The quest to give locked-in patients a lifeline, a way to communicate once ALS or another disease has shut down their muscle control, is ongoing. One way to get hands-free input, in this case or for anyone who can only operate his or her eyes—or just someone who has both hands occupied—is to track eye blinks. It’s not an easy device to get working, as it can be hard for a computer to tell the difference between an intentional blink and a reflexive one, but a team from Chongquing University in China thinks they have it cracked.
In a paper in Science Advances, Zhong Lin Wang and his colleagues describe a device, mounted to a pair of eyeglasses, that lies gently against the skin beside the eye and can feel the pressure, in the form of an electrical signal, as the skin presses against it during a blink.
“This is a very exciting discovery that uses a very old phenomenon, but new technology, new innovations, something we never thought of before,” says Wang, who is a professor of nanoscience at Georgia State University.
Inventors have been using eye blinks to communicate with those in the latter stages of ALS or locked-in patients who otherwise have lost the use of their bodies aside from the ability to blink. A camera trained on the eyes can track blinks, but it’s not a very streamlined tool, and requires an external power source. So researchers explored tracking the difference in electromechanical potential between the cornea and retina, using a tool similar to an EEG. But this method relies on reading the body’s own electricity, and the noise is high and resolution low on these readings, making it hard to discern intentional blinks.
A few years ago, Wang and colleagues had leveraged an old scientific phenomenon, triboelectricity—electricity generated by friction, also known as static electricity—to build a small device to capture energy from the human body, called a TENG, or triboelectric nanogenerator. As previously covered by Smithsonian.com, the small device doesn’t produce much energy, but the voltage is significant enough to be easily measured by a computer and used as input. And it’s also low-cost, and doesn’t require any energy to run, which makes it useful for the types of self-powered sensors that are becoming popular in medical devices or the Internet of Things. Wang’s paper offers a long list of advantages: It’s “noninvasive, highly sensitive …, easy-to-fabricate, stable, small, light, transparent, flexible, skin-friendly, low-cost, durable, and reusable,” to name just a few.
Thus, it’s useful as an eye sensor. When placed on the temple of the glasses, the sensor sits gently against the wrinkle beside the user’s eye. That skin flexes slightly outward during a blink, bending the nanogenerator and sending an electrical signal.
For now, Wang and his colleagues are focusing on the medical devices. They’ve already programmed the device to react to a two-blink “double-click” and created a scrolling keyboard that allows the user to blink once, twice, or thrice, to select one of three letters within each row, though more elaborate typing systems could be built in the future. Tests, which were limited to sharing the device around the lab, have the authors believing it will not only improve medical care for the elderly and handicapped, but also lead to advances in robotics and other computer-human interfaces.
Closer on the horizon are consumer electronics based on the glasses, which could offer additional ways to interact with games or remote-control robots while your thumbs are occupied with the controller.
Peter Lund, an engineering physics professor at Aalto University in Finland, who works in sustainable energy, finds the work promising.
“It’s really fascinating to see how this miniaturization, what he’s doing, brings energy closer to the human beings,” says Lund.