Technology Review - Connecting a human brain to a computer is as much a materials science problem as a biology one. What kind of interface is delicate enough not to damage nerve tissue, but resilient enough to last decades?
Researchers have come up with what they call a “stealthy neural interface” made from a single carbon fiber and coated with chemicals to make it resistant to proteins in the brain.
The new microthread electrode, designed to pick up signals from a single neuron as it fires, is only about 7 micrometers in diameter. That is the thinnest yet developed, and about 100 times as thin as the conventional metal electrodes widely used to study animal brains.
An electrode made from a carbon fiber thread is 7 micrometers wide
Nature Materials - Ultrasmall implantable composite microelectrodes with bioactive surfaces for chronic neural interfaces
“We want to see an electrode that lasts 70 years.”
Researchers need long-lasting electrodes in order to improve brain-machine interfaces. These systems, in preliminary studies, have allowed paralyzed people to control robotic limbs or a computer mouse. By using electrodes to record the firing of individual brain cells, scientists have learned to decode these signals as representing the movement of a rat’s whiskers or a quadriplegic’s effort to move his arms
ABSTRACT - Implantable neural microelectrodes that can record extracellular biopotentials from small, targeted groups of neurons are critical for neuroscience research and emerging clinical applications including brain-controlled prosthetic devices. The crucial material-dependent problem is developing microelectrodes that record neural activity from the same neurons for years with high fidelity and reliability. Here, we report the development of an integrated composite electrode consisting of a carbon-fibre core, a poly(p-xylylene)-based thin-film coating that acts as a dielectric barrier and that is functionalized to control intrinsic biological processes, and a poly(thiophene)-based recording pad. The resulting implants are an order of magnitude smaller than traditional recording electrodes, and more mechanically compliant with brain tissue. They were found to elicit much reduced chronic reactive tissue responses and enabled single-neuron recording in acute and early chronic experiments in rats. This technology, taking advantage of new composites, makes possible highly selective and stealthy neural interface devices towards realizing long-lasting implants.
13 pages of supplemental material
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