title: Spontaneous wettability patterning via creasing instability.
abstract: Surfaces with patterned wettability contrast are important in industrial applications such as heat transfer, water collection, and particle separation. Traditional methods of fabricating such surfaces rely on microfabrication technologies, which are only applicable to certain substrates and are difficult to scale up and implement on curved surfaces. By taking advantage of a mechanical instability on a polyurethane elastomer film, we show that wettability patterns on both flat and curved surfaces can be generated spontaneously via a simple dip coating process. Variations in dipping time, sample prestress, and chemical treatment enable independent control of domain size (from about 100 to 500 μm), morphology, and wettability contrast, respectively. We characterize the wettability contrast using local surface energy measurements via the sessile droplet technique and tensiometry.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.
authors.forename: Dayong
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 gareth@mit.edu recohen@mit.edu.
authors.forename: Gareth H
authors.initials: GH
authors.lastname: McKinley
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; gareth@mit.edu recohen@mit.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Cohen
keywords: creasing instability; curved surfaces; domain size; morphology; wettability contrast