A sensor, such as a lateral flow sensor, which includes a chemical layer and a detector on a flexible substrate. An optical signal is produced in response to an analyte placed on the chemical layer. The detector detects the signal, to thereby detect the presence, absence or concentration of the analyte. The detector is on the substrate. The chemical layer and the substrate are laminated together, to thereby form an integrated sensor. The sensor can include a light source. The light source can be on the substrate, or on an opposite side of the chemical layer than the detector.