Micromechanical Resonators with Nanoporous Materials for Enhanced Vapor Sensing
Dec 03, 2012
from 10:00 AM to 12:00 PM
|Where||Faraday Room, 67-124 Engr IV|
|Contact Name||Yong Ha Hwang|
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Resonant sensors can detect chemical and biological analytes by measuring shifts in the resonant frequency due to adsorption-induced mass changes. This talk describes a sensing approach that provides the sensitivity of nanoscale devices without sacrificing capture area through the use of highly porous surface so as to increase the adsorbed mass. Three strategies are studied to achieve high sensitivity gas sensors; (1) porous-etched silicon resonator, (2) ZIF (zeolitic imidazolate framework)-agglomerated resonator by drop casting, and (3) ZIF-coupled resonator by dielectrophoresis.
Microscale silicon resonators with nanoscale pores are developed for increased surface area. Partially-porous silicon resonators and receptor-coated partially-porous silicon resonators are improved up to 165% and 654% in resonator sensitivity, respectively, as compared to nonporous silicon resonators.
This talk also presents ZIF-coupled agglomerated resonators whose sensitivity shows an improvement up to 78 times (780% improvement) over the silicon resonators with identical dimensions while additionally utilizing the inherently selective adsorption properties of ZIFs. ZIF nanoparticles provide previously unattainable surface area as well as the ability to tailor crystal structure for inherent selectivity. A unique fabrication technique in combination with drop casting method is presented.
Lastly, ZIF nanoparticles are coupled to resonators using dielectrophoresis (DEP) to maximize adsorption of ZIFs so as to gain further sensitivity enhancement. By utilizing an inherently sensitive and selective adsorption property of ZIFs, amplitude of frequency shift shows a sensitivity improvement up to 158 times over the silicon resonator. Also, consistent decay constant of the frequency shift provide significant chemical recognition ability of the ZIF-coupled resonant sensor.
Yong Ha Hwang is a Ph.D. candidate in Sensors and Technology Laboratory, Electrical Engineering Department, UCLA. He received both the B.S. and M.S. degrees from Electrical Engineering Department in Korea University, Seoul, Korea. His research interests include design, fabrication and characterization of nano- and microelectromechanical systems for sensing applications.