Role of Channel Morphology In Microfluidic Applications: Impact on the Behavior of the Electrostatic Potential for An Idealized Case

Microfluidic concepts have become more widely known and helpful to advance technological applications in, for example, health informatics and environmental proteomics just to mention two leading ones. The systematic investigation of the role of both, channel geometry and channel morphology are far to be complete. In particular, their impact on the key variable for electrokinetic applications, i.e., the electrostatic potential has not been addressed. This is of crucial importance since the electric fields can induce electro-convective flow of an electrolyte inside the microfluidic devices that controls, for example, the overall motion of the analyte. The understanding of this motion can help in assessing the role of the electrostatic potential on the transport aspects of the analyte and, therefore, understand the characteristics and performance of microfluidic devices.

The complexities of analyzing channel geometry and channel morphology are not trivial and, in this project, we have proposed a relative simple (but effective) selection of two geometries, i.e. rectangular and cylindrical, and one type of morphology: A convergent and divergent section of the channel. As a by-product of the investigation, one can assess also the behavior of the electrostatic potential inside of a convergent-divergent section. Three key parameters have been identified to describe the electrostatic potential behavior: The angle (α) of the convergent (or divergent) section (related to the walls of the channels) that handles the ?magnitude? of the deviation with respect to the regular channel; the ratio of the wall potentials, R, which handles the symmetrical/non-symmetrical aspects of the electrostatic potential, and the ratio of the width to the length (γ) that controls the ?shape? of the channel section.

A study of the electrostatic potential in divergent and convergent symmetrical channels has been performed based on the use of the 2D Poisson-Boltzmann Equation (PBE); this equation has been solved for the cased of the Debye ?Huckel approximation. Results of this study will be shown by using a series of portraits that capture the key behaviors of the electrostatic potential with respect to the three parameters described above. Suggestions for integrating these results into flow and transport studies will be also offered.