Science Forums 2

[InfiniteNow]

Originally Posted by freeztar

Perhaps I'm taking "pushed" too literally, but wouldn't gecko tape need to be pushed onto a surface as well? And would not the nanotubes interacting with the surface be considered molecular?

I'm going to hazard a guess and say that in a vacuum, you do not have space between the molecules because of lack of air. Perhaps this air space is critical for the "intertwining" to work.
I'm envisioning something like a peice of velcro made out of minature balloons. With the baloons deflated, no "hooks" would exist to snag each other.

It appears you're pretty close.

Straight Dope Staff Report: How does glue work?

A good adhesive has excellent properties of adhesion (the ability to stick to the surfaces to which it's applied) and cohesion (the ability to stick to itself). When you pull apart something that's been glued together and the glue comes right off the pieces, that's an adhesive failure. If the glue itself splits apart, leaving glue on either side of the joint, then that's a cohesive failure:

There's no universally accepted theory, and given the variety of adhesives more than one process may be at work. It's generally agreed that adhesion occurs at the molecular level, the chief processes involved being Van der Waals forces, ionic bonding, covalent bonding, and metallic bonding.

According to recent research, Van der Waals forces explain how the lizards known as geckos can stick to so many surfaces in a seemingly impossible manner. Specifically, the tiny hairs on the gecko's feet (called setae) are split at the microscopic level into "as many as 1,000 branches, whose spatula-shaped tips are only 200 nanometers wide." As a result, even though the Van der Waals forces acting on an individual tip is small, the adhesion of a billion or so tips adds up to enough force to let the gecko stick to anything.

Persuasive as all this sounds, other scientists doubt that Van der Waals forces alone fully explain how glue works. They attribute at least some of the strength of adhesives to mechanical bonding, also known as mechanical locking. The idea here is that all surfaces, even seemingly smooth ones, are actually rough at the molecular level, and that an adhesive achieves some of its strength by flowing into the hidden valleys and imperfections of the surfaces to be bonded...In mechanical bonding as with Van der Waals forces, an adhesive needs to be able to spread finely into the microscopic roughness of the surfaces, wet the tiny cracks properly, and allow trapped air to escape. The main difference is that mechanical bonding will work at distances that would render Van der Waals forces useless.

Still another type of adhesion involves the presence of tiny air bubbles--in 1999, French researchers presented a theory in Discover magazine that instant adhesives (like that used in Scotch-brand tape and Post-It notes) actually work by creating numerous microscopic bubbles each having a partial vacuum in them, which act as suction cups.