Doubly re-entrant cavities to sustain boiling nucleation in FC-72

We report a micro- and nano-machined surface cavity on which boiling nucleation resumes after ceasing in perfluorohexane (i.e., FC-72, a Fluorinert™ from 3M™) for a short time. To the best of our knowledge, this is the first such success with FC-72, which has the lowest surface tension of all available liquids and completely wets any existing material including Teflon^® so that all surface cavities get flooded once nucleation stops. Despite the wide usage in electronics cooling, FC-72 was never considered for boiling heat transfer because once cooled boiling would not restart without an excessive heating. Our result experimentally supports the half-century-old idea of doubly re-entrant cavities envisioned to facilitate more stable nucleation, encouraging further development.