SnO2-Based Ultra-Flexible Humidity/Respiratory Sensor for Analysis of Human Breath

Moumita Deb, Mei Yu Chen, Po Yi Chang, Pin Hsuan Li, Ming Jen Chan, Ya Chung Tian, Ping Hung Yeh, Olivier Soppera*, Hsiao Wen Zan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Developing ultraflexible sensors using metal oxides is challenging due to the high-temperature annealing step in the fabrication process. Here, we demonstrate the ultraflexible relative humidity (RH) sensor on food plastic wrap by using 808 nm near-infrared (NIR) laser annealing for 1 min at a low temperature (26.2–40.8 °C). The wettability of plastic wraps coated with sol-gel solution is modulated to obtain uniform films. The surface morphology, local temperature, and electrical properties of the SnO2 resistor under NIR laser irradiation with a power of 16, 33, and 84 W/cm2 are investigated. The optimal device can detect wide-range RH from 15% to 70% with small incremental changes (0.1–2.2%). X-ray photoelectron spectroscopy reveals the relation between the surface binding condition and sensing response. Finally, the proposed sensor is attached onto the face mask to analyze the real-time human breath pattern in slow, normal, and fast modes, showing potential in wearable electronics or respiration monitoring.

Original languageEnglish
Article number81
Issue number1
StatePublished - Jan 2023


  • breath analysis
  • humidity sensor
  • NIR annealing
  • plastic wrap
  • SnO


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