Figure 1:
Schematic of the extension of polymer chains (in black) under the stress induced by a cutting wire. If the wire is simply pushed onto the solid, the chains under the wire will experience the largest tension. If the wire is simultaneously slid along its axis (in a slicing motion), stress becomes more symmetrically distributed within a small region around the perimeter of the wire. The chains thus stretch both normally as well as longitudinally (the combined deformation is shown in red). Due to the exponential relationship between stretch and fracture probability, rupture of the polymer chain will occur at a much smaller normal force.