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Abstract:
By sufficiently heating a solid, a sessile drop can be prevented from contacting the surface by floating on
its own vapour. While certain aspects of the dynamics of this so-called Leidenfrost effect are understood,
it is still unclear why a minimum temperature (the Leidenfrost temperature TL) is required before the effect
manifests itself, what properties affect this temperature, and what physical principles govern it. Here we
investigate the dependence of the Leidenfrost temperature on the ambient conditions: first, by increasing
(decreasing) the ambient pressure, we find an increase (decrease) in TL. We propose a rescaling of the
temperature which allows us to collapse the curves for various organic liquids and water onto a single
master curve, which yields a powerful tool to predict TL. Secondly, increasing the ambient temperature
stabilizes meta-stable, levitating drops at increasingly lower temperatures below TL. This observation
reveals the importance of thermal Marangoni flow in describing the Leidenfrost effect accurately. Our
results shed new light on the mechanisms playing a role in the Leidenfrost effect and may help to
eventually predict the Leidenfrost temperature and achieve complete understanding of the phenomenon,
however, many questions still remain open.
