Nano-indentation of a room-temperature ionic liquid film on silica: a computational experiment

TL;DR

This study uses atomistic simulations to examine how a thin ionic liquid film interacts with silica during nano-indentation, revealing layering effects and fluidity loss, with results aligning closely with experimental AFM data.

Contribution

It provides a detailed atomistic simulation of ionic liquid-silica interface indentation, matching experimental measurements and revealing structural and mechanical insights.

Findings

Identification of weak layering in ionic liquid near silica

Observation of fluidity loss approaching silica surface

Simulation results agree with AFM measurements

Abstract

We investigate the structure of the [bmim][Tf2N]/silica interface by simulating the indentation of a thin (4 nm) [bmim][Tf2N] film by a hard nanometric tip. The ionic liquid/silica interface is represented in atomistic detail, while the tip is modelled by a spherical mesoscopic particle interacting via an effective short-range potential. Plots of the normal force (Fz) on the tip as a function of its distance from the silica surface highlight the effect of weak layering in the ionic liquid structure, as well as the progressive loss of fluidity in approaching the silica surface. The simulation results for Fz are in near-quantitative agreement with new AFM data measured on the same [bmim][Tf2N]/silica interface at comparable thermodynamic conditions.