Levitation of Sparkling Water Drops using Self-Generated Gas Cushion

Previous studies have shown that droplet levitation on solid surfaces (Leidenfrost effect) can be realized by creating a vapor/air cushion under the drop using evaporation, gas perfusion or surface-driven motions. However, the major limitation of these methods is that the substrate needs to be either heat resistant, porous or mobile. A progressive loss of liquid volume is an additional drawback in the case of evaporating droplets. We demonstrate a room-temperature Leidenfrost effect that is driven spontaneously by the degassing of carbonated water droplets deposited on superhydrophobic surfaces. We observe the levitation-to-wetting transition of these degassing droplets using light interferometry on transparent superhydrophobic substrates. We characterize the timescales of the wetting transitions with respect to the concentration of dissolved carbon dioxide and show that a minimum critical dissolved carbon dioxide concentration of ≈10 mM is required for achieving droplet levitation. We finally display the practical utility of this phenomena for liquid-solid friction reduction, droplet sorting, self-propulsion, and on-demand droplet levitation using chemical reactions.