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Judy Woodruff: Finally tonight- Have you ever had trouble getting ketchup out of a bottle? How about stopping an oil rig from exploding? A lab in Boston has developed a slick solution for both problems. Our science producer, Nsikan Akpan, reports about this new coating in our latest episode of ScienceScope.
Nsikan Akpan: Look at this ketchup sliding, so smooth, so easy. Back in the day, using condiments tended to end with a caveman-mess, but not with these high-tech bottles. Their insides are coated with something called LiquiGlide.
Kripa Varanasi: It's a coating technology that can basically get every last bit of the product out, so you can save on billions of tons of product that's wasted. What LiquiGlide does is fundamentally changes how liquids and solids interact.
Nsikan Akpan: That's Kripa Varanasi, a mechanical engineer at the Massachusetts Institute of Technology who co-created LiquiGlide to battle the nefarious issue of interfaces. An interface is any spot or surface where two things meet. You're familiar with the physical forces creating friction and solid interfaces, like when a tire skids on a road. But a liquid sliding across a solid also experiences this friction in tension. It's part of what makes some liquid sticky, such as maple syrup.
Kripa Varanasi: It's a ubiquitous problem, whether it be in consumer products, or personal care products to chemical industry to energy industry.
Nsikan Akpan: LiquiGlide came about due to an infamous interface problem in the oil industry. Drilling oil unearths all types of crud, mucky sediment and minerals. This includes methane hydrate crystals, which can form molasses-like goop and plug a pipe.
Kripa Varanasi: If they form, it can be very catastrophic, because if you release sort of this methane hydrate plug, the methane can come out and essentially lead to an explosion.
Nsikan Akpan: Kripa was mulling how to prevent these plugs from forming when a similar problem sprouted at home.
Kripa Varanasi: And at that time, my son was about a year old. My wife was trying to get honey out of a bottle. And, you know, she said, you know, why don't you apply this technology to bottles?
Nsikan Akpan: Kripa knew a plastic surface, a glass surface, any solid surface, for that matter, isn't truly smooth. It's covered with microscopic ridges and gaps. These pockets trap liquid and cause friction at interfaces. So, Kripa and his former grad student Dave Smith chemically designed a liquid to intentionally experience so much friction, it gets stuck in these pockets. This embedded liquid acts like a lubricant. Put ketchup in the bottle and it glides against the lubricant nano-layer, never coming in physical contact with the glass. Get it? LiquiGlide.
Dave Smith: Then we thought about, how can we make this easily and sprayable?
Nsikan Akpan: Smith developed a formula that can predict and build coatings for any solid surface. Once sprayed, LiquiGlide adheres so firmly to the bottle that it can't seep into the container's contents. But, as a precaution, the coatings they use for food applications are edible and FDA-approved. They founded a start-up in 2012 and their sprayable coatings now help squeeze out the stickiest stuff, toothpaste, cream cheese, paint. Even Elmer's Glue uses LiquiGlide. LiquiGlide won't work for every pocketbook. Uniformly applying a coating becomes tricky for larger containers. And specialized coatings are more expensive than materials like plain old glass. So, right now, LiquiGlide is best suited for smaller containers or situations where you can easy respray it, like with industrial bins. Back at Kripa's lab, a new legion of grad students is conquering other interfaces. Say you're tired of flight delays due to ice-covered planes.
Henri-Louis Girard: If you have icing rain, for instance, on a wing, the time that it's going to spend on the surface will determine whether it ices or it doesn't. So we want to minimize the time that it spends on the surface. And the way we do that is that we create microscopic ridges on the surface. And if we impact a drop now on the middle of the ridge, we can see that it breaks up in two parts that will bounce off independently. And because these two parts are smaller than the initial drop, they bounce off faster. And this is because when the drop bounces, it actually acts like a spring that gets compressed when it expands and then retracts. And smaller drops act like smaller springs that are actually stiffer than the larger drop. And stiffer springs will bounce off faster.
Nsikan Akpan: If smaller drops bounce off faster, then water is less likely to stick, so covering a plane in these microscopic ridges could eliminate the toxic chemicals airlines currently use. Other students in Kripa's lab are learning how to stop clogs at desalination water facilities by observing how saltwater evaporates, or they're keeping water from condensing on steam turbines to improve energy efficiency at power plants, or they have brewed a pesticide spray that sticks to plant leafs more effectively, rather than washing away into the environment. That's all from now. I'm Nsikan Akpan, and this is ScienceScope from the PBS NewsHour.
