Behold the ubiquitous gecko climbing a vertical wall in the blink of an eye or scurrying across the ceiling in gravity-defying dashes.

For at least 2,000 years people have wondered what made geckos’ feet stick, because the footpads do not feel sticky to the touch.

Finally the nanotech revolution provided the answer. Geckos’ feet are covered with millions of tiny hairs called setae.

Each seta has a dendritic structure that branches into multiple sub-fibers, which in turn break into hundreds of nano-size fibrils (spatulae) 100-200 nanometers in diameter. These are so small and get so close to the atoms of a surface that they actually bond at the atomic level via Van der Waals forces. The hairs also become more flexible as they become thinner, which helps maximize the number in contact with the surface.

The van der Waals force on each fibril is small, but their sheer numbers along with flattened tips that splay out to maximize contact even on rough surfaces provide more than enough strength to allow them to scurry along walls and ceilings.

In Van der Waals bonds, named after Dutch scientist Johannes Diderik van der Waals, electrons are not transferred or permanently disrupted from their orbitals as they are in stronger covalent and ionic bonds. Van der Waal forces arise from the "sloshing" of electrons in a cloud around atoms.

As one electron cloud sloshes it sets up sympathetic sloshing in adjacent electrons, which creates a field of "temporary fluctuating dipoles" that attract each other.

The geckos’ spatulae behave as molecular electromagnets that are attracted to atoms of the surface along which the resilient residential reptiles race.

Van der Waals forces are relatively weak compared to normal chemical bonds, but play a fundamental role in diverse fields within physics, chemistry and biology.

Van der Waals bonds are the same type that hold thin layers of graphene together to form sheets of graphite and that make atoms of the noble gases such as helium, neon and argon slightly sticky. The slipperiness of graphite and the ability of the noble gases to liquefy are both a consequence of Van der Waals forces.

Material scientists are intrigued by the possibility of sticking to and releasing from virtually any surface over and over. Applied gecko-tech could create shoes and tires that grip better, bandages and sutures that would stick better to wounds, tools that grip better in all kinds of environments, including space, and adhesives that could replace glues, solders and even Velcro.

Several different projects are under way to reproduce the tiny tendrils from various materials. One uses carbon nanotubes in place of the gecko’s spatulae, while another uses proprietary techniques to stamp nanohairy polycarbonate plastic from branched nanopores specially etched onto anodized aluminum foil.

Evolution has given the gecko the perfect molecular glue, but also the perfect way to unstick it. The gecko simply peels the individual seta away from the surface like removing a piece of tape.

Richard Brill is a professor of science at Honolulu Community College. Email questions and comments to rickb@hcc.hawaii.edu.