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Viscous entrainment on hairy surfaces

Alice Nasto, P.-T. Brun, and A. E. Hosoi
Phys. Rev. Fluids 3, 024002 – Published 7 February 2018
Physics logo See Synopsis: How Hairy Tongues Help Bats Drink Nectar

Abstract

Nectar-drinking bats and honeybees have tongues covered with hairlike structures, enhancing their ability to take up viscous nectar by dipping. Using a combination of model experiments and theory, we explore the physical mechanisms that govern viscous entrainment in a hairy texture. Hairy surfaces are fabricated using laser cut molds and casting samples with polydimethylsiloxane (PDMS) elastomer. We model the liquid trapped within the texture using a Darcy-Brinkmann-like approach and derive the drainage flow solution. The amount of fluid that is entrained is dependent on the viscosity of the fluid, the density of the hairs, and the withdrawal speed. Both experiments and theory reveal an optimal hair density to maximize fluid uptake.

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  • Received 6 July 2017

DOI:https://doi.org/10.1103/PhysRevFluids.3.024002

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Synopsis

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How Hairy Tongues Help Bats Drink Nectar

Published 7 February 2018

Experiments and theory show that hairs on a bat’s tongue allow the animal to drink 10 times more nectar than it could if its tongue were smooth.

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Authors & Affiliations

Alice Nasto1, P.-T. Brun2, and A. E. Hosoi1,2

  • 1Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 2Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

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Issue

Vol. 3, Iss. 2 — February 2018

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