This is basic research – not ready to use quite yet, but a neat idea anyway and it could well turn out useful.
The new material, developed by MIT mechanical engineer Hadi Ghasemi, consists of a thin double-layered disc. The bottom layer consists of spongy carbon foam that doubles up as a flotation device and a thermal insulator that prevents solar energy from dissipating into the fluid underneath. The top layer — the active layer — consists of flakes of graphite that were exfoliated using a microwave. The microwave causes the graphite to bubble up “just like popcorn” according to Gang Chen, another researcher involved with the work. [doi:10.1038/ncomms5449 – “Solar steam generation by heat localization”]