Theoretical investigation on wicking behavior and saturation distribution in single and perpendicularly interlaced yarns

Capillary wicking in yarns is a dominant factor governing textiles’ heat-moisture comfort, medical dressing liquid transport, and technical textile mass transfer functionality. Classical Lucas-Washburn equation and Darcy’s law, rooted in the uniform pore size assumption, fail to accurately describe liquid transport in yarns’ heterogeneous capillary networks; meanwhile, the mass transfer mechanism at interlaced yarn interfaces remains poorly understood, hindering cross-scale wicking prediction from single yarns to fabrics. Here, we establish a series-connected thick-thin tube heterogeneous capillary model, and derive a coupled theoretical model for wicking kinetics and saturation distribution in single and perpendicularly interlaced yarns. We analyze six key structural parameters’ regulation effects via Comsol, validate the model with single-yarn wicking tests, reveal interlacing structure’s influence via 12 groups of experiments, and extend the model to interlaced systems using an analogy method with two proposed equivalent characteristic parameters. Results show wicking performance is positively correlated with thin-to-thick tube length ratio n, radius ratio m, equivalent capillary radius R, porosity φ, pore size distribution index λ, and negatively correlated with total tube segment number N; reduced interlacing angle and increased intersection height synergistically aggravate interfacial pore collapse and flow resistance, with horizontal yarns exhibiting poorer wicking due to combined compression-bending deformations. The model is further extended to plain woven fabric scale, and fabric-scale simulations confirm the stable existence of interlacing-induced transport anisotropy and saturation discontinuity at yarn-yarn interfaces, verifying its full cross-scale prediction capability from single yarns to fabrics. This work breaks classical wicking theory limitations, providing theoretical support for structure-oriented design of functional moisture-wicking textiles.