Research by MSE Assistant Professor Ludovico Cademartiri and his team was published online on March 23, 2016 in Advanced Materials.
The paper, titled “Thermal Processing of Silicones for Green, Scalable, and Healable Superhydrophobic Coatings,” was co-authored by Ph.D. students Xinchun Tian, Santosh Shaw, and Kara Lind. The group found that silicones can become water-repellant after being exposed to intense heat, such as by a flame. The simplicity, and low cost of this process makes it attractive in a number of applications where such coatings are needed on large areas (as on runways, where they can prevent icing by freezing rain, or solar panels where they could prevent the accumulation of dust, or in construction).
These types of surfaces must be able to withstand environmental stressors (such as abrasion) while still possessing environmental and biological compatibility. The surfaces need to be renewable and able to be produced quickly in processes that can be easily scaled and automated so the coating can be rapidly applied. Perhaps most importantly, the surface coating must be able to withstand the wear and tear of covering such large areas. There are currently solutions that target some of these requirements but not all of them, which is what Cademartiri and his group set out to accomplish.
The group exposed silicone coatings to flames, resulting in the partial degradation of the silicone. This degradation would result in two effects: the formation of pores on the surface and the deposition of silicone “soot” in these pores. This “soot” became the coating that can then be generated and regenerated with a propane torch and can adhere to a variety of surfaces. The surface coating structure remains in place even when exposed to moderate wear and can tolerate significant foot traffic of more than 1000 steps before showing signs of wear. The coatings are environmentally friendly and remained water-repellant after being exposed to acid, UV, contamination.
Cademartiri and group hope these results will open the door to self-healing and water-repellant silicone coatings that could further simplify their application over large areas.
The full text of the Advanced Materials article can be found here.