Since biometric sensing using light can noninvasively measure biological information from the outside of the body, various information can be obtained from dynamic things such as blood oxygen concentration and heart rate to static things such as fingerprints and veins. Among them, a flexible organic imager can be attracted to the body, so it is used as wearable electronics. Utilizing its flexibility, imagers capable of imaging fingerprints and veins, pulses that can be directly applied to the skin, blood oximeters, muscle contraction sensors, etc. have been reported.

In this study, we have developed ultra-flexible and lightweight highly efficient, ultra-flexible, air-stable, three-color, polymer light-emitting diodes (PLEDs) The total thickness of the devices, including the substrate and encapsulation layer, is only three micrometers, which is one order of magnitude thinner than the epidermal layer of the human skin. Due to the very thin substrate and neutral position, our device shows the highly flexibility and conformability. The PLEDs are directly laminated on the surface of skin and are used as indicators/displays. And also, we have developed a sheet-type image sensor that enables high-resolution and high-speed reading. Our conformable imager has pixel pitches as small as 50 µm, with resolutions of up to 508 dpi. Using our conformable imager, we succeed to take a high-resolution image of fingerprints and veins used for biometric authentication.