It started with a bottle of honey.
Kripa Varanasi and his wife, Manasa, were at home, and she was trying to make a snack for their young son. She was struggling to spoon out some honey, frustrated by how hard it was to get the last bits of sticky sweetness from the bottom of the container. Finally, she turned to her husband. “You work on slippery things,” she said. “Why can’t you make a slippery bottle?”
Varanasi, an associate professor of mechanical engineering, says he knew instantly that was just the idea he had been looking for: “I was like, that’s brilliant!”
The two of them had been discussing the details of a new company that he and one of his students, David Smith, had just launched to commercialize an invention they’d developed as part of Smith’s doctoral thesis work. After finding a way to make very slippery surfaces, they had been seeking a real-world application. But the ideas they’d come up with just weren’t cutting it—until Manasa hit on the honey jar.
Five years later, that company, called LiquiGlide, has just closed its second round of venture capital—for a total of more than $24 million in funding. And already LiquiGlide has contracts with more than 70 companies to bring various versions of its slippery coatings, some of them food-grade, into the marketplace by way of ketchup and glue bottles, cosmetics jars, paint cans, mixing vats for agrochemicals, and more.
It’s been quite a run lately for Varanasi. He’s also founded a second company, whose work with large industrial partners is poised to make a dent in the world’s carbon emissions. A video depicting the invention behind LiquiGlide—showing ketchup sliding effortlessly out of its bottle—has been watched well over two-thirds of a million times on YouTube. In the span of a recent week, he was featured on BBC, CNN, NBC, and other outlets nationally and internationally. And he and his wife had their second child in November, just a year after he earned tenure as an MIT professor.
But the concept behind that initial slippery invention, which led up to that “Aha!” moment, had been years in the making.
Since he was a kid growing up in Hyderabad, in southern India, Varanasi has been passionate about tinkering, inventing, and figuring out how things work. As the child of a physics teacher mother and an electrical engineer father, and the grandson of two teachers, he had no shortage of mentors and tutors as he built electronics circuits from kits, devoured math books, and created projects for science competitions. He earned a coveted spot at one of the country’s elite engineering schools, IIT Madras, and from there he went to MIT, earning his PhD in mechanical engineering in 2004. After a nearly five-year stint at GE, he returned to MIT in 2009 to join the faculty in mechanical engineering. And that’s where the insights into slippery surfaces really began.
“I wanted to have a lab that will improve efficiency in a whole range of industries,” says Varanasi. And he had a hunch that focusing on interfaces would prove useful. As he worked on real-world problems in a variety of industries, he indeed began to notice a common thread: inefficiencies often arose from the way materials behave at interfaces, the places where a solid surface makes contact with liquids, gases, or other solids. For example, on airplane wings, water vapor turns to ice, adding weight and reducing lift. On the condensers in a power plant, hot steam meets cool surfaces to convert, not very efficiently, into liquid that can then go back to a boiler to be revaporized. In pipelines, the flow of oil and gas can be slowed or even blocked by frozen methane hydrates that stick to the pipes’ walls.
Varanasi found that small changes at those interfaces could have big results. To prevent clogged pipelines and icy airplane wings, he needed a way to prevent water or other fluids from sticking to surfaces. So he and his students started by examining exactly what was going on in these situations at the atomic and molecular level. They did modeling based on fundamental laws of physics and then studied the wetting process in microscopic detail in the lab.
Keeping water from sticking to surfaces involves a property called hydrophobicity (literally, a fear of water) or, in its more extreme form, superhydrophobicity. Many labs around the world work on developing superhydrophobic surfaces, but Varanasi and his team have pushed this property in new directions. They’ve made surfaces that shed many kinds of fluids and others that remain highly durable, even in harsh environments like power plants full of hot steam.
The insights that launched LiquiGlide came gradually. Varanasi set out to find a way to create a perpetually slippery surface that could be used with a variety of fluids. He likens the problem to cooking a pancake on a griddle: to keep it from sticking, you coat the pan with a layer of oil, but the oil needs to be replenished as you add more batter. What if there were a way to make the oil stay in the pan?
That’s where the basic physics came in. Varanasi and Smith realized that by creating a surface with a sufficiently fine microscale or nanoscale texture, they could harness capillary forces—the same thing that lets water rise up inside a tree’s tiny internal passageways—to hold a lubricant securely in place. And sure enough, after a lot of experiments with different kinds of textures and lubricants, they found combinations that achieved just that: they could pattern the surface by scoring or etching (or, later, by spraying a special coating), and then a layer of oil or other lubricant applied to that surface would be anchored solidly in place in its tiny crevices. It worked, and the coatings proved to be amazingly durable.
When they patented the process, one initial focus was going to be on coatings for the condensers in steam-based power plants. They figured out that by getting those condensers to shed water droplets more quickly as they formed, they could improve the overall efficiency of the plant. Even a small improvement could cut global carbon emissions significantly.
But it turned out to be an uphill battle to find customers willing to pay for a large-scale installation that hadn’t been proved operationally. So they started thinking about consumer products. What could they make with this process that wasn’t capital intensive and could be sold directly?
That’s when Manasa’s suggestion came along. The samples they had been testing in the lab were flat surfaces, and they hadn’t really thought much about coating complex curved surfaces, but with a bit more work they found that their process could indeed work well for containers. Smith prepared a set of demonstrations, using nontoxic coated containers for mayonnaise, honey, ketchup, and toothpaste. He made short videos demonstrating the results, and one of those quickly went viral.
The ketchup bottle—a vessel that famously retains its contents despite pounding, shaking, and coaxing—was what really caught people’s attention. And with that consumer-oriented approach, the company branched out.
Now, LiquiGlide tests and tweaks customized versions of its coatings to work with a wide variety of thick, viscous liquids. This could be helpful, for example, to paint manufacturers, who lose up to 30 percent of their production runs when paint sticks to mixing tanks and has to be washed away with a large volume of water that becomes contaminated in the process.
“In the paint industry alone, they lose about an estimated 200 million tons of product and produce millions of gallons of wastewater, so all of that adds up to lots of dollars wasted,” Varanasi says.
And that’s just one of his invention-based startups. Three years ago, he and MIT associate provost Karen Gleason formed another company, called DropWise, that is harnessing a highly durable superhydrophobic surface aimed at condensers in steam power plants and rough environments like oil and gas drilling operations. Yet another company is in its earliest stages, just a few months old and still in stealth mode. “I really think of science as a way to enable design. And I think that’s what made this happen,” Varanasi says. But it might not have come to pass if it hadn’t been for that one annoying honey jar.