Researchers from Northwestern University and University of California have developed a strategy that prevents frost formation - the team reported a hybrid surface design that passively controls the diffusion of water vapor over a surface to sustain flat frost-free regions for long periods of time. The hybrid anti-frosting technique can prevent frosting for potentially weeks at a time and is scalable, durable and fabricated through 3D printing.
The team found that tweaking the texture of any surface and adding a thin layer of graphene oxide prevents 100% of frost from forming on surfaces for one week or potentially even longer. This is 1,000 times longer than current, state-of-the-art anti-frosting surfaces. As a bonus, the new scalable surface design is also resistant to cracks, scratches and contamination.
By incorporating the textured surface into infrastructure, the researchers believe that companies and government agencies could save billions of dollars per year in averted maintenance costs and energy inefficiencies.
The new study builds upon previous work from Northwestern’s Kyoo-Chul Kenneth Park's laboratory. In 2020, Park and his team discovered that adding millimeter-scale textures to a surface theoretically reduced frost formation by up to 80%. The research was inspired by the rippling geometry of leaves.
“There is more frost formation on the convex regions of a leaf,” Park said at the time. “On the concave regions (the veins), we see much less frost. People have noticed this for several thousands of years. Remarkably, there was no explanation for how these patterns form. We found that it’s the geometry — not the material — that controls this.”
Through experimental work and computation simulations, Park and his collaborators found that condensation is enhanced on the peaks and suppressed in the valleys of wavy surfaces. The small amount of condensed water in the valleys then evaporates, resulting in a frost-free area.
In the previous study, Park’s team developed a surface featuring millimeter-scale peaks and valleys with small angles in between. In the new study, Park’s team added graphene oxide on flat valleys, which reduced frost formation by 100% in those valleys. The new surface comprises tiny bumps, with a peak-to-peak distance of 5 millimeters. Then a thin layer of graphene oxide, just 600 microns thick, coats the valleys between peaks.
As graphene oxide can attract water vapor and confines water molecules within its structure, the GO layer acts like a container to prevent water vapor from freezing. When the team combined graphene oxide with the macrotexture surface, it resisted frost for long times at high supersaturation. The hybrid surface becomes a stable, long-lasting, frost-free zone, the team explained.
When compared to other state-of-the-art anti-frosting surfaces, Park’s method was said to have major advantages. While superhydrophobic (water repelling) and lubricant-infused surfaces resisted 5-36% of frost formation for up to 5 hours, Park’s surface resisted 100% of frost formation for 160 hours.
“Most other anti-frosting surfaces are susceptible to damage from scratches or contamination, which degrades surface performance over time,” Park said. “But our anti-frosting mechanism demonstrates robustness to scratches, cracks and contaminants, extending the life of the surface.”
