Abstract: A method is disclosed for the direct synthesis of double stranded DNA molecules of a variety of sizes and with any desired sequence. The DNA molecule to be synthesis is logically broken up into smaller overlapping DNA segments. A maskless microarray synthesizer is used to make a DNA microarray on a substrate in which each element or feature of the array is populated by DNA of a one of the overlapping DNA segments. The complement of each segment is also made in the microarray. The DNA segments are released from the substrate and held under conditions favoring hybridization of DNA, under which conditions the segments will hybridize to form duplexes. The duplexes are then separated using a DNA binding agent which binds to improperly formed DNA helixes to remove errors from the set of DNA molecules. The segments can then be hybridized to each other to assemble the larger target DNA sequence.