A method of manufacturing a vapor-sensing device, including placing an aqueous dispersion of colloidal spheres on a substrate, drying the aqueous dispersion of colloidal spheres to obtain a colloidal crystal, filling the voids among the colloidal crystal with a vapor-expandable matrix composition, curing the vapor-expandable matrix composition, and peeling away any excess vapor-expandable matrix material from the surface of the film, so that the colloidal crystal is exposed.