Micromachined Particle Filter With Low Power Dissipation

Abstract

Microfilters for collecting micron-size airborne biological agents are designed and fabricated using a micro-electro-mechanical-system (MEMS) fabrication technology. The thickness of the microfilter ranges from 1 μm–3 μm, and the hole diameter from 5 μm–12 μm. Iterations between experimental and numerical studies are carried out to attain efficient microfilter designs with low pressure drop. Two orders of magnitude reduction of viscous power consumption have been achieved. A design rule of the filter in a low Reynolds-number range was first derived from numerical simulations. Highly accurate measurements of the three-dimensional (3-D) geometry, side-wall profile, and diameter of the micron-size holes are critical in validating and modifying the design rule. The effect of the surface slip is found to be small in the tested Knudsen-number range.

Monodisperse, Polymeric Nano‐ and Microsieves Produced with Interference Holography

“…Poiseuille's equation for circular channels [15] is the simplest approximation, but it is inaccurate for small length scales and does not take into account entrance effects. Better descriptions are given by Dagan, [16] Tio & Sadhal, [17] Yang, [18] and Van Rijn. [19] The latter gives the best agreement with the real flow behavior of monodisperse microsieves with the dimensions dealt with in this study:…”

Pressure Drop for Low Reynolds-Number Flows Through Regular and Random Screens

“…Courtesy of Springer-Verlag (Comstock and Côté 1968) Karlsson 2000;Laakkonen 2003), and many filtering processes. Very recently applications which involve the use of microfilters have also appeared (Yang et al 2001). There are also many biological systems which involve fluid flow through thin net-like structures.…”

Rarefaction, Compressibility, and Viscous Heating in Gas Microfilters

“…The side-wall geometry is shown to affect the overall pressure drop across the micro lter devices. 3 Empirical formulas for pressure drop in conventional lters have been obtained previously. 11;12 However these scaling laws are valid for high-Reynolds-number ows (Re À 100), and they can not be applied to micro lters.…”

“…11;12 However these scaling laws are valid for high-Reynolds-number ows (Re À 100), and they can not be applied to micro lters. 3 The initial work on micro lters is by Kittilsland et al, 13 who fabricated a lter that consisted of two silicon membranes with holes. By changing the membrane separation distance, they were able to build lters for separation of particles as small as 50 nm.…”