Lin and Yang. Soft Matter. 2009, 5 , 1011-1018

1. CAREER: Selective Grafting of Responsive Polymer Brushes on Topographically Structured Surfaces: A New Route for Surface and Interface Manipulation Shu Yang, University of Pennsylvania, DMR 0548070 • A major goal of this research is to combine the chemical heterogeneity and surface topography by selectively grafting responsive polymer brushes on different parts of a nanostructured surface to spatially control surface wettability and transition in response to a small change of environment. • We demonstrate reversibly tunable wetting and dry adhesion on a rippled PDMS film by regulating the micro-scale surface roughness via mechanical strain. To promote the surface wetting into Cassie’s region and test importance of dual roughness, we integrate nanoparticles into the rippled system to generate dual-scale roughness. The inclusion of superhydrophobicity within the tunable range of wetting behaviors allows us to dynamically switch the flow resistance (droplet “move” or “stick”) on wrinkled PDMS, which potentially could lead to a broad range of engineering applications, such as microfluidic valves and mixers, anti-fouling, and manipulation of cell transport. • We fabricated a strain responsive wrinkled surface based on buckling of a bilayer of hard oxide on soft poly(dimethylsiloxane) (PDMS). By decorating silica nanoparticles on the wrinkled surface, we elucidate the importance of dual roughness to wetting and flow resistance. • Left figure: SEM and AFM images of a PDMS film with dual-scale roughness and real-time, reversible tunability of its surface topography by mechanical strain. Inset: contact angles at corresponding roughness. Lin and Yang. Soft Matter. 2009, 5, 1011-1018

2. CAREER: Selective Grafting of Responsive Polymer Brushes on Topographically Structured Surfaces: A New Route for Surface and Interface ManipulationShu Yang, University of Pennsylvania, DMR 0548070 • Education at Graduate and Undergraduate Levels: • Three Ph.D. students have learned about the nano- and microfabrication of structured polymers, and synthesis and characterization of polymer brushes. One senior graduated has graduated and start a new career as postdoc fellow at Organic Technology, S&T Division, Corning Inc • At the undergraduate level, the PI has supervised 3 REU students (one partially supported by CAREER/REU and two from MRSEC/REU) last summer working on wetting and pattern transfermation. The results from Jason Reed, who is partially supported on CAREER/REU, have been presented at ACS 2009 Spring meeting, POLY division. • PI has supervised 5 senior design students on tunable wetting on wrinkled surfaces. • Outreach for K-12 Education: • the PI has given lectures to • the Philadelphia region high school teachers on “Materials Patterning: from Micro- to Nanoscale” in March 2009, and • high school students (grades 10-12) through MAGPI Frontiers of Material Science videoconference event in April 2009 through Penn MRSEC. MAGPI (Mid-Atlantic Gigapop in Philadelphia for Internet2) is a multi-state regional GigaPoP, involving institutions from New Jersey, Pennsylvania and Delaware. Following her students’ demonstrations, the PI discussed the mechanism of each hydrogel formation and their new applications to nanotechnology through Q/A session with students. http://www.magpi.net/programs/lrsm.html