A novel design for passive misscromixers based on topology optimization method

Abstract

In this paper, a series of novel passive micromixers, called topological micromixers with reversed flow (TMRFX), are proposed. The reversed flow in the microchannels can enhance chaotic advection and produce better mixing performance. Therefore the maximum of reversed flow is chosen as the objective function of the topology optimization problem. Because the square-wave unit is easier to fabricate and have better mixing performance than many other serpentine micromixers, square-wave structure becomes the original geometry structure. By simulating analysis, the series of TMRFX, namely TMRF, TMRF0.75, TMRF0.5, TMRF0.25, mix better than the square-wave micromixer at various Reynolds numbers (Re), but pressure drops of TMRFX are much higher. Lots of intensive numerical simulations are conducted to prove that TMRF and TMRF0.75 have remarkable advantages on mixing over other micromixers at various Re. The mixing performance of TMRF0.75 is similar to TMRF's. What's more, TMRF have a larger pressure drop than TMRF0.75, which means that TMRF have taken more energy than TMRF0.75. For a wide range of Re (Re ≤ 0.1 and Re ≥ 10), TMRF0.75 delivers a great performance and the mixing efficiency is greater than 95 %. Even in the range of 0.1-10 for the Re, the mixing efficiency of TMRF0.75 is higher than 85 %.

A Review of Topology Optimisation for Fluid-Based Problems

“…Oh et al [100] used the Navier-Stokes and a convection-diffusion equation to model and optimise the osmotic permeate flux over a membrane wall. Chen and Li [101] optimised micromixers under the assumption that reverse flow structures [8] inserted in a microchannel increases the mixing. Hyun et al [102] designed repeating units for sorting particles using principles in deterministic lateral displacement.…”

A Review on Micromixers

“…The optimal parameters (a 1 :a 2 :b = 5:6:4) for the ellipse were investigated with a high mixing efficiency of >80%, which was better than that of the T-channel mixer ( Figure 15 c). Recently, several convergence–divergence based micromixers, which were transformed from the typical two-dimensional serpentine channel and based on topology optimization method, were reported by Chen and Li [ 105 ]. In these micromixers, convergence-divergence structures were set at the center of the channel with the obstacles at different height ( Figure 15 d), The results showed that the micromixer with the ratio of the height of the convergence-divergence structure to that of the channel of 0.75 had the best mixing efficiency of over 95% for a wide range of Re ( Re ≥ 5 or Re ≤ 0.5).…”

Mixing Optimization in Grooved Serpentine Microchannels

“…Passive strategies, on the other hand, rely on the channel geometry-fluid interaction to induce transversal flows that stretch the interface between the fluids components to be mixed, and advection, mimicking macroscale turbulence [17][18][19]. Arrays of obstacles [28][29][30][31], ridge-groove systems [32][33][34], two-or three-dimensional turns [35,36], and curved channel sections [17,37,38] have been successfully used to exploit the already existent pressure differentials necessary to push the fluids of interest along the microfluidic device, in order to generate cross-sectional flows capable of stretching, folding, and splitting fluid elements conducive to efficient mixing. Aside from a proven ability to reach the necessary mixing quality, passive designs benefit from being accessible to a variety of fabrication methods including soft lithography [39,40], 3D printing [41], and molecular imprinting [42].…”