Mushroom-shaped microfiber array by electrohydrodynamic structuring process for superhydrophobicity

Bioinspired mushroom-shaped microfiber arrayed surface demonstrates superhydrophobicity. Such a textured surface is fabricated by an electrohydrodynamic (EHD)-based structuring process, which is a combination of hot embossing, electrically induced growing and electrowetting. First, an ordinary micropillar array is prestructured on a conductive substrate through the hot embossing process. Second, another planar plate, functioning as the upper electrode, combines the substrate and an air gap into a parallel capacitor, across which an electrical voltage is applied to generate a modulated electric field. The electrically induced Maxwell force could drive the polymer to grow towards upper electrode and spread transversely on it, forming the mushroom-shaped microfibers. Through an analysis on the early-stage kinetics of the pre-structured micropillars, we can find a suitable electrical potential to ensure the electrically-induced force is sufficient to drive the polymer growing upwards. The measured static contact angle of about 152° and contact angle hysteresis of about 11° demonstrate the superhydrophobicity of this mushroom-shaped microfiber arrayed surface.