Reproduction of Hierarchically Rough Surfaces via Micromolding Surface-Initiated Polymerization

Abstract

Micromolding surface-initiated polymerization (µMSIP) – a recent addition to the soft lithographic toolbox – represents a unique and powerful approach in surface fabrication. As the name suggests, this technique marries two techniques; micromolding is used to generate casts of a substrate of interest and surface-initiated polymerization (SIP) follows for reproduction of the surface architecture with a covalently bound polymer thin film. Importantly, a number of SIP approaches employ partially fluorinated materials thereby offering a route to ultralow energy surfaces with desirable properties. Previous work with this technique has been restricted to bioinspired surfaces, such as plant leaves and to several machined surfaces that were useful in assessing polymerization kinetics. The focus of this work has been extending µMSIP to new and more challenging surfaces. Novel surfaces of various types have been fabricated as substrates for molding and reproduced. Smaller feature sizes, including both micro- and nanoscale roughness, have been shown beyond those previously demonstrated. Additionally, replication of re-entrant surface geometry – indispensable for superomniphobicity – has also been achieved. Many of these films demonstrate superhydrophobicity, and some have proven superoleophobic as well. The development and expansion of µMSIP will prove invaluable not only for its many applications and unique properties, but also because it enables researchers to characterize many surfaces that would be impossible to generate with other techniques. Such research may open the door to great extensions in our understanding of the many phenomena at the surface.