Gecko feet inspire a powerful new band-aid

Geckos can walk on ceilings upside down, performing this gravity-defying feat thanks to their unusual feet, which are ultra sticky. Now researchers at MIT and Harvard have been inspired by the stickiness of gecko feet to design a super sticky, waterproof and biodegradable bandage. This band-aid is so good that it can be used to seal surgical wounds instead of sutures, its inventors say. The bandages would dissolve harmlessly and be absorbed by the body, they say.

The team that developed the bandage was led by Jeff Karp of Brigham and Women's Hospital and Harvard Medical School, and Robert Langer of MIT.

The reason geckos do not drop from the ceiling while scurrying upside down is that the undersides of their feet are covered with hundreds of thousands of tiny hairs, called setae. Each seta tip has thousands of nanoscale projections, which are so small that they allow them to produce the weak molecular interactions known as van der Waals forces. Traces of water that may be present add to this force by producing a capillary force. Taken together, the half a million odd setae on the underside of each gecko foot produce a force powerful enough to make sure that the gecko never falls. It has been estimated that a gecko foot is so sticky that it can lift an infant.

Karp and Langer and colleagues built their medical adhesive with a polymer called PGSA. PGSA is very tough and elastic and biodegrades over a period of weeks. They used semiconductor micropatterning technologyo shape the PGSA into different hill and valleys akin to a gecko's foot.

Karp then added a very thin layer of a sugar-based glue, to create a strong bond even to a wet surface.

Karp and Langer say the bandage is so powerful that there is hope that one day it can be used on the surface of the heart. However, to get to that stage, it will have to be made stickier. The current bandage is only about one-tenth as sticky as a gecko's foot.

Meanwhile, it can be used for closing wounds and cuts due to minor surgery, such as the holes left behind after laparoscopy.

"There is a big need for a tape-based medical adhesive," said Dr Karp.

The new bandage has other advantages. For example, Karp and Langer say it could be infused with drugs such as antibiotics or anti-inflammatory drugs or even stem cells that the bandage can release as it degrades. The elasticity and degradation rate of the PGSA polymer can be controlled, as are the number of setae-like pillars and valleys. This means that the new adhesives can be customized to have the right elasticity, resilience and grip for different medical applications.

"This is an exciting example of how nanostructures can be controlled, and in so doing, used to create a new family of adhesives," said Dr. Langer.


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