Organic optoelectronic sensors for healthcare applications

Engineers at UC Berkeley have developed a pulse oximeter composed of all-organic optoelectronics that measures arterial oxygen saturation and heart rate as accurately as conventional, silicon-based pulse oximeters. The device is flexible enough to be used like a bandaid.

“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 that is developing the 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, Arias and her team of graduate students - Claire Lochner, Yasser Khan and Adrien Pierre - 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.

Image by Yasser Khan.

Using a solution-based processing system, the researchers 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.

“We showed that if you take measurements with different wavelengths, it works, and if you use unconventional semiconductors, it works,” said Arias. “Because organic electronics are flexible, they can easily conform to the body.”

Arias added that because the components of conventional oximeters are relatively expensive, healthcare providers will choose to disinfect them if they become contaminated. In contrast, “organic electronics are cheap enough that they are disposable like a bandaid after use”, she said. The National Science Foundation and Flextech helped support this research.