Dr. Anish Tuteja has developed a coating that will repel just about any liquid.
You may have heard of oleophobic coatings (which reduce smudges on your touchscreen) or hydrophobic coatings (which repel water). Working with a team at the University of Michigan, he’s developed a new coating for material that will repel both Newtonian and non-Newtonian fluids of just about any kind. They’re calling it superomniphobic.
According to Dr. Tuteja, the key to making fluids bounce off a material is to trap pockets of air between the fluid at the surface. This starts as a chemistry problem (you want a material with low surface energy) but quickly becomes a physics problem. “With chemistry we can cause water to bead up but not oil,” he says. “To get to the next step you have to design the geometry or the shape of the coating.”
To create the coating, the team takes a polymer solution and applies an electric field to it. By tuning the concentration of the polymer solution, they can change how the solution breaks up into microscopic droplets. These droplets are then deposited on the surface, and Dr. Tuteja says they can coat any material.
The result is a hierarchical texture, where a highly porous surface is itself made up of nanopores. There are so many millions of tiny pockets of air trapped under the droplet that the fluid and the surface barely come into contact at all. Dr. Tuteja says they’ve left samples submerged for up to two months. They come out completely dry.
OK, so is this stuff magical? Not so, says Dr. Tuteja, for while it’s basically invulnerable to fluids (including monsters like hydrochloric acid) thanks to its properties at the nano scale, it’s very vulnerable at the mechanical scale. “Durability remains a big issue. It’s easy to peel this one off,” he says.
The good news is they are working on a more durable coating. It’s made using similar principles but the polymers and the manufacturing process are different. Applications for such a material run from protecting gadgets in the field to making coatings for boats that reduce drag as they slice through the water.
It’s all part of a series of investigations that Dr. Tuteja says the team has been running for five years since he was a post doc at MIT. As they progress, some materials can be commercialized quickly, while others help them learn new principles for application to the next project. “All the work we do in my lab is to a particular application,” he says. “We try to think of novel ways to solve a particular problem. We try to figure out if there is a better way to address that and find the scientific principles along the way.”
“It’s a very visual field, you immediately know whether you have succeeded or failed.”Go Back to Top. Skip To: Start of Article.