Electropermanent magnet actuation for droplet ferromicrofluidics.

Area of Science:

• Microfluidics
• Magnetohydrodynamics
• Biotechnology

Background:

• Droplet actuation is crucial for microfluidic applications.
• Ferrofluid-based systems offer unique possibilities for droplet manipulation.
• Precise control of droplet movement is essential for various lab-on-a-chip applications.

Purpose of the Study:

• To investigate the use of electropermanent magnets (EPMs) for on-demand electromagnetic actuation of water droplets in ferrofluid microfluidics.
• To quantify the magnetic forces and droplet velocities generated by EPMs.
• To demonstrate droplet sorting capabilities using this actuation method.

Main Methods:

• Utilized electropermanent magnets (EPMs) to generate magnetic fields up to 50 mT and gradients up to 6.4 × 10^4 kA/m^2 in a ferrofluid-filled microchannel.
• Applied short current pulses (50 µs) to activate EPMs and induce magnetophoretic forces on water-in-ferrofluid droplets (40–80 µm).
• Employed a split-junction microfluidic design to demonstrate droplet sorting under continuous flow.

Main Results:

• Generated negative magnetophoretic forces ranging from 10 to 70 nN on the droplets.
• Achieved maximum droplet displacement velocities of up to 300 µm/s under both flow and no-flow conditions.
• Successfully demonstrated electropermanent magnet-activated droplet sorting in a continuous flow system.

Conclusions:

• EPMs provide an effective method for on-demand electromagnetic droplet actuation in ferrofluidic systems.
• The demonstrated technique allows for precise control over droplet displacement and sorting.
• This approach holds potential for advanced microfluidic applications requiring sophisticated droplet manipulation.