Lab
Spotlight: Lawrence Livermore National Laboratory
Designing
Biocompatible Microelectronics
Pioneering work with
polymer-based microfabrication methods at Lawrence Livermore National
Laboratory (LLNL) is feeding into the primary component of the
Artificial Retina Project—namely, development of a flexible,
biocompatible microelectrode array.
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The
artificial retina team at Lawrence Livermore National Laboratory
includes: Front row (left) Julie Hamilton and (right) Terri
Delima. Back row, from left to right: Phillipe Tabada, Satinderpall
Pannu, and William Benett. |
A key LLNL technique
for making thin metal lines “allows us to pack many more
electrodes into a much smaller device than previous models,”
says Satinderpall Pannu, who is leading the LLNL effort. This
technique, coupled with integrated-circuit and wireless technologies,
drives the Department of Energy’s advanced retina prosthesis.
The current goal is to develop an array with hundreds of electrodes.
Micrometer
Sizing
As part of LLNL’s Center for Micro- and Nano-Technology,
Pannu and his team are applying their expertise to microelectromechanical
systems (called MEMS) that integrate micrometer-sized mechanical
elements, sensors, actuators, and electronics through microfabrication
technology.
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A
closeup view of the neural microelectrodes that make up the
artificial retina array. |
The metal traces forming
the electrodes and electronics in the array are less than a micrometer
thick, less than 1% the thickness of a human hair. Embedded in
such soft, moldable substrates as silicone, the array conforms
easily to the curved shape of the retina.
Pannu’s group
also is developing methods for integrating complementary metal
oxide silicon (called CMOS) electronics into the retinal prosthesis
to reduce its overall size and complexity.
These electronics send
electrical signals to microelectrodes to stimulate the retina,
a function normally generated by the eye’s photoreceptor
cells. In blind people suffering from retinitis pigmentosa and
age-related macular degeneration, however, this process has broken
down. The microelectrode array mimics the function of the photoreceptor
cells by electrically stimulating the remaining healthy bipolar
and ganglion cell layers.
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Advanced
ocular surgical tools developed at LLNL are used to tack the
thin-film electrode array into the retinal tissue. |
Additionally, LLNL’s
expertise is being tapped to develop advanced ocular surgical
tools that will allow surgeons to place the microelectrode array
precisely on the retina with minimal tissue damage.
Dual-Use Technology
Many of the technological advances forming the basis of this research
stem from LLNL’s role as a national security laboratory.
“This project
is a great example of LLNL’s multidisciplinary approach
to science,” says Cherry Murray, LLNL’s deputy director
of Science and Technology.
Previously, LLNL researchers
used silicone as a substrate for microfluidic devices such as
biosensors to detect and identify chemical and biological pathogens
in waterways.
Since silicone is a
biocompatible material, more recent work has focused on developing
processes for embedding metal microelectrodes and electronics
within silicone for use in biomedical devices.
“We’re
leveraging a lot of the technologies we’ve developed for
biodetection systems onto the retinal prosthesis, and vice versa,”
Pannu explains.
Future applications
for the flexible electrode array go beyond the artificial retina.
LLNL researchers are working to integrate this technology into
next-generation devices such as the cochlear implant for hearing.
The array also might be used one day to stimulate the deep brain
for treating such diseases as Parkinson’s and chronic depression,
and the spinal cord to relieve chronic pain.
“Our hope is
that this technology will evolve into a general-purpose neural
electrode array,” Pannu says, “helping to restore
eyesight in blind people and revolutionizing treatment for all
kinds of neurologically based diseases.”
LLNL is managed by
the University of California for the U.S. Department of Energy’s
National Nuclear Security Administration.
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