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Materials

Opening and closing nano-venetian blinds

Stretching pliable polymer composites containing brittle components could open new portals in nanotech

by Matt Davenport
June 13, 2016 | A version of this story appeared in Volume 94, Issue 24

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Credit: Nature
A glass filament, about 20 µm in diameter and shown as a black line, reversibly splits into uniform pieces when its polymer coating is stretched.
A micrograph shows a thin glass rod that has been broken into discrete particles within its polymer cladding.
Credit: Nature
A glass filament, about 20 µm in diameter and shown as a black line, reversibly splits into uniform pieces when its polymer coating is stretched.

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.

Watch how polymers and brittle materials join forces to create micro- and nanoparticles in this video. For reference, each polymer component shown is about 1 mm across.
Credit: Nature/C&EN

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