Physics of Fluids - Publications

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

arΧiv
Proceedings of the National Academy of Sciences 117, 2788–2794 (2020)

Authors

	Pallav Kant
	Robin Koldeweij
	Kirsten Harth
	Michiel van Limbeek
	Detlef Lohse

BibTeΧ

@article {Kant2788,
	author = {Kant, Pallav and Koldeweij, Robin B. J. and Harth, Kirsten and van Limbeek, Michiel A. J. and Lohse, Detlef},
	title = {Fast-freezing kinetics inside a droplet impacting on a cold surface},
	volume = {117},
	number = {6},
	pages = {2788--2794},
	year = {2020},
	doi = {10.1073/pnas.1912406117},
	publisher = {National Academy of Sciences},
	abstract = {From critically affecting the performance of an aircraft to droplet-based additive manufacturing, the solidification of impacting droplets influences a wide range of industrial applications; thus, a deeper fundamental understanding of the solidification of an impacting droplet is necessary. In this work, we reveal and rationalize a peculiar freezing morphology originating from the complex interplay between the droplet-scale hydrodynamics and phase-transition effects at sufficiently high substrate undercooling. The direct visualization of different freezing morphologies only became possible as we adopt an optical technique (TIR) in the context of freezing. This technique can be employed in more complex situations, such as solidification of an impacting droplet on liquid-infused or patterned surfaces, which potentially can influence many industrial processes.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{\textemdash}namely, total-internal reflection (TIR){\textemdash}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},
	URL = {https://www.pnas.org/content/117/6/2788},
	eprint = {https://www.pnas.org/content/117/6/2788.full.pdf},
	journal = {Proceedings of the National Academy of Sciences}
}