Carbon/molecule/Cu/Au molecular junctions were fabricated on 4-inch silicon wafers using microfabrication techniques common in commercial semiconductor manufacturing. Electron-beam deposited carbon films are introduced as substrates, and the junctions exhibited high yield and excellent reproducibility. Current density-voltage characteristics of the devices were area scaling, weakly dependent on temperature and exponentially on molecular film thickness, and quantitatively similar to those of devices made with other techniques reported previously in our group, which contained pyrolyzed photoresist films as substrates. Furthermore, the test of cycle life and thermal stability reveals that the devices can survive at least under several millions of potential cycles at room temperature in air, and elevated temperature up to 150 C in vacuum for >40 hours. Parallel fabrication, thermal stability, and high yield are required for practical applications of molecular electronics, and the reported results provide important steps toward integration of molecular electronic devices with commercial processes and devices.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 178-197).

Imagine if you could combine the power and capabilities ofan entire laboratory in the palm of your hand. Advances inmicrofluidic chip technology promise to integrate andminiaturize multiple lab processes into a single palm-sizeddevice. The advantages of these lab-on-a-chip devices,sometimes also referred to as micro total analysis systems(µTAS), compared with conventional bench-scale systems arenumerous and wide ranging and include: less reagentconsumption, low manufacturing costs, increased performance,faster analysis, high sample throughput, integration andautomation possibilities, and disposability. However,microfluidic devices also present challenges such as theinterfacing to the macro world and detection limits. In this thesis the focus has been to develop novel discretemicrofluidic components for biotechnology and organic chemicalapplications with the goal to integrate them to formlab-on-chips. A flow-through filter-chamber device has beendesigned, manufactured and evaluated for chemical analysis onbeads. Passive liquid handling has been integrated on the chipin the form of hydrophobic valves at the inlet channels. Anarray format has also been developed to allow parallel analysisof multiple samples. The filter-chamber functions well forsingle nucleotide analysis using pyrosequencing. Initialevaluations on catalyst screening in the filter-chamber devicehas been performed. The suitability of valve-less micropumps for biochemicalapplications is presented. Fluids encountered in variousbiochemical methods, including living cells, that areproblematic for other micropumps have been pumped with goodperformance. This thesis also introduces expandablemicrospheres as a novel component in microfluidics includingapplications such as one-shot valves, micropositioning andsurface enlargement. A novel technique for bead immobilization in microfluidicdevices based on surface chemistry is presented in this thesis.Beads for both biochemical assays and organic chemistry havebeen self-sorted and self-assembled in line patterns as narrowas 5 µm on both structured and unstructured substrates.This method will greatly facilitate the generation of screeningplatforms, for example. To develop a microfluidic device for catalysis-on-chip,ligands for asymmetric catalysis have successfully beenimmobilized in silicon channels by consecutive microcontactprinting, which is a novel technique presented in thisthesis. <b>Keywords:</b>microfluidics, beads, microspheres, silicon,filter-chamber, flow-through, bead trapping, DRIE, passivevalves, fluorocarbon, microfluidic array, adhesive bonding,valve-less micropump, microcontact printing, PDMS,self-assembly, self-sorting, DNA, SNP, pyrosequencing,allele-specific extension, expandable microspheres, catalysis,chiral ligand, monolayer, miniaturization, lab-on-a-chip,µTAS.

