According to researchers at the University of California at Berkeley, future fitness trackers could soon add blood-oxygen levels to the list of vital signs they measure. By switching from silicon to an organic, or carbon-based, design, the researchers say that they were able to create a device that could ultimately be thin, cheap, and flexible enough to be slapped on like a bandage during hiking or other outdoor sports.

“There are various pulse oximeters already on the market that measure pulse rate and blood-oxygen saturation levels, but those devices use rigid conventional electronics, and they are usually fixed to the fingers or earlobe,” said Ana Arias, an associate professor of electrical engineering and computer sciences and head of the UC Berkeley team developing the new organic optoelectronic sensor.

A conventional pulse oximeter typically uses light-emitting diodes (LEDs) to send red and infrared light through a fingertip or earlobe. Sensors detect how much light makes it through to the other side. Bright, oxygen-rich blood absorbs more infrared light, while the darker hues of oxygen-poor blood absorb more red light. The ratio of the two wavelengths reveals how much oxygen is in the blood.

For the organic sensors, the team used red and green light, which yield comparable differences to red and infrared when it comes to distinguishing high and low levels of oxygen in the blood. Using a solution-based processing system, they deposited the green and red organic LEDs and the translucent light detectors onto a flexible piece of plastic. By detecting the pattern of fresh arterial blood flow, the device can calculate a pulse, they explained. And, they say that the organic electronics are cheap enough that can be considered disposable.