Scaling behavior in on-chip field-amplified sample stacking.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Separation Science

Background:

• Field amplified sample stacking (FASS) is a technique to increase analyte concentration.
• Analyte stacking in FASS is limited by molecular diffusion and convective dispersion from electroosmotic flow (EOF).

Purpose of the Study:

• To present a theoretical scaling analysis of stacking dynamics in FASS.
• To validate the theoretical model with experimental data and numerical simulations.
• To identify and characterize different stacking regimes in on-chip FASS.

Main Methods:

• Theoretical scaling analysis of FASS dynamics.
• On-chip sample stacking experiments.
• Numerical simulations of stacking processes.
• Analysis of experimental data under varying electric fields, conductivity gradients, and EOF.

Main Results:

• Identified two distinct stacking regimes: diffusion-dominated and convection-dominated.
• Developed simplified, nondimensional relations for peak concentration and width growth in FASS.
• Validated theoretical scaling behavior with numerical simulations and experimental results.
• Demonstrated that experimental data align with predicted scaling behavior across various parameters.

Conclusions:

• The scaling analysis provides fundamental insights into FASS dynamics.
• Understanding these regimes allows for optimization of on-chip FASS by controlling experimental parameters like electric field and conductivity gradients.
• This work offers a framework for predicting and enhancing analyte stacking efficiency in microfluidic devices.