The tokay gecko is the largest animal living today that uses adhesion for locomotion.
Adhesion is the ability of one thing to stick to another. In biology, it's the evolutionary quality that allows certain small creatures, like insects -- and lizards -- to climb up walls and perch on ceilings.
"Geckos are really cool animals," said Alfred J. Crosby, a polymer research scientist from the University of Massachusetts. "They have the ability to hang in any position, to do it over and over again and do it on a wide range of surfaces."
For a long time, scientists have been trying to mimic gecko adhesion in hopes of creating a product that could be used commercially.
But until Crosby and his research partner Duncan J. Irshchick, a UMass biologist and gecko expert, invented "Geckskin," no one had been able to do it on a large scale.
"They were missing something," Crosby said.
Crosby explained the development of Geckskin to a standing-room only crowd of HCC students and staff this week. He was invited to speak by chemistry professor Diane Stengle as part of HCC's BSTEM Speaker Series.
The last great innovation in binding two pieces of material together was Velcro, said Crosby.
"That was 50 or 60 years ago," he said.
He noted that there are many limitations to the generally accepted methods people use for attaching items together. Nails and screws, for example, leave holes in walls. Glue and tape leave tacky residue.
Crosby said the goal behind Geckskin was to create a new product that was strong, non-damaging, reusable, and could be used on multiple surfaces.
The mistake other scientists made was in trying to copy the exact features of the gecko feet, which are covered in tiny scales called "lamellae" that are in turn covered with microhairs ("setae") that split still further into even tinier fibers, 5 nanometers wide, or the size of 50 atoms.
"They have a single protein molecule at the tip," he said. "That's how fine it is."
For decades, scientists tried to reproduce these "microfabricate setae," he said. They were able to do it on small scales (for example, hanging a college textbook to a wall) but large-scale uses remained elusive.
The answer to gecko adhesion, Crosby said, was in understanding the physics.
"The hairs were a distraction," Crosby said. "We didn't simply want to copy the gecko. Geckskin is based on math and not on mimicry."
Once they understood the physics behind gecko adhesion they were able to reproduce it using some fairly simple and available products, mainly fabric (nylon, Kevlar, carbon) and bathroom caulking material.
The result is a product that can stick to any smooth surface, including glass, support items up to 700 pounds and can be easily reused.
Crosby said he and Irschick have five patents pending for Geckskin and co-founded a company to develop commercial applications. He said more than 60 companies have contacted them expressing interest in Geckskin.
"So hopefully you guys can use it," he said.
Photos: (Left) Alfred J. Crosby, a polymer research scientist from the University of Massachusetts, explains Geckskin at HCC. (Right) HCC students check out some samples of Geckskin.