Electrically driven flow near a colloidal particle close to an electrode with a Faradaic current.

Area of Science:

• Colloid and Surface Science
• Electrokinetics
• Fluid Dynamics

Background:

• Electrically driven particle aggregation is crucial in various industrial processes.
• Understanding the fluid dynamics near charged particles and electrodes is key to controlling aggregation.
• Existing models often simplify the complex interplay of electrical forces and fluid flow.

Purpose of the Study:

• To elucidate the processes driving particle aggregation in electric fields.
• To analyze the contributions of electroosmotic flow (EOF) and electrohydrodynamic (EHD) flow.
• To investigate the relationship between flow characteristics and aggregation velocity.

Main Methods:

• Studied fluid flow near a charged spherical colloidal particle adjacent to an electrode in steady electric fields.
• Developed analytical models for EOF and EHD flow components.
• Performed scaling analysis to determine flow dependencies on system parameters.

Main Results:

• Identified two primary flow components: EOF and EHD flow, driven by electrical body forces.
• Showed that EOF depends on current density and zeta potential, while EHD flow scales with current density and applied potential.
• Demonstrated that flow superposition can lead to particle aggregation, with EHD flow dominating in the far field.

Conclusions:

• The combined EOF and EHD flows provide a mechanism for electrically driven particle aggregation.
• The applied potential's influence on EHD flow may explain aggregation velocity variability at higher field strengths.
• This study offers insights into controlling colloidal particle behavior in electric fields.