In-Plane Rotation of Prolate Colloids Adhered to a Planar Substrate in the Presence of Flow

Area of Science:

• Colloid science
• Fluid dynamics
• Surface science

Background:

• Micron-size spherical polystyrene colloidal particles are mechanically deformed into prolate shapes.
• These prolate particles are studied in an aqueous medium with controlled ionic concentration.

Purpose of the Study:

• To investigate the behavior and filtration of prolate polystyrene particles in microchannels under unidirectional flow.
• To develop a theoretical model for filtration efficiency considering particle-flow interactions.

Main Methods:

• Mechanical stretching of spherical particles to create prolate shapes.
• Introduction of particles into a microchannel with a glass substrate and unidirectional flow.
• Observation of particle adhesion, orientation, and rotation.
• Development of a theoretical model incorporating hydrodynamic drag and intersurface forces.

Main Results:

• Loosely adhered particles are washed off, while strongly adhered particles align with flow.
• Prolate particles exhibit in-plane rotation influenced by flow direction.
• Filtration efficiency depends on particle reorientation, flow rate, and ionic concentration.

Conclusions:

• The study provides a theoretical framework for understanding particle filtration in microfluidic systems.
• Particle shape and surface interactions significantly influence behavior under flow conditions.
• The findings are relevant for microfluidic device design and particle manipulation.