— One of the participating tokay geckos. Photo: Ethan Knapp and Alyssa Stark

I love a good gecko story, and I love how the cute little critters can climb up most things but would apparently struggle with my non-stick frying pan. Now I’ve found out that if my frying pan was still wet from the washing up Mr Gecko would have a better chance of holding on.

There is a serious side to this science. Hundreds of systems have been developed mimicking the adhesive power of gecko toes and all rely on creating a large surface area that can get in contact with whatever surface you want to stick to using van de Waals forces to do the rest. Understanding how different surfaces affect adhesion is obviously important and it’s been anecdotally known for a while that as well as struggling with Teflon, geckos can’t stick to wet glass despite their feet being superhydrophobic. In rainforests, things can get quite wet so how do the geckos manage?

To test this out Alyssa Stark‘s lab at the University of Akron, Ohio, placed geckos on different surfaces to investigate when the geckos slipped and when they stuck. To get more data than slip versus stick, those little geckos were fitted with harnesses and slowly pulled off surfaces using force meters to record the gecko adhesion values. If ever there’s a day you’d have liked to have been in someone’s lab, the day harnessed geckos were slid around for science has got to be up there (at least for me).

The findings are, in part, to be expected. Wetting surfaces usually makes them more slippery for geckos but it’s only wet glass that causes a real problem – hydrophobic surfaces that were wetted could still be clung on to as the lizard’s hydrophobic feet helped get rid of the water and form a contact with the dry surface beneath. So the lab work confirms that wet leaves shouldn’t be a problem. The exception, which also contradicted the Akron group’s modelling, was PTFE, or Teflon. Wet Teflon, it seems, is much easier for the geckos to hold on to. The why is not certain yet though, so I for one am looking forward to more gecko science, ideally with videos…

Laura Howes

                  

Source:
http://prospect.rsc.org/blogs/cw/2013/04/02/how-geckos-can-beat-non-stick/