Ultrafast elastocapillary fans control agile maneuvering in ripple bugs and robots.
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| Title: | Ultrafast elastocapillary fans control agile maneuvering in ripple bugs and robots. |
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| Authors: | Ortega-Jimenez, Victor M., Kim, Dongjin, Kumar, Sunny, Kim, Changhwan, Koh, Je-Sung, Bhamla, Saad |
| Source: | Science. 8/21/2025, Vol. 389 Issue 6762, p811-817. 7p. |
| Subjects: | Riffle bugs, Stiffness (Mechanics), Capillary waves, Microrobots, Microstructure |
| 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. 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 FROM AUTHOR] |
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| Database: | Psychology and Behavioral Sciences Collection |
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| 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. 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 FROM AUTHOR] |
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| ISSN: | 00368075 |
| DOI: | 10.1126/science.adv2792 |
