Gecko lizards, which can climb any vertical surface and hang from a ceiling with one toe, have fascinated scientists for a long time. Their foot-hairs have a structure which allow them to strongly adhere to any type and shape of surface. Now, according to this short news release from the National Science Foundation (NSF), researchers from the University of Akron, Ohio, have developed synthetic hairs from multiwalled carbon nanotubes (MWNT) that have adhesion forces 200 times higher than those observed with gecko foot-hairs. This could lead to new dry adhesives used in microelectronics, robotics or space applications. Read more.
Here is the first paragraph of the NSF press release (here is another link if you want to see a picture of a gecko lizard).
Renowned for their ability to walk up walls like miniature Spider-Men--or even to hang from the ceiling by one toe--the colorful lizards of the gecko family owe their wall-crawling prowess to their remarkable footpads. Each five-toed foot is covered with microscopic elastic hairs called setae, which are themselves split at the ends to form a forest of nanoscale fibers known as spatulas. So when a gecko steps on almost anything, these nano-hairs make such extremely close contact with the surface that they form intermolecular bonds, thus holding the foot in place.
So researchers from the University of Akron, helped by a $400,000 grant from the NSF, have developed synthetic hairs from carbon nanotubes that have adhesion forces 200 times higher than those observed with gecko foot-hairs. Here is a link to their own news release.
They built new structures, based on multiwalled carbon nanotubes (MWNT) constructed on polymer surfaces with strong nanometer level adhesion. These structures can be used as dry adhesives similar to or stronger than gecko foot-hairs.
Here is an example of such nanostructures.
The pictures above illustrate the topography and force measurement of multiwalled carbon nanotube brushes on PMMA with a scanning force microscope (SPM). (A) and (B) show real SPM height images taken by tapping mode for vertically and horizontally aligned MWNT, respectively. The bars represent 5 nm and 150 nm, respectively (Credit: University of Akron).
There were never in the world two opinions alike, any more than two hairs or two grains. Their most universal quality is diversity.
—Michel de Montaigne (1533–1592)
[Note: PMMA, which stands for Poly (methyl methacrylate), is a transparent plastic sold under different names, such as Plexiglas, and is often simply called Acrylic.]
The research paper about this work has been published by Chemical Communications on July 5, 2005 under the title "Synthetic gecko foot-hairs from multiwalled carbon nanotubes" (Issue 30, 2005, Pages 3799 - 3801). Here is a link to the short abstract.
We report a fabrication process for constructing polymer surfaces with multiwalled carbon nanotube hairs, with strong nanometer-level adhesion forces that are 200 times higher than those observed for gecko foot-hairs.
The full paper is available for free for registered users of the Institute of Physics for a duration of one month. Here is a link to this paper (PDF format, 3 pages, 313 KB).
For more information, you also can read a previous entry about a related project, "Spider Legs Lead to Better Post-it Notes."
These two projects don't follow the same approach, but they have a similar goal: design improved adhesives that will have critical applications in microelectronics, information technology, robotics, space and other areas.
Sources: National Science Foundation news release, via EurekAlert!, August 15, 2005; and various web sites
I believe in the total depravity of inanimate things ... the elusiveness of soap, the knottiness of strings, the transitory nature of buttons, the inclination of suspenders to twist and of hooks to forsake their lawful eyes, and cleave only unto the hairs of their hapless owner’s head.
—Katharine Walker (1840–1916)
Related stories can be found in the following categories.
Chemistry
Materials
Nanotechnology
Nature
Science
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