Volume 86, Number 6, June 2009
Article Number 64001
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
Published online 01 July 2009
EPL, 86 (2009) 64001
DOI: 10.1209/0295-5075/86/64001

Life at high Deborah number

E. Lauga

Department of Mechanical and Aerospace Engineering, University of California San Diego 9500 Gilman Dr., La Jolla, CA 92093-0411, USA

received 20 April 2009; accepted in final form 29 May 2009; published June 2009
published online 1 July 2009

In many biological systems, microorganisms swim through complex polymeric fluids, and usually deform the medium at a rate faster than the inverse fluid relaxation time. We address the basic properties of such life at high Deborah number analytically by considering the small-amplitude swimming of a body in an arbitrary complex fluid. Using asymptotic analysis and differential geometry, we show that for a given swimming gait, the time-averaged leading-order swimming kinematics of the body can be expressed as an integral equation on the solution to a series of simpler Newtonian problems. We then use our results to demonstrate that Purcell's scallop theorem, which states that time-reversible body motion cannot be used for locomotion in a Newtonian fluid, breaks down in polymeric fluid environments.

47.63.Gd - Swimming microorganisms. - Low-Reynolds-number motions.
47.57.-s - Complex fluids and colloidal systems.

© EPLA 2009