Page 34 - Plastics News May 2019

FEATURES

Superlubricity and Nanotechnology

Michael Berger
Superlubricity offers promising solutions to overcome lubrication challenges in various areas of nanotech-
nology including micro/nano-electromechanical systems

riction is the name given to the force that resists the of energy, as long as there is any friction.However, there
FLQLWLDWLRQ RI VOLGLQJ PRWLRQ EHWZHHQ WZR VXUIDFHV LW LV is a very special case where friction almost vanishes
all around us and it occurs at all length scales. between two surfaces. This is a phenomenon, known
as superlubricity, in which surfaces simply slide over
In simple terms: friction is a force that slows things down.
In many cases, it is exploited to improve our life (you each other with barely any resistance (a state that is
couldn't walk, drive or even write if there was no friction called near-zero friction). To date, however, most of the
superlubricity observed experimentally has been realized
only at the nanoscale and under extreme conditions like
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therefore isn't really suitable for real world applications
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systems is due to the very complex physical, chemical,
and mechanical interactions that occur simultaneously at
the sliding interfaces of these systems.

Achieving near-zero friction in commercial and industrial
applications will be game-changing from tiny micro
electromechanical systems that will never wear out, to
oil-free bearings in industrial equipment, to much more
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energy even in low wind conditions. Superlubricity offers
promising solutions to overcome lubrication challenges in
various areas of nanotechnology including micro/nano-
electromechanical systems (MEMS/NEMS), water transport
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required to reduce mechanical energy dissipation and (AFM), aerospace and wind energy applications, as well as
wear. The reduction of friction is particularly critical for other electronic devices. It is one of the most promising
energy conservation where friction directly translates in properties of functional nanomaterials for energy saving
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a particular task. About 1/3 of the world’s primary energy
For example, conductive AFM is one of the most effective
LV GLVVLSDWHG LQ PHFKDQLFDO IULFWLRQ DQG RI PDFKLQHU\ instruments to characterize electrical properties of
components' failure is caused by wear. Friction and wear materials at the nanoscale. However, a critical challenge
are also bottlenecks for micro-/nano-mechanical systems associated with this characterization technique is the low
(MEMS and NEMS) featured with sliding components.
reliability of AFM tips during high-current testing, which
In Nature, there are no completely frictionless is related to rapid wear by the friction of tip-sample
environments: even in deep space, tiny particles may interfaces. Therefore, superlubricity at the tip-sample
interact and cause friction. Friction processes can be interfaces is a promising way to avoid tip wear for reliable
observed on all scales and dimensions. This is one reason nanoscaled electrical characterization. Recent advances
why you can't have a perpetuum mobile, i.e. a motion in two-dimensional (2D) materials, such as graphene, (but
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Plastics News May 2019 34