On the 3-dimensional effects in etched chips for high performance liquid chromatography-separations

Area of Science:

• Analytical Chemistry
• Chemical Engineering
• Fluid Dynamics

Background:

• Packed beds of spheres are commonly used in chromatography and other separation techniques.
• Micro-pillar arrays offer a potential alternative with improved ordering and flow control.
• Understanding band broadening is crucial for optimizing separation efficiency.

Purpose of the Study:

• To quantify the band broadening caused by top and bottom plates in micro-pillar arrays.
• To compare the performance of micro-pillar arrays with traditional packed beds.
• To develop a predictive model for band broadening in micro-pillar arrays.

Main Methods:

• Computational fluid dynamics (CFD) simulations were employed.
• The study investigated the influence of axial distance, velocity, inter-pillar distance, and pillar height.
• A phenomenological model was developed and validated against simulation results.

Main Results:

• Additional band broadening from top and bottom plates exhibits a transient regime before reaching a steady state.
• In the fully developed regime, wall effects can nearly double band broadening compared to arrays without walls.
• These wall effects become negligible for porous, retentive pillars.

Conclusions:

• Micro-pillar arrays present a tunable platform for chromatographic separations.
• Top and bottom plate effects are significant and must be accounted for in micro-pillar array design.
• The proposed phenomenological model provides a useful tool for predicting band broadening in these systems.