Researchers from Harvard University have developed a paint-on, see-through, smart bandage that glows to indicate tissue oxygenation concentration. The smart bandage provides direct, noninvasive measurement of tissue oxygenation by combining a bright sensor molecule with a long phosphorescence lifetime and appropriate dynamic range; a bandage material compatible with the sensor molecule that conforms to the skin’s surface to form an airtight seal; and an imaging device capable of capturing the oxygen-dependent signals from the bandage with high signal-to-noise ratio. The bandage glow is generated by phosphors, molecules that absorb light and then emit it via a process known as phosphorescence. As the concentration of oxygen is reduced, the phosphors glow longer and more bright. To make the bandage simple to interpret, the researchers incorporated a green oxygen-insensitive reference dye. Changes in tissue oxygenation are displayed as a green-to-red color map. The bandage is applied onto the skin’s surface as a viscous liquid, which dries to a solid thin film within a minute. Once the first layer has dried, a transparent barrier layer is then applied atop it to protect the film and slow the rate of oxygen exchange between the bandage and room air, making the bandage sensitive to the oxygen within tissue. A camera or smartphone is used with the bandage to provide a burst of excitation light that triggers the emission of the phosphors inside the bandage, and then it records the phosphors’ emission.