Gecko Feet do Not Permanently Adhere
Adhesives are very useful tools, whether we are putting paintings or electronics on a surface, but sometimes we do not want to leave a residue behind or want to remove the object later. One possible solution is to apply the physics that allow geckos to walk upside-down on seemingly smooth surfaces. Researchers at Linköping University however have found that the physics involved are not permanent, and so may not be the best choice for all applications.
All molecules and atoms are attracted to each other by van der Waals forces. These are weak forces though, so you cannot expect to climb a wall just by pressing your hands against it. Geckos and spiders however have evolved special hairs that are able to get so close to a surface and with enough surface area that the van der Waals forces are able to resist gravity. The Linköping researchers decided to look into this more deeply and found that van der Waals forces do not hold indefinitely. Both the surface and the object suffer very small vibrations from molecules moving, and for the most part these are insignificant. Eventually though, these movements will fall in sync between the object and surface, which will cause them to detach from each other.
As the researchers point out, this is not a problem for geckos and other living, moving objects, but would mean you would not want to hang up anything relying on van der Waals for too long.
Source: Linköping University