A New Tracking Algorithm for Multiple Colloidal Particles Close to Contact

TL;DR

This paper introduces a fast, simple algorithm based on radial symmetry for tracking multiple colloidal particles near contact, effectively handling overlapping images to improve measurement accuracy in colloidal studies.

Contribution

The proposed algorithm extends radial symmetry center methods to multiple particles, maintaining accuracy and speed without modifications for different particle counts.

Findings

Maximum error less than 2 nm for 5.53 μm particles in contact

Effective in overlapping image conditions

Applicable to multiple particles without modification

Abstract

In this paper, we propose a new algorithm based on radial symmetry center method to track colloidal particles close to contact, where the optical images of the particles start to overlap in digital video microscopy. This overlapping effect is important to observe the pair interaction potential in colloidal studies and it appears as additional interaction in the measurement of the interaction with conventional tracking analysis. The proposed algorithm in this work is simple, fast and applicable for not only two particles but also three and more particles without any modification. The algorithm uses gradient vectors of the particle intensity distribution, which allows us to use a part of the symmetric intensity distribution in the calculation of the actual particle position. In this study, simulations are performed to see the performance of the proposed algorithm for two and three particles, where the simulation images are generated by using fitted curve to experimental particle image for different sized particles. As a result, the algorithm yields the maximum error smaller than 2 nm for 5.53 {\mu}m silica particles in contact condition.