Many areas such as synthetic biology, 1 nucleic acid vaccine, CRISPR Cas9 gene editing, protein engineering, molecular biology, and others require de novo synthesis of single-or doublestranded (ss-or ds-) DNAs longer than 200 nucleotides (nt). Because the state of the art chemical synthesis methods cannot reliably produce oligos longer than 200 nt, these ss-and ds-DNAs have to be produced via biological means such as polymerase chain reaction assembly (PCR assembly) or less commonly ligation using synthetic oligos shorter than 200-mers. While the biological methods have provided the required DNAs for the above mentioned areas to emerge and advance, many sequences desperately needed by some projects are beyond the reach of existing methods. For example, if a sequence contains higher order structures with unusual stability, the PCR assembly method may not function effectively. If a sequence contains repeating segments that are longer than the short oligos available from chemical synthesis, the biological means would not be able to accurately assemble the target DNA. If a sequence contains one or more site-specific modifications such as m A, the PCR assembly method may not be able to produce the sequence. To overcome these and other challenges, which were discussed in a previous article, there is an need to develop new methods for direct de novo synthesis of oligos longer than 200-mers.