A Water Spectroscopy Microsystem with Integrated Discharge Source, Dispersion Optics, and Sample Del
Post Doctorate Research Fellow
University of Michigan
In this talk, I will describe a microsystem integrating the fluidic, electrical and optical elements required for field-portable water-chemistry testing by electric discharge spectroscopy. The device utilizes a DC microdischarge as a spectroscopic source. The discharge is created by applying a DC voltage between a metal anode and uses the water sample as the cathode. Impurities are sputtered from the water sample into the microdischarge. A blazed grating is used as the dispersion element, along with an aperture fabricated on a glass substrate. The microsystem is assembled and used with a CCD sensing element to distinguish atomic spectra. Two versions of the microsystem have been implemented: planar and a capillary tube-based device. Our current system does not utilize collimation optics; we explore the possibility of using simplified optics, and evaluate the compromises in resolution.
Detection of Cr and other chemicals in water samples has been successfully demonstrated with both devices. Experiments find that the angular resolution (?q/?l) of the whole system is reduced to approximately 0.10 rad/ µm from theoretical 0.22 rad/ µm for both planar and capillary version devices since the microdischarge source is un-collimated and not a point source. However, the Cr and Na contaminants in the water and N2 spectra still can be detected readily, indicating sufficient angular resolution to allow critical spectra (Cr, Na and N2) to be distinguished. If necessary collimating optics are integrated, the separation between the grating and the camera can be scaled down to 1.5 cm for 8 µm pixel spacing on the image plane.
Long Que received his undergraduate and graduate education in physics and communication engineering in Peking University, Beijing, China. He received his Ph. D degree in electrical engineering from University of Wisconsin-Madison in 2000. He held various positions in industry, research institute and university. Currently he is a visiting scientist at EECS Department at University of Michigan at Ann Arbor. His general research interests are in BioMEMS, optical/RF MEMS, and Nanotechnology. His current research includes: miniaturized system for chemical sensing and for biochemical (DNA and protein) fluorescence imaging; RF CPW-transmission line integrating bistable switch with MilliNewton latching force; and ultrafast optics pulse shaping and sensing utilizing bistable MEMS platform.
He has published about 20 papers in journals and conferences and co-authored a chapter in a book entitled Micro-Opto-Electro-Mechanical System (in press). He has been awarded three US patents and another four patents are pending.