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.
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机译：液滴驱动是基于液滴的微流体系统的基本机制。在基于铁磁流体的微流体系统中使用按需电磁致动来置换水滴。永磁体（EPM）用于在铁磁流体填充的微通道中感应50 mT磁场，其梯度高达6.4×10 4 kA / m 2 。短的50 µs电流脉冲会激活永久磁铁，并在40至80 µm的铁磁水液滴上产生10至70 nN的负磁致变力。在流动和无流动条件下，最大液滴移动速度可达300 µm / s。使用分接缝微流体设计证明了在连续流下的电永磁励磁液滴分选。
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