Featured Research

from universities, journals, and other organizations

Climbing The Walls? New Adhesive Mimics Gecko Toe Hairs

Date:
January 30, 2008
Source:
University of California, Berkeley
Summary:
A new anti-sliding adhesive developed by engineers at the University of California, Berkeley, may be the closest man-made material yet to mimic the remarkable gecko toe hairs that allow the tiny lizard to scamper along vertical surfaces and ceilings. The researchers say that such an adhesive could one day be used to outfit a small robot that could climb up walls.

Researchers have developed a directional adhesive, inspired by the gecko, using microfibers made from a hard polymer, polypropylene. The polymer fibers are 600 nanometers in diameter, just 1/100 the diameter of a human hair, and are formed by a casting process. Like the gecko, the synthetic microfiber array is not sticky except when fibers slide a small distance along a surface.
Credit: J. Lee and R.S. Fearing, UC Berkeley

A new anti-sliding adhesive developed by engineers at the University of California, Berkeley, may be the closest man-made material yet to mimic the remarkable gecko toe hairs that allow the tiny lizard to scamper along vertical surfaces and ceilings.

The researchers say that such an adhesive could one day be used to outfit a small robot that could climb up walls.

Taking a cue from the millions of hairs covering a gecko's toes, researchers squeezed 42 million hard plastic microfibers onto each square centimeter of material and loaded it with various weights. They found that on a smooth, clean, vertical surface, two square centimeters of the synthetic adhesive could hold 400 grams (0.88 pounds). At the same time, the adhesive easily lifts off with minimal force and no residue.

Scientists have long marveled at the gravity-defying feats of the gecko, and a number of research teams across the world are working on duplicating the lizard's adhesive forces. Fearing notes that previous research on gecko-like adhesives has focused on the strength of the adhesion. He said that the ease of attachment and detachment are equally important when developing a material that can practically be used for scaling vertical walls and ceilings.

What sets this new gecko-inspired adhesive apart from the others created thus far is that it is directional, only "sticking" when it slides along a smooth surface, not when it is pressed down.

"This difference is critical because if you're climbing up vertical surfaces, you can't afford to use a lot of energy pressing down into the surface to stick," said Ron Fearing, UC Berkeley professor of electrical engineering and computer sciences and head of the research team developing this new material. "Using force to attach also requires force to detach. A gecko running uphill may be attaching and detaching its feet 20 times a second, so it'd get very tired if it had to work hard to pull its feet off at every step."

The microfibers, made of polypropylene, are 20 microns long, or one-fifth the thickness of a sheet of paper, with a diameter of 0.6 microns, or one-hundredth the diameter of a human hair.

The structure is similar to a microfiber array developed by the same group in 2006. That material relied upon friction to work, however, requiring the application of force to make it stick. Changes made to the plastic backing enabled the directional adhesion reported in this new material to work on truly vertical surfaces.

"For a gecko, this seemingly subtle change could mean the difference between life or death," said Fearing. "With friction only, a gecko would fall from a wall or ceiling. With directional adhesion, a gecko can stop itself from falling because the mechanism works without the need for force that is perpendicular to the surface."

The new research is described in a pair of papers published online Jan. 23 in the Journal of the Royal Society Interface. Members of Fearing's UC Berkeley research team are Jongho Lee, a graduate student in mechanical engineering, and Bryan Schubert, a graduate student in electrical engineering and computer sciences. Co-author Carmel Majidi, a former UC Berkeley graduate student in electrical engineering and computer sciences, is now a post-doctoral researcher at Princeton University.

"This is a major milestone in the new field of gecko-inspired adhesives," said Kellar Autumn, associate professor of biology at Lewis & Clark College in Portland, Ore., who is considered one of the nation's leading experts on gecko movement and who was not a co-author on this latest research. "Fearing's adhesive is made from a plastic that is very hard - like real gecko protein - so it is not 'sticky' to the touch. Also, just like what we found in real gecko foot hairs, Fearing's microfiber arrays are sticky only when they slide across a surface. This could be the first real gecko tape."

Fearing and his colleagues are part of a Nanoscale Interdisciplinary Research Team supported by the National Science Foundation and specifically tasked in 2003 with developing synthetic adhesives that perform like gecko hairs.

In 2000, Fearing teamed up with biologists Robert Full at UC Berkeley and Autumn at Lewis & Clark, and engineer Thomas Kenny from Stanford University, in the first study pointing to the secret of gecko adhesion: intermolecular van der Waals forces that remain weak until surfaces get intimately close. Two years later, members of this same team synthesized gecko hair tips that stick, providing the first direct experimental verification of a van der Waals mechanism for gecko foot-hair adhesion.

Not only is each gecko toe covered by millions of tiny hairs, but those hairs are further split at the end into billions of nanoscale spatulae. The van der Waals forces come into play when these spatulae make contact with the surface.

This new material is also an example of a "smart adhesive," becoming stronger with use, said Fearing, who is also part of UC Berkeley's Center for Information Technology Research in the Interest of Society. "More microfibers bend and engage automatically as the weight increases. When the load is removed, the microfibers disengage. This allows for controlled attachment and detachment and is a critical innovation for clean release and reuse. It's the first time this has been demonstrated with a hard microfiber array."

Another benefit to using hard polymers is that the fibers are less prone than softer plastic to collecting dirt after repeated use.

So far, the new adhesive only works on smooth, clean surfaces. The next step, said Fearing, is to develop a material that can also adhere to rough surfaces and that is self-cleaning.


Story Source:

The above story is based on materials provided by University of California, Berkeley. The original article was written by Sarah Yang. Note: Materials may be edited for content and length.


Cite This Page:

University of California, Berkeley. "Climbing The Walls? New Adhesive Mimics Gecko Toe Hairs." ScienceDaily. ScienceDaily, 30 January 2008. <www.sciencedaily.com/releases/2008/01/080129201546.htm>.
University of California, Berkeley. (2008, January 30). Climbing The Walls? New Adhesive Mimics Gecko Toe Hairs. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2008/01/080129201546.htm
University of California, Berkeley. "Climbing The Walls? New Adhesive Mimics Gecko Toe Hairs." ScienceDaily. www.sciencedaily.com/releases/2008/01/080129201546.htm (accessed April 23, 2014).

Share This



More Matter & Energy News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com
China Falls for 4x4s at Beijing Auto Show

China Falls for 4x4s at Beijing Auto Show

AFP (Apr. 22, 2014) The urban 4x4 is the latest must-have for Chinese drivers, whose conversion to the cult of the SUV is the talking point of this year's Beijing auto show. Duration: 00:40 Video provided by AFP
Powered by NewsLook.com
Lytro Introduces 'Illum,' A Professional Light-Field Camera

Lytro Introduces 'Illum,' A Professional Light-Field Camera

Newsy (Apr. 22, 2014) The light-field photography engineers at Lytro unveiled their next innovation: a professional DSLR-like camera called "Illum." Video provided by Newsy
Powered by NewsLook.com
3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

TheStreet (Apr. 22, 2014) Sales of motorcycles have continued to ride back from the depths of hell known as the Great Recession. Excluding scooters, sales of motorcycles increased 3% in 2013. In units, however, at 465,000 sold last year, the total remained about 50% below the peak hit in 2007. Industry leader Harley Davidson’s shareholders have benefited both by the industry recovery and positive headlines emanating from the company. Belus Capital Advisors CEO Brian Sozzi takes you beyond the headlines of the motorcycle maker. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins