Contact Line Dynamics on Surfaces with Non-uniform Wetting Properties

 Film flow over a surface with alternating hydrophilic (dark gray) and hydrophobic (frosted white) bands.

Film flow over a surface with alternating hydrophilic (dark gray) and hydrophobic (frosted white) bands.

We encounter surfaces of wildly different wetting properties every day: from waterproof table cloths that cause water to break into droplets to the paper towel that soaks all that water up. The surfaces that repel water, like the waterproof table cloth, are said to be "hydrophobic" whereas surfaces that attract water are "hydrophilic".

 Wave trains generated by alternating hydrophilic and hydrophobic stripes on the bow of a ship model. 

Wave trains generated by alternating hydrophilic and hydrophobic stripes on the bow of a ship model. 

Our current work focuses on surfaces with alternating hydrophobic and hydrophilic regions. These patterned surfaces mimic the surfaces of ships, which are regularly painted but experience fouling over time due to environmental conditions. Fouling may lead to local changes in the ship’s wetting properties. We study how these non-uniform wetting properties affect the contact line, which is the intersection between air, water, and a solid surface. Studying ways to control and modify the contact line may lead to the development of methods to reduce drag and control the spray signature of ships .

We began by investigating the more fundamental question: how do thin water films and rivulets behave on patterned surfaces? We found that film flows were dominated by roller structures while rivulets were often seen jumping over the repulsive, hydrophobic regions. 

We are now starting experiments in naval-like contexts and are excited to see how the observations made thus far translate to these flows.