Zhou Wenli. / "October 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In electrochemical sensing, the miniaturisation of electrodes leads to enhanced characteristics, including higher signal-to-noise ratio and lower detection limits and sensitivity to external convection due to more efficient mass transport. In recent years, this has generated considerable interest in both the manufacturing and characterisation of nanoelectrodes. However, the high-volume, commercial fabrication of integratable, low cost nanoelectrodes remains a challenge. This work presents a nanoelectrode architecture that can be manufactured using established and well-characterised microfabrication methods. Vertical ring electrodes are fabricated at hole edges using thin film deposition and microlithography techniques. A metal layer of nanometre thickness is sandwiched between two insulators on a substrate followed by the etching of micron scale holes through the stack of layers. This leads to the exposure of a metal nanoband around the hole perimeter and thus a nanoelectrode with the area defined by the hole perimeter and the deposited metal layer thickness. This work first reports a simulation study, which investigates the in uence of design parameters such as band and insulator thicknesses and hole size on the diffusive current. The results show a relative independence of the current to the band thickness and a linear dependence on the hole perimeter with a steady state current comparable to that of a microelectrode. For example, a nanoband electrode with a band thickness of 50nm produces up to approximately half of the limiting current measured on a planar microsquare electrode and a 25 nm electrode produces 88% of the current of a 50 nm electrode. This information contributed to the development of a process for the fabrication of arrays of platinum nanoband electrodes in microsquare holes on a silicon substrate with control over the critical geometric parameters. Electrodes with band thicknesses of 5 nm to 50 nm and a range of square side lengths have been fabricated for experimental validation. Their performance has been compared to microsquare electrode arrays, and was shown to give a similar response to established microdisc and square electrodes. An analysis procedure has been developed and inherent nanoelectrode behaviour and effects have been investigated. The relative importance of a range of nanoeffects on the electrodes has been assessed, indicating a contribution of migration to mass transfer. It has been demonstrated that these nanoband electrodes can be used to detect rapid processes such as the measurement of large electrochemical rate constants, unlike microsquare array electrodes.

Abstract In this study, we use microfabrication processes on silicon to produce a rectangular microchannel. The fabrication technology includes exposing, dry etching, and anodic bounding technologies. After fabrication finished, we use AFM and alpha-step to secure surface roughness. It is found a relatively low surface roughness about 3.34¢H with dimension of 0.5£gm¡Ñ100£gm¡Ñ5000£gm microchannel. A theoretical study and calculations, we also made with continuity equation and proper slip condition to analyze fluid behavior in microchannel. At present, several fluid informations in microchannel that incloud pressure drop, fluid velocity, and fluid mass flow rate were obtained.

Thesis (Ph.D.)--City University of Hong Kong, 2009. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references.

Thesis (Ph.D.) -- University of Texas at Arlington, 2007.

As one of the few 3D microfabrication techniques available to researchers, multiphoton lithography (MPL) has generated considerable interest in the scientific community. By allowing researchers to localize photochemistry to a femtoliter volume, MPL has permitted the fabrication of intricate, 3D microstructures from a range of materials, including protein hydrogels. MPL can be used to fabricate functional hydrogels on the scale of 100 μm, with features on the order of 1 μm. This dissertation examines existing MPL techniques to discover ways in which current processes can be modified to produce hydrogel products that are more useful for biomedical applications like tissue engineering. A new material is introduced that enables the fabrication of fully unconstrained hydrogel microstructures. In this context, A structure can be classified as “unconstrained” when it is free to translate and rotate without hindrance in three dimensions, and is not attached to the substrate or any other structure. New processes are demonstrated that permit the fabrication of larger MPL hydrogels without sacrificing feature resolution. This allows the fabrication of millimeter-scale, high aspect ratio structures with features smaller than 10 μm. Methods are described for tuning and measuring the mechanical properties of MPL-fabricated hydrogels, and ways of tuning the functional properties of the hydrogels are also examined. / text

Tissue engineering is a recently developed field that combines material science, cell biology, and engineering to create or improve functional tissues/organs. The field of tissue engineering has progressed from a fledgling science to an emerging technology, in large part due to parallel advances in the application of biomaterials and understanding stem cell behavior. Current studies have evaluated certain types of natural and synthetic biomaterials for feasibility of replicating the physio-chemical microenvironments of stem cells. Furthermore, technologies derived from micro-machining and solid free-form fabrication industries have utilized these biomaterials to create scaffolds that resemble tissue-like structures. Recent scaffold fabrication methods have attempted to overcome certain challenges in engineering tissues and organs. One of the fundamental limitations in current tissue engineering efforts has been the inability to develop multiple tissue types (i.e. bone, cartilage, muscles, ligaments) within a single scaffold structure in a predesigned manner. The differentiation of multiple cells within a three-dimensional (3D) scaffold using a single stem cell population has yet to be developed due to challenges in integrating various biochemical factors in a spatially-patterned method. This dissertation discusses scaffold micro-fabrication techniques that use layerby-layer, ultraviolet-based (UV) stereolithography systems. These approaches in microfabricating scaffolds provide an optimal, biomimetic environment for the pre-patterned differentiation of mesenchymal stem cells into skeletal-type tissues. We demonstrated both laser-based and digital micromirror device-based stereolithography systems for creating intricate scaffold architectures with multiple bio-factors encapsulated in predetermined regions. We showed that micro-stereolithography has the powerful capability of building 3D complex scaffolds with specific pore sizes and shapes in a layer-by-layer fashion using photo-crosslinkable monomers. These polymer-based scaffolds were functionalized with specific signaling proteins to create a biomimetic niche in which stem cells can respond, attach, and differentiate. The ultimate goal of this project is to integrate novel concepts of micro-manufacturing along with polymer-controlled release kinetics and stem cell biology to attain pre-designed architectures of tissue structures. / text

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Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.