Simultaneous and wireless measurement of CO2 and humidity using a SAW reflective delay line

Chunbae Lim; Wen Wang; Keekeun Lee; Hae-Kwan Oh; Sangsik Yang

doi:10.1117/12.809994

23 February 2009 Simultaneous and wireless measurement of CO₂ and humidity using a SAW reflective delay line

Chunbae Lim, Wen Wang, Keekeun Lee, Hae-Kwan Oh, Sangsik Yang

Proceedings Volume 7207, Microfluidics, BioMEMS, and Medical Microsystems VII; 72070W (2009) https://doi.org/10.1117/12.809994
Event: SPIE MOEMS-MEMS: Micro- and Nanofabrication, 2009, San Jose, California, United States

Abstract

A 440MHz wireless and passive surface acoustic wave (SAW) based chemical sensor was developed for simultaneous measurement of CO₂ gas and relative humidity (RH) using a reflective delay line pattern as the sensor element. The reflective delay line was structured by an inter-digital transducer (IDT) and several shorted grating reflectors positioned both sites of the IDTs along the SAW propagation direction. A Teflon AF 2400 film with large solubility, permeability, and selectivity towards to CO₂ and a hydrophilic SiO₂ layer for water vapor sensing are used as the sensitive film and deposited onto the piezoelectric substrate. A simulation on the SAW device was performed using the coupling of modes (COM). The measured reflection coefficient S₁₁ in time domain of the fabricated SAW device shows sharp reflection peaks with high signal-to-noise (S/N) ratio, small signal attenuation, and few spurious peaks. During the CO₂ and humidity testing, high sensitivity (~2^o ppm^-1 for CO₂ detection and 7.45^o/%RH for humidity sensing), good linearity and repeatability were observed in the CO₂ concentration of 50~400ppm and humidity of 20~80%RH. Temperature and humidity compensations were also investigated during the sensitivity evaluation process.

Citation Download Citation

Chunbae Lim, Wen Wang, Keekeun Lee, Hae-Kwan Oh, and Sangsik Yang "Simultaneous and wireless measurement of CO₂ and humidity using a SAW reflective delay line", Proc. SPIE 7207, Microfluidics, BioMEMS, and Medical Microsystems VII, 72070W (23 February 2009); https://doi.org/10.1117/12.809994

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available