Blogs / 80beats

Researchers have long known how to create surfaces that repel water (they just had to look at a duck’s back for an example), but how to repel oily liquids was a mystery until last year, when a team of MIT chemists created a material antisocial enough to repel liquids of both kinds. They have gone one better than nature, which is not known to have made materials with such properties. [Researchers] even had to coin a new word to describe their creation - “omniphobic” - literally meaning it hates everything [New Scientist].

Now, the same researchers have pushed the technology another step forward, by developing a set of general design rules for omniphobic materials and by altering existing items–like, for example, duck feathers–to make them repel both oil and water.

One of the biggest differences between water and an oily liquid such as octane, a component of petroleum, is surface tension. A droplet of a fluid with high surface tension — such as water — tends to pull itself into a sphere, whereas one with low surface tension, such as oil, tends to spread across a surface more readily [Science News]. Researchers first created a surface covered in 300-nanometer-tall “toadstools,” which allowed even oily liquids with low surface tension to remain in tight spherical droplets, essentially sitting on the toadstools’ caps.

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Researchers have built a honeycomb-like scaffold that resembles natural heart tissue, and found that when they seeded the artificial structure with heart cells from young rats the cells grew and joined together in an approximation of normal heart muscle. The cells had also formed electrical connections with one another, allowing them to contract in coordination – and when an electric field was applied along the long axis of the honeycomb, the cells indeed contracted. “You could see the cells ‘beating’ on the scaffold,” says [study coauthor] George Engelmayr [New Scientist].

Other researchers have constructed biodegradable scaffolding on which to grow different types of tissue, but heart tissue poses particular technical challenges. Heart tissue must be flexible enough to change shape as the heart contracts, but also strong enough to withstand the intense forces generated by these contractions. So, the researchers used a polymer…. “It’s elastic like a rubber band,” Engelmayr says, so it can withstand repeated stretching while only gradually losing strength as it degrades [Technology Review].

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A thin nanotech paper that’s being developed in a Florida lab could revolutionize everything from aviation to laptop computers, researchers say. The super-strong “buckypaper” could be layered like papier-mâché to build lighter airplanes and cars, or it could be exposed to an electric charge