Fast-freezing kinetics inside a droplet impacting on a cold surface

Pallav Kant*, Robin B.J. Koldeweij, Kirsten Harth, Michiel A.J. van Limbeek, Detlef Lohse*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Freezing or solidification of impacting droplets is omnipresent in nature and technology, be it a rain droplet falling on a supercooled surface; in inkjet printing, where often molten wax is used; in additive manufacturing or metal-production processes; or in extreme ultraviolet lithography (EUV) for the chip production, where molten tin is used to generate the EUV radiation. For many of these industrial applications, a detailed understanding of the solidification process is essential. Here, by adopting an optical technique in the context of freezing—namely, total-internal reflection (TIR)—we elucidate the freezing kinetics during the solidification of a droplet while it impacts on an undercooled surface. We show that at sufficiently high undercooling, a peculiar freezing morphology exists that involves sequential advection of frozen fronts from the center of the droplet to its boundaries. This phenomenon is examined by combining elements of classical nucleation theory to the large-scale hydrodynamics on the droplet scale, bringing together two subfields which traditionally have been quite separated. Furthermore, we report a self-peeling phenomenon of a frozen splat that is driven by the existence of a transient crystalline state during solidification.

Original languageEnglish
Pages (from-to)2788-2794
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number6
Early online date24 Jan 2020
DOIs
Publication statusPublished - 11 Feb 2020

Keywords

  • Classical nucleation theory
  • Crystal growth
  • Droplet impact
  • Phase change
  • Solidification

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