2008 Volume 41 Issue 5 Pages 420-426
The breakup phenomena of large oil-in-water (O/W) emulsion droplets in silicon microchannel (MC) array devices at low applied pressures were investigated by microscopic and high-speed observations. This study used two sizes of MC arrays, each of which consisted of uniformly sized MCs, slit-like terraces, and deeply etched wells. Monodisperse feed O/W emulsion droplets that had entered the MC arrays were broken up into fine droplets primarily by snap-off that occurs due to localized shear inside the MCs and by pinch-off due to interfacial tension effects inside the MCs or on the inlet side of a terrace. The average droplet size of the permeate O/W emulsions depended significantly on the MC size and exceeded the MC size by 1.2 to 1.4 times. Their coefficients of variation were 18% to 21%. The results obtained from preceding work were compared with the results for direct generation of O/W emulsion droplets using the same MC array device.
