Capillary bridge retention between two particles

A droplet on a flat surface, which has a convex air-liquid interface, evaporates linearly according to the time. A concave air-liquid interface in a microscopic length scale has been revealed to have different evaporation dynamics due to the negative curvature. According to the Laplace-Young equation, the low pressure inside the air-liquid interface is expected to suppress the evaporation rate, so there could be a retention effect. Significantly, the two-particle system is the representative case for that phenomenon. Here, we show a capillary bridge retention dynamics as a thermodynamic equilibrium state between two particles. We observe the capillary bridge using an optical microscope and X-ray microscope to visualize the interface line. We experimented with several micro-radius-scale systems from 10⁰ um to 10² um to find if the evaporation dynamics and thermodynamic equilibrium depend on the internal pressure induced by the air-liquid interface's negative curvature. This comprehension of capillary bridge retention would be essential in the fundamental fields such as cloud seeds, sand, soil, and industrial fields such as inkjet printing, painting, and cosmetics.