Self-cleaning sticky stuff

For years, scientists have been trying to develop a man-made adhesive by mimicking the properties of the toe hairs of the gecko.

Earlier this year, one set of researchers, led by Ron Fearing, a University of California, Berkeley professor of electrical engineering and computer sciences, developed such an adhesive using polymer microfibres that could easily attach to and detach from clean surfaces.

But replicating the gecko's ability to walk through dirty surfaces yet keep its feet clean enough to climb walls has been tricky. In 2005, research led by Kellar Autumn, associate professor of biology at Lewis & Clark College in Portland, Oregon, revealed that a gecko keeps its feet sticky but clean by shedding dirt particles with every step.

And now, Fearing's group has created the first adhesive that can clean itself after each use. To do so, the researchers designed the adhesive with microfibres made from stiff polymers.

Using microspheres 3 to 10 micrometres in diameter to simulate contaminants, the researchers showed that the microfibres pushed the microsphere particles toward the fibre tips when the adhesive was not in contact with a surface.