A liquid crystalline chirality balance for vapours

Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs). Chiral determination of vapours is possible in biological systems as an important part of the olfactory system. Here, the authors describe a system that is capable of visually detecting and distinguishing the chirality of vapour-phase molecules by structural changes in a liquid crystal confined in open microchannels.