Microscopic Fibers Coil Together

What at first resembles a sea anemone clasping two pearls is really a micrometer-scale construct created through a new technique devised at Harvard University.

To make these objects, materials science professor Joanna Aizenberg, applied math professor L. Mahadevan, and colleagues fabricate an array of hairlike, epoxy fibers poking up from a substrate, which they then submerge in a liquid such as ethanol or toluene. As the liquid evaporates, capillary forces cause the flexible hairs to clump and then twist together (Science 2009, 323, 237). The ropelike structures formed can themselves twine with other ropes. "The process is similar to the formation of dreadlocks" from wet, curly hair, Aizenberg explains.

If the liquid contains suspended particles, the entwining hairs capture them in a tenacious grip that can be loosened by, say, a change in pH.

"The structures self-assemble under the influence of simple physical interactions which can be understood and controlled," says Peter Fratzl, who investigates biomimetic materials at the Max Planck Institute of Colloids & Interfaces, in Potsdam, Germany. "This opens the possibility to create nanosystems with completely new functions." Potential applications include adhesives, switchable photonic devices, or drug delivery systems.