A micromixer is an important component of microfluidic systems, which reveals wide and essential applications in the field of chemistry and biochemistry. In the micro scale, diffusive mixing is notoriously slow as fluid is in the form of laminar flow. Therefore, design of a high performance micromixer to mix fluids at short distance is essential for a successful development of microfluidic systems. A novel three-dimensional micromixer, which composed of several units of three dimensional asymmetric arc structures, was proposed. Mixing experiments and numerical studies were carried out and the experimental results showed a good agreement with the simulation results. For the normal fluid (viscosity is 9.7×10−4 kg/ms and diffusivity is 3.6×10−10 m2/s), the complete mixing lengths are less than 2 mm at the inlet velocity from 1.9×10−4m/s to 2.9 m/s. The complete mixing length gradually increases from 350μm to 2000μm when inlet velocity increases from 1.9×10−4 m/s to 1.9×10−2 m/s. However, the complete mixing length decreases to 700 μm while the inlet velocity continues increasing to 2.9m/s. The inlet velocity of 1.9×10−2 m/s is considered as a critical inlet velocity, where more chaotic advection occurs to enhance the mixing performance and reduce the complete mixing length when the inlet velocity is bigger than the critical value. For the fluid with viscosity of 0.186 kg/ms and diffusion rate of 9×10−13m2/s, no chaotic advection occurs and the complete mixing lengths are around 2200μm at the inlet velocity from 3.7×10−3m/s to 3.7m/s. The results show that this novel micromixer has extremely short mixing length even for difficult mixing fluids.

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