A sensor system including devices and methods for determining the concentration of an analyte in a sample is described. The assembly may also have a lens carrying the film. The wrap includes a plurality of flaps extends from opposite sides of a generally longitudinal central portion, such that one or more flaps from the opposite sides fasten to each other to surround the body portion. A metal layer is deposited on the dielectric layer to fill the recessed areas and cover the non-recessed areas.