Affymetrix received US Patent No. 6,646,243, “Nucleic acid reading and analysis system.” The patent covers a system for the preparation of a substrate containing a number of sequences. First, photoremovable groups are attached to a surface of a substrate. Then, selected regions of the substrate are exposed to light so as to activate the selected areas. A monomer, also containing a photoremovable group, is provided to the substrate to bind at the selected areas.