Single-trajectory characterization of active swimmers in a flow

Area of Science:

• Physics of active matter
• Statistical mechanics
• Biophysics

Background:

• Characterizing the physical properties of active particles, such as microswimmers, is crucial for understanding their behavior in complex fluids.
• Existing methods often struggle with heterogeneous particle populations or require ensemble measurements.

Purpose of the Study:

• To develop a robust maximum likelihood method for inferring physical properties of elongated active particles from individual trajectories.
• To provide reliable uncertainty quantification for the inferred properties.

Main Methods:

• A maximum likelihood estimation framework is employed to analyze single-particle trajectories.
• The method utilizes particle movement data in various flow conditions (no flow, simple shear, Poiseuille flow) for validation.

Main Results:

• Accurate determination of rotational diffusion coefficients and effective aspect ratios for active particles.
• Reliable estimation of uncertainties associated with these physical quantities.
• Successful validation using numerically generated trajectories under different flow regimes.

Conclusions:

• The developed method effectively characterizes elongated active particles using single-trajectory data.
• Its ability to handle morphological diversity makes it suitable for diverse experimental conditions, including the study of swimming bacteria like E. coli.