Bio-microdevices are miniaturised devices based on biologically derived components (e.g., DNA, proteins, and cells) combined or integrated with microfabricated substrates. These devices are of interest for numerous applications, ranging from drug discovery, to environmental monitoring, to tissue engineering. Before a bio-microdevice can be fully developed, specific fabrication issues need to be addressed. One of the most important is the spatial immobilization of selected biomolecules in specific micro-areas of the device. Among the biomolecules of interest, the controlled immobilization of proteins to surfaces is particularly challenging due to the complexity of these macromolecules and their tendency to lose bioactivity during the immobilization step. The present Thesis reports on three novel micropatterning techniques for the spatial immobilization of proteins with bioactivity retention and improved read-out of the resulting micropatterns. The technologies developed are based on three different micropatterning approaches, namely 1) direct-writing UV laser microablation (proLAB), 2) a novel microcontact printing method (�CPTA) and 3) a replica molding method combined with bead selfassembly (BeadMicroArray). The first two technologies, proLAB and �CPTA, are an implementation of existing techniques (laser ablation and �CP, respectively), whereas the third, i.e., the BeadMicroArray, is a totally new technique and type of patterning platform. 'ProLAB' is a technology that uses a micro-dissection tool equipped with a UV laser (the LaserScissors�) for ablating a substrate made of a layer of ablatable material, gold, deposited over a thin polymer layer. The latter layer is transparent to the laser but favours protein adsorption. In the present work microchannels were chosen as the structure of interest with the aim of arranging them in 'bar-codes', so to create an 'information-addressable' microarray. This platform was fabricated and its application to specific antigen binding demonstrated. The second technique that was developed is a microstamping method which exploits the instability of a high-aspect ratio rubber stamp fabricated via soft-lithography. The technique is denominated microcontact printing trapping air (�CPTA) since the collapsing of a rubber stamp made of an array of micro-pillars over a plane glass surface resulted in the formation of a large air gap around the entire array. The method can be successfully employed for printing micro-arrays of proteins, maintaining biological activity. The technique was compared with robotic spotting and found that microarrays obtained with the �CPTA method were more homogeneous and had a higher signal-tonoise ratio. The third technique developed, the BeadMicroArray, introduces a totally new platform for the spatial addressable immobilization of proteins. It combines replica molding with microbead self-assembling, resulting in a platform where diagnostic beads are entrapped at the tip of micropillars arranged in a microarray format. The fabrication of the BeadMicroArray involves depositing functional microbeads in an array of V-shaped wells using spin coating. The deposition is totally random, and conditions were optimised to fill about half the array during spin coating. After replica molding, the resulting polymer mold contains pyramid-shaped posts with beads entrapped at the very tip of the post. Thanks to the fabrication mode involved, every BeadMicroArray fabricated contains a unique geometric code, therefore assigning a specific code to each microarray. In the present work it was demonstrated that the functionality of the beads after replica molding remains intact, and that proteins can be selectively immobilized on the beads, for instance via biorecognition. The platform showed a remarkable level of selectively which, together with an efficient blocking towards protein non-specific adsorption, lead to a read-out characterized by a very good signal-to-noise. Also, after recognition, a code was clearly visible, therefore showing the encoding capacity of this unique microarray.

The chemistry of hafnium oxide based and materials are described in the context of ion exchange and lithography. HafSOx, represented by the composition HfO₂₋[subscript x](SO₄)x, is described to possess a significant capacity towards ion exchange in acidic and basic solutions, enabling films of HafSOx to be cleanly and readily be converted to oxide films by neutralization. The optical properties, composition and morphology of these oxide films are characterized. The fabrication of mixed metal oxide films is demonstrated via solution and ion exchange routes. This thesis also explores the photoresist chemistry of HafSOx resists. A photoreaction mechanism based on the decomposition of peroxide is proposed. In addition, the patterning of HafSOx films by 193 nm, extreme ultraviolet (EUV) and electron beam radiation is described, and the influence of composition on its photoresist properties is studied. / Graduation date: 2012

