Dynamic Defrosting on Superhydrophobic and Biphilic Surfaces

Ice formation and accretion present serious concerns formany building energy applications. Current defrosting methods expend significant energy by reversing the system cycle direction to heat the working fluid. Additionally, water retained on heat exchangers post defrosting cycle decreases the long-term heat-transfer performance. Here, we study the defrosting behavior of superhydrophobic and biphilic surfaces having spatially distinct wettability domains. Through optical imaging, we show that defrosting on biphilic regions is dynamic, where the ice/frost layer undergoes spontaneous motion because of a highly mobile slush. The high mobility of dynamic defrosting enables surface forces to pull and remove the slush from the superhydrophobic regions prior to it completely melting. To explore the effect of pattern heterogeneity, we studied nature-inspired biphilic patterns such as banana leaf. Our work provides the fundamental understanding required for design of heterogeneous defrosting coatings and elucidates the role of wettability gradients on defrosting dynamics.