Microfluidic devices are critical components of promising future applications including massively parallel drug discovery, integrated sensors for biological and chemical threats, and personalized medicine. Despite their small size, many microfluidic systems currently in use are limited to the laboratory due to large operational voltages. A relatively new class of device that places micron size electrodes inside channels is promising as they operate at relatively low voltage--a key requirement for portability. Most computational models of these devices are based in the classical theory of electrokinetic phenomena which couples fluid flow, ion transport and electric fields in electrolytes. Unfortunately, these models fail to predict some critically important experimental trends, impeding their development. Recent work by the PI and collaborators has started to apply simple corrections to the classical theory of electrokinetics to account for some of the major deficiencies. To date, the corrected models can predict some of the key trends but the agreement between model and experiment is still lacking. The overall objective of this work is to improve modeling capability in these electrically driven microfluidic applications such that one can use relatively simple simulations as a tool for engineering design. While the phenomena of interest is truly at the nanoscale, the strategy put forth is to develop an accurate yet tractable continuum-based formulation that can be applied by other researchers. This study has two main trusts. The first is to study the role of incorporating surface roughness into the model. The second thrust will be to investigate the role that electrochemical reactions at the electrode surface plays in models of these flows. The hypothesis is that inclusion of these two effects can go a long way toward resolving key discrepancies between simulation and experiment. While the field of electrokinetics is very mature, the microfluidic designs of interest operate in regimes where aspects of the commonly used theory do not apply. This study develops several carefully planned research projects to provide Olin undergraduate students with an immersive, modern and successful research experience.
