Browsing by Subject "Microscale"

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Analytical and experimental investigation of capillary forces induced by nanopillars for thermal management applications
(2010-05) Zhang, Conan; Hidrovo, Carlos H.
This thesis presents an analytical and experimental investigation into the capillary wicking limitation of an array of pillars. Commercial and nanopillar wicks are examined experimentally to assess the effects of micro and nanoscale capillary forces. By exerting a progressively higher heat flux on the wick, a maximum achievable mass flow was observed at the capillary limit. Through the balance of capillary and viscous forces, an ab initio analytical model is also presented to support the experimental data. Comparison of the capillary limit predicted by the analytical model and actual limit observed in experimental results are presented for three baseline wicks and two nanowicks.
Integrated fabrication of micro- and nano-scale structures for silicon devices enabled by metal-assisted chemical etch
(2021-08-05) Lema Galindo, Raul Marcel; Sreenivasan, S. V.; Ekerdt, John G
Silicon device manufacturing, at both the micro and nanoscales, is largely performed using plasma etching techniques such as Reactive Ion Etching. Deep Reactive Ion Etching (DRIE) can be used to create high-aspect ratio nanostructures in silicon. The DRIE process suffers from low throughput, only one wafer can be processed at a time; high cost, the necessary tools and facilities for implementation are expensive; and surface defects such as sidewall taper and scalloping as a consequence of the cycling process required for high-aspect-ratio manufacturing. A potential solution to these issues consists of implementing wet-etching techniques, which do not require expensive equipment and can be implemented at a batch scale. Metal Assisted Chemical Etch is a wet-etch process that uses a metal catalyst to mediate silicon oxidation and removal in a diffusion-based process. This process has been demonstrated to work for both micro and nanoscale feature manufacturing on silicon substrates. To date, however, a single study aimed at identifying experimental conditions for successful multi-scale (integrated micro- and nanoscale) manufacturing is lacking in the literature. This mixed micro-nanoscale etching process (IMN-MACE) can enable a wide variety of applications including, for example, development of point-of-care medical diagnostic devices which rely on micro- and nano-fluidic sample processing, a growing field in the area of preventive medicine. This work developed multi-scale MACE by a systematic experimental exploration of the process space. A total of 54 experiments were performed to study the effects of the following process parameters: (i) surface silicon dioxide, (ii) metal catalyst stack, (iii) etchant solution concentration, and (iv) pre-etch sample preparation. Of these 54 experiments, 18 experiments were based on exploring nanopatterning of 100nm pillars, and the remaining 36 explored the fabrication of micropillars with a diameter between 10µm and 50µm in 5µm increments. It was determined that a single catalyst stack consisting of ~3nm Ag underneath a ~15nm Au metal layer can be used to etch high quality features at both the micro and nanoscales on a silicon substrate pre-treated with hydrogen fluoride to remove the native oxide layer from the surface. Future steps for micro-nano scale integration were also proposed.