In a winter of seemingly endless snow and ice, what if there were a better way of fortifying roads against potholes?
What if this same technology could be used to build stronger bridges, create solar panels, even penetrate and selectively kill cancer cells?
They're called nanocrystals — particles so small that their width measures about 1/80,000 of the diameter of a single strand of hair. And they are so light and so strong that NASA once said they theoretically could be used to build an elevator to the moon.
"The excitement to me was that they could be made out of almost anything," said Thomas Webster, chairman of Northeastern University's Department of Chemical Engineering, "and by shrinking that thing down in size, you could change its properties."
One way to do this is to start with the material in its normal form and evaporate it into individual atoms by heating it, Webster said. The degree of heat necessary depends on the material and can range from about 100 degrees to melt a polymer such as Tupperware, to as much as 9,000 degrees to melt metal. Then the atoms are collected on a cold surface, where they condense and form nanocrystals.
These tiny particles improve the strength of materials such as metal and concrete. Webster also is looking at using a combination of selenium nanoparticles, which have anti-cancer properties, and iron oxide nanoparticles, which are magnetic.
"So one can use a magnetic force to force the selenium and iron oxide nanoparticles to only go into cancer cells, and not healthy cells, to thus selectively kill cancer cells," he said. "This provides a much better solution than chemotherapy, which kills all cells."
But back to those potholes — about 6,000 of which the Boston Public Works Department filled in January and February, up nearly 400 percent from the same period last year.
Nanocrystals of asphalt could be used to keep roads from forming as many potholes by filling cracks as they begin to form and grow, Webster said, and nanocrystals of road salt could be used to keep ice from forming or to melt it more quickly by increasing the surface area to decrease the freezing point.
"To me, that is how to get the best of both worlds, using nanotechnology," he said.
So why not use that technology now? The main reason, Webster said, is the cost of heating materials.
"Some of the nanocrystals we make cost upwards of $100 per milligram," he said. "So even though using nanocrystals will make a road last longer and probably save you money in the long run on repairs to both the road and your car, filling an average-sized pothole would cost about $5,000 today."
Webster is optimistic, however, that if industry partners with universities, together they would be able to reduce the cost within the next five years.
"And then," he said, "the possibilities are endless."
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