Jaren Wilkey, BYU
An observer to a lab in one of the basement rooms on the Brigham Young University campus might wonder why mechanical engineering students and faculty are shooting water with different intensities and quantities at various surfaces in the room.
But it is from those tests that researchers are developing super-hydrophobic — extremely waterproof — surfaces that have the potential to help many industries throughout the world.
“[The lab is] fun, but definitely a work space,” said Julie Crockett, who is an associate professor in BYU’s mechanical engineering program.
Professor Crockett and her colleague, Dan Maynes, who is also a professor and the Mechanical Engineering Department chairman, have spent the past few years studying water and how it attaches — or doesn’t attach — to surfaces.
Through their research, they have figured out how to make surfaces more waterproof by analyzing water as it hits different surfaces. Recently, they have figured out how to make water hit the surface, ball up and then bounce off.
“We have been researching these super-hydrophobic surfaces, or these structured surfaces with a coating, to really understand how they do a couple really big things,” said Professor Crockett. “They repel water and create droplets, making them really waterproof, which is really great for self cleaning-type mechanisms.”
As neat as it is to see, these findings have a greater impact when looking at possible practical applications in the future. A more waterproof surface could benefit many industries, the researchers say.
“One [example] would be surfaces that never get dirty, or a surface that would clean itself,” said Professor Maynes. “If you’ve got a building that has a lot of windows, and you don’t ever want to have to wash those windows, you have windows that are super hydrophobic. Then, anytime water hits it, it will bead up and roll off of it. If there is any dust or particulate that gets on it, it will automatically be cleaned by that action. In a normal window, when water hits, it spreads out and then leaves a deposit behind of the dirt that is on it.”
So windows — whether it is a windshield of a car or building windows or any other glass — would be self-cleaning and always remain pristine, he said. That could be expanded to showers and other surfaces in a home.
“In general, any surface you don’t want to get dirty — whether it is boots or tools or machinery or equipment or cement or something else — they won’t get dirty at all, and you won’t have to continually wash them,” said Professor Maynes.
Another possible application could be in solar-powered plants where solar panels can be more effective during rain and dust storms. The researchers say the extreme waterproofing ability could also come in handy for medical devices, making the interior of tubes or syringes that transport fluids to patients more effective.
Although the research on waterproofing isn’t new, it is the particular structure of the surfaces microscopically that is making a difference.
“We analyze not just how — I mean, the droplets are cool, and they bounce and move around — but we also study the jet of liquid hitting these surfaces and how that spreads out and moves,” said Professor Crockett. “And also by studying an entire liquid flow over the surface that we put these channels and to actually have fluid over them, we can see what kind of resistance we can have.”
Researchers have created these super-hydrophobic surfaces by etching patterns — one that has micro posts or the other that has ribs and cavities (the size of a human hair) onto the surface. They then add a water-resistant film — such as Teflon — to the surface, and that combination creates a super-waterproof surface. As they alter the width and angles of the ribs and cavities, they are able to find different results.
“These particular surfaces can do this because of the structure of the surface,” said Professor Crockett. “You get air pockets in between where the fluid is actually touching, reducing the drag, so there is not as much friction because there is not as much contact between a liquid and a solid.”
This also has the possibility of helping in the ship industry, researchers say. When looking at a ship in the ocean, there is friction between the water and the surface of the ship. If the ship were to have a super-waterproof surface, there would be much less drag or resistance to motion, making travel faster and more economical.
“When you are talking about ships, you are talking about such an enormous amount of energy that is consumed each year all around the world,” said Professor Maynes. “So the reduction of only one or two percent of the overall drag represents literally billions of dollars. Even though the amount of reduction may not be big, the cumulative reductions are.”
Although the list of practical applications is interesting and fun to think about, the main reason for their research goes beyond waterproofing, said Professor Crockett. With an array of experiments always in progress, BYU professors and students are working hard on their research to find the type of surface that is best for a specific application.
“We really want to understand the physics,” she said. “We foresee many applications, and part of the vision that we have is to understand how to create these surfaces and understand them enough so that other people understand them as well.”
From there, Professor Crockett is excited to see what benefits and possibilities — of which researchers haven’t yet considered — come up because of their research.
The research — focusing on surfaces with microscopic patterns coupled with the waterproof coating — was recently published in the academic journal Physics of Fluids.