The refrigerant is also the pump

An electrocaloric polymer cooler efficiently pumps heat from cold to hot reservoirs Both applying an electric field to and removing it from a dielectric cause temperature changes (ΔT) and entropy changes (ΔS) of the dielectric, which is known as the electrocaloric (EC) effect (1) and is analogous to the changes that occur in a gas when it is compressed (T increases) and expanded (T decreases). In general, the electric field–induced T change in dielectrics is very small, but advances in the last decade have led to the development of several EC polymers and their nanocomposites that together generate more than 10°C EC cooling near room temperature as self-supporting films (2–4). Because EC polymers are insulators, there is very little energy loss during EC cooling. However, high-efficiency cooling requires efficient heat transfer from cold to hot ends of the cooling device. On page 1130 of this issue, Ma et al. (5) report an EC polymer cooler that elegantly integrates the high EC response in EC polymer films with electrostatic actuation (enabled by the flexibility of the polymer-film refrigerant) to efficiently transfer heat from the cold to the hot end.