A sensor detects the precise moment when ice begins to form on a surface. Due to their high sensitivity, low power, ease of fabrication, and planar profile, microwave resonators were chosen for the device.
Ice detection systems used currently on aircraft include pilots visually detecting ice on aircraft wings before de-icing in flight. 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 and are mechanically robust, sensitive, and easy to fabricate. The sensors provide a complete picture of the icing conditions on any surface such as 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, without altering the aerodynamic profile of the wing. The sensors can also detect when ice is melted away during de-icing.
The sensitivity and precision of the sensors means the detection occurs in real time. That could make both ground and in-flight de-icing faster, cheaper, and much more efficient.
The resonator detected frost formation within seconds after the sensor was cooled below freezing. On the other hand, it took about two minutes at -10 °C for the frost to become visible on the resonator with the naked eye.
Planar microwave resonator devices have recently demonstrated significant performance in sensing, monitoring, and characterizing solid, liquid, and gaseous materials; however, detection of ice and frost has not been undertaken previously for transportation and safety applications. The radio-frequency and microwave technology can also be made wireless and contactless.