Study of Sample Dispersion Mechanisms in an Electroosmotically Pumped Microchannel

B. Debusschere, H. Najm, A. Matta, O. Knio, R. Ghanem and O. Le Maitre
Sandia National Laboratories, US

Keywords: dispersion, electroosmotic, stochastic, microchannel, protein labeling, zeta-potential

Abstract:
In many microfluidic separation processes, dispersion of sample peaks is a significant problem limiting the detection resolution. In this work, we use simulations to study the dominant dispersion mechanisms during a protein labeling process in electroosmotic microchannel flow with a potassium phosphate buffer. The goal is to explain the dominant dispersion mechanisms and to provide a tool for predicting and minimizing dispersion in microchannel flows. The simulations are performed with a stochastic microchannel simulation code. We use a detailed representation of electroosmotic and pressure-driven channel flow by solving the coupled momentum, species transport, as well as electrostatic field equations. The chemistry model accounts for pH-dependent protein labeling reactions as well as detailed buffer electrochemistry in a mixed finite-rate/equilibrium formulation. The model also has the unique capability to account for stochastic processes, such as random zeta-potential variability. In our talk, we will specifically address two phenomena. The first is the electrokinetic and hydrodynamic dispersion, caused by the disturbance of the buffer solution as a sample moves through the channel. The second is the effect on dispersion of random zeta-potential variability, due to surface roughness or heterogeneous wall material properties.

NSTI Nanotech 2003 Conference Technical Program Abstract