Rapid microfluidic mixing via rotating magnetic microbeads

Presented here is a novel method for mixing in a microfluidic channel via an array of rotating magnetic microbeads. The microbeads rotate around circular permalloy (NiFe) features magnetized by a rotating external magnetic field. This system demonstrates rapid mixing in short channel lengths. The effectiveness of this system is quantified by analyzing the degree of mixing of two streams, one with fluorescence and one without. Our experiments and numerical simulations reveal that beads orbiting at a high velocity as compared to flow down the channel cause the fluid to form circular coronae that stretch across the microchannel leading to fluid mixing. Under these conditions, rotating magnetic microbeads were able to fully mix the streams in a 270 μm mixing region.