Fluid Movement
Fluid movement through the narrow interstitial spaces of a porous material is driven by surface tension and intermolecular forces. Dynamic capillary suction determines the rate at which moisture spreads across a fabric surface during wear.
Wicking Mechanism
When a liquid contacts the yarn surface, the pressure differential between the atmosphere and the curved meniscus inside the fibre lumen pulls fluid along the longitudinal axis. Since capillary suction increases as the pore diameter decreases, fine microfibres often exhibit faster transport than coarse yarns. High surface energy on the polymer surface promotes this effect, while hydrophobic finishes like wax or silicone suppress it.
The internal geometry of the yarn, including the twist level and the packing density of individual filaments, dictates the volume of liquid the structure can hold. Dense packing creates smaller voids that generate higher tension but may restrict the total flow volume.
Testing Protocol
Evaluation of this property occurs via vertical wicking tests where one end of a fabric strip is immersed in distilled water. The distance the liquid travels over a fixed time interval provides a metric for the efficiency of the capillary suction occurring within the knit or weave. Standards such as AATCC 197 define these measurement parameters.
Moisture Management
Performance apparel relies on these forces to move perspiration away from the skin toward the outer layer of the garment for evaporation. Engineering the yarn cross section to create more channels enhances the natural capillary suction of the structure. Efficient fluid transfer prevents the buildup of clammy moisture against the body.
