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Journal of Micro/Nanolithography, MEMS, and MOEMS • Open Access

High-performance extended gate field-effect-transistor-based dissolved carbon dioxide sensing system with a packaged microreference electrode
Author(s): Chia-Hsu Hsieh; Wei-Che Hung; Po-Han Chen; I-Yu Huang

Paper Abstract

We have developed an extended gate field-effect-transistor (EGFET)-based carbon dioxide (CO2) sensing system with a packaged Ti/Ag/AgCl/KCl-gel microreference electrode using microelectro-mechanical systems (MEMS) technology. The total dimensions of the proposed CO2 sensing system are only 2.8×1.5×0.1  cm, which is approximately 30 times smaller than a conventional CO2 sensing system (including the commercial Ag/AgCl RE). All of the manufacturing processes adopted in this work are compatible with standard planar technology and are very suitable for mass production. The presented planar reference electrode shows a very small offset voltage (−3.0  mV) and a very small potential drift (2.5 mV in 30,000 s) that is approximately equal to that of the commercial Ag/AgCl RE (1.6 mV in 30,000 s). Additionally, the implemented EGFET-based CO2 microsensor with a coated CO2 solid electrolyte and gas permeable membranes on the gate sensing area demonstrates a very high sensitivity (44.4  mV/decade) and very high sensing linearity (98.37%), while sensing CO2 concentrations ranging from 0.25 to 50 mM. Furthermore, a very small hysteresis voltage (7.5 mV) was obtained during the sensing cycle of 2.5–5–25–50–25–5–2.5 mM; this result was achieved by improving the surface planarization and enlarging the sensing area of the EGFET to 1  mm2.

Paper Details

Date Published: 19 September 2014
PDF: 8 pages
J. Micro/Nanolith. 13(3) 033017 doi: 10.1117/1.JMM.13.3.033017
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 13, Issue 3
Show Author Affiliations
Chia-Hsu Hsieh, National Sun Yat-Sen Univ. (Taiwan)
Wei-Che Hung, National Sun Yat-Sen Univ. (Taiwan)
Po-Han Chen, National Sun Yat-Sen Univ. (Taiwan)
I-Yu Huang, National Sun Yat-Sen Univ. (Taiwan)

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