The goals of this research were first to examine flame quenching in tubing smaller than the quench diameter, and then to place lower size limits on microcombustor and microreactor systems by studying a catalytic microcombustor burning propane. In the first set of experiments, flame quenching was examined as a function of wall temperature for various hydrocarbon fuels. This was accomplished by creating a wall temperature profile along a tube, allowing a flame to propagate down the tube, and measuring the temperature of the tube wall coincident with the flame front. This wall quench temperature was plotted as a function of both the equivalence ratio and tube diameter. Fuels tested included propane, hexane, kerosene and diesel. Results showed that quench diameter was reduced by elevating the wall temperature and that the quench temperature increased for increasing mixture flow velocities. Flames were produced in tubes down to 0.8 mm in diameter. In the second set of experiments, a catalyst was used in combination with fuel preheating to obtain a self-sustaining combustion reaction in a chamber approximately 0.25 mm³ in size. Propane was used in this experiment. Results demonstrated that a stable self-sustaining reaction can be obtained in the microscale regime and that reaction temperatures are on the order of 900°C. This research not only aided in the characterization of hydrocarbon combustion in small diameter channels but also showed promise for development of microcombustor systems. / Graduation date: 2002

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

The aim of this master thesis has been to design, and partly manufacture and evaluate, a highly miniaturized, on-chip conductivity-temperature-depth (CTD) sensor system for deepwater analysis also including electrodes for pH and chloride ion concentration measurements. The microtechnology-based sensor system will be a vital instrument onboard the Deeper Access, Deeper Understanding submersible, which will be small enough for deployment through bore holes into the subglacial lakes of Antarctica. Design of the complete 15 x 30 mm chip, including variations of each sensor type (in total 39 sensors), is presented. Salinity (through conductivity), temperature, chloride ion concentration and pH sensors have been manufactured using conventional lithography, evaporation, wet etching and lift off techniques. Simulations of the pressure sensors (not manufactured) show how the set of four bossed membranes with integrated strain gauges combine to cover, yet withstand, pressures of 1-100 atm. Salinity is measured conductively with gold electrodes. The temperature sensor is a platinum thermoresistor. Chloride ion concentration and pH are measured potentiometrically with ion-selective microelectrodes of silver/silver chloride and iridium oxide, respectively. Tests of the conductivity sensor gave good results also on sea water samples of known salinity. The temperature sensor showed good linearity to a reference sensor in the tested range of 5-35 C. Issues with evaporation and lift off are discussed, and a process identification document is attached. / DADU

Cooling systems that consist of mini-channels (hydraulic diameters in the 0.5 mm to 2.0 mm range) and micro-channels (hydraulic diameters in the 100 m-500 m range) can dispose of extremely large volumetric thermal loads that are well beyond the feasible operating range of conventional cooling methods. Mini/micro-channel systems that utilize boiling fluids are particularly useful due to the superiority of boiling heat transfer mode over single-phase flow convection. Although forced flow boiling in mini and micro-channels has been investigated by several research groups in the past, a verified and reliable predictive method is not yet available. In this study, the capability of a large number of forced flow boiling heat transfer correlations for application to mini channels is examined by comparing their predictions with three experimental data sets. The data all represent recently-published experiments with mini-channels The tested correlations include well-established methods for forced-flow boiling in conventional boiling systems, as well as correlations recently proposed for mini-channels. Based on these comparisons, the most accurate existing predictive methods for mini-channel boiling are identified. The deficiencies of the predictive methods and the potential causes that underlie these deficiencies are also discussed.

Atomic force microscope (AFM) is an invaluable tool for measurement of pico-Newton to nano-Newton levels of interaction forces in liquid. As such, it is widely used to measure single-molecular interaction forces through dynamic force spectroscopy. In this technique, the interaction force spectra between a specimen on the sharp tip of the cantilever and another specimen on the substrate is measured by repeatedly moving the cantilever in and out of contact with the substrate. By varying the loading rate and measuring the bond rupture force or bond lifetime give researchers information about the strength and dissociation rates of non-covalent bonds, which in turn determines the energy barriers to overcome. Commercially available cantilevers can resolve interaction forces as low as 5 pN with 1 kHz bandwidth in fluid. This resolution can be improved to 1 pN by using smaller cantilevers at the expense of microfabrication constraints and sophisticated detection systems. The pulling speed of the cantilever, which determines the loading rate of the bonds, is limited to the point where the hydrodynamic drag force becomes comparable to the level of the molecular interaction force. This level is around 10 um/s for most cantilevers while higher pulling speeds are required for complete understanding of force spectra. Thus, novel actuators that allow higher loading rates with minimal hydrodynamic drag forces on the cantilevers, and fast, sensitive force sensors with simple detection systems are highly desirable. This dissertation presents the research efforts for the development of membrane-based active probe structures with electrostatic actuation and integrated diffraction-based optical interferometric force detection for single-molecular force measurements. Design, microfabrication and characterization of the probes are explained in detail. A setup including optics and electronics for experimental characterization and biological experiments with the probes membranes is also presented. Finally, biological experiments are included in this dissertation. The "active" nature of the probe is because of the integrated, parallel-plate type electrostatic actuator. The actuation range of the membrane is controlled with the gap height between the membrane and the substrate. Within this range it is possible to actuate the membrane fast, with a speed limited by the membrane dynamics with negligible hydrodynamic drag. Actuating these membrane probes and using a cantilever coupled to the membrane, fast pulling experiments with an order of magnitude faster than achieved by regular AFM systems are demonstrated. The displacement noise spectral density for the probe was measured to be below 10 fm/rtHz for frequencies as low as 3 Hz with differential readout scheme. This noise floor provides a force sensitivity of 0.3 - 3 pN with 1 kHz bandwidth using membranes with spring constants of 1 - 10 N/m. This low inherent noise has a potential to probe wide range of biomolecules. The probes have been demonstrated for fast-pulling and high-resolution force sensing. Feasibility for high throughput parallel operation has been explored. Unique capabilities of the probes such as electrostatic spring constant tuning and thermal drift cancellation in AFM are also presented in this dissertation.

Not available

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 14, 2009) Includes bibliographical references (p. 16-17).

Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 116-131).