Wicking in textiles at rates comparable to human sweating

Abstract

To understand liquid transport mechanisms in textiles for thermal comfort, the textile field has developed standard test methods, such as vertical wicking or a droplet test. However, experience has shown that these tests can give contradictory results. Here we try to understand how liquid moves along capillary channels in textiles by simulating realistic human sweating generated from each sweat gland pore. The SWEAT test mimics realistic human sweating by supplying a continuous microfluidic flow to only a single yarn at a single point within the fabric substrate at a similar flow rate to a single sweat gland. We compare the results of typical test methods with either infinite liquid reservoirs or limited, but large amounts of liquid with those of a new test method, the SWEAT test. In the SWEAT test, we found transfer of liquid from one capillary channel to another occurred only at contact points between the yarns and not through the space between yarns. Additionally, we observed a wicking lengthtime superposition: liquid wicked within a single yarn initially, subsequently it spilled over to adjacent yarns, and the initial wicking rate in adjacent yarns was the same as the initial course yarn but with a time offset.