Scientists have invented a liquid ink that doctors can print onto a patient's scalp to measure brain activity. The technology offers a promising alternative to the cumbersome process currently used for monitoring brainwaves and diagnosing neurological conditions.

For nearly a century, EEGs have helped scientists and doctors measure the electric pulses that fire through our brains, diagnosing everything from epilepsy to traumatic brain injuries. But they’ve always come with strings attached — literally.