Metastable wetting model of electrospun mats with wrinkled fibers

Abstract Electrospun mats with targeted wettability are a way forward to diversify their mainstream applications and can facilitate in creating a platform for a remarkable set of properties. Limited control over the fiber morphology and surface chemistry, along with the complex architecture of electrospun mats, pose some of the key challenges for maneuvering the wettability. Herein, we present the design principles that underpin the key determinants responsible for a metastable state of a water droplet on electrospun mats possessing wrinkled surface topography. A ‘first-of-its-kind’ analytical model of apparent contact angle based on the modified Cassie-Baxter state has been proposed that accounts for the dual-scale roughness originating from fiber wrinkles and protuberances created by fiber-fiber contacts. Three-dimensional (3D) fiber and structural parameters obtained via X-ray microcomputed tomography (microCT) analysis served as key inputs for predictive modeling. The analytical model of the apparent advancing and receding contact angles has been validated with electrospun mats having well-defined orientation characteristics. In general, the theory and experiment are in reasonable agreement. Although similar magnitudes of static and advancing contact angles were experimentally observed in randomly and aligned electrospun mats with water drops, the receding contact angles were significantly different.