Geckos are the only animals their size that can walk over a ceiling without falling, according to our partner The Conversation.
This incredible faculty is due to the millions of points of contact present on the fingers of the gecko and acting like so many small suckers.
The analysis of this phenomenon was carried out by François Muller, teacher-researcher in nanosciences and nanotechnologies at ECE Paris.
Geckos are very common reptiles on Earth.
They are quite small, from 1.6 to 60 cm for a weight ranging from a few grams to over a hundred.
They are distinguished from lizards, with which they are often confused, in two ways.
First of all, geckos are remarkable vocalists.
Their name comes from the Malay "gekop" corresponding to the call produced by an Indonesian gecko that you can hear here:
All of them are membership wizards too: they can climb any surface, including smooth ones, but unlike lizards also walk and stay on a ceiling without falling.
Geckos are the only animals of this size that can do this!
This unique power, the gecko owes only to the particular structure of the inside of its fingers.
Like lizards, the gecko has pads at the ends of its fingers covered with a series of lamellae made up of ultra-fine hairs, about 10 times finer than a hair.
This structure is dense: every square millimeter is covered with more than 10,000 of these hairs.
It allows geckos and lizards to climb on most vertical, smooth or rough surfaces.
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Point of view of the world of tomorrow: The grip of the gecko
But, unlike lizards, with the gecko it doesn't stop there: each of its hairs is made up of even smaller hairs.
You can imagine the gecko's pads as combs, each of whose teeth is itself a comb.
This structure allows the gecko to have millions of points of contact with the surface like so many small suckers.
There is a small local adhesion force between each of the small suction cups and the surface, which added over the millions of contacts, gives an incredible, oversized adhesion force.
Geckos have so many suckers that they only need one leg to catch up!
Pads of a Tokay Gecko, on which we can clearly see the lamellae composed of ultra-fine hairs © Shimbathesnake / Wikimedia CC BY-SA
These bristles are very sticky with all materials in almost all conditions, but do not stick together.
No risk of their legs sticking together.
In addition, the pads of the geckos are always clean, while they do not groom their paws.
Their paws do not get dirty on contact with surfaces or at least they clean themselves.
With all this, you may wonder how the geckos manage to take off in order to move.
Quite simply ... by raising your paw!
They just have to pull on one paw while changing the orientation of the bristles a little so that the little suckers all come off immediately.
It's completely mechanical!
And geckos are able to do this in less than a second!
Hence their speed of movement regardless of the surface, the conditions and their posture.
Our "Animals" file
The discovery of this structure of gecko cushions is quite recent since it dates back to the 1990s. The understanding of the physical mechanisms involved in this incredible adhesive of gecko legs has also been a long time to determine.
Even if there are practical questions unanswered, engineers cannot miss such interesting properties to create extraordinary adhesives, always clean that can be peeled off at will.
Imitation of gecko structures could one day allow us to walk on the ceiling!
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This analysis was written by François Mulet, teacher-researcher in nanosciences and nanotechnologies at ECE Paris.
The original article was published on The Conversation website.
Declaration of interests
François Muller does not work, does not advise, does not own shares, does not receive funds from an organization that could benefit from this article, and has not declared any affiliation other than his research organization.
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