(142bo) Diamagnetic Particle Trapping in Ferromicrofluidics

Concentrating particles to a detectable level is often necessary and critical in many areas such as environment monitoring, food safety, and water quality control. We present in this talk a magnetic method for trapping and concentrating particles in a continuous ferrofluid flow through a straight rectangular microchannel. A pair of attracting permanent magnets is embedded into the PDMS slab on the two sides of the microchannel to produce strong magnetic field gradients in the flow direction. As they are less magnetizable than the ferrofluid, diamagnetic particles are repelled away from the high magnetic field region and trapped in front of the magnets where the flow velocity is counterbalanced by the magnetophoretic particle velocity. We experimentally study how the effects of flow rate, location of each magnet, and particle size on the particle trapping performance by directly visualizing the particle behavior. We also develop an analytical model to simulate the particle transport and trapping in ferrofluid flows under the experimental conditions.