Elastocaloric Cooling on the Miniature Scale: A Review on Materials and Device Engineering

This Review covers the fundamentals of operation and scaling of elastocaloric cooling devices as well as current developments of elastocaloric shape-memory alloy (SMA) films and the engineering of SMA film-based cooling devices. Sputter-deposited TiNiCuCo alloys showing ultra-low fatigue enable unique functional properties such as tailored transformation temperature gradients. Two substantially different concepts for the development of elastocaloric cooling demonstrators are discussed. One concept relies on heat transfer by mechanical contact between the elastocaloric SMA film and solid heat sink and source elements. The second concept makes use of the heat transfer between the elastocaloric SMA film and a heat transfer fluid, including the advanced technology of active regeneration. Demonstrators based on a single SMA film reach device temperature spans of 14K and a high specific cooling power of up to 18Wg(-1). The performance characteristics are compared with other solid-state caloric cooling technologies.