Assessment of Micromixer Design in Microfluidic Chips via Mixing Efficiency Measurement Using Contactless Conductivity Detection

D) for the precise benchmarking of microfluidic mixer designs. Using wrap-around electrodes, the platform measures the cross-sectional average mixing state at multiple locations along the microchannel, thereby eliminating errors associated with focal plane selection in optical methods. With instantaneous acid-base neutralization as a standardized model, the mixing process is decoupled from reaction kinetics, ensuring measured signals accurately reflect the structural performance of the micromixer. Evaluations across various geometries demonstrate that periodic convergent-divergent sections generate a "stretching-folding" flow field, overcoming diffusion limitations and yielding a mixing index above 90% within 0.24 s. This work provides a robust, direct methodology for the quantitative assessment and rational structural design of high-performance microreactors.