2025-08-21 カリフォルニア大学バークレー校(UCB)
The feet of the insect-like, semi-aquatic robot Rhagobot, developed by engineers at Ajou University, mimic the fan-like feet of Rhagovelia. The self-morphing fans open underwater (right) to form a rigid oar for agile maneuvering in turbulent water. Ajou University, South Korea
＜関連情報＞
- https://news.berkeley.edu/2025/08/21/wing-like-fans-on-the-feet-of-ripple-bugs-inspire-a-novel-propulsion-system-for-miniature-robots/
- https://www.science.org/doi/10.1126/science.adv2792
超高速弾性毛細管ファンが波紋虫とロボットの機敏な操縦を制御する Ultrafast elastocapillary fans control agile maneuvering in ripple bugs and robots
Victor M. Ortega-Jimenez, Dongjin Kim, Sunny Kumar, Changhwan Kim, […] , and Saad Bhamla
Science Published:21 Aug 2025
DOI:https://doi.org/10.1126/science.adv2792
Editor’s summary
Fans attached to the legs of Rhagovelia, commonly known as ripple bugs, automatically deploy protrusions on their middle legs under water. Ortega-Jimenez et al. examined this phenomenon from the structural, behavioral, and energy consumption perspectives (see the Perspective by Aubin). They show that the protrusions have a flat-ribbon microarchitecture, enabling fast capillary actuation. Furthermore, the individual barbs have divergent rigidity in orthogonal directions, facilitating both elastocapillary morphing and effective force production during a propulsive stroke, which enhances thrust production through unsteady vortices and capillary waves. The researchers designed an insect-scale robot equipped with synthetic, ultralight, ultrafast elastocapillary fans and demonstrated how these structures enable a variety of movements at impressive speeds. —Marc S. Lavine
Abstract
Rhagovelia ripple bugs use specialized middle-leg fans with a flat-ribbon architecture to navigate the surfaces of fast-moving streams. We show that the fan’s directional stiffness enables fast, passive elastocapillary morphing, independent of muscle input. This flat-ribbon fan balances collapsibility during leg recovery with rigidity during drag-based propulsion, enabling full-body 96° turns in 50 milliseconds, with forward speeds of up to 120 body lengths per second—on par with fruit fly saccades in air. Drawing from this morphofunctional architecture, we engineered a 1-milligram elastocapillary fan integrated into an insect-scale robot. Experiments with both insects and robots confirmed that self-morphing fans improve thrust, braking, and maneuverability. Our findings link fan microstructure to controlled interfacial propulsion and establish design principles for compact, elastocapillary actuators in agile aquatic microrobots.
