Ultrasensitive flexible self-powered ammonia sensor based on triboelectric nanogenerator at room temperature

An ultrasensitive self-powered ammonia (NH3) sensing system based on a vertical contact-separate mode triboelectric nanogenerator (TENG) has been proposed for room temperature detection of NH3 concentrations both in the ambient environment and in human exhaled gases. Owing to the special output characteristics of the TENG adjusted by the load resistance of the NH3 sensor, output voltage of the fabricated gas sensor has a proportional relationship with NH3 concentration, which is the fundamental working mechanism of the self-powered gas-sensing system. The triboelectric ammonia sensor (TEAS) based on PANI-MWCNTs composite thin film possesses a NH3-sensing response of 10% at 0.01 ppm NH3 and exhibits a great response of 255% at 100 ppm NH3. Meanwhile, the TEAS also holds fast response/recovery time (89-120 s/103-127 s for 0.6-100 ppm NH3), excellent long-term stability, satisfactory selectivity and good anti-bending ability. Furthermore, a preliminary test of human exhaled NH3 concentration has been carried out to further expand the practical application of the developed TEAS. The results not only provide an effective technique in ultrasensitive NH3 sensing but also greatly broaden the applicability of TENG in the detection of human kidney health through comparing to average NH3 concentrations within exhaled gases of healthy people.