Light-Up ‘Skin-Like’ Plastic Is the Next Step for Wearables

March 30, 2022 — Imagine a tiny, stretchable, glowing Band-Aid on your finger or arm, and you are picturing the latest wearable technology advance from researchers at Stanford University.

Professors in the school of engineering there have created a new type of polymer, or synthetic plastic material, that can light up. They used it to build a flexible color display similar to what you’d see on any digital screen. But unlike your cellphone, it holds up when stretched or flexed.

The discovery is the latest in a quest to build “skin-like” wearable electronics — thin, flexible devices that promise greater comfort and accuracy than the more rigid, bulky wearables of today.

Unlike previous attempts at flexible displays, this model does not lose brightness when stretched. You can stick it to an arm or finger, and it won’t rip when you bend or flex.

The engineers say this bright, stretchy technology may someday unlock many new ways of improving health and fitness.

For example, instead of sporting a clunky fitness tracker on your wrist, imagine wearing a skin patch continually monitoring health data, like your heart rate, with the display right on the device.

Even more futuristic: Picture a telehealth appointment where a doctor would not just be able to see and hear you, but also examine the texture of your skin for problems via a flexible patch.

“Getting closer to the human body will allow us to get more information,” says chemical engineer Zhenan Bao, PhD, one of the Stanford researchers who developed the new material. Skin-like wearables are one way to get closer for all manner of measurements.

What Can We Learn From Having Light Near the Skin?

Flip over any fitness watch capable of tracking your heart rate, and you’ll see green flashing lights on its underbelly.

These LEDs beam light through the skin, which is then reflected back to the watch. The watch then uses the wavelength of that reflected light to measure things like your pulse or the oxygen in your blood (aka pulse-ox).

For accurate readings, the brighter the light, the better. Researchers have long sought to create an LED that is softer and more flexible than today’s technology, but they’ve faced three main challenges:

  • Creating a material flexible enough to stretch without breaking
  • Generating a light bright enough to capture accurate readings
  • Achieving a lower-risk voltage level to power the light (Electric shocks from wearables are not ideal.)

This new Stanford study has been 3 years in the works. In it, Bao and her research team detail how they worked through these obstacles and developed a flexible film that produces bright light at low voltage. She says the material can generate light at least twice as bright as a typical cellphone display.

Potential Future Health Applications

As future versions of this light-up material get more flexible and durable, devices made with it could measure things that wearable devices can’t today, Bao says. For example, the sound of a person’s breathing or levels of the stress hormone cortisol could provide context for common measurements like changes in heart rate, and help people understand what they mean.

“Adding cortisol makes [a reading] more precise in determining whether what’s being seen is true stress, or just a kind of fluctuation of the heart rate,” Bao says.

Skin-like displays and sensors could also change how we use electronics, Bao says. In telemedicine, for example, a person could stick the wearable film on an area of the body that needs to be examined. The wearable could then generate a three-dimensional interface, allowing the doctor to examine the area from far away.

In the meantime, more studies are already underway. Bao predicts medical and commercial use to be possible in 5 years.

“The future of this stretchy technology will lead to advancements in telemedicine because it can offer real-time information displays,” Bao says. “If we can make them truly skin-like, then the possibilities are really limited by one’s imagination. And that is what we are aiming for.”