The hydrodynamics of water-walking arthropods

Hu, David; Bush, John W. M.

doi:10.1017/s0022112009992205

Cited by 129 publications

(154 citation statements)

References 67 publications

(88 reference statements)

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“…3 are closely related to the motion of insects up curved menisci (29,30). Insects located at fluid interfaces create distortions owing to their weight and by displacing their appendages or bending their bodies to excite capillary force distributions around their centers of mass.…”

Section: Resultsmentioning

confidence: 99%

Curvature-driven capillary migration and assembly of rod-like particles

Cavallaro

Botto

Lewandowski

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

232

234

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Capillarity can be used to direct anisotropic colloidal particles to precise locations and to orient them by using interface curvature as an applied field. We show this in experiments in which the shape of the interface is molded by pinning to vertical pillars of different cross-sections. These interfaces present well-defined curvature fields that orient and steer particles along complex trajectories. Trajectories and orientations are predicted by a theoretical model in which capillary forces and torques are related to Gaussian curvature gradients and angular deviations from principal directions of curvature. Interface curvature diverges near sharp boundaries, similar to an electric field near a pointed conductor. We exploit this feature to induce migration and assembly at preferred locations, and to create complex structures. We also report a repulsive interaction, in which microparticles move away from planar bounding walls along curvature gradient contours. These phenomena should be widely useful in the directed assembly of micro-and nanoparticles with potential application in the fabrication of materials with tunable mechanical or electronic properties, in emulsion production, and in encapsulation.anisotropic particles | colloidal interactions | colloidosome | Pickering | interfacial assemblies F luid interfaces are remarkable sites for directed migration and assembly of particles (1-6). When particles distort an interface, spontaneous, long-range interactions occur owing to capillary energy, given by the product of the surface tension and the area of the distortion. When distortions induced by neighboring particles overlap, the interfacial area decreases, resulting in capillary interactions that cause particles to attract and assemble. This effect, responsible for clustering of cereal in a bowl of milk (7), is now an important means for microparticle assembly at otherwise planar fluid interfaces, in particular for anisotropically shaped objects, which assemble with preferred orientations (4, 6, 8-13). At planar interfaces, the magnitude of the interaction is determined by the particle geometry, size, and surface energies. Hence, once the particles are placed at the interface, the strength of resulting capillary interactions is fixed. Assembly occurs at random locations on the interface determined by sites of initial encounter between the particles. In this work, we show that interface curvature can be employed as an external field to direct the location at which particles assemble. The phenomenon is entirely controlled by the coupling between geometry and capillarity. Therefore, it can be applied to colloids made of any material.When an anisotropic particle is placed on a curved fluid interface, capillary interactions arise, as the area of the interface then depends on the particle's orientation with respect to the principal axes and its location in a curvature gradient, resulting in torques (5, 14) and forces (5) on the particle. Because fluid interfaces can be molded and reconfigured using pinning sites, ...

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Section: The Journal Of Experimental Biologymentioning

confidence: 99%

“…Likewise, we did not measure the differential wettability of ant body parts, which is another potentially important variable in their interaction with the water surface (Suter, 2013). Detailed force and hydrophobicity analyses have been conducted for other taxa (Hu and Bush, 2010;Suter, 2013) and provide good models for future studies of water surface locomotion in ants.The kinematic features of swimming in terrestrial arthropods are highly variable among taxa (Miller, 1972;Andersen, 1976;Franklin et al, 1977). Similar inconsistencies occur among ants.…”