Optical waveguides, quantum dot emitters, and flat top beam shapers were designed and fabricated by two soft lithographic techniques; micro transfer molding (microTM) and vacuum assisted microfluidics (VAM). Optical waveguides were fabricated through a microTM technique that utilizes a poly dimethylsiloxane (PDMS) stamp. Generation of the flexible stamp required development of a channel waveguide pattern mask, defined by maskless lithography, and followed by construction of a three dimensional channel waveguide master, acquired through contact lithography on a glass substrate coated with SU-8 photoresist. Creation of a positive imprint replicating mold was accomplished through prepolymer PDMS solution settling and curing around the master. Waveguide fabrication was achieved through PDMS conformal contact on, and subsequent curing of, ultraviolet (UV) polymer resins on a silicon substrate. A slight modification of the microTM PDMS stamp, whereby inlet and outlet tunnels were incorporated, resulted in a novel VAM structure and correspondingly waveguides. Waveguide propagation losses were determined to be 1.14 dB/cm and 0.68 dB/cm for the microTM and VAM fabricated waveguides, respectively. A lithographic approach employing quantum dots doped in SU-8 photoresist has led to the realization of a new quantum dot emitter. Uniform coating of a doped material on a silver coated substrate was followed by contact mask lithography. Evaporation of a thin silver layer, upon development of the resultant quantum dot doped channel waveguide structure, facilitates confined emission. Successful edge emitting was demonstrated with blue laser pumping. The lithographic fabrication of such quantum dot emitter is successfully replaced by soft lithographic VAM technique. A flat top beam shaper, whose profile was developed on cured UV polymer resins, was fabricated by microTM technique. The master used for the development of the PDMS stamp was produced through an iterative wet etching process capable of achieving etching depths as small as a few nanometers. Comparisons between the reference wet etched beam shaper and the microTM based beam shaper produced near identical output flat top beams from incident Gaussian beams. Through this research work, successful soft lithographic fabrication of optical waveguides, quantum dot emitters, and flat top beam shapers were demonstrated. The vast potential exhibited by these and other related technologies show great promise for cost-effective mass production of various micro optics and integrated photonic components.

The field of Information and Communication Technologies is witnessing a development speed unprecedented in history. Moore’s law proves that the processor speed and memory size are roughly doubling each 18 months, which is expected to continue in the next decade. If photonics is going to play a substantial role in the ICT market, it will have to follow the same dynamics. There are mainly two groups of components that need to be integrated. The active components, including light sources, electro-optic modulators, and detectors, are mostly fabricated in III-V semiconductors. The passive components, such as waveguides, resonators, couplers and splitters, need no power supply and can be realized in silicon-related semiconductors. The prospects of silicon photonics are particularly promising, the fabrication is mostly compatible with standard CMOS technology and the on-chip optical interconnects are expected to increase the speed of microprocessors to the next generation. This thesis starts with designs of various silicon-based devices using finite-difference time-domain simulations. Parallel computation is a powerful tool in the modeling of large-scale photonic circuits. High Q cavities and resonant channel drop filters are designed in photonic crystal platform. Different methods to couple light from a single mode fiber to silicon waveguides are studied by coupled-mode theory and verified using parallel simulations. The performance of waveguide grating coupler for vertical radiation is also studied. The fabrication of silicon-based photonic devices involves material deposition, E-beam or optical lithography for pattern defining, and plasma/wet-chemistry etching for pattern transfer. For nanometer-scaled structures, E-beam lithography is the most critical process. Depending on the structures of the devices, both positive resist (ZEP520A) and negative resist (maN2405) are used. The proximity and stitch issues are addressed by careful dose correction and patches exposure. Some examples are given including photonic crystal surface mode filter, micro-ring resonators and gold grating couplers. In particular, high Q (2.6×105), deep notch (40 dB) and resonance-splitting phenomenon are demonstrated for silicon ring resonators. It is challenging to couple light into photonic integrated circuits directly from a single-mode fiber. The butt-coupled light-injecting method usually causes large insertion loss due to small overlap of the mode profiles and large index mismatch. Practically it is not easy to cleave silicon sample with smooth facet where the waveguide exposes. By adding gold gratings to the waveguides, light can be injected and collected vertically from single-mode fiber. The coupling efficiency is much higher. There is no need to cleave the sample. The access waveguides are much shortened and the stitch problem in E-beam lithography is avoided. In summary, this thesis introduces parallel simulations for the design of modern large-scale photonic devices, addresses various issues with Si-based fabrication, and analyses the data from the characterization. Several novel devices using silicon nanowire waveguides and 2D photonic crystal structures have been demonstrated for the first time. / QC 20100923

A self-aligning nanostencil mask is used to fabricate circular features of tin, indium and silver on an atomically clean Si(001) substrate. The shadow mask limits deposited material to areas under openings in the mask, leaving adjacent clean areas for material to diffuse. STM, SEM and AFM have been used to study the surface diffusion of these metals in UHV. The diffusion of tin is relatively limited in comparison to the other metals. Indium forms metal islands that dissolve over time and contribute to the spreading of a surrounding single layer film. Lastly, silver forms a film that spreads even in the absence of metal islands.

A self-aligning nanostencil mask is used to fabricate circular features of tin, indium and silver on an atomically clean Si(001) substrate. The shadow mask limits deposited material to areas under openings in the mask, leaving adjacent clean areas for material to diffuse. STM, SEM and AFM have been used to study the surface diffusion of these metals in UHV. The diffusion of tin is relatively limited in comparison to the other metals. Indium forms metal islands that dissolve over time and contribute to the spreading of a surrounding single layer film. Lastly, silver forms a film that spreads even in the absence of metal islands.

