Characterization of Permeability of Electrospun Yarns

Abstract

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.

Design of Nanofibrous and Microfibrous Channels for Fast Capillary Flow

“…Capillary flow exists in numerous applications including microfluidic diagnostics, microscale molding and manufacturing, thermal management, functional fabrics, and oil–water separation. − The speed of capillary flow is often a bottleneck in further advancing these functionalities, especially in nanoscale and microscale fluidic devices and systems. For example, it is desirable to speed up the capillary flow in lab-on-a-chip devices to control timing of sequential reactions.…”

Paradox of the drinking-straw model of the butterfly proboscis

“…This pressure, P p , could not be measured. However, we could estimate the pressure at the meniscus moving in the capillary tube, knowing the contact angle θ determined from Jurin's experiments (Jurin, 1917(Jurin, -1919, as previously discussed for this geometry (Tsai and Kornev, 2013), surface tension σ of the liquid and radius r of the capillary tube. The driving capillary pressure:…”

“…thus was obtained independently (Tsai and Kornev, 2013). Once the driving capillary pressure was known, the problem of determining proboscis permeability was reduced to the problem of liquid flow through a composite conduit consisting of two tubes connected in a sequence (Tsai and Kornev, 2013).…”

“…Once the driving capillary pressure was known, the problem of determining proboscis permeability was reduced to the problem of liquid flow through a composite conduit consisting of two tubes connected in a sequence (Tsai and Kornev, 2013). When a conduit has a fixed length and the pressure differential is applied to the ends of this conduit, the flow description is reduced to the Cohn-Rashevsky method of design of some parts of the cardiovascular system (Cohn, 1954;Cohn, 1955;Rashevsky, 1960).…”

“…The dynamics of meniscus propagation, however, depend only on a single dimensionless complex. It is convenient to introduce the Jurin height, Z c =2σcosθ/(ρgr), where ρ is the liquid density and g is acceleration due to gravity (Jurin, 1917(Jurin, -1919Lehnert et al, 2013;Tsai and Kornev, 2013); this is the maximum height that the Eqn 5 is the Lucas-Washburn equation describing capillary rise in tubes (Lucas, 1918;Washburn, 1921), which has the solution:…”