Characterisation of Nanoparticle Size Distributions in a Fluid using Optical Forces

TL;DR

This paper presents a novel optical trapping method within microfluidic devices to analyze nanoparticle size distributions and physical properties in fluids, combining optical forces and viscous drag effects.

Contribution

The introduced technique uniquely uses a microcavity-based optical trap to measure nanoparticle properties through threshold behavior analysis, enhancing physical characterization methods.

Findings

Clear threshold behavior observed in trapping events

Parameter related to dielectric polarizability and hydrodynamic radius measured

Potential for detailed nanoparticle characterization in solutions

Abstract

We introduce a method for analyzing the physical properties of nanoparticles in fluids via the competition between viscous drag and optical forces. By flowing particles through a microfluidic device containing an optical microcavity which acts as a combined optical trap and sensor, the variation of the rate of trapping events with the different forces can be established. A clear threshold behaviour is observed which provides a measure of a parameter combining the dielectric polarizability and the hydrodynamic radius. This technique could be applied in combination with other analytic techniques to provide a detailed physical characterisation of particles in solution.