Study of the mixing mechanism of two miscible liquids via visualization and microPIV methodology

Laboratory of physical measurement, Institute for Nanomaterials, Advanced Technology and Innovation, Bendlova 1409/7, Liberec, Czech Republic

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Published online: 12 March 2026

Abstract

Reducing the channel dimensions within microfluidic systems enhances mass transfer efficiency and enables precise regulation of concentration gradients. A fundamental function of microfluidic devices is the mixing of miscible liquids. One proposed mechanism for liquid mixing in such systems is diffusion, which is predicated on the assumption that, given the low Reynolds numbers and laminar flow conditions typical of microfluidic environments, turbulence does not facilitate mixing. Nonetheless, the mixing efficiency observed is often significant and can be further augmented through the implementation of optimized geometric configurations. The primary methodology employed to assess liquid mixing efficacy involves visualization techniques, such as the use of dyed solutions. However, the visualized outcomes do not directly correlate with theoretical calculations of mixing time based on diffusion processes. This study focuses on the confluence of liquids within a Y-branch microchannel. Utilizing visualization methodologies and the micro–Particle Image Velocimetry (micro-PIV) technique, we aim to elucidate the parameters that influence and optimize effective mixing within this geometric configuration.