Mr. William G. Gardner Profile

William G. Gardner

at Duke Univ

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Publications (2)

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Proceedings Article | 26 October 2010 Paper

Fabrication of a mechanically aligned single-wafer MEMS turbine with turbocharger

S. Pelekies, T. Schuhmann, W. Gardner, A. Camacho, J. Protz

Proceedings Volume 7833, 783306 (2010) https://doi.org/10.1117/12.862729

KEYWORDS: Oxides, Semiconducting wafers, Etching, Optical alignment, Deep reactive ion etching, Microelectromechanical systems, Silicon, Plasma enhanced chemical vapor deposition, Wafer bonding, Photomasks

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We describe the fabrication of a turbocharged, microelectromechanical system (MEMS) turbine. The turbine will be part of a standalone power unit and includes extra layers to connect the turbine to a generator. The project goal is to demonstrate the successful combination of several features, namely: silicon fusion bonding (SFB), a micro turbocharger [2], two rotors, mechanical alignment between two wafers [1], and the use of only one 5" silicon wafer. The dimension of the actual turbine casing will be 14mm. The turbine rotor will have a diameter of 8mm. Given these dimensions, MEMS processes are an adequate way to fabricate the device, but it will be necessary to stack up seven different layers to build the turbine, as it is not possible to construct it out of one thick wafer. SFB will be used for bonding because it permits the great precision necessary for high quality alignment. Yet a more precise alignment will be necessary between the layers that contain the turbine rotor, to decrease imbalance and guarantee operation at a very high rpm. To achieve these tight tolerances, a mechanical alignment feature announced by Liudi Jiang [1] is used. The alignment accuracy is expected to be around 200nm. Despite the fact that the turbine consists of multiple layers, it will be fabricated on only one silicon-on-insulator (SOI) wafer. As a result, all layers are exposed to the same process flow. The fabrication process includes MEMS technology as photolithography, nine deep reactive ion etching (DRIE) steps, and six SFB operations. A total of 14 masks are necessary for the fabrication.

Proceedings Article | 5 May 2010 Paper

Microscale ethanol vapor ejector and injector

William Gardner, Ivan Wang, Natalya Brikner, Justin Jaworski, Jonathan Protz

Proceedings Volume 7679, 76792P (2010) https://doi.org/10.1117/12.858797

KEYWORDS: Bioalcohols, Liquids, Throat, Rockets, Microfabrication, Deep reactive ion etching, Microelectromechanical systems, Scanning electron microscopy, Manufacturing, Finite element methods

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Two non-rotating pumping components, a jet ejector and injector, were designed and tested. Two jet ejectors were designed and tested to induce a suction draft using a supersonic micronozzle. Three-dimensional axisymmetric nozzles were microfabricated to produce throat diameters of 187 μm and 733 μm with design expansion ratios near 2.5:1. The motive nozzles achieved design mass flow efficiencies above 95% compared to isentropic calculations. Ethanol vapor was used to motivate and entrain ambient air. Experimental data indicate that the ejector can produce a sufficient suction draft to satisfy both microengine mass flow and power off-take requirements to enable its substitution for high speed microscale pumping turbomachinery. An ethanol vapor driven injector component was designed and tested to pressurize feed liquid ethanol. The injector was supplied with 2.70 atmosphere ethanol vapor and pumped liquid ethanol up to a total pressure of 3.02 atmospheres. Dynamic pressure at the exit of the injector was computed by measuring the displacement of a cantilevered beam placed over the outlet stream. The injector employed a three-dimensional axisymmetric nozzle with a throat diameter of 733 μm and a three-dimensional converging axisymmetric nozzle. The experimental data indicate that the injector can pump feed liquid into a pressurized boiler, enabling small scale liquid pumping without any moving parts. Microscale injectors could enable microscale engines and rockets to satisfy pumping and feedheating requirements without high speed microscale turbomachinery.

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