(142bi) Analysis of Groove Micromixers: Shape Optimization Study

Micromixing is a key step in realizing fast analysis time in many bio-chemical, biological and detection applications of Lab-on-a-chip (LOC) devices. The conventional T-mixer design requires longer channel lengths and times to achieve complete mixing owing to its dependence on transverse diffusion. The performance of a homogeneous T-mixer can be enhanced significantly by the stimulation of secondary/ transverse flows in the microchannel. The groove based micromixers (pressure or electrokinetic) generate helical flows within the microchannel to augment the mixing performance [1, 2]. These micromixers are extensively studied with respect to geometric parameters such as groove width, groove spacing, channel height etc. However, the effect of groove shape is not systematically studied with respect to mixing performance. Previous studies have focused on two or three different groove shapes, typically involving slanted grooves, asymmetric herringbone grooves and their variations. In this computational study, we analyze the effect of groove shape on micromixing performance and search for the optimal groove shape. The groove shape is parametrically represented by Bézier curves which could take any shape within a constrained plane.  The control points of Bézier curve are chosen as optimization parameters to identify the optimal groove shape which maximizes the mixing for given operating conditions. The optimal groove shape problem is studied for both pressure driven and electrokinetically driven flows in microchannel. With the assumption of thin electric double layer (EDL), electrokinetic flow is modeled using Helmholtz-Smoluchowski slip condition within a three dimensional finite-element model. The resulting optimal design generates the most favorable transverse flow structure to provide optimal mixing performance. Various parametric studies are carried out to compare the optimal groove structure with other common groove types (staggered, herringbone etc.) micromixers.

1. Stroock AD, Dertinger SKW, Ajdari A, Mezic I, Stone HA, Whitesides GM. Chaotic mixer for microchannels. Science. 2002 JAN 25;295(5555):647-51.

2. Johnson TJ, Ross D, Locascio LE. Rapid microfluidic mixing. Anal Chem. 2002 JAN 1;74(1):45-51.