Engineering topics
Koo, Hyung-Jun
Publications and source records attributed to Koo, Hyung-Jun.
Flexible and Wearable Fiber Microsupercapacitors Based on Carbon Nanotube–Agarose Gel Composite Electrodes
Not provided.
Selective Wetting-Induced Micro-Electrode Patterning for Flexible Micro-Supercapacitors
Selective wetting-induced micro-electrode patterning is used to fabricate flexible micro-supercapacitors (mSCs). Here, the resulting mSCs exhibit high performance, mechanical stability, stable cycle life, and hold great promise for facile integration into flexible devices requiring on-chip energy storage.
Facile fabrication of graphene composite microwires via drying-induced size reduction of hydrogel filaments
Graphene based electrical conductors are under consideration for numerous applications in energy storage, energy conversion devices, electronics and sensors. Here, we report a facile and versatile method for fabrication of graphene based composite microwires ranging from ~20 to 250 μm in diameter via size reduction during dehydration of extruded larger diameter graphene oxide-loaded agarose hydrogel fibers. The graphene oxide is effectively reduced to graphene by chemical and thermal treatment. Here, after dehydration and reduction, the resulting graphene composite microwires exhibit high electrical conductivities of up to 1.8 S m –1 .
Regenerable Photovoltaic Devices with a Hydrogel-Embedded Microvascular Network
Light-driven degradation of photoactive molecules could be one of the major obstacles to stable long term operation of organic dye-based solar light harvesting devices. One solution to this problem may be mimicking the regeneration functionality of a plant leaf. We report an organic dye photovoltaic system that has been endowed with such microfluidic regeneration functionality. A hydrogel medium with embedded channels allows rapid and uniform supply of photoactive reagents by a convection-diffusion mechanism. A washing-activation cycle enables reliable replacement of the organic component in a dye-sensitized photovoltaic system. Repetitive restoration of photovoltaic performance after intensive device degradation is demonstrated.