What is it about?

The precise control of the boiling state of liquid drops on hot surfaces is crucial for a variety of heat and mass transfer fields. On high-temperature solid surfaces, the behavior of water drops typically exhibits two different scenarios: one in which the drop instantly undergoes explosive evaporation upon contact with the heated surface, and the other in which the drop maintains a floating stable state. In the latter case, the drop remains suspended on a vapor-insulating layer rapidly generated by the interface between the surface and the drop, a phenomenon known as the Leidenfrost state. In this paper, through the design of base materials and interface regulation, we discuss a previously unrecognized steady Leidenfrost state. In this state, the water drops stably 'stand' on hot and smooth hydrophobic surfaces, exhibiting distinct characteristics. The drops partially adhere to the hot surface, achieving their own balance through this partial adhesion. This phenomenon simultaneously triggers the drop's unique deformation and rotational behavior, reminiscent of the elegant dance of a Sufi whirling dervish. Our analysis of this standing Leidenfrost state reveals the underlying mechanisms that drive the drop’s stable partial adhesion and subsequent deformation with rotation.

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Why is it important?

It is commonly believed that the Leidenfrost drop keeps stable by floating over a self-vaporized cushion, which deteriorates the heat transfer. Our research explored a new stable Leidenfrost state with partial adhesion that the water drops ‘stand up’ and further ‘whirl’ on a hot smooth surface. The ‘standing’ Leidenfrost state exhibited markedly more efficient heat transfer than the conventional “floating” state. This discovery not only provides a new perspective for our understanding of drop behavior under extreme conditions but also has the potential to trigger significant application explorations in the field of thermal management and beyond.

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This page is a summary of: A standing Leidenfrost drop with Sufi whirling, Proceedings of the National Academy of Sciences, August 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2305567120.
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