Measurement of the Mass Flow and Tangential Momentum Accommodation Coefficient in Silicon Micromachined Channels
An analytic and experimental investigation into gaseous flow with slight rarefaction through long microchannels is undertaken in an attempt to obtain values of the Tangential Momentum Accommodation Coefficient (TMAC) for a common MicroElectroMechanical Systems (MEMS) surface. A set of analytic e...
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| Format: | Technical Report |
| Language: | en_US |
| Published: |
Aerospace Computational Design Laboratory, Dept. of Aeronautics & Astronautics, Massachusetts Institute of Technology
2010
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| Online Access: | http://hdl.handle.net/1721.1/57611 |
| Summary: | An analytic and experimental investigation into gaseous
flow with slight rarefaction through long microchannels
is undertaken in an attempt to obtain values of the Tangential Momentum Accommodation Coefficient
(TMAC) for a common MicroElectroMechanical Systems (MEMS) surface. A set of analytic expressions is
developed from the slip-
flow solutions of the Navier Stokes equations which can be used to interpret the
results of
flow in micromachined channels and to extract TMAC values from these results. In addition
to the theoretical framework, a robust microchannel fabrication procedure and a dedicated high-resolution
mass
flow measurement technique is developed. These are used in conjunction to obtain TMAC values for
single-crystal silicon upon which a native oxide resides for gas
flows of argon, nitrogen and carbon dioxide.
It is shown that the TMAC for this common MEMS surface can possess a value less than unity (0.75-0.85)
for the conditions which are expected to be encountered with state-of-the-art MEMS. |
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