Electrophoresis of a bead-rod chain through a narrow slit: A Brownian dynamics study

We use two-dimensional Brownian dynamics simulations to study the electrophoresis of a bead-rod chain through a narrow slit. A constant electric field is assumed to act inside and outside of the slit, and each bead on the chain is assigned a constant uniform charge. We calculate the dependence of the polymer transit velocity on chain length, slit dimensions (width-to-length ratio), and electric-field strength. For sufficiently narrow slits, the transit velocity increases nonlinearly with the applied field for low-field strengths, whereas it increases linearly for high-field strengths. In the low-field strength region and for sufficiently narrow slits, the transit velocity decreases rapidly for small chain lengths and then decreases slowly beyond a critical chain length. As the slit width increases, the transit velocity decreases with chain length in more continuous manner, and for sufficiently large slits the transit velocity becomes independent of chain length as expected. Distributions of the chain end-...