Numerical and experimental characterization of a novel modular passive micromixer

Abstract

This paper reports a new low-cost passive microfluidic mixer design, based on a replication of identical mixing units composed of microchannels with variable curvature (clothoid) geometry. The micromixer presents a compact and modular architecture that can be easily fabricated using a simple and reliable fabrication process. The particular clothoid-based geometry enhances the mixing by inducing transversal secondary flows and recirculation effects. The role of the relevant fluid mechanics mechanisms promoting the mixing in this geometry were analysed using computational fluid dynamics (CFD) for Reynolds numbers ranging from 1 to 110. A measure of mixing potency was quantitatively evaluated by calculating mixing efficiency, while a measure of particle dispersion was assessed through the lacunarity index. The results show that the secondary flow arrangement and recirculation effects are able to provide a mixing efficiency equal to 80 % at Reynolds number above 70. In addition, the analysis of particles distribution promotes the lacunarity as powerful tool to quantify the dispersion of fluid particles and, in turn, the overall mixing. On fabricated micromixer prototypes the microscopic-Laser-Induced-Fluorescence (μLIF) technique was applied to characterize mixing. The experimental results confirmed the mixing potency of the microdevice.

The effect of chaotic advection on mixing degree and pressure drop of non-Newtonian fluids flow in curved micromixers

“…As the Reynolds number increases, the strength of secondary flows increases and mixing index becomes greater. Similar trends were reported by several researchers for Newtonian fluids [5,20,30] and by Afzal and Kim [1] for Carreau-Yasuda model of non-Newtonian fluids. In addition, by decreasing the power-law index and consequently increasing of apparent viscosity, the chaotic advection effect is weakened by viscous forces and as a result the degree of mixing decreases.…”

“…In addition, they reported that among the studied cases, the full three-stream (FTS)-CSC micromixer is more appropriate. Pennella et al [20] studied mixing efficiency of a novel configuration of split and recombination micromixer with curved segments, both experimentally and computationally. They investigated flows at Reynolds number between 10 and 110 and found that secondary flows and recirculation effect can be able to promote mixing performance.…”

Microfluidic Approaches for the Assessment of Blood Cell Trauma: A Focus on Thrombotic Risk in Mechanical Circulatory Support Devices

“…The shearing channels are characterized by a constant height (50 μm) and a varying width (ranging from 15 to 120 μm) and have a total priming volume of about 1 μL The whole platform can be perfused with about 200 μL of platelets. The design of the mixing sub-unit was optimized by means of numerical modeling, in terms of channel length and number of repeating herringbone structures, as previously reported (78).…”

A novel passive micromixer with modified asymmetric lateral wall structures

“…Passive mixing behavior typically relies on diversified microchannel structural design for fluid flow guiding along the wall and distortion to obtain the desired mixing performance . Hence, the improvement and optimization of the passive micromixer structure have always been the focus of research; a variety of passive micromixers with diverse structures have been implemented …”