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Published on: May 20, 2014
In-Plane Rotation of Prolate Colloids Adhered to a Planar Substrate in the Presence of Flow
Ran Ran1, Jianfeng Sun1, Sinan Müftü1
1Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, United States.
Abstract:
Micron-size spherical polystyrene colloidal particles are mechanically stretched to a prolate geometry with desirable aspect ratios. The particles in an aqueous medium with specific ionic concentration are then introduced into a microchannel and allowed to settle on a glass substrate. In the presence of unidirectional flow, the loosely adhered particles in the secondary minimum of surface interaction potential are easily washed off, but the remnant in the strong primary minimum preferentially aligns with the flow direction and exercises in-plane rotation. A rigorous theoretical model is constructed to account for filtration efficiency in terms of hydrodynamic drag, intersurface forces, reorientation of prolate particles, and their dependence on flowrate and ionic concentration.
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