Gecko foot

Pictured: Close-up of the underside of a gecko’s foot as it walks on a glass wall. Van der Waals force interactions between the finely divided setae (hairs on the toes) and the glass enables the gecko to stay in place and walk on the seemingly smooth glass.

gecko grippers – Gecko feet have branched systems of tiny hairs that use a type of molecular attraction known as the van der Waals force to stick to a surface with minimal effort, and can easily turn the force on or off. The grippers are not an exact replica of the structures on actual geckos’ feet, but they have synthetic hair structures called stalks that mimic the real thing. The tip of each stalk basically acts like a tiny suction cup. When force is applied to the stalks, adhesiveness is activated, whereas relaxing the force turns the stickiness off.

What’s the problem?

  • Ask – Many of the satellites that have been launched have stopped functioning. Now they are space junk and could be a hazard for other satellites and spacecraft. How can these be collected?
  • Imagine – The grippers are being developed as part of NASA’s Phoenix program, to work on new technologies that could allow for components from non-functioning satellites still in orbit to be harvested and re-used.
  • Design, Build – researchers tested the grippers in weightless conditions aboard NASA’s C-9B parabolic flight aircraft, where they were able to grapple not only a 20-pound (9-kg) cube as it floated around, but also one of the researchers wearing a special suit made of spacecraft material panels, standing in for a 250-pound (113-kg) object.
  • Improve

That’s engineering

  • adhesive – (glue, cement) – any substance applied to the surfaces of materials that binds them together and resists separation.
  • van der Waals force – an unusual quirk of physics that occurs when electrons orbiting the nuclei of an atom are unevenly distributed, creating an electric field with a positive and negative pole.
  • van der Waals force – The ability of geckos – which can hang on a glass surface using only one toe – to climb on sheer surfaces has been attributed to the van der Waals forces between these surfaces and the spatulae, or microscopic projections, which cover the hair-like setae found on their footpads.

Engineering ideas

  • van der Waals force, molecular attraction, mimic, suction, adhesive, stickiness, microscopic

Do It
Challenges for you to work on…

  • where could “gecko-feet” be