How geckos become unstuck
Geckos have an amazing ability to stick to surfaces—they can even run upside down on polished glass. About a decade ago, it was shown that gecko feet have microscopically structured hairs that exploit atomicscale attractions (van der Waals (vdW) forces).1,2 Later, the same principle was discovered in spiders.3,4 This short-range attraction is so strong that a tiny contact area is enough to support the creature’s weight.
Not only is this stickiness highly effective, but the surfaces are also self-cleaning. So they avoid the problem that ordinary sticky tape has of attracting dust and losing its effectiveness. So, scientists imitated the microscopic design of the sticky feet in a fine-structured sticky tape. The tape was both strong—a contact area of only 0.5 cm² on glass could bear a load of more than 100 grams—and self-cleaning.5,6 However, this tape could be attached and detached only a few times before the fine structure was destroyed.
However, for the gecko to run on surfaces, it must have a good way to become unstuck when needed. New research at Oregon State University has unlocked more gecko secrets to explain why.7 Unlike the imitation tape, the live gecko can change the angle of the hairs to detach. And the hairs are curved, so they store lots of energy like a spring, and use this energy to separate quickly.
Researcher Alex Greaney, a professor of mechanical engineering, said, “What’s amazing is just how finely balanced and finely tuned this whole system is.” One of the reports8 wrote, “with the future of gecko tech looking bright, perhaps it’s time to give some credit where credit is due.” It then quoted the discoverer of the vdW mechanism, Kellar Autumn, a biomechanics professor at Lewis and Clark College in Portland, Oregon:
“Adhesive nanostructures are such a different way of sticking things together that I don’t think engineers would have invented this if geckos hadn’t done it first.”
Indeed, we should give credit, but not to the geckos that had no control over their foot structure, but to the One who designed both them and their amazing feet, on Day 6 of Creation Week.
References and notes
- Autumn, K. et al., Adhesive force of a single gecko foot hair, Nature 405(6787):681–681,2000 | doi:10.1038/3501507; perspective by Gee, H., Gripping feat, same issue, p. 631. Return to text.
- Sarfati, J., Great gecko glue? Creation 23(1):54–55, 2000; creation.com/gecko. Return to text.
- Kesel, A.B., Martin, A. and Seidl, T., Adhesion measurements on the attachment devices of the jumping spider Evarcha arcuata, J. Exp. Biol. 206(16):2733–2738, 2003 | doi:10.1242/jeb.00478. Return to text.
- Sarfati, J., Spectacular spider stickiness, Creation 27(4):54–55, 2005; creation.com/spiderstick. Return to text.
- Geim, A.K. et al., Microfabricated adhesive mimicking gecko foot-hair, Nature Materials 2(7):461–463, 2003 | doi:10.1038/nmat917. Return to text.
- Sarfati, J., Gecko foot design—could it lead to a real ‘spiderman’? Creation 26(1):22–23, 2003; creation.com/geckoman. Return to text.
- Hu, C. and Greaney, P.A., Role of seta angle and flexibility in the gecko adhesion mechanism, Journal of Applied Physics 116:074302 | doi:10.1063/1.4892628, 12 August 2014. Return to text.
- Sirucek, S., How geckos turn their stickiness on and off, newswatch.nationalgeographic.com, 12 August 2014. Return to text.