October 26th, 2017
Ice and frost may be picturesque hallmarks of winter, but they come with an expensive trade-off. Delayed flights, frost-laden car windshields, and power outages are inconveniences caused by ice that add up to billions of dollars lost for companies and consumers every year.
A Virginia Tech student research team based in the Department of Biomedical Engineering and Mechanics set out to tackle the ice problem. Now their invention of passive anti-frosting surfaces has qualified the team as one of six finalists in the National Inventors Hall of Fame Collegiate Inventors Competition.
Team members will travel to Alexandria, Virginia, on Nov. 1-3 to present their research and a working prototype to a panel of famous inventors at the United States Patent and Trademark Office.
The team’s passive anti-frosting technology forgoes traditional methods of fighting ice, such as antifreeze chemicals and energy inputs. Instead, the technology harnesses the unique qualities of ice itself to prevent frost formation.
Using a simple approach to design, the researchers created an anti-frosting surface on untreated aluminum by patterning ice stripes onto a microscopic array of elevated grooves. The low pressure of the ice formed on these grooves attracts nearby moisture from the air, allowing the intermediate surface area to stay completely dry, even in humid, sub-freezing conditions.
“To date, there has never been a single example of a passive anti-frosting surface, meaning no surface in existence today can indefinitely keep the majority of the surface dry without using any chemicals or energy,” said Jonathan Boreyko, an assistant professor in the Department of Biomedical Engineering and Mechanics and the team’s faculty advisor.
“No one has ever done that until now,” he said.
The passive anti-frosting technology may also help to offset traditional methods of fighting ice that carry troubling implications for the environment. For example, it takes thousands of gallons of antifreeze chemicals to defrost the wings of one airplane for a single flight. Those chemicals run off into groundwater, get dispersed into the air as tiny droplets, and may have lasting effects on vegetation and wildlife — even people.
This technology had its first breakthrough in Boreyko’s Nature-Inspired Fluids and Interfaces Laboratory in the summer of 2016. The research team, consisting of then-undergraduate Grady Iliff, then-master’s student Saurabh Nath, and doctoral student Farzad Ahmadi — all of Virginia Tech’s engineering mechanics program — realized they could stop frost from growing around a single piece of ice.
The researchers concluded that if they could arrange multiple ice pieces into the right pattern, all of the dry zones around those ice pieces would overlap to keep the rest of the surface dry.
Building on the previous work of Boreyko and other students, the team developed a working prototype of their anti-frosting surface after several months of testing, modeling, and experiments. The microscopic grooves on the elevated ridges act as sacrificial areas, where stripes of intentional ice form and create low pressure zones. These low-pressure areas pull nearby moisture from the air onto the nearest ice stripe, keeping the intermediate areas dry and free of frost.
“We ran the experiment for more than 24 hours, and the surface was still preventing frost from forming,” said Ahmadi, now a fourth-year Ph.D. student in the engineering mechanics program. “In that time, the surface itself was almost completely free of condensation and frost, even though the temperature was 10 degrees below freezing in a very humid environment.”
The surface’s simple design, coupled with its passive approach, means it will be cheaper and easier to implement than other anti-frosting technologies. The lack of a surface treatment or robust roughness also makes the material more durable. Industrial applications for the surface include car windshields, airplane wings, power transmission lines, and HVAC systems.
“There’s no surface coating, no fancy lab tricks,” said Boreyko of the invention. “We’ve been using the same surfaces in the lab for over a year now, and they still work.”
The project has received funding through the National Science Foundation and the 3M Company. The researchers plan to pursue practical industrial applications for the technology in future studies.
Written by Emily Roediger