Featured Research

from universities, journals, and other organizations

Forever clean? Metal–organic 'micromushrooms' repel all

Date:
April 10, 2014
Source:
The Agency for Science, Technology and Research (A*STAR)
Summary:
A clever chemical transformation yields surface-bound microstructures that efficiently drive away oil- and water-based contaminants. Natural surfaces that repel water, such as lotus leaves or butterfly wings, often have a rough, microscale texture that traps air beneath the liquid droplet. By mimicking these biological structures, researchers have developed 'superhydrophobic' coatings that are highly resistant to wetting. One trick unknown to nature, however, is the ability to repel hydrocarbon-based oils that have much lower surface tension than water and tend to spread out rather than bead up.

A clever chemical transformation yields surface-bound microstructures that efficiently drive away oil- and water-based contaminants.

Natural surfaces that repel water, such as lotus leaves or butterfly wings, often have a rough, microscale texture that traps air beneath the liquid droplet. By mimicking these biological structures, researchers have developed 'superhydrophobic' coatings that are highly resistant to wetting. One trick unknown to nature, however, is the ability to repel hydrocarbon-based oils that have much lower surface tension than water and tend to spread out rather than bead up.

Jia Min Chin and co-workers from the A*STAR Institute of Materials Research and Engineering and A*STAR Institute of Bioengineering and Nanotechnology in Singapore have now discovered a simple procedure to synthesize 'omniphobic' interfaces that repel both oil and water using intricate, mushroom-shaped, metal-organic crystal frameworks.

Recent efforts toward omniphobic surfaces have focused on producing reentrant microscale textures, which have curved shapes that inherently retain air pockets. These structures prevent oil from wetting the surface and stabilize the beaded droplet state. Currently, complicated and labor-intensive lithographic fabrication techniques are needed to generate such textures.

Chin and co-workers investigated a 'bottom-up' strategy to synthesize omniphobic films using metal-organic frameworks (MOFs) -- compounds that connect metal ions into multidimensional structures using hydrocarbon-based linkages. Previous studies have shown that an aluminum-containing MOF, known as NH2-MIL-53(Al), can controllably form micro- and nanoscale rods and needles. The team suspected that suitable synthetic conditions could yield spontaneous needle growth upward from a substrate, forming a micro-rough surface with numerous trapped air pockets.

To achieve this, the researchers mixed their MOF precursor with an aluminum oxide membrane and applied 'hydrothermal' high temperature-high pressure aqueous reaction conditions. This resulted in perpendicularly aligned needles on both sides of the membrane. Next, the team faced the challenge of transforming the needles into curved textures suitable for repelling oil. After many attempts, they spotted an important clue -- the modified membranes 'floated' on top of aqueous surfaces due to their superhydrophobic nature.

Chin and her team exploited this floating effect by suspending the microneedle-covered membrane in an aqueous solution of the MOF precursor. Additional MOF growth occurred only on the wetted tips of the needles, expanding the crystalline stems into mushroom-like caps (see image). By controlling the reaction time to generate a targeted cap size, the researchers' omniphobic surface successfully repelled long-chain hydrocarbon oils.

Chin notes that this benchtop, chemical process produces results previously limited to facilities with expensive, high-tech equipment. "Our aim was to develop simple techniques for fabricating interesting structures which are accessible to scientists around the world," she says.


Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.


Journal Reference:

  1. Tristan T. Y. Tan, Michael R. Reithofer, Eric Y. Chen, Ajay G. Menon, T. S. Andy Hor, Jianwei Xu, Jia Min Chin. Tuning Omniphobicity via Morphological Control of Metal–Organic Framework Functionalized Surfaces. Journal of the American Chemical Society, 2013; 135 (44): 16272 DOI: 10.1021/ja407896m

Cite This Page:

The Agency for Science, Technology and Research (A*STAR). "Forever clean? Metal–organic 'micromushrooms' repel all." ScienceDaily. ScienceDaily, 10 April 2014. <www.sciencedaily.com/releases/2014/04/140410160245.htm>.
The Agency for Science, Technology and Research (A*STAR). (2014, April 10). Forever clean? Metal–organic 'micromushrooms' repel all. ScienceDaily. Retrieved August 29, 2014 from www.sciencedaily.com/releases/2014/04/140410160245.htm
The Agency for Science, Technology and Research (A*STAR). "Forever clean? Metal–organic 'micromushrooms' repel all." ScienceDaily. www.sciencedaily.com/releases/2014/04/140410160245.htm (accessed August 29, 2014).

Share This




More Matter & Energy News

Friday, August 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Australian Airlines Relax Phone Ban Too

Australian Airlines Relax Phone Ban Too

Reuters - Business Video Online (Aug. 26, 2014) Qantas and Virgin say passengers can use their smartphones and tablets throughout flights after a regulator relaxed a ban on electronic devices during take-off and landing. As Hayley Platt reports the move comes as the two domestic rivals are expected to post annual net losses later this week. Video provided by Reuters
Powered by NewsLook.com
Hurricane Marie Brings Big Waves to California Coast

Hurricane Marie Brings Big Waves to California Coast

Reuters - US Online Video (Aug. 26, 2014) Huge waves generated by Hurricane Marie hit the Southern California coast. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Chinese Researchers Might Be Creating Supersonic Submarine

Chinese Researchers Might Be Creating Supersonic Submarine

Newsy (Aug. 26, 2014) Chinese researchers have expanded on Cold War-era tech and are closer to building a submarine that could reach the speed of sound. Video provided by Newsy
Powered by NewsLook.com
Breakingviews: India Coal Strained by Supreme Court Ruling

Breakingviews: India Coal Strained by Supreme Court Ruling

Reuters - Business Video Online (Aug. 26, 2014) An acute coal shortage is likely to be aggravated as India's supreme court declared government coal allocations illegal, says Breakingviews' Peter Thal Larsen. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins