Our overall objective is to design an integrated microfluidic system that will synthesize long genes of arbitrary sequence in high purity and cut the lead times and cost per base from the current values by at least one order of magnitude. This project consists of three parts: oligonucleotide synthesis, large DNA synthesis, and integrated system. My focus in this project is the large DNA synthesis. After the oligonucleotide synthesis, oligonucleotides are purified by MutS proteins and large DNA segments are manufactured by ligation chain reaction (LCR). They are amplified on a microfluidic chip by polymerase chain reaction (PCR). Gene synthesis in the microfluidic chip has very fast synthesis rate, high throughput process, and requires less experimental reagents and solvents due to the integration of all processes and its small reaction volume. This device can also shorten the rate of contamination and the overall time of the experiment by simplifying the material handling procedures to less than 48 hours. The scope of this research would be developing microfluidic chips that can synthesize many genes simultaneously.