Participant: Dayong Chen
Collaboration with Gareth McKinley, MIT MechE
In the second subproject we have been investigating novel approaches to produce patterns of hydrophobic and hydrophilic character on polymer-coated surfaces. 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 pre-stress and chemical treatment enable independent control of domain size (from about 100 μm 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.