Publications by authors named "Deug-Woo Lee"

Background: Cerebral angiography in a rabbit model is widely used in the field of interventional radiology. Conventionally, the femoral artery is used for cerebral angiography in radiology departments. However, angiographic studies require surgical cutdown of the femoral artery, which is technically difficult.

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  • Pulse electrochemical nanopatterning is a non-contact method for creating nanoscale oxide patterns on silicon surfaces using ultrashort voltage pulses.
  • The process involves localized electrochemical oxidation facilitated by pulsed currents delivered through atomic force microscopy, allowing control over the size of the oxide features.
  • Oxides can be easily removed through chemical etching, which enables a more refined approach for layer-by-layer nanofabrication.
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Optical transparency and mechanical flexibility are both of great importance for significantly expanding the applicability of superhydrophobic surfaces. Such features make it possible for functional surfaces to be applied to various glass-based products with different curvatures. In this work, we report on the simple and potentially cost-effective fabrication of highly flexible and transparent superhydrophobic films based on hierarchical surface design.

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We present a simple route for controlling the surface morphology of polydimethylsiloxane (PDMS) films based on a standard replica molding technique incorporating a microparticle-embedded elastomeric master for enhancing surface wetting properties. The elastomeric masters are simply prepared by embedding microparticles (MPs) firmly into a surface of PDMS substrates using an abrasive air-jetting (AAJ) that can be potentially scaled up to large-area fabrication. The surface geometries of the PDMS masters can be easily controlled by using MPs with different shape and size in the AAJ process, resulting in easy control of the surface morphologies and resultant wetting and optical properties of the PDMS films after replicating.

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A facile and scalable technique to fabricate optically transparent, mechanically flexible and self-cleanable superhydrophobic films for practical solar cell applications is proposed. The superhydrophobic films were fabricated simply by transferring a transparent porous alumina layer, which was prepared using an anodic aluminium oxidation (AAO) technique, onto a polyethylene terephthalate (PET) film with a UV-curable polymer adhesive layer, followed by the subsequent formation of alumina nano pyramids (NPs) through the time-controlled chemical etching of the transferred porous alumina membrane (PAM). It was found experimentally that the proposed functional films can ensure the superhydrophobicity in the Cassie-Baxter wetting mode with superior water-repellent properties through a series of experimental observations including static contact angle (SCA), contact angle hysteresis (CAH), sliding behaviour on the tilted film, and dynamic behaviour of the liquid droplet impacting on the film.

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We demonstrated that the size and morphology of an oxidizer have strong effects on the propulsion forces of nano-Al-based propellants. Enhanced propulsion forces could be obtained through the creation and addition of various oxidizer nanoparticles and nanowires in nano-Al-based propellants.

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TiO2 nanoparticles (NPs) with a size of 240 nm (T240), used as a light-scattering layer, were applied on 25-nm-sized TiO2 NPs (T25) that were used as a dye-absorbing layer in the photoelectrodes of dye-sensitized solar cells (DSSCs). In addition, the incident light was concentrated via a condenser lens, and the effect of light concentration on the capacity of the light-scattering layer was systematically investigated. At the optimized focal length of the condenser lens, T25/T240 double layer (DL)-based DSSCs with the photoactive area of 0.

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Dye-sensitized solar cells (DSSCs) are inexpensive to manufacture and easy to process in comparison with silicone solar cells, but they are difficult to commercialize due to their low efficiency. Accordingly, the aim of this study was to improve the efficiency of a DSSC via an aluminum film reflective plate, reusing discarded light after it was absorbed. We found that the factor having the most dominant influence on DSSC efficiency was the amount of radiation reacting with the dye.

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Dye-sensitized solar cells (DSSCs) are inexpensive to manufacture and easy to process in comparison with silicone solar cells, but they are difficult to commercialize due to their low efficiency. Accordingly, the aim of this study was to improve the efficiency of a DSSC via an aluminum film reflective plate, reusing discarded light after it was absorbed. We found that the factor having the most dominant influence on DSSC efficiency was the amount of radiation reacting with the dye.

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Dye-sensitized solar cells have slightly lower photoelectric efficiency than silicon solar cells. Researchers have investigated various ways to address this problem. In this paper, we found that the optimized separation between the condenser lens and the cells was 8 mm.

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Dye-sensitized solar cells have slightly lower photoelectric efficiency than silicon solar cells. Researchers have investigated various ways to address this problem. This study improved the efficiency of a dye-sensitized solar cell by re-driving it with a reflector, reusing discarded light after it was absorbed.

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In this study, brittle materials were mechanically modified under precise normal force control at the mN approximately microN level using PCD tools as a nano tool. The lab-made PCD attached micro cantilevers were customized for tribo nanolithography. The machined patterns were measured under an atomic force microscope (AFM) to obtain the machining characteristics of the samples for each set of conditions.

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In this study, we propose one of the ultra-precision machining methods that can be adapted brittle material as well as soft material by using multi arrayed diamond tips and high speed spindle. Conventional machining method is too hard to control surface roughness and surface texture against brittle material because particles of grinding tools are irregular size and material can be fragile. Therefore we were able to design tool paths and machine controlled pattern on surface by multi arrayed diamond tips which has uniform size made in MEMS fabrication and high speed spindle of which maximum speed is about 300,000 rpm.

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Article Synopsis
  • Piezoelectric actuators are beneficial for ultra-precision applications due to their high force, resolution, and speed, but have limited positioning ranges which restrict their use for long-distance tasks.
  • A new variable speed inchworm stage design features hinge structures that enhance displacement through a lever mechanism, allowing for nanometer resolution while addressing the limitations of traditional piezoelectric actuators.
  • The study revealed that lever ratio affects stiffness, and materials like aluminum provided better responsiveness and performance compared to stainless steel, highlighting the importance of material choice in actuator design.
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This paper demonstrates a micro/nanoscale surface patterning technology for brittle material using mechanical and chemical processes. Fused silica was scratched with a Berkovich tip under various normal loads from several mN to several tens of mN with various tip rotations. The scratched substrate was then chemically etched in hydrofluoric solution to evaluate the chemical properties of the different deformed layers produced under various mechanical scratching conditions.

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  • Nano-stages are critical components in ultra-precision systems like scanning probe microscopes and optical fiber aligners, utilizing nano-scale motion for high accuracy.
  • The performance of these motion stages is influenced by several factors, including hinge structure, actuation methods, and system control strategies.
  • This paper presents advancements in leafspring and planar joint hinges, proposing a new composite joint hinge stage to enhance overall system performance.
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