A Flexible Humidity Sensor Using Candle Soot as Sensitive Material

In this work, a flexible humidity sensor using hydrophilic candle-soot as its humidity sensitive material is proposed. The sensor is prepared simply by flame deposition of a candle-soot layer, oxygen-plasma treating of the layer surface and electrode wrapping at two ends of the device. Within a relative humidity range from 30 to 95%RH, such a sensor is able to achieve sensitivity of 4.32 MΩ/%RH and a response time of 0.5 s. Besides, no distinct deterioration in performance is observed when the sensor is bent upward and downward to a large degree, implying applicability of the sensor on irregular surfaces. It is expected that such a flexible humidity sensor has potential utilization in cosmetic moisture testing, wound healing monitoring and respiratory humidity detecting.