Fiber-assisted nanoparticle tracking analysis meets nanorheology: a novel approach for probing viscoelastic properties at the nanoscale.

This study introduces fiber-assisted nanoparticle tracking analysis (FaNTA) as a platform for nanorheology that utilizes an advanced antiresonant optical fiber to analyze the viscoelastic properties of fluids at the nanoscale. The platform confines colloidal nanotracers within a fiber-integrated microchannel, significantly extending observation times and improving statistical accuracy. The FaNTA system consists of a custom-designed microstructured antiresonant fiber, a dedicated optical setup, and sophisticated data processing including image analysis and statistical filtering, enabling precise determination of the hydrodynamic diameter and thus the local viscosity. The study demonstrates the capabilities of the FaNTA concept in the context of rheology by measuring the viscosity of glycerol-water solutions at different concentrations using 50 nm gold nanospheres as nanoprobes. By analyzing their individual diffusive motion, the platform accurately determines fluid viscosities with results that closely match literature values, validating the efficacy of FaNTA for nanorheological applications. FaNTA's high accuracy and performance in nano- and microrheological measurements highlight its broad potential in nanoscale materials science, dynamic process studies, life and environmental sciences, and nanochemistry. This innovative approach provides a valuable extension to current microrheological methods and offers precise nanoscale fluid characterization for a wide range of applications.