Advanced Materials Research Vol. 74

Abstract: High dielectric capacitors , that has around 1000 in dielectric constant, can be successfully formed by nanotransfer on non-heat-resisting substrates. PZT film could be released from the Si substrate and bonded onto the polymer one. The releasing characteristics have the relationships with the thickness of Pt layer. The formed PZT has perovskite structure and clear columnar texture.

Abstract: In the broadband communication network, the wavelength-division-multiplexed (WDM) system is widely used to maximize the information that the signals can carry. As a result, the number of channels which are carried by different optical wavelengths in the WDM optical fiber network also keeps increasing. To separate the huge number of different wavelength signals, optical filter is required. The optical filter based on semiconductor has been widely studied due to the maturation of semiconductor fabrication technology and that it is possible to integrate the filter with the stable semiconductor devices such as laser diodes and MOSFETS. The tunable optical filter is basically a selective optical resonator that only allows the resonant modes passing through. Various mechanical methods are studied to achieve the tunable effect by tuning the physical structure of the filter; however, there is not much research on how the semiconductor material will affect the tuning function. In this paper, the author studied the influence of refractive index of the multi-silicon-slabs on the filter, whereby the tuning of refractive index is reached by thermal effect. It is found by simulation that when heating the silicon slabs, the increasing refractive index of silicon will lead to a shift of the resonant mode wavelength. This shift is almost linear with the change of the temperature, which is about 1nm with every 20K temperature increase. For certain devices, the result of the simulation showed it is possible to tune the resonant mode from C band to L band in the Fiber Optical Communication.

Abstract: A packaging architecture is developed for MEMS tunable laser (MEMS-TL). The hybrid integration of chips is realized under high accuracy thermal control and precise alignment. The thermal conductivity of the laser chip has been improved up to 60% by the proper substrate design of device and epi-down bonding method. Under the analysis of heat flux, we employ a thermo-electric cooler (TEC) to stabilize the temperature. The substrate is designed to accommodate gain chips with minimal active optical alignment, thus reducing the packaging cost. With this packaging scheme, the insertion loss is greatly induced less than 1 dB due to the advantages of horizontal and vertical alignment in optical fiber fastening and laser diode bonding.

Abstract: The dependence of the optical properties of spherical gold nanoparticles (AuNPs) on particle size and wavelength were analyzed theoretically using Mie theory, where the complex refractive index of gold was corrected for the effect of a reduced mean free path of the conduction electrons in small particles. The simulation results indicated that larger diameter AuNPs have high sensitivity and the resolution compared to the small diameter AuNPs. Two different fabricated methods for synthesis larger diameter AuNPs have been proposed. One is the directly synthesis 50nm AuNPs, the other method is separated to two steps (prepared 13nm AuNPs seeds, then synthesis 50nm AuNPs). Comparing the UV-vis spectra and SEM image of the AuNPs synthesized by these two method, we find that the symmetry of the directly synthesis method is better than the other method. The experiment results show that the synthesis AuNPs are uniform. The major aim of this work is to provide a simple and fast method to synthesis larger diameter AuNPs and research the optical properties of the nanoparticles.

Abstract: Optimization of micro-mixing components is vital for efficient micro-electromechanical systems (MEMS) and lab-on-a-chips. In this area, it is ideal to have a universal micro-mixer design for general purpose multiple-phase fluidic mixing. Numerical methods to compute and analyze the mixing process in the spiral micro-mixer design are presented. This spiral design has also been found to be efficient for intra-droplet mixing as well as continuous particle separation by utilizing its attributing Dean flows. Analysis on the mixing performance of this design serves to present Archimedes’ spiral as a robust solution and exemplifies the effects of minute yet effective alterations to the design.

Abstract: Efficient energy interconversion between light propagation and the localized field of light is important for highly-sensitive biological and chemical detectors. Solid optical tip can effectively enhance optical intensity for the measurement of nanoscale single molecule imaging. However, it lacks dynamic control mechanisms and is difficult to realize a smooth interface which may result in serious loss of scattering. Liquid can be dynamically controlled and the interfaces are optically smooth. Recently, liquid waveguides are reported to exhibit various advantages of dynamic, cheap and low optical loss. In this paper, a liquid optical tip in a microchannel controlled by flow rates is reported. In the design of the optofluidic chip, the core flow stream of the liquid waveguide is formed as Calcium Chloride (CaCl2) flow stream, and the cladding flow stream is formed as dioionzed (DI) water flow stream. The diffusion of CaCl2 between the microfluidic laminar flows establishes a gradient refractive index distribution to make an optical tip. For the optical system, laser source with central wavelength of 633 nm is used as input. The microchannel has a height of 80 µm and a width of 100 µm. The diffusion coefficient is 1 × 10-9 m2/s. The original refractive index of CaCl2 solution and deinized (DI) water are 1.442 and 1.332, respectively. The optical intensity at the optical tip is increased by 15 times sing Finite-Difference Time-Domain (FDTD) method. Thus, light be guided to form a sharp optical tip through the control of liquid. The on-chip optical tip has potential applications in biological, chemical and medical solution detectors.

Abstract: The microcantilevers have emerged as a versatile biosensor, and showed excellent performance such as high sensitivity, high selectivity, and label-free detection. They have been successfully used for the detection of nucleic acids, disease marker proteins, cells, and pathogens including small molecules. So far, our group has successfully demonstrated the marker protein detection using the actuating layer (PZT)-embedded microcantilevers for the last decade. Here, we introduce in/ex-situ monitoring of the DNA binding events using performance improved actuating layer-embedded microcantilever sensors. To obtain the stable and reliable resonant frequency shifts, the microcantilevers were passivated with parylene-C film for in-situ detection and perfluorosilane (PF-Si) film for ex-situ detection. To achieve the recognition layer, the probe DNA (37-mer including T10 spacers) specific to HBV DNA was immobilized on the gold-coated microcantilever, and followed by backfilling of ethylene glycol spacer (HSC11-EG3-OH) to increase the DNA binding efficiency. After the surface treatment, the detection of HBV DNA (27-mer) was performed through two manners, in-situ and ex-situ. Target DNA in the range of 1 to 20 M and 10 nM to 5 M were applied for the in-situ and ex-situ detection respectively, and the resonant frequency shifts according to the concentration was examined quantitatively. From the results, we explained the relationship between the DNA hybridization and the nanomechanical response. In addition, we presented a hypothesis on the different tendency of in-situ and ex-situ results.

Abstract: Research on microneedles has been increasing rapidly as to overcome the drawbacks of conventional needle which can results in painful during injection, tissue damage and skin infection at the injected site. This paper presents characterization process of wet isotropic etch for solid microneedles array development. This approach utilizes HNA etchant to build the outer shape of solid microneedles. Works has been carried out to investigate the isotropic etching behavior of HNA in different temperature ranging from 20 to 50 degrees, various agitation rate ranging from 0 rpm to 450 rpm and on the various window size ranging from 100 μm to 500 μm. Characterization on those factor, determine the effect of vertical and lateral etch rate variations, surface quality and the geometry obtained. The experimental responses of vertical etch rate, lateral etch rate and high aspect ratio reported. The obtained etching properties will be applied to develop recipes to fabricate outer shape of solid microneedles’ tip.