In people with epilepsy, the device could be used to detect when seizures first begin, and deliver pulses to shut the seizures down. In people with spinal cord injuries, the technology has promise for reading complex signals in the brain that direct movement, and routing those signals to healthy muscles or prosthetic devices.
"The focus of our study was to make ultrathin arrays that conform to the complex shape of the brain, and limit the amount of tissue damage and inflammation," said Brian Litt, an author on the study. The new silk-based implants can hug the brain like shrink wrap, collapsing into its grooves and stretching over its rounded surfaces, according to the researchers. The study shows that the thin flexible implants can record brain activity more faithfully than thicker implants embedded with similar electronics.
The implants contain metal electrodes that are 500 microns thick, or about five times the thickness of a human hair. The absence of sharp electrodes and rigid surfaces should improve safety, with less damage to tissue. Also, the implants' ability to mold to the brain's surface could provide better stability; the brain sometimes shifts in the skull and the implant could move with it. Finally, by spreading across the brain, the implants have the potential to capture the activity of large networks of brain cells, Litt said.
Besides its flexibility, silk was chosen as the base material because it is durable enough to undergo patterning of thin metal traces for electrodes and other electronics. It can also be engineered to avoid inflammatory reactions, and to dissolve at controlled time points, from almost immediately after implantation to years later. The electrode arrays can be printed onto layers of polyimide (a type of plastic) and silk, which can then be positioned on the brain.
The researchers tested the ability of these implants in animals. By recording signals from the brain's visual center in response to visual stimulation, they found that the thin polyimide-silk arrays captured more robust signals compared to thicker implants.
MEDICA.de; Source: NIH/National Institute of Neurological Disorders and Stroke