Atomic Force Microscopy (AFM) has become an indispensable metrology tool for nanoscale surface characterization. Today, research and industry demand faster and more accurate metrology and these demands must be met expediently. Traditional AFM cantilevers and associated actuators (i.e. piezoelectric) are limited in regards to actuation speed and resonance frequency presenting the user with an undesired trade-off of speed versus resolution. Based on a pre-existing technology known as the FIRAT (Force Sensing Integrated Readout and Active Tip) AFM probe, this work aims to remedy actuation and response issues by implementing a cantilever-on-cantilever probe as well as a novel seesaw probe. Both cases implement electrostatic actuation, eliminating the need for piezoelectrics while demonstrating large - micron scale - actuation and sensitive displacement detection. These new probe designs can potentially demonstrate a wide bandwidth frequency response (e.g. 100 kHz) ideal for high-speed video-rate imaging. Unlike traditional AFM cantilevers, this is realized by mechanically coupling two physically separate structures to provide a soft resonator sensor atop a stiff actuator structure. Common surface-micromachining techniques are utilized to solve the logistical challenge of fabricating these stacked structures. By manipulating the viscous damping and mechanical mode coupling it becomes feasible to attain the aforementioned desired dynamic characteristics.

In diesem Report wird eine Niederenergie-Implantationskammer (NEI-Kammer) beschrieben, die im Forschungszentrum Rossendorf entwickelt und aufgebaut wurde. Die Kammer ermöglicht es, die Implantation von Ionen bei niedrigen Energien (< 30 keV) mit einer Implantationsanlage für mittlere Energien durchzuführen. In der Kammer werden der Ionenstrahl, den der Implanter liefert, auf die erwünschte niedrige Energie abgebremst. Dazu wird ein elektrostatisches Bremslinsensystem eingesetzt, das auf einem neuartigen Prinzip basiert. Das System besteht aus einer Sammellinse und einer Zerstreuungslinse, wobei die Öffnungsfehler beider Linsen entgegengesetzte Vorzeichen besitzen und sich gegenseitig kompensieren. Dadurch ist es möglich, Wafer gebräuchlicher Größe bei geringer Energie mit hoher Dosishomogenität zu implantieren. Die NEI-Kammer ist insbesondere für Forschungseinrichtungen eine vorteilhafte Lösung, da sie eine wesentlich kostengünstigere und flexiblere Alternative zur Anschaffung einer Niederenergie-Implantationsanlage darstellt.

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Title from PDF of title page. / Document formatted into pages; contains 88 pages. / Thesis (M.S.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: In this work, a multi dimensional RF MEMS variable capacitor that utilizes electrostatic actuation is designed and fabricated on a 425um thick silicon substrate. Electrostatic actuation is preferred over other actuation mechanisms due to low power consumption. The RF MEMS variable capacitor is designed in a CPW topology, with multiple beams supported (1 - 7 beams) on a single pedestal. The varactors are fabricated using surface micromachining techniques. A 1um thick silicon monoxide (Er - 6) is used as a dielectric layer for the varactor. The movable membrane is suspended on a 2.5um thick electroplated gold pedestal. The capacitance between the membrane and the bottom electrode increases as the bias voltage between the membrane and the bottom electrode is increased, eventually causing the membrane to snap down at the actuation voltage. For the varactors designed herein, the actuation voltage is approximately 30 - 90V. / ABSTRACT: Full-wave electromagnetic simulations are performed from 1 - 25GHz to accurately predict the frequency response of the varactors. The EM simulations and the measurement results compare favorably. A series RLC equivalent circuit is used to model the varactor and used to extract the parasitics associated with the capacitor by optimizing the model with the measurement results. The measured capacitance ratio is approximately 12:1 with a tuning range from 0.5 - 6pF. Furthermore, the measured S-parameter data is used to extract the unloaded Q of the varactor (at 1GHz) and is found to be 234 in the up state and 27 in the down state. An improved anodic bonding technique to bond high resistivity Si substrate and low alkali borax glass substrate that finds potential application towards packaging of MEMS varactors is investigated. To facilitate the packaging of the varactors the temperature is maintained at 400°C. The bonding time is approximately 7min at an applied voltage of 1KV. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

The electrostatic actuation with its several advantages is the main principle for micro-electro-mechanical systems (MEMS). One major drawback is the nonlinear behavior, which results into instability, known as the electrostatic pull-in effect. This effect might also push a closed-loop configuration into instability and thus makes a linear time-invariant control inapplicable to the system. The paper investigates the stability of an acceleration sensor in closed-loop operation with this setting. A simplified controller adjustment gives a first insight into this topic. Practical implementations saturate on the quantizer's full-scale value, which is also considered in the stability analysis. Numerical phase-plane analysis verifies the stability and shows further surprising results.

A dust layer, especially based on high-resistivity dust, at the collecting electrodes may cause a back corona discharge in electrostatic precipitators (ESP). It can significantly reduce the ESP efficiency and as a result cause ecological damages. To study the dust layer influence inside ESPs, it is necessary to derive an adequate model of the ESP precipitation process with a dust layer at the collecting electrode. The research of the present thesis is focused on stationary studies of the precipitation process with a dust layer at the collecting electrode in ESPs. Three mathematical models are proposed as a description of the precipitation process with a dust layer at the collecting electrode. The models are based on Maxwell’s equations and the finite element method (FEM). COMSOL Multiphysics software is used for their implementation. In all models the dust layer has constant conductivity and the air region has constant ion mobility. In the first model there are no coupling conditions, which is required in mathematics, are given between the two regions. The solution found by COMSOL Multiphysics does not provide physically acceptable coupling conditions. In the second model, a continuous transition zone is introduced between the two regions so that no coupling conditions are required. With the large derivatives in the transition zone, the nonlinear solver in COMSOL Multiphysics does not converge. Finally, in the third model, the dust layer and the grounded collecting electrode are replaced with a boundary condition for the air region. The properties of the third model are investigated, and these models can be used to study the influence of the dust layer. The results of these investigations are reported and discussed.

Polymeric waveguide-on-flex has the potential to replace complex and costly light-turning devices in optoelectronic applications. As light signals are propagated and confined through the definition of core-cladding interface, the light guiding structure is required to adhere well and ensure long term interfacial stability. This thesis addresses the gap that has emerged in the fundamental material issues such as the polymeric optical waveguide materials deposited on the flexible substrates. In addition, this thesis investigates the feasibility of a new approach using electrostatic-induced lithography in micro-patterning of polymer, in optical waveguide fabrication. Plasma treatment is applied to enhance interfacial adhesion between flex substrates and optical cladding layers. The modified flex surfaces of polyimide KaptonHNTM and liquid crystal polymer VecstarTM materials are characterised. In addition, sonochemical surface treatment is evaluated on these flexible substrates. ToF-SIMS depth profiling has confirmed the interface reaction mechanisms where it has shown that plasma treatment increases the interfacial interpenetration. The larger interfacial width increases the possible entanglement mechanism between the polymer chains. These results, together with the double cantilever beam testing, indicate the strengthening of the polymeric interface upon plasma treatment, which is essential for long term optical and mechanical stability of waveguide-on-flex applications. A new method of micro-pattering of polymer material has been adopted for fabricating multimode waveguide-on-flex. The method, using an electrostatic-induced lithography, is developed to produce 50 μm x 50 μm arrays of polysiloxane LightlinkTM waveguide on flex. This thesis looks at various process recipes of the technique and reports the pattern formation of polymeric optical core. By adjusting the spin-coated liquid core thickness, pre-bake condition, UV exposure and applied voltage, the aspect ratio and profile of the optical core microstructure can be varied. As the electrostatic pressure overcoming the surface tension of spin-coated waveguide material induces the optical core formation, the core structure is smooth, making it ideal for low scattering loss waveguide. The propagation loss of fabricated waveguide is measured at 1.97 dB/cm at 850 nm wavelength. The result shows that the use of electrostatic-induced lithography in optical polymer is a promising approach for low cost and low temperature (<150 °C) processing at back end optical-electrical integrated circuitry assembly.

The electrostatic field created by the inward pointing dipole moments of an oriented membrane leaflet has never been measured directly, but is thought to have an important influence on membrane function. Here we present the first direct measurement of the membrane dipole field in lipid bicelles using vibrational Stark effect spectroscopy which is based on the sensitivity of a nitrile oscillator’s vibrational frequency to its local electrostatic environment. The nitrile probe was introduced as the artificial amino acid p-cyanophenylalanine (CN-Phe) in four different locations of a α-helical peptide composed of alternating alanine and leucine residues. This peptide was intercalated into bicelles composed of mixtures of the long chain lipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and the short chain lipid 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) formed in two different sizes, 5 nm and 15 nm in radius. Formation of the bicelle above the phase transition temperature of the lipid mixture was confirmed by ³¹P NMR, and the structure of the [alpha]-helix within the bicelle was confirmed by circular dichroic spectroscopy. The absorption energy of the nitrile probe at 4 positions along the helical axis was measured by Fourier transform infrared spectroscopy, from which we estimate the magnitude of the membrane dipole electrostatic field to be -6 MV/cm. Then we successfully manipulated the dipole field in q = 0.5 DMPC/DHPC bicelles by incorporating the small molecule phloretin into the membrane and measured the corresponding ratiometric fluorescence signal of the co-intercalated voltage gated dye di-8-ANEPPS. We measured 0.7 ± 0.2 cm⁻¹ blue shift in absorption energy of the nitrile probe due to the decrease in dipole field caused by phloretin, corresponding to a dipole field of -4.2 MV/cm. This change was essentially identical to what has been estimated through ratiometric fluorescence methods, indicating that VSE spectroscopy will be useful tool for measurement of the biological effects of electrostatic fields in lipid membranes. / text

