Numerical and experimental mixing studies in a MEMS-based multilaminated/elongational flow micromixer

Abstract

Improvement of mixing quality in microchannel mixers or reactors has been recognized as a relevant technical issue critical to the development and application of integrated microchemical processing systems. Silicon micro- electro mechanical systems (MEMS) technology was successfully used to fabricate a novel multichannel micromixer. This improved micromixer design basically used the mechanisms of fluid multilamination, elongational flow, and geometric focusing for mixing enhancement. The fabricated triple-stack (Pyrex™/silicon/Pyrex™) multilaminated/elongational flow micromixer (herein referred to as MEFM-4) was evaluated for its mixing performance using residence time distribution (RTD) measure in conjunction with UV–vis absorption spectroscopy detection technique. Using a semi-empirical model and the so-called convolution–deconvolution theorem, a model description of the experimental RTD data was obtained for the flow/mixing unit. This result was compared with numerical RTD predictions based on computational fluid dynamics (CFD) simulations. The simulation results are in good agreement with the experimental data, especially in the low flow-rate range (Reynolds number <13 in this study). However, as expected, the accuracy of the CFD simulations is generally limited at higher flow rates (high Peclet number) because of unavoidable numerical diffusion. This paper describes the efficient design, fabrication and characterization of an effective microchannel mixer for microchemical systems’ applications.