DESIGN AND FABRICATION OF RESONANT GAS SENSOR FOR HIGH SENSITIVITY IN THE PRESENCE OF AIR DAMPING

Gas sensors have been used widely in different important area including industrial control, environmental monitoring, counter-terrorism and chemical production. Micro-fabrication offers a promising way to achieve sensitive and inexpensive gas sensors. Over the years, various MEMS gas sensors have been investigated and fabricated. One significant type of MEMS gas sensors is based on mass change detection and the integration with specific polymer. This dissertation aims to make contributions to the design and fabrication of MEMS resonant mass sensors with capacitance actuation and sensing that lead to improved sensitivity. To accomplish this goal, the research has several objectives: (1) Define an effective measure for evaluating the sensitivity of resonant mass devices; (2) Model the effects of air damping on microcantilevers and validate models using laser measurement system (3) Develop design guidelines for improving sensitivity in the presence of air damping; (4) Characterize the degree of uncertainty in performance arising from fabrication variation for one or more process sequences, and establish design guidelines for improved robustness. Work has been completed toward these objectives. An evaluation measure has been developed and compared to an RMS based measure. Analytic models of air damping for parallel plate that include holes are compared with a COMSOL model. The models have been used to identify cantilever design parameters that maximize sensitivity. Additional designs have been modeled with COMSOL and the development of an analytical model for Fixed-free cantilever geometries with holes has been developed. Two process flows have been implemented and compared. A number of cantilever designs have been fabricated and the uncertainty in process has been investigated. Variability from processing have been evaluated and characterized.

Enzyme engineering of aminotransferases for improved activity and thermostability

The production by biosynthesis of optically active amino acids and amines satisfies the pharmaceutical industry in its demand for chiral building blocks for the synthesis of various pharmaceuticals. Among several enzymatic methods that allow the synthesis of optically active aminoacids and amines, the use of minotransferase is a promising one due to its broad substrate specificity and no requirement for external cofactor regeneration. The synthesis of chiral compounds by aminotransferases can be done either by asymmetric synthesis starting from keto acids or ketones, and by kinetic resolution starting from racemic aminoacids or amines. The asymmetric synthesis of substituted (S)-aminotetralin, an active pharmaceutical ingredient (API), has shown to have two major factors that contribute to increasing the cost of production. These factors are the raw material cost of biocatalyst used to produce it and product loss during biocatalyst separation. To minimize the cost contribution of biocatalyst and to minimize the loss of product, two routes have been chosen in this research: 1. To engineer the aminotransferase biocatalyst to have greater specific activity, and 2. Improve the engineering of the process by immobilization of biocatalyst in calcium alginate and addition of cosolvents. An (S)-aminotransferase (Mutant CNB03-03) was immobilized, not as purified enzyme but as enzyme within spray dried cells, in calcium alginate beads and used to produce substituted (S)-aminotetralin at 50 °C and pH 7 in experiments where the immobilized biocatalyst was recycled. Initial rate of reaction for cycle 1 (6 hr duration) was determined to be 0.258 mM/min, for cycle 2 (20 hr duration) it decreased by ~50% compared to cycle 1, and for cycle 3 (20 hr duration) it decreased by ~90% compared to cycle 1 (immobilized preparation consisted of 50 mg of spray dried cells per gram of calcium alginate). Conversion to product for each cycle decreased as well, from 100% in cycle 1 (About 50 mM), 80% in cycle 2, and 30% after cycle 3. This mutant was determined to be deactivated at elevated temperatures during the reaction cycle and was not stable enough to allow multiple cycles in its immobilized form. A new mutant aminotransferase was isolated by applying error-prone polymerase chain reaction (PCR) on the gene coding for this enzyme and screening/selection: CNB04-01. This mutant showed a significant improvement in thermostability in comparison to CNB03-03. The new mutant was immobilized and tested under similar reaction conditions. Initial rate remained fairly constant (0.2 mM/min) over four cycles (each cycle with a duration of about 20 hours) with the mutant retaining almost 80% of initial rate in the fourth cycle. The final product concentrations after each cycle did not decrease during recycle experiments. Thermostability of CNB04-01 was much improved compared to CNB03-03. Under the same reaction conditions as stated above, the addition of co-solvents was studied in order to increase substituted tetralone solubility. Toluene and sodium dodecylsulfate (SDS) were used. SDS at 0.01% (w/v) allowed four recycles of the immobilized spray dried cells of CNB04-01, always reaching higher product concentration (80-85 mM) than the system with toluene at 3% (v/v) -70 mM-. The long term activity of immobilized CNB04-01 in a system with SDS 0.01% (w/v) at 50 °C, pH 7 was retained for three cycles (20 to 24 hours each one), reaching always final product concentration between 80-85 mM, but dropping precipitously in the fourth cycle to a final product concentration of 50 mM. Although significant improvement of immobilization on productivity and stability were observed using CNB04-01, another observation demonstrated the limitations of an immobilization strategy on reducing process costs. After analyzing the results of this experiment it was seen that a sudden drop occurred on final product concentration after the third recycle. This was due to product accumulation inside the immobilized preparation. In order to improve the economics of the process, research was focused on developing a free enzyme with an even higher activity, thus reducing raw material cost as well as improving biomass separation. A new enzyme was obtained (CNB05-01) using error-prone PCR and screening using as a template the gene derived from the previous improved enzyme. This mutant was determined to have 1.6 times the initial rate of CNB04-01 and had a higher temperature optimum (55°). This new enzyme would allow reducing enzyme loading in the reaction by five-fold compared to CNB03-03, when using it at concentration of one gram of spray dried cells per liter (completing the reaction after 20-24 hours). Also this mutant would allow reducing process time to 7-8 hours when used at a concentration of 5 grams of spray dried cells per liter compared to 24 hours for CNB03-03, assuming that the observations shown before are scalable. It could be possible to improve the economics of the process by either reducing enzyme concentration or reducing process time, since the production cost of the desired product is primarily a function of both enzyme concentration and process time.

