A new sensor made of an alternating array of printed light-emitting diodes 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. Credit: Yasser Khan, Arias Research Group, UC Berkeley
A new, wearable sensor is able to map out blood-oxygen levels from virtually anywhere on the body.
A University of California Berkeley research team has created a flexible sensor comprised of organic electronics printed on bendable plastic that molds to the contours of the body. The new sensors could be used to map the oxygenation of skin grafts, look through the skin to monitor oxygen levels in transplanted organs, or to give physicians a new way to monitor how wounds are healing.
“All medical applications that use oxygen monitoring could benefit from a wearable sensor,” Ana Claudia Arias, a professor of electrical engineering and computer sciences at UC Berkeley, said in a statement. “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.”
Currently, oximeters only work on areas of the body like the fingertips or earlobes that are partially transparent. They also only measure blood-oxygen levels at a single point in the body, while the new sensor works on nine different points in a grid.
“When you hear the word oximeter, the name for blood-oxygen sensors, rigid and bulky finger-clip sensors come into your mind,” Yasser Khan, a graduate student in electrical engineering and computer sciences at UC Berkeley, said in a statement. “We wanted to break away from that, and show oximeters can be lightweight, thin and flexible.”
These devices use light-emitting diodes (LED) to shine red and near-infrared light through the skin. They then detect how much light makes it to the other side.
Red, oxygen rich blood absorbs infrared light, while darker, oxygen-poor blood absorbs more red light. The ratio of transmitted light determine how much oxygen is in the blood.
The researchers previously printed organic LEDs in 2014 that can be used to develop thin, flexible oximeters for the fingertips or earlobes. They have also developed a way to measure oxygenation in tissues by using reflected light rather than transmitted light.
By combining both breakthroughs, the researchers created the wearable sensor, which is built of an array of alternating red and near-infrared organic LEDS and organic photodiodes printed on a flexible material.
In testing the sensor, the researchers were able to track the overall blood-oxygen levels on the forehead of a volunteer who breathed air with progressively lower concentrations of oxygen. The researchers found that the sensor matched with the data found using a standard fingertip oximeter.
The team 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.
“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 study was published in the Proceedings of the National Academy of Science of the United States of America.
