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.

Self-sustained green neuromorphic interfaces

“…Thus, the films (Supplementary Fig. 1) formed from the molecular protein nanowires are stable in ambient environment [17][18][19]36 . The protein nanowires can be protonated or deprotonated in solution environments 37 , which can modulate the wire-wire interaction and hence film solubility.…”

“…5). However, a quick change of local humidity as the result of breathing-induced non-uniform moisture adsorption 19 , resulting in an instant electric spike (Fig. 1h).…”

“…2b), in which the sensory signal was locally processed and converted into action potential (e.g., by an interneuron) before sending to the central nervous system for upper-level decision [9][10][11] . In this case, the interface can be used to perceive humidity level that is relevant to environmental and physiological conditions (e.g., hydration, wound state) 19 for an intelligent decision.…”

“…Second, devices fabricated with protein nanowires can harvest electric energy from environmental humidity 18 , sustaining signal and energy to computing. Third, protein nanowires can function as the sensing component in electronic sensors 19 . The biocomposition in the devices also represents an exploration for "green" electronics integrated from biomaterials that offer renewability, biocompatibility, and eco-friendliness 16 .…”

Strategies for Fabricating Protein Films for Biomaterial Applications

“…[ 94,95 ] Recently, wearable electronic devices have been developed using protein nanowire films for humidity sensing. [ 96 ] Composite materials of amyloid aggregates and graphene have exhibited shape memory and enzyme sensing properties. [ 97 ]…”