Figure 21.

Schematic illustration of biased reptation. The chain is confined by the fibers of the gel to a reptation tube (dashed, red line). The arrows indicate possible directions for the chain to move along the tube. In the biased reptation model, the probability of moving in one of these two directions is biased by the electric field. A key assumption in the reptation theory is that the chain is confined inside the tube and cannot form hernias.¹⁸⁸