Development of aqueous two-phase droplet-based microfluidic system

Abstract

In this study, the microfluidic system based on the aqueous two-phase system (ATPS) droplets has been developed. Microfluidics allows handling of tiny amount of fluids using channels with dimensions of tens to hundreds of micrometres. Droplets generated and manipulated in the microfluidic system can provide unique opportunities to handle fluids in a discrete manner, offering novel platform of miniaturized system for chemical and biological processes. The ATPS formed by tetrabutylammonium bromide (TABA) / ammonium sulfate (AS) is employed for the experimental study of the droplet-based microfluidic system in this study. The phase separation of TBAB/AS ATPS has been studied with the phase diagram and sulfate and bromide ion distribution. Properties of the two-phase system such as the interfacial tension and viscosity of the ATPS were used to expect the fluid dynamic behavior in the microfluidic system. The microextraction in the stratified laminar flow was carried out to demonstrate the transport of solute from one phase to the other. The design of microfluidic system and the operation conditions such as flow rate of each phase were determined for the microextraction. The distribution coefficient which indicates the equilibrium partition of solute between the two phases was calculated along with its pH dependency and showed the successful transport of the molecules. Generation of TBAB/AS ATPS droplets by electrohydrodynamic method was studied. Initially fed as laminar flows, the AS-rich phase was destabilized and eventually dispersed as droplets in the continuous TBAB-rich phase at the T-junction in the microfluidic system when the d. c. electric potential difference was applied as pulses. Based on the pH dependency of the threshold electric voltage required to generate a single droplet, the electrophoretic mobility of the AS-rich phase in TBAB-rich phase was discussed and a model for the mechanism was suggested. Applying the same electrohydrodynamic princi...