“…In particular, truncated conical capillaries have been extensively studied as the simplest model to study the effect of geometrical gradient and, in particular, as the model of imbibition into porous substrates 5 . Also, they have been studied for their potential applications as micro-and nano-fluidic devices 12,16,[18][19][20][21][22][23] such as liquid diode 12,16,20,21 , ionic current rectifier 18 , pump 19 , Janus paper 22 , and water harvesting 23 . Carbon nanocone seems the most promising candidate of conical nano capillaries 23,24 .…”