1. An apparatus comprising: a substrate; a plurality of carbon nanotubes disposed and fixed with said substrate to define a carbon nanotube network substantially at the percolation threshold of the network, wherein the percolation threshold provides for one or more paths extending from an input region to an output region of the network, the apparatus being configured to, upon receiving particular input signalling via the input region, provide particular predefined output signalling at the output via the one or more signal paths, the particular output signalling being predefined according to the one or more one signal paths.