Ferroelectric nematic liquid crystals: temperature-tunable electrocaloric fluids with large strength at low fields

The electrocaloric (EC) effect offers a promising energy-efficient and clean cooling technology. We present the first direct measurements of EC temperature change in a new family of EC fluids, ferroelectric nematic liquid crystals (FNLCs), demonstrating in two such materials temperature jumps of |ΔT _j | ~ 0.2 K for field changes as low as ΔE ~ 0.1 V μm^-1. Indirect measurements of adiabatic temperature change $|\Delta \mathrm{T|}$ confirm that these direct measurements are an underestimate and that ΔE = 2 V μm^-1 can induce up to |ΔT _j | ~ 1.6 K, yielding EC strengths |ΔT/ΔE| up to 100% higher than incumbent materials. For temperature spans of 5-10 K, we predict a coefficient of performance of ~21-40. We find |ΔT|~1 K for >100 FNLCs that collectively span all temperatures between 0 ˚C and 100 ˚C. This, together with the new device concepts conceivable with fluid EC materials, offers huge potential for cooling applications.