Le travail de thèse a consisté à développer des voies originales de microfabrication pour laconception d'électrodes qui pourront être utilisées dans un biocapteur basé sur unetransduction électrochimique. Une des perspectives étant de pouvoir intégrer ce type decapteur dans un microsystème analytique à base microfluidique, nous avons fait le choix duverre comme matériau de base. Par ailleurs, nous avons privilégié les technologies de" lithographie douce " au détriment de voies classiques telles que la photolithographie afin derendre inutile l'accès à des salles à environnement contrôlé ou l'utilisation d'appareillagessophistiqués.Lors de ce travail, nous avons plus particulièrement travaillé sur le développement deméthodes combinant la technique de microtamponnage et la métallisation chimique de typeautocatalytique (electroless). Cette métallisation nécessitant des surfaces catalytiques pourfaire croître la couche métallique, nous avons développé des méthodes de traitements desurface afin de rendre le substrat de base catalytique sur toute sa surface. La technique demicrotamponnage a ensuite été utilisée afin de passiver les zones où la métallisation n'est pasdésirée et cela a mené à des microstructures métalliques en surface du verre présentant peu oupas de défauts. Notre approche nous a conduit à utiliser plusieurs types de catalyseurs sous laforme de nanoparticules métalliques à base d'argent, d'or ou de palladium et nous avonsdiscuté les différences entre les méthodes basées sur ces différents catalyseurs.Une autre voie a consisté à graver de façon localisée des couches minces métalliquesuniformes en protégeant les zones ne devant pas être gravées par la technique demicrotamponnage. Ceci a permis le développement de deux voies originales demicrostructuration sur couches minces métalliques uniformes (d'une part le pelage sélectif etd'autre part le procédé à double inversion).Dans l'ensemble de nos travaux, des caractérisations d'extrême surface par les techniquesSEM, AFM, ToF-SIMS, XPS et de mouillabilité ont été menées afin d'optimiser ledéveloppement des différents procédés.

Monitoring bio-electric events is a common procedure, which provides medical data required in clinical and research applications. Electrophysiological measurements are applied in diagnosis as well as evaluation of the performance of different body organs and systems, e. g. the heart, muscles and the nervous system. Furthermore, it is staple feature in operation rooms and extensive care units. The performance of the recording system is affected by the tools and instrumentation used and the bio-electrode is a key-player in electrophysiology, hence, the improvements in the electrode recording technique will be directly reflected in the system?s performance in terms of the signal quality, recording duration as well as patient comfort. In this thesis, a design methodology for micro-spike array dry bio-electrodes is introduced. <br /><br /> The purpose of this methodology is to meet the design specifications for portable long-term EEG recording and optimize the electrical performance of the electrodes by maximizing the electrode-skin contact surface area, while fulfilling design constraints including mechanical, physiological and economical limitations. This was followed by proposing a low cost fabrication technique to implement the electrodes. The proposed electrode design has a potential impact in enhancing the performance of the current recording systems, and also suits portable monitoring and long term recording devices. The design process was aided by using a software design and optimization tool, which was specifically created for this application. <br /><br /> The application conditions added challenges to the electrode design in order to meet the required performance requirements. On the other hand, the required design specifications are not fulfilled in the current electrode technologies which are designed and customized only for short term clinical recordings. <br /><br /> The electrode theory of application was verified using an experimental setup for an electrochemical cell, but the overall performance including measuring the electrode impedance is awaiting a clinical trial.

Arguments for miniaturization of a thermal field-flow fractionation system ( and #956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar methods was presented. Motivation for miniaturization of ThFFF systems was established by examining the geometrical scaling of the fundamental ThFFF theory. Miniaturization of conventional macro-scale ThFFF systems was made possible through utilization of micromachining technologies. Fabrication of the and #956;-ThFFF system was discussed in detail. The and #956;-ThFFF system was characterized for plate height versus flow rate, single component polystyrene retention, and multi-component polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macro-scale ThFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0ױ0-8 and 5.4ױ0-8 cm2/sec?? The maximum diameter-based selectivity was 1.40. While the concept of an acoustic FFF sub-technique has been around for decades, the fabrication methods have not been available until recently. The theory was developed in full including relating sample physical properties to retention time in the FFF system. In addition to the theory, the design and fabrication of the and #956;-AcFFF was presented. Design results from an acoustic modeling program were presented with the determination of the acoustic resonant frequency. The acoustic-based systems was designed around the model results and characterized by electrical input impedance, fluidic, plate height, polystyrene suspension retention, and polystyrene mixture separation studies. The and #956;-AcFFF system was able to retain a series of nanometer scale polystyrene samples. However, the retention data did not follow normal mode retention but did reveal the location of the steric inversion point for the power level used, around 200 nm. The results of the multiple component separation confirmed this results as the sample, which contained 110, 210, and 300 nm diameter samples, was not resolved but only broadened.

