• Secret behind geckos' fancy footwork may yield amazing inventions
Kellar Autumn was on vacation in Hawaii, lying on his back in a hotel room, when he saw a monstrous spider on the ceiling directly over his face.
While he was trying to determine what to do next, a gecko glided across and took care of the problem for him. The lizard easily outmaneuvered the hapless spider, picking it up and throwing it down from the ceiling to the floor.
The upside-down battle would have grabbed anyone's attention, but for Autumn it was a moment of insight. He'd spent much of his adult life studying geckos. 'It hadn't even occurred to me that the most interesting thing about geckos is that they have sticky feet,' he says.
Seven years later, Autumn, a 40-year-old associate professor of biology at Lewis & Clark College, is arguably the world's expert on gecko feet. He's learned that gecko feet aren't just incredibly weird. They also could prove extremely valuable, because their feet function as self-cleaning adhesives that one day may be replicated synthetically, leading to all sorts of potential inventions.
Imagine reusable duct tape, without the messy goo. Or a rock-climbing anchor that could stick to a solid granite face without budging.
Or climbing robots to help with search and rescue missions.
Or a nontoxic medical adhesive for internal use.
Or an improved version of the Mars rover, with gecko toes instead of wheels.
'If you had asked me 10 years ago if my gecko research would have been useful, I would have said, 'I doubt it. I'm just curious,' ' Autumn says. 'But now, in this serendipitous sequence of events that's been totally unpredictable, it's turning out to be really, really useful.'
When Autumn returned to Portland from that vacation in 1998, he went straight to the library, assuming that somebody must have figured out how gecko feet work. It turned out no one had, though many had tried.
So how do gecko feet work? Do they contain tiny suction cups? Or tiny spikes like the crampons on climbing boots? Do they secrete some chemical that makes them sticky? Do they use static electricity?
None of the above. But clearly the key to the puzzle lay somewhere in the tiny hairs on a gecko's toes. So in 2000 Autumn collaborated with scientists and engineers at the University of California, Berkeley (where he had earned his doctorate in integrative biology in 1995) to isolate a single hair on a gecko's foot, an object one-tenth the diameter of a human hair, with hundreds of branches or split ends so small they can only be seen through an electron microscope.
They had what they needed, but they couldn't figure out how it worked. Months went by, and everybody wanted to quit, Autumn recalls. And then came the breakthrough realization: Gecko feet don't stick by chemical attraction but by very weak molecular attractions called van der Waals forces.
In other words, gecko feet are sticky by design. Ron Fearing, an engineer at UC-Berkeley, was able to nanofabricate synthetic gecko hair from two different materials.
Not only did this revelation free Autumn and his colleagues from having to spend years studying complex genetic sequences and chemical formulas, it also opened the door to a huge array of potential practical uses.
'What it meant was that to make a synthetic gecko, you don't have to copy the gecko's chemistry,' Autumn says. 'You don't have to sequence gecko genes. Instead you use geometric structural principles to take something that used to be slippery and make it sticky.'
Autumn and his colleagues immediately began filing patents, and all sorts of people started showing interest. Today their sponsors include the National Science Foundation, the U.S. military's Biologically Inspired Multifunctional Dynamic Robotics Program, the M.J. Murdock Charitable Trust, the John S. Rogers Science Research Program and multiple corporate sponsors who are withholding their names.
Invention ideas abound
As he shows visitors around his office and lab, nonchalantly holding a gecko in his right hand, Autumn makes it clear that while he respects the lizards, he does not particularly like them.
Geckos have attacked several of his students. And then there was the television crew from the BBC that learned the hard way that geckos have limits in the amount of intrusion they will accept.
'They attacked the entire BBC crew, just terrified the interviewer and landed on the sound guy,' Autumn says. 'The sound guy was from Wales, and he taught us some new words that day.'
Autumn's lab is as quirky in appearance as its subject matter. A sign warns, 'Do not stare at laser with remaining eye.' Inventions abound, including a gecko-inspired 'toe-bot' and a device that uses a laser to measure the contact areas of adhesives.
Autumn's past field research has led him to Turkmenistan, western China and Tibet. But while the Solomon Islands and New Caledonia are tempting locations for future gecko sabbaticals, for now Autumn is well-settled in Portland, which he calls 'one of the great cities in the world.' He lives with his wife, Valeurie Friedman, and their daughters, Kendra, 8, and Kaisa, 4, in the Hillsdale neighborhood, where they recently had a climbing wall installed in their home.
He has no plans to leave academia, Autumn says. He decided long ago that he would not form a startup company, and he says he's happy to work at Lewis & Clark, where he gets to work with 'lots of really brilliant undergrads.'
'Sweet spot' may pay off
Autumn's most recent paper, co-written with one of his former students, Wendy Hansen, was published this month in the Proceedings of the National Academy of Sciences. The paper explains how gecko feet function as a self-cleaning adhesive.
'There are lots of sticky things, but all of them get all gunked up,' Autumn says. 'Take a piece of tape and stick it in the dirt, and it's worthless. But geckos put their feet in the dirt all day long, and their feet stay sticky.'
So how do they do this?
'What we found was quite bizarre,' he says. 'The hairs, taken apart from the gecko, were self-cleaning. You don't need to have a gecko attached to the hair in order for them to clean themselves.
'The answer, once again, appears to be in an extremely clever structure that interacts with surfaces in a particular way, so as to minimize the attraction between dirt particles but still maintain enough attraction to the surface to make them really sticky. It's the sweet spot in the design space that allows the adhesive to be self-cleaning.'
Replicating that 'sweet spot in the design' is the challenge that Autumn's engineering colleagues now face. If they can manage to do so, the potential uses seem endless. For example, an effective adhesive that sticks because of its design rather than its chemistry could theoretically be made out of a material that could enter the human body without damaging it, allowing for all sorts of surgical uses. Nothing like it currently exists in medicine, Autumn says.
He's also tested the gecko's adhesive properties in a vacuum and found that they would work in a spacecraft. The wheeled rovers that have been used to explore the surface of Mars have run into numerous problems, and Autumn and his colleagues are looking into whether a gecko-inspired design might make an improvement.
'Don't get me wrong,' he says. 'The current Mars rovers are awesome. But as a scientist it's my job to keep looking to the future and asking how can we do this better?'
Did he ever have an inkling that one day he'd be rethinking the design of space vehicles?
'No,' he says. 'But that's what I like about my job. It's completely unpredictable. É You can't tell in advance how valuable curiosity-based basic science will be. It's an investment in the future.'