Collective effects in microbubble growth by solvent exchange

Regulating the formation and growth of microscopic bubbles at solid-liquid interfaces is essential in many physical, chemical, and catalytic processes, such as the electrolysis of water or a dry-wet transition of a superhydrophobic surface. The growth of bubbles in a group is influenced by the neighboring bubbles as well as the overall gas concentration in the system. In this work, we have investigated the growth of multiple microbubbles on highly ordered hydrophobic microcavity arrays, seeded by pre-existing gas pockets trapped inside the cavities. A pulse of gas oversaturation at an extremely low level was supplied in a process we call solvent exchange. Our results show that the distance between the seeding air pockets has significant effects on the location, number density, and size of bubbles on the array. With closely spaced microcavities, growing microbubbles self-organized into symmetric patterns. Their growth rate was enhanced at the corners and edges of the array, and interior bubbles dissolved because of the competitive growth. By contrast, no symmetric patterns were observed when the space between the microcavities was large. The findings reported in this work provide important insights into solvent exchange and collective interactions in the formation of surface nanobubbles.