From two-dimensional colloidal self-assembly to three-dimensional nanolithography.

A number of "top-down" lithographic and "bottom-up" self-assembly methods have been developed to fabricate three-dimensional (3D) nanostructures to support the recent advances in nanotechnology. But they are limited by a number of factors such as fabrication cost, pattern resolution, and/or flexibility of geometry. Here we present a 3D nanolithography process that utilizes self-assembled nanospheres to create a periodic array of focal spots, which are then replicated across multiple depth in a transparent medium according to the Talbot effect. The Talbot field then exposes a pattern onto the underlying photoresist, recording the 3D intensity distribution. We have demonstrated designable complex 3D periodic structures with 80 nm minimum feature size, roughly one-fourth of the operating wavelength. This approach combines 2D colloidal self-assembly and 3D phase lithography, is robust, cost-effective, and widely applicable to nanoscale research and manufacturing.

Visualization of flagellar interactions on bacterial carpets.

Methods for the in-depth study of the physics of microscale actuation of microfluidics environments by flagellated bacteria 'teamsters' have been developed. These methods, which include single and multi-colour fluorescent labelling and electron microscopy allow for the analysis of the effect that individual flagellar filaments have on bacterially driven microstructures, and allow for the investigation of the interaction and coordination of flagellar filaments of neighbouring bacteria on densely packed monolayers of bacteria, 'bacterial carpets'. We show that the flagella of bacteria that are immobilized on a surface often interact with each other, and that the flagella of these bacteria do not often form multi-flagella bundles that are aligned with the cell body.