A deep dive into hydrodynamic dispersion in microfluidic systems

Hydrodynamic dispersion of solutes is a pivotal phenomenon in microfluidic systems, wherein the axial spreading of various dissolved species-including ions, chemical compounds, biomolecules, dyes, pharmaceuticals, and nanoparticles-occurs due to the coupled effects of molecular diffusion and the non-uniform velocity profiles inherent to confined laminar flows. Given its profound impact on a broad range of applications-spanning analytical, diagnostic, bioengineering, pharmaceutical, environmental, and chemical processing systems-mastering the mechanisms of dispersion is crucial for enhancing separation efficiency, reproducibility, reaction performance, and analytical throughput, while minimizing sample volume, energy consumption, and undesired side effects. This comprehensive review provides a structured synthesis of the fundamental concepts, historical development, and governing mechanisms underlying Taylor-Aris dispersion in micro- and nanofluidic systems. Special emphasis is placed on the role of flow profile design, channel cross-sectional geometry, and surface physicochemical properties in modulating dispersion intensity. Through a systematic analysis of analytical, numerical, and experimental studies conducted from 2000 to 2025, we identify prevailing challenges, unresolved questions, and methodological gaps in the literature. Notably, this work addresses a key void by offering the first coherent classification that concurrently explores the mechanistic origins and engineering control strategies of hydrodynamic dispersion across diverse operating regimes. By bridging classical theories with emerging microfluidic architectures, this article not only deepens the understanding of dispersion phenomena but also lays the foundation for future innovations in colloid and interface science. As such, it provides an essential resource for researchers aiming to optimize transport, separation, and energy conversion processes in advanced fluidic systems.