Gecko glue is one of those things that seems to be under constant development, as our flashbacks below testify. The National Science Foundation is now reporting that a group of scientists under Dr. Liming Dai from the University of Dayton has successfully developed “a gecko-inspired adhesive that is ten times stronger than a gecko, at about 100 newtons per square centimeter.” Such an adhesive might have implications for a variety of biomedical applications.
From the NSF:
The researchers constructed their adhesive out of two slightly different layers of multi-walled carbon nanotubes. The lower layer is composed of vertically-aligned carbon nanotubes, while the upper segment–which comes into contact with the surface it is sticking to–is curly, like a mess of spaghetti.
As shown in the figure, the adhesive sticks best when it is pulled down parallel to the surface it is sticking to–this is called shear adhesion. This action arranges the tips of the curly nanotubes so they have maximum contact with the substrate, thereby maximizing the Van der Waals force. Pulling the adhesive off in a motion perpendicular to the substrate is much easier–at this angle the sticking force is ten times weaker.
In this way, the adhesive has strong shear adhesion for firm attachment and relatively weak adhesion for detachment perpendicularly to the substrate. Just like a gecko, the adhesive can stick to a wall when needed, and then lift off easily to take the next step. This breakthrough, supported by the National Science Foundation, will have many technological applications.
Abstract: Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off Science 10 October 2008:
Vol. 322. no. 5899, pp. 238 – 242; DOI: 10.1126/science.1159503
NSF: As Sticky as a Gecko … but Ten Times Stronger!…
Flashbacks: Gecko Glue ; Gecko Tech for In Vivo Bandages; Geckos – not just for insurance sales anymore; Geckos and Mussels Scrub Up for Surgery