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Web Date: July 23, 2013

Nanostructures That Heal Themselves

Materials Science: Tiny patterns imprinted on the surface of the polymer Nafion can recover from repeated damage
Department: Science & Technology
News Channels: Nano SCENE, Materials SCENE
Keywords: nanotechnology, self-healing material, shape-memory polymer, nanoimprinting, Nafion, biomimicry
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POLYMER REVIVAL
Scanning electron micrographs show 5-µm-wide pillars molded into Nafion (left). In the center image, researchers deformed the pillars by rubbing the polymer surface with a finger. At the bottom, the pillars have returned to their original shape after heating. Scale bars are 10 µm for the closeups and 50 µm for the wide views.
Credit: Langmuir
20130723lnj1-nafion1
 
POLYMER REVIVAL
Scanning electron micrographs show 5-µm-wide pillars molded into Nafion (left). In the center image, researchers deformed the pillars by rubbing the polymer surface with a finger. At the bottom, the pillars have returned to their original shape after heating. Scale bars are 10 µm for the closeups and 50 µm for the wide views.
Credit: Langmuir

The iridescence of a butterfly’s wing and the stickiness of a gecko’s foot derive their properties from nanoscale structures on their surfaces. Unlike with those natural materials, nanostructures engineered from synthetic materials often lack the ability to heal themselves when damaged. Now a Singaporean team has imprinted nanopatterns into a shape-memory polymer and found that the patterns can repeatedly recover from damage (Langmuir 2013, DOI: 10.1021/la401621j).

Hong Yee Low, a polymer chemist at the Singapore University of Technology & Design, and her team molded a nanopattern into Nafion, a well-studied fluoropolymer-copolymer. They heated Nafion film at 310 °C for 10 minutes and used a mold to imprint rows of pillars, ranging from 500 nm to 5 μm wide, onto the material. After cooling the polymer to room temperature, the researchers bent the pillars by smudging them with a finger, blasting them with a focused electron beam, or squishing them with a diamond stylus. When the team heated the material to 140 °C, past Nafion’s glass transition temperature, the ruined structures regained their original shape. The structures withstood this damage-and-repair process 25 times.

Towards a possible application, Low is now working to mimic the complex nanopatterns on gecko feet with a polyurethane-based polymer that can heal itself. The materials could lead to a new type of dry adhesive.

 
Chemical & Engineering News
ISSN 0009-2347
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