Yeo Leslie Y, Lastochkin Dmitri, Wang Shau-Chun, Chang Hsueh-Chia
Center for Microfluidics and Medical Diagnostics, Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Phys Rev Lett. 2004 Apr 2;92(13):133902. doi: 10.1103/PhysRevLett.92.133902. Epub 2004 Apr 1.
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.
我们报道了一种新型高频（>10 kHz）交流电喷雾，它能够产生微米级的电中性液滴。与直流电喷雾不同，这些液滴不是从尖锐的泰勒锥连续喷出，而是从孔口处共振的弯月面间歇性喷出。我们将共振频率归因于弯月面的毛细管惯性振动时间，而液滴喷射归因于液滴尖端的麦克斯韦-瓦格纳电应力，观察到该电应力在一个交叉频率处会反转其方向。高于此频率，方向相反的麦克斯韦-瓦格纳力会使液体作为一种明显的电润湿效应沿微针向上退缩。
