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Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Feb;79(2 Pt 2):026301. Epub 2009 Feb 2.

Comparison of Faxén's correction for a microsphere translating or rotating near a surface.

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Department of Physics and Astronomy, University of Glasgow, Glasgow, Scotland.


Boundary walls in microfluidic devices have a strong influence on the fluid flow and drag forces on moving objects. The Stokes drag force acting on a sphere translating in the fluid is increased by the presence of a neighboring wall by a factor given by Faxén's correction. A similar increase in the rotational drag is expected when spinning close to a wall. We use optical tweezers to confirm the translational drag correction and report the hitherto unmeasured rotational equivalent. We find that the corrections for the rotational motion is only required for particle-wall separations an order of magnitude shorter than that for the translational cases. These results are particularly significant in the use of optical tweezers for measuring viscosity on a picolitre scale.


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