Superhydrophobic Veneers: Surface Coatings Inspired by Nature

Vanderbilt University, Nashville TN

Investigators

Abstract

1134509 Jennings Superhydrophobic surfaces combine intrinsic hydrophobicity with microscale roughness and have a broad array of potential applications in self-cleaning surfaces, corrosion resistance, water repellency, and reduced drag. Applications of superhydrophobic surfaces could be greatly expanded into the area of coatings by the development of simpler, less costly methods to prepare these materials from initially smooth substrates and the development of stable surfaces that maintain the so-called "Cassie" state where an interlayer of air exists over most of the coating/aqueous interface and imparts remarkable properties to the surface. While superhydrophobic surfaces are abundant in Nature, approaches to truly replicate natural surfaces have generally produced hand-held elastomeric materials but not surface coatings. The ability to replicate highly evolved and functional natural surfaces onto a substrate could revolutionize the fabrication of superhydrophobic coatings, leading to unique materials architectures and compositions that fuse the best of the natural and synthetic worlds. Intellectual Merit: This project introduces a new approach to replicate Nature's engineered, microscopically rough, and highly functional surfaces onto a solid substrate through surface initiated polymerization. In this approach, the microscale features of a mold prepared from a natural surface are filled with monomer. When the monomer-filled mold is pressed against an initiated substrate, the microscale features of the mold function to confine a surface-initiated polymerization so that the growing, tethered polymer chains fill the microfeatures of the mold,thereby replicating the natural surface. This approach offers a limitless supply of coating topographies through Nature and a near-boundless array of materials compositions through synthetic chemistry (well beyond those in Nature) to generate superhydrophobic coatings with novel architectures and structures. The project also introduces new materials compositions and structures through surface-initiated polymerization, including the use of superhydrophobic veneers atop initially smooth polymer films to provide multi-functional coatings. The broad objectives of the project are as follows: 1. Investigate the growth of SH polymer films as veneers atop smooth polymer films to provide uniquely layered coatings. 2. Develop a novel surface-initiated method to replicate SH coatings in Nature onto solid substrates. Broader Impacts: This project will develop new surface coatings with varied compositions and unique biomimetic architectures that replicate those of highly evolved natural surfaces to impact such applications as self-cleaning windows, corrosion and wear protection, and water collection in dry environments. The project will integrate research and education through the PI's classroom activities and his mentoring of undergraduate research students, as well as his strong commitment to outreach for K-12 students. For undergraduate researchers, this project extends the lab into the outside world, as Nature's unique surfaces are identified, collected, and replicated as coatings. The PI will continue to offer an intensive week-long course on nanotechnology to gifted rising eighth graders through the Vanderbilt Summer Academy with a special laboratory component on the replication of natural surfaces. The PI will continue to host a high school teacher in his laboratory through an on-campus NSF-funded Research Experiences for Teachers (RET) program.