To integrate efficient mixing functions inside small chips with variable Reynolds numbers， this study developed a strategy for designing micromixers by increasing the concentration difference through matching contact surfaces based on Fick's law and Einstein's equation for Brownian motion. Subsequently， the Coanda effect was extended by analyzing the flow direction of the fluid over the channel surface and abstracting four functions from specific microchannel modules. These functions were used to predict and modulate the concentration gradient and construct the micromixer. Two three-dimensional structures of passive micromixers were designed using four functional modules to rotate and adjust the fluid interface. A three-dimensional Navier-Stokes system of equations was used for numerical analysis， and a micromixer was constructed via soft lithography for experimental verification. The experimental and simulation results showed that the designed micromixer consistently exhibits a mixing efficiency of 94%-99% at 3.3 mm， which is 22 times the hydraulic diameter length， for Reynolds numbers ranging from 0.1 to 100. This demonstrates a clear advantage over existing methods at an equal hydraulic diameter. Furthermore， the structure is easy to integrate on a chip， indicating the superiority of the modular design.