Researchers at UT Southwestern Medical Center have designed a way to
improve electrical stimulation of nerves by outfitting electrodes with
the latest in chemically engineered fashion: a coating of basic black,
formed from carbon nanotubes.
The nanotube sheathing improves
the signals received and transmitted by electrodes, which researchers
say is a potentially critical step for advancing electrical nerve
stimulation therapy. This type of therapy increasingly shows promise
for diseases ranging from epilepsy to depression to chronic leg and
By implanting electronic nerve stimulators, doctors elsewhere have
provided a quadriplegic patient with the ability to move a computer
cursor at will, and monkeys have been able to move objects in a virtual
world with mere mind power. For individuals who lose an arm or leg and
rely on prosthetics, implanted stimulators offer promise in restoring
feelings of sensation.
"The key to success for these types of
brain-machine interfaces is where the electrode meets the nerve
tissue," said Dr. Edward Keefer, instructor of plastic surgery at UT
Southwestern and lead author of the study appearing in a recent issue
of Nature Nanotechnology. "When we coat the electrodes with carbon
nanotubes, it improves the stimulation of the nerve and the feedback
from the sensors."
Depending on the way the nanotubes are
fashioned, researchers were able to bolster either the stimulation or
receptive capabilities to improve performance. In some tests, the
nanotube coating improved performance by fortyfold, while in others it
improved by a factor of as much as 1,600.
Nanotubes look like
lattices rolled into a tube on a microscopic scale. Although they are
1/50,000 the width of a human hair, nanotubes are nonetheless among the
stiffest and strongest fibers known, as well as excellent conductors of
Those properties proved to be just the attributes
needed to help electrophysiologists conquer some of the hurdles facing
them - issues such as battery power and chemical stability.
carbon nanotube coating improves conductivity, which means less energy
is needed to power the nerve stimulator. That can help reduce routine
maintenance, such as the need to change batteries in implanted
stimulation devices, as well as reduce tissue damage caused by the
"Our process is like taking a Ford Pinto, pouring on this chemical coating, and turning it into a Ferrari," Dr. Keefer said.
have tried several types of electrochemical coatings to see if they
could improve conductivity, but the coatings often break down quickly
or fail to stay affixed to the electrodes. The carbon nanotube coating
shows far more promise, although further research is still needed, Dr.
"The development of new technologies by Dr. Keefer
to potentially restore function in wounded tissues and future
transplantations is exciting," said Dr. Spencer Brown, assistant
professor of plastic surgery who heads research in the Nancy Lee and
Perry R. Bass Advanced Plastic Surgery and Wound Healing Laboratory at
UT Southwestern Medical Center. September 2008.