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Fluid Dynamics Seminar

Monday, April 19, 2010, 4:00 PM
Cullimore Hall 611
New Jersey Institute of Technology

Rotation-translation coupling strategies for artificial low Reynolds number propulsion

Eric Keaveny

Courant Institute of Mathematical Sciences, New York University

Abstract

Swimming strategies at low Reynolds number are restricted by kinematic reversibility. One effective mechanism, which is utilized by many bacteria, is the rotation of helical flagella whose hydrodynamic mobility matrix couples rotation and translation. The use of such rotation-translation coupling has also been shown to be effective in artificial systems. In this talk, I will discuss two such cases. The first case is an artificial micro-swimmer constructed from a filament of paramagnetic beads connected to a human red blood cell. The original experiments demonstrated swimming under the influence of an applied oscillating magnetic field resulting from the propagation of bending waves along the length of the filament. Using simulations and theoretical analysis, we propose and investigate the kinematics of an alternative actuation strategy based on rotating magnetic fields where the swimmer deforms into a cork-screw-like shape and spirals its way though the fluid. In the second case, we study the hydrodynamic mobility of rigid, self-assembled colloidal clusters with chiral symmetry. The building blocks of these aggregates are doublets of two micron-scale beads of different radii bonded together by a magnetic cement. Our calculations indicate that for larger values of the size ratio of the beads, the coupling between rotations and translations changes sign as the number of doublets in the aggregate increases.