Branched Nanowire Architectures for Compact Power Sources

Abstract : Efficient compact power sources are critical to future mobile technologies, yet limitations with existing sources have restricted development. The objective of this research is to exploit advances in nanoscience to enable new capabilities in compact biofuel cells. The research program has focused on (i) controlled synthesis and characterization of nanowire building blocks that can function as probes of fundamental biofuel cell processes, (ii) development of novel methods for hierarchical assembly of these nanoscale structures to enable studies of power scaling, and (iii) development and fabrication of new nanoscale electrodes enabling studies of microbial fuel cells down to the level of single bacteria. First, methods for the predictable and controlled synthesis of branched nanowires consisting of single crystal silicon backbones with metal nanowire branches have been developed. Nanocluster catalyzed growth was used to control the diameter and dopant concentration of silicon nanowire backbones, and metal branches were prepared using a novel nanocluster seeded solution phase growth. Second, an approach for large area, uniformly aligned and controlled density nanowire and nanotube films that involves expanding a bubble from a homogeneous suspension of these materials was developed. The blown-bubble films allow the unique properties of nanowires and to be exploited in applications that require large surface areas. Third, nanofabrication was used to define electrode arrays in which the exposed electrode area of individual elements was designed to limit interactions specifically with one or more bacterial cell and fabrication of optically transparent electrode arrays was carried out on transparent substrates to enable in-situ imaging of individual cells during electrochemical measurements. Results advance significantly our fundamental knowledge of branched nanoscale building blocks.