http://faculty.washington.edu/bergs/Gecko_Adhesion.html
Gecko feet inspired Gecko Tape
How a gecko lizard can run so effortlessly up and down a wall has caught the attention of many
observers, starting with, and likely before, the recorded observations of Aristotle. (Ref. 1) Some previous
hypotheses were: geckos have a sticky liquid adhesive that is secreted, that they had suction cups to hold
on, or that that they had microscopic hooks to help them cling. All were found to be wrong. Then around
the year 2000, Robert Full discovered that millions of hairs called setae used van der Waal’s
intermolecular force to attract to surfaces. (Ref. 4) This force is due to moving electrons which attracts
molecules together. And example would be water droplets “sticking” to a ceiling or water surface tension.
This particular force is a very weak force but when hundreds of thousands work together, an 8 in X 8 in
piece of this bioinspired tape can hold up the entire adult male who made it, Stanislav Garb at the
University of Kiel Germany. (See picture – Ref. 3)
The Gecko Tape product was inspired by the foot pad of the Gecko lizard. This tape was inspired
by the foot pad of the gecko. The toepad consists of hundreds of thousands of keratin made setae that
have smaller projections with a flat top called a spatula. In 2003, Andre Geim from the University of
Manchester successfully mimicked these using a synthetic material and created “tape” from it. (Ref. 4)
This new tape works in the same way a gecko’s setae works, when more force or sheer is needed, more
setae hairs are attracted to the surface because more touch the surface. (Ref. 3)
http://beacon-center.org/wp-content/uploads/2011/11/Pic3.jpg
These are setae hairs with spatula ends.
Click here for zoom in animation
Click here for good video by Robert Full
This new GSA, Gecko inspired tape, works the same way using a hard plastic microfiber made in
a similar process and microchips, creating a reusable synthetic adhesive with no residue or does not need
high pressure to work. Some of the uses discussed by this product were medical equipment, sporting
goods, robots for search and rescue, and military uses. (Ref. 5)
There was not a very large market for this product for many years. There are many challenges
that cause this product to not to be sold commercially. To synthesize these keratin setae is very expensive
and difficult. Hundreds of thousands of synthetic plastic setae must be made similar to the way computer
chips are made. Only small pieces are able to be made at a time. (Ref. 5) Other problems that occur with
this product are that it works by sliding, so it is one directional and load dependant. On the other hand,
this new tape can be reusable, can withstand a lot for force, and leave no goo type residue. (Ref. 6)
Two new ideas that are currently succeeding in possibly finding a larger market are medical
bandages and an entirely new tape inspired in a new light using the same gecko foot. MIT researchers,
Robert Langer and Jeff Karp, successfully created a waterproof bandage that may revolutionize part of the
medical field. Their “biorubber” pillar pattern, based off of the bioinspired gecko setae pattern, can patch
up internal wounds, it is safely biodegradable, and causes no inflammations, its elastic, and can work in
wet environment using a sugar based glue. (Ref. 7) But over at the University of Massachusetts Amherst,
Alfred Crosby looked at the /Gecko foot with a fresh perspective. He skipped the setae altogether and
focused on the skin, tendons, and bone of the foot. His adhesive pad attached to a “stiff fabric tendon” can
hold up to 700 lbs if the size of an index card, as he demonstrated using his bioinspired gecko tape
product by holding up a 42 in flat screen TV with his tape. (Ref. 8- Click here to see the demo) Looking
at the foot in a new light may be the key for globalized use.
I don’t think this product is a societal win, at least not yet. To make the setae gecko tape with
silicon or plastics synthetic materials will not be good for the environment. The amount of resources,
energy, and cost to make the tape does not justify, in my opinion, the uses we get from the product. It is
too limited with its one directional sliding adhesion. With that said, the medical bandages mentioned that
are biodegradable may change my mind.
I am not convinced this is true biomimicry because of the sustainability of future species. Using
hard plastics as most have done is not going to preserve a positive environment for future generations.
The gecko’s setae are made from keratin and the industry is mostly using silicon and hard plastics. So it
is not really like true setae.
The new biodegradable bandages work the same way but uses a sugar glue for the wet
environment, which never lets go, while a geckos foot is designed to release and grab, and uses no sugars.
So in my opinion the gecko tape was inspired by nature, but is not true biomimicry.
Links:
1.
Geckos stick to any surface.
http://faculty.washington.edu/bergs/Gecko_Adhesion.html
2.
Good Robert Full video
http://www.youtube.com/watch?v=JnBkbaFsZOY&feature=related
3. University of Kiel Germany- Man canhang from ceiling
http://news.discovery.com/tech/gecko-tape-111107.html
4. Gecko foot structure with animation
http://www.stanford.edu/group/mota/education/Physics%2087N%20Final%20Projects/Group%20Gamma
/gecko.htm
5. University of California Berkley Smart Gecko Tape
http://robotics.eecs.berkeley.edu/~ronf/Gecko/interface08.html
6. Scientific Journal Mechanism of adhesion
http://intl-icb.oxfordjournals.org/content/42/6/1081.full
7. MIT bioinspired bandages
http://web.mit.edu/newsoffice/2008/adhesive-0218.html
8. Using skin, tendons, and bones—not setae hairs
http://www.pse.umass.edu/~acrosby/Adhesion.htm
9. van der Waals intermolecular force animations
http://www.educationscotland.gov.uk/highersciences/chemistry/animations/intermolecularforces.asp