Gecko and a snail are disputing who is better at climbing.
Gecko: I can walk on the wall.
Snail: Me too.
Gecko: I can walk on the ceiling.
Snail: Me too.
Gecko: I can walk on the glass wall.
Snail: Me too. Moreover I can crawl over razor blades.
Gecko: OK. Show it. You will cut yourself and I will be the only climber. Ha ha.
Snail: It was easy.
Gecko: Wow! Very impressive! But we are not talking about razor blades. Hey snail, you are good, but I am faster. You have to admit that I AM the best climber and I can climb everywhere.
Snail: No, you are not. I have seen your video on YouTube.
Gecko: Which one?
Snail: THIS one. You failed. And this one:
Gecko: That is an only exception. It is polytetrafluoroethylene, commonly known as teflon. It is the only material that geckos can not crawl. But at least I tried that.
Snail: I can crawl it.
Gecko: Ha-ha-ha-ha-haaaaaaaaaaa!!! Don’t you know that? Nobody can crawl on teflon. It has non-stick surface so nobody can stick to it. Teflon has very low surface tension. Teflon consist of atoms of carbon and atoms of fluorine. Electrons of fluorine are very tightly bounded. Therefore there are very weak van der Waals forces. Unfortunately these forces allows me to crawl on any material except of teflon.
Snail: I can really crawl it.
Gecko: If you think so. Try to crawl on this frying pan that has a teflon non-stick coating, But be careful. Some people say that teflon is not safe.
Snail: Do not worry. It is hazardous only in temperatures above 200 °C.
Gecko: OK. You won. But tell me, how do you do that?
Snail: First of all, I attach the whole foot to the surface all the time. Second, I create mucous layer that allows me to adhere to nearly any material. This is called adhesive locomotion. It cost me much energy, much water resources and it is slow, but it is one of the most effective method among all animals.
Gecko: Nearly. You said “nearly”! Finally!!! There exist something that you can not climb to. What is it?
Snail: Ummm… Well… Yes. There exist some snail resistant materials. For example I can not climb to radomes when they are painted with a superhydrophobic paint Hirec 1440. It is because radomes are weatherproof and they protects antennas from freezing rain.
Shirtcliffe N. J., McHale G. & Newton M. I. 2012: Wet Adhesion and Adhesive Locomotion of Snails on Anti-Adhesive Non-Wetting Surfaces. PLoS ONE 7(5): e36983. doi:10.1371/journal.pone.0036983
Wikipedia contributors. Teflon. – Wikipedia. accessed 25 May 2013