A new tracking algorithm for multiple colloidal particles close to contact

Area of Science:

• Colloidal science
• Optical microscopy
• Particle tracking

Background:

• Observing pair interaction potentials in colloidal systems is crucial.
• Overlapping particle images in digital video microscopy complicate conventional tracking analysis.
• This overlap can lead to inaccurate measurements of inter-particle forces.

Purpose of the Study:

• To develop a novel algorithm for tracking colloidal particles that are close to contact.
• To address the challenges posed by overlapping particle images in microscopy.
• To improve the accuracy of measuring pair interaction potentials.

Main Methods:

• A new algorithm based on the radial symmetry center method is proposed.
• The algorithm utilizes gradient vectors of particle intensity distribution.
• It calculates particle positions using partial symmetric intensity distribution, applicable to multiple particles.

Main Results:

• The algorithm is simple, fast, and effective for tracking two, three, or more particles.
• Simulations were conducted using experimental particle image data for various particle sizes.
• The maximum tracking error was found to be less than 2 nm for 1 μm silica particles in contact.

Conclusions:

• The proposed radial symmetry-based algorithm accurately tracks colloidal particles, even when their images overlap.
• This method overcomes limitations of conventional tracking analysis for closely spaced particles.
• It offers a reliable tool for studying pair interaction potentials in colloidal systems.