Ryung Shin

Controlled electrochemical growth of Co(OH)2 flakes on 3D multilayered graphene foam for high performance supercapacitors

The present research describes successful enchase of Co(OH)2 microflakes by the potentiodynamic mode of electro-deposition (PED) on porous, light weight, conducting 3D multilayered graphene foam (MGF) and their synergistic effect on improving the supercapacitive performance. Structural and morphological analyses reveal uniform growth of Co(OH)2 microflakes with an average flake width of ∼30 nm on the MGF surface. Moreover, electrochemical capacitive measurements of the Co(OH)2/MGF electrode exhibit a high specific capacitance of ∼1030 F g−1 with ∼37 W h kg−1 energy and ∼18 kW kg−1 power density at 9.09 A g−1 current density. The superior pseudoelectrochemical properties of cobalt hydroxide are synergistically decorated with high surface area offered by a conducting, porous 3D graphene framework, which stimulates the effective utilization of redox characteristics and mutually improves electrochemical capacitive performance with charge transport and storage. This work evokes scalable electrochemical synthesis with the enhanced supercapacitive performance of the Co(OH)2/MGF electrode in energy storage devices.

Design methodology for a confocal imaging system using an objective microlens array with an increased working distance.

In this study, a design methodology for a multi-optical probe confocal imaging system was developed. To develop an imaging system that has the required resolving power and imaging area, this study focused on a design methodology to create a scalable and easy-to-implement confocal imaging system. This system overcomes the limitations of the optical complexities of conventional multi-optical probe confocal imaging systems and the short working distance using a micro-objective lens module composed of two microlens arrays and a telecentric relay optical system. The micro-objective lens module was fabricated on a glass substrate using backside alignment photolithography and thermal reflow processes. To test the feasibility of the developed methodology, an optical system with a resolution of 1 μm/pixel using multi-optical probes with an array size of 10 × 10 was designed and constructed. The developed system provides a 1 mm × 1 mm field of view and a sample scanning range of 100 μm. The optical resolution was evaluated by conducting sample tests using a knife-edge detecting method. The measured lateral resolution of the system was 0.98 μm.

Effects of Fabrication Errors on the Sensitivity of Nano-Replicated Guided Mode Resonance Protein Sensors

Although an injection molding is a promising method for inexpensive mass production of nanograting substrate for disposable guided mode resonance (GMR) protein sensor, the incomplete filling of nanocavities due to the thick solidified layer in conventional injection molding process may lower the sensitivity of label-free GMR protein sensor. In this study, an instant heating method at the filling stage during the injection molding process was investigated to improve the pattern transcribability of molded nanograting and the sensitivity of fabricated GMR protein sensor. Two types of injection molded nanograting with and without instant heating method were prepared and the effects of pattern fidelity on the performance of fabricated GMR protein sensor were analyzed by theoretical and experimental methods.

Label-free detection of protein-protein interactions on multi-scale micro-well arrays using spatial light modulator

A mass production method of label-free protein microarray integrated with micro-well structures for the use of miniaturized multi-parallel scanning system was investigated. The geometrical parameters of biosensing structure were designed by rigorous coupled wave analysis simulation, and micro-well structures were designed considering the detection and material delivery system. The protein microarray with micro-well structures was fabricated by one-step UV nanoimprinting process using an electroformed multi-scale metallic stamp. Finally, microarray scanning was achieved using optical modulation without applying any motorized system and the feasibility of proposed protein microarray and scanning system was demonstrated by verifying the bio-molecular interactions.

Acoustically sticky topographic metasurfaces for underwater sound absorption

A class of metasurfaces for underwater sound absorption, based on a design principle that maximizes thermoviscous loss, is presented. When a sound meets a solid surface, it leaves a footprint in the form of thermoviscous boundary layers in which energy loss takes place. Considered to be a nuisance, this acoustic to vorticity/entropy mode conversion and the subsequent loss are often ignored in the existing designs of acoustic metamaterials and metasurfaces. The metasurface created is made of a series of topographic meta-atoms, i.e., intaglios and reliefs engraved directly on the solid object to be concealed. The metasurface is acoustically sticky in that it rather facilitates the conversion of the incident sound to vorticity and entropy modes, hence the thermoviscous loss, leading to the desired anechoic property. A prototype metasurface machined on a brass object is tested for its anechoicity, and shows a multitude of absorption peaks as large as unity in the 2-5 MHz range. Computations also indicate that a topographic metasurface is robust to hydrostatic pressure variation, a quality much sought-after in underwater applications.

Formation of multilayered magnetic nanotracks with perpendicular anisotropy via deoxidization using ion irradiation on ultraviolet-imprinted intaglio nanostructures

We proposed a method to fabricate perpendicular magnetic nanotracks in the cobalt oxide/palladium multilayer films using UV-nanoimprinting lithography and low-energy hydrogen-ion irradiation. This is a method to magnetize UV-imprinted intaglio nanotracks via low-energy hydrogen ion irradiation, resulting the irradiated region are magnetically separated from the non-irradiated region. Multilayered magnetic nanotracks with a line width of 140 nm, which were fabricated by this parallel process without additional dry etching process, exhibited a saturation magnetization of 290 emu cm−3 and a coercivity of 2 kOe. This study demonstrates a cost-effective mass production of multilayered perpendicular magnetic nanotracks and offers the possibility to achieve high density storage and memory devices.