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Technology (Singap World Sci). 2016 Jun;4(2):110-119. Epub 2016 May 13.

Electropermanent magnet actuation for droplet ferromicrofluidics.

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Department of Electrical Engineering, School of Engineering, Stanford University, Stanford, CA 94305, USA.
Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94305, USA.


Droplet actuation is an essential mechanism for droplet-based microfluidic systems. On-demand electromagnetic actuation is used in a ferrofluid-based microfluidic system for water droplet displacement. Electropermanent magnets (EPMs) are used to induce 50 mT magnetic fields in a ferrofluid filled microchannel with gradients up to 6.4 × 104 kA/m2. Short 50 µs current pulses activate the electropermanent magnets and generate negative magnetophoretic forces that range from 10 to 70 nN on 40 to 80 µm water-in-ferrofluid droplets. Maximum droplet displacement velocities of up to 300 µm/s are obtained under flow and no-flow conditions. Electropermanent magnet-activated droplet sorting under continuous flow is demonstrated using a split-junction microfluidic design.


Droplet Microfluidics; Droplet Sorting; Electropermanent Magnets; Ferrofluids; Ferromicrofluidics; Magnetic Actuation

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