Development of the microLED based flexible optoelectronic devices for the biomedical implants

Abstract

Light emitting-diode (LED) has been used for the light mediated biomedical treatments including the optogenetics and the phtotherapy. However, the conventional LEDs such as the inorganic LED, and the OLED have limitations to be applied for the high-resolution diagnostics, and the stable phototherapy of the curve organs and skins due to their low flexibility and efficiency, large emitting area, performance degradation by the moisture and the oxygen. To solve these problems, the micro-LED, promising candidate to replace the traditional display materials, has been employed as the optoelectronic devices for the biomedical treatments. However, the micro-LED has difficulties in the packaging process due to the absence of the reliable transfer technology. In this work, flexible vertical micro-LED (f-VLED) was developed through the ACF transfer technology in high production yield. AlGaInP f-VLEDs exhibited the optical power of $50 \mu W$ at 1 mA, peak wavelength of 639.68 nm, and stable pulsed operation. Then, the f-VLEDs were implanted under the mouse skull to stimulate the frontal motor cortex, and successfully induced the forlimb movement of the mouse through the optogenetics. GaN f-VLED preserved its overall performance regardless of the 3,000 bending cycles at the bending radius of 2 cm. The f-VLEDs were fabricated as $10 \times 10$ array passive matrix display, and showed stable operation, demonstrating the applicability of the f-VLEDs to the phototherapy of the large sized organs and skins.