Graduate SeminarsDr. Robert E. Cohen St. Laurent Professor of Chemical Engineering Massachusetts Institute of Technology
Friday, APRIL 3, 2009 - 9:30 am 1175 Benedum Hall
"Designing Robust Omniphobic Surfaces" Superhydrophobic surfaces that display water contact angles greater than 150o with low contact angle hysteresis are becoming commonplace in the materials community. Microscopic pockets of air trapped beneath the high surface tension (γlv = 72mN/m) water droplets lead to a composite solid-liquid-air interface in thermodynamic equilibrium. Previous experimental and theoretical work suggests that it should not be possible to form similar fully-equilibrated composite interfaces with drops of low surface tension liquids such as alcohols or alkanes (e.g. pentane: (γlv = 16 mN/m). In this lecture I will discuss novel surfaces that possess the required re-entrant topographical texture and surface chemistry to support strongly metastable composite solid-liquid-air interfaces for any liquid. Quantitative design parameters will be introduced to guide the development of these novel omniphobic surfaces. Examples that have been realized to date will be demonstrated: these embodiments include lithographically fabricated microhoodoos in silicon, randomly deposited electrospun fiber mats and dip-coated textiles.
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