Cluster researcher Zhenhai Xia uses carbon nanotubes to make a gecko-inspired dry adhesive

Materials Modeling 

If Spiderman were real, his hands and feet would work like gecko feet, says Zhenhai Xia, a member of the Materials Modeling research cluster and the Center for Advanced Scientific Computing and Modeling at UNT. Geckos can climb any vertical or horizontal surface, sticking to it and detaching easily while their feet stay clean.

The quick-release adhesion is attributed to the unique structure of the millions of microscopic hairs on their feet and van der Waals force, which allows them to generate a strong adhesion force to defy gravity but easily detach from a surface by peeling their feet away.

Xia was part of a team of researchers, led by Liming Dai of Case Western Reserve University, who made gecko-inspired dry adhesive that was 10 times stronger than gecko feet by mimicking gecko footpads using carbon nanotubes. The palm-sized adhesive was estimated to be strong enough to support a 200-pound man climbing a wall, but easy to remove and re-adhere upon many reapplications. Their research was published in Science magazine. Because of the tubes' strength and flexibility, they also could be used as structural material in such things as car parts and baseball bats.

Zhenhai Xia

Zhenhai Xia, associate professor of materials science and engineering, explores the micro hairs of gecko feet for his research on dry adhesives.

Photo by: Jonathan Reynolds

Now, Xia, associate professor of materials science and engineering, is further exploring the hair of gecko feet. His team has discovered a self-cleaning mechanism in the feet and, based on the finding, will create artificial gecko feet for testing.

The research could be used to help create dry synthetic adhesives that would be strong and reusable, remaining sticky and clean after each application. The advanced adhesion technology could be used for applications such as bonding material in the biomedical field or electrical components. He is hoping the research also could lead to cheaper ways to fabricate the adhesive.

Xia focuses on biomimetic research, which looks to nature to design materials and devices. Nature has had millions of years to perfect the design of animals and plants, he says, and from it we can learn to create new, better and greener materials.

"As scientists, we need to solve big problems," Xia says. "If we solve big problems, we make life easier and help protect the environment."

Xia also has been researching how to improve clean-energy technology for cars and power plants. He was part of a team that had a breakthrough in fuel cell technology, discovering that nitrogen-doped carbon nanotubes are nearly four times better than platinum as a catalyst and could eventually replace it in fuel cells. These findings also were published in Science.

Xia says the high cost of platinum is one of the major barriers for fuel cell commercialization. Carbon is easy to find and cheap to mass produce, so it is a more renewable resource than platinum. Carbon nanomaterial also is a better catalyst for oxygen reduction -- a key chemical reaction that generates electricity in fuel cells -- so it can make a clean technology better and cheaper. Xia is now working to better understand the catalytic mechanisms in fuel cells.

— This article originally appeared in the 2013 edition of the UNT Research Magazine