Fearing and his colleagues are part of a Nanoscale Interdisciplinary Research Team supported by the National Science Foundation and specifically tasked in 2003 with developing synthetic adhesives that perform like gecko hairs.
In 2000, Fearing teamed up with biologists Robert Full at UC Berkeley and Autumn at Lewis & Clark, and engineer Thomas Kenny from Stanford University, in the first study pointing to the secret of gecko adhesion: intermolecular van der Waals forces that remain weak until surfaces get intimately close. Two years later, members of this same team synthesized gecko hair tips that stick, providing the first direct experimental verification of a van der Waals mechanism for gecko foot-hair adhesion.
Not only is each gecko toe covered by millions of tiny hairs, but those hairs are further split at the end into billions of nanoscale spatulae. The van der Waals forces come into play when these spatulae make contact with the surface.
This new material is also an example of a "smart adhesive," becoming stronger with use, said Fearing, who is also part of UC Berkeley's Center for Information Technology Research in the Interest of Society. "More microfibers bend and engage automatically as the weight increases. When the load is removed, the microfibers disengage. This allows for controlled attachment and detachment and is a critical innovation for clean release and reuse. It's the first time this has been demonstrated with a hard microfiber array."
Another benefit to using hard polymers is that the fibers are less prone than softer plastic to collecting dirt after repeated use.
So far, the new adhesive only works on smooth, clean surfaces. The next step, said Fearing, is to develop a material that can also adhere to rough surfaces and that is self-cleaning.
|Contact: Sarah Yang|
University of California - Berkeley