Design principles of hair-like structures as biological machines

Seale, Madeleine; Cummins, Cathal; Viola, Ignazio Maria; Mastropaolo, Enrico; Nakayama, Naomi

doi:10.1098/rsif.2018.0206

Cited by 29 publications

(24 citation statements)

References 180 publications

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“…The performance of arrays of hair‐like structures, such as ctenes, in locomotion depends on how much of the fluid flows through the gaps between the hairs, termed the leakiness of the array, as opposed to flowing around the perimeter of the whole array (Koehl, 2001). At very low Reynolds numbers, Re < 1, each hair in the array is surrounded by a thick boundary layer that extends into the fluid, so when hairs are close, the interacting boundary layers significantly reduce fluid flow between hairs and thus the array behaves like a paddle with a continuous surface (Seale, Cummins, Viola, Mastropaolo, & Nakayama, 2018). In general, as the Reynolds number of the array increases, so too does the leakiness (Koehl, 2001).…”

Section: Discussionmentioning

confidence: 99%

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

Goebel

Colin

Costello

et al. 2020

Invertebrate Biology

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Ctenophores coordinate large macrociliary structures called ctenes to propel themselves through the water. The morphology and kinematics of the ctenes mediate swimming performance. We investigated morphological and kinematic factors affecting swimming performance in free‐swimming ctenophores (Pleurobrachia bachei) using high speed videography. Our morphological results showed that the relationship between body size and ctene morphology and arrangement in P. bachei were well described using linear (i.e., isometric) relationships, which suggests functional limitations of ctenes that vary among individuals of different sizes. Our kinematic results showed that isometric constraints on swimming performance can potentially be overcome by alterations in kinematics: (a) swimming speed in P. bachei increased with ctene beat frequency over a range of body lengths, and (b) the separation of ctenes into clumps of cilia allowed the ctene to increase in width during the effective stroke and decrease in width during recovery. Separation increases the surface area of the ctene during the effective stroke, likely increasing the thrust produced. The finding that ctenes are not monoliths and instead are separated into clumps of cilia has not been previously described, and we subsequently observed this trait in three other ctenophore species: Euplokamis dunlapae, Bolinopsis infundibulum, and Beroe mitrata. Flexibility in function may be a necessary corollary to isometric development of the ctenes as propulsive structures.

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Section: Discussionmentioning

confidence: 99%

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

Goebel

Colin

Costello

et al. 2020

Invertebrate Biology

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“…Here, µ air = 1.8 × 10 −5 a.s is the dynamic viscosity of air, U air < 1 ms −1 is the radial air-speed out of the narrow gap estimated based on our recent report 47 , Z ≈ 1.5 µm is the representative length of microtrichia, E ≈ 9 GPa is the characteristic Young's modulus for hairs from the work of Seale et al 48 , and…”

Section: Grooming Behavior Grooming Was Commonly Observed In Halobatmentioning

confidence: 99%

Superhydrophobicity and size reduction enabled Halobates (Insecta: Heteroptera, Gerridae) to colonize the open ocean

Mahadik

Hernández-Sánchez

Arunachalam

et al. 2020

Sci Rep

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Despite the remarkable evolutionary success of insects at colonizing every conceivable terrestrial and aquatic habitat, only five Halobates (Heteroptera: Gerridae) species (~0.0001% of all known insect species) have succeeded at colonizing the open ocean-the largest biome on earth. this remarkable evolutionary achievement likely required unique adaptations for them to survive and thrive in the challenging oceanic environment. For the first time, we explore the morphology and behavior of an open-ocean Halobates germanus and a related coastal species H. hayanus to understand mechanisms of these adaptations. We provide direct experimental evidence based on high-speed videos which reveal that Halobates exploit their specialized and self-groomed body hair to achieve extreme water repellence, which facilitates rapid skating and plastron respiration under water. Moreover, the grooming behavior and presence of cuticular wax aids in the maintenance of superhydrophobicity. further, reductions of their body mass and size enable them to achieve impressive accelerations (~400 ms −2) and reaction times (~12 ms) to escape approaching predators or environmental threats and are crucial to their survival under harsh marine conditions. These findings might also inspire rational strategies for developing liquid-repellent surfaces for drag reduction, water desalination, and preventing bio-fouling. The proliferation of invertebrate taxa in the ocean during the Cambrian explosion eventually led to their colonization on land, where insects first appeared ~479 million years (Myr) ago 1 to eventually dominate various terrestrial ecosystems 2,3. With an estimated ~5.5 million extant species 4 , insects comprise 80% of all known metazoans, making them the dominant animals on Earth 5. Despite their successful colonization of both terrestrial and aquatic habitats, only a small number of insects (~0.5% of total species) have been found in marine environments, mostly in nearshore habitats, with only a handful of Halobates (~0.0001% of insect species) ultimately colonizing the open ocean, the largest biome on Earth 6-8. Halobates is a member of the family Gerridae, which evolved nearly 55 Myr ago 6,9. Some 48 species of Halobates are known to occur in tropical and subtropical seas and oceans that cover more than 70% of the Earth's surface. Most of these species are found in mangrove and near-shore habitats and two even live in freshwater, whereas five live on the surface of the open ocean. The fact that only a mere 0.0001% of insect species were able to colonize the largest habitat on Earth indicates that there must have been formidable environmental challenges for oceanic Halobates to overcome in order to live there. Halobates most likely evolved from an estuarine or mangrove ancestor that was washed out to the sea and became adapted to survive in the open ocean 8,10. Freshwater relatives of sea-skaters are often found on placid water bodies such as small ponds, lakes or slow-flowing streams, whereas many tropical species can be found

