To observe hydrodynamics in microregions, we applied laser scanning manipulation to measure the drag acting on a fine glass bead moving in mineral oil sandwiched between two glass plates (the thickness of the oil layer was a 33 and 64 mu m). We measured the maximum velocity, V-M, of a laser trapped bead at which the bead was released. This allowed us to quantitatively determine the drag, the drag coefficient, C-D, and the Reynolds number, R, of the particle in the microregion of a viscous fluid. As a result, the minimum CDR was obtained midway between the two glass plates, and the CDR increased closer to the walls. Also, the distribution of CDR was in good agreement with the values calculated using the equation for wall effect in macroregions (over 0.1 mm).
Japanese Journal of Applied Physics: Part 1: Regular Papers, Short Notes and Review Papers,
Vol. 39, no. 4A (Apr 2000), pp. 1930-1933