A new tuning fork-based instrument for oscillatory shear rheology of nano-confined liquids

TL;DR

This paper introduces a novel nano-confined liquid rheology instrument using a sensitive force sensor to measure shear forces at high frequencies, enabling exploration of slow-down effects and non-linear behaviors in confined liquids.

Contribution

The paper presents a robust, off-resonance shear rheology instrument capable of measuring nano-confined liquids' response at high frequencies, addressing previous measurement limitations.

Findings

Able to measure shear forces from 1 to 10 nN

Operates at shear frequencies above the system relaxation time

Facilitates investigation of non-linear effects in nano-confined liquids

Abstract

We present a new method to measure rheological response of liquids confined to nano-scale which exhibit a considerable slow-down in dynamics compared to bulk liquids. The method relies on using a robust force sensor that has a sensitivity to measure shear forces in the range of 1 to 10 nN and a stiffness of 55000 N/m to avoid thermal noise. Off-resonance operation ensures application of a range of shear frequencies . This range is higher than the inverse of the system's mechanical relaxation time and allows the measurement of non-linear effects emerging due to significant "slow down" in dynamics upon confinement. The instrument is a step forward towards resolving the controversies about the nature of nano-confined liquids.