CAMBRIDGE, MASS. — If a glue could not stick to the inside of the tube or bottle, you might think, This does not seem like a very good glue.
On the other hand, clinging glue has annoyed generations of parents and children attempting to scoop out the remaining bits with their fingers.
LiquiGlide, a company started by a professor at the Massachusetts Institute of Technology and one of his graduate students, has come up with a solution for this particular one of life’s little problems: a coating that makes the inside of the bottle permanently wet and slippery. The glue quickly slides to the nozzle or back down to the bottom.
The company announced on Monday that Elmer’s Products Inc. had signed an exclusive licensing agreement for the use of such coatings in glue containers. “We certainly see a chance for a competitive advantage,” said Anthony Spath, associate manager for innovation and business development at Elmer’s.
LiquiGlide, in Cambridge, Mass., has also licensed its technology to a packaging company in Australia. The idea there is to make the inside surface of paint can lids slippery so paint would slide back into the can instead of sticking to the lid and drying there. The dried bits fall into the paint and not only end up as bumps on a painted wall, but can also clog painting equipment.
The technology could also have major environmental payoffs by reducing waste. In a few years, “we expect it to be ubiquitous,” said J. David Smith, the graduate student turned chief executive of LiquiGlide.
Tests by Consumer Reports in 2009 found that much of what we buy never makes it out of the container and is instead thrown away — up to a quarter of skin lotion, 16 percent of laundry detergent and 15 percent of condiments like mustard and ketchup.
“It’s pretty crazy, getting mayonnaise out,” said Kripa K. Varanasi, a professor of mechanical engineering at M.I.T., who is Mr. Smith’s thesis adviser and co-founder of LiquiGlide.
Take a look at mayonnaise sliding easily out of a LiquiGlide-coated squeeze bottle.
What makes it hard to get mayonnaise and toothpaste out is that they are what scientists call Bingham plastics. A Bingham plastic, named after Eugene Bingham, a chemist who described the mathematical properties, is not made of plastic; the term describes a highly viscous material that does not flow without a strong push.
Dr. Varanasi did not set out to solve the problem of clingy glue and mayonnaise. Rather, he was thinking of larger-scale industrial challenges, like preventing ice formation on airplane wings and allowing more efficient pumping of crude oil and other viscous liquids. How to make a slippery surface has been an interest for many scientists and engineers with many potential uses.
When water or other liquids flow through a pipe, the layer of liquid next to the pipe wall typically sticks, not moving. Farther from the pipe wall, the liquid flows, fastest at the center. “Different layers of water are sliding past one another, and therefore there is friction, which is viscosity, and that is why you need to pump it,” said Neelesh A. Patankar, a professor of mechanical engineering at Northwestern University, who is not involved with LiquiGlide.
The trick is to find a way around the so-called no-slip boundary condition. “What people have tried to do is, can we have something between the solid surface and the liquid which will help the liquid slide?” Dr. Patankar said.
One simple example is when a droplet of water skitters across a hot pan that vaporizes some of the water. The droplet is riding on a layer of steam like a hovercraft, not touching the pan.
Dr. Patankar and other scientists have been investigating superhydrophobic surfaces. A hydrophobic surface repels water; a superhydrophobic surface, as one might imagine, really repels water. Inspired in part by lotus leaves, the surface of a superhydrophobic material looks rough, at least under a microscope. Water rolls up into balls, sitting on the tips of the rough surface, but mostly on air trapped between the droplet and the rough surface. The droplets roll off easily.
That technology has had some success. Rust-Oleum, for example sells a superhydrophobic treatment developed by a company called NeverWet in Lancaster, Pa. But the microscopic roughness can be damaged, and then water flows in, displacing the pockets of air, and sticks to the no-longer-slippery surface.
Because air dissolves into water, superhydrophobic surfaces can also lose slipperiness when submerged for long periods. That makes it impractical for ship hulls, for instance. But Dr. Patankar and his colleagues have shown that with a clever choice of texture, trapped water vapor could serve as the persistent layer separating the water from the surface.
LiquiGlide’s approach is similar, but it uses a liquid lubricant, not a gas.
”What could be a solution that provides sort of universal slipperiness?” Dr. Varanasi said. “The idea we had was, Why not think about trapping a liquid in these features?”
Dr. Varanasi and Mr. Smith worked out a theory to predict interactions among the surface, the lubricant and air. Essentially, the lubricant binds more strongly to the textured surface than to the liquid, and that allows the liquid to slide on a layer of lubricant instead of being pinned against the surface, and the textured surface keeps the lubricant from slipping out.
“We’re not defying physics, but effectively, we are,” Mr. Smith said.
The approach also allows them to vary the ingredients of the textured layer and the lubricant to fit the properties of different liquids — for food applications, the coatings are derived from edible materials. (The company does not divulge the specific ingredients. “We use things that are, maybe, parts of foods, you’d say,” Mr. Smith said. “You wouldn’t make a meal out of our coatings.”)
The shift from industrial applications to packaging started when Dr. Varanasi’s wife was having trouble getting honey out of a bottle and asked him, because he was an expert on slipperiness, whether he couldn’t do something about that.
Meanwhile, M.I.T. was sponsoring a $100,000 contest for entrepreneurial ideas. Mr. Smith and Dr. Varanasi decided to enter. Over a weekend, Mr. Smith developed a prototype of a ketchup bottle. Using a video of ketchup sliding out, they were the runner-up and won the Audience Choice Award. Then they started LiquiGlide. (Mr. Smith has not finished his doctorate but said he planned to.)
A mayonnaise bottle could be coming this year or early next year, the founders say. Easier-to-squeeze toothpaste could arrive in 2017.
So far, makers of ketchup, which is less viscous, have not shown much interest. LiquiGlide, with 20 employees, just moved to a larger office and laboratory space, and this month announced a $7 million investment from a venture capital firm.
The company is also exploring the industrial applications originally envisioned, including coatings for petroleum storage tanks and pipelines. That could not only reduce the energy needed to push materials through the pipes, but also speed cleaning of tanks, with fewer chemicals.
Crude oil, for example, slips off a LiquiGlide-treated sheet.
“There are significant savings from a sustainability perspective,” Dr. Varanasi said.
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