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Fast and thorough mixing is a crucial operation of digital microfluidic devices, where discrete and small fluid portions are moved and processed. In this paper, we want to analyze and to optimize the mixing process by substituting conventional motion and superposing oscillatory and translational modes. An accurate multiphase smoothed particle hydrodynamics (SPH) discretization for incompressible flow is instantiated. Different harmonic excitation patterns for the solid–liquid surface energy are applied and their influence on droplet mode shapes, formation of eddies and the Shannon entropy of droplet fluid components are measured. We tailor enhanced actuation patterns which improve mixing grade and reduce mixing time.

The concrete mixer possesses the basic performance "mixing efficiency", and is one of the most important construction machines on the step that manufactures concrete. The bi-axial forced-mixing type of the mixer is high and the mixing efficiency is the highest. The flow patterns of this type mixer are divided into two: the locally crossing flow and the globally circulating flow. The globally circulating flow uniformly mixes fine particle materials that differ greatly the grain size turned on and are various and cement active. The locally crossing flow contributes to "Knead" to improve the contact frequency of the cement particle and water.

In the research, concrete was assumed to be a viscous model of one phase system for the model mixer of two types with different area of the locally crossing flow, the mixing efficiency curve of the model concrete of the high viscosity and the low viscosity was a process of becoming uniform with the axial rotation, and quantification was attempted. The second research tried the quantification of the crossing flow around the blade generated when two circulating flows crossed by the pressure fluctuation of the pressure sensor installed in the surface of the blade of the mixer was attempted, and the magnitude of the crossing Flow generated in the model mixer of two types and the correlation of the mixing efficiency curve were considered.

In this paper, we have designed a rhombic microchannel plane micromixer (RMPM). The RMPM uses the principle of converging and diverging to improve the mixing efficiency. We improved the mixing efficiency by changing the rhombic angles and the rhombic channel width ratios. The influence of geometric parameters on mixing efficiency is analyzed by control of the variable method. Through the analysis of the numerical simulation, the RMPM can help increase the chaotic convection between different concentrations of fluids. The results of the study show that the rhombic angle and the width ratio of a microchannel can have a considerable effect on the mixing efficiency. The micromixer can be potentially useful in the future applications of rapid and high throughput mixing.

We designed a new type of $T$-type electroosmotic micromixer with variable modules (EMVMs). By applying 7V alternating current (AC) voltage to the EMVM, the mixing efficiency at different Reynolds number (Re) is discussed by changing the rotation angles of modules at different positions in different directions. We found that the mixing efficiency of the EMVM can reach 99% when the first block is rotated along the xz-axis. Then, we change the torsion angle of the same variable module and find that the mixing efficiency can reach 99.3% when the torsion is $0^{\circ }$. Finally, we change the voltage value and find that the mixing efficiency of the EMVM increases with the increase of voltage values.

This paper investigates the effects of external excitation on the mixing performance of the micromixer with curved bluff-body structure. The micromixer was fabricated by the MEMS process of polydimethylsiloxane (PDMS). The mixing process and mixing efficiency were evaluated with a high speed camera. Results showed that the finger-spiked type flow patterns were generated in the mixing chamber under an excitation frequency of 5Hz. It turns out that the mixing efficiency as high as 85.6% is achieved at Re=0.25 with a single bluff-body structure. It demonstrates that the new design can be used to achieve complete mixing within ultra short length at mciroscale.

This paper theoretically and numerically investigates the hydraulic resistance, mixing efficiency, and comprehensive mixing and hydraulic performance characterized by the outlet mixing efficiency to hydraulic resistance ratio of the symmetric T-shaped rectangular microchannel mixer with uniform channel height. The influences of multi-parameters including width ratio of inlet channel and outlet channel, channel height, and two different inlet conditions of inlet velocity and inlet flowrate on the hydraulic and mixing performance of the micromixer are investigated. This work found that the comprehensive performance first increases and then decreases with the increasing channel width ratio of inlet channel and outlet channel, indicating the existence of an optimal channel width ratio to reach the best comprehensive mixing and hydraulic performance. This result is similar to the conclusion of classical Murray’s law and can be considered as an extension of classical Murray’s law in the field of microscale mixing. The effects of the channel height, channel length ratio and different inlet conditions on the optimal width ratio are analyzed.

In this paper, we have studied the effect of variable-angle grooves and baffles on the mixing efficiency of the micromixer. In order to explore the influence on the micromixer with different types of grooves and baffles, we designed grooves and baffles with different geometric parameters and placed them in T-channels to interfere with fluid flow. We studied VAM30^∘ (variable-angle grooves and baffles micromixer with an angle of 30^∘) directions and distributions as well as their different groove depths and baffle heights affect the mixing performance. We tried to divide the grooves and baffles into five groups, and discussed the effects of staggered depth and height on mixing efficiency. The mixing efficiencies of micromixer in the Re (Reynolds number) range of 0.1–100 were calculated, and the fluid flow in the microchannel was analyzed. The simulation results show that VAM30^∘ is more favorable for solution mixing. The mixing efficiency of the micromixer could reach 98.9% with the change of different geometric parameters. This is because when the structure changes, the flow state of the fluid is improved, which is conducive to lengthening the residence time of the fluid in the channel. With the increase of Re, it is also conducive to enhancing the chaotic convection and improving the mixing efficiency.

In this paper, we mainly study the mixing performance of the micromixer with quartic Koch curve fractal (MQKCF) by numerical simulation. Changing the structure of the microchannel based on the fractal principle can significantly improve the fluid flow state in the microchannel and improve the mixing efficiency of the micromixer. This paper discussed the effects of different fractal deflection angles, microchannel heights and different fractal times on the mixing efficiency under four different Reynolds numbers (Re). It is found that changing the deflection angle of the fractal can bring extremely high benefits, which makes the fluid deflect and fold in the microchannel, enhancing the chaotic convection in the microchannel, and improve the mixing efficiency of the fluid. Under the reasonable arrangement of the quartic Koch curve fractal principle, it can give the micro-mixture more than 99% mixing efficiency. Based on the excellent mixing performance of MQKCF, it also has extremely high application value in the biochemical neighborhood.

We mainly studied the mixing performance of three new T-type electroosmotic micromixers (T-EMs). The three T-EMs are designed as rhomboids with three different shapes of obstructions inside. The rhomboid micromixers utilize the principle of convergence and divergence to improve mixing efficiency. By changing the Reynolds number (Re), the change of mixing efficiency under direct current (DC) voltage 20V and alternating current (AC) voltage 2mV was observed. We changed the shape of the intermediate obstacles, discussed the shape of the internal barrier on the mixing efficiency of T-EM, and increased the mixing efficiency by increasing the voltage value. The mixing efficiency of T-EM with 150$\mu$m channel width can reach 97.5% under DC condition and 97.6% with circular barrier under AC condition.