Figure 30.

Schematic diagrams depicting the different states experienced by the droplets. Ω is the total volume of the droplet. (i) The droplet grows inside the microcone cavity until ΔP_in becomes slightly positive and starts to move outside the cavity. (ii) The upper meniscus contact line of the droplet reaches the top of the microcavity and the lower meniscus contact line moves upward. (iii) The droplet grows further to the critical upper meniscus radius of curvature R_t,cr = L/2 above which coalescence with the neighboring droplets occurs. (iv) Coalescence of a droplet Ωcr with a larger droplet of at least ~4 Ω_cr. The average pressure P_in(Ω_cr) within a small droplet is much larger than P_in(~4 Ω_cr) within a larger droplet. (v) This coalescence induces a pressure difference that drags the small droplets out of the microcone cavity. Reprinted with permission from Ref [133]. Copyright 2018 American Chemical Society.