In one or more embodiments described herein, there is provided an apparatus comprising a substrate, and a plurality of carbon nanotubes (semiconducting nano-elements) disposed and fixed with said substrate. The nanotubes are disposed and fixed on said substrate such that they define a carbon nanotube network substantially at the percolation threshold of the network. As the network is at the percolation threshold, this provides for one or more signal paths extending from an input region to an output region. The apparatus is 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.