Statistical Analysis of Droplet Charge Acquired during Contact with Electrodes in Strong Electric Fields
Statistical Analysis of Droplet Charge Acquired during Contact with Electrodes in Strong Electric Fields
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DOI：
10.1021/acs.langmuir.8b04254
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发表时间：
2019-03-19
期刊：
影响因子：
3.9
通讯作者：
Ristenpart, William D.
中科院分区：
文献类型：
--
作者：
Elton, Eric S.;Tibrewala, Yash V.;Ristenpart, William D.
当水滴在高压电场中接触电极时，它们会获得电荷。尽管许多研究人员已经研究了不同条件下液滴的电荷，但液滴电荷通常只是简单地用平均值和标准差来报道。在这里，我们表明，与之前和随后的接触相比，液滴在一次接触中通常获得的电荷要少得多。这些“低电荷事件”，在金属球充电时没有观察到，导致液滴获得的电荷减少高达60%，并且与施加的场强、液滴电导率或液滴体积无关。在这里检查的所有情况下，低电荷事件的发生近似地遵循负二项分布（即帕斯卡分布），平均概率为13%。我们进一步证明，大约16%的充电事件具有“不规则”泰勒锥动力学特征，这表明接近液体界面的电驱动变形的不稳定性可能是导致低电荷事件的原因。结果表明，使用液滴充电系统的工作人员应该考虑到液滴随机获得比预期更少的电荷的可能性。
Aqueous droplets acquire charge when they contact electrodes in high-voltage electric fields. Although many researchers have investigated droplet charging under various conditions, the droplet charges are typically reported simply in terms of a mean and standard deviation. Here, we show that droplets often acquire significantly less charge for a single contact compared to the previous and subsequent contacts. These "low-charge events," which are not observed with charging of metal balls, yield up to a 60% decrease in charge acquired by the droplet and occur regardless of the applied field strength, droplet conductivity, or droplet volume. In all cases examined here, the occurrence of low-charge events to good approximation follows a negative binomial distribution (i.e., a Pascal distribution) with a mean probability of 13%. We further demonstrate that approximately 16% of charging events are characterized by "irregular" Taylor cone dynamics, suggesting that instabilities in the electrically driven deformation of the approaching liquid interface may be responsible for the low-charge events. The results indicate that workers using systems involving droplet charging should take into account the high likelihood of droplets randomly acquiring less charge than expected.