Non-coalescence of oppositely charged drops

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Original entry: Sujit S. Datta, APPHY 225, Fall 2009.

Reference

W. D. Risternpart, J. C. Bird, A. Belmonte, F. Dollar and H. A. Stone, Nature 461, 377 (2009).

Keywords

electric, droplet, coalescence

Key Points

The objective of this work was to study the coalescence behavior of water droplets (dispersed in oil) under the influence of an applied electric field. The experimental setup was simple: the bottom half of a container was filled with water and was electrically grounded, while the top half was filled with a poorly conducting oil, with an electrode inserted in the liquid. This allows an inhomogeneous electric field (of strength up to 100,000V/m) to be applied across the sample chamber. After this field is applied, a small water droplet is pipetted into the oil at the top of the chamber. Because the electric field is inhomogeneous, the droplet moves by dielectrophoresis towards the top electrode.