9
January 2003
Microdroplets: Rayleigh round
A liquid droplet tends towards the spherical because of the surface tension of the liquid. But if a droplet becomes electrically charged—as in an ink-jet printer or in thunderclouds for instance—electrostatic repulsion between ions can overcome the surface tension, causing it to break up. An upper estimate for the charge in a droplet is given by a formula known as the Rayleigh limit, and the fine spray that then forms is known as a Rayleigh jet. High-speed microscopy has now been used to examine the dynamics of the disintegration of levitated charged water droplets, and the images obtained confirm Lord Rayleigh's prediction, made in 1892 without the aid of sophisticated microscopy, that the droplet becomes ellipsoid as a first step towards disintegration. But some of Rayleigh's other predictions are stretched to breaking point.
Coulomb fission: Rayleigh jets from levitated microdroplets
DENIS DUFT, TOBIAS ACHTZEHN, RENE MÜLLER, BERND A. HUBER &
THOMAS LEISNER
Nature 421, 128 (2003); doi:10.1038/421128a
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