Mixing of vaporizing droplets on liquid substrates caused by festoon instability

A new configuration for a microfluid mixer, in which a mixed volume in the form of a volatile liquid droplet rests on a layer of water, is proposed. The mixing occurs owing to the injection of festoons emerging in a droplet under the influence of evaporation themocapillary convection from the periphery of the droplet to its central part. A linear relationship between the injection rate and the injection layer temperature is established, and it is shown that a droplet has time to repeatedly mix during its lifetime.