Milliseconds microfluidic chaotic bubble mixer

In this study, we report a rapid microfluidic mixing device based on chaotic advection induced by microbubble-fluid interactions. The device includes inlets for to-be-mixed fluids and nitrogen gas. A side-by-side laminar flow segmented by monodisperse microbubbles is generated when the fluids and the nitrogen are co-injected through a flow focusing micro-orifice. The flow subsequently enters a series of hexagonal expansion chambers, in which the hydrodynamic interaction among the microbubbles results in the stretch and fold of segmented fluid volumes and rapid mixing and homogenization. We characterize the performance of the microfluidic mixer and demonstrate rapid mixing within 20 ms. We further show that bubbles can be conveniently removed from the mixed fluids using a microfluidic comb structure on completion of the mixing.