Micromixers active mixers

An active mixer based on an oscillating EOF induced by sinusoidal voltage ( 100 Hz, 100 V/mm) was devised and modeled for mixing of fluorescein with electrolyte solutions. This is termed as electrokinetic-instability micromixing, which is essentially a flow fluctuation phenomenon created by rapidly reversing the flow. Various microchips materials (PDMS, PMMA, and glass) and various electrolytes (borate, HEPES buffers) have been used to evaluate this method of micromixing [480]. 

The term active mixer or active micromixer refers to a microfluidic device in which species mixing is enhanced by the application of some form of external energy disturbance. Typically, this disturbance is generated either by moving... 

The term active mixer or active microimxef refers to a microfluidic device in which species mixing is enhanced by the application of some form of external energy disturbance. Typically, this disturbance is generated either by moving components within the micromixer itself, e.g. magnetically-actuated stirrers, or by the application of an external force field, e. g. pressure, ultrasound, acoustic, electrohydrodynamic, electrokinetic, dielectrophoretic, magneto-hydrodynamic, thermal, and so forth [1]. 

Microfluidic-based mixers allow ultrafast reactions to take place in the kinetically limited regime by achieving faster mixing, which is usually obtained by a complex coupling of increases in the advective flux and interfacial area. The micromixers that have been developed can be categorized into active and passive mixers. 

In contrast to the presented passive mixers, active micromixers rely on external power input to introduce perturbations within the laminar flow to accelerate mixing. A selection of different external perturbation sources are summarized in Table 4.1 and are discussed briefed here. 

A detailed list of these mixers, their mixing principles and operating conditions can be found in recent reviews by Nguyen and Wu [5], Squires and Quake [6] and more specifically by Hessel et al. [7] and in the next chapter of the present book. Almost every laboratory and company active in this field has proposed its own, or several, mixer(s). Because of the high number of mixers and of the lack of one standard performance quantification method, it is difficult for the user to compare and to choose between the different micromixers according to a specific purpose. 

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