface Robot

High-speed and good trajectory controllability are two critical attributes of small artificial aquatic surface robots. Inspired by the moving mechanism of water striders, we herein propose insect-scale soft aquatic surface robots utilizing piezoelectric actuation coupled with asymmetric footpads. The aquatic surface robots move quickly without penetrating the water-air interface and utilize incoordinate propulsive force from asymmetric footpads to realize precise trajectory control. An ultrafast linear speed of 21.82 BL/s (24 cm/s) and a high angular speed of 303 degrees/s are achieved, which are advanced among small aquatic surface robots. We showcase agility and maneuverability by navigating through a water maze with a total route length of 88 cm in an actual driving time of 16.5 s. Moreover, proof-of-concept for search and rescue operations is demonstrated by using a robot to tow an on-water monitoring system to record a real-time video showing the "SOS" symbol. An untethered robot is also demonstrated to improve the practical potential. The design principles, operation mechanisms, and steering characteristics presented in this work provide fundamental guidelines for the development of future small aquatic surface robots.