Future Of Driving

3D Printed Sensors Can Reveal Tire Wear

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How do you know when your car tires need to be replaced? You could eyeball it, you could guess, or you could wait until they shred off your rims while you're barreling down the highway, flinging mangled rubber across a two-mile stretch of asphalt and depositing your car in a ditch.

Alternately, Duke University engineers and the Fetch Automotive Design Group have figured out a way to sense the wear of car tires down to a fraction of a millimeter to determine if it's in need of replacement. This technology already existed in expensive forms; in fact, there's a $2 billion tire and wheel sensor market. But these electrical engineers discovered how to do it inexpensively, and they used 3D printing to do it. This could mean that future cars will have built-in tire sensors, saving time, money, and even lives.

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A demonstration of the printed carbon nanotubes on a flexible surface. The prototype tire tread sensor (middle) is flanked by the logos of Duke University and Fetch Automotive Design Group.

Putting Two Heads Together

The sensor is comprised of two electrodes placed on the underside of the rubber tire. When they're placed next to each other, one can conduct an electric current while the other grounds the electric current. The electric current measures the thickness by passing through the tire with 99 percent accuracy, and that data is then delivered to the driver.

The engineers were able to pack so much tech in a cheap, unobtrusive way by 3D printing the two electrodes, which are comprised of metallic carbon nanotubes 10 million times thinner than a centimeter in diameter. Amazingly, they can be printed directly onto the tires using an aerosol jet printer, which prints high resolution electronic circuits and components on 2D and 3D surfaces.

Associate professor of electrical and computer engineering at Duke University Aaron Franklin pointed out that the use of measuring thickness through an electric current is nothing new. When he and the team present the idea to industry people, they wonder why this hadn't been thought of until now. (The same was probably said for the self-twirling spaghetti fork.)

An illustration of how the novel tread sensor works. The sensor is placed on the inside of the tire, where the tire wall and tread interferes with an electric field that arcs between two electrodes. That interference can be measured to determine the thickness of the rubber with millimeter accuracy.

"Wear" Will It Go?

While the first step is to have the technology attached to as many cars as possible, the sensors can be used to measure the thickness of anything that's not made of metal and not too thick that the current can't pass through it. And for all you motorheads, testing actually showed that the metallic mesh inside tires does not negatively affect the sensor's readouts.

When people are able to see exactly how much wear is on their tires, they can get them replaced when needed, and can avoid popping a tire in general, much less while going 70 mph on the highway. While the nanofibers garnered the best results at this point, it is also possible to print the technology using ink, which isn't necessary important as it just fascinating.

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