This dissertation presents the design, fabrication, and testing of a microfluidic system to be used for whole-cell analysis. The study of cellular function and structure is essential for disease diagnosis and treatment. Microsystems developed to perform these bioanalyses add benefits such as requiring smaller samples and reagents, testing multiple samples in parallel, and supporting point-of-care testing, all of which increases throughput and reduces cost-per-analysis. Traditional methods for designing a microsystem use standard materials and techniques such as silicon, glass, photolithography, and wet and dry etching. This research is focused on utilizing materials and techniques that require less infrastructure, allow for a faster design-to-prototype cycle, and can integrate electrical and fluidic functionality to address a variety of possible applications. The microfluidic system presented in this thesis is comprised of multiple layers of Kapton, a polyimide available from DuPont. Kapton provides a biocompatible substrate that is flexible while maintaining structural stability and can be used in high temperature and other harsh environments. Microchannels with widths of 400 m and thru-hole fluidic vias less than 5 m in diameter are laser ablated through the flexible polyimide sheets using excimer and CO2 lasers. Electrical traces and contact pads are defined on the substrate by vapor deposition through reusable microstencils rather than with photolithography. The patterned layers are bonded using heat staking and then packaged with the addition of wires and a fluidic interface. Validation of the system for whole-cell analysis was first performed with impedance spectroscopy measurements collected on air, DI water, phosphate buffered saline, clusters of human cancer cells, and human cancer tissue samples. This was followed by testing the ability to use the device to control the movement and position of 10 m diameter microbeads and dissociated cells. As a whole, this research demonstrates the realization of a microfluidic system for whole-cell analysis based on non-standard fabrication materials and techniques.

<p>Imagine if you could combine the power and capabilities ofan entire laboratory in the palm of your hand. Advances inmicrofluidic chip technology promise to integrate andminiaturize multiple lab processes into a single palm-sizeddevice. The advantages of these lab-on-a-chip devices,sometimes also referred to as micro total analysis systems(µTAS), compared with conventional bench-scale systems arenumerous and wide ranging and include: less reagentconsumption, low manufacturing costs, increased performance,faster analysis, high sample throughput, integration andautomation possibilities, and disposability. However,microfluidic devices also present challenges such as theinterfacing to the macro world and detection limits.</p><p>In this thesis the focus has been to develop novel discretemicrofluidic components for biotechnology and organic chemicalapplications with the goal to integrate them to formlab-on-chips. A flow-through filter-chamber device has beendesigned, manufactured and evaluated for chemical analysis onbeads. Passive liquid handling has been integrated on the chipin the form of hydrophobic valves at the inlet channels. Anarray format has also been developed to allow parallel analysisof multiple samples. The filter-chamber functions well forsingle nucleotide analysis using pyrosequencing. Initialevaluations on catalyst screening in the filter-chamber devicehas been performed.</p><p>The suitability of valve-less micropumps for biochemicalapplications is presented. Fluids encountered in variousbiochemical methods, including living cells, that areproblematic for other micropumps have been pumped with goodperformance. This thesis also introduces expandablemicrospheres as a novel component in microfluidics includingapplications such as one-shot valves, micropositioning andsurface enlargement.</p><p>A novel technique for bead immobilization in microfluidicdevices based on surface chemistry is presented in this thesis.Beads for both biochemical assays and organic chemistry havebeen self-sorted and self-assembled in line patterns as narrowas 5 µm on both structured and unstructured substrates.This method will greatly facilitate the generation of screeningplatforms, for example.</p><p>To develop a microfluidic device for catalysis-on-chip,ligands for asymmetric catalysis have successfully beenimmobilized in silicon channels by consecutive microcontactprinting, which is a novel technique presented in thisthesis.</p><p><b>Keywords:</b>microfluidics, beads, microspheres, silicon,filter-chamber, flow-through, bead trapping, DRIE, passivevalves, fluorocarbon, microfluidic array, adhesive bonding,valve-less micropump, microcontact printing, PDMS,self-assembly, self-sorting, DNA, SNP, pyrosequencing,allele-specific extension, expandable microspheres, catalysis,chiral ligand, monolayer, miniaturization, lab-on-a-chip,µTAS.</p>

