A self-actuated electrocaloric polymer heat pump design exploiting the synergy of electrocaloric effect and electrostriction

Caloric cooling is an attractive family of technologies owing to their environmental friendliness and potential for higher efficiency than present refrigeration systems. Cooling devices based on the electrocaloric (EC) effect specifically have the added benefit of being easily miniaturized, enabling applications in electronic thermal management, wearables and localized cooling. A challenge in prior compact EC cooling devices has been the need for a separate actuation mechanism to cyclically contact the EC material with hot and cold interfaces. Here, we propose a self-actuated EC polymer heat pump, exploiting recent discoveries of giant EC and electromechanical responses under low electric fields in P(VDF-TrFE-CFE-FA) (VDF: vinylidene fluoride, TrFE: trifluoroethylene, CFE: chlorofluoroethylene, FA: fluorinated alkynes) relaxor tetrapolymers. We show that the transverse electroactuation of P(VDF-TrFE-CFE-FA) relaxor tetrapolymer films can be tailored over a broad range, from strong actuation to weak actuation, without affecting the high EC response. Using this principle, a unimorph actuator was constructed from two EC tetrapolymer layers with large differences in electroactuation. This device autonomously achieves a large displacement between the heating and cooling cycles of the EC films, which could be used to switch thermal contact between hot and cold interfaces. This concept could thus enable highly efficient and compact EC heat pumps.