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Micromachines 2013, 4(3), 306-320;

Formation of Tunable, Emulsion Micro-Droplets Utilizing Flow-Focusing Channels and a Normally-Closed Micro-Valve

Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan
Author to whom correspondence should be addressed.
Received: 13 June 2013 / Revised: 7 July 2013 / Accepted: 8 July 2013 / Published: 17 July 2013
(This article belongs to the Collection Lab-on-a-Chip)
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A mono-dispersed emulsion is of great significance in many chemical, biomedical and industrial applications. The current study reports a new microfluidic chip capable of forming tunable micro-droplets in liquids for emulsification applications. It can precisely generate size-tunable, uniform droplets using flow-focusing channels and a normally-closed valve, which is opened by a pneumatic suction force. Experimental data showed that micro-droplets with a diameter ranging from several to tens of micrometers could be precisely generated with a high uniformity. The droplet size is experimentally found to be dependent on the velocity of the dispersed-phase liquid, which is controlled by the deflection of the suction membrane. Emulsions with droplet sizes ranging from 5.5 to 55 μm are successfully observed. The variation in droplet sizes is from 3.8% to 2.5%. The micro-droplets have a uniform size and droplets smaller than those reported in previous studies are possible with this approach. This new microfluidic device can be promising for emulsification and other related applications. View Full-Text
Keywords: microfluidics; emulsification; normally-closed valve; suction force microfluidics; emulsification; normally-closed valve; suction force

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Wang, J.-H.; Lee, G.-B. Formation of Tunable, Emulsion Micro-Droplets Utilizing Flow-Focusing Channels and a Normally-Closed Micro-Valve. Micromachines 2013, 4, 306-320.

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