CBE10_Chang_Lecture

CBE10_Chang_Lecture - Challenges of Transport Phenomena in...

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1 Challenges of Transport Phenomena in Research and Education Miniaturized and Integrated Sensors and Microsystems Jane P. Chang April 17, 2007 Chemical and Biomolecular Engineering Department University of California, Los Angeles 2 • Background and Societal Impact – Detection of harmful species at low concentrations • Chemical and biological warfare agents • Selectivity (w/ separation) • Sensitivity, stability, speed • Distributed sensor network (with RF MEMS) – Societal impact • Civilian and environmental safety • Total chemical processing on a chip • Chemical synthesis and energy systems
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3 • Lab-on-a-chip – From unit operation to systems – From single unit to network Chemically Selective Separation Sample Collection Valve Pump Valve Gas Flow Control Chemically Selective Detection Separation Sample Collection / Concentration Standard reference Micro-hot plate preconcentrator (μPC) Micro-gas chromatograph column (μGC) Micro-thermal conductivity detector ( µ TCD) µ CIT Center for Embedded Networked Sensing, UCLA Æ Low power consumption 4 Technical Principles – Thermal • Heat flow, heat content, pyroelectric, calorimetric – Mechanical • Weight, size, shape – Electrochemical • Ions, amperometry, potentiometry, pH, conductimetry – Optical • Absorption, emission, reflection – Magnetic • Paramagnetism, Hall effect, field strength, field direction – Electronic • Voltage, current, impedance Integration Challenges – Versatile platforms that offer complementary sensing capabilities at reduced dimensions
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5 • State-of-the-Art – Microfluidics • Dimensionless scaling parameters for design and characterization – Micro gas chromatography • Fast separation of large number of species, with over 10,000 theoretical plates – Micro mass analyzer • Micro-scaled devices with proven efficiency – Chemical sensor with micro plasmas • Battery operated device with high sensitivity 0 1 02 03 04 05 06 07 0 -100 -50 0 50 100 150 200 ion signal subtracted baseline e - gate of e - gate on RF of RF on Signal (nA) time ( µ sec) 6 * Courtesy of H.A. Stone, School of Engineering & Applied Sciences, Harvard University • Complex fluids – From microfluidics with multiphase flows to wetting of rough surfaces (final equilibrium shape; 4 different liquids)
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7 * Courtesy of T. G. Mason, Chemistry and Biochemistry Department, UCLA • Controlled folding of a viscous thread in Microfluidic Channels Silicon-based microchannel Silicone oils: 0.5 < η < 1000 cP Refractive index: 1.375< n <1.453 Gravity Capillary ρ < 2 2 F = 10 gh U γ →∞ 0 Ca = U Peclet Viscosity ratio Flow rate ratio << 36 Pe = , 10 Pe 10 hU D χχ = 1 2 , 10 < < 2000 ϕϕ =< 1 2 , 0.01 < 1 Q Q Reynolds < Re = 50 hU Dimensionless Groups: “Subfolding and Chaotic Folding” “Simple Viscous Folding” χ = 83 η 1 = 500 cP η 2 = 6 cP χ = 1000 η 1 = 500 cP η 2 = 0.5 cP 8 • Application in chemical processing and materials synthesis Æ From passive detection to active point-of-use treatment/abatement
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9 F. Leipold et al., J. Phys. D 33 , 2268 (2000).
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CBE10_Chang_Lecture - Challenges of Transport Phenomena in...

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