Plastic substrates, including poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) slides, may be modified with methods described herein and subsequently used in the manufacture or formation of biochips, or other microarrays. Illustrative methods include modifying the surface of the plastic substrates by covalent attachment of unsaturated acid derivatives that include a primary amine group for reacting with functional groups on the surface of the plastic substrate. Further illustrative methods include modifying the surface of the plastic substrates by a cleaning procedure that results in improved adhesive properties for subsequent printing. After being modified, the substrates described herein may be used to prepare 2D and 3D microarrays by printing using conventional methods.