Computational simulations of latent heat thermal energy storage systems - with innovative and first-principles based simulation for the underlying unsteady melting (and solidification) processes

This thesis develops an effective modeling and simulation procedure for a specific thermal energy storage system commonly used and recommended for various applications (such as an auxiliary energy storage system for solar heating based Rankine cycle power plant). This thermal energy storage system transfers heat from a hot fluid (termed as heat transfer fluid - HTF) flowing in a tube to the surrounding phase change material (PCM). Through unsteady melting or freezing process, the PCM absorbs or releases thermal energy in the form of latent heat. Both scientific and engineering information is obtained by the proposed first-principle based modeling and simulation procedure. On the scientific side, the approach accurately tracks the moving melt-front (modeled as a sharp liquid-solid interface) and provides all necessary information about the time-varying heat-flow rates, temperature profiles, stored thermal energy, etc. On the engineering side, the proposed approach is unique in its ability to accurately solve – both individually and collectively – all the conjugate unsteady heat transfer problems for each of the components of the thermal storage system. This yields critical system level information on the various time-varying effectiveness and efficiency parameters for the thermal storage system.

Metal-oxide film and photonic structures for integrated device applications

The application of photonic crystal technology on metal-oxide film is a very promising field for future optical telecommunication systems. Band gap and polarization effects in lithium niobate (LiNbO3) photonic crystals and bismuth-substituted iron garnets (BiYIG) photonic crystals are investigated in this work reported here. The design and fabrication process are similar for these two materials while the applications are different, involving Bragg filtering in lithium niobate and polarization rotation in nonreciprocal iron garnets. The research of photonic structures in LiNbO3 is of high interest for integrated device application due to its remarkable electro-optical characteristics. This work investigated the photonic band gap in high quality LiNbO3 single crystalline thin film by ion implantation to realize high efficiency narrow bandwidth filters. LiNbO3 thin film detachment by bonding is also demonstrated for optical device integration. One-dimensional Bragg BiYIG waveguides in gyrotropic system are found to have multiple stopbands and evince enhancement of polarization rotation efficiency. Previous photon trapping theory cannot explain the phenomena because of the presence of linear birefringence. This work is aimed at investigating the mechanism with the support of experiments. The results we obtained show that selective suppression of Bloch states in gyrotropic bandgaps is the key mechanism for the observed phenomena. Finally, the research of ferroelectric single crystal PMN-PT with ultra high piezoelectric coefficient as a biosensor is also reported. This work presents an investigation and results on higher sensitivity effects than conventional materials such as quartz and lithium niobate.

