Strain-induced color changes in biomimetic materials | Chemical & Engineering News
Volume 94 Issue 29 | p. 9 | Concentrates
Issue Date: July 18, 2016

Strain-induced color changes in biomimetic materials

Microscopic cracks and folds reversibly alter appearance of polymer-based hybrids
Department: Science & Technology
News Channels: Materials SCENE
Keywords: materials, color change material, mechanochromic, fluorescence
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The color of the fluorescence emitted by this mechanochromic material changes reversibly as it is stretched by several millimeters and released (right) because of the formation of micrometer-sized cracks and folds (left).
Credit: Luyi Sun/U Connecticut
Images of material changing colors as it is stretched and released.
 
The color of the fluorescence emitted by this mechanochromic material changes reversibly as it is stretched by several millimeters and released (right) because of the formation of micrometer-sized cracks and folds (left).
Credit: Luyi Sun/U Connecticut

Taking a clue from jellyfish and squids that quickly alter their appearance via muscle-controlled morphology changes in their bodies’ surface structures, researchers have designed polymeric materials that change appearance reversibly in response to mechanically induced folds and deformations (Nat. Commun. 2016, DOI: 10.1038/ncomms11802). The animals exploit their color-changing abilities for camouflage and safety purposes. Scientists could use the new synthetic materials for those applications or as mechanical sensors, optical switches, and color-changing smart windows. The researchers, led by Luyi Sun of the University of Connecticut, made several types of so-called mechanochromic materials by depositing a transparent rigid film made from polyvinyl alcohol and a silicate compound on a flexible polydimethylsiloxane (PDMS) substrate. Stretching the simple bilayer material by 40% changes its appearance markedly yet reversibly from transparent to opaque. The optical changes result from stretch-induced microscopic cracks and folds that trap and scatter light. The team varied the material design to induce other optical effects. For example, they bonded an ultraviolet-shielding film to PDMS doped with a variety of fluorophores. Stretches and strains as small as 5% caused these materials to quickly change colors or change from nonluminescent to highly luminescent.

Colorful

Stretching this polymeric hybrid material by several millimeters and releasing it induces a range of reversible color changes. Credit: Luyi Sun/U Connecticut

 
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Comments
Miguel Mitchell (Wed Jul 20 17:52:31 EDT 2016)
Amazing! I hope that this can be done as an undegraduate experiment. It would be very memorable and inspire students to learn more about chemistry.

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