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

Abstract

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 these applications with a 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 with 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 sensing range of this artificial nose extends into the human olfactory threshold for H₂S. The sensor is operated under low voltage (1 V) and mild temperature (0–25 °C) with sensing stability for at least 2 weeks. Furthermore, this artificial nose is demonstrated to be promising for applications in noninvasive halitosis diagnosis and meat spoilage identification. Our work may inspire odorant sensor development with an artificial olfactory system for robotics and other specific applications.