In this work, MEMS based fabrication is used to engineer multifaceted enhancements to microfluidic systems such as lab-on-a-chip devices. Two specific elements of microfluidic systems are the focus of this study: microfluidic chambers and microneedles. Microfluidic chambers, which are back-end passive elements, via proposed material and structural modifications, are shown to exhibit reduced non-specific DNA binding and enable increased cell lysis efficiency. Microneedles, which are front-end interfacing elements, have been fabricated in silicon and in silicon dioxide varieties. The geometry of silicon microneedles has been varied via DRIE processing to yield sharpened tips. Sharpening of microneedle tips provides reduced skin insertion force without compromising structural strength. Variation of skin insertion force of microneedles with change in tip sharpness has been studied, and toughness of human skin derived to be approximately 26 kJ/m². The axial and shear fracture limits of the microneedles have also been studied. Axial fracture of 36 gauge silicon needles takes place at an average force of 740gf. Shear fracture force of silicon needles varies from 275gf (33 gauge needles) to 35.6gf (36 gauge needles). Fracture limits of circular and square shaped silicon dioxide needles show reduced strength of square needles; which is pronounced in the case of shear fracture.

The unique frequency range and robustness of surface acoustic wave (SAW) devices has been a catalyst for their adoption as integral components in a range of consumer and military electronics. Furthermore, the strain and piezoelectric fields associated with SAWs are finding novel applications in nanostructured devices. In this thesis, the interaction of SAWs with periodic elastic structures, such as photonic or phononic crystals (PnCs), is studied both computationally and experimentally. To predict the behaviour of elastic waves in PnCs, a finite-difference time-domain simulator (PnCSim) was developed using C++. PnCSim was designed to calculate band structures and transmission spectra of elastic waves through two-dimensional PnCs. By developing appropriate boundary conditions, bulk waves, surface acoustic waves, and plate waves can be simulated. Results obtained using PnCSim demonstrate good agreement with theoretical data reported in the literature. To experimentally investigate the behaviour of SAWs in PnCs, fabrication procedures were developed to create interdigitated transducers (IDTs) and PnCs. Using lift-off photolithography, IDTs with finger widths as low as 1.8 um were fabricated on gallium arsenide (GaAs), corresponding to a SAW frequency of 397 MHz. A citric acid and hydrogen peroxide wet-etching solution was used to create shallow air hole PnCs in square and triangular lattice configurations, with lattice constants of 8 um and 12 um, respectively. The relative transmission of SAWs through these PnCs as a function of frequency was determined by comparing the insertion losses before and after etching the PnCs. In addition, using a scanning Sagnac interferometer, displacement maps were measured for SAWs incident on square lattice PnCs by Mathew (Creating and Imaging Surface Acoustic Waves on GaAs, Master’s Thesis). Reasonable agreement was found between simulations and measurements. Additional simulations indicate that SAW waveguiding should be possible with a PnC consiting of air holes in GaAs. The phononic properties of a commonly used photonic plate were also determined. Band structure simulations of the plate displayed no complete elastic band gaps. However, transmission simulations indicated that a pseudo-gap may form for elastic waves polarized in the sagittal plane. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-12-23 16:24:33.164