Noncovalent factors, such as shape complementarity and electrostatic driving forces, almost exclusively cause the affinity and specificity for which two or more biological macromolecules organize into a functioning complex. The human oncoprotein p21Ras (Ras) and a structurally identical but functionally distant analog, Rap1A (Rap), exhibit high selectivity and specificity when binding to downstream effector proteins that cannot be explained through structural analysis alone. Both Ras and Rap bind to Ral guanine nucleotide dissociation stimulator (RalGDS) with affinities that differ tenfold instigating diverse cellular functions; it is hypothesized that this specificity of RalGDS to discriminate between GTPases is largely electrostatic in nature. To investigate this hypothesis, electrostatic fields at the binding interface between mutants of RalGDS bound to Rap or Ras are measured using vibrational Stark effect (VSE) spectroscopy, in which spectral shifts of a probe oscillator’s energy is related directly to that probe’s local electrostatic environment and measured by Fourier transform infrared spectroscopy (FTIR). After calibration, the probe is inserted into a known position in RalGDS where it becomes a highly local, sensitive, and directional reporter of fluctuations of the protein’s electrostatic field caused by structural or chemical perturbations of the protein. The thiocyanate (SCN) vibrational spectroscopic probe was systematically incorporated throughout the binding interface of RalGDS. Changes in the absorption energy of the thiocyanate probe upon binding were directly related to the change of the strength of the local electrostatic field in the immediate vicinity of the probe, thereby creating a comprehensive library of the binding interactions between Ras-RalGDS and Rap-RalGDS. The measured SCN absorption energy on the monomeric protein was compared with solvent-accessible surface area (SASA) calculations with the results highlighting the complex structural and electrostatic nature of protein-water interface. Additional SASA studies of the nine RalGDS mutants that bind to Ras or Rap verified that experimentally measured thiocyanate absorption energies are negatively correlated with exposure to water at the protein-water interface. By changing the solvent composition, we confirmed that the cyanocysteine residues that are more exposed to solvent experienced a large difference in absorption energy. These studies reinforce the hypothesis that differences in the electrostatic environment at the binding interfaces of Ras and Rap are responsible for discriminating binding partners. / text

The functional aspects of proteins are largely dictated by highly selective protein- protein and protein-ligand interactions, even in situations of high structural homology, where electrostatic factors are the major contributors to selectivity. The vibrational Stark effect (VSE) allows us to measure electrostatic fields in complex environments, such as proteins, by the introduction of a vibrational chromophore whose vibrational absorption energy is linearly sensitive to changes in the local electrostatic field. The works presented here seek to computationally quantify electrostatic fields measured via VSE, with the eventual goal of being able to quantitatively predict electrostatic fields, and therefore Stark shifts, for any given protein-interaction. This is done using extensive molecular dynamics in the Amber03 and AMOEBA force fields to generate large ensembles the GTPase Rap1a docked to RalGDS and [superscript p]²¹Ras docked to RalGDS. We discuss how side chain orientations contribute to the differential binding of different mutations of Rap1a binding to RalGDS, where it was found that a hydrogen-bonding pocket is disrupted by the mutation of position 31 from lysine to glutamic acid. We then show that multi-dimensional umbrella sampling of the probe orientations yields a wider range of accessible structures, increasing the quality of the ensembles generated. A large variety of methods for calculating electrostatic fields are presented, with Poisson- Boltzmann electrostatics yielding the most consistent, reliable results. Finally, we explore using AMOEBA for both ensemble-generation as well as the electrostatic description of atoms for field calculations, where early results suggest that the electrostatic field due to the induce dipole moment of the probe is responsible for predicting qualitatively correct Stark shifts.