Microwave humidity sensor based on carbon dots-decorated MOF-derived porous Co3O4 for breath monitoring and finger moisture detection. (15th October 2021)

• Record Type: Journal Article
• Authors: Yu, He; Wang, Cong; Meng, Fanyi; Xiao, Jin; Liang, Junge; Kim, Hyunseok; Bae, Sanghoon; Zou, Danqing; Kim, Eun-Seong; Kim, Nam-Young; Zhao, Meng; Li, Baoqiang
• Is Part Of: Carbon. Volume 183(2021)
• Page Start: 578
• Page End: 589
• Publication Date: 2021-10-15
• Subjects: Microwave device -- Humidity sensor -- Carbon dots -- Integrated passive device technology -- Breath moisture detection; Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2021.07.031
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: This research investigates a microwave transduction-based humidity sensor that is a promising candidate for real-time clinical healthcare applications and green miniaturized wearable electronic devices. Optimization of sensing material, sensing platform, and device fabrication techniques produces a carbon dots (CDs)-decorated metal organic framework (MOF)-derived porous Co3 O4 (CDs-Co3 O4 ) microwave resonator-based sensor with excellent real-time humidity detection. Inspired by the water absorption component polyacrylamide in baby diapers, the acrylamide is adopted to synthesize CDs for microwave humidity sensor. Combining CDs with MOF-derived porous Co3 O4 enhances humidity sensitivity under microwave excitation, with a frequency shift of 3.40 MHz/% RH and a loss variation of 0.15 dB/% RH between 5% and 99% RH. These values are 49.7% (for frequency shift) and 20.5% (for return loss) higher than Co3 O4 sensor. Moreover, CDs-Co3 O4 exhibits high selectivity towards water vapor against other volatile organic compounds, and the response or recovery time are both less than 5 s. Fabricated by an integrated passive device technology, the sensing platform is miniaturized at 0.98 × 0.80 × 0.22 mm 3 with superb device stability and reliability. The CDs-Co3 O4 sensor remarkably monitors respiratory patterns of breathing or apnea, as well as subtle changes in the humidity levels of an approaching finger. A charge transfer process and microwave interactions are the mechanisms for improved humidity sensitivity. Graphical abstract: Image 1