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Molecular physics of jumping nanodroplets
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Perumanath, Sreehari, Borg, Matthew K., Sprittles, James E. and Enright, Ryan (2020) Molecular physics of jumping nanodroplets. Nanoscale, 12 (40). pp. 20631-20637. doi:10.1039/D0NR03766D ISSN 2040-3364.
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Official URL: http://dx.doi.org/10.1039/D0NR03766D
Abstract
Next-generation processor-chip cooling devices and self-cleaning surfaces can be enhanced by a passive process that require little to no electrical input, through coalescence-induced nanodroplet jumping. Here, we describe the crucial impact thermal capillary waves and ambient gas rarefaction have on enhancing/limiting the jumping speeds of nanodroplets on low adhesion surfaces. By using high-fidelity non-equilibrium molecular dynamics simulations in conjunction with well-resolved volume-of-fluid continuum calculations, we are able to quantify the different dissipation mechanisms that govern nanodroplet jumping at length scales that are currently difficult to access experimentally. We find that interfacial thermal capillary waves contribute to a large statistical spread of nanodroplet jumping speeds that range from 0 - 30 m/s, where the typical jumping speeds of micro/millimeter sized droplets are only up to a few m/s. As the gas surrounding these liquid droplets is no longer in thermodynamic equilibrium, we also show how the reduced external drag leads to increased jumping speeds. This work demonstrates that, in the viscous-dominated regime, the Ohnesorge number and viscosity ratio between the two phases alone are not sufficient, but that the thermal fluctuation number (Th) and the Knudsen Number (Kn) are both needed to recover the relevant molecular physics at nanoscales. Our results and analysis suggest that these dimensionless parameters would be relevant for many other free-surface flow processes and applications that operate at the nanoscale.
| Item Type: | Journal Article | ||||||||||||||||||
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| Subjects: | Q Science > QC Physics | ||||||||||||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Mathematics | ||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | Molecular structure -- Mathematics, Nanostructures, Surface energy | ||||||||||||||||||
| Journal or Publication Title: | Nanoscale | ||||||||||||||||||
| Publisher: | Royal Society of Chemistry | ||||||||||||||||||
| ISSN: | 2040-3364 | ||||||||||||||||||
| Official Date: | 28 October 2020 | ||||||||||||||||||
| Dates: |
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| Volume: | 12 | ||||||||||||||||||
| Number: | 40 | ||||||||||||||||||
| Page Range: | pp. 20631-20637 | ||||||||||||||||||
| DOI: | 10.1039/D0NR03766D | ||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||
| Access rights to Published version: | Restricted or Subscription Access | ||||||||||||||||||
| Date of first compliant deposit: | 31 July 2020 | ||||||||||||||||||
| Date of first compliant Open Access: | 22 July 2021 | ||||||||||||||||||
| Grant number: | EP/N016602/1, EP/P020887/1, EP/P031684/1, EP/S029966/1 and | ||||||||||||||||||
| RIOXX Funder/Project Grant: |
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