Characterization of permeability of electrospun yarns.

We developed a novel technique enabling determination of the permeability of electrospun yarns composed of hundreds of fibers. Analyzing the wicking kinetics in a yarn-in-a-tube composite conduit, it was found that the kinetic is very specific. The liquid was pulled by the capillary pressure associated with the meniscus in the tube while the main resistance comes from the yarn. Therefore, one can separate the yarn permeability from the capillary pressure, which cannot be done in wicking experiments with single yarns. A surface tensiometer (Cahn) was employed to collect the data on wicking kinetics of hexadecane into the yarn-in-a-tube conduits. Yarns from different polymers and blends were electrospun and characterized using the proposed protocol. We showed that the permeability of electrospun yarns can be varied in a broad range from 10(-14) m(2) to 10(-12) m(2) by changing the fiber diameter and packing density. These results offer new applications of electrospun yarns as flexible micro- and nanofluidic systems.