Sticky Business
Open gallery
Biologist Kellar Autumn is one of the world’s leading authorities on gecko adhesion.
The spiders were driving him crazy.
When Kellar Autumn was a postdoctoral fellow in Berkeley, California, he and his wife took a vacation to Hawaii. The rundown hippie hotel where they were staying was loaded with spiders, but fortunately for the world of biological innovation, it was also home to a small gecko.
Autumn flopped down on the bed and looked up. A giant spider danced on the ceiling right above him. He stared at the eight-legged creature. Should he grab a glass from the bathroom and try to catch it, or maybe use his shoe to smash it?
Suddenly, out of the corner of his eye, he spotted a tiny lizard, a tropical gecko. It effortlessly darted across the ceiling and attacked the spider. In a fierce upside-down battle, the sure-footed gecko easily overcame and then ate the spider. Belly full, the six-inch lizard scurried across the ceiling and down the wall.
It was all over within a few seconds, but it was a moment of inspiration for the science detective. “How can a gecko climb on the ceiling?” Autumn asks, his face animated with the scientific quest that still drives him. “Could we make a robot that could do the same thing? I’ve been trying to answer these kinds of questions for the past 10 years.”
When Autumn returned from Hawaii, he discovered that scientists had been asking similar questions about the nimble gecko for many hundreds of years. Among others, Aristotle marveled at the reptile’s ability to walk up any surface, hang upside down, and effortlessly stick to even the smoothest surfaces. There have been many attempts to solve the riddle, but no one has come closer than Autumn to figuring it out.
“Early microscopy studies showed that geckos have millions of microscopic hairs on their feet,” he explains. “The tips of those hairs aren’t easily visible even with the best light microscopes, so it’s not surprising that researchers proposed a number of theories like suction cups and glue to explain the gecko’s ability.”
The introduction of the electron microscope in the 1950s showed that the ends of gecko feet hair split into hundreds of tiny spatula-shaped nanotips. Autumn devised an experiment to measure the forces generated by the tips and found that molecules in these pads are faintly attracted to surfaces, thanks to something scientists call van der Waals’ forces. It’s the same attraction that bonds oil molecules together and keeps them from dispersing into gas. When multiplied across the surface area of the gecko hairs, these weak bonds form a strong adhesive.
Autumn’s discovery opened the door to an entirely new subfield of science: adhesive nanostructures. “We’d found the first mechanically controllable adhesive,” he says. “We learned that geckos can stick under any conditions to virtually any surface because of van der Waals’ forces. The mechanics of the hair allow it not only to stick, but to be released easily.”
David Wake, a professor at the Graduate School in Integrative Biology, University of California at Berkeley, and one of Autumn’s early mentors, says, “Autumn’s work is inspiring. I had no idea that van der Waals’ forces could play any significant role in the biomechanics of macroorganisms such as geckos.”
Wake calls his former student “highly logical and organized in approach … gifted and filled with insight. I admire his good sense and judgment and his intellectual prowess.”
Last year, in an article in the Journal of the Royal Society Interface, Autumn’s research team wrote, “Conventional pressure-sensitive adhesives are either strong and difficult to remove (e.g., duct tape) or easy to remove (e.g., sticky notes).” Autumn says that gecko technology could offer the best of both.
Of course, Autumn’s discovery raised even more questions, which continue to propel his research program. He wanted to understand the mechanics of the gecko hairs. He and his student researchers devised a complex experiment on a Lilliputian scale. They isolated a single microscopic gecko-foot hair–one-tenth the width of a human hair. Then they built a very precise manipulator and a new device that could measure the tiny adhesion forces exerted by the hair.
The experiment was difficult to set up, so they were pleased when it was completed. But soon they became increasingly puzzled and frustrated when their force device consistently registered zero. They couldn’t get the gecko hair to stick. The hair exerted no force at all. For two months, they struggled without results. Then it came to Autumn in a moment of insight. “We weren’t thinking or moving like a gecko,” he says. “When a gecko plants a foot on the wall, it presses the foot lightly into the surface, then drags it inward. I knew this from a study I’d done on the mechanics of gecko motion. When we applied gecko motion in the manipulator, we found it turned on the adhesion in the hair.”
The results were stunning. They revealed that gecko hair is amazingly sticky–at least 10 times stronger than Autumn had imagined. He knew he was onto something big. “We found that a gecko’s worth of these hairs–about 6.5 million of them, which could fit on a dime–could lift 130 kilograms, or the weight of a big football player. This adhesive isn’t just strong enough to hold a gecko, but strong enough to hold a person or something even larger.”
