Ejection of Uniform Micrometer-Sized Droplets from Faraday Waves on a Millimeter-Sized Water Drop

Abstract

This Letter reports the first observation and theoretical analysis of a new phenomenon: one large spherical water drop ejecting simultaneously a very large number of monodisperse microdroplets. An ultrasonic nozzle with multiple-Fourier horns in resonance enables controlled excitation of megahertz Faraday waves on the free water surface. The temporal instability of such waves leads to the ejection of 3.5-4.4 μm monodisperse droplets at a high rate (>4.0×10(7) droplets/sec). This is in stark contrast to the Rayleigh-Plateau instability, which ejects one droplet at a time.