Flexible and implantable μLED-based photonic healthcare devices for human body interfaces applications

Abstract

Optical devices including laser and LEDs have been utilized in modern medicine fields as diagnostic and therapeutic tools for treatment of human diseases and disorders. However, conventional light sources cannot achieve efficient light deliver due to mechanical incompliance, heat generation, and high tissue damages, having a restriction in treatment time, targeting area and treatment effectiveness. To implement human body interfaces photonic healthcare devices should be designed in consideration of the shape of human body such as skin, tissues, organs, and brain. In this thesis we developed µLED-based flexible/implantable optoelectronics which can be applied to human skin, pancreas, and heart for treatment of skin diseases, cancer, and arrhythmia, respectively, with minimal tissue damages. In chapter 2, we report a wearable surface-lighting µLED (SµLED) photostimulator for skin-bleaching applications. The SµLEDs, consisting of LDL, 900 thin film µLEDs and PDMS, achieved uniform surface-lighting in 2 × 2 cm$^2$-sized area with 100 % emission yields. The SµLEDs maximize photostimulation effectiveness on the skin surface by uniform irradiation, high flexibility and thermal stability. The SµLEDs effect on melanogenesis inhibition was evaluated via in vitro and in vivo experiments. The anti-melanogenic effect of SµLEDs was confirmed by reduced melanin content and enhanced melanin distribution, compared to a conventional LED (CLED) stimulator. In chapter 3, we demonstrated a deep-implantable, self-fixing, three-dimensional micro-LEDs (SFLEDs) capable of capturing tumor tissues in intra-body environment. The ~15 µm-thick ultra-thin SFLEDs consists of 70 micro-LEDs, a shape memory polymer of polyurethane (PU) and ultra-violet (UV) cured polymers for passivation. The claw-shaped SFLEDs three-dimensionally covered the tumors, while holding the cancer tissues by itself with the characteristics of shape memory polymer. The SFLEDs enabled precise PDT without delamination or movements from the tumor tissues, inducing selective apoptosis/necrosis of tumors in pancreas.