Elastocaloric heat pump with specific cooling power of 20.9 W g–1 exploiting snap-through instability and strain-induced crystallization

Conventional refrigeration relies on hazardous agents, contributing to global warming. Soft, cheap, biodegradable solid-state elastocaloric cooling based on natural rubber offers an environmentally friendly alternative. However, no such practical cooler has been developed, as conventional soft elastocaloric designs are not fast enough to ensure adiabaticity. Here, we combine snap-through instability with strain-induced crystallization and achieve a sub-100 ms quasi-adiabatic cycling, which is 30 times faster than previous designs. Negligible heat exchange in expansion/contraction stages combined with the latent heat of phase transitions results in a giant elastocaloric crystallization effect. The rubber-based all-soft heat pump enables a specific cooling power of 20.9 W g–1, a heat flux of 256 mW cm–2, a coefficient of performance of 4.7 and a single-stage temperature span between hot and cold reservoirs of 7.9 K (full adiabatic temperature change of rubber membrane exceeding 23 K). The pump permits a compact all-soft voltage-actuated set-up, opening up the opportunity of a viable plug-in-ready cooling device. Solid-state caloric cooling is a promising alternative to vapour compression, yet only a few prototypes have been shown. Greibich et al. now report an elastocaloric cooling device based on natural rubber with a cooling power of over 20 W g–1 that exploits snap-through instability and strain-induced crystallization.