Guiding Ambient Vapor to Condense at the Fixed Pattern on Micronano Hierarchically Aluminum Substrate for Antifrost Application

Vapor spontaneously diffuses from areas of high concentration to areas of low concentration as a consequence of the Second Law of Thermodynamics and the hunt for maximum entropy. The distribution of substances with lower saturated vapor pressures on a surface can create this concentration slope in the space. However, most substances, except ice, cannot maintain this slope because humidity sinking causes their saturated vapor pressure to drop. Moreover, the location of ice growth is difficult to control. In this paper, a pattern of CaCl2 was made on the micronano hierarchically aluminum substrate. When the temperature drops below zero, the vapor pressure at the position where CaCl2 is located is low relative to that of water as a way to achieve a continuous phase transition from solid CaCl2 to brine to ice. Thus, vapor nearby continuously diffuses to and deposits at the site, resulting in a lasting dry region around without water condensation. The frost growing on the pattern is also fluffy and can be easily removed by gravity and/or wind. This work has promising applications in areas where it is extremely difficult to use active deicing methods.