Control design and genetic algorithm optimization for electrostatic MEMS

This dissertation discusses structural-electrostatic modeling techniques, genetic algorithm based optimization and control design for electrostatic micro devices. First, an alternative modeling technique, the interpolated force model, for electrostatic micro devices is discussed. The method provides improved computational efficiency relative to a benchmark model, as well as improved accuracy for irregular electrode configurations relative to a common approximate model, the parallel plate approximation model. For the configuration most similar to two parallel plates, expected to be the best case scenario for the approximate model, both the parallel plate approximation model and the interpolated force model maintained less than 2.2% error in static deflection compared to the benchmark model. For the configuration expected to be the worst case scenario for the parallel plate approximation model, the interpolated force model maintained less than 2.9% error in static deflection while the parallel plate approximation model is incapable of handling the configuration. Second, genetic algorithm based optimization is shown to improve the design of an electrostatic micro sensor. The design space is enlarged from published design spaces to include the configuration of both sensing and actuation electrodes, material distribution, actuation voltage and other geometric dimensions. For a small population, the design was improved by approximately a factor of 6 over 15 generations to a fitness value of 3.2 fF. For a larger population seeded with the best configurations of the previous optimization, the design was improved by another 7% in 5 generations to a fitness value of 3.0 fF. Third, a learning control algorithm is presented that reduces the closing time of a radiofrequency microelectromechanical systems switch by minimizing bounce while maintaining robustness to fabrication variability. Electrostatic actuation of the plate causes pull-in with high impact velocities, which are difficult to control due to parameter variations from part to part. A single degree-of-freedom model was utilized to design a learning control algorithm that shapes the actuation voltage based on the open/closed state of the switch. Experiments on 3 test switches show that after 5-10 iterations, the learning algorithm lands the switch with an impact velocity not exceeding 0.2 m/s, eliminating bounce.

Quantum dot / optical protein bio-nano hybrid system biosensing

The integration of novel nanomaterials with highly-functional biological molecules has advanced multiple fields including electronics, sensing, imaging, and energy harvesting. This work focuses on the creation of a new type of bio-nano hybrid substrate for military biosensing applications. Specifically it is shown that the nano-scale interactions of the optical protein bacteriorhodopsin and colloidal semiconductor quantum dots can be utilized as a generic sensing substrate. This work spans from the basic creation of the protein to its application in a novel biosensing system. The functionality of this sensor design originates from the unique interactions between the quantum dot and bacteriorhodopsin molecule when in nanoscale proximity. A direct energy transfer relationship has been established between coreshell quantum dots and the optical protein bacteriorhodopsin that substantially enhances the protein’s native photovoltaic capabilities. This energy transfer phenomena is largely distance dependent, in the sub-10nm realm, and is characterized experimentally at multiple separation distances. Experimental results on the energy transfer efficiency in this hybrid system correlate closely to theoretical predictions. Deposition of the hybrid system with nano-scale control has allowed for the utilization of this energy transfer phenomena as a modulation point for a functional biosensor prototype. This work reveals that quantum dots have the ability to activate the bacteriorhodopsin photocycle through both photonic and non-photonic energy transfer mechanisms. By altering the energy transferred to the bacteriorhodopsin molecule from the quantum dot, the electrical output of the protein can be modulated. A biosensing prototype was created in which the energy transfer relationship is altered upon target binding, demonstrating the applicability of a quantum dot/bacteriorhodopsin hybrid system for sensor applications. The electrical nature of this sensing substrate will allow for its efficient integration into a nanoelectronics array form, potentially leading to a small-low power sensing platform for remote toxin detection applications.

