Understanding and controlling ice accumulation are crucial for aircraft efficiency, highway and powerline maintenance, and building construction. Currently, most de-icing systems rely on either physical or chemical removal of ice, both energy and resource-intensive. A more desirable approach would be to prevent ice formation rather than to fight its build-up. While much attention has focused on freezing of static water droplets, the first step in ice accretion is the dynamic droplet/substrate collision. In this project we analyze the behavior of dynamic droplets impacting supercooled nano- and microstructured surfaces.
We have shown that highly-ordered nanostructured materials can be designed to remain entirely ice-free down to −25 to −30°C due to their ability to repel impacting water droplets. Detailed experimental analysis of the temperature dependent droplet/surface interaction shows that the process relies on complete water retraction and bouncing off the surface before ice nucleation has a chance to occur. Ice accumulated following the nonwetting freezing transition at these temperatures can be easily removed due to its localization at the structure tips and low adherence. We have proposed a model that describes factors contributing to droplet retraction, pinning, and freezing using classical nucleation theory and wetting dynamics.
Based on our analyses, we are designing and testing a variety of sustainable, versatile, built-in ice-preventive materials. In particular, we are exploring the potential of polymeric coatings bearing closed-cell surface microstructures for their improved mechanical and pressure stability, amenability to facile large-scale fabrication, and opportunities for greater tuning of their material and chemical properties.