Monodispersed polygonal water droplets in microchannel

Abstract

The fabrication, motion and behavior of small droplets are subjects under considerable current study. The possible applications include using droplets as actuators to enhance mixing, as chemical reactors and the formation of emulsions. Microfluidics provides a convenient means of producing droplets at the micro scale. The study is currently dominated by spherical systems where droplets are consistently spherical in nature. Various methods and geometries have been tested for fabricating these droplets but little research has been conducted towards producing non-circular droplets. While the fabrication of non-spherical droplets has been reported before control over their shape remains difficult to achieve. In this thesis, we present a method to fabricate droplets using shear focusing in an oil medium alternatively from two channels facing each other. The droplets produced are non-circular in shape, and their shape dynamically alters as they travel in the microfluidic channel. The size of the droplets can be controlled by the ratio of oil and water flow rates. Microscopic images have been presented that show the non-spherical shape of the droplets at the point of fabrication. Images taken at two points further along the microfluidic channel show how the shapes of these droplets change as they travel in the channel. There were three regimes of droplet shapes, circular, triangular and rectangular shapes that were determined by the packing ratio of water droplet in oil phase in microfluidic channels. All droplets formed in this experiment were monodispersed.