Existing solutions for gluing foam materials to metals and plastics can make it virtually impossible to disassemble the parts for recycling. Now, the Blue Oval is looking to the gecko for inspiration as part of a joint research project with Procter & Gamble.
The gecko’s phenomenal ability to adhere itself onto just about any surface has been known since the time of Aristotle: A large example weighing somewhere in the region of 150g could theoretically support upwards of 40 kg if it gripped with all four feet. Just as impressive is the fact it does so without secreting any substances and that it can pull its feet off the surface with ease.
While the gecko’s ability is well documented it wasn’t until 2002 that researchers fully grasped how it takes place. The answer lies with millions of tiny hair-like structures known as setae found on their feet. The molecules within these have an imbalanced distribution of electrons; their overall charge is neutral, but they can generate an attractive force when placed near other imbalanced molecules.
These so-called van der Waals forces are relatively weak in isolation, but they become significant when spread across millions of points. More importantly for Ford and other companies engaged in this research, the gecko can overcome these forces at will.
The key to the release mechanism is a specially evolved joint that allows the gecko to hinge its toes upwards. While the van der Waals forces present a very strong combined effect when the setae are perpendicular to the surface this rapidly breaks down as the orientation changes. Starting with the tips of the toes, the gecko can peel its feet away from the surface. It’s a bit like removing a plaster – the force required would be huge if you tried to lift the whole area in one go, but it becomes quite easy if starting at one edge.
The race is now on to replicate this behaviour synthetically. Ford is by no means the only company looking into it, and potential solutions include synthetic setae made from polymers or carbon nanotubes.
“Solving this problem could provide cost savings and certainly an environmental saving,” commented Debbie Mielewski, senior technical leader for plastics and sustainability research at Ford. “It means we could increase the recycling of more foam and plastics, and further reduce our environmental footprint.”