Flexible and ion-conductive hydrogel as an artificial nose for odorous H2S detection

Discriminative and sensitive detection of low-concentration odorous gases is of great significance for health diagnostics, product quality control and robotics. However, achieving a biomimetic olfactory system in those applications with hydrogel remains a challenge. Here, by learning the mechanism of human olfactory epithelium, we design a flexible and ion-conductive hydrogel based on cellulose as an artificial nose. The hydrogel is soft, flexible, adhesive, self-healing and conductive, enabling the integration to various devices. The artificial nose exhibits high selectivity to H2S over other gas molecules such as NH3, NO2, CO2, CH3CH2OH, CH2O, etc. It has high linear sensitivity (0.34 ppm-1) with a fast response (143 s). More importantly, the sensoring range of this artificial nose moves into human olfactory threshold of H2S. The sensor is operated under low voltage (1 V) and mild temperature (0-25 °C) with sensoring stability for at least 2 weeks. Furthermore, this artificial nose are demonstrated as promising in applications of noninvasive halitosis diagnosis and meat spoilage identification. Our work may inspire odorant sensor development with artificial olfactory system for robotics and other specific applications.