What is it about?

This work examines what happens when very tiny water based droplets hit surface - do they stick, or do they bounce away? We found that it isn’t just about how water-repellent the surface is, or the how viscous the fluid is. The droplet’s speed and size are also important. If the droplet is too slow it sticks. Too fast, it also sticks. Only at just the right speed can it bounce. We also discovered that droplets below a certain size can never bounce at all. These findings are significant for everyday things like how pesticides spread on plants, how inkjet printers work, and even how cough or sneeze droplets behave.

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Why is it important?

Droplets are everywhere in daily life, from raindrops and crop sprays to printing and the tiny droplets we breathe out. Whether they stick or bounce changes how diseases spread, how well pesticides work, and how reliably we can print or coat surfaces. By showing how we can control droplet behaviour, our work gives simple rules to help design better coatings, improve technologies, and even guide health advice.

Perspectives

This article aims to show that tiny, everyday processes, like droplets hitting a surface, are far from mundane. They are surprisingly complex, and scientists spend a great deal of time trying to understand them. Our study provides an essential foundation for advancing many different processes. When you think about droplets, consider the many places they matter: how medicines are delivered, how crops are sprayed, or how diseases spread. Our high-speed images reveal dynamics that normally happen too quickly and on too small a scale for us to notice, slowing them down so we can connect fundamental physics to real-world challenges.

Jamie Mclauchlan
University of Bath

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This page is a summary of: Bouncing microdroplets on hydrophobic surfaces, Proceedings of the National Academy of Sciences, September 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2507309122.
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