The trapping behavior of patterned micromagnets was investigated based on the parameters affecting superparamagnetic beads in microfluidic channels. Using replica molding and electroplating technologies, the micromagnets were fabricated on the microchannel bottom and generated sufficient magnetic gradients to bias the moments of superparamagnetic beads in a flowing stream. The calculated and experimental results revealed that both the magnetic force and the hydrodynamic drag force contributed to the rate of fluidic flow. The relative velocity of magnetic particles was dependent on the external magnetic field driven by an alternate current (AC) source at various frequencies. The magnetic gradient induced hysteresis characters of transmission spectrum, associating with the interaction of superparamagnetic beads and magnetic field. The device has potentials considering different possibilities of surface functionalisation and manipulation of super paramagnetic beads in microchannels.
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