This paper deals with the extraction from a meniscus of water droplets of small size into an immiscible insulating liquid by the use of a multistage voltage pulse. A previous study on a particular oil established that this EHD Drop-on-demand technique allows producing droplets of size smaller or much smaller than the needle diameter. The case of a dielectric liquid characterized by a rather high value of the water/oil interfacial tension is considered here. It is shown that by adequately modifying the shape and level of the multistage voltage pulse, droplets are produced with a diameter ranging over a large interval. It was expected that the short enough pulse duration would give electrically neutral droplets; in practice it is found that the droplets carry minute but nonzero charges. An explanation is given for the charging mechanism and other changes of the pulse shape allow to further minimize the droplets charge. Finally having in mind the possibility to investigate experimentally the electrocoalescence of two close drops, results are presented concerning the injection of two successive droplets.

本文涉及使用多级电压脉冲从弯液面中提取小尺寸的水滴到不混溶的绝缘液体中。先前对特定机油的研究表明，这种EHD按需滴落技术可以产生尺寸小于或小于针头直径的液滴。这里考虑以水/油界面张力的值较高为特征的介电液体的情况。结果表明，通过适当地改变多级电压脉冲的形状和电平，可以产生直径范围较大的液滴。预期足够短的脉冲持续时间将产生电中性的液滴。在实践中，发现液滴携带微小但非零的电荷。给出了带电机理的解释，并且脉冲形状的其他变化允许进一步减小液滴带电。最后，考虑到有可能通过实验研究两个紧密液滴的电聚结的可能性，给出了与两个连续液滴的注入有关的结果。