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Summary: Dual-Mode Piezo-on-Silicon Resonant Temperature
and Humidity Sensor for Portable Air Quality
Monitoring Systems
Jenna L. Fu and Farrokh Ayazi
School of Electrical and Computer Engineering
Georgia Institute of Technology
Atlanta, GA, USA
jenna.fu@gatech.edu
Abstract--This paper demonstrates a dual-mode,
micromachined temperature and relative humidity (RH) sensor
platform using two ZnO-on-silicon, lateral-mode bulk acoustic
wave (BAW) resonators. A moisture-insensitive reference
resonator is utilized in conjunction with an identical, humidity-
functionalized resonator to yield a thermally compensated RH
sensor. The reference sensor exploits the dual-mode response of
fundamental and higher order in-plane resonance modes in the
range of 30-100 MHz to eliminate the RH sensor dependence on
temperature. Hygroscopic polyethyleneimine (PEI) is deposited
on annexed sensing platforms of the BAW resonator to enable
operation from 20 to 92 %RH with high Q in air. A humidity
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