Superhydrophilic conformal polydopamine coating on nanostructured surface formed by capillary-induced solution infusion

Abstract

As a material-independent adhesive coating agent with excellent functionality on interfaces of materials, polydopamine (PDA) has been widely applicable in bioengineering, environment, and energy fields. Conventional coating methods using dopamine (DA) solutions suffer from slow deposition rates, hindering the attainment of adequate thickness and durability. This work introduces a technique involving rapid capillary-induced solution infusion and in-air polymerization to overcome these limitations. By immersing nanostructured surfaces for just 10 seconds into the solution, the DA solution is uniformly infused onto the surface, and distributed evenly over the nanostructured surfaces. Polymerization is facilitated by oxygen diffusion from the air, resulting in the formation of a conformal coating up to a micrometer thick. These PDA coatings exhibit persistent superhydrophilicity with water contact angles below 10° and maintain resistance to abrasion, sonication, and oil fouling. Additionally, when applied to microfiber textiles, the PDA coating leads to excellent underwater oil repellency. Our method holds promise for compatibility with various wet-based coating techniques such as drop casting, spraying, spin coating, or ink-jet printing, opening avenues for versatile applications in diverse fields.