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  • Book
    Katherine Lin Tsai.
    Digital2010
    Lab-on-a-Chip devices are attractive for medical diagnostics due to their ability to perform laboratory tasks on small scales. This manuscript explores magnetic nanoparticle-based technologies for low-power, remote actuation in Lab-on-a-Chip systems. Two specific applications -- microfluidic pumping and cell separation -- are investigated. First, chemistry-independent microfluidic pumping using magnetic nanoparticles suspended within a fluid has been demonstrated. Magnetic circuits to generate magnetic field gradients for actuating superparamagnetic nanoparticles in fluids have been fabricated, and changes in fluid velocities when the magnetic circuits are applied have been measured. Results show that the fluid velocity in a microchannel increases 30 [mu]m/sec when a magnetic field gradient of ~3 T/m is applied, and 10 -- 70 [mu]m/sec when a magnetic field gradient of ~5 T/m is applied. The magnetic, optical, and mechanical properties of a magnetic polymer that is composed of SU-8 polymer embedded with nickel nanoparticles (SU8-Ni) have also been characterized. Results show the SU8-Ni composites exhibit weak ferromagnetic behavior and saturate at magnetic fields around 0.2 T, the transmittance of light through SU8-Ni decreases with increasing Ni concentrations, and SU8-Ni has a Young's modulus that is 30 times lower and a hardness that is 1400 times lower than that of bulk Ni. A torsional microactuator made of SU8-Ni has been fabricated to demonstrate its use for magnetic actuation, and a model of the SU8-Ni based on deflection experiments of the actuator has been developed. Micropillars made of SU8-Ni have been fabricated for capturing and concentrating breast cancer cells in microchannels. Magnetic field gradients up to 10,000 T/m have been predicted for an SU8-Ni pillar that is 100 [mu]m tall, 100 [mu]m in diameter, and composed of 12.5% Ni by weight. Experimental results show the SU8-Ni micropillars capture magnetic bead-bound cells when an external magnet is applied and release the cells when the magnet is removed.