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confidence: 99%

Water surface locomotion in tropical canopy ants

Yanoviak

Frederick

2014

Journal of Experimental Biology

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Upon falling onto the water surface, most terrestrial arthropods helplessly struggle and are quickly eaten by aquatic predators. Exceptions to this outcome mostly occur among riparian taxa that escape by walking or swimming at the water surface. Here we document sustained, directional, neustonic locomotion (i.e. surface swimming) in tropical arboreal ants. We dropped 35 species of ants into natural and artificial aquatic settings in Peru and Panama to assess their swimming ability. Ten species showed directed surface swimming at speeds >3 body lengths s −1 , with some swimming at absolute speeds >10 cm s −1 . Ten other species exhibited partial swimming ability characterized by relatively slow but directed movement. The remaining species showed no locomotory control at the surface. The phylogenetic distribution of swimming among ant genera indicates parallel evolution and a trend toward negative association with directed aerial descent behavior. Experiments with workers of Odontomachus bauri showed that they escape from the water by directing their swimming toward dark emergent objects (i.e. skototaxis). Analyses of high-speed video images indicate that Pachycondyla spp. and O. bauri use a modified alternating tripod gait when swimming; they generate thrust at the water surface via synchronized treading and rowing motions of the contralateral fore and mid legs, respectively, while the hind legs provide roll stability. These results expand the list of facultatively neustonic terrestrial taxa to include various species of tropical arboreal ants. KEY WORDS: Aquatic, Behavior, Forest, Formicidae, Neustonic, Skototaxis INTRODUCTIONEfficient locomotion at the air-water interface is relatively uncommon in nature (Vogel, 1994). Most terrestrial arthropods are helpless when they fall onto water, in part because their small body size makes them vulnerable to entrapment by surface tension forces. Additionally, the relatively low physical resistance of water to slender kicking appendages often leads to a futile struggle ending in death via drowning or predation. Conspicuous exceptions to these generalities include the specialized water-treading behaviors and morphologies of neustonic insects and spiders (Andersen, 1976;Milne and Milne, 1978;Vogel, 1994;Hu et al., 2003). For species lacking such traits, escape from the water surface usually is fortuitous.The very specialized legs of obligate pelagic and neustonic taxa such as diving beetles and water striders facilitate efficient locomotion below or on the water surface (Nachtigall, 1974), but are relatively ineffective and clumsy on land. The gaits of these insects often are kinematically distinct from the alternating tripod gait used by terrestrial species in the same clades (Andersen, 1976). By contrast, riparian arthropods frequently tread on both land and water with high efficiency using the same gaits and appendages. For example, the hydrophobic tarsi of riparian Hydrophorus flies allow them to alight on water or vegetation (Burrows, 2013), and the modified hin...

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“…P henomena driven by surface tension are important in a variety of biological systems (1,2), and in recent years the importance of working with living organisms to test theoretical biophysical models [e.g., trees (3,4), arthropods (5)(6)(7)(8), and birds (9, 10)] has become evident. Exploration of natural solutions to specific fluid dynamics challenges has provided conceptual tools fostering practical advances in a wide array of fields (11,12).…”

mentioning

confidence: 99%

The hummingbird tongue is a fluid trap, not a capillary tube

Rico-Guevara

Rubega²

2011

Proc. Natl. Acad. Sci. U.S.A.

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Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue-fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).biomechanics | fluid dynamics | nectar trapping | surface tension

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“…Squid and octopus employ large volume and shape deformations to power their locomotion and maneuvering (Huffard 2006;Packard 1969;Muller & Lentink 2004;Polet et al 2015). Rowing involves imparting momentum to the fluid through motion of the oars, which are then retracted leaving an energetic wake behind; likewise insects and lizards can walk on water by submerging and then retracting their legs (Dickinson 2003;Hsieh & Lauder 2004;Hu & Bush 2010).…”

Section: Introductionmentioning

confidence: 99%

Shape of retracting foils that model morphing bodies controls shed energy and wake structure

et al. 2016

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The flow mechanisms of shape-changing moving bodies are investigated through the simple model of a foil that is rapidly retracted over a spanwise distance as it is towed at constant angle of attack. It is shown experimentally and through simulation that by altering the shape of the tip of the retracting foil, different shape-changing conditions may be reproduced, corresponding to: (a) a vanishing body, (b) a deflating body, and (c) a melting body. A sharp-edge, 'vanishing-like' foil manifests strong energy release to the fluid; however it is accompanied by an additional release of energy, resulting in the formation of a strong ring vortex at the sharp tip edges of the foil during the retracting motion. This additional energy release introduces complex and quickly-evolving vortex structures. By contrast, a streamlined, 'shrinking-like' foil avoids generating the ring vortex, leaving a structurally simpler wake. The 'shrinking' foil also recovers a large part of the initial energy from the fluid, resulting in much weaker wake structures. Finally, a sharp-edged but hollow, 'melting-like' foil provides an energetic wake while avoiding the generation of a vortex ring. As a result, a melting-like body forms a simple and highly energetic and stable wake, that entrains all of the original added mass fluid energy. The three conditions studied correspond to different modes of flow control employed by aquatic animals and birds, and encountered in disappearing bodies, such as rising bubbles undergoing phase change to fluid.

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The hydrodynamics of water-walking arthropods

Cited by 129 publications

References 67 publications

Curvature-driven capillary migration and assembly of rod-like particles

Water surface locomotion in tropical canopy ants

The hummingbird tongue is a fluid trap, not a capillary tube

Shape of retracting foils that model morphing bodies controls shed energy and wake structure

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