Duke engineers develop treadwear sensors

DURHAM, N.C. — Researchers at Duke University have developed a printed sensor that they claim can monitor the treadwear of car tires in real time.

Electrical engineers at Duke's Pratt School of Engineering said the "inexpensive" sensor will warn drivers when the rubber meeting the road has grown "dangerously thin."

The product, which was developed in collaboration with Fetch Automotive Design Group, uses metallic carbon nanotubes that can track millimeter-scale changes in tread depth with 99-percent accuracy, the university said.

The university has two patents pending for the product, which uses mechanics of how electric fields interact with metallic conductors, according to Aaron Franklin, associate professor of electrical and computer engineering at Duke.

The technology relies on the well-understood mechanics of how electric fields interact with metallic conductors, researchers said. The core of the sensor is formed by placing two small, electrically conductive electrodes very close to each other; by applying an oscillating electrical voltage to one and grounding the other, an electric field forms between the electrodes.

A sensor is placed on the inside of the tire, where the tire wall and tread interferes with an electric field that arcs between the electrodes.

"That interference can be measured to determine the thickness of the rubber with millimeter accuracy," the university paper explained.

"When we pitch this idea to industry experts, they say to each other, 'Why haven't we tried that before?' " Mr. Franklin said. "It seems so obvious once you see it, but that's the way it is with most good inventions."

The sensors can be printed on almost anything using an aerosol jet printer — even on the inside of the tires themselves.

According to Mr. Franklin, whatever approach is ultimately used, the sensors should cost "far less than a penny apiece once they're being made in quantity."

Mr. Franklin's group also wants to explore other automotive applications for the printed sensors, such as keeping tabs on the thickness of brake pads or the air pressure within tires.

This is consistent with a key trend in the automotive sector toward using embedded nanosensors.