A microfluidic mixer based on parallel, high-speed circular motion of individual microbeads in a rotating magnetic field

A new magnetic micromixer based on parallel manipulation of individual magnetic microbeads attracted to soft ferromagnetic microdiscs integrated in microchannels is demonstrated. An external rotating magnetic field was constructed to induce synchronized circular motion of individual magnetic beads around the soft magnets in an array, thereby generating secondary flow in the form of local vortices across the microchannel. A theoretical basis was developed for determining the effectiveness of the magnetic mixer, and was verified by experimental results. Surprisingly large angular velocities of the microbeads, i.e., in the order of 1000 rad/sec, were demonstrated in our relatively simple system, leading to extremely effective microfluidic mixing results.