Heat is applied to a water-attracting plate opposite a hydrophobic plate.

An engineer at Virginia Tech has developed an aircraft thermal management technology that stands ready for adaptation into other areas. The planar bridging-droplet thermal diodes present a novel approach to thermal management.

This new bridging-droplet thermal diode can be used upright, sideways, or even upside-down, and would even work in space where gravity is negligible.

Source