Snapping for high-speed and high-efficient butterfly stroke–like soft swimmer

Abstract

Natural selection has tuned many flying and swimming animals to share the same narrow design space for high power efficiency, 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 comparably fast-speed and high-efficient soft swimmers to marine animals due to the naturally selected narrow design space and soft body compliance. Here, bioinspired by the flapping motion in swimming animals, we report leveraging snapping instabilities for soft flapping-wing swimmers with comparable high performance to biological counterparts. The lightweight, butterfly stroke–like soft swimmer (2.8 g) demonstrates a record-high speed of 3.74 body length/s (4.8 times faster than the reported fastest flapping soft swimmer), high power efficiency (0.2 < St = 0.25 < 0.4), low energy consumption cost, and high maneuverability (a high turning speed of 157°/s).

A modular strategy for distributed, embodied control of electronics-free soft robots

“…Soft robotics has become a notable area of research in recent years, with the potential to enable robots with a number of promising characteristics (1,2), such as resilience to large deformation (3,4), safe human-machine interaction (5,6), environmental adaptability (7,8), novel and adaptable locomotion strategies (9,10), and resistance to impact (11,12). Versatile deformable structures and actuating materials have been adopted in the design and fabrication of soft robots, including pneumatic and hydraulic actuators (13)(14)(15), dielectric elastomer actuators (16,17), liquid crystal elastomers (LCEs) (18)(19)(20), magnetic actuators (21,22), and hydrogels (23,24). Numerous useful functionalities have been demonstrated in soft robots, including gripping (25,26), crawling (27,28), jumping (29,30), and shape adaptability (31,32).…”

Bio‐Mimic, Fast‐Moving, and Flippable Soft Piezoelectric Robots

“…Several different types of soft actuators have been developed such as light actuators, [1][2][3][4][5][6][7] electrical actuators, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] thermal actuators, [27][28][29][30][31][32][33][34][35][36] DOI: 10.1002/advs.202300673 magnetic actuators, [37][38][39][40][41][42][43][44][45][46][47] and fluidic actuators. [48][49][50][51]…”

“…Several different types of soft actuators have been developed such as light actuators, [ 1–7 ] electrical actuators, [ 8–26 ] thermal actuators, [ 27–36 ] magnetic actuators, [ 37–47 ] and fluidic actuators. [ 48–53 ] Soft actuators and body structures enable more degrees of freedom. They can be integrated and fused, similar to biological systems.…”

Pseudo-bistability of viscoelastic shells

“…Such instabilities are ubiquitous in nature and our daily life: Venus flytrap, the famous plant capable of fast movement, can rapidly flip its bistable leaves to catch prey [6], while hair clips can be quickly sprung up and down by fingers. The snap-through buckling of elastic shells has been widely employed to achieve rapid deformation in various applications, such as soft actuators [9][10][11][12], logic switches [13,14], and responsive surfaces [15]. Many of these works are based on elastomeric shells, most of which exhibit viscoelasticity.…”