Ferrofluid Droplet Manipulations on an Electromicrofluidic Device
Ferrofluids, which are synthesized as a stable colloidal suspension of permanently magnetized particles such as magnetite of 10 nm diameter, are an excellent choice for micro/nanoelectromechanical system (MEMS/NEMS) field. Although magnetically actuated plugs of ferrofluids have been used to design microfluidic valves, pistons and pumps by many researchers, but rare research about manipulations of ferrofluid itself on electromicrofluidic platform have been done. We demonstrate fundamental studies of ferrofluid microdroplet manipulations by electrowetting on dielectric (EWOD), liquid dielectrophoresis (LDEP), and magnetic force. We choose water-based ferrofluid (EMG 700) and oil-based ferrofluid (EFH 1) produced by Ferrotec Corporation. The most optimal frequency and minimum required voltage to drive a droplet following the signal back and forth on the five driving electrodes for at least one cycle at different spacer and different surroundings are recorded. Besides, we manipulate three kinds of core-shell encapsulated droplets, water-core and oil-shell, water-based-ferrofluid-core and oil-shell, water-core and oil-based-ferrofluid-shell. And we pattern ferrofluid by designed electrode on ITO-glass chip. What’s more, we design spiral coils arrayed on PCB to generate local magnetic field, and manipulated ferrofluid droplets by magnetic force.