Tuning the material structure at the nanoscale level can be really hard to achieve – but what if we had small particles, which assemble all by themselves, creating the required structure? At the Vienna University of Technology (TU Wien), the phenomenon of self-assembly is being investigated by studying inhomogeneously charged particles. Depending on different parameters, they can form gel-like or crystal-like structures. This kind of self-assembly holds great promise for nanotechnology.

Emanuela Bianchi, a scientist in Prof. Gerhard Kahls research group at the Institute for Theoretical Physics, uses computer simulations to reproduce the bahavior of particles which are no bigger than a few micrometers – comparable to viruses or small bacteria. Her recent work has focused on particles with inhomogeneously charged surface regions: The majority of the particle carries negative electric charge, but the polar regions on the top and at the bottom of the particle are positively charged. “Due to the fact that like charges repel while opposite charges attract each other”, says Emanuela Bianchi, “our particles tend to align in such a way that the pole of one particle points towards the equator of the other.” But when many of these particles interact, things get more complicated.

“With our model, we can find out which parameters determine the emerging structure...”Emanuela Bianchi, scientist at the Institute for Theoretical Physics, Vienna University of Technology.

Computer simulations have now been able to show how these particles behave when they are trapped between two planes so that they have to align in quasi two dimensional structures. Results showed that there are different possible configurations. Sometimes the particles are tightly packed in a simple hexagonal structure, which is well known from crystals. Sometimes, less ordered gel-like structures emerge, with interconnected rings of five or six particles. “With our model, we can find out which parameters determine the emerging structure”, says Emanuela Bianchi.

Understanding the self-assembly of microparticles opens the door to designing particles which automatically form taylor-made structures. Depending on the microscopic alignment of the particles, they create surface types with different densities and different responses to external stimuli (e.g. elcetromagnetic fields). This means that self-assembled structures could for instance be used to create filters with tunable porosity. “Especially for biomedical applications, this could have many possible applications”, says Emanuela Bianchi.

This story is reprinted from material from Vienna University of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.