The microfluidic Kelvin water dropper
Abstract
The so-called "Kelvin water dropper" is a simple experiment demonstrating the spontaneous appearance of induced free charge in droplets emitted through a tube. As Lord Kelvin explained, water droplets spontaneously acquire a net charge during detachment from a faucet due to the presence of electrical fields in their surrounding created by any metallic object. In his experiment, two streams of droplets are allowed to drip from separated nozzles into separated buckets, which are at the same time interconnected through the dripping needles. In this paper we build a microfluidic water dropper and demonstrate that the droplets get charged and break-up due to electrohydrodynamic instabilities. A comparison with recent simulations shows the dependence of the acquired charge in the droplets on different parameters of the system. The phenomenon opens a door to cheap and accessible transformation of pneumatic pressure into electrical energy and to an enhanced control in microfluidic and biophysical manipulation of capsules, cells and droplets via self-induced charging of the elements.
Cite
@article{arxiv.1309.2866,
title = {The microfluidic Kelvin water dropper},
author = {Alvaro G. Marin and Wim van Hoeve and Pablo García-Sánchez and Lingling Shui and Yanbo Xie and Marco A. Fontelos and Jan C. T. Eijkel and Albert van den Berg and Detlef Lohse},
journal= {arXiv preprint arXiv:1309.2866},
year = {2013}
}
Comments
Accepted for publication as communication in Lab on a Chip (RSC)