THREE-DIMENSIONAL HYDRO-MAGNETIC FOCUSING OF SUPERPARAMAGNETIC BEADS

We present magneto-microfluidic three-dimensional focusing of magnetic microparticles from a dense plug into a single streamline with longitudinal inter-particle spacing. Plug formation is induced by a high-gradient magnetic field generated at the sidewall of a microchannel by a micromachined magnetic tip that is connected to an electromagnet. Controlled release of the microparticles is achieved using an exponential damping protocol of the magnetic retention force in the presence of an applied flow. Adding subsequently a lateral sheath flow microchannel focuses the microparticles into a single stream situated within ± 5 µm from the channel center axis.