CHARACTERIZATION OF ASPHALT MATERIALS CONTAINING BIO OIL FROM MICHIGAN WOOD

The objective of this research is to develop sustainable wood-blend bioasphalt and characterize the atomic, molecular and bulk-scale behavior necessary to produce advanced asphalt paving mixtures. Bioasphalt was manufactured from Aspen, Basswood, Red Maple, Balsam, Maple, Pine, Beech and Magnolia wood via a 25 KWt fast-pyrolysis plant at 500 °C and refined into two distinct end forms - non-treated (5.54% moisture) and treated bioasphalt (1% moisture). Michigan petroleum-based asphalt, Performance Grade (PG) 58-28 was modified with 2, 5 and 10% of the bioasphalt by weight of base asphalt and characterized with the gas chromatography-mass spectroscopy (GC-MS), Fourier Transform Infra-red (FTIR) spectroscopy and the automated flocculation titrimetry techniques. The GC-MS method was used to characterize the Carbon-Hydrogen-Nitrogen (CHN) elemental ratio whiles the FTIR and the AFT were used to characterize the oxidative aging performance and the solubility parameters, respectively. For rheological characterization, the rotational viscosity, dynamic shear modulus and flexural bending methods are used in evaluating the low, intermediate and high temperature performance of the bio-modified asphalt materials. 54 5E3 (maximum of 3 million expected equivalent standard axle traffic loads) asphalt paving mixes were then prepared and characterized to investigate their laboratory permanent deformation, dynamic mix stiffness, moisture susceptibility, workability and constructability performance. From the research investigations, it was concluded that: 1) levo, 2, 6 dimethoxyphenol, 2 methoxy 4 vinylphenol, 2 methyl 1-2 cyclopentandione and 4-allyl-2, 6 dimetoxyphenol are the dominant chemical functional groups; 2) bioasphalt increases the viscosity and dynamic shear modulus of traditional asphalt binders; 3) Bio-modified petroleum asphalt can provide low-temperature cracking resistance benefits at -18 °C but is susceptible to cracking at -24 °C; 3) Carbonyl and sulphoxide oxidation in petroleum-based asphalt increases with increasing bioasphalt modifiers; 4) bioasphalt causes the asphaltene fractions in petroleum-based asphalt to precipitate out of the solvent maltene fractions; 5) there is no definite improvement or decline in the dynamic mix behavior of bio-modified mixes at low temperatures; 6) bio-modified asphalt mixes exhibit better rutting performance than traditional asphalt mixes; 7) bio-modified asphalt mixes have lower susceptibility to moisture damage; 8) more field compaction energy is needed to compact bio-modified mixes.

The Laboratory Evaluation of Bio Oil Derived From Waste Resources as Extender for Asphalt Binder

A shortage of petroleum asphalt is creating opportunities for engineers to utilize alternative pavement materials. Three types of bio oils, original bio oil (OB), dewatered bio oil (DWB) and polymer-modified bio oil (PMB) were used to modify and partially replace petroleum asphalt in this research. The research investigated the procedure of producing bio oil, the rheological properties of asphalt binders modified and partially replaced by bio oil, and the mechanical performances of asphalt mixtures modified by bio oil. The analysis of variance (ANOVA) is conducted on the test results for the significance analysis. The main finding of the study includes: 1) the virgin bioasphalt is softer than the traditional asphalt binder PG 58-28 but stiffer after RTFO aging because bio oil ages much faster than the traditional asphalt binder during mixing and compaction; 2) the binder test showed that the addition of bio oil is expected to improve the rutting performance while reduce the fatigue and low temperature performance; 3) both the mass loss and the oxidation are important reasons for the bio oil aging during RTFO test; the mixture test showed that 1) most of the bio oil modified asphalt mixture had slightly higher rutting depth than the control asphalt mixture, but the difference is not statistically significant; 2) the dynamic modulus of some of the bio oil modified asphalt mixture were slightly lower than the control asphalt mixture, the E* modulus is also not statistically significant; 3) most of the bio oil modified asphalt mixture had higher fatigue lives than the control asphalt mixture; 4) the inconsistence of binder test results and mixture test results may be attributed to that the aging during the mixing and compaction was not as high as that in the RTFO aging simulation. 5) the implementation of Michigan wood bioasphalt is anticipated to reduce the emission but bring irritation on eyes and skins during the mixing and compaction.

A MEMS Light Modulator Based on Diffractive Nanohole Gratings

We present the design, fabrication, and testing of a microelectromechanical systems (MEMS) light modulator based on pixels patterned with periodic nanohole arrays. Flexure-suspended silicon pixels are patterned with a two dimensional array of 150 nm diameter nanoholes using nanoimprint lithography. A top glass plate assembled above the pixel array is used to provide a counter electrode for electrostatic actuation. The nanohole pattern is designed so that normally-incident light is coupled into an in-plane grating resonance, resulting in an optical stop-band at a desired wavelength. When the pixel is switched into contact with the top plate, the pixel becomes highly reflective. A 3:1 contrast ratio at the resonant wavelength is demonstrated for gratings patterned on bulk Si substrates. The switching time is 0.08 ms and the switching voltage is less than 15V.

