Figure 3: Two evaporation stages.
From: Low internal pressure in femtoliter water capillary bridges reduces evaporation rates
(a) The water film height, normalized by each particle diameter, is initially pinned and then quickly depinned by evaporation. This behavior can be analyzed by rescaling time according to the characteristic time α, taken at h/d = exp(−1). (b) The first pinning stage appears up to t/α ~ 0.96, corresponding to θ ~ 60o, equivalent to a ≈ ½ rp. The second depinning stage emerges for a very short time around t ~ α. (c) The water contact angle ϕ increases during the pinning stage and quickly decreases up to zero during the depinning stage, indicating that the water bridge becomes catenoidal. (d) The microspheres used here are monodispersed, rp = 3.0 ± 0.03 μm (a standard deviation from 24 datasets), as demonstrated by the SEM image.
