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Adhesion and friction in mesoscopic graphite contacts

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Science  08 May 2015:
Vol. 348, Issue 6235, pp. 679-683
DOI: 10.1126/science.aaa4157

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Using friction to guide fabrication

Ultralow friction found in certain layered materials such as graphite is important in the construction of nanomechanical devices. Koren et al. combined measurements and modeling to characterize the interaction of sliding graphite planes (see the Perspective by Liechti). This helped them to make small graphite devices that featured rotational pivots and multiple locking positions.

Science, this issue p. 679

Abstract

The weak interlayer binding in two-dimensional layered materials such as graphite gives rise to poorly understood low-friction characteristics. Accurate measurements of the adhesion forces governing the overall mechanical stability have also remained elusive. We report on the direct mechanical measurement of line tension and friction forces acting in sheared mesoscale graphite structures. We show that the friction is fundamentally stochastic in nature and is attributable to the interaction between the incommensurate interface lattices. We also measured an adhesion energy of 0.227 ± 0.005 joules per square meter, in excellent agreement with theoretical models. In addition, bistable all-mechanical memory cell structures and rotational bearings have been realized by exploiting position locking, which is provided solely by the adhesion energy.

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