Critical angle for electrically driven coalescence of two conical droplets

James C. Bird, William D. Ristenpart, Andrew Belmonte, Howard A. Stone

Research output: Contribution to journalArticlepeer-review

127 Scopus citations


Oppositely charged drops attract one another and, when the drops are sufficiently close, electrical stresses deform the leading edges of each drop into cones. We investigate whether or not the liquid cones coalesce immediately following contact. Using high-speed imaging, we find that the coalescence behavior depends on the cone angle, which we control by varying the drop size and the applied voltage across the drops. The two drops coalesce when the slopes of the cones are small, but recoil when the slopes exceed a critical value. We propose a surface energy model (volume-constrained area minimization) to describe the transition between these two responses. The model predicts a critical cone angle of 30.8°, which is in good agreement with our measurements.

Original languageEnglish (US)
Article number164502
JournalPhysical review letters
Issue number16
StatePublished - Oct 16 2009

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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