(250d) Research of DNA Separation By Post Array Under Intermittent Electric Field

We applied an intermittent electric field to replace the continuous one to separate λ-(48.5kbp) and T4(165.6kbp) DNA in a fused silica microchannel with a hexagonal post array of 1 micron diameter and 3 micron pitch. In the post array, the mobility of DNA decreases with molecular weight since larger DNA has higher probability to hit and hook on the post. However, the occurrence of channeling phenomenon restricts not only the operating condition but also the separation efficiency of a fixed length post array. By using intermittent electric field, the electric field(E) is repeatedly turned on for a time interval t_on and turned off for a time interval t_off. With an intermittent electric field, the channeling phenomenon was suppressed by the relaxation of DNA during the “off” period. We also correlated t_on with the trapping time of DNA. The results indicated that t_on set in between the trapping time of T4 and λ-DNA has the best resolution of separation for a fixed separation time while t_on set close to the trapping time of λ-DNA yields the best resolution of separation for a fixed channel length. Compared to continuous electric field, an intermittent one enables the separation to be conducted under higher Pe. With properly tuned t_on and E, the resolving power of a channel with fixed length increases only at the expense of time. For a given post array, intermittent electric field offers much more flexibility in choosing operation conditions for optimized separation.