A new ac electrospray mechanism by Maxwell-Wagner polarization and capillary resonance.
We report a new high-frequency (>10 kHz) ac electrospray that is capable of generating micron-sized electroneutral drops. Unlike its dc counterpart, the drops are not ejected continuously from a sharp Taylor cone but intermittently from a resonating meniscus at the orifice. We attribute the resonant frequency to the capillary-inertia vibration time of the meniscus and the drop ejection to the Maxwell-Wagner electric stress at the drop tip, which is observed to reverse its direction across a crossover frequency. Above this frequency, the oppositely directed Maxwell-Wagner force causes the liquid to recede up the microneedle as an apparent electrowetting effect.
Yeo
Leslie Y
LY
Center for Microfluidics and Medical Diagnostics, Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Lastochkin
Dmitri
D
Wang
Shau-Chun
SC
Chang
Hsueh-Chia
HC