Researchers at University of California Berkeley have developed a flexible sensor that can be placed on the skin to measure levels of blood oxygenation over a large area. The device could help in tracking wound healing, or in monitoring oxygenation levels in transplanted skin or organs.
“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 researcher involved in the study. “We wanted to break away from that, and show oximeters can be lightweight, thin and flexible.”
In traditional finger-clip oximeters, LEDs shine near-infrared light through the skin. As red, oxygen-loaded blood absorbs more infrared light than deoxygenated blood, the sensor detects how much light makes it through the tissue, which gives an indication of blood oxygenation. However, this means that the sensor can only be applied to relatively thin and transparent appendages, such as the finger or ear lobe.
“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,” said Khan.
Instead of measuring light that is transmitted through tissue, the new sensor measures reflected light. This means that it can be applied anywhere on the body and can measure blood oxygenation at nine points in a grid, providing a more complete picture of local oxygenation.
The new sensor consists of an array of red and near-infrared LEDs printed on a flexible surface. The researchers have tested it on the forehead and forearm of volunteers, and found that it provides blood oxygenation readings that are comparable to a traditional finger-clip oximeter.
“All medical applications that use oxygen monitoring could benefit from a wearable sensor,” said Ana Claudia Arias, another researcher involved in the study. “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.”
“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.”
Study in Proceedings of the National Academy of Sciences: A flexible organic reflectance oximeter array
Via: UC Berkeley