OUR WORLD IS populated by hundreds of thousands of cyborgs. Some are Parkinson’s patients, who can shut off their tremors by activating metal electrodes implanted deep within their brains. Others—albeit far fewer—are completely paralyzed people who can move robotic limbs with their minds, thanks to their own implants. Such technologies can radically improve someone’s quality of life. But they have a major problem: Metal and the brain get along very, very poorly.
Brains have the texture of Jell-O—push on them too hard, and they’ll come apart into fragile clumps. There’s a violence to probing the brain with wires. “It’s like sticking a knife into the tissue,” says Magnus Berggren, professor of organic electronics at Linköping University in Sweden.
Worse, while electrodes remain relatively fixed in place, the brain jiggles and shifts around them, causing even more injury. The body responds by forming scar tissue, which gradually walls off the electrode from the neurons that it is supposed to record or stimulate. Because of scarring, Utah arrays—the tiny, hairbrush-like devices implanted in the brains of paralyzed people—are typically removed after around five years, and patients who have regained the ability to move or speak once again become silent and still.