New wicking measurement system to mimic human sweating phenomena with continuous microfluidic flow

Typical liquid moisture management property tests of textiles may not represent human sweating from sweat pores because those methods are conducted with infinite reservoirs or limited, but large amounts of liquid. For this reason, we developed a new method, ‘single-pore wicking evolution apparatus for textiles (SWEAT),’ to investigate how liquid is transported in fabrics based on within-a-yarn and yarn-to-yarn transfer wicking. This measurement system was implemented by supplying continuous liquid flow to a single yarn at a single point within the fabric substrate at a similar flow rate to a single sweat gland (approximately 50 nl/min/gland). In order to mimic the sweating phenomenon, this SWEAT test avoids the flooding liquid stage by controlling flow rate and choosing a diameter of liquid source similar to the pore size of a sweat gland. From microscopic video analysis, we found that the liquid moves along the yarns instead of making a circular wetting area, as observed in standardized tests. With the SWEAT test, we successfully measured the directional wicking rate along an individual yarn, which has not previously been reported. Furthermore, we examined not only liquid movement within-a-yarn but also yarn-to-yarn transfer of liquid because the continuously supplied liquid spills over to the adjacent yarns through the contact points.