Why do the feet of the Gecko Lizard not stick to Teflon surfaces?
Gecko feet have been the focus of a lot of research over the past 10 years.  

Their ability to walk up vertical or even hanging from ceilings is attributed to tiny branching hairs growing from the pads of their feet.  The hairs branch down to the size of 100s of nanometers and its believed that this gives them large surfaces at the molecular scale, giving them a strong van der Waals adhesion force.  



Teflon, being hydrocarbon chains covered with 'hard' electronegative flourine atoms doesn't provide the same attraction to the hairs, as van der Waals forces rely on mutual polarizability of atoms in close contact. That is to say, electronically fluffy atoms can stick together more readily.