An experimental study on the non-coalescence exhibited by anchored aqueous droplets in air

In this work an effort has been made to demonstrate and understand electrocoalescence phenomena in dropletin-air system using an anchored drop setup. Phase diagrams pertaining to the behaviour of droplet-in-air system is absent in the existing literature, and hence, are constructed for three different droplet conductivities, low (1.5 mu S/cm), moderate (1244 mu S/cm), and high (89500 mu S/cm). The critical electrocapillary number Ca-c (estimated to be (similar to)0.25) for anchored droplets is found to be independent of droplet conductivity, cone angle, and separation distance between the droplets. For separation less than s(0)/R = 0.5, coalescence is observed at all Ca > Ca-c because the cone angle of contact is always less than the critical angle of contact for non-coalescence. Different mechanisms govern non-coalescence behaviour with change in droplet conductivity. In addition to coalescence and non-coalescence events, subsequent events after first non-coalescence are studied and an effort is made to explain and categorize the behaviour under different regimes.