The organic light-emitting diode (OLED) technology behind flexible cell phones, curved monitors, and televisions could one day be used to make on-skin sensors that show changes in temperature, blood flow, and pressure in real time. An international collaboration, led by researchers from Seoul National University in the Republic of Korea and Drexel University, has developed a flexible and stretchable OLED that could put the technology on track for this use and a range of new applications.