NON-CHROMATOGRAPHIC PURIFICATION OF SYNTHETIC BIO-OLIGOMERS

Synthetic oligonucleotides and peptides have found wide applications in industry and academic research labs. There are ~60 peptide drugs on the market and over 500 under development. The global annual sale of peptide drugs in 2010 was estimated to be $13 billion. There are three oligonucleotide-based drugs on market; among them, the FDA newly approved Kynamro was predicted to have a $100 million annual sale. The annual sale of oligonucleotides to academic labs was estimated to be $700 million. Both bio-oligomers are mostly synthesized on automated synthesizers using solid phase synthesis technology, in which nucleoside or amino acid monomers are added sequentially until the desired full-length sequence is reached. The additions cannot be complete, which generates truncated undesired failure sequences. For almost all applications, these impurities must be removed. The most widely used method is HPLC. However, the method is slow, expensive, labor-intensive, not amendable for automation, difficult to scale up, and unsuitable for high throughput purification. It needs large capital investment, and consumes large volumes of harmful solvents. The purification costs are estimated to be more than 50% of total production costs. Other methods for bio-oligomer purification also have drawbacks, and are less favored than HPLC for most applications. To overcome the problems of known biopolymer purification technologies, we have developed two non-chromatographic purification methods. They are (1) catching failure sequences by polymerization, and (2) catching full-length sequences by polymerization. In the first method, a polymerizable group is attached to the failure sequences of the bio-oligomers during automated synthesis; purification is achieved by simply polymerizing the failure sequences into an insoluble gel and extracting full-length sequences. In the second method, a polymerizable group is attached to the full-length sequences, which are then incorporated into a polymer; impurities are removed by washing, and pure product is cleaved from polymer. These methods do not need chromatography, and all drawbacks of HPLC no longer exist. Using them, purification is achieved by simple manipulations such as shaking and extraction. Therefore, they are suitable for large scale purification of oligonucleotide and peptide drugs, and also ideal for high throughput purification, which currently has a high demand for research projects involving total gene synthesis. The dissertation will present the details about the development of the techniques. Chapter 1 will make an introduction to oligodeoxynucleotides (ODNs), their synthesis and purification. Chapter 2 will describe the detailed studies of using the catching failure sequences by polymerization method to purify ODNs. Chapter 3 will describe the further optimization of the catching failure sequences by polymerization ODN purification technology to the level of practical use. Chapter 4 will present using the catching full-length sequence by polymerization method for ODN purification using acid-cleavable linker. Chapter 5 will make an introduction to peptides, their synthesis and purification. Chapter 6 will describe the studies using the catching full-length sequence by polymerization method for peptide purification.

Generierung von Konstruktionsmerkmalen zur Entwicklung eines bio-inspirierten Kommissionier- Greifers für die Intralogistik mittels Clusteranalyse

Kurzbeschreibung: In der Automatisierung von intralogistischen Kommissioniervorgängen ist ein großes Zukunftspotential erkennbar. Elementarer Bestandteil des Automatisierungsprozesses ist der Einsatz von Industrierobotern, die mit einem geeigneten Endeffektor, dem Greifer, ausgestattet werden müssen. Die Robotik ist in der Lage schneller, präziser und ausdauernder als die menschlichen Kommissionierer zu arbeiten und trägt damit entscheidend zur Effizienzsteigerung bei. Eine wesentliche Herausforderung für diesen Entwicklungsschritt zur Substitution der manuellen Kommissionierung ist die Konstruktion und Bereitstellung eines geeigneten Greifsystems. Am Lehrstuhl für Maschinenelemente und Technische Logistik der Helmut-Schmidt-Universität wurde mit der Erfahrung aus einem vorangegangenen Forschungsprojekt die Methode der Clusteranalyse erstmalig zur Untersuchung von Greifobjekten zur Entwicklung eines bionischen Universalgreifers für die Kommissionierung von Drogerieartikeln verwendet. Diese Abhandlung beschreibt einen Beitrag zur Entwicklung dieses Greifers am Beispiel handelsüblicher Drogerieartikel, die aktuell manuell kommissioniert werden. Diese werden hinsichtlich der für das Greifen relevanten Objektmerkmale geclustert und die daraus resultierenden Erkenntnisse in Form von Konstruktionsmerkmalen abgeleitet. Nach einer Analyse und Festlegung der greifrelevanten Merkmale der Greifobjekte wird eine Objektdatenbasis erstellt. Mit Hilfe geeigneter Methoden wird die gewonnene Datenbasis aufbereitet und reduziert. Im Anschluss werden die Greifobjekte bzw. deren Merkmalsausprägungen einer hierarchischen Clusteranalyse unterzogen. Hierbei werden die Grenzen der gebildeten Cluster mittels der zugehörigen Greifobjekte festgelegt und analysiert. Abschließend werden bestimmte greiferspezifische Merkmale auf die Anwendbarkeit in den Clustern überprüft und bewertet. Diese Betrachtungen ermöglichen es, dass spezielle Anforderungen an den Greifer, die direkt aus den Eigenschaften der Greifobjekte herrühren, zuverlässig erkannt und konstruktiv berücksichtigt werden können.