Looking at the effectiveness of an earth science unit designed using the Understanding by Design process

This report shares my efforts in developing a solid unit of instruction that has a clear focus on student outcomes. I have been a teacher for 20 years and have been writing and revising curricula for much of that time. However, most has been developed without the benefit of current research on how students learn and did not focus on what and how students are learning. My journey as a teacher has involved a lot of trial and error. My traditional method of teaching is to look at the benchmarks (now content expectations) to see what needs to be covered. My unit consists of having students read the appropriate sections in the textbook, complete work sheets, watch a video, and take some notes. I try to include at least one hands-on activity, one or more quizzes, and the traditional end-of-unit test consisting mostly of multiple choice questions I find in the textbook. I try to be engaging, make the lessons fun, and hope that at the end of the unit my students get whatever concepts I‘ve presented so that we can move on to the next topic. I want to increase students‘ understanding of science concepts and their ability to connect understanding to the real-world. However, sometimes I feel that my lessons are missing something. For a long time I have wanted to develop a unit of instruction that I know is an effective tool for the teaching and learning of science. In this report, I describe my efforts to reform my curricula using the “Understanding by Design” process. I want to see if this style of curriculum design will help me be a more effective teacher and if it will lead to an increase in student learning. My hypothesis is that this new (for me) approach to teaching will lead to increased understanding of science concepts among students because it is based on purposefully thinking about learning targets based on “big ideas” in science. For my reformed curricula I incorporate lessons from several outstanding programs I‘ve been involved with including EpiCenter (Purdue University), Incorporated Research Institutions for Seismology (IRIS), the Master of Science Program in Applied Science Education at Michigan Technological University, and the Michigan Association for Computer Users in Learning (MACUL). In this report, I present the methodology on how I developed a new unit of instruction based on the Understanding by Design process. I present several lessons and learning plans I‘ve developed for the unit that follow the 5E Learning Cycle as appendices at the end of this report. I also include the results of pilot testing of one of lessons. Although the lesson I pilot-tested was not as successful in increasing student learning outcomes as I had anticipated, the development process I followed was helpful in that it required me to focus on important concepts. Conducting the pilot test was also helpful to me because it led me to identify ways in which I could improve upon the lesson in the future.

Design of a lab scale direct-filtration system and its application in process lab

The Environmental Process and Simulation Center (EPSC) at Michigan Technological University started accommodating laboratories for an Environmental Engineering senior level class CEE 4509 Environmental Process and Simulation Laboratory since 2004. Even though the five units that exist in EPSC provide the students opportunities to have hands-on experiences with a wide range of water/wastewater treatment technologies, a key module was still missing for the student to experience a full cycle of treatment. This project fabricated a direct-filtration pilot system in EPSC and generated a laboratory manual for education purpose. Engineering applications such as clean bed head loss calculation, backwash flowrate determination, multimedia density calculation and run length prediction are included in the laboratory manual. The system was tested for one semester and modifications have been made both to the direct filtration unit and the laboratory manual. Future work is also proposed to further refine the module.

Automated design of self-stabilization

Self-stabilization is a property of a distributed system such that, regardless of the legitimacy of its current state, the system behavior shall eventually reach a legitimate state and shall remain legitimate thereafter. The elegance of self-stabilization stems from the fact that it distinguishes distributed systems by a strong fault tolerance property against arbitrary state perturbations. The difficulty of designing and reasoning about self-stabilization has been witnessed by many researchers; most of the existing techniques for the verification and design of self-stabilization are either brute-force, or adopt manual approaches non-amenable to automation. In this dissertation, we first investigate the possibility of automatically designing self-stabilization through global state space exploration. In particular, we develop a set of heuristics for automating the addition of recovery actions to distributed protocols on various network topologies. Our heuristics equally exploit the computational power of a single workstation and the available parallelism on computer clusters. We obtain existing and new stabilizing solutions for classical protocols like maximal matching, ring coloring, mutual exclusion, leader election and agreement. Second, we consider a foundation for local reasoning about self-stabilization; i.e., study the global behavior of the distributed system by exploring the state space of just one of its components. It turns out that local reasoning about deadlocks and livelocks is possible for an interesting class of protocols whose proof of stabilization is otherwise complex. In particular, we provide necessary and sufficient conditions – verifiable in the local state space of every process – for global deadlock- and livelock-freedom of protocols on ring topologies. Local reasoning potentially circumvents two fundamental problems that complicate the automated design and verification of distributed protocols: (1) state explosion and (2) partial state information. Moreover, local proofs of convergence are independent of the number of processes in the network, thereby enabling our assertions about deadlocks and livelocks to apply on rings of arbitrary sizes without worrying about state explosion.

