Snapping for high-speed and high-efficient, butterfly swimming-like soft flapping-wing robot

TL;DR

This paper presents a bioinspired soft swimming robot that uses snapping instabilities in bistable wings to achieve high speed, efficiency, and maneuverability, surpassing previous soft robots and approaching biological performance.

Contribution

It introduces a novel snapping mechanism in bistable wings for soft-bodied swimming robots, enabling record-high speed and efficiency in biomimetic aquatic locomotion.

Findings

Record-high speed of 3.74 body lengths/sec

High efficiency with Strouhal number 0.25

High maneuverability with 157°/s turning speed

Abstract

Natural selection has tuned many flying and swimming animals across different species to share the same narrow design space for optimal high-efficient and energy-saving locomotion, e.g., their dimensionless Strouhal numbers St that relate flapping frequency and amplitude and forward speed fall within the range of 0.2 < St < 0.4 for peak propulsive efficiency. It is rather challenging to achieve both fast and high-efficient soft-bodied swimming robots with high performances that are comparable to marine animals, due to the observed narrow optimal design space in nature and the compliance of soft body. Here, bioinspired by the wing or fin flapping motion in flying and swimming animals, we report leveraging the generic principle of snapping instabilities in the bistable and multistable flexible pre-curved wings for high-performance, butterfly swimming-like, soft-bodied flapping-wing robots. The soft swimming robot is lightweight (2.8 grams) and demonstrates a record-high speed of 3.74 body length/s (4.8 times faster than the reported fastest soft swimmer), high-efficient (0.2 < St = 0.25 < 0.4), low energy consumption cost, and high maneuverability (a high turning speed of 157o /s). Its high performances largely outperform the state-of-the-art soft swimming robots and are even comparable to its biological counterparts.