Not only is gecko adhesion incredibly strong, it’s also self-cleaning. Despite the fact that geckos walk around in dirty, dusty places, their sticky feet stay clean. In a study with Wendy Hansen BA ’01, a Rena Ratte Award winner at Lewis & Clark, Autumn found that gecko feet are self-cleaning due to their nanogeometry. Once the researchers discovered the mechanism for clean gecko feet, they were able to model and test it.
It was a significant leap forward. Autumn had unraveled the mystery behind the first mechanically controllable, self-cleaning adhesive known to science. The applications for this gecko glue are unlimited. It could take the place of zippers, screws, or stitches. It has the potential to be used anywhere dry, clean, removable adhesive is needed. “Imagine thousands and thousands of applications for these adhesive nanostructures, ranging from medical applications like nanosurgery to sports applications like gecko gloves and climbing boots,” he says. “We could brainstorm 10 new applications right now.”
Autumn and his colleagues have applied for six patent applications for adhesive nanostructures and developed a number of potential applications. Four of the patents have been granted. Major biomedical companies like Johnson & Johnson are interested. His gecko adhesive discoveries have the potential to make Autumn a wealthy man, but he brushes aside the possibility. “Getting wealthy isn’t why I got into science, and I’d be surprised if it happened,” he says.
He’s more intrigued with the adhesive’s potential to change the world. “You could reduce reliance on adhesives made from toxic compounds and replace them with inert, hard-adhesive nanostructures that can rebond easily. Things would be more durable and you’d be able to disassemble things for recycling. This idea could make the world a better place.”
It’s clear that ideas, puzzles, and questions rather than cash motivate Autumn. As a young postdoctoral graduate in integrative biology from UC Berkeley, he could easily have gone into business or industry. But the challenge of research and teaching in higher education was more appealing. “I’m motivated by the pursuit of knowledge,” he says. “Interacting with bright, creative people here at Lewis & Clark makes me happy.”
When Lewis & Clark offered him a job 10 years ago, it was the synergy between research and teaching, which allows him to be both scientific explorer and mentor to his students, that sealed the deal. Thea Lambert CAS ’09, a biology major, says Autumn demands students think for themselves and become problem solvers. “He gives us a great deal of freedom and demands self-sufficiency. He’s always available for advice and suggestions, but he expects us to run our lab projects independently, which gives us a real taste of science. It forces us to face our own mistakes and figure out ways to fix them.”
Autumn’s work at Lewis & Clark has not only enabled him to make major discoveries, it’s also changed his view of the world. “My work has taught me that the world is very complicated and often counterintuitive. Simple answers are usually wrong. That makes it interesting to me. It’s also convinced me that academia is a very valuable enterprise. The world faces so many political and social challenges, and academia has the potential to solve a lot of these problems.”
He says that the world’s complexity and its interconnectedness create an increasingly difficult task in preparing students for life beyond college. He tells students who want to be scientists to study more math and science; he tells students who don’t want to be scientists to do the same thing. “The leaders, the visionaries, the inventors of the future can’t afford to ignore science. The world is highly interdisciplinary, technical, and scientific. Science classes teach critical thinking skills and approaches to the world that will last a lifetime.”
It’s a message recent graduate Hannah Hultine BA ’08 received loud and clear. “Kellar’s style of teaching has changed the way I think,” says Hultine, a biology major who has been inspired by Autumn to apply to graduate school. “His classes have taught me to think without making assumptions and to ask the right questions.”
A small photo of the Dalai Lama is clipped to Autumn’s in-box. Early in his career, he worked 80+ hours a week. He still works hard. However, his research has taught him that working longer doesn’t necessarily mean getting more done. Instead, he’s learned to appreciate balance in his life and, like the gecko, he’s become more efficient and effective. In addition to teaching and science research, he makes time to be with his wife of 23 years and his two daughters. He also enjoys taking Zenji, his Egyptian Basenji, to the dog park and careening down narrow, steep paths on his mountain bike.
Kellar Autumn is clearly a man having fun. And it’s something he wants to share with his students. “Lewis & Clark is a unique place because students can get a rigorous, deep, and broad education–and they can have fun while doing it. That was one of the things that brought me here. There were equally talented students and faculty at other places, but they didn’t seem to be having as good a time. That’s important. It’s easy to work hard when others are working hard and having fun.”
Bobbie Hasselbring is an award-winning freelance writer and author who has written for a number of colleges and universities.
