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(abstract)In the insect realm, liquids become traps due to capillary and viscous forces dominant at their scale. Yet, aphids eliminate the highly viscous honeydew droplets that they secrete, by coating them with hydrophobic wax powder which maintains an air layer between their body and the sticky liquid. These low-adhesion, highly mobile coated droplets, known as liquid marbles, enable manipulation of small liquid volumes which is useful in applications such as biomedical analysis where samples volume is limited, chemistry to reduce chemical waste, or digital microfluidics for large-scale cell culturing and drug testing. Despite numerous applications, the physical properties of liquid marbles remain largely unexplored. This article addresses the fundamental question of the stability and adhesion of hot liquid marbles on cooler substrates. We find that due to the temperature difference, condensation forms within the particle layer, eventually bridging the core liquid with the substrate where wettability then plays a role. Hot liquid marbles rupture on hydrophilic substrates but remain intact on hydrophobic ones; however, their adhesion increases with temperature difference due to increased liquid bridge density. This non-wetting failure, rupture and increased adhesion, can be suppressed by increasing the particles size, decreasing the liquid volatility or using superhydrophobic substrates.
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Keyword: Liquid marble, Hot droplet, Cassie Wenzel transition
Date published: 2025-05-20
Publisher: The Proceedings of the National Academy of Sciences (PNAS)
Journal:
- PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA (ISSN: 10916490) vol. 122 issue. 20
Funding:
Manuscript type: Author's version (Accepted manuscript)
MDR DOI: https://doi.org/10.48505/nims.5474
First published URL: https://doi.org/10.1073/pnas.2500619122
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Updated at: 2025-05-14 12:30:13 +0900
Published on MDR: 2025-05-14 12:21:24 +0900