Operational-modes of field-flow fractionation in microfluidic channels

Area of Science:

• Separation Science
• Analytical Chemistry
• Physical Chemistry

Background:

• Field-flow fractionation (FFF) encompasses various separation modes with distinct theoretical underpinnings.
• A unified theoretical framework is needed to predict and connect these diverse separation behaviors.

Purpose of the Study:

• To develop a single, unified ideal retention theory for predicting a wide range of FFF separation behaviors.
• To introduce and define a device retention parameter to unify different FFF modes.
• To predict and map new operational regimes within FFF.

Main Methods:

• Theoretical analysis of the retention ratio in field-flow fractionation (FFF).
• Introduction of a device retention parameter to unify separation theories.
• Numerical analysis of elution order as a function of particle size.
• Extension of analysis to account for stress variation over particle surfaces.

Main Results:

• A single unified ideal retention theory predicts hydrodynamic chromatography, normal-mode FFF, and steric-mode FFF.
• A critical device retention parameter is identified, defining transitions between regimes.
• A new regime, Faxén-mode FFF, is predicted, occurring when particle sizes approach channel height.
• Numerical mapping of transitions between steric-mode and Faxén-mode FFF is presented.

Conclusions:

• The unified theory and device retention parameter provide a comprehensive framework for understanding and predicting FFF separation modes.
• The identification of Faxén-mode FFF expands the understanding of FFF behavior, particularly in microfluidic applications.
• The findings may guide future design and optimization of FFF devices for enhanced separation capabilities.