Surface evolution of manganese chloride aqueous droplets resulting in self-suppressed evaporation

The exchange kinetics of liquid water, which are of fundamental interest and have potential applications, remain unclear. A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride. As observed from the evolution of this type of droplet, a thin film was formed on the surface with an exothermic phase transition, resulting in self-suppressed evaporation. The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C. In contrast, a pure water droplet can only be sustained for a few minutes. The self-suppressed evaporation of doped water may be due to the special hydration of the accumulated manganese and chloride ions at the surface, decreasing the surface tension.