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Ind. Eng. Chem. Res. 2005, 44, 5852-5856
Production of Monodisperse Oil-in-Water Emulsions Using a Large Silicon Straight-Through Microchannel Plate Isao Kobayashi,†,‡,§ Sukekuni Mukataka,‡ and Mitsutoshi Nakajima*,† National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1, Tennoudai, Tsukuba, Ibaraki 305-8577, Japan, and Japan Society for the Promotion of Science, 6 Ichibancho, Chiyoda-ku, Tokyo 102-8471, Japan
Straight-through microchannel (MC) emulsification is a promising and novel technique for producing monodisperse emulsions. A straight-through MC is a channel array microfabricated vertically to the surface of a silicon plate. We investigated the throughput capacity of monodisperse oil-in-water (O/W) emulsion droplets for a silicon straight-through MC plate with a size of 40 × 40 × 0.4 mm, developed in this study. Oblong channels used in this study had a longer line of 26.7 µm, a shorter line of 6.6 µm, and a depth of 100 µm. Monodisperse O/W emulsions with average droplet diameters of 31-32 µm and coefficients of variation below 10% were successfully produced using the large straight-through MC plate. The straight-through MC emulsification device had maximum throughput capacities of monodisperse emulsion droplets of 20-30 mL/h for the system containing refined soybean oil and of 60-70 mL/h for the system containing silicone oil. Introduction Emulsification is an important process applied in the food, cosmetics, pharmaceutical, and chemical industries. Monodisperse emulsions with a typical coefficient of variation (CV, (standard deviation/average droplet diameter (dav)) × 100)) less than 10% have received a great deal of attention in both the scientific and the industrial fields. Monodisperse emulsions can improve emulsion stability, and their physical, physicochemical, and organoleptic properties can be analyzed and controlledmoreclearlythanthoseofpolydisperseemulsions.1-4 However, traditional emulsification devices such as dispersing machines, colloid mills, and high-pressure homogenizers usually produce polydisperse emulsions.5,6 Significant advances in emulsification devices have been made in the past decade to produce monodisperse emulsions. Shear-rupturing of polydisperse viscous droplets in an injection couette mixer can produce quasimonodisperse emulsions.7 Monodisperse emulsions with a minimum CV value of 10% can be produced by membrane emulsification.8-10 Size-controlled emulsion droplets are formed by forcing the to-be-dispersed phase into the continuous phase through microporous membranes with different average pore sizes.8,11 Membrane emulsification applies energy input and shear stress lower than the traditional emulsification devices.12 Monodisperse emulsion droplets with a CV value below 10% can be formed by microchannel (MC) emulsification using a channel array with a slit-like terrace microfabricated on a silicon plate.13 The resultant droplet size can be primarily controlled by MC geometry.14,15 MC emulsification, in which droplet formation exploits interfacial tension, does not apply any external shear stress at very low energy input.16 * To whom correspondence should be addressed. Tel: +8129-838-8014. Fax: +81-29-838-7996. E-mail:
[email protected]. † National Food Research Institute. ‡ University of Tsukuba. § Japan Society for the Promotion of Science.
We recently proposed straight-through MC emulsification17 as a solution for the low-throughput of monodisperse emulsion droplets (
