Electronic devices get smaller and more complex every year. It turns out that
fragility is the price for miniaturization, especially when it comes to small
devices, such as cell phones, hitting the floor. Wouldn't it be great if they
bounced instead of cracked when dropped?
A team of Clemson University
researchers, led by Apparao Rao, professor of physics, has invented a way to
make beds of tiny, shock-absorbing carbon springs which possibly could be used
to protect delicate objects from damaging impacts. With collaborators at the
University of California at San Diego, the team has shown that layers of these
tiny springs called coiled carbon nanotubes, each a thousand times smaller than
a human hair, can act as extremely resilient shock absorbers.
Similar coiled carbon nanotubes have been made before, yet Clemson researchers
say this method is unique since beds of coiled carbon nanotubes can be grown
in a single step using a proprietary hydrocarbon-catalyst mixture.
The group also envisions coiled nanotubes in soldiers' body armor, car bumpers
and bushings and even as cushioning elements in shoe soles.
"The problem we have faced in the past is producing enough of these coiled
carbon nanotubes at a reasonable cost to make a difference," said Rao.
"Because our current method produces coiled nanotubes quickly in high yield,
it can be readily scaled up to industrial levels. After formation, the coiled
nanotubes can be peeled off in one piece and placed on other surfaces to form
instant cushioning coatings."
In earlier studies, Rao and his team, along with UCSD collaborators, tested
more conventional straight carbon nanotubes against coil-shaped nanotubes. When
a stainless steel ball was dropped onto a single nanotube layer, the coiled
nanotubes completely recovered from the impact, while the straight ones did
"It's like an egg toss," said Rao. "If you move your hand backward
as you catch the egg and increase the time of contact over which the impact
occurs, the impact will be less forceful and the egg will not break. It is the
same phenomenon experienced in catching a baseball."
In previous work, Rao's group developed a process that coaxes a traditionally
straight carbon nanotube to split into a "Y" shape. When powered by
electrical voltages, the Y-branched nanotubes behave like tiny switches or transistors
that process information.
"Our studies with carbon nanotubes have been ongoing for quite some time,"
said Rao. "Each step along the way has led to the next breakthrough, and
each time we've learned more about how they grow and what their applications
could be. We believe that carbon nanotubes have tremendous potential for the
lives of each one of us."