Bouncing microdroplets on hydrophobic surfaces

Jamie McLauchlan; Jim S. Walker; Vatsal Sanjay; Maziyar Jalaal; Jonathan P. Reid; Adam M. Squires; Anton Souslov

doi:10.1073/pnas.2507309122

Bouncing microdroplets on hydrophobic surfaces

Jamie McLauchlan, Jim S. Walker, Vatsal Sanjay, Maziyar Jalaal, Jonathan P. Reid, Adam M. Squires, Anton Souslov

Research output: Contribution to journal › Article › peer-review

Abstract

Intuitively, slow droplets stick to a surface and faster droplets splash or bounce. However, recent work suggests that on nonwetting surfaces, whether microdroplets stick or bounce depends only on their size and fluid properties, but not on the incoming velocity. Here, we show using theory and experiments that even poorly wetting surfaces have a velocity-dependent criterion for bouncing of aqueous droplets, which is as high as 6 m/s for diameters of 30 to 50 μm on hydrophobic surfaces such as Teflon. We quantify this criterion by analyzing the interplay of dissipation, surface adhesion, and incoming kinetic energy, and describe a wealth of associated phenomena, including air bubbles and satellite droplets. Our results on inertial microdroplets elucidate fundamental processes crucial to aerosol science and technology.

Original language	English
Article number	e2507309122
Journal	Proceedings of the National Academy of Sciences
Volume	122
Issue number	36
Early online date	4 Sept 2025
DOIs	https://doi.org/10.1073/pnas.2507309122
Publication status	Published - 9 Sept 2025

Data Availability Statement

All study data are included in the article and/or supporting information.

Acknowledgements

We gratefully acknowledge the Engineering and Physical Sciences Research Council Centre for Doctoral Training in Aerosol Science (Grant No. EP/S023593/1) and the University of Bath Department of Chemistry for funding, Sara Dale for useful discussions and for help with Atomic Force Microscopy measurements of the nanoparticle-coated surface, as well as Lukesh Mahato, Lauren McCarthy, and Aditya Jha for fruitful discussions.

Funding

We gratefully acknowledge the Engineering and Physical Sciences Research Council Centre for Doctoral Training in Aerosol Science (Grant No. EP/S023593/1) and the University of Bath Department of Chemistry for funding, Sara Dale for useful discussions and for help with Atomic Force Microscopy measurements of the nanoparticle-coated surface, as well as Lukesh Mahato, Lauren McCarthy, and Aditya Jha for fruitful discussions.

Funders	Funder number
Department of Chemistry, University of York
Engineering and Physical Sciences Research Council	EP/S023593/1

Keywords

droplet
microfluidics
aerosols
bouncing
deposition

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10.1073/pnas.2507309122Licence: CC BY

Cite this

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AU - McLauchlan, Jamie

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AU - Souslov, Anton

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N2 - Intuitively, slow droplets stick to a surface and faster droplets splash or bounce. However, recent work suggests that on nonwetting surfaces, whether microdroplets stick or bounce depends only on their size and fluid properties, but not on the incoming velocity. Here, we show using theory and experiments that even poorly wetting surfaces have a velocity-dependent criterion for bouncing of aqueous droplets, which is as high as 6 m/s for diameters of 30 to 50 μm on hydrophobic surfaces such as Teflon. We quantify this criterion by analyzing the interplay of dissipation, surface adhesion, and incoming kinetic energy, and describe a wealth of associated phenomena, including air bubbles and satellite droplets. Our results on inertial microdroplets elucidate fundamental processes crucial to aerosol science and technology.

AB - Intuitively, slow droplets stick to a surface and faster droplets splash or bounce. However, recent work suggests that on nonwetting surfaces, whether microdroplets stick or bounce depends only on their size and fluid properties, but not on the incoming velocity. Here, we show using theory and experiments that even poorly wetting surfaces have a velocity-dependent criterion for bouncing of aqueous droplets, which is as high as 6 m/s for diameters of 30 to 50 μm on hydrophobic surfaces such as Teflon. We quantify this criterion by analyzing the interplay of dissipation, surface adhesion, and incoming kinetic energy, and describe a wealth of associated phenomena, including air bubbles and satellite droplets. Our results on inertial microdroplets elucidate fundamental processes crucial to aerosol science and technology.

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Bouncing microdroplets on hydrophobic surfaces

Abstract

Data Availability Statement

Acknowledgements

Funding

Keywords

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