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Droplets reach lift-off

28 March, 2023

A drop of water is completely removed from a surface when a deformable sphere falls on it.

 

 

 

Learn how KAUST scientists are studying fluid dynamics using novel imaging and experimental methods. Copyright © 2022, Rafsan Rabbi et al. Reproduced under CC BY 4.0. https://discovery.kaust.edu.sa/en/article/1326/droplets-reach-lift-off

 

 

 

Water droplets are familiar phenomena, yet these droplets still hold surprises for scientists in how they behave.


A tennis ball dropped from a height will deform from its spherical shape when it hits the floor before bouncing back and returning to its spherical shape. Does this idea also apply to a falling droplet of water? The water would be expected to spread out as it strikes the surface. But this spread is slowed by viscosity —  water’s intrinsic resistance to flow. And if the surface is hydrophobic (it repels water), then the liquid can even begin to retract and, during this retraction phase, completely bounce back.

Tadd Truscott and co-workers investigated the fascinating situation in which the drop starts off sitting on the hydrophobic surface, and then a soft deformable sphere is dropped on it. “We discovered that a droplet can be lifted from the surface by an impacting ball if the elasticity and surface features of the ball and surface are matched,” explains Truscott. “This is a new way to clean or clear water from the surface.”

Read the full story at KAUST Discovery.