Swiss researchers are developing a new road asphalt that closes up cracks on its own using magnetic nanoparticles

They're a common sight on many roads and the bane of motorists' lives, but potholes could soon be a thing of the past thanks to nano-technology. Researchers in Switzerland have patented a method that repairs stress-induced cracks in asphalt to prevent potholes forming in the first place and could double the life span of roads embedded with the technology.

A precise amount of iron oxide nanoparticles are mixed with bitumen - the sticky, viscous black binder obtained from crude oil and used to keep road material together. Ever-so slightly heating up this asphalt using a small magnetic field melts the bitumen, allowing it to seep into the minute cracks to 'self-heal'.

Etienne Jeoffroy from the Complex Materials lab at ETH Zurich and Empa (the Swiss Institute for Materials Science) is part of the team that created a magnet eic nano-particulate additive that gives asphalt self-healing properties.

"The idea is that we have nanoparticles fused with this binder [the bitumen]," Jeoffroy told Reuters. "The idea is to focus on this binder and to heat it up so that it can flow slowly and close the cracks."

Roads are exposed to a lot of mechanical and thermal stress, as well as environmental effects. Nano-technology would not prevent stress-induced cracks from ever forming again. But a once-yearly application of an electromagnetic field to the road would repair them, said Jeoffroy, and potentially double their lifetime.

"You apply a little bit of the magnetic field and it's sufficient to make the black binder liquid enough to flow inside the micro cracks. When you repeat this every year you will be able to double the lifetime of the road," he said.

Jeoffroy concedes that entire roads will need to be constructed using this nano-tech infused bitumen to make it completely self-healing. But the embedded magnetic nanoparticles are added to the asphalt during its preparation and then applied to the road surface as normal; meaning no additional skills or equipment are needed.

Eventually he envisions vehicles equipped with magnetic field generators that would simply drive over the new road, remotely exciting the magnetic nanoparticles and starting the healing process.

"The idea is to have a truck that would carry this magnetic field with a large coil to cover the maximum surface. With this process you'll only need to close the road for a few hours and you have time to go with your truck over the road and in a few seconds locally the road will be heated at the temperatures where the binder is flowing."

Jeoffroy added that the nanoparticle additive could also be used on existing roads to help repair potholes; acting like a skin graft to form a new layer of road surface.

"You can have a little of the nanoparticles inside the mixture, and apply a magnetic field locally to give enough temperature to make the joint between the new material and the old road," he said.

The team is now looking to work with commercial partners who can scale-up the system and find the most cost-effective method to use the technology in the real world.

In a separate project Erik Schlangen, a materials scientist at Delft University in the Netherlands, is developing self-healing asphalt, mixed with tiny steel fibres.

Produced by Jasper Pickering. Special thanks to Leon Siciliano.

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