SEE THROUGH SENSORS OPEN NEW WINDOW IN TO THE BRAIN
Developing invisible
implantable medical sensor arrays, a team of University of Wisconsin-Madison
engineers has overcome a major technological hurdle in researchers' efforts to
understand the brain.
The team described
its technology, which has applications in fields ranging from neuroscience to
cardiac care and even contact lenses, in the Oct. 20 issue of the online
journal Nature Communications.
Neural researchers
study, monitor or stimulate the brain using imaging techniques in conjunction
with implantable sensors that allow them to continuously capture and associate
fleeting brain signals with the brain activity they can see. However, it's
difficult to see brain activity when there are sensors blocking the view.
"One of the
holy grails of neural implant technology is that we'd really like to have an
implant device that doesn't interfere with any of the traditional imaging diagnostics,"
says Justin Williams, a professor of biomedical engineering and neurological
surgery at UW-Madison. "A traditional implant looks like a square of dots,
and you can't see anything under it. We wanted to make a transparent electronic
device."
The researchers
chose graphene, a material gaining wider use in everything from solar cells to
electronics, because of its versatility and biocompatibility. And in fact, they
can make their sensors incredibly flexible and transparent because the
electronic circuit elements are only 4 atoms thick -- an astounding thinness
made possible by graphene's excellent conductive properties. "It's got to
be very thin and robust to survive in the body," says Zhenqiang (Jack) Ma,
a professor of electrical and computer engineering at UW-Madison. "It is
soft and flexible, and a good tradeoff between transparency, strength and
conductivity."
Drawing on his
expertise in developing revolutionary flexible electronics, he, Williams and
their students designed and fabricated the microelectrode arrays, which --
unlike existing devices -- work in tandem with a range of imaging technologies.
"Other implantable microdevices might be transparent at one wavelength,
but not at others, or they lose their properties," says Ma. "Our
devices are transparent across a large spectrum -- all the way from ultraviolet
to deep infrared. We've even implanted them and you cannot find them in an MR
scan."
The transparent
sensors could be a boon to neuromodulation therapies, which physicians
increasingly are using to control symptoms, restore function, and relieve pain
in patients with diseases or disorders such as hypertension, epilepsy,
Parkinson's disease, or others, says Kip Ludwig, a program director for the
National Institutes of Health neural engineering research efforts.
"Despite remarkable improvements seen in neuromodulation clinical trials
for such diseases, our understanding of how these therapies work -- and
therefore our ability to improve existing or identify new therapies -- is rudimentary."
Currently, he says,
researchers are limited in their ability to directly observe how the body
generates electrical signals, as well as how it reacts to externally generated
electrical signals. "Clear electrodes in combination with recent
technological advances in optogenetics and optical voltage probes will enable
researchers to isolate those biological mechanisms. This fundamental knowledge
could be catalytic in dramatically improving existing neuromodulation therapies
and identifying new therapies."
The advance aligns
with bold goals set forth in President Barack Obama's BRAIN (Brain Research
through Advancing Innovative Neurotechnologies) Initiative. Obama announced the
initiative in April 2013 as an effort to spur innovations that can
revolutionize understanding of the brain and unlock ways to prevent, treat or
cure such disorders as Alzheimer's and Parkinson's disease, post-traumatic
stress disorder, epilepsy, traumatic brain injury, and others.
While the team
centered its efforts on neural research, they already have started to explore
other medical device applications. For example, working with researchers at the
University of Illinois-Chicago, they prototyped a contact lens instrumented
with dozens of invisible sensors to detect injury to the retina; the UIC team
is exploring applications such as early diagnosis of glaucoma.
Additional authors
on the Nature Communications paper include UW-Madison electrical
and computer engineering graduate students Dong-Wook Park and Solomon Mikael,
materials science graduate student Amelia A. Schendel, biomedical engineering
research specialist Sarah K. Brodnick; biomedical engineering graduate students
Thomas J. Richner, Jared P. Ness and Mohammed R. Hayat; collaborators Farid
Atry, Seth T. Frye and Ramin Pashaie of the University of Wisconsin-Milwaukee;
and Sanitta Thongpang of Mahidol University in Bangkok, Thailand.
The researchers are
patenting their technology through the Wisconsin Alumni Research Foundation.
Funding for the research came from the U.S. Defense Advanced Research Projects
Agency, the National Institutes of Health, and the U.S. Office of Naval
Research.
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