Microbial nanowires for sustainable electronics

Microbial protein nanowires are emerging as an alternative to abiotic nanowires for electronics applications. Microbial nanowires are sustainably produced, robust, non-toxic, biodegradable and uniquely malleable to precision genetic tailoring, which can confer specific functionalities. At present, the microbial nanowires that seem most adaptable to electronics applications are curli fibres, electrically conductive pili (e-pili) and c-type cytochrome filaments. These nanowires are all highly resistant to conditions that denature most proteins. Editing of the genes encoding curli fibre and e-pili monomers has yielded nanowires with enhanced functions, including increased conductivity, improved sensor selectivity and sensitivity, metal-binding properties, increased surface attachment, and improved nanowire alignment. Such microbial nanowires are highly processable in the organic solvents required for some device fabrication methods and readily incorporated into polymers without loss of function. This Review describes promising electronic devices for sensing, electricity generation and neuromorphic memory that depend on microbial nanowire components and discusses preliminary evidence of the feasibility of other microbial nanowire applications such as transistors, optoelectronics and supercapacitors. Factors that affect the commercialization of microbial nanowire-based electronics are also considered.