Wednesday, 12 April 2017

The “building blocks” of the world’s lightest material revealed

A study by Stefano Signetti from the University of Trento in Nature Communications sheds light on the nanomechanical features of tetrapods, aerographite’s “building blocks”

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It is black, super flexible, hydrophobic, highly conductive and, most of all, it is the world’s lightest material ever created:  aerographite. It was created in 2012 based on graphene in the research laboratories of the universities of Kiel and Hamburg. Weighting 0,2 milligrams per cubic centimeter, that is up to 6 times lighter than air and 75 times lighter than polystyrene, it is currently considered an extremely interesting material for its diverse possible applications when both lightness and resistance are sought. It can be used, for example, in ultra-light batteries for cars and e-bikes, mobile devices, models of biological scaffolds for medical applications, filters to treat air, oil or water containing pollutants and impurities, and even in foams to be used to reduce the impact of micrometeorites on space crafts. The Italian Space Agency finds this latter aspect particularly interesting.

These features are made possible by a highly porous 3D network which allows for the creation of long-lasting, light and resistant scaffolds,  thanks to interwoven carbon nanotubes that make up aerographite. However, there is still a lot to be discovered on this material, and researchers believe there is a chance to even further improve its performance. A study that has recently been published in Nature Communications, the prestigious scientific journal, marks a step forward in understanding the nanomechanics of the individual structural elements of aerographite. Based on nanoscale experiments, analytical modelling, numerical simulations, the study revealed the nanomechanics of individual tetrapods, the “building blocks” of aerographite.
The part of the study on numerical simulations was conducted by Stefano Signetti, PhD candidate and member of the research group of the Department of Civil, Environmental and Mechanical Engineering at the University of Trento led by Nicola Pugno, who coordinates the project in collaboration with researchers from the universities of Kiel and Hamburg (the very ones who created this material) and the University of Latvia. The project is funded under the Graphene Flagship consortium, the research initiative by the European Commission under Horizon 2020 involving over 150 scientists from 23 countries with a budget of 1 billion euro.

The study by the University of Trento focused mainly on the analytical and numerical modelling of the nanomechanics of individual aerographite tetrapods. With their peculiar tubular morphology (with arms having a length of 10-20 µm, diameter of 3 5 µm and thickness of 10-30 nm), their central joints experience elastic instability and bend, behaving therefore like a sort of “elastic zipper”.

Mechanical tests, carried out using an atomic force microscope, included also numerical simulations. Modelling showed the mechanical behaviors of tetrapods of different size and shape when under compression or tension, and when in contact with other aerographite tetrapods. The results achieved shed light on the behavior of aerographite networks as a whole. Understanding the mechanics of the individual “building block” is crucial to devise new types of aerographite with even better mechanical features.

Project coordinator Nicola Pugno is very satisfied with the work of Stefano Signetti: «I am very proud of his work. I selected him during a project set up by the Alta Scuola Politecnica, and he followed me to Trento since the beginning, to work on his doctoral program. He has put a lot of commitment and effort in this project, took my advice, and achieved excellent results. Signetti published about a dozen articles in prestigious international journals and has already been invited to the Korea Advanced Institute of Science & Technology (KAIST) for a post-doc position to work with professor Ryu, an emerging Korean scientist who has been to Trento as visiting professor. He is a black belt, second dan, in ju-jitsu, and maybe this helped him to keep up with the pace of the lab: meetings sometimes were held while biking uphill in the evening sun».

References to the original publication:
R Meija, S. Signetti, A. Schuchardt, K. Meurisch, D. Smazna, M. Mecklenburg, K.Schulte, D. Erts, O. Lupan, B. Fiedler, Y.K. Mishra, R. Adelung, N.M. Pugno Nanomechanics of individual aerographite tetrapods
Nature Communications. DOI:

This research was funded mainly by:
the European Commission under the Graphene Flagship (WP14 “Polymer Composites”, no. 696656).