One aspect of the disclosure involves a nib material comprising a polymeric matrix and carbon nanotubes in the matrix. In one or more embodiments of any of the foregoing embodiments, the matrix comprises a silicone. In one or more embodiments of any of the foregoing embodiments, the rub material is at least 1.0 mm thick. In one or more embodiments of any of the foregoing embodiments, the silicone is selected from the group consisting of dimethyl- and fluoro-silicone rubbers and their copolymers. In one or more embodiments of any of the foregoing embodiments, the carbon nanotubes at least locally have a concentration of 1-20% by weight.