Wicking fingering in electrospun membranes

Area of Science:

• Materials Science
• Fluid Dynamics
• Transport Phenomena

Background:

• In-plane wicking in thin, aligned electrospun fibrous membranes exhibits pronounced waterfront fingering.
• This phenomenon is hypothesized to originate from capillary pressure perturbations triggering non-local growth based on the waterfront gradient.

Purpose of the Study:

• To investigate the mechanisms behind waterfront fingering during in-plane wicking in electrospun membranes.
• To analyze the influence of fiber alignment and orientation on wicking behavior and fingering patterns.

Main Methods:

• Experimental study of vertical and horizontal wicking in poly(ethylene-co-vinyl alcohol) (EVOH) membranes using backlight photography.
• Development of a non-local transport model incorporating waterfront gradient and fiber orientation modeled as a correlated random field.

Main Results:

• Experimental observations confirmed a transition from straight to highly fingered waterfronts during water uptake.
• The developed model successfully replicated the observed fingering behavior, with finger size and shape dependent on fiber orientation.
• Model-experiment agreement validates the proposed mechanism for fingering onset and growth.

Conclusions:

• Waterfront fingering in thin electrospun membranes is initiated by capillary pressure perturbations.
• These perturbations arise from the anisotropic and heterogeneous structure of the membrane.
• Fingering growth is a non-local process dependent on the waterfront gradient and influenced by fiber orientation.