Symposium SM01: Materials Modulating Stem Cells and Immune Response
MRS Outstanding Early-Career Investigator Award recipient Huolin Xin

Symposium CT02: In Situ TEM Characterization of Dynamic Processes During Materials Synthesis and Processing

Xiang Wang, University of Pittsburgh

Late News: Atomic-Scale Friction Between Single-Asperity Contacts Under In Situ Transmission Electron Microscopy

Written by Jessalyn Hui Ying Low

Nanostructures are commonly used in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS). For this, atomic friction between nanoscale components should be considered. “Understanding atomic friction between nanoscale contact is very important to control the surface value and extend their service life,” says Xiang Wang.

In this talk, Wang describes their proposed approach to studying the atomic friction process. Here, they designed a set-up consisting of a substrate and mobile tip, allowing for nanoscale contact between mechanical tungsten asperities. Controlled motion was then performed under high-resolution transmission electron microscopy (HRTEM), and also coupled with molecular dynamics simulations. Such an approach holds multiple advantages – high atomic scale resolution and in particular, real-time observation which is difficult to be achieved by conventional techniques like atomic force microscopy (AFM). 

Using this approach, they discovered that friction between single-asperity nanocontacts displayed a typical stick-slip behavior. Interestingly, they had observed that in one period, there occurs two slipping events, with slipping route along two different [111] directions. In addition, they had found that strain distribution on the interface during friction is inhomogeneous. During friction, atoms accumulate strain energy for subsequent slipping, but only some elastic strain is being released after the slip, indicating an asynchronous evolution of the accumulation and release of strain energy. This study highlights a promising way of using in situ TEM to gain mechanistic insights into atomic friction.

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