Geckos, being master of the van der Waals force, climb up glass walls like it's no big thing. But can they do it when they're dead? Scientists have found out that they can, and that has important implications for technology.
Geckos can climb pretty much anything, no matter how smooth the surface. Scientists at first thought that, with the tiny hairs on the gecko's hands, they were gripping imperceptible imperfections in the surfaces they climbed. Further investigation revealed that the geckos were using the van der Waals force.
The force involves disrupting the balance of electrons and protons in individual atoms. When an atom has all its electrons on one end, and it approaches another atom, the like charges repel. The electrons on the second atom will flee to the far end of the second atom. That leaves the protons on the near end of the second atom exposed, and unlike charges attract each other. The two atoms stick together. The tiny hairs on the gecko's hands are made of stuff that encourages the van der Waals force. To control its grip, the gecko controls how many hairs are in contact with the surface.
But do these gecko hairs work after the geckos were dead, or does it take conscious control? Since the tests were performed after the gecko's death and time was a factor in this experiment, it's safe to say that the geckos tested did not die of natural causes. That's the bad news. The good news is that scientists designed a system that could mimic the dragging motion of the gecko's hands, along with devices that would record the motion and measure the forces involved. According to Timothy Highan, one of the conductors of the experiment, "We found that dead geckos maintain the ability to adhere with the same force as living animals, eliminating the idea that strong adhesion requires active control. Death affects neither the motion nor the posture of clinging gecko feet. We found no difference in the adhesive force or the motion of clinging digits between our before- and after-death experiments."
Up until 30 minutes after death, there was no real change in stickiness. The force doesn't depend on conscious control at all. It does, however, depend on a gecko's ability to keep its own hand from getting damaged. Too much drag will damage the hairs, and, because the gecko is dead, they won't be reconstructed. So if we make adhesive or climbing technology based on this, we need to make sure there is a system that checks damage, and that replaces damaged parts.
Gecko Hand Image: Emily Kane
Via Biology Letters.