Controllable size and form of droplets in microfluidic-assisted devices: Effects of channel geometry and fluid velocity on droplet size.

Droplet-based microfluidic assisted devices have proposed an extensive interest in many applications such as lab-on-a-chip technologies as well as chemical/biological/nanomaterial preparation, chemical engineering, drug delivery, tissue engineering and biosensing. Here, a computational fluid dynamic model was developed for deep understanding of the droplet size and formation in a flow-focusing (FF) microchannel with consideration of the continuous phase (non-Newtonian fluid). The simulations presented an alternative method to achieve insights into this complicated process. In the following for the first time, the role of channel geometry, channel aspect ratio and flow rate ratio on droplet features including the mechanism of droplet formation, diameter/volume of droplet, velocity/amount of droplet formation, and final shape/size of the generated droplets were fully described. These findings could remarkably derive desirable protocols to control droplets characteristics comprising their size and shape in non-Newtonian fluids. Moreover, level set (LS) method was used for scrutinizing the droplet-breaking procedure in the microfluidic FF devices. The results showed that different droplet sizes could be prepared with changing the various parameters, demonstrating many challenges in various applications including lab-on-a-chip, cell encapsulation, drug delivery, tissue engineering, biosensing and bioimaging could be successfully addressed.