Microwave resonator sensor spots ice-accumulation

Engineers in Canada have developed a planar microwave resonator sensor that detects ice-accumulation in real-time, and advance that could improve airline safety and efficiency.

microwave resonator
UBCO graduate students Kiana Mirshahidi and Ben Wiltshire demonstrate how small and portable the tiny ice detection senor is (Image: UBCO)

The collaborative effort from the University of British Columbia’s Okanagan School of Engineering brought together one team that designs microwave sensors and microelectronics systems and another that investigates ice-repellent materials and extreme liquid repellency.

According to UBCO, the researchers aimed to develop a sensor that could detect the precise moment when ice begins to form on a surface. Due to their high sensitivity, low power, ease of fabrication, and planar profile, the team chose to use microwave resonators. The device will make it easier to detect and manage ice accumulation on aircraft, said Assistant Professor Kevin Golovin.

“The ice detection systems used today are quite rudimentary. For example, pilots visually detect ice on aircraft wings before de-icing in flight,” Golovin said 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 mechanically robust, sensitive and easy to fabricate, said 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. 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 their research findings in Sensors and Actuators B: Chemical. This is the first report on using microwave resonators to detect frost or ice accumulation, said Zarifi. The reverse is also possible, and the sensors can detect when ice is melted away during de-icing, he added.

The sensitivity and precision of the sensors means detection occurs in real-time, making ground and in-flight deicing faster, cheaper and more efficient.

“The resonator detected frost formation within seconds after the sensor was cooled below freezing,” said Wiltshire, the first author of the study. “It took about two minutes at -10C 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 recently demonstrated significant performance in sensing, monitoring and characterising solid, liquid and gaseous materials. However, research on the detection of ice and frost has not been undertaken until now, said Zarifi, despite the benefits of real-time, sensitive and robust ice detection for transportation and safety applications.

“This is a brand-new method for detecting ice formation quickly and accurately,” said Zarifi. “The radiofrequency 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.”