Impact of electrode design and voltage waveform on low-potential magnetohydrodynamic fluid actuation

Abstract

Magnetohydrodynamic actuation of millimetric aqueous sodium chloride droplet samples is achieved using annular copper electrodes and PID control to stay below the electrolysis activation potential. The effects of electrode design, potential wave form shape, and frequency on current and liquid velocity are investigated. A difference is observed between steady-state forward- and reverse-bias currents and is attributed to the difference in cathodic surface area. Both forward-bias and reverse-bias currents are shown to increase with frequency as a result of the charging and discharging droplet capacitance. Although larger cathodic surface areas lead to larger currents, increased shear forces at the electrodes can counteract the increased MHD force and limit the droplet velocities.