Micropatterned surfaces with both hydrophilic and hydrophobic regions are relevant for a wide range of applications from fuel cells to water harvesting systems. The preferential nucleation of water on hydrophilic regions can also be used to control frost nucleation on chemically patterned surfaces. So far, this concept has been tested on brittle silicon surfaces with only a few different sizes and shapes of hydrophilic regions. In this work, the concept of controlled icing is investigated on five polymeric surfaces with different surface energies modified by micropatterning them with three types of hydrophilic polymer brushes. Frost formation and propagation on the resulting patterned surfaces with regions of varying wettability is monitored and quantified using high-resolution thermal imaging. The study proves that control over frost nucleation and propagation using regions of varying wettability can be achieved on commodity polymers. In addition to influencing the time and location of ice nucleation, the local patterning affects the freezing propagation mode and rate due to its impact on the continuity and thickness of molecular water layers (MWL). These results show that local control over the state of MWLs is key to controlling both ice nucleation and propagation of freezing events on surfaces.

In this work, we study the relationship between the molecular water layer (MWL) and frost freezing onset and propagation. The progression of frost has been reported to be governed by various localized icing phenomena, including interdroplet ice bridging, dry zones, and frost halos. Reports studying the state of water on surfaces have revealed the presence of a thin nanometer water layer on a range of surfaces. Regardless of further investigations that show environmental humidity, temperature, and surface energy to affect the thickness of the MWL on surfaces, the influence of the MWL on frost nucleation and propagation has not yet been previously addressed in the literature. To study the effect of the MWL on surface freezing events, a range of surface-functionalized glass substrates were prepared. In situ monitoring of freezing events with thermal imaging allowed studying the effect of surface chemistry and environmental relative humidity (RH) on the thickness and continuity of the MWL. We argue that the observed icing nucleation and propagation kinetics are directly related to the presence and continuity of the MWL, which can be manipulated by controlling the environmental humidity and surface chemistry.