Related Experiment Video
Updated: Apr 19, 2026
08:41
Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions
Published on: September 7, 2018
9.6K
Electrokinetic mixing at high zeta potentials: ionic size effects on cross stream diffusion.
Alireza Ahmadian Yazdi1, Arman Sadeghi2, Mohammad Hassan Saidi1
1Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, Tehran 11155-9567, Iran.
Journal of Colloid and Interface Science
|December 17, 2014
Summary
Finite ion size significantly impacts mixing in micromixers. Steric effects at high zeta potentials enhance mixing efficiency by retarding flow, contrary to point-charge assumptions.
Area of Science:
- Electrokinetics
- Fluid dynamics
- Nanotechnology
Background:
- Electrokinetic phenomena exhibit unique behaviors at high zeta potentials.
- Ionic size (steric) effects become significant in high ionic concentration solutions.
Purpose of the Study:
- Investigate the influence of finite ionic size on cross-stream diffusion.
- Analyze these effects in an electrokinetically actuated Y-shaped micromixer.
Main Methods:
- Employed a finite difference numerical approach on a non-uniform grid.
- Solved the dimensionless governing equations, including the modified Poisson-Boltzmann equation.
Main Results:
- Neglecting ionic size overestimates mixing length at high zeta potentials.
- Steric effects retard flow, enhancing mixing efficiency, especially in narrow channels.
- Increasing zeta potential improves diffusion when ionic size is considered.
Conclusions:
- Finite ionic size is crucial for accurate modeling of micromixer performance.
- Steric effects are vital for understanding electrokinetic transport at high potentials.
Related Concept Videos
01:23Theory of Strong Electrolytes
115
The interionic forces of the strong electrolytes depend on the solvent's dielectric constant, which is the ability of a solvent to store electrical energy, based on its polarizability. and the solution's concentration. In high-dielectric solvents and in dilute solutions, weak electrostatic forces keep ions apart. However, in low-dielectric solvents or concentrated solutions, stronger interionic forces may cause ions to pair up as ionic doublets despite being fully ionized. The theory of strong...
115
01:24Electrochemical Systems
157
Electrochemical systems provide a fascinating insight into the dynamic interplay of charged species within various phases. One notable example is the interaction between a membrane permeable to K⁺ ions but not to Cl⁻ ions, separating an aqueous KCl solution from pure water. As K⁺ ions diffuse through the membrane, they generate net charges on each phase, leading to a potential difference between them.Similarly, when a piece of Zn is immersed in an aqueous ZnSO₄ solution,...
157
01:30The Electrical Double Layer
210
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
210
01:30Processes at Electrodes
92
The electrode interacts with ions in the electrolyte solution at its interface. The rate of oxidation and reduction depends on the speed at which electrons can transfer through this interface. As ions attach to or leave the electrode surface, the electrode acquires a charge, and an electrical potential forms across the interface, making the process more difficult to reach equilibrium. The charge on the electrode affects the local ion concentrations in the solution, though thermal motion...
92
01:29The Colloidal State
167
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called...
167
03:08Electrolytes: van't Hoff Factor
37.8K
Colligative Properties of ElectrolytesThe colligative properties of a solution depend only on the number, not on the identity, of solute species dissolved. The concentration terms in the equations for various colligative properties (freezing point depression, boiling point elevation, osmotic pressure) pertain to all solute species present in the solution. Nonelectrolytes dissolve physically without dissociation or any other accompanying process. Each molecule that dissolves yields one dissolved...
37.8K