US engineers have developed a new lightweight, thin and flexible sensor that can map blood-oxygen levels over large areas of skin, tissue, and organs, potentially giving doctors a new way to monitor healing wounds in real time.


Injuries cannot heal without a constant influx of blood's key ingredient -- oxygen. The device can track oxygenation of healing wounds in real time. The sensor is made of organic electronics printed on bendable plastic that moulds to the contours of the body and can be placed anywhere on the skin. 

It could potentially be used to map oxygenation of skin grafts, or to look through the skin to monitor oxygen levels in transplanted organs, the researchers said. "All medical applications that use oxygen monitoring could benefit from a wearable sensor," said Ana Claudia Arias, Professor at the University of California (UC)- Berkeley. 

"Patients with diabetes, respiration diseases and even sleep apnoea could use a sensor that could be worn anywhere to monitor blood-oxygen levels 24/7," she added. Existing oximeters (the name for blood-oxygen sensors) use LEDs to shine red and near-infrared light through the skin, and work only on areas of the body that are partially transparent, like the fingertips or the earlobes. It can only measure blood-oxygen levels at a single point in the body.

"Thick regions of the body, such as the forehead, arms and legs, barely pass visible or near-infrared light, which makes measuring oxygenation at these locations really challenging," the researchers said. The new sensor, described in the journal PNAS, is built of an array of alternating red and near-infrared organic LEDs and organic photodiodes printed on a flexible material. 

The team used the sensor to track the overall blood-oxygen levels on the forehead of a volunteer who breathed air with progressively lower concentrations of oxygen -- similar to going up in altitude -- and found that it matched those using a standard fingertip oximeter. They also used the sensor to map blood-oxygen levels in a three-by-three grid on the forearm of a volunteer wearing a pressure cuff.