Maximum velocity for a single water molecule entering a carbon nanotube.

Carbon nanotubes, despite their hydrophobic nature, rapidly fill with water and allow super fast fluid flow through their interior due to the almost frictionless nanotube surface. The question arises as to whether it is possible to maximize the uptake (suction energy) of water and thus generate the highest possible fluid flow. In this paper, we outline the concepts of an acceptance condition and the suction energy and subsequently examine the suction characteristics of a single water molecule entering a carbon nanotube. In particular, we find that for the hydrogen atoms oriented towards the tube end, the radius of the carbon nanotube must be at least 3.464 A (or 0.3464 nm) for acceptance of a water molecule, and that a radius of 3.95 A provides the maximum uptake or suction energy.