A low-cost production technology for thin-film blue flexible vertical micro LEDs (f-VLEDs) could help advance the commercialization of micro LEDs in flexible displays and for bilateral visual communication in the Internet of Things. A research team at the Korea Advanced Institute of Science and Technology (KAIST) has developed a source technology that enables production of thousands of thin-film blue vertical micro LEDs, each less than 2 μm thick, on plastics, using a one-time transfer. The team demonstrated high-performance GaN f-VLEDs using silver nanowire networks and monolithic fabrication. High-performance and high-density blue f-VLED arrays. Courtesy of KAIST. The blue GaN f-VLEDs achieved an optical power density of about 30 mW/mm2 — three times higher than that of lateral micro LEDs. By reducing heat generation, researchers realized a device lifetime of 100,000 hours. Good thermal and mechanical stability was demonstrated through 100,000 bending-unbending cycles. Researchers inserted the high-density GaN f-VLED arrays onto a living mouse cortex and operated the f-VLED arrays without significant histological damage to the brain. Transparent, ultrathin GaN LED arrays adhered to a human fingernail and stably glowed without mechanical deformation. The team believes that these blue f-VLEDs could be conformally attached to curved skin and brains for wearable devices, and stably operated by wirelessly transferred electrical energy. To widely commercialize micro LEDs for mobile and TV displays, a one-time transfer method for hundreds of thousands of highly efficient thin-film micro LEDs will be required, said the team. “For future micro LEDs, the innovative technology of thin-film transfer, efficient devices, and interconnection is necessary,” said professor Keon Jae Lee at KAIST. “We plan to demonstrate a full-color micro LED display in smartwatch sizes by the end of this year.” Micro LEDs (µLEDs), a sub-100-µm light source for red, green, and blue light, have good optical output, ultralow power consumption, and fast response speed, and they are flexible, making them potential candidates for replacing active matrix OLED (AMOLED) displays. The research was published in Advanced Materials (doi:10.1002/adma.201800649).