Heat pipes are reliable, passive devices to transport heat. However, their heat transport capacity degrades rapidly as they get longer due to insufficient capillary pressure generated by the heat pipe wick.
Our recent efforts have targeted developing new planar heat pipe technology that can transport kilowatts of heat over meter-long distances. The enabling technology is the replacement of the heat pipe wick with electrowetting-based pumping. The electrowetting heat pipe (EHP) uses electrowetting to pump condensate to the evaporator in the form of discrete droplets. This innovation overcomes the capillary limit to heat transport and enables planar, long heat pipes for moving high heat loads. The microfluidics of this device was tested on the International Space Station in 2017.