First solid-state freezer

The first solid-state freezer is an elastocaloric freezing device developed by a team of researchers, led by Guoan Zhou, from The Hong Kong University of Science and Technology (China). In a paper published in Nature on 14 January 2026, the team explained how a heat-sink machined from a nickel-titanium alloy made it possible to freeze 20-ml of water without the need for conventional heat pumps or refrigerants.

The freezer was designed around the unique phase-transition properties of what are called shape-memory alloys (or SMAs). These are metals that heat up when compressed, and cool down when relaxed.

The team machined a mesh of fine Ni-Ti tubes which were placed inside the cooler box (roughly the size of a shoebox). The mesh was then cycled between compression and relaxation about once a second, with the heat generated by the compression being transferred to an external heat-exchanger by a constant flow of liquid inside the tubes.