The overall conductivity of SWNT networks is dominated by the existence of high resistance and tunneling/Schottky barriers at the intertube junctions in the network. Here we report that in-situ polymerization of a highly conductive self-doped conducting polymer �skin� around and along single stranded DNA functionalized- SWNTs can greatly decrease the contact resistance. The polymer skin also acts as �conductive glue� effectively assembling the SWNTs into a conductive network, which decreases the amount of SWNTs needed to reach the high conductive regime of the network. The conductance of the composite network after the percolation threshold can be two orders of magnitude higher than the network formed from SWNTs alone. In addition, the polymer skin also provides a powerful functionality for biosensor applications.

However, we found that only in-situ polymerized conducting polymers were able to effectively interlink the SWNTs to form a highly conductive network. The pre-formed conducting polymer dramatically decreased the conductivity and increased the percolation threshold of the SWNT networks. Surprisingly, the conducting polymer formed by in-situ polymerization with pre-oxidized SWNTs (�seed� method) did not assemble the nanotubes into a conductive network either. Instead, the polymer induced severe aggregation of the nanotubes into large particles. Consequently, the percolation threshold of the composite formed by the seed approach is much higher and the conductance after the percolation threshold is three orders of magnitude lower than the network formed by SWNTs alone. Various techniques were applied to understand the mechanism for the different enhancement in nano and molecular scales.