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TECHNICAL PAPERS

Micromachined Particle Filter With Low Power Dissipation

[+] Author and Article Information
Joon Mo Yang, Chih-Ming Ho

Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095

Xing Yang, Yu-Chong Tai

Electrical Engineering Department, California Institute of Technology, Pasadena, CA 91125

J. Fluids Eng 123(4), 899-908 (May 20, 2001) (10 pages) doi:10.1115/1.1399285 History: Received June 02, 2000; Revised May 20, 2001
Copyright © 2001 by ASME
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References

Figures

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Fabrication process for the membrane particle filters: (a) membrane (SiN) deposition (LPCVD), (b) KOH etching of Si wafer, (c) Hole patterning (RIE), (d) KOH etching of Si wafer, and (e) Parylene C deposition
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Measured pressure drop as a function of the inlet velocity for various microfilters. Each line represents second-order fitting curve. For dimensions of each microfilter, see Table 1. (Uncertainties ΔP=±2 percent, Uncertainties Uin=±3.5 percent).
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A nondimensionalized formula obtained from numerical calculations based on the calculation domain shown in Fig. 5. Some of the calculated results are shown as symbols: ○−d=12 μm, hexagonal, t=1 μm,β=45 percent,Δ−d=12 μm, circular, t=1 μm,β=45 percent,□−d=7.8 μm, hexagonal, t=3 μm,β=19 percent,x−d=8 μm, circular, t=3 μm,β=20 percent,⋄−d=4.8 μm, circular, t=3 μm,β=7 percent.
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Comparison of the measured and the calculated pressure drop and the effect of slip boundary condition (α=1.0): (a) Filter I, (b) Filter II, and (c) Filter III. (Uncertainties ΔP=±2 percent, Uncertainties Uin=±3.5 percent).
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A SEM picture of (a) a 1-μm-thick resolution grid, (b) a silicon nitride membrane, and (c) a Parylene coated membrane for measuring the thickness of the microfilter and the side-wall profile of the filtering hole
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Images taken for measuring the hole size of the microfilter: (a) a SEM picture of one hole and (b) an image of the filtering holes from WYKO surface profiler
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Probability density function (PDF) of the hole diameter obtained from the images using the WYKO surface profiler (davg=5.4 μm)
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Comparison of the calculated pressure drop with 0.5 μm error in the measurement of the hole diameter for (a) Filter I, (b) Filter II, and (c) Filter III. (Uncertainties ΔP=±2 percent. Uncertainties Uin=±3.5 percent).
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Side-wall profile of the filtering hole generated by the RIE process (a/b=0.5; dashed line is ideal case, solid line is real case)
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Computational domain determined from the SEM picture shown in Fig. 8 for (a) a silicon nitride membrane and (b) a Parylene coated membrane
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Comparison between the measured and the calculated pressure drop after the side-wall profile is taken into consideration for (a) Filter I, (b) Filter II, and (c) Filter III. (Uncertainties ΔP=±2 percent, Uncertainties Uin=±3.5 percent).
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A nondimensionalized formula, which is established based on the geometry shown in Fig. 13 and a comparison with the measured pressure drop. (Uncertainties Kβ2/[3.5(t/d)+3]=±7.8 percent, Uncertainties Uind/βν=±3.9 percent).
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Power required to sustain a desired flow rate as a function of the flow rate per unit area. See Table 1 for dimensions of each microfilter. Here, each line represents the curve fit of each data set. (Uncertainties Prequired=±6.4 percent, Uncertainties Uin=±3.5 percent).
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Comparison of the power requirement with the same particle threshold (5 μm) but different opening factors. See Table 1 for dimensions of each microfilter. Here, each line represents the curve fit of each data set. (Uncertainties Prequired=±6.4 percent, Uncertainties Uin=±3.5 percent).
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Photographs of the fabricated microfilters: (a) photograph of the entire microfilter, (b) filtering region with circular holes, (c) filtering region with hexagonal holes, and (d) filtering region with rectangular holes
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Geometrical factors in the microfilter: (a) front and (b) side views
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Calculation domain and boundary conditions for numerically predicting the pressure drop through the microfilter: (a) a 3-D domain, (b) a simplified axisymmetric domain 4, and (c) a magnified region around the hole

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