Abstract: An assay technique for qualitative and quantitative detection of a chemical, biochemical or biological detection of a chemical, biochemical or biological species in sample. The technique comprises: (a) coating at least a predetermined part of a pre-formed surface on a substrate with a thin film of a material capable of binding the species to be assayed, the pre-formed surface being optically active with respect to radiation at least over a predetermined band of wavelengths; (b) contacting the coated surface with sample; and (c) observing the optical properties of said pre-formed surface in order to determine a qualitative and quantitative change in optical properties as a result of the binding of the species onto said thin film of material. The optical properties as a result of the pre-formed surface may be observed before and after step (b) in order to determine any change in optical properties, or they may be monitored during step (b). The pre-formed surface is preferably a grating.

Abstract: An assay technique for qualitative and quantitative detection of a chemcial, biochemical or biological detection of a chemical, biochemical or biological species in sample. The technique comprises (a) coating at least a predetermined part of a pre-formed surface on a substrate with a thin film of a material capable of binding the species to be assayed, the pre-formed surface being optically active with respect to radiation at least over a predetermined band of wavelengths; (b) contacting the coated surface with sample; and (c) observing the optical properties of said pre-formed surface in order to determine a qualitative and quantitative change in optical properties as a result of the binding of the species onto said thin film of material. The optical properties of the pre-formed surface may be observed before and after step (b) in order to determine any change in optical properties, or they may be monitored during step (b). The pre-formed surface is preferably a grating.