There are a significant number of microwave applications, including active antenna arrays, wireless communication systems, navigational applications, etc., where improvement of such qualities as manufacturing costs, size, weight, power consumption, etc. is still on the agenda of todays RF design. In order to meet these requirements, new technologies must be actively involved in fabrication of RF components with improved characteristics. One of such fabrication technologies is called LIGA, used before primarily in fluidics, photonics, bioengineering, and micromechanics, and only recently receiving growing attention in RF component fabrication. One of the RF components suffering limitations in performance due to limitations in fabrication capabilities is the compact single metal layer (SML) coupled-line 3-dB coupler, also called hybrid, required in some applications thanks to its ability to divide power equally and electrically isolate the output from the input. In todays practical edge-coupled SML coupler designs, the level of coupling is limited by the capabilities of the photolithographic process to print the coupled lines close enough for tight coupling and it is usually no tighter that 8 dB. A promising way to overcome this limitation is increasing the area of metallic interface of the coupled lines, thus increasing the mutual capacitance of the lines, and inherently the coupling between them. This should be preferably done with keeping the coupler compact with respect to the footprint area, which is attained by making taller conductors, i.e. employing the third dimension. In contrast with previously used RF component fabrication processes, LIGA is the technology that allows the designer to explore the third dimension and build tall conductors while being also able to use small features. When the two-dimensional edge-coupled SML couplers are extended into the three-dimensional structures, they rather become the side-coupled SML couplers. Tall-conductor coupled lines have been characterized in this work to reveal their dependence on their geometry and a 3-dB SML coupler with tall conductors has been developed and fabricated using LIGA at the Institute for Microstructure Technology (IMT), Karlsruhe, Germany. The simulation and measurement results demonstrate the potentially superior performance of LIGA couplers, and the promising capabilities of LIGA for fabrication of RF microstructures.

There are a significant number of microwave applications, including active antenna arrays, wireless communication systems, navigational applications, etc., where improvement of such qualities as manufacturing costs, size, weight, power consumption, etc. is still on the agenda of todays RF design. In order to meet these requirements, new technologies must be actively involved in fabrication of RF components with improved characteristics. One of such fabrication technologies is called LIGA, used before primarily in fluidics, photonics, bioengineering, and micromechanics, and only recently receiving growing attention in RF component fabrication. One of the RF components suffering limitations in performance due to limitations in fabrication capabilities is the compact single metal layer (SML) coupled-line 3-dB coupler, also called hybrid, required in some applications thanks to its ability to divide power equally and electrically isolate the output from the input. In todays practical edge-coupled SML coupler designs, the level of coupling is limited by the capabilities of the photolithographic process to print the coupled lines close enough for tight coupling and it is usually no tighter that 8 dB. A promising way to overcome this limitation is increasing the area of metallic interface of the coupled lines, thus increasing the mutual capacitance of the lines, and inherently the coupling between them. This should be preferably done with keeping the coupler compact with respect to the footprint area, which is attained by making taller conductors, i.e. employing the third dimension. In contrast with previously used RF component fabrication processes, LIGA is the technology that allows the designer to explore the third dimension and build tall conductors while being also able to use small features. When the two-dimensional edge-coupled SML couplers are extended into the three-dimensional structures, they rather become the side-coupled SML couplers. Tall-conductor coupled lines have been characterized in this work to reveal their dependence on their geometry and a 3-dB SML coupler with tall conductors has been developed and fabricated using LIGA at the Institute for Microstructure Technology (IMT), Karlsruhe, Germany. The simulation and measurement results demonstrate the potentially superior performance of LIGA couplers, and the promising capabilities of LIGA for fabrication of RF microstructures.

Graduation date: 1993

In this thesis two issues in nanotechnology have been addressed. The first is the comprehensive characterization of engineered nanomaterials prior to their examination in toxicology and environmental studies. The second is the development of a method to produce nanostructure arrays over large areas and for low cost. A major challenge when assessing nanomaterial’s risks is the robust characterization of their physicochemical properties, particularly in commercial products. Such data allows the critical features for biological outcomes to be determined. This work focused on the inorganic oxides that were studied in powdered and dispersed forms as well as directly in consumer sunscreen products. The most important finding was that the commercial sunscreens that listed titania or zinc oxide as ingredients contained nanoscale materials. Cell free photochemical tests revealed that ZnO particles without any surface coating were more active at generating ROS than surface coated TiO2 nanoparticles. These studies make clear the importance of exposure studies that examine the native form of nanomaterials directly in commercial products. The second part of this thesis presents the development of a new method to fabricate gold nanoring and nanocrescent arrays over large areas; such materials have unique optical properties consonant with those described as metamaterials. A new shaped nanosphere lithography approach was used to manipulate the form of silica nanospheres packed onto a surface; the resulting array of mushroom structures provided a mask that after gold evaporation and etching left either golden rings or crescents over the surface. The structures had tunable features, with outer diameters ranging from 200 to 350 nm for rings and crescent gap angles of ten to more than a hundred degrees. The use of a double mask method ensured the uniform coverage of these structured over 1 cm2 areas. Experimental and theoretical investigations of the optical properties of the arrays revealed the optical resonances in the infrared region. Finally, in the course of developing the nanorings, etch conditions were developed to deposit large area arrays of polystyrene nanodoughnuts with diameters from 128 to 242 nm. These non-conductive structures provide an ideal template for further attachment of magnetic of optically emissive nanoparticles.