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Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions
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Combined electrokinetic and shear flows control colloidal particle distribution across microchannel cross-sections
Varun Lochab1, Shaurya Prakash1
1Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA. prakash.31@osu.edu.
Soft Matter
|November 17, 2020
Summary
Fluid viscosity controls particle migration in microfluidic channels. Increased kinematic viscosity suppresses particle movement, enabling new 3D control of colloidal suspensions via electrophoresis-induced lift forces.
Area of Science:
- Colloidal science
- Microfluidics
- Physical chemistry
Background:
- Experimental observations show unusual cross-stream migration and assembly of colloidal particles in microfluidic channels under combined electrokinetic and shear flows.
- An electrophoresis-induced lift force is postulated for lateral particle migration, but its dependence on fluid properties and flow conditions is poorly understood.
- Experimental quantification of this electrophoresis-induced lift force is lacking.
Purpose of the Study:
- To investigate the impact of fluid properties, specifically kinematic viscosity, on electrophoresis-induced lift force and colloidal particle migration.
- To experimentally quantify the electrophoresis-induced lift force under various flow conditions.
- To explore the potential for three-dimensional control of colloidal particles in microchannels.
Main Methods:
- Experiments were conducted on colloidal suspensions in rectangular microfluidic channels.
- Varying fluid kinematic viscosity and flow conditions (Reynolds number range 0.1–1.1) were employed.
- Colloidal particle migration and spatial distribution were analyzed to infer lift forces.
Main Results:
- Kinematic viscosity was demonstrated as a key factor in modulating particle distribution across the microchannel.
- Increased fluid kinematic viscosity suppressed colloidal particle migration.
- Significant particle migration (∼10 μm) from all channel walls was observed, with electrophoresis-induced lift forces up to ∼30 fN.
- Inertial migration was observed even in flow regimes where it was previously considered ineffective, attributed to the electrophoresis-induced lift force.
Conclusions:
- The study establishes fluid kinematic viscosity as a critical parameter for controlling colloidal particle migration in microfluidic systems.
- The electrophoresis-induced lift force is quantified and shown to be significant, enabling particle migration across the entire microchannel cross-section.
- This work presents a new paradigm for achieving precise three-dimensional control of colloidal particles within confined microchannels.
