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arXiv · 1703.01419

Mechanism of Contact between a Droplet and an Atomically Smooth Substrate

Hau Yung Lo·Yuan Liu·Lei Xu
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Abstract

When a droplet gently lands on an atomically smooth substrate, it will most likely contact the underlying surface in about 0.1 s. However, theoretical estimation from fluid mechanics predicts a contact time of 10 to 100 s. What causes this large discrepancy, and how does nature speed up contact by 2 orders of magnitude? To probe this fundamental question, we prepare atomically smooth substrates by either coating a liquid film on glass or using a freshly cleaved mica surface, and visualize the droplet contact dynamics with 30 nm resolution. Interestingly, we discover two distinct speed-up approaches: (1) droplet skidding due to even minute perturbations breaks rotational symmetry and produces early contact at the thinnest gap location, and (2) for the unperturbed situation with rotational symmetry, a previously unnoticed boundary flow around only 0.1 mm/s expedites air drainage by over 1 order of magnitude. Together, these two mechanisms universally explain general contact phenomena on smooth substrates. The fundamental discoveries shed new light on contact and drainage research.

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Hau Yung Lo, Yuan Liu, Lei Xu. 2017-03-04. Mechanism of Contact between a Droplet and an Atomically Smooth Substrate. https://doi.org/10.1103/physrevx.7.021036

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