University of Melbourne, Australia

A nanoscientist says block co-polymers may unblock nanotechnology.

One of the great drivers of the nanotechnology revolution has been the dream of molecular assembly. Essentially, this means using molecular or chemical forces to self-assemble smart or functional structures that could be integrated into electronic or optical devices.

Thomas Russell and his colleagues have recently provided a superb example of the way the field may be heading (B. Kim et al. Small 3, 1869–1872; 2007).They took a diblock polymer — one that self-assembles into micelles — known as poly(styrene-b-4-vinylpyridine) and forced it to form microdomains by tuning the micelle structure through solvent exchange. This led to hexagonally ordered templates with periods of about 45 nanometres.

They then transferred these polymer templates by reactive ion etching to aluminium surfaces and fabricated regular pores by anodic oxidation at 4° C. The resulting hexagonal, close-packed pores are just 12 nanometres across, with nearest-neighbour spacings that should be tunable over a range of about 10–50 nanometres. The ordering extends over an area several micrometres square.

Particularly elegant is the seamless combination of colloid chemistry with more conventional 'top-down' processing. These wet chemical methods should be cheaper and more scalable than more conventional cleanroom-based techniques. What is particularly exciting about this approach is that the diblock structure can be readily tuned to provide a range of surface topologies and so a wide variety of potential templates. These could drastically simplify the fabrication of periodic, sub-wavelength structures for plasmonics-based applications such as optical circuitry.