Laser-localized hydrothermal synthesis of flexible ZnO gas sensor for room-temperature detection of nitrogen dioxide

In this work, a flexible ZnO-based gas sensor is developed for room-temperature detection of nitrogen oxide (NO2). The sensor is fabricated on polyimide (PI) substrate by highly efficient and scalable laser micro-processing techniques, including laser direct writing of carbonized electrode on PI and laser-localized hydrothermal synthesis of ZnO on the electrode. The gas sensing characteristics of the device, such as response, stability, and repeatability, are systematically investigated. The ZnO-based sensor shows a response of 0.71% for NO2 in room temperature, a good stability (30 days), and repeatability with the substrate curvatures bent from 22.34 to 4.16 mm in 1000 ppm NO2 at room temperature (25 °C). Unlike the traditional ZnO-based gas sensor, the device we made presents the characteristics of p-type semiconductor through gas sensing tests, which could be attributed to the possible doping of C and low performing temperature.