Thermally induced effects for droplet-based microfluidics

In recent years, the emergence of droplet-based microfluidics has brought new life to microfluidics technologies. Researchers have demonstrated the potential of droplet-based microfluidics in addressing issues encountered by the current continuous flow microfluidics especially in the area of analytical chemistry for lab-on-chip applications. This dissertation will, first, review the various droplet forming techniques and their underlying physics. Control and manipulation of droplets in microchannel will also be discussed. A class of fluids, which is referred to as functional fluid, will be introduced. These are fluids which have been reported to enhance the performance of microfluidic devices with their unique properties. To accelerate the understanding of droplet formation under various hydrodynamic flow conditions and operating environment, numerical modeling will be an economical tool to supplement conventional experimental approach. In this dissertation, a numerical model is developed to assist the study of droplet formation in a T-junction geometry. The model is successfully validated with experimental data and correlates well to the response of a temperature mediated T-junction geometry where the viscosities of the fluids are induced to vary accordingly. In the final part of the dissertation, the model is further extended to investigate the thermocoalescence of droplet in a microchannel geometry which consists of a non-temperature controlled droplet formation section of the similar T-junction geometry cascaded to a temperature-induced merging chamber. The validated model will pave the path for our future work on droplet-based microfluidic research such as the investigation of droplet formation and coalescent with a non-Newtonian or functional fluid in which their fluid properties can induce to change according to the external perturbation they are subjected to.DOCTOR OF PHILOSOPHY (MAE