Nanoparticle-stabilised blue phase liquid crystals enabling ultra-low-voltage electro-optic switching at room temperature

We report a blue-phase liquid crystal (BPLC) formulation that achieves room-temperature operation with ultra-low drive voltage via doping. Four cells were studied: undoped (S1), MWCNT-doped (S2), Ag-NP-doped (S3) and Au-NP-doped (S4). The field threshold drops from 25 V (S1) to 10 V (S2), 2.5 V (S3) and 0.10 V (100 mV) in S4, where a complete dark state is reached at 100 mV under crossed polarisers. The blue-phase temperature span for the doped systems is ~22.3°C (S2), ~21.6°C (S3) and ~23°C (S4), each encompassing room temperature, whereas the undoped sample exhibits a different thermal profile and requires much higher voltages for switching. Phase assignment and stability windows were confirmed by polarised optical microscopy, temperature-dependent dielectric spectroscopy and reflectance spectra. These results are supported by a temperature-dependent Landau–de Gennes modelling framework, which links blue-phase stability with electro-optic threshold behaviour. The analysis identifies a crossover from lattice-dominated electrostriction to defect-mediated, plasmon-assisted switching at high disorder. These results demonstrate a practical route to low-power, room-temperature BPLC devices for displays and tunable photonics.