Real-time nanoparticle characterization through opto-fluidic force induction

TL;DR

This paper introduces OF2i, a real-time optical method for nanoparticle characterization that combines microfluidics and optical forces to measure particle size distribution with high sensitivity and throughput.

Contribution

The paper presents a novel optofluidic force induction scheme that enables real-time, single-particle sensitivity nanoparticle sizing across a wide size range, validated by a parameter-free theoretical model.

Findings

Achieves real-time nanoparticle counting with high sensitivity.

Provides accurate size distribution for particles from tens of nanometers to several micrometers.

Demonstrates potential applications in pharmaceuticals and medical diagnostics.

Abstract

We propose and demonstrate a novel scheme for optical nanoparticle characterization, optofluidic force induction (OF2i), which achieves real-time optical counting with single-particle sensitivity, high throughput, and for particle sizes ranging from tens of nanometers to several $\mu$m. The particles to be analyzed flow through a microfluidic channel alongside a weakly focused laser vortex beam, which accomplishes 2D trapping of the particles in the transverse directions and size-dependent velocity changes due to the optical forces in the longitudinal direction. Upon monitoring the trajectories and velocity changes of each individually tracked particle, we obtain detailed information about the number based particle size distribution. A parameter-free model based on Maxwell's equations and Mie theory is shown to provide very good agreement with the experimental results for standardized particles of spherical shape. Our results prove that OF2i can provide a flexible work bench for numerous pharmaceutical and technological applications, as well as for medical diagnostics.