Seung-Dae Oh

We present a method of helical long-period fiber grating (H-LPFG) fabrication by use of a CO2 laser for use as an optical torque sensor. A conventional optical fiber grating has periodic vertical index changes along its fiber axis, but a H-LPFG has a screw-type index modulation. The helical index modulation is obtained with the asymmetric index change caused by a single-side laser beam exposure. The H-LPFG shows peak shifts with codirectional or contradirectional torsion to the helix. Also, the

The lotus effect indicates that a superhydrophobic, self-cleaning surface can be obtained by roughening the topography of a hydrophobic surface. However, attaining high transmittance and clarity through a roughened surface remains challenging because of its strong scattering characteristics. Here, a haze-free, antireflective superhydrophobic surface that consists of hierarchically designed nanoparticles is demonstrated. Close-packed, deep-subwavelength-scale colloidal silica nanoparticles and th

A membrane with selective wettability to either oil or water has been utilized for highly efficient, environmentally friendly membrane-based oil-water separation. However, a predictive model, which can be used to evaluate the overall separation performance of the membrane, still needs further development. Herein, we investigate three separation performance parameters, that is, separation efficiency, liquid intrusion pressure, and mass flux in particular, as a function of pore geometry and liquid

We introduce a thin (<200 nm) superhydrophobic cerium-oxide surface formed by a one-step wet chemical process to enhance the condensation heat-transfer performance with improved thermal stability compared to silane-treated surfaces. The developed cerium-oxide surface showed a superhydrophobic characteristic with a low (<5°) contact angle hysteresis because of the unique surface morphology and hydrophobicity of cerium oxide. The surface was successfully incorporated to popular engineering materia

The sluggish and complex multi-step oxygen evolution reaction remains an obstacle to bias-free photoelectrochemical water-splitting systems. Several theoretical studies have suggested that spin-aligned intermediate radicals can significantly enhance the kinetic rates for oxygen generation. Herein, it is reported that the chirality-induced spin selectivity phenomena can become an impressive approach by adopting chiral 2D organic-inorganic hybrid perovskites as a spin-filtering layer on the photoa

Here, we study the water penetration dynamics through a Janus membrane with opposite wettability, i.e., (super-) hydrophobic on one side and (super-) hydrophilic on the other side, during drop impact. It is demonstrated that the penetration dynamics through the membrane consists of two temporally distinct events: dynamic pressure driven penetration dynamics on a shorter timescale and capillary pressure driven penetration dynamics on a longer timescale. For penetration under dynamic pressure, the

We experimentally confirmed the idea of mitigating (or delaying) the cavitation on the turbomachinery (rotating blades) by transforming the blade surface to be superhydrophilic, thereby the population of the cavitation nuclei is reduced near the surface. We focused on the changes in the cavitation incidence rate, amount of cavitation bubble, and bubble distribution on the superhydrophilic blade through the high-speed camera imaging, compared to the case with a regular (i.e., smooth) surface. Wit