TY - JOUR
T1 - Environment-friendly surface acoustic wave humidity sensor with sodium alginate sensing layer
AU - Han, Y.C.
AU - Wu, W.
AU - Kong, X.Y.
AU - Li, J.S.
AU - Yang, X.
AU - Guo, Y. J.
AU - Fu, Yongqing
AU - Torun, Hamdi
AU - Xiang, Xia
AU - Tang, Yongliang
AU - Zu, Xiaotao
N1 - Funding information: This study was supported financially by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (Grant No. U1930205), Engineering Physics and Science Research Council of UK (EPSRC EP/P018998/1) , and International Exchange Grant (IEC/NSFC/201078) through Royal Society and the National Natural Science Foundation of China (NSFC), and Royal Academy of Engineering: Research Exchange between UK and China.
PY - 2022/6/1
Y1 - 2022/6/1
N2 - A low-cost and environment-friendly surface acoustic wave (SAW) humidity sensor was fabricated on a quartz substrate using sol-gel/spin-coated sodium alginate (SA) sensing layer. The sensing mechanism is based on the frequency shift of the SAW sensor caused by both mass loading and electrical loading, with the former being the dominant factor. The SA film prepared in this study is an environment-friendly material with a large number of hydroxyl and carboxylate groups, which easily adsorb and react with H2O molecules to form hydrogen bonds. These adsorbed H2O molecules lead to significantly enhanced mass loading and signal responses of the SAW sensor. Electrical loading effect is also generated due to the transfer of hydrogen ions in the H2O molecules, which alters the electrical resistance and results in changes of resonant frequencies of the SAW device. When the relative humidity (RH) is increased from 35% to 85%, the responses of the SAW sensor with 1 wt% SA are significantly decreased. Whereas in a low humidity environment (e.g., RH <35%), the responses of the sensor show a linear relationship with the change of humidity. The developed humidity sensor shows good short-term/long-term stabilities and a low temperature coefficient of frequency.
AB - A low-cost and environment-friendly surface acoustic wave (SAW) humidity sensor was fabricated on a quartz substrate using sol-gel/spin-coated sodium alginate (SA) sensing layer. The sensing mechanism is based on the frequency shift of the SAW sensor caused by both mass loading and electrical loading, with the former being the dominant factor. The SA film prepared in this study is an environment-friendly material with a large number of hydroxyl and carboxylate groups, which easily adsorb and react with H2O molecules to form hydrogen bonds. These adsorbed H2O molecules lead to significantly enhanced mass loading and signal responses of the SAW sensor. Electrical loading effect is also generated due to the transfer of hydrogen ions in the H2O molecules, which alters the electrical resistance and results in changes of resonant frequencies of the SAW device. When the relative humidity (RH) is increased from 35% to 85%, the responses of the SAW sensor with 1 wt% SA are significantly decreased. Whereas in a low humidity environment (e.g., RH <35%), the responses of the sensor show a linear relationship with the change of humidity. The developed humidity sensor shows good short-term/long-term stabilities and a low temperature coefficient of frequency.
KW - Surface acoustic wave, sensor
KW - Sodium alginate (SA)
KW - Humidity
UR - http://www.scopus.com/inward/record.url?scp=85127133726&partnerID=8YFLogxK
U2 - 10.1016/j.mne.2022.100127
DO - 10.1016/j.mne.2022.100127
M3 - Article
SN - 2590-0072
VL - 15
JO - Micro and Nano Engineering
JF - Micro and Nano Engineering
M1 - 100127
ER -