Iridescence and superhydrophobicity combined on one surface

January 21, 2012 by Lisa Zyga weblog
graphene oxide
Biomimetic graphene oxide with iridescence like a butterfly's wing and superhydrophobicity like a rose petal. Image credit: Wang, et al. ©2012 Chemistry - An Asian Journal

(PhysOrg.com) -- Scientists have combined two properties on a single piece of graphene oxide that don’t usually go together: iridescence (resulting in a rainbow-hued appearance) and superhydrophobicity (causing low-contact water droplets to strongly adhere to the surface). The engineered surface could have applications in liquid transportation and analysis, and due to graphene’s good electronic properties, possibly even in future electronic devices.

The researchers, Jian-Nan Wang and coauthors from Jilin University in Changchun, China, achieved these properties by creating a microscopic texture on the graphene oxide’s surface. By shining two laser beams on the surface, they created an interference pattern that burned tiny grooves into the material. The surface immediately took on an iridescent appearance, shimmering like a butterfly’s wing. The scientists explained that the tiny grooves, which form highly ordered periodic structures, act as diffraction gratings that split white light into its various colored wavelengths.

The researchers discovered that the surface effects also caused the graphene oxide to exhibit highly adhesive superhydrophobicity. When they poured water on the surface, the water merged into nearly spherical droplets. Although the droplets are barely in contact with the graphene oxide, they adhere to the surface, not detaching even when the surface is held upside down. The researchers attributed this phenomenon to the surface’s microscopic unevenness and a decrease in surface energy caused during laser irradiation, which removes some hydrophilic oxygen groups.

The researchers predict that the combination of these two properties on one surface could have applications in microfluidic devices, where a superhydrophobic surface is useful for transporting small amounts of liquid in a controlled way. oxide might also be used as a biocompatible surface for growing cells, which requires controlled wetting.

The might be used for color-coding different states in microfluidic devices, as well as decorating for aesthetic purposes. Also, by altering the optical properties of graphene-based devices, it may open doors to new optical or electronic devices.

Explore further: Light-speed nanotech: Controlling the nature of graphene

More information: Jian-Nan Wang, et al. “Biomimetic Graphene Surfaces with Superhydrophobicity and Iridescence.” Chemistry - An Asian Journal. DOI: 10.1002/asia.201100882
via: Chemistry World

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Husky
not rated yet Jan 20, 2012
superhydrooptophobomicroiridofluidotransistors i try in wordfeud...
Argiod
2 / 5 (4) Jan 20, 2012
I'd like to see this added to automotive paint to create a vehicle that sheds water instead of rusting away. I can also see a windshield coating that would afford privacy while shedding water, ice and possibly mud thrown up by passing vehicles.
Ronan
not rated yet Jan 20, 2012
I'm rather more interested by the "adhesive yet hydrophobic" qualities of this substance than its iridescence, frankly. They note that hydrophilic oxygen groups are removed (and, presumably, other polar groups are also absent), yet the water droplets still somehow adhere? Van der Waals attraction, maybe?
Jaeherys
5 / 5 (3) Jan 20, 2012
After doing a bit of reading, it would seem that van der waals forces may me the culprit for adhesion. Gecko pads are adhesive and hydrophobic and an aluminum oxide type material with a pillar type surface (created by researchers studying the gecko pads) showed the same properties. So it's probably not a big stretch to infer the same type of mechanic is involved on this graphenes surface.

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