Humidity sensing with printable films of lyotropic chromonic liquid crystals

Lyotropic chromonic liquid crystals (LCLCs) combine a very high packing density (intramolecular separation is about 3.4 A within aggregates) with an ability to form ordered structures that are transferable from a water solution to a dry film. We show that the electric current in a dry film of LCLC aggregates is sensitive to the distance between the molecules in the aggregates and that it depends on the ambient humidity. Thus, by measuring the electric current through an LCLC film printed onto a substrate with predesigned electrodes and integrated circuits, we can measure the humidity. A humidity sensor based on LCLCs has high sensitivity, a fast response, and short recovery times.