In this paper, we report a factor of 3 improvement in the resolution and a factor of 10 improvement in the speed of fractionation of approximately 100-kb DNA molecules in Brownian ratchet arrays. In our device, the electrophoretic flow is tilted at a small angle relative to the array axis. Tilting accelerates the fractionation speed because a higher fraction of the diffusing molecules is "ratcheted" at each step in the array. Molecules of lengths 48.5 and 164 kb can be separated in approximately 70 min with a resolution of approximately 3.8, using a 12-mm-long array. The Brownian ratchet arrays are not limited to DNA separation, but can, in principle, be used for any particle in this size range.