Amyotrophic Lateral Sclerosis (ALS) affects the nerve cells that control voluntary muscle movements such as walking and talking. As a result, ALS patients often lose the ability to speak, making it difficult to communicate with others.

Read more: ALS Patients with Locked-In Syndrome May Get a Voice with This New Wearable

Now, researchers at MIT have developed a wearable skin-like sensor that can detect small deformations of the skin, potentially serving as a way to help ALS patients to communicate through facial movements. Using this approach, patients could communicate a variety of sentiments, such as “I love you” or “I’m hungry,” with small movements that are measured and interpreted by the device, reports Anne Trafton at MIT News. The wearable sensor is thin and can be camouflaged with makeup to match any skin tone, making it unobtrusive.

“Not only are our devices malleable, soft, disposable, and light, they’re also visually invisible,” says Canan Dagdeviren, the LG Electronics Career Development Assistant Professor of Media Arts and Sciences at MIT and the leader of the research team. “You can camouflage it and nobody would think that you have something on your skin.”

The researchers tested the initial version of their device in two ALS patients (one female and one male, for gender balance) and showed that it could accurately distinguish three different facial expressions — smile, open mouth, and pursed lips.

The lead authors of the study are MIT graduate student Farita Tasnim and former research scientist Tao Sun. Other MIT authors are undergraduate Rachel McIntosh, postdoc Dana Solav, research scientist Lin Zhang, and senior lab manager David Sadat. Yuandong Gu of the A*STAR Institute of Microelectronics in Singapore and Nikta Amiri, Mostafa Tavakkoli Anbarani, and M. Amin Karami of the University of Buffalo are also authors. The study appears in Nature Biomedical Engineering.

Dagdeviren’s lab, the Conformable Decoders group, specializes in developing conformable (flexible and stretchable) electronic devices that can adhere to the body for a variety of medical applications. She became interested in working on ways to help patients with neuromuscular disorders communicate after meeting Stephen Hawking in 2016, when the world-renowned physicist visited Harvard University and Dagdeviren was a junior fellow in Harvard’s Society of Fellows.

Read more: MIT Develops Smart Shirt That Can Monitor Heart Rate, Temperature and Other Vital Signs

Most ALS patients also eventually lose the ability to control their limbs. The MIT team created a wearable device that consists of four piezoelectric sensors embedded in a thin silicone film. The sensors, which are made of aluminum nitride, can detect mechanical deformation of the skin and convert it into an electric voltage that can be easily measured. All of these components are easy to mass-produce, so the researchers estimate that each device would cost around $10.