Electronic friction and liquid-flow-induced voltage in nanotubes

A recent exciting experiment by Ghosh [Science 299, 1042 (2003) ] reported that the flow of an ion-containing liquid such as water through bundles of single-walled carbon nanotubes induces a voltage in the nanotubes that grows logarithmically with the flow velocity v(0). We propose an explanation for this observation. Assuming that the liquid molecules nearest the nanotube form a two-dimensional solidlike monolayer pinned through the adsorbed ions to the nanotubes, the monolayer sliding will occur by elastic loading followed by the local yield (stick-slip motion). The drifting adsorbed ions produce a voltage in the nanotube through electronic friction against free electrons inside the nanotube. Thermally excited jumps over force-biased barriers, well known in the stick-slip model, can explain the logarithmic voltage growth with flow velocity. We estimate the short-circuit current and the internal resistance of the nanotube voltage generator.