A method and apparatus for assay of multiple analytes. The method uses a sensing
element comprising a substrate upon which is arranged a multiplicity of recognition
elements, such that each element is laid out in a predetermined pattern. Each pattern
is unique in that it can give rise to a characteristic diffraction pattern in the
assay. The patterns may or may not be interpenetrating on the substrate surface.
The method of detecting multiple analytes includes contacting the medium of analytes
with the patterned substrate, illuminating the substrate by a light source, and
detecting any resultant diffraction image. The pattern of diffraction and the intensity
of the diffracted signal provides information about the existence of specific analytes
and their quantification.