Electrically tunable soft photonic gel formed by blue phase liquid crystal for switchable colour reflecting mirror

We report a robust soft photonic crystal system, fabricated using blue phase (BP) liquid crystal, which can efficiently filter visible light. The BP gel system is obtained without surface treatment or polymerization and thus is facile and cost effective to fabricate. Perfect monodomain with vivid colour is achieved with a low electric field, which can be further tuned to reflect a second colour. Most importantly, apart from the field induced colour switching, a dark / transparent state is also achieved due to complete unwinding of the BP helical structure. A potential application as a tunable colour reflecting mirror which can be switched between ‘reflecting’ and ‘transparent’ states is proposed.