Engineers from the University of California, Berkley, have created a flexible sensor that maps blood-oxygen levels over large areas of skin, tissue and organs. The team says this sensor has potential to monitor wound healing wounds, oxygen levels in transplanted organs, oxygenation of skin grafts and more.

A new sensor made of an alternating array of printed LEDs and photodetectors can detect blood-oxygen levels anywhere in the body. The sensor shines red and infrared light into the skin and detects the ratio of light that is reflected back. Source: Yasser Khan, Arias Research Group, UC BerkeleyA new sensor made of an alternating array of printed LEDs and photodetectors can detect blood-oxygen levels anywhere in the body. The sensor shines red and infrared light into the skin and detects the ratio of light that is reflected back. Source: Yasser Khan, Arias Research Group, UC Berkeley

"When you hear the word oximeter, the name for blood-oxygen sensors, rigid and bulky finger-clip sensors come into your mind," said Yasser Khan, a graduate student in electrical engineering and computer sciences at UC Berkeley. "We wanted to break away from that, and show oximeters can be lightweight, thin and flexible."

Organic electronics are printed onto a bendable plastic which fits the contours of the patient's body. It also has an array of red and near-infrared organic LEDs and organic photodiodes printed on the surface. The sensor can be placed anywhere on the skin and detect blood-oxygen levels at nine points in a grid.

Ana Claudia Arias, a professor of electrical engineering and computer sciences at UC Berkeley, said, "Patients with diabetes, respiration diseases and even sleep apnea could use a sensor that could be worn anywhere to monitor blood-oxygen levels 24/7."

Current oximeters only work on partially transparent areas of the body, like the earlobe.

"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," Khan said.

In 2014, the team proved that printed LEDs can create thin and flexible oximeters for the fingertips and earlobes. They later developed a means to measure tissue oxygenation using reflected light.

The newest sensor is a combination of these two developments. It tracked overall blood-oxygen levels on the forehead of a volunteer, who then breathed lower concentrations of oxygen. The results matched those of a standard fingertip oximeter. The new sensor also mapped the blood-oxygen levels in a three-by-three grid on the volunteer’s forearm.

"After transplantation, surgeons want to measure that all parts of an organ are getting oxygen," Khan said. "If you have one sensor, you have to move it around to measure oxygenation at different locations. With an array, you can know right away if there is a point that is not healing properly."

The paper on the new sensor was published in the Proceedings of National Academy of Sciences.