High Resolution Viscosity Measurement by Thermal Noise Detection

TL;DR

This paper presents an interferometric method for high-resolution viscosity measurement in liquids using thermal noise detection of a micro-cantilever, achieving high accuracy with minimal sample volume.

Contribution

The study introduces a novel interferometric approach combined with Sader's model to accurately measure liquid viscosity via thermal fluctuations of a micro-cantilever.

Findings

Detected viscosity variations below 0.03 mPa·s

Achieved measurements with as little as 50 μL of sample

Demonstrated high sensitivity and low noise in the measurement system

Abstract

An interferometric method is implemented in order to accurately assess the thermal fluctuations of a micro-cantilever sensor in liquid environments. The power spectrum density (PSD) of thermal fluctuations together with Sader's model of the cantilever allow for the indirect measurement of the liquid viscosity with good accuracy. The good quality of the deflection signal and the characteristic low noise of the instrument allow for the detection and corrections of drawbacks due to both the cantilever shape irregularities and the uncertainties on the position of the laser spot at the fluctuating end of the cantilever. Variation of viscosity below 0.03 mPa$\cdot$s was detected with the alternative to achieve measurements with a volume as low as 50 $\mu$L.