Vapor chambers with jumping-drop liquid return from superhydrophobic condensers

In closed-loop phase-change systems, self-propelled jumping drops on a superhydrophobic condenser offer a new mechanism to return the working fluid to the evaporator, eliminating the requirement for either external forces or wick structures along the return path. Here, we report the heat transfer performance of a jumping-drop vapor chamber consisting of two parallel plates, a superhydrophobic condenser and a superhydrophilic evaporator. With proper removal of the non-condensable gases including those dissolved in the working fluid, the overall thermal resistance of the jumping-drop chamber is primarily governed by the conduction resistance of the wicked evaporator in series with the interfacial resistances at the phase-change interfaces. The lumped resistance model was verified by systematically varying the parameters of the chamber such as wick thickness, vapor spacing, vapor temperature, and heat flux. As an alternative mechanism to transport the working fluid, the jumping drops can enable novel phase-change heat transfer systems such as planar thermal diodes and heat spreaders, for which this work provides practical design guidelines.