October 29, 2009
News View Article
Hard Rain: Pitt-led Researchers Create Nano-Particle Coating to Prevent Freezing Rain Buildup on Roads, Power LinesInspired by water-resistant lotus leaves, the Pitt-developed solution repels freezing rain and provides the first evidence of anti-icing ability in superhydrophobic coatings, team reports in “Langmuir”
PITTSBURGH-Preventing the havoc wrought when freezing rain collects on
roads, power lines, and aircrafts could be only a few nanometers away.
A University of Pittsburgh-led team demonstrates in the Nov. 3 edition
of “Langmuir” a nanoparticle-based coating developed in the lab of Di
Gao, a chemical and petroleum engineering professor in Pitt's Swanson
School of Engineering, that thwarts the buildup of ice on solid
surfaces and can be easily applied.
The paper, by lead author
and Pitt doctoral student Liangliang Cao, presents the first evidence
of anti-icing properties for a burgeoning class of water
repellants-including the Pitt coating-known as superhydrophobic
coatings. These thin films mimic the rutted surface of lotus leaves by
creating microscopic ridges that reduce the surface area to which water
can adhere. But the authors note that because ice behaves differently
than water, the ability to repulse water cannot be readily applied to
ice inhibition. Cao's coauthors include Gao, Jianzhong Wu, a chemical
engineering professor at the University of California at Riverside, and
Andrew Jones and Vinod Sikka of Ross Technology Corporation of Leola,
Pa.
The team found that superhydrophobic coatings must be
specifically formulated to ward off ice buildup. Gao and his team
created different batches made of a silicone resin-solution combined
with nanoparticles of silica ranging in size from 20 nanometers to 20
micrometers, at the largest. They applied each variant to aluminum
plates then exposed the plates to supercooled water (-20 degrees
Celsius) to simulate freezing rain.
Cao writes in “Langmuir”
that while each compound containing silica bits of 10-or-fewer
micrometers deflected water, only those with silica pieces less than 50
nanometers in size completely prevented icing. The minute surface area
of the smaller fragments means they make minimal contact with the
water. Instead, the water mostly touches the air pockets between the
particles and falls away without freezing. Though not all
superhydrophobic coatings follow the Pitt recipe, the researchers
conclude that every type will have a different particle-scale for
repelling ice than for repelling water.
Gao tested the coating
with 50-nanometer particles outdoors in freezing rain to determine its
real-world potential. He painted one side of an aluminum plate and left
the other side untreated. The treated side had very little ice, while
the untreated side was completely covered. He produced similar results
on a commercial satellite dish where the glossed half of the dish had
no ice and the other half was encrusted.
A video available on
Pitt's Web site shows an aluminum plate glazed with Gao's
superhydrophobic coating (left) repelling the supercooled water. For
the uncoated plate (right), the water freezes on contact and ice
accumulates. The video can be accessed at www.pitt.edu/news2009/ice.html
The “Langmuir” paper is available on Pitt's Web site at www.pitt.edu/news2009/DiGao.pdf
