Stay-sticky tape inspired by geckos

Scientists followed nature's lead to come up with a dry material covered in clinging microscopic hairs.

Like a gecko's toe pads, they automatically rid themselves of larger dust particles through friction, while smaller grains disappear into grooves between the hairs.

In future, the tape could be used as an alternative to Velcro hook and loop fasteners, or to produce first aid bandages that can be opened and closed several times, say the researchers.

It took scientists many years to fathom out how geckos are able to scurry up vertical walls and even hang upside down from ceilings.

The lizards employ no glue or suction devices. Instead, millions of tiny hairs on each toe exploit an electrical quantum effect that maintains a firm grip even on polished glass.

Molecules and atoms exert a weak attraction when they are brought extremely close together due to Van der Waals forces which involve the random movement of electrons.

Because of the large number of microhairs on its feet, the gecko is able to amply the effect until it greatly outweighs gravity.

The new sticky material developed by German and US scientists employs artificial elastic mushroom-shaped microhairs.

In their experiments, the researchers substituted tiny glass beads for grains of dust.

When the bead diameter exceeded that of the microhairs, the material lost stickiness after first contact but regained up to 100% of its adhesive power with a few repeated applications.

With a sphere size smaller than the microhairs, a third of the original clinging force was restored.

"Such a tape might be applied in the sports sector, in medicine, automotive industry or aerospace technology," said Professor Metin Sitti, a member of the team from Carnegie Mellon University in the US.