Quantized conductance
(Top) A transmission electron microscope image of the macroscopic fibre of multiwall nanotubes used by Walt de Heer and co-workers at the Georgia Institute of Technology to measure the conductance of individual multiwall nanotubes. As the fibre is lowered into liquid mercury, contact will initially be made with just one of the nanotubes that sticks out from the bundle (insert). (Bottom) A plot of conductance versus depth clearly shows that the conductance increases in units of the quantum of conductance as the number of individual nanotubes making contact with the mercury increases. This suggests that nanotubes are ideal waveguides for electrons (see Frank et al. in further reading).