Measuring the electrical activity of neurons within the body is tricky, not least because it can be hard to attach electrodes to the skin and particularly a hairy scalp. But doing so is vital for neurosurgery, for example when installing brain implants that can allow disabled people to control machines using their mind.
Getting electrodes to stay in place for long periods is a particular problem, says Mingui Sun, who with colleagues at the University of Pittsburgh has an answer in the form of an electrode that screws into the skin.
The device is button-shaped, with a set of microscopic teeth horizontally aligned around the edge of its lower face (see image, right). When the button is pressed against the skin and twisted, the teeth dig into the upper layer of skin and become fixed in place, maintaining good electrical contact.
Because the teeth penetrate only the top layer of skin, the buttons should be pain-free, the patent claims.