UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Investigating Energetic Porous Silicon as a Solid Propellant Micro-Thruster(2019) Churaman, Wayne Anthony; Bergbreiter, Sarah; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Energetic porous silicon has emerged as a novel on-chip energetic material capable of generating thrust that can be harnessed for positioning of millimeter and micron-scale mobile platforms such as microrobots and nano-satellites. Porous silicon becomes reactive when nano-scale pores are infused with an oxidizer such as sodium perchlorate. In this work, energetic porous silicon was investigated as a means of propulsion by quantifying thrust and impulse produced during the exothermic reaction as a function of porosity. The baseline porous silicon devices were two millimeter diameter and etched to a target depth of 25 microns. As a result of changing porosity, a 7x increase in thrust performance and a 16x increase in impulse performance was demonstrated. The highest thrust and impulse values measured were 680 mN and 266 micron Newton seconds respectively from a 2 mm diameter porous silicon device with 72 % porosity. Limitations and trade-offs associated with arrays of devices were presented by studying the effects of scaling porous silicon area, and characterizing thrust when arrays of porous silicon micro-thruster devices were ignited simultaneously. In addition, the effects of sympathetic ignition were evaluated to better understand how closely independent devices could be physically spaced on a 1 cm2 chip. 3D nozzles were fabricated to study confinement effects by varying nozzle throat diameter, and divergent angle. It was shown that integration of a nozzle (throat diameter of 0.75 mm and a divergent angle of theta = 10 degrees) resulted in approximately 4X increase in thrust, and 4X increase in impulse. This study highlighted enhancements to thrust and impulse generated by porous silicon, identified trade-offs associated with simultaneous activation of multiple devices on a 1 cm2 chip, and showed energetic porous silicon as a viable solid propellant for propulsion of nano-satellites and micro-robots.Item Novel Integrated System Architecture for an Autonomous Jumping Micro-Robot(2010) Churaman, Wayne Anthony; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As the capability and complexity of robotic platforms continue to evolve from the macro to micro-scale, innovation of such systems is driven by the notion that a robot must be able to sense, think, and act [1]. The traditional architecture of a robotic platform consists of a structural layer upon which, actuators, controls, power, and communication modules are integrated for optimal system performance. The structural layer, for many micro-scale platforms, has commonly been implemented using a silicon die, thus leading to robotic platforms referred to as "walking chips" [2]. In this thesis, the first-ever jumping microrobotic platform is demonstrated using a hybrid integration approach to assemble on-board sensing and power directly onto a polymer chassis. The microrobot detects a change in light intensity and ignites 0.21mg of integrated nanoporous energetic silicon, resulting in 246µJ of kinetic energy and a vertical jump height of 8cm.Item Application of porous silicon in terahertz technology(2010) Lo, Shu-Zee Alencious; Murphy, Thomas E; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis, we discuss our efforts in developing porous silicon based devices for terahertz signal processing. In the first stage of our research, we demonstrate that porous silicon samples fabricated from highly doped p-type silicon can have adjustable refractive indices ranging from 1.5-2.1 and can exhibit a resistivity that is four orders of magnitude higher than that of the silicon wafer from which they were made. We show that the porous silicon becomes stable and relatively lossless after thermal oxidation. The partially oxidized porous silicon is shown to exhibit a smooth absorption spectrum, with low absorption loss of <10 cm^-1 over the entire terahertz spectrum. As a proof of concept, we fabricated, for the first time, a porous silicon based multilayered Bragg filter with reflectance of 93% and full-width at half-maximum bandwidth of 0.26 THz. Compared with other multilayered filtering techniques, porous silicon has the advantage that it can be easily fabricated, and offers the possibility of forming multilayer and graded index structures for more advanced filters. The large surface area of nanoporous silicon makes it an especially attractive platform for applications in biochemical detection and diagnostics As part of our effort in developing terahertz waveguide for biosensing, we reported the world's first porous silicon based terahertz waveguide using the principle of surface plasmon polaritons. The effect of porous silicon film thickness on the propagation of surface plasmons is explained theoretically in this thesis and is found to be in good agreement with experimental results.