Hairy spider legs inspire engineers

In Self-Publishing on March 24, 2010 at 8:07 pm

GAINESVILLE, Fla. – Despite the leaps and bounds that science and technology has made over the past century, sometimes it can still be beaten.

“You see that nature can do something we can’t do yet in science,” said Wolfgang Sigmund, a University of Florida professor in the department of materials science and engineering.

In this case, that “something” is leg hair. Spider leg hair, actually.

People have often observed the amazing properties that water spiders possess in order to walk along the surface of lakes and ponds. This natural feat was the impetus behind one of Sigmund’s current projects to create a surface material that would be equally as “hydrophobic” or water repellant.

After two years of research, Sigmund and his team have successfully generated an artificial material that mimics the hairy structure found on spiders with nearly perfect hydrophobic response.

Positive results are rewarding for the team, Sigmund said. Scientists and researchers are always working on several topics because the outcomes are never predictable. If something doesn’t work, the experience is valuable because the unworkable principles are isolated. But when something does work, it means a lot to the team.

But persistence is key. This project actually began with three student researchers, but two students gave up, Sigmund said. It was the final student, Shu-Hau Hsu, who was able to make the breakthrough. But even he needed some convincing.

“To be honest with you, in the beginning, I was reluctant to do the project,” said Hsu, 34, a Ph.D. candidate in materials science engineering.

Typically, Hsu had worked with rigid materials such as metals or ceramics. Biomimetics, the field that deals with studying and replicating natural life forms and processes, was new to him. So were its softer and more pliable materials.

But it turns out, the components aren’t that exotic.

It’s plastic from a report cover. Yep, the kind you once used for your book reports.

“The material isn’t special,” Hsu said. “I got it from Office Depot.”

His process, however, was different. Other researchers started off the same way Hsu did, by binding a porous material to the plastic. But instead of melting off the porous material like they did, Hsu just peeled it off with his fingernails.
This created a surface where the fibers were uneven, irregular and more like you would find on a spider.

At microscopic levels, photos depict an orb of water sitting on the structure, without spreading over its surface in the slightest. But when applied, water quickly speeds off at rates much faster than normal movement.

And because this is due to the physical properties of the surface and not chemicals, there are less health risks to humans, pets and the environment, Sigmund said.

Another potential use illustrated in this and other research is the self-cleaning property of hydrophobic surfaces.
In a video of water being applied to the new material, a sample coated in carbon dust is completely cleaned by just a few droplets.

And not only is the surface clean, but very little energy and force is required to get the results, which is important when considering energy conservation and efficiency. Boats, batteries and solar panels could all be improved if a construction materially possessing these abilities could be successfully engineered.

In its current state, the artificial hairs aren’t sturdy enough for boating. Scratching the material will destroy it. But Sigmund isn’t deterred.

With an initial success, the methods and future projects become believable for funding sources, he said. And there’s no limit to the varieties of materials that can be used in research to make the artificial hairs more durable.

All it takes is a few little hairs to open up the door.


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