Dripping of a liquid from a tube in the absence of gravity.

In zero gravity, liquid does not drip from a tube but hangs from it for all time as a pendant drop. It is shown that a drop can be made to fall off a tube by heating the contact line (CL), which causes a temperature gradient between the drop's CL and its tip. Simulations show that whether a drop detaches from or remains attached to the tube is set by the competition between the Marangoni stress that causes flow away from its CL, where the surface tension is low, toward its tip, where is high, and the capillary pressure that causes flow from the tip back toward the CL. The method can be used to make microscopic (nanoscopic) drops by dripping in ordinary gravity, which had heretofore been unattainable.