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

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) fo...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-02, Vol.117 (6), p.2788-2794
Main Authors: Kant, Pallav, Koldeweij, Robin B. J., Harth, Kirsten, van Limbeek, Michiel A. J., Lohse, Detlef
Format: Article
Language:English
Subjects:
Cold surfaces
Droplets
Fluid dynamics
Fluid flow
Freezing
Hydrodynamics
Industrial applications
Inkjet printing
Kinetics
Morphology
Nucleation
Physical Sciences
Radiation
Solidification
Supercooling
Tin
Ultraviolet radiation
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Summary: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, totalinternal 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1912406117