Multifunctional Protein Nanowire Humidity Sensors for Green Wearable Electronics

Abstract Sustainably produced biomaterials can greatly improve the biocompatibility of wearable sensor technologies while reducing the energy and environmental impacts of materials fabrication and disposal. An electronic sensor device in which the sensing element is a thin (≈2 µm) film of electrically conductive protein nanowires harvested from the microbe Geobacter sulfurreducens is developed. The sensor rapidly responds to changes in humidity with high selectivity and sensitivity. The sensor is integrated on a flexible substrate as a wearable device, enabling real‐time monitoring of physiological conditions such as respiration and skin hydration. Noncontact body tracking is demonstrated with an array of sensors that detect a humidity gradient at distance from the skin with high sensitivity. Humidity gradients induce directional charge transport in the protein nanowires films, enabling the production of a current signal without applying an external voltage bias for powerless sensing. These results demonstrate the considerable promise for developing protein nanowire‐based wearable sensor devices.