Putting on diamonds means you want to look your absolute best. Thanks to nanotechnology,
diamonds may let you be your best on the inside, too. As this ScienCentral
news video reports, coatings made from incredibly tiny diamonds could help
artificial joints work better and last longer.
Nano Diamonds: Your New Best Friend
Every year, according to the National
Center for Health Statistics, about 550,000 Americans undergo surgery
to receive artificial hips or knees—and as baby boomers age, that number
is expected to grow by ten percent yearly. Right now, the most durable implants
are made of stainless steel or titanium. But friction from daily use can loosen
or wear
them down after only about ten years. Abrasion can cause pain, infection,
and finally, crumbling implants. Any active person with an artificial joint
may have to endure more surgery to get another replacement.
At the University of Alabama,
Birmingham, physicist Yogesh
Vohra is interested in extending the life of artificial joints—to
about 40 years—while improving their wearers’ comfort and health.
To do that, he has turned to the hardest material on earth: diamond.
Scientists have been growing
diamonds in laboratories for about 50 years. Resilient diamond coatings
already make tools tougher and even
protect teeth. But, Vohra points out, most designer diamonds are faceted
crystals, with surfaces pocked with peaks and valleys. Coatings made with
faceted diamonds need expensive polishing. Otherwise, they may scratch metal
implants and remain too rough to adhere to bones inside the body.
Vohra's "nanodiamond" film could one day coat artificial hip joints like this one.
A lucky accident led Vohra to a solution. He and his
research team had been working on ways to grow diamonds for new materials.
In 2001, the researchers were struggling to design diamonds that would stick
to metal. One day, the lab’s gas reactor in which they were growing
diamond crystals sprang a small leak, adding a little air to their careful
combination of hydrogen and methane gases. The team was amazed to find that
the batch of diamonds came out very, very smooth, adhering easily to metal.
When they retraced their steps and tried the experiment again, they found
that nitrogen, the
main ingredient in air, had made the crucial difference. Nitrogen, Vohra
explains, had prevented the diamond crystals from growing larger than a few
nanometers. If diamonds stay that small, they don’t grow a faceted surface,
but remain smooth. The researchers had stumbled on a way to grow what Vohra
calls “nanostructured diamond.” When they combined these incredibly
tiny diamonds with a carbon-based film, nitrogen “provided the glue,”
allowing the diamond crystal to adhere to metal.
Vohra’s new shatter-proof film could improve artificial joints with a
coating that combines diamond’s traditional toughness with smoothness.
By working on the nanoscale, Vohra says, “you gain a lot in reducing
the surface roughness, but you have not sacrificed the important properties
of diamond. The nanoscale reduces surface friction as much as you can with
hard materials. Nanostructured diamond coating means that implants can take
sudden shocks or changes in stress levels.” For example, Vohra says,
if a woman with an artificial hip or knee stands up in very high heels, her
implant’s nanostructured diamond surface could absorb the extra mechanical
stress—and last longer.
Recently, Vohra has been “taking a baby step, testing a small implant,
and our preliminary results are encouraging.” He has applied his new
coating to metal mandibular joints, needed for jaw replacements. Vohra found
that implants coated with his nanodiamonds attach better to bone than uncoated
titanium implants do. Although implants coated with his film have yet to be
tested in people, Vohra believes that the advantages of nanodiamonds are so
great that they could outshine the current generation of implants.
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