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Better Brain Implants With Ultrathin Carbon Fiber Electrodes



In hopes of revolutionizing implant technology, researchers have developed a new neural interface that has great potentials to improve the efficiency of future brain-computer interfaces. According to a today’s post on the new neural electrodes are delicate enough not to damage nerve tissue, but resilient enough to last decades. Made from a single carbon fiber and coated with chemicals the technology is believed to be fully resistant to the brain.

The main problem that neurons have with electrodes is that they make terrible neighbors. The new carbon fiber electrodes could eventually be used to send signals to prosthetic limbs, overcoming inflammation larger electrodes cause that damages both the brain and the electrodes.

The carbon microthread electrode is the thinnest electrode ever, only about 7 micrometers in diameter, which is about 100 times as thin as the conventional metal electrodes used to study animal brains. Developed at the University of Michigan, the electrode is 10 times smaller than the nearest competition and could make long-term measurements of neural activity practical at last.

The new electrode is unobtrusive and even friendly in comparison. It is a thread of highly conductive carbon fiber, coated in plastic to block out signals from other neurons. The conductive gel pad at the end cozies up to soft cell membranes, and that close connection means the signals from brain cells come in much clearer.

Electrical impulses travel through the brain by movements of ions, or atoms with electric charges, and the signals move through the gel in the same way. On the other side, the carbon fiber responds to the ions by moving electrons, effectively translating the brain’s signal into the language of electronic devices.

“Because these devices are so small, we can combine them with emerging optical techniques to visually observe what the cells are doing in the brain while listening to their electrical signals,” said Takashi Kozai, who led the project as a student in the laboratory of Daryl Kipke, a professor of biomedical engineering.

“This will unlock new understanding of how the brain works on the cellular and network level.” Kipke stressed that the electrode that the team tested is not a clinical trial-ready device, but it shows that efforts to shrink electrodes toward the size of brain cells are paying off.

In order to listen to a neuron for long, or help people control a prosthetic as they do a natural limb, the electrodes need to be able to survive for years in the brain without doing significant damage. With only six weeks of testing, the team couldn’t say for sure how the electrode would fare in the long term, but the results were promising.

To demonstrate how well the electrode listens in on real neurons, Kipke’s team implanted it into the brains of rats. The electrode’s narrow profile allows it to focus on just one neuron, and the team saw this in the sharp electrical signals coming through the fiber. They weren’t getting a muddle of multiple neurons in conversation.

In addition to picking up specific signals to send to prosthetics, listening to single neurons could help tease out many of the brain’s big puzzles in the future.