So I'm sitting on the porch of my hut in the Kruger National Park and a pale gecko peers from beneath the rim of the lantern which is glowing on the wall, attracting all sorts of no doubt scrumptious gecko snacks.
The pale wall crawler demolishes his prey with ease, padding straight up vertical walls and even hanging nonchalantly beneath the lantern post eyeing an unlucky insect.
The little guy's gravity-defying abilities stem from millions of minuscule hair-like fibres underneath the pads of his feet known as setae.
These nanoscopic bristles not only enhance the gecko's grip because of their ability to penetrate every available space in a surface, but also because of Van der Waals forces, as molecules that are close together are attracted to each other.
When Jeffrey Karp and his colleagues at the Brigham and Women's Hospital in Boston, Massachusetts set out to develop medical tape to close wounds, they turned to the incredible abilities of the gecko for inspiration.
Karp recalls that "a lot of people were working on gecko-inspired adhesives", but their creations tended to lose their bonding properties when wet and were not biodegradable, making them unsuited to the medical applications he envisaged.
Karp and his team created a tough and elastic polymer, labelled PGSA, for their tape, pressing it into thin sheets.
The material causes little inflammation on contact with human tissues and is fully biodegradable after a few days or weeks, which is more than enough time for human wounds to heal.
To mimic the stickiness of a gecko's feet, the team etched the sheets of PGSA to create nano-scopic pillars - about a million per millimetre - across the surface. The massive surface area created means that the PGSA tape sticks to flesh like a gecko to a wall.
But a gecko is able to cling motionless to a wall for hours before releasing its hold and flitting across the surface at speed. Karp explains: "Geckos can adhere and de-adhere. Otherwise you'd see a lot of unhappy geckos hanging around on the walls."
In nature, the Van der Waals forces attracting the gecko's feet to whatever it's hanging on to are not that strong and remain effective only because of the gecko's light weight.
In medical applications, however, the bond between the PGSA tape and the tissue beneath has to be very strong to be viable.
To increase the stickiness factor, Karp and his team coated the nano-pillared surface with a thin layer of a complex sugar, called dextran, which forms a more permanent chemical bond with human tissues.
The coated PGSA was tested on a pig's intestines and found to be at least twice as sticky as the untreated sheets, withstanding a pull of three to five newtons before losing its grip.
The amazing adhesive properties of the tape are likely to make it a staple in general practitioners' rooms and surgical theatres, where it may soon replace the glues, sutures and staples used to close cuts and wounds.
The biodegradable qualities of the material mean that it can also be used internally.
With improvements in stickiness as research progresses, Karp believes that the PGSA tape will be able to withstand rigorous movement, hinting at the implications for its future abilities to help heal the human heart.
- bigeyeddeer2008 @gmail.com