One-step modification of superhydrophobic surfaces by a mussel-inspired polymer coating.

Mussels, which are promiscuous, underwater fouling organisms, attach to virtually any natural or synthetic organic/ inorganic substrate. The major components of mussels adhesive pads include proteins that contain the unusual amino acid 3,4-dihydroxy-l-phenylalanine (DOPA). In particular, Mytilus edulis foot protein-5 (Mefp-5), a protein located at a distal side of adhesive pads that attaches to opposing substrates, shows an exhaustive repeat of DOPAlysine. Recently, Lee, Messersmith, and co-workers identified dopamine that contains both side chain functionalities of DOPA and lysine and reported new surface chemical method, called polydopamine coating. Polydopamine modified a wide variety of material surfaces, including noble metals, metal oxides, ceramics, and synthetic polymers on which protein immobilization, metallization, biomineralization, and cell adhesion were demonstrated. Despite the unparalleled capability of polydopamine, the functionalization of superhydrophobic surfaces remains unexplored. Superhydrophobic surfaces have received significant attention because of their extraordinary surface properties. A great deal of effort has been made to fabricate such surfaces. The well-known biological model system of superhydrophobicity is the lotus leaf, which exhibits a static contact angle for water of greater than 1508. Most superhydrophobic surfaces have been prepared by various lithographic techniques: photolithography, e-beam lithography, assembly of colloidal particles, capillary lithography and others. The nonwetting properties of superhydrophobic surfaces have allowed a variety of applications, such as antireflectivity, self-cleaning, anti-fouling, and in a long lifetime microfluidic valves. Despite the large effort to develop methods to prepare superhydrophobic surfaces and to seek useful applications, few strategies to tailor the superhydrophobic surface properties have been developed. In particular, a facile strategy to modify superhydrophobic surfaces that can be integrated with widely implemented soft-lithographic techniques has not been achieved. Herein, we report a one-step, solution-based surface chemical method that modifies superhydrophobic surfaces (Figure 1). The surface chemistry to enable this innovation is