One of the challenges in making a robot stick to walls lies in finding a way to apply sufficient pressure to make them stick. The new CMU robot handles this using a tail. At any one moment, at least two of its six foot pads are in contact with the surface, as is the tail, which is spring-loaded so that it will always push against the surface, even when on the ceiling.

However, in developing these materials, the researchers still need to resolve some issues, says Andre Geim, a professor of condensed-matter physics at the University of Manchester, in the United Kingdom, who has also fabricated setaelike structures. "No one has yet explained why geckos can first run on a dirt road picking up dust and then somehow climb up walls," he says. "This is a major obstacle."

Cutkosky agrees that more research needs to be done into the self-cleaning abilities of geckos. "The world is dirty, and robots cannot be stopping to wash their feet every few meters," he says.