Nano-mechanical transduction of polymer micro-cantilevers to detect bio-molecular interactions

Using variothermal polymer micro-injection molding, disposable arrays of eight polymer micro-cantilevers each 500 μm long, 100 μm wide and 25 μm thick were fabricated. The present study took advantage of an easy flow grade polypropylene. After gold coating for optical read-out and asymmetrical sensitization, the arrays were introduced into the Cantisens(®) Research system to perform mechanical and functional testing. We demonstrate that polypropylene cantilevers can be used as biosensors for medical purposes in the same manner as the established silicon ones to detect single-stranded DNA sequences and metal ions in real-time. A differential signal of 7 nm was detected for the hybridization of 1 μM complementary DNA sequences. For 100 nM copper ions the differential signal was found to be (36 ± 5) nm. Nano-mechanical sensing of medically relevant, nanometer-size species is essential for fast and efficient diagnosis.

Comparison of the toxicity of diesel exhaust produced by bio- and fossil diesel combustion in human lung cells in vitro

Alternative fuels are increasingly combusted in diesel- and gasoline engines and the contribution of such exhausts to the overall air pollution is on the rise. Recent findings on the possible adverse effects of biodiesel exhaust are contradictive, at least partly resulting from the various fuel qualities, engine types and different operation conditions that were tested. However, most of the studies are biased by undesired interactions between the exhaust samples and biological culture media. We here report how complete, freshly produced exhausts from fossil diesel (B0), from a blend of 20% rapeseed-methyl ester (RME) and 80% fossil diesel (B20) and from pure rapeseed methyl ester (B100) affect a complex 3D cellular model of the human airway epithelium in vitro by exposing the cells at the air–liquid interface. The induction of pro-apoptotic and necrotic cell death, cellular morphology, oxidative stress, and pro-inflammatory responses were assessed. Compared to B0 exhaust, B20 exhaust decreased oxidative stress and pro-inflammatory responses, whereas B100 exhaust, depending on exposure duration, decreased oxidative stress but increased pro-inflammatory responses. The effects are only very weak and given the compared to fossil diesel higher ecological sustainability of biodiesel, it appears that – at least RME – can be considered a valuable alternative to pure fossil diesel.

Optimizing Models of the North Atlantic Spring Bloom Using Physical, Chemical and Bio-Optical Observations from a Lagrangian Float

The North Atlantic spring bloom is one of the main events that lead to carbon export to the deep ocean and drive oceanic uptake of CO(2) from the atmosphere. Here we use a suite of physical, bio-optical and chemical measurements made during the 2008 spring bloom to optimize and compare three different models of biological carbon export. The observations are from a Lagrangian float that operated south of Iceland from early April to late June, and were calibrated with ship-based measurements. The simplest model is representative of typical NPZD models used for the North Atlantic, while the most complex model explicitly includes diatoms and the formation of fast sinking diatom aggregates and cysts under silicate limitation. We carried out a variational optimization and error analysis for the biological parameters of all three models, and compared their ability to replicate the observations. The observations were sufficient to constrain most phytoplankton-related model parameters to accuracies of better than 15 %. However, the lack of zooplankton observations leads to large uncertainties in model parameters for grazing. The simulated vertical carbon flux at 100 m depth is similar between models and agrees well with available observations, but at 600 m the simulated flux is larger by a factor of 2.5 to 4.5 for the model with diatom aggregation. While none of the models can be formally rejected based on their misfit with the available observations, the model that includes export by diatom aggregation has a statistically significant better fit to the observations and more accurately represents the mechanisms and timing of carbon export based on observations not included in the optimization. Thus models that accurately simulate the upper 100 m do not necessarily accurately simulate export to deeper depths.

A lung-on-chip array with an integrated bio-inspired respiration mechanism

We report about a lung-on-chip array that mimics the pulmonary parenchymal environment, including the thin, alveolar barrier and the three-dimensional cyclic strain induced by the breathing movements. A micro-diaphragm used to stretch the alveolar barrier is inspired by the in-vivo diaphragm, the main muscle responsible for inspiration. The design of this device aims not only at best reproducing the in-vivo conditions found in the lung parenchyma, but also at making its handling easy and robust. An innovative concept, based on the reversible bonding of the device, is presented that enables to accurately control the concentration of cells cultured on the membrane by easily accessing both sides of the membranes. The functionality of the alveolar barrier could be restored by co-culturing epithelial and endothelial cells that formed tight monolayers on each side of a thin, porous and stretchable membrane. We showed that cyclic stretch significantly affects the permeability properties of epithelial cell layers. Furthermore, we could also demonstrate that the strain influences the metabolic activity and the cytokine secretion of primary human pulmonary alveolar epithelial cells obtained from patients. These results demonstrate the potential of this device and confirm the importance of the mechanical strain induced by the breathing in pulmonary research.