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Research Highlights
Nanotechnology team aims to build a better electrode
August 20, 2008
Implanted brain electrodes may one day
play an important role in restoring
independence to those with spinal cord
injury, ALS, limb loss or other conditions.
As part of technology being developed by
VA researchers and colleagues, the
electrodes would pick up brain signals and
send them to a decoder that would convert
them to signals to control computer
cursors, artificial arms or other devices.
One challenge, though, is that the
electrodes appear to lose their
effectiveness over time. This may be due
to a "mechanical mismatch" between the
rigid electrode and the surrounding soft
tissue, says polymer scientist Christoph
Weder, PhD. "The working hypothesis is
that initially the electrode needs to be stiff,
or you would not be able to implant it. But
once it's in, the brain is soft, like Jell-O,
and then you have this stiff electrode.
What you really want is an electrode that
uses as a substrate a 'smart' material—something that is stiff when it goes in and
then becomes soft."
Weder and colleagues are designing just
that. His group at Case Western Reserve
University and VA’s Advanced Platform
Technology Center, based at the Louis
Stokes Cleveland VA Medical Center, have
created a "nanocomposite" that changes
from hard to soft. They described their
invention in the journal Science earlier this
year.
"The materials on which we reported in
Science were designed to change from a
hard plastic—think CD case—to a soft
rubber when brought into contact with water," said coauthor Stuart
Rowan, PhD.
The new material is inspired by the sea cucumber, explains
Jeffrey Capadona, PhD, lead author on the Science article. “These
creatures can reversibly and quickly change the stiffness of their
skin. Normally is it very soft, but—for example, in response to a
threat—the animal can activate its 'body armor' by hardening its
dermis.” Capadona keeps one of the creatures in an aquarium at
home.
The theory is that an electrode that could morph from hard to
soft in response to water would work well in the aqueous
environment of the brain. The researchers, funded by VA and the
National Institutes of Health, are preparing to test the theory in
animals. An alternative route they are taking is to create similar
electrodes that would change their stiffness in response to an
electrical or light signal, instead of water. That could be useful, for
example, if clinicians needed to remove the electrode from the
brain of a patient and wanted to re-stiffen it.
This article originally appeared in the July/Aug 2008 issue of VA Research Currents.
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