Ferrofluid dynamics in a Hele-Shaw cell simultaneously stressed by DC and rotating magnetic fields

Abstract

Earlier experiments have been repeated to evaluate magnetic fluid behavior in DC, AC and rotating magnetic fields. Understanding these behaviors are essential to the ferrohydrodynamic applications of ferrofluids in biomedicine. Careful measurements in Hele-Shaw cells with simultaneous perpendicular DC and in-plane rotating magnetic fields have shown that ferrofluid drop spiral patterns rotate in the same direction as the rotating magnetic field, independent of the polarity of the perpendicular DC magnetic field. This corrects inconsistencies in previously reported measurements. The large and heavy electromagnet and power supply used in earlier work were also replaced by a small permanent magnet assembly from MagswitchTM to still produce ferrofluid spirals and spontaneous self-assembling ferrofluid dot patterns.