A method for performing a diagnostic assay of an analyte, wherein the method comprises providing a base that has been structured using laser processing so as to provide a substrate with at least one patterned surface, wherein the laser processing comprises the selective application of pulsed laser energy to the base, whereby to melt a surface layer of the base which resolidifies, whereby to create the at least one patterned surface; applying a metal to the at least one patterned surface so as to provide at least one metalized patterned surface; positioning the analyte on the at least one metalized patterned surface; and performing a diagnostic assay of the analyte.