Yong-Kyu Yoon

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Metals typically have very large nonlinear susceptibilities (~10(6) times larger than those of typical dielectrics), but because they are nearly opaque their nonlinear properties are effectively inaccessible. We demonstrate numerically that a multilayer metal-dielectric structure in which the metal is the dominant nonlinear [chi((3))] material can have much(More)
Conventional micromolding provides rapid and low-cost methods to fabricate polymer microstructures, but has limitations when producing sophisticated designs. To provide more versatile micromolding techniques, we developed methods based on filling micromolds with polymer microparticles, as opposed to polymer melts, to produce microstructures composed of(More)
We present a fabrication approach for the production of micromachined biodegradable microstructures, and illustrate its application in two areas: biodegradable microneedles for transdermal drug delivery, and biodegradable ratcheting surgical ties for blood vessel surgery. We fabricated solid polymer microneedles out of polyglycolide, polylactide and their(More)
We designed electrospun polycaprolactone mats consisting of nanofibers and microbeads for extended delivery of dexamethasone. Thin flexible dexamethasone loaded polycaprolactone mats were prepared by electrospinning. The solvents, polymer loading, voltage and tip-to-collector distance were varied to explore the effects on microstructure of the mats. The(More)
Administration of protein and DNA biotherapeutics is limited by the need for hypodermic injection. Use of micron-scale needles to deliver drugs in a minimally invasive manner provides an attractive alternative, but application of this approach is limited by the need for suitable microneedle designs and fabrication methods. To address this need, this paper(More)
We report a fabrication approach for three-dimensional (3-D) microstructures having functional metal patterns by using inclined UV lithography and 3-D metal transfer micromolding. Inclined rotational UV exposure using SU-8 has been exploited to simultaneously generate gradually varying 3-D structures with different heights in a single mask. For 3-D metal(More)
We have designed and fabricated a microneedle array with electrical functionality with the final goal of electroporating skin's epidermal cells to increase their transfection by DNA vaccines. The microneedle array was made of polymethylmethacrylate (PMMA) by micromolding technology from a polydimethylsiloxane (PDMS) mold, followed by metal deposition,(More)
A multidimensional, vertical screen filter system is developed in which structures analogous to the mesh of a window screen are extended vertically through the cross-sectional area of a simultaneously-formed flow channel. Vertical screens with heights of up to 400 microns and aperture sizes of 10 microns have been achieved in a simple, multiexposure(More)
This article presents a new method for fabricating highly conductive gold nanostructures within a polymeric matrix with subwavelength resolution. The nanostructures are directly written in a gold precursor-doped photoresist using a femtosecond pulsed laser. The laser energy is absorbed by a two-photon dye, which induces simultaneous reduction of gold in the(More)
We report a replica molding process for simultaneously forming a three dimensional metal pattern on the surface of molded polymer microstructures. This technique uses noncovalent surface forces to guide the transfer of thin metal films from the three dimensional features of high aspect ratio poly dimethylsiloxane micromolds to polymeric replicates. The(More)