Geometrical Performance of Self-Phoretic Colloids and Microswimmers

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Microfluidics

Background:

• Phoretic phenomena (self-electrophoresis, self-diffusiophoresis, self-thermophoresis) drive micro-particle motion.
• Understanding the relationship between surface activity and resulting particle velocity is crucial for designing micro-motors.

Purpose of the Study:

• To present a unified theoretical framework for predicting the velocity of spheroid micro-particles driven by axisymmetric surface activity.
• To introduce a dimensionless performance metric for micro-motor shape and surface activity distribution.
• To identify optimal spheroid geometries and surface partitioning for maximal self-propulsion.

Main Methods:

• Developed a simple integral kernel to relate surface flux to particle velocity for spheroids.
• Introduced a scaled speed as a dimensionless measure of motor performance.
• Mapped performance across a range of geometries (discotic, spherical, rodlike) and bipartite surface activity distributions.

Main Results:

• The integral kernel provides a general method for calculating particle velocity from surface activity.
• A dimensionless performance metric quantifies the efficiency of micro-motor designs.
• Optimal intermediate aspect ratios and specific bipartitioning strategies for maximizing propulsion were identified.
• Theoretical predictions were validated against experimental data from existing literature.

Conclusions:

• The unified formulation simplifies the analysis of various phoretic self-propulsion mechanisms.
• The findings offer guidelines for designing high-performance micro-motors by optimizing shape and surface activity.
• This work provides a valuable tool for researchers in micro-robotics and targeted drug delivery.