Jump to main content
Jump to site search


A new methodology for a detailed investigation of quantized friction in ionic liquids

Author affiliations

Abstract

When confined at the nanoscale between smooth surfaces, an ionic liquid forms a structured film responding to shear in a quantized way, i.e., with a friction coefficient indexed by the number of layers in the gap. So far, only a few experiments have been performed to study this phenomenon, because of the delicate nature of the measurements. We propose a new methodology to measure friction with a surface force balance, based on the simultaneous application of normal and lateral motions to the surfaces, allowing for a more precise, comprehensive and rapid determination of the friction response. We report on proof-of-concept experiments with an ionic liquid confined between mica surfaces in dry or wet conditions, showing the phenomenon of quantized friction with an unprecedented resolution. First, we show that the variation of the kinetic friction force with the applied load for a given layer is not linear, but can be quantitatively described by two additive contributions that are respectively proportional to the load and to the contact area. Then, we find that humidity improves the resistance of the layers to be squeezed-out and extends the range of loads in which the liquid behaves as a superlubricant, interpreted by an enhanced dissolution of the potassium ions on the mica leading to a larger surface charge. There, we note a liquid-like friction behavior, and observe in certain conditions a clear variation of the kinetic friction force over two decades of shearing velocities, that does not obey a simple Arrhenius dynamics.

Graphical abstract: A new methodology for a detailed investigation of quantized friction in ionic liquids

Back to tab navigation

Supplementary files

Publication details

The article was received on 03 Oct 2019, accepted on 22 Nov 2019 and first published on 22 Nov 2019


Article type: Paper
DOI: 10.1039/C9CP05422G
Phys. Chem. Chem. Phys., 2020, Advance Article

  •   Request permissions

    A new methodology for a detailed investigation of quantized friction in ionic liquids

    R. Lhermerout and S. Perkin, Phys. Chem. Chem. Phys., 2020, Advance Article , DOI: 10.1039/C9CP05422G

Search articles by author

Spotlight

Advertisements