Interplay of wall reactivity and viscoelasticity governs solute dispersion in microcapillary flows

Abstract

Abstract Controlling solute transport in microcapillaries is central to the intersection of microfluidic and biomedical technologies yet predicting dispersion in viscoelastic flows with reactive surfaces remains elusive. Here, we present a first-of-its-kind analytical framework that captures the coupled effects of non-Newtonian fluid elasticity, shear-thinning and surface adsorption–desorption kinetics on solute dispersion within cylindrical microcapillaries. Leveraging the Phan–Thien–Tanner (PTT) model for viscoelastic flow and employing the method of moments alongside multiple-scale analysis, we derive closed-form expressions for axial dispersion and advection coefficients, bypassing the need for computationally expensive simulations. Our model accounts for reversible solute interactions at reactive walls, revealing how key parameters such as Deborah number, reaction kinetics and molecular diffusivity orchestrate the resulting transport phenomena. The analysis not only unravels the subtle interplay between fluid rheology and surface chemistry towards dictating the resulting dispersion characteristics, but also provides key insights for the rational design and optimization of next-generation microfluidic and biomedical systems, enabling precise control over solute transport in micro-confined geometries.