Long DNA Separation Using a Sparse Micropost Array

Long DNA are difficult to separate using traditional gel electrophoresis. We will present separation data obtained in a microfluidic device containing a sparse post array. The posts were made in hexagonal array of 1 µm diameter in 3 µm spacing using photolithography and deep trench etching. DNAs of λ XHo1 digest, Hind III digest, λ DNA-Mono cut mix, 2λ and T4 were mixed with λ DNA and tested in the device. The separations were measured with electropherograms recorded by a photomultiplier tube and a computer controlled fluorescent microscope. Under an electric field of 10 V/cm, the mobilities of different species were normalized by the λ DNA mobility in the mixtures and compared across the size range from 10 kbp to 165.5 kbp. DNA mobility depends linearly on molecular weight in this regime, allowing us to calibrate the device. We demonstrate the robustness of the device by using the calibration function to identify the peaks in a separation of the λ DNA-Mono cut mix.