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Unformatted text preview: U n c o r r e c t e d P r o o f 2 7- 1 2- 1 4 i Dongqing Li: Encyclopedia of Micro- and Nano-Fluidics — Entry 202 — 2007/12/14 — 17:18 — page 1 — LE-T E X i i i Micro- and Nanoscale Anemometry: Implication for Biomedical Applications 1 Micro- and Nanoscale Anemometry: Implication for Biomedical Applications MAHSA ROUHANIZADEH, HONGYU YU, LISONG AI, 1 JENNIFER XU, TZUNG K. HSIAI 2 Department of Biomedical Engineering & Cardiovascular 3 Medicine, School of Engineering & School of Medicine, 4 University of Southern California, Los Angles, TS3 USA 5 [email protected] 6 Synonyms 7 Thermal flow sensors 8 Definition 9 Hot-wire anemometers have been developed for a wide 10 spectrum of applications from experimental fluid mechan- 11 ics to aerospace engineering to measure physical parame- 12 ters such as temperature, flow rates, and shear stress. The 13 advent of microelectromechanical systems (MEMS) and 14 nanoscale thermal sensors has provided an entry point to 15 microfluidics, biomedical sciences, and micro-circulation 16 in cardiovascular medicine. These MEMS and nanoscale 17 devices are fabricated with semiconductor-based sensing 18 elements which harbor the physical property of a resistor 19 and have the dimension of one-tenth of a strand of hair. 20 On the basis of the heat transfer principle, these resistant 21 elements are heated by the Joule effect due to the passage 22 of electric current. As the air or fluid flows past their sur- 23 faces, the decrease in temperature alters the resistance of 24 the sensing elements, from which physical parameters can 25 be obtained. 26 Overview 27 The concept of hot-wire or hot-film anemometry was first 28 conceived in the early 1900s . Due to the technical 29 difficulty in developing and testing hot-wire anemome- 30 ters, published experimental data have remained scarce. 31 Boussinesq was one of the first to have validated the the- 32 ory of hot-wire anemometry , followed by other inves- 33 tigators, including Ziegler  TS4 who was the first to 34 develop the constant-temperature anemometer to enhance 35 the sensitivity. Later, King designed hot-wire anemome- 36 ters coupled with the theory of heat convection using cylin- 37 ders immersed in a fluid flow . Recently, Ho and co- 38 workers  as well as Sheplak et al.  have developed 39 MEMS thermal sensors for aerospace applications. Over- 40 all, these investigators have contributed to the basics of 41 hot-wire anemometry for biomedical and clinical appli- 42 cations [6–8]. By virtue of their high temporal and spa- 43 Micro- and Nanoscale Anemometry: Implication for Biomedical Appli- cations, Figure 1 ( a ) Conventional hot-wire anemometry. The arrows indicate the thin hot wires connected to the electrodes with both ends....
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This note was uploaded on 02/15/2012 for the course BIO 551 taught by Professor Hsai during the Spring '12 term at USC.
- Spring '12