Hairy Adhesives

Ant writes "Science Daily has an article about scientists having found that the way spiders stick to ceilings could be the key to making Post-it notes that don't fall off even when they are wet. A team from Germany and Switzerland have made the first detailed examinations of a jumping spider's 'foot' and have discovered that a molecular force sticks the spider to almost anything. The force is so strong that these spiders could carry over 170 times their own body weight while standing on the ceiling. The research is published today (Monday 19 April 2004) in the Institute of Physics journal Smart Materials and Structures." Other researchers are actually exploring ways to make a sort of non-glue adhesive tape.

Re:One thing that's never been clear

[bigg_nate]

From the article:

The total van der Waals force on the spider's feet is very strong, but it is the sum of many very small forces on each molecule. The researchers believe the spider lifts its leg so that the setules are lifted successively, not all at once, and it does not need to be very strong to do this. All you would have to do to lift a future kind of Post-it® note is peel it off slowly.

We've known gecko feet work like this for years

[infernow]

I don't think this is as much of a breakthrough as the article makes it out to be. We've known that geckos use Van der Waals forces to climb things for years.

Here's an article from nature.com [nature.com] from 2000 that talks about gecko feet, and here's another [nature.com] from 2002 about how scientists have developed prototype adhesives based on what they learned from geckos. One of the articles even talks about experiments from 30 years ago, wherein researchers found that geckos do not stick to Teflon, which does not produce Van der Waals forces.

So while we may not have known that spiders use Van der Waals forces as well, we have known for years that animals have been using the force to stick to things.

Obstacle

[Dachannien]

One of the biggest problems in developing a gecko- or spider-inspired adhesive is that the hairs on the feet of the gecko (and likely the spider as well) have lots of regular branching that are very difficult to fabricate non-biologically. The branching structure increases the surface area of the keratin by some very large factor, which increases the adhesion of the material.

This means that, before this stuff can be produced as an ultra-strong adhesive, we will need to understand - and replicate/emulate - the biological process by which the hairs are produced.

Better Post-it Notes

[rpiquepa]

You'll find extra references and pictures on my blog [weblogs.com].