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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.
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]
Copyright of Science is the property of American Association for the Advancement of Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Psychology and Behavioral Sciences Collection
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  Data: Ultrafast elastocapillary fans control agile maneuvering in ripple bugs and robots.
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  Data: <searchLink fieldCode="AR" term="%22Ortega-Jimenez%2C+Victor+M%2E%22">Ortega-Jimenez, Victor M.</searchLink><br /><searchLink fieldCode="AR" term="%22Kim%2C+Dongjin%22">Kim, Dongjin</searchLink><br /><searchLink fieldCode="AR" term="%22Kumar%2C+Sunny%22">Kumar, Sunny</searchLink><br /><searchLink fieldCode="AR" term="%22Kim%2C+Changhwan%22">Kim, Changhwan</searchLink><br /><searchLink fieldCode="AR" term="%22Koh%2C+Je-Sung%22">Koh, Je-Sung</searchLink><br /><searchLink fieldCode="AR" term="%22Bhamla%2C+Saad%22">Bhamla, Saad</searchLink>
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  Data: <searchLink fieldCode="JN" term="%22Science%22">Science</searchLink>. 8/21/2025, Vol. 389 Issue 6762, p811-817. 7p.
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  Data: <searchLink fieldCode="DE" term="%22Riffle+bugs%22">Riffle bugs</searchLink><br /><searchLink fieldCode="DE" term="%22Stiffness+%28Mechanics%29%22">Stiffness (Mechanics)</searchLink><br /><searchLink fieldCode="DE" term="%22Capillary+waves%22">Capillary waves</searchLink><br /><searchLink fieldCode="DE" term="%22Microrobots%22">Microrobots</searchLink><br /><searchLink fieldCode="DE" term="%22Microstructure%22">Microstructure</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: 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]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Science is the property of American Association for the Advancement of Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Text: English
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              Text: 8/21/2025
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