8 February, 2022
A new paper published in the journal Nature Synthesis, reported a new type of solidification patterns appearing on the surface of solidifying liquid metals. MacDiarmid Institute PhD student Stephanie Lambie with Co-Director and Principal Investigator Professor Nicola Gaston from the University of Auckland, and Associate Investigator Dr Krista Steenbergen from Te Herenga Waka Victoria University of Wellington were part of the collaboration of scientists from Australia, New Zealand, and the US authoring the paper.
Professor Gaston, Dr Steenbergen and Stephanie Lambie formed one of two molecular dynamics simulation groups that carried out supercomputer simulations to provide atomistic insights to the phenomenon. The other molecular dynamic simulation group was led by Professor Salvy Russo (RMIT University, Australia). The collaboration with Professor Gaston’s group was established through the Australian Research Council Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), a partner of the MacDiarmid Institute. As well as bringing together FLEET researchers from two participating nodes (UNSW and RMIT), the work combined two Australian Research Council (ARC) Centres of Excellence: FLEET, and the Centre for Exciton Science.
Pattern formation is a fundamental yet ubiquitous phenomenon which has interested and inspired scientists for a long time. Some pattern types are more common than others.
Among all the diverse patterning behaviours, divergent pattern formation, or bifurcation, is frequently seen in nature because this particular arrangement generally favours energy conversion or distribution explains Dr Jianbo Tang from University of New South Wales (UNSW), first author of the paper. River networks, tree branches, lightning pathways, and vascular systems are all examples of bifurcation.
In comparison, convergent pattern growth, or inverse bifurcation, is encountered less frequently as it is contrary to the energetically favourable bifurcation.
The strange cyclic divergent and convergent growth, called oscillatory bifurcation, is rare and has not been observed in solidification structures prior to the new published work.
Despite this, the researchers observed oscillatory bifurcation patterns on the surface of several liquid alloys after solidification, which suggests that this counter-intuitive behaviour is quite general for solidification patterns forming on the surface of liquid metals.
"The work can provide the idea that by understanding the way specific atoms interact with each other, under different conditions (concentrations, temperatures), we can persuade them to behave in useful ways." says Professor Gaston.
"If we can persuade individual atoms to behave the way we want them to, to self-assemble by design, then we have access suddenly to a much wider range of nanomaterials."