Effect of dispersed phase viscosity on maximum droplet generation frequency in microchannel emulsification using asymmetric straight-through channels
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Uniformly sized droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and n-tetradecane with a Sauter mean diameter of d (3,2) = 26-35 mu m and a distribution span of 0.21-0.25 have been produced at high throughputs using a 24 x 24 mm silicon microchannel plate consisting of 23,348 asymmetric channels fabricated by photolithography and deep reactive ion etching. Each channel consisted of a 10-mu m diameter straight-through micro-hole with a length of 70 mu m and a 50 x 10 mu m micro-slot with a depth of 30 mu m at the outlet of each channel. The maximum dispersed phase flux for monodisperse emulsion generation increased with decreasing dispersed phase viscosity and ranged from over 120 L m(-2) h(-1) for soybean oil to 2,700 L m(-2) h(-1) for n-tetradecane. The droplet generation frequency showed significant channel to channel variations and increased with decreasing viscosity of the dispersed phase. For n-tetradecane, the maximum mean droplet generation frequency was ...250 Hz per single active channel, corresponding to the overall throughput in the device of 3.2 million droplets per second. The proportion of active channels at high throughputs approached 100% for soybean oil and MCT oil, and 50% for n-tetradecane. The agreement between the experimental and CFD (Computational Fluid Dynamics) results was excellent for soybean oil and the poorest for n-tetradecane.
Keywords:Microchannel emulsification / Membrane emulsification / Single crystal silicon microchannel array / Droplet generation frequency / Monodisperse droplets
Source:Microfluidics and Nanofluidics, 2011, 10, 6, 1199-1209
- Japan Society for the Promotion of Science, Tokyo [L-05555], Ministry of Agriculture, Forestry and Fisheries of Japan