Fig. 4: Transient response of the RuO2-functionalized sensor to ethanol concentrations from ppm to ppb levels.

a Transient response of the fabricated sensor upon exposure to ethanol, ranging from 10 to 1 ppm, and b ranging from 20 ppb to 5 ppb. The resistance measured in air (Rair) for calculating the sensor response was 1.07 MΩ. The response was measured using the microheater-integrated sensor positioned in a quartz tube under room temperature. The average operating temperature of the micro heater was 290 °C