Kuang-Chong Wu

Case‐II diffusion in polymers. I. Transient swelling

The swelling of a polymer glass by sorption of a small molecule penetrant is considered in a regime characterized by so‐called case‐II diffusion. Attention is focused on the polymer so that the swelling process can be investigated apart from diffusion. The model of Thomas and Windle (TW) is used to predict the surface swelling as a function of exposure time. This model assumes that the swelling is driven by the osmotic pressure which relaxes to zero as the surface penetrant volume fraction φs approaches its equilibrium value φe. The rate‐controlling factor of the swelling process is the viscosity of the polymer η, which decreases with increasing surface sorption according to η=η0 exp(−mφ) where η0 is the viscosity of the unswollen polymer. For large values of M=mφe, φs is very small until a time τ is reached beyond which the swelling then accelerates rapidly towards its equilibrium value. This feature is absent if M

Etching submicrometer trenches by using the Bosch process and its application to the fabrication of antireflection structures

This paper reports solutions to the issues of profile control, microloading effect and suppression of the sidewall roughness of submicrometer trenches by modifying the regular conditions of the Bosch process that is often employed in the inductively coupled plasma (ICP) deep reactive ion etching (DRIE) system. Additionally, under the modified processing conditions, a high efficient antireflection structure can be fabricated.

Case‐II diffusion in polymers. II. Steady‐state front motion

We consider front formation and steady‐state front motion in a one‐dimensional polymer system undergoing case‐II diffusion. The polymer system approximates a polymer sheet whose thickness is very small compared with its lateral dimensions. The osmotic pressure of Thomas and Windle (TW) is used in the theoretical analysis. The transient problem of front formation is formulated. It is found that the original coupled system of partial differential equations proposed by TW can be reduced to one equation. An exact solution of this equation for a diffusion front moving with a velocity V is presented. The solution allows us to predict the dependence of the steady‐state velocity on material parameters and the equilibrium concentration of penetrant outside the sheet. The concentration and pressure profile ahead of the moving front is obtained. We also show that the TW Model predicts the existence of a Fickian tail ahead of the steadily moving front. Conditions for the dominance of the Fickian tail are determined. ...

Phase-shifting algorithms for electronic speckle pattern interferometry

A set of innovative phase-shifting algorithms developed to facilitate metrology based on electronic speckle pattern interferometry (ESPI) are presented. The theory of a phase-shifting algorithm, called a (5,1) algorithm, that takes five phase-shifted intensity maps before a specimen is deformed and one intensity map after a specimen is deformed is presented first. Because a high-speed camera can be used to record the dynamic image of the specimen, this newly developed algorithm has the potential to retain the phase-shifting capability for ESPI in dynamic measurements. Also shown is an algorithm called a (1,5) algorithm that takes five phase-shifted intensity maps after the specimen is deformed. In addition, a direct-correlation algorithm was integrated with these newly developed (5,1) or (1,5) algorithms to form DC-(5,1) and DC-(1,5) algorithms, which are shown to improve significantly the quality of the phase maps. The theoretical and experimental aspects of these two newly developed techniques, which can extend ESPI to areas such as high-speed dynamic measurements, are examined in detail.

Enhanced luminescence of organic/metal nanostructure for grating coupler active long-range surface plasmonic device

This letter is intended to demonstrate the effect of coupled active long-range surface plasmon polaritons (SPPs) on the plasmonics response of a lamellar grating nanostructure with organic material on the surface. The phenomenon of nano-optics gives rise to a selective spectral response and a local field enhancement. The authors’ fabricated device consists of coupled organic/metal nanostructure with specific width and symmetric dielectric structure. The interaction between organic/metal interface SPPs can allow specific directional emission rather than isotropic emission. The authors present recent experimental results and discuss potential applications of such an active plasmonic biosensor with enhanced resonance energy emission due to interactions on the organic/metal nanograting.

Enhancement and tunability of active plasmonic by multilayer grating coupled emission

The effect of coupled mode surface plasmon polaritons (SPPs) on the active emission of a nanostructure grating with organic semiconductor material, Alq(3), on the surface was investigated in this study. We report surface plasmon grating coupled emission (SPGCE) from excited organic layer on metal grating in both organic/metal (2-Layer) and organic/metal/organic/metal (4-Layer) structures. The dispersion relation was obtained from angle-resolved photoluminescence measurement. The resultant emission intensity can have up to 6 times enhancement on the 4- Layer device and the Full-Width Half-Maximum (FWHM) is less than 50 nm. The combination of SPPs on organic/metal interface allows specific directional emission and color appearance of Alq(3) fluorophores. Potential applications of such an active plasmonics with enhanced resonant energy emission due to interactions on the organic/metal nano-grating as biosensor were presented and discussed.

Near-Tip Fields in a Notched Body With Dislocations and Body Forces

Strohs formualism for anisotropic elasticity is used. The intensity coefficients contained in the near tip fields are determined by bettis reciprocity theorem. Special attention is given to orthotropic and isotropic materials. Some explicitt results of intensity coefficients due to concentrated forces on the notch faces and dislocations at the wedge bisector are also provided

Simulation on binding efficiency of immunoassay for a biosensor with applying electrothermal effect

The working principle of immunoassays is based on the specific binding reaction of an analyte-ligand protein pair in physiological environments. However, for a diffusion-limited protein, the diffusion boundary layer of the analyte on the reaction surface of a biosensor would hinder the binding reaction from association and dissociation. The formation of such association and dissociation layers thus limits the response time and the overall performance of a biosensor. In this work we have performed a two-dimensional full time scale finite element simulation on the binding reaction kinetics of two commonly used proteins, C-reactive protein (CRP) and immunoglobulin G (IgG). By applying a nonuniform ac electric field to the flow microchannel of the biosensor, the electrothermal force can be generated to induce a pair of vortices to stir the flow field. With the aid of the vortices and a suitable choice of the location of the biosensor, the fluids flowing over the reacting surface can be accelerated fast enough...

Representations of Stress Intensity Factors by Path-Independent Integrals

Two types of representation are given. The first type of integrals are expressed by integration over contours surrounding a crack tip. Those of the second type are integrated over contours enclosing a finite crack. The path independent integrals are applied to determine the stress intensity factors due to a body force and a dislocation for a finite crack in an infinite anisotropic body

Dynamic crack growth in anisotropic material

Dynamic propagation of a crack in an anisotropic material under uniform stress is studied. The crack is assumed to nucleate from an infinitesimal micro-crack and expands with a constant velocity. Explicit expressions for the stress intensity factor and the energy release rate are derived.