Optical micro- and nanoparticle characterization in microfluidics

Abstract

The analysis of micro- and nanoparticles in liquids is crucial in many industrial and scientific areas. Here, dark-field video microscopy is combined with microfluidics and 2D-tracking of diffusive Brownian motion to determine the size of particles in a liquid sample. A method was developed for acquisition of very long trajectories from multiple, diffusing nanoparticles, leading to significantly increased sizing precision. Simultaneous tracking of Brownian motion and superimposed sedimentation movement was demonstrated with a custom sensor setup, hence enabling calculation of particle sizes from both principles. Finally, metallic wear particles in oil were characterized by means of dark field tracking in combination with a heatable microfluidic chip. The results highlight the abilities of dark field imaging, video microscopy, particle tracking, and microfluidics, showing potential for a variety of diagnostic applications.