PHILADELPHIA Wear is a fact of life. As surfaces rub against one another, they break down and lose their original shape. With less material to start with and functionality that often depends critically on shape and surface structure, wear affects nanoscale objects more strongly than it does their macroscale counterparts.
Worse, the mechanisms behind wear processes are better understood for things like car engines than nanotech devices. But now, researchers at the University of Pennsylvania's School of Engineering and Applied Science have experimentally demonstrated one of the mechanisms behind wear at the smallest scale: the transfer of material, atom by atom, from one surface to another.
The research was conducted by Tevis Jacobs, a doctoral student in the Department of Materials Science and Engineering, and Robert Carpick, department chair of Mechanical Engineering and Applied Mechanics.
Their research was published in the journal Nature Nanotechnology.
On the nanoscale, wear is mainly understood through two processes, fracture and plastic deformation. Fracture is where large pieces of a surface break off at once, like when the point of a pencil snaps off in the middle of a sentence. Plastic deformation is what happens when the surface changes shape or compresses without breaking, like when the edge of knife gets dull or bent.
These mechanisms typically affect thousands or millions of atoms at a time, whereas nanoscale wear often proceeds through a much more gradual process. Determining the mechanisms behind this more gradual process is key to improving such devices.
"At the nanoscale, wear is a very significant problem," Jacobs says. "Nanotechnology is developing smaller and smaller parts for very tiny machines. Their contact interfaces wear out very quickly, sometimes surviving for hundreds of cycles when they need to survive for trillions or more."
One wear mechanism that had
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University of Pennsylvania