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Accepted · first revision · record

Title: Predicting contact-angle hysteresis from measured surface defect statistics
Plain: Raindrops stick to a tilted window because the drop edge catches on tiny surface defects, so the angle needed to advance is larger than the angle at which it recedes. Can this gap be computed from a map of the defects alone?
Precise: For a liquid on a solid with chemical or topographic defects of density $n_d$, size $d$ and wettability contrast $f_d$, all measured independently, predict the hysteresis $\cos\theta_r-\cos\theta_a$, including the crossover between dilute defects that each pin the line independently and dense defects that pin it collectively. An answer is a formula or simulation protocol that predicts hysteresis within experimental error for surfaces with designed disorder, with no fitted parameters.
Settled by: Hysteresis measurements on lithographically patterned surfaces with controlled $n_{d}, d\ \text{and}\ f_{d}$, compared with blind predictions from the elastic-line model.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)