Large scale and cost effective generation of 3D self-supporting oxide nanowire architectures by a top-down and bottom-up combined approach

Metal oxide nanowires are one of the most promising material systems utilized in energy conversion and storage devices. Directly synthesizing oxide nanowires on conductive substrates and assembling them into 3D self-supporting spatial architectures are of great importance for improving their performances. We propose and experimentally demonstrate a top-down and bottom-up combined manufacturing strategy, which can facilely fabricate various 3D self-supporting macro-micronano-nanowire multiscale architectures directly on bulk metal substrates. By employing micro-nano precursor structures, the gap between the commonly micrometer scale top-down and nanometer scale bottom-up approaches is bridged seamlessly. The presented strategy combines the advantages of the ultrafast laser direct writing approach in creating versatile micro patterns with those of the oxidation growth approach in creating elaborate nanowires. Both the precursor structures and the nanowires can be flexibly tuned in order to achieve arbitrary desired 3D architectures. Successfully pairing the scalable top-down laser direct writing technique with the high throughput bottom-up oxidation growth technique greatly improves the potential of our strategy in mass production and widespread adoption. Our approach opens a general and convenient route for integrating low dimensional oxide nanostructures with macroscopic metal substrates for various applications.