Optical microscope study of liquid transport in carbon nanotubes

Taking advantage of the transparency to visible light of CNTs with 15 nm thick walls, we studied experimentally capillary filling, condensation, and evaporation of glycerin, ethylene glycol, and distilled water inside CNTs at room conditions. All liquids readily filled the CNTs by the action of capillary forces. The experimental observations of capillary filling and rates of evaporation and condensation were compared and agreed favorably with simple theoretical predictions. This is the first report on optical studies of liquid transport inside carbon nanotubes (CNTs).