Clinging to the Ceiling

"Those rugged little bodies whose parts rise and fall in various inequalities,
Hills in the risings of their surface show,
As valleys in their hollow pits below."
- Richard Leigh, 'Greatness in Little'

Image of a gecko's foot

    Gecko's have an astonishing way of adhering to walls and ceilings with little to no effort exhorted. Something is holding it to the wall, but it is not it's muscles. For centuries, scientists have wondered how these animals can run up and down any kind of surface with no trouble. Geckos are a group of nocturnal lizards with about 850 species in all. They can be found all across the southern continents. The gecko that has the most research done on is the Tokay gecko (Gecko gecko), a large Asian species.
   The gecko began to appear in science in the mid-1990s because of Professor Bob Full's Polypedal Lab. He is an expert on animal locomotion meaning he belongs to the biomechanic wing in bio-inspiration. Much of his previous work was focused on insect motion but when he noticed the adhesive quality that gecko's have, he became interested right away. Full also involved Kellar Autumn in his work. Autumn studied geckos for most of his professional life. They wanted to find the exact principle at work that made the geckos feet adhesive and then apply it to a technical system. Autumn thought that the feet of a gecko was the most interesting. To the human eye, the pad of a geckos foot is crossed by transverse bands that look like reptile scales. It was not until the application of the electron microscope that they saw that the geckos foot had tiny bristles on the toes (about 500,000 on each foot). The ends of the bristles then fork out to between 100-1,000 mini-bristles. Just one gecko has about one billion of these points of contact. These bristles are the reason why the gecko can stick to anything. The bristles also don't need any muscle activation for them to stick, so a gecko can still stick to things when it's dead.

    Autumn's team found the force of a single gecko bristle to be 10 times more than you would have expected given the amount of bristles on the foot. If all of the bristles came in contact at one time on a surface then it would be able to support a 264 pound man. This is actually opposite to the Lotus-Effect because it created many contact points for a better adhesion. Ron Fearing also contributed to this work when he realized that it is not just the nervous systems of creatures that enable them to pull off incredible physical tasks, but most of the time it is the mechanics. Scientists immediately wanted to find ways in which this mechanism could be fabricated.
    They soon realized that creating a design for this would be difficult since human technology has not been able to create "bristle-like" products small enough to be compared to a gecko. The lab of Andre Geim used an atomic force microscope to create dimples in a wax surface to be used as a mold to make plastic pillars to mimic a gecko's bristle. The pillars were not exact comparisons but they were able to use it to create 'gecko tape'. The tape had limitations because the plastic was soft and after a few uses the pillars would stick together. The tape would also become very dirty after uses.
    Scientists then noticed that bristles needed to be compliant. They needed to have flexibility. Fearing notes that the soft sticky surface and the flexible backing is two levels of compliance. These ideas were compiled into the gecko mechanism and was patented by the Autumn/Full/Fearing team on May 18, 2004.
    For a long time people thought that there was something magical about the gecko. But it only comes down to the nanostructure of these animals that makes them so special. There are also many other animals that have this adhesive quality including beetles, flies, spiders and other lizards. It is also found that the larger the animal the more finer the bristles become.



Below is a video about Bio-inspiration to help you understand a little more about what it is:
3:50-7:08 goes into specific details about the gecko's foot with Bob Full and Ron Fearing.