Grain‐Boundary‐Induced Drastic Sensing Performance Enhancement of Polycrystalline‐Microwire Printed Gas Sensors

The development of materials with high efficiency and stable signal output in a bent state is important for flexible electronics. Grain boundaries provide lasting inspiration and a promising avenue for designing advanced functionalities using nanomaterials. Combining bulk defects in polycrystalline materials is shown to result in rich new electronic structures, catalytic activities, and mechanical properties for many applications. However, direct evidence that grain boundaries can create new physicochemical properties in flexible electronics is lacking. Here, a combination of bulk electrosensitive measurements, density functional theory calculations, and atomic force microscopy technology with quantitative nanomechanical mapping is used to show that grain boundaries in polycrystalline wires are more active and mechanically stable than single-crystalline wires for real-time detection of chemical analytes. The existence of a grain boundary improves the electronic and mechanical properties, which activate and stabilize materials, and allow new opportunities to design highly sensitive, flexible chemical sensors.