Active micromixers use an external source of energy 11, 12, 13, 14, 15, 16, while passive micromixers rely entirely on diffusion or chaotic advection and do not require external energy except for a micropump for fluid delivery. Presently, micromixer designs and technologies are classified into active and passive micromixers 9, 10. Consequently, the microfluidic mixing mechanism is dominated by diffusion, which is based on the concentration gradient, a process that leads to the increment of the time and length of the mixing procedure. the viscous effects dominate inertial effects, a completely laminar flow occurs where fluid streamlines are parallel to each other and convective mass transfer occurs only in the direction of the fluid flow.

For microfluidic devices, the Reynolds number is small ( ≪100), i.e. Mixing efficiency and rapid mixing play a major role in the characterization and performance of microfluidic systems researchers have been making numerous attempts to develop a versatile and efficient mixing mechanism 8, 9, 10. Micromixers are a key component in several Lab On a Chip (LOC 1) and Micrototal Analysis Systems (μTAS), which are increasingly being used in chemical, biological and biomedical applications 2, 3, 4, 5, 6, 7. Finally, the potential diagnostic value of the presented microdevice was validated experimentally for Red Blood Cell (RBC) lysis. A mixing efficiency of almost 100% was readily reached when three serpentine units were included (3-SERP). This micromixer design including a single serpentine unit (1-SERP) displayed an efficiency higher than 90% (mixing length = 6.4 mm) creating a pressure drop of about 500 Pa at Re = 0.1 and 60 kPa at Re = 10. The experimental results showed a very good agreement with the predicted numerical results. The micromixer structure was fabricated in a simple single-step process using maskless lithography and soft lithography. The performance of the most efficient design was experimentally investigated by means of fluorescence microscopy for a range of low diffusion coefficients, 10 −12 < D < 10 −11 m 2/s. The geometrical characteristics of the presented design were analyzed numerically in the range of 0.01 < Re < 100 based on the micromixer performance.

This paper proposes a novel, simple, passive micromixer design characterized by a planar accordion-shape geometry.

Micromixers are the key component that allow lab-on-a-chip and micro total analysis systems to reach the correct level of mixing for any given process.

Accordion method half square triangles