Electrohydrodynamic instabilities for smart window applications

Electrohydrodynamic instability in liquid crystals is investigated for smart window applications. By comparing different species of ions doped in liquid crystals, the positive charge of the organic part of the salt is the origin of the generation of vortexes and leads to the activation of electrohydrodynamic instability. By replacing conventional electrolytes with zwitterions, compared to electrolyte-doped liquid crystals, zwitterion-doped liquid crystals have a broader range of optimal frequency from 10 Hz to 5 kHz. The devices can be switched between the transparent state and the light scattering state for thousands of times without showing any fatigue. A scattering colour is obtained by incorporating a dichroic dye in zwitterion-doped liquid crystal. A patterned device is designed and shows a localised light scattering and colour effect in the presence of an electric field. This strategy will make electrohydrodynamic instability possible to enrich the applications across smart windows, projection screens and information displays.