Opening and closing nano-venetian blinds

Researchers led by Soroush Shabahang and Ayman F. Abouraddy at the University of Central Florida are making nanoparticles with their bare hands––and some crafty materials science. To create uniform micro- and nanoscale structures, the team is simply stretching fibers and sheets made from a ductile polymer composite containing either a brittle core or coating (Nature 2016, DOI: 10.1038/nature17980). The team’s process is compatible with a variety of ductile materials, such as polycarbonate and polyethersulfone, that can be stretched at room temperature without breaking. The method also works with a variety of brittle materials, including glass, gold, and even ice. Stretching a fiber or sheet of one of the composites with a pair of pliers forces the polymer’s molecules into alignment, which causes the fiber or sheet to contract. But this contraction begins in a small region and then spreads outward like a wave, traveling through the polymer layer. This wave acts like a pair of scissors to cut the brittle component of the material into pieces at regular intervals, Abouraddy says. The researchers can then dissolve the polymer to retrieve the uniform brittle pieces, or instead they can repair the composite by heating it. This reversible snip-and-repair method opens and closes gaps in the brittle component, similar to opening and closing slats in venetian blinds, a process that could be useful for nanostructured dynamic camouflage, Abouraddy says.