While there are already systems that estimate tire wear, electrical engineers at Duke University have developed a sensor that actually measures it in real time. Designed in collaboration with the Fetch Automotive Design Group, the relatively simple device can reportedly track millimeter-scale changes in tread depth with 99 percent accuracy.

The sensor is adhered to the inside wall of a tire, and consists of two electrodes made of carbon nanotubes. Those electrodes are printed very close to one another on a flexible polyimide film.

An oscillating electrical voltage is applied to one of the electrodes, while the other one is grounded. This creates an electrical field, most of which passes directly from the one electrode to the other. Some of the field, however, arcs up across the small gap between them. This is known as a "fringing field."

If a material such as tire rubber is occupying the space above the electrodes, it interferes with the fringing field, and that interference can be measured via the electrical response of the grounded electrode – the thicker the material that the field has to pass through, the greater the amount of interference.

Although the technology won't work when applied to purely metallic materials, the metal mesh embedded in tires doesn't present any problems.

And while the sensor currently takes the form of a decal of sorts, the electrodes could also be jet-printed directly onto the inside wall of the tire. In either case, it is estimated that when mass-produced, the sensors will cost less than one cent each. That said, there would also have to be hardware for applying the voltage, and for transmitting the readings to the driver.

The research is being led by Prof. Aaron Franklin, and is described in a paper that was recently published in IEEE Sensors Journal.

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