Vehicular maintenance is one of the costliest aspects of owning a car. Several times a year, drivers need to take their vehicles in for oil changes, tire rotations, along with having to replace and periodically monitor certain parts and components. A car’s tires are obviously an essential part of the vehicle whose wellness needs to be constantly monitored. Since tires wear quickly the more the vehicle is driven, it makes tire replacement an inevitability, which costs Americans around $20 billion annually.
Hoping to make this process easier, a cheap printed sensor that can monitor the tread of tires in real time has been developed by electrical engineers at Duke University. When the rubber on the tire making contact with the road grows dangerously thin, the sensor issues a warning to the driver, a setup that could greatly increase safety, improve vehicle performance, and reduce fuel consumption. The Duke engineers hope their newly developed sensor becomes the first of several that could begin altering the tire and wheel control sensor market.
In a demonstration the Duke researchers conducted with Fetch Automotive Design Group, the research team showed how the sensor used metallic carbon nanotubes tracked millimeter-scale changes in tread depth with 99 percent accuracy. The collaboration of scientists and engineers have two patents currently pending, and are in the process of establishing additional partnerships throughout the industry with hopes of bringing this technology to as many people as possible.
The engineers broke down their sensor design in a paper that was published in the IEEE Sensors Journal. The device’s technology utilizes mechanics of how electric fields interact with metallic conductors. Two small electrically conductive electrodes are placed very close to each other, forming the sensor’s core. Upon applying an oscillating electrical voltage to one of these electrodes, the second one becomes grounded as an electrical field forms between the pair.
Despite some of the field arcs between the electrodes, most of the electric fields pass directly between the two. Interference within this “fringing field” is triggered when a material is placed on top of the electrodes and upon measuring that interference through the electrical response of the grounded electrode, it’s possible to determine the thickness of the material covering the sensor.
Despite having no limit to how thick material can be for this setup to detect, it’s more than enough to cover several millimeters of tread you’ll find in modern tires. The technology can easily notify drivers when it’s time to purchase a new tire set or provide information about uneven and dangerous wear with evidence of sub-millimeter resolution, and connecting several sensors in a grid to cover the width of the tire. The tests also showed the embedded metal mesh within the tires doesn’t disrupt the operation of new sensors.
While the device could be composed from a variety of materials and methods, the publication notes how the researchers maximized the sensor’s performance through the exploration of numerous variables from sensor size and structure, to substrate and ink materials. The best results were attained when electrodes comprised of metallic carbon nanotubes were printed on a flexible polyimide film.
Aside from providing the best results, more than enough durability to survive the harsh conditions within the tire is provided for the sensor by the metallic carbon nanotubes. The sensors are printable on almost anything with an aerosol jet printer, which can even print the sensors inside the actual tire. Despite some uncertainty that direct printing will be the best manufacturing approach, any of the aforementioned methods that wind up being used should be significantly cheaper (less than a penny each) when produced on a larger scale.
The researchers also hope to explore other automotive applications for these sensors, like monitoring the thickness of brake pads or tire’s air pressure. This is consistent with a key trend in the automotive industry of an increasing shift towards utilizing embedded nanosensors, which we should see a lot more of in the immediate future.
Filed Under: M2M (machine to machine)