High Speed Chemical Sensing Using Microdischarges

Bhaskar Mitra, Graduate Student, University of Michigan
In our recent work, we have used emission spectroscopy on miniaturized microplasmas for the detection of vapors and gases in air. Unlike other chemical sensing methods, the detection is based on atomic structure of the chemical agent rather than chemical property. This makes it possible to detect a wide variety of chemicals, including inert gases. Some relevant aspects of d.c microplasmas are discussed. D.C Microplasmas differ significantly from their macroscale counterparts, as they are powered by secondary emission from the cathode, rather than avalanche multiplication in the gas. This offers certain unique advantages for sensing applications. The application of pulsed microdischarges to vapor sensing is explored by examining the afterglow of the discharge. It is seen that the pulsed microplasma differs significantly from the d.c discharge, as it is seen to have a significant afterglow. This afterglow is important to sensing applications; certain species are more prominent in the afterglow due to the way the excited states are formed. The powering aspects of pulsed microplasmas are explored using three electrode discharges. These discharges make it possible to discharge extremely low power (down to 4 uJ) per pulse to make these devices suitable for low power applications.
Bhaskar Mitra was born in Jaipur, India in 1979. He recieved his B.Tech and M.Tech in Electrical Engineering from the Indian Institute of Technology, Bombay, in 2002. As part of his masters thesis, he built a microsystem for single cell electroporation. Such a system is used to inject a large population of cells with drugs or genetic material one cell at a time. Since January 2003, he has been in the Ph.D program in the EECS department at the University of Michigan. He is currently working on microplasmas, microdischarges and their applications under the guidance of Prof. Yogesh Gianchandani.