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Investigation of Cantilever Resonance Applied to Potentiometric Sensing

Published online by Cambridge University Press:  01 February 2011

Goutam Koley  and
Lakshminarayanan Lakshmanan
Goutam Koley
Affiliation:
koley@engr.sc.edu, University of South Carolina, Electrical Engineering, 3A12 Swearingen Center, Columbia, SC, 29208, United States, 8037773469
Lakshminarayanan Lakshmanan
Affiliation:
lakshmal@mailbox.sc.edu, University of South Carolina, Electrical Engineering, 1B27 Swearingen Center, Columbia, SC, 29208, United States
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Abstract

We demonstrate a highly sensitive potentiometric gas sensor based on a resonating Si microcantilever. Using a scanning probe microscope based set up in non-contact mode, the microcantilever was made to oscillate at its resonance frequency with periodically changing amplitude, using simultaneous mechanical and electrical excitation sources. The variation of the oscillation amplitude was found to be extremely sensitive to changes in surface potential, and served as a linear indicator for surface work function changes caused by molecular adsorption. The microcantilever sensor was found to be able to detect changes in surface potential down to 50 microvolt, which is basically limited by the system noise. When applied to sensing hydrogen using platinum coated cantilevers, it was observed that the microcantilever sensor can detect 1000 ppm hydrogen with an estimated lower limit of the detection time of 70 ms, at a cantilever-ground electrode distance of ∼10 micron. Several parameters, such as ac signal amplitude, cantilever – reference electrode distance, quality factor, area, and spring constant of the cantilever, can be adjusted to significantly enhance the sensitivity, possibly by orders of magnitude. Excitation of the cantilever at subharmonic resonance frequencies was also performed to study possible parametric resonance effects. In this system it was possible to observe sub-harmonic resonance of order more than 50 (i.e. lower than one-fiftieth the resonance frequency).

Keywords

microelectro-mechanical (MEMS)sensorscanning probe microscopy (SPM)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 951: Symposium E – Nanofunctional Materials, Nanostructures and Novel Devices for Biological and Chemical Detection , 2006 , 0951-E05-03
Copyright
Copyright © Materials Research Society 2007

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References

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