Nanofilters are a promising new class of nanofabricated devices that have proven very successful at rapidly separating sub-kilobasepair DNA and denatured proteins using weak electric fields, typically less than 100 V/cm. The device consists of a series of narrow slits (~50nm) connecting deep wells (~300nm) that trap the DNA. The rate of escape from the wells is a function of molecular weight, leading to a size-dependent elution process. Experiments and near-equilibrium theoretical arguments both indicate that smaller DNA emerge from the device first, and that separations fail at ~100V/cm. We show, on theoretical grounds, that the range of useful electric fields in nanofilters should extended beyond the experimentally observed limit of 100V/cm to high values of around 1000 V/cm, which would enhance the speed and the performance of this class of DNA separation devices. Based on scaling arguments, the separation of short, rod-like DNA molecules at these high fields occurs by a new mechanism that we call “torque-assisted escape”. Although DNA migrate from slit to slit in a strong field without much translational diffusion into the well, they can arrive at the slit entrance in a forbidden orientation due to rotational diffusion. Their escape is then enabled by the torque that originates from the non-uniform electric field at the slit entrance. The quadratic dependence of the torque on the molecule size indicates that larger molecules will now emerge first. As a result, we predict that separations in this high-field regime operate in band-inverted manner; larger molecules should now elute first. This claim is further examined via Brownian dynamics simulations. The simulation results confirm that the mobility increases with molecular weight, and also indicate a quasi-plateau in the mobility at very large fields. In an effort to optimize the nanofilter geometry for separating short DNA, we also study the effect of the well depth on the elution process. As the well deepens, short molecules will span smaller gradients in the electric field, which can delay their exit by torque-assisted escape. The size-dependent optimal well depth should then lead to a method for a better tuning of the separation