Seung S. Lee

In this letter, a focal tunable liquid lens using a large deformable polydimethylsiloxane (PDMS) membrane is integrated with an electromagnetic microactuator for uniform pressure on the membrane by a fabrication process of PDMS compatible with conventional micromachining processes. The fabricated device is characterized by surface profiling and optical observations. A rectangular PDMS membrane of 3mm in width for actuation shows that the maximum displacement is 51.4μm when the current is 30mA. I

A micromachined piezoelectric cantilever transducer, which works both as a microphone and as a microspeaker, has been fabricated and tested. The 2000/spl times/2000/spl times/4.5 /spl mu/m/sup 3/ cantilever has a zinc oxide (ZnO) piezoelectric thin film on a supporting layer of low-pressure chemical-vapor-deposited (LPCVD) low-stress silicon nitride. A highlight of the fabrication process, which may also be relevant for other micromachined structures, is the technique for producing a flat, multi

In this paper we propose a new split and recombination (SAR) micromixer that is compatible with the microfabrication process of polydimethylsiloxane ( PDMS). We evaluate the mixing efficiency of the fabricated SAR micromixer and find that it increases interfaces exponentially. Simulation using CFD-ACE+ shows a cross-sectional view of the flow and estimates the mixing efficiency of the SAR micromixer and the pressure drop for a unit of the SAR micromixer. A mixing experiment involving phenolphtha

The present work describes a theoretical investigation of the near-field thermal radiation between doped Si plates coated with a mono-layer of graphene. It is found that the radiative heat flux between doped Si plates can be either enhanced or suppressed by introducing graphene layer, depending on the Si doping concentration and chemical potential of graphene. Graphene can enhance the heat flux if it matches resonance frequencies of surface plasmon at vacuum-source and vacuum-receiver interfaces

We introduce a facile method to enhance the functionality of a patterned metallic transparent conductor through selective laser ablation of metal nanowire percolation network. By scanning focused nanosecond pulsed laser on silver nanowire percolation network, silver nanowires are selectively ablated and patterned without using any conventional chemical etching or photolithography steps. Various arbitrary patterns of silver nanowire transparent conductors are readily created on the percolation ne

The present work theoretically analyzes the performance of the near-field thermophotovoltaic (TPV) energy conversion device for low temperature applications (Tsource ∼ 500 K). In the proposed TPV system, doped Si is employed as the source because its optical property can be readily tuned by changing the doping concentration, and InSb is selected as a TPV cell because of its low bandgap energy (0.17 eV). In order to enhance the near-field thermal radiation between the source and the TPV cell, mon

We investigated a novel fabrication method of a microneedle array. In microneedle fabrication methods employed to date, researchers have used conventional silicon-based fabrication methods such as inductively coupled plasma etching and wet etching techniques. However, these processes are not sufficient for the fabrication of a longer needle shank and applications such as blood extraction from the skin surface. Using a deep x-ray, high-aspect-ratio (HAR) 3D microstructures can be fabricated. The

Artificially designed hyperbolic metamaterial (HMM) possesses extraordinary electromagnetic features different from those of naturally existing materials. In particular, the dispersion relation of waves existing inside the HMM is hyperbolic rather than elliptical; thus, waves that are evanescent in isotropic media become propagating in the HMM. This characteristic of HMMs opens a novel way to spectrally control the near-field thermal radiation in which evanescent waves in the vacuum gap play a c

Flower-like CuO nanostructures were fabricated to enhance nucleate pool boiling. These nanostructures enhance boiling due to capillary wicking induced by their high surface area–to-volume ratio. Despite only having a thickness of 3–4 μm, ∼58% improvement in critical heat flux (CHF) was obtained by the addition of CuO nanostructures to both a smooth surface and a microgrooved surface. Because the CuO nanostructures are processed at room temperature, they can be easily combined with microfabricate