In recent years,micromixer has been

In recent years,micromixer has been broadly applied in biological analysis and chemical synthesis as an important component in Lab-On a Chip (LOC) and micro-total analysis systems(μTAS)where rapid and high-efficiency mixing is required.Mixing process of two or more reagents is a critical issue for microfluidic application.The flow regime is usually laminar with low Reynolds number (Re),and the interface tension and viscous effect between two fluids play more important roles compared with inertia effect in small hydraulic diame ter channels.The scaling effects of the microchannels,such as entrance effect,surface roughness and slippage phenomena,have a significant influence on the flow stability and the transport of mass,momentum and heat in the microscale.When two species of fluids flow in the micromixer,the mixing performance mainly relies on the molecular diffusion and the mixing process is time-consuming.According to the rate of diffusive mixing characterized by DA∇C,there are three ways to increase the mass transfer in micromixers,i.e.,to improve the diffusion coefficient D,to increase the species concentration gradient ∇C and to increase the interfacial surface area A between different species of fluids.As the temperature rises up,the diffusion coefficient will increase.However,high temperature may have a strong impact on the physical properties of some reagents,which should be avoided in some practical applications.And due to the actual working conditions,it is limited to increase the gradient of species concentration.Therefore,increasing the interfacial surface area between different fluids in micromixers is considered to be an effective method to enhance the mass transfer.