SCIENTIFIC MANAGEMENT SYSTEMS AS ENFRAMING OR EMPOWERING: HOW LEAN AND SIX SIGMA DEFINE TECHNICAL COMMUNICATION

In this project, I examine current forms of scientific management systems, Lean and Six Sigma, as they relate to technical communication. With the goal of breaking work up into standardized processes in order to cut costs and increase efficiency, Lean, Six Sigma and Lean Six Sigma hybrid systems are increasingly applied beyond manufacturing operations to service and other types of organizational work, including technical communication. By consulting scholarship from fields such as business, management, and engineering, and analyzing government Lean Six Sigma documentation, I investigate how these systems influence technical communication knowledge and practice in the workplace. I draw out the consequences of system-generated power structures as they affect knowledge work, like technical communication practice, when it is reduced to process. In pointing out the problems these systems have in managing knowledge work, I also ask how technical communication might shape them.

DESIGN AND IMPLEMENTATION OF HOME USE PORTABLE SMART ELECTRONICS

The widespread of low cost embedded electronics makes it easier to implement the smart devices that can understand either the environment or the user behaviors. The main object of this project is to design and implement home use portable smart electronics, including the portable monitoring device for home and office security and the portable 3D mouse for convenient use. Both devices in this project use the MPU6050 which contains a 3 axis accelerometer and a 3 axis gyroscope to sense the inertial motion of the door or the human hands movement. For the portable monitoring device for home and office security, MPU6050 is used to sense the door (either home front door or cabinet door) movement through the gyroscope, and Raspberry Pi is then used to process the data it receives from MPU6050, if the data value exceeds the preset threshold, Raspberry Pi would control the USB Webcam to take a picture and then send out an alert email with the picture to the user. The advantage of this device is that it is a small size portable stand-alone device with its own power source, it is easy to implement, really cheap for residential use, and energy efficient with instantaneous alert. For the 3D mouse, the MPU6050 would use both the accelerometer and gyroscope to sense user hands movement, the data are processed by MSP430G2553 through a digital smooth filter and a complementary filter, and then the filtered data will pass to the personal computer through the serial COM port. By applying the cursor movement equation in the PC driver, this device can work great as a mouse with acceptable accuracy. Compared to the normal optical mouse we are using, this mouse does not need any working surface, with the use of the smooth and complementary filter, it has certain accuracy for normal use, and it is easy to be extended to a portable mouse as small as a finger ring.

DESIGN AND SYNTHESIS OF MULTIFUNCTIONAL POLYMERIC MICELLES FOR GENE-DIRECTED ENZYME PRODRUG THERAPY

Gene-directed enzyme prodrug therapy is a form of cancer therapy in which delivery of a gene that encodes an enzyme is able to convert a prodrug, a pharmacologically inactive molecule, into a potent cytotoxin. Currently delivery of gene and prodrug is a two-step process. Here, we propose a one-step method using polymer nanocarriers to deliver prodrug, gene and cytotoxic drug simultaneously to malignant cells. Prodrugs acyclovir, ganciclovir and 5-doxifluridine were used to directly to initiate ring-opening polymerization of epsilon-caprolactone, forming a hydrophobic prodrug-tagged poly(epsilon-caprolactone) which was further grafted with hydrophilic polymers (methoxy poly(ethylene glycol), chitosan or polyethylenemine) to form amphiphilic copolymers for micelle formation. Successful synthesis of copolymers and micelle formation was confirmed by standard analytical means. Conversion of prodrugs to their cytotoxic forms was analyzed by both two-step and one-step means i.e. by first delivering gene plasmid into cell line HT29 and then challenging the cells with the prodrug-tagged micelle carriers and secondly by complexing gene plasmid onto micelle nanocarriers and delivery gene and prodrug simultaneously to parental HT29 cells. Anticancer effectiveness of prodrug-tagged micelles was further enhanced by encapsulating chemotherapy drugs doxorubicin or SN-38. Viability of colon cancer cell line HT29 was significantly reduced. Furthermore, in an effort to develop a stealth and targeted carrier, CD47-streptavidin fusion protein was attached onto the micelle surface utilizing biotin-streptavidin affinity. CD47, a marker of self on the red blood cell surface, was used for its antiphagocytic efficacy, results showed that micelles bound with CD47 showed antiphagocytic efficacy when exposed to J774A.1 macrophages. Since CD47 is not only an antiphagocytic ligand but also an integrin associated protein, it was used to target integrin alpha(v)beta(3), which is overexpressed on tumor-activated neovascular endothelial cells. Results showed that CD47-tagged micelles had enhanced uptake when treated to PC3 cells which have high expression of alpha(v)beta(3). The synthesized multifunctional polymeric micelle carriers developed could offer a new platform for an innovative cancer therapy regime.