STIRRING IMMISCIBLE LIQUIDS IN NANOLITER CAVITIES

In this paper, we present immiscible liquid mixing within nanoliter droplet-based ‘cavities’ in microfluidic devices. In doing so, we create biphasic droplets with tunable internal structures, from near-equilibrium drop-in-drop morphologies to complex yet uniform non-equilibrium steady-state structures. The droplets contain an aqueous mixture of poly(ethylene glycol) (PEG) and dextran (DEX), and are injected into an immiscible oil in a simple microfluidic T-junction device. Aqueous droplets with tunable spatial heterogeneity in structure and composition could potentially be used to conduct in vitro biochemistry in environments that more closely emulate in vivo milieus than conventional macro or micro methods.