Ice buildup on the wings of aircraft can quickly cause problems if not detected early enough. Researchers at the University of British Columbia Okanagan's School of Engineering have developed a sensor that can detect the precise moment when ice begins forming on a surface. This capability could prevent tragedies linked to icy airplane wings.
After studying several approaches, the researchers chose to use microwave resonators due to their high sensitivity, low power, ease of fabrication and planar profile.
Present ice detection systems are relatively primitive. “For example, pilots visually detect ice on aircraft wings before de-icing in flight," said Assistant Professor Kevin Golovin, who runs the Okanagan Polymer Engineering Research and Applications Lab, in a statement. "And on the tarmac, certifying that the aircraft is free of ice after de-icing is also done by visual inspection, which is susceptible to human error and environmental changes."
Planar microwave resonator sensors are simple traces of metal deposited onto a plastic. Yet, they are mechanically robust, sensitive and easy to fabricate, explains Assistant Professor Mohammad Zarifi, head of UBCO's Microelectronics and Advanced Sensors Laboratory.
"The sensors give a complete picture of the icing conditions on any surface, like an airplane wing,” said Zarifi. “They can detect when water hits the wing, track the phase transition from water to ice, and then measure the thickness of the ice as it grows, all without altering the aerodynamic profile of the wing."
The pair, along with graduate students Benjamin Wiltshire and Kiana Mirshahidi, published research findings in Sensors and Actuators B: Chemical. The research is reportedly the first on using microwave resonators to detect frost or ice accumulation, according to Zarifi. The reverse is also possible, and the sensors can detect when ice is melted away during de-icing, he adds.
The sensor’s ability to detect ice buildup in real time could make both ground and in-flight de-icing faster, cheaper, and much more efficient, according to the researchers.
"The resonator detected frost formation within seconds after the sensor was cooled below freezing," explains Wiltshire, the first author of the study. "It took about two minutes at -10°C for the frost to become visible on the resonator with the naked eye—and that's in one small area in ideal lab conditions. Imagine trying to detect ice over an entire wingspan during a blizzard."
Planar microwave resonator devices have successfully been used to sense, monitor, and characterize solid, liquid and gaseous materials. However, research on ice and frost detection has not been undertaken until now, says Zarifi, despite their clear benefits for ice detection in transportation and safety applications.
"This is a brand-new method for detecting ice formation quickly and accurately," says Zarifi. "The radio frequency and microwave technology can even be made wireless and contactless. I wouldn't be surprised if airlines start adopting the technology even for this upcoming winter."