Polymer Could Spot Brain Injuries | Chemical & Engineering News
Volume 93 Issue 33 | p. 29 | Concentrates
Issue Date: August 24, 2015

Polymer Could Spot Brain Injuries

ACS Meeting News: Photonic crystal made from plastic changes color when compressed
Department: Science & Technology
News Channels: Analytical SCENE, Environmental SCENE, Materials SCENE, Nano SCENE
Keywords: traumatic brain injury, photonic crystals, structural color, ACS meeting news, #ACSBoston

To help doctors determine whether a patient might have experienced a traumatic brain injury, materials scientists have developed a thin polymeric film that changes color when struck with forces similar to those produced during football games or combat. The sensor is basically litmus paper for forces, said Shu Yang of the University of Pennsylvania. Yang and her team designed the sensor as a photonic crystal—a material with ordered nanostructures that interact with light to produce color. They built it by dipping a silicon wafer in a suspension of silica nanoparticles. The particles self-assembled into an ordered crystal on the wafer. The team then added a thermoplastic, allowing the polymer to fill in around the particles and solidify. After dissolving away the silica with acid, the researchers were left with an ordered array of voids where the particles once were. This material starts out orange-red. An applied force compresses these voids, shrinking their widths and shifting the color of the overall material, first to green and then to purple and blue.

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These photonic crystals changed color when a 300-µm-diameter tip pressed the materials with 30-mN (left), 60-mN (middle), and 90-mN (right) forces.
Credit: Yang Lab
Photonic crystal made from a polymer changes color with different levels of forces.
 
These photonic crystals changed color when a 300-µm-diameter tip pressed the materials with 30-mN (left), 60-mN (middle), and 90-mN (right) forces.
Credit: Yang Lab
 
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ISSN 0009-2347
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