Keywords: Brownian dynamics, microfabrication, boundary element method, DNA electrophoresis, separations Abstract: I will present our recent results on the dynamics of long DNA as they move through a hexagonal arrays of microfabricated posts under the influence of an electric field. The first part of the talk focuses on the potential of using sparse, ordered post arrays to separate long DNA by molecular weight. In particular, I will focus on the crucial role of electric field gradients on the separation process and how we can use microfabrication tools to control these gradients. In the second part of the talk, I will demonstrate how we are using a combination of Brownian dynamics simulations and videomicroscopy to gain a detailed understanding of the separation process at the macromolecular level.