Studying microscopic interactions at single asperities is vital for the understanding of friction and lubrication at the macroscale. Surface probe instruments with carbon nanotube tips may enable such investigations, as now demonstrated in a theoretical study led by Ping Liu and Yong-Wei Zhang at the A*STAR Institute of High Performance Computing1. The researchers showed that short, single-walled, capped carbon nanotubes are able to capture the frictional characteristics of graphene with atomic resolution.
Atomistic simulations show that short, capped single-walled carbon nanotubes (red) can elucidate the tribological properties of graphene surfaces. Copyright : 2011 Elsevier
“For an ideal probing tip, its dimension should be as small as possible, its rigidity should be as large as possible, its geometry should be well-defined, and it should be chemically inert,” explains Liu. The combination of such characteristics would allow surface characterization with atomic resolution while ensuring a long lifetime and geometrical, chemical and physical stability of the tip.
Carbon nanotubes, in particular short ones, are of great interest due to their inherent strong carbon–carbon bonds, which allows them to withstand buckling and bending deformation and recover to their original shape after deformation. Capped tubes in turn offer improved chemical stability and stiffness in comparison to non-capped tubes. These considerations indicate that short, capped single-walled carbon nanotubes may be ideal imaging probe tips.
As it is not yet possible to use such tips in experimental setups, to test this hypothesis Liu and Zhang performed large-scale atomistic simulations focusing on the interaction between such nanotube probing tips and graphene (see image)—a carbon material that is ideal for surface coating lubrication. “Because of advances in the development of accurate atomic potentials and massive parallel computing algorithms, atomistic simulations not only enable us to determine the probing characteristics of such tips, but also to investigate the frictional and defect characteristics of graphene with atomic resolution,” says Liu.
The simulations could capture the dependence of the friction and average normal forces on tip-to-surface distance and number of graphene layers. The researchers analyzed and interpreted the observed characteristics in terms of different types of sliding motions of the tip across the surface, as well as energy dissipation mechanisms between the tip and underlying graphene layers. They could further identify clear signatures that distinguish the motion of a tip across a point defect or the so-called Stone-Thrower-Wales defect, which is thought to be responsible for nanoscale plasticity and brittle–ductile transitions in the graphene carbon lattice. “Our simulations provide insight into nanoscale friction and may provide guidelines on how to control it,” says Liu.
The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing
Advanced AI boosts clinical analysis of eye images
19.09.2019 | Universitätsspital Bern
Quantum computers by AQT and University of Innsbruck leverage Cirq for quantum algorithm development
16.09.2019 | Universität Innsbruck
To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Potsdam (both in Germany) and the University of Toronto (Canada) have pieced together a detailed time-lapse movie revealing all the major steps during the catalytic cycle of an enzyme. Surprisingly, the communication between the protein units is accomplished via a water-network akin to a string telephone. This communication is aligned with a ‘breathing’ motion, that is the expansion and contraction of the protein.
This time-lapse sequence of structures reveals dynamic motions as a fundamental element in the molecular foundations of biology.
19.09.2019 | Event News
10.09.2019 | Event News
04.09.2019 | Event News
19.09.2019 | Power and Electrical Engineering
19.09.2019 | Physics and Astronomy
19.09.2019 | Event News