Decoupling Wetting from Swelling in Electrospun Fibrous Mats: Predicting Saturation Time, Swelling Time, and Dimensional Change from Solubility Parameters

A closed gate instead imposes a 14 kPa intrusion pressure; the mat stays dry unless the interior drive is favorable, in which case it resists a droplet yet imbibes once entry has occurred. Fiber swelling completes within 10² s, and a jamming argument closes the dimensional-change problem, giving a porosity linear in the fiber swelling ratio and an exact decomposition of gravimetric uptake into network and void terms.

Against published data, a cellulose acetate (CA) mat-and-film pair returns a mat porosity of 0.90 with no adjustable parameter, and a cross-linked poly(vinyl alcohol) (PVA) series a monotonic cross-link density reproducing the reported cross-linker ranking. A swelling ratio reported without the dry porosity is not interpretable: for one hydrophilic mat, 54% of the uptake is capillary water between the fibers, not water in the polymer.

Two independent datasets test the two branches separately: the wetting gate against poly(ε-caprolactone) (PCL) mats that absorb a water droplet completely despite an apparent contact angle of 137.9°, and the Kozeny–Carman baseline against absolute permeability measurements on poly(lactic acid) (PLA) scaffolds several times coarser in fiber diameter. The framework applies unmodified to microfluidic and tissue-engineering scaffolds as well as to wound dressings, drug-releasing membranes, separators and filtration media.