Abstract: The invention overcomes the limitations described for the bonding of structured layers by providing a method for selectively reducing the bonding of materials. In its most generic form, the invention uses a bonding technique in combination with a printing method for modifying or covering at least one portion of a surface to either fully or partially prevent localised bonding. The structuring process may act upon the layers either before or after the bonding of the layers. The invention overcomes the limitations described in the application of affinity chromatography by providing a planar substrate with discrete optical detection flow cells that contain porous material and have connecting microchannels for fluid delivery and/or removal, and a method for making the same.