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“…By uncovering the physics behind the flight of the dandelion, we have discovered a novel type of fluid behaviour around fluid-immersed bodies. As filamentous microstructures within the relevant regimes (< 1 for the pore scale and about 100 − 1,000 for the body scale) are commonplace in the biological world 19,31,34 , we anticipate that permeability-dependent flow control is prevalent in nature. Traditionally, fluid dynamics investigations tend to observe a single scale; exploration of interplays among multiple regimes may uncover other as yet unknown fluid behaviour.…”

mentioning

confidence: 99%

A separated vortex ring underlies the flight of the dandelion

Cummins

Seale

Macente

et al. 2018

Nature

Self Cite

184

188

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Wind-dispersed plants have evolved ingenious ways to lift their seeds 1,2. The common dandelion uses a bundle of drag-enhancing bristles (pappus) to help keep their seeds aloft. This passive flight mechanism is highly effective, enabling seed dispersal over formidable distances 3,4 ; however, the engineering underpinning pappus-mediated flight remains unresolved. Here, we have visualized the flow around dandelion seeds, uncovering an extraordinary type of vortex. This vortex is a ring of recirculating fluid, which is detached due to the flow passing through the pappus. We hypothesized that the circular disk-like geometry and the porosity of the pappus are the key design features that enable the formation of the separated vortex ring. The porosity gradient was surveyed using microfabricated disks, and a disk with a similar porosity was found able to recapitulate the flow behaviour of the real pappus. The porosity of the dandelion's pappus appears to be tuned precisely to stabilize the vortex, while maximizing the aerodynamic loading and minimizing the material requirement. The discovery of the separated vortex ring signals the existence of a new class of fluid behaviour around fluid-immersed bodies that may underlie locomotion, weight reduction, and particle retention of biological and manmade structures. Dandelions (Taraxacum officinale agg.) are highly successful perennial herbs, which can be found in temperate zones all over the world 5. Dandelions, like many other members of the Asteraceae family, disperse their bristly seeds using the wind and convective updrafts 6,7. Most dandelion seeds likely land within 2 m 8,9 ; however, in warmer, drier and windier conditions, some may fly further (up to 20,000 seeds per hectare travelling more than 1 km by one estimate) 6,10. Asteraceae seeds routinely disperse over 30 km and occasionally even 150 km 3,4. Plumed seeds comprise a major class of dispersal strategies used by numerous and diverse groups of flowering plants, of which the common dandelion is a representative example. Plumed seeds contain a bundle of bristly filaments, called a pappus, which are presumed to function in drag enhancement (Fig. 1a-c). The pappus prolongs the descent of the seed, so that it may be carried farther by horizontal winds 11 , and it may also serve to orientate the seed as it falls 7,12. Dandelion seeds fall stably at a constant speed in quiescent conditions 2,13-15. For wind-dispersed seeds, maintaining stability while maximizing descent time in turbulent winds may be useful for long-distance dispersal 16,17. It is not clear, however, why plumed seeds have opted for a bristly pappus rather than a wing-like membrane, which is known to enhance lift in some other species (e.g., maples 1). Here, we uncover the flight mechanism of the dandelion, characterizing the fluid dynamics of the pappus and identifying the key structural features enabling its stable flight. To examine the flow behaviour around the pappus, we built a vertical wind tunnel (Fig. 1d, and M1), designed so that the seed ca...

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Design principles of hair-like structures as biological machines

Cited by 29 publications

References 180 publications

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

Superhydrophobicity and size reduction enabled Halobates (Insecta: Heteroptera, Gerridae) to colonize the open ocean

A separated vortex ring underlies the flight of the dandelion

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