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 | Δ T j | ~ 0.2 K for field changes as low as Δ E ~ 0.1 V μm -1 . Indirect measurements of adiabatic temperature change |Δ T| | Δ T| confirm that these direct measurements are an underestimate and that Δ E = 2 V μm -1 can induce up to | Δ T j | ~ 1.6 K, yielding EC strengths | Δ T/ Δ E| 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 |Δ T|~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.