Abstract
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.
Highlights
Formation of liquid droplets in another immiscible fluid is important in emulsion, when the droplet size and size distribution can be controlled on a micro- or nano-scale [1]
When the dispersed-phase liquid passed through the terrace/microchannel, the emulsification exploits the interfacial tension, which is the dominating force on a micrometer scale, as the driving force for droplet formation
We have successfully demonstrated a new microfluidic chip capable of formation of micro-droplets in liquids using flow-focusing channels and a NC micro-valve
Summary
Formation of liquid droplets in another immiscible fluid is important in emulsion, when the droplet size and size distribution can be controlled on a micro- or nano-scale [1]. This technique for the emulsification process has been widely applied in several industries, including cosmetics, foods, Micromachines 2013, 4 paints and drugs [2]. The model based on the droplet formation mechanism and experimental observation in the microchannel array system was reported for predicting droplet diameters [10] These microchannel devices could generate micro-droplets successfully. A flow-focusing technique capable of controlling the size of micro-droplets in emulsion was reported [11]
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