Micromirror total internal reflection microscopy for high-performance single particle tracking at interfaces

TL;DR

This paper introduces a micromirror-based total internal reflection dark field microscopy technique that achieves high-precision, high-speed single particle tracking at interfaces, surpassing previous scattering-based methods in background suppression and localization accuracy.

Contribution

The authors develop a novel micromirror TIR dark field microscopy method that significantly improves background suppression and localization precision for nanoparticle tracking at interfaces.

Findings

Achieves nm localization precision at 6 μs exposure for 20 nm gold nanoparticles.

Demonstrates sub-nm deterministic flow characterization at liquid-liquid interfaces.

Approaches optimal background suppression and localization accuracy for scattering-based nanoparticle tracking.

Abstract

Single particle tracking has found broad applications in the life and physical sciences, enabling the observation and characterisation of nano- and microscopic motion. Fluorescence-based approaches are ideally suited for high-background environments, such as tracking lipids or proteins in or on cells, due to superior background rejection. Scattering-based detection is preferable when localisation precision and imaging speed are paramount due to the in principle infinite photon budget. Here, we show that micromirror-based total internal reflection dark field microscopy enables background suppression previously only reported for interferometric scattering microscopy, resulting in nm localisation precision at 6 $\mu$s exposure time for 20 nm gold nanoparticles with a 25 x 25 $\mu$m$^{2}$ field of view. We demonstrate the capabilities of our implementation by characterizing sub-nm deterministic flows of 20 nm gold nanoparticles at liquid-liquid interfaces. Our results approach the optimal combination of background suppression, localisation precision and temporal resolution achievable with pure scattering-based imaging and tracking of nanoparticles at regular interfaces.