Abstract
Microfluidic mixing becomes a necessity when thorough sample homogenization is required in small volumes of fluid, such as in lab-on-a-chip devices. For example, efficient mixing is extraordinarily challenging in capillary-filling microfluidic devices and in microchambers with stagnant fluids. To address this issue, specifically designed geometrical features can enhance the effect of diffusion and provide efficient mixing by inducing chaotic fluid flow. This scheme is known as “passive” mixing. In addition, when rapid and global mixing is essential, “active” mixing can be applied by exploiting an external source. In particular, magnetic mixing (where a magnetic field acts to stimulate mixing) shows great potential for high mixing efficiency. This method generally involves magnetic beads and external (or integrated) magnets for the creation of chaotic motion in the device. However, there is still plenty of room for exploiting the potential of magnetic beads for mixing applications. Therefore, this review article focuses on the advantages of magnetic bead mixing along with recommendations on improving mixing in low Reynolds number flows (Re ≤ 1) and in stagnant fluids.
Highlights
Lab-on-a-chip (LOC) devices integrate one or more miniaturized laboratory functions on a single chip
We focus on active mixing induced by magnetic means, using magnetic beads or magnetic actuators
Dynamic behavior of superparamagnetic beads under the influence of rotating magnetic fields and its immediate effect on the surrounding fluid have been numerically and experimentally studied, not much research has been done on the collective motion of the micro stirrers and its effect on the mixing efficiency in microfluidic chambers or channels
Summary
Lab-on-a-chip (LOC) devices integrate one or more miniaturized laboratory functions on a single chip. The efficiency and reproducibility of capturing and detecting low concentration targets is strongly dependent on the global homogeneity of the reagents within the complete sample volume [8], which a mixing enhancement method can help achieve. This type of micromixer makes use of two phenomena: molecular diffusion and chaotic advection The former happens when fluids are in contact and exchange particles or molecules. We start by discussing other means of micromixing These methods are assessed by ease and cost of fabrication, their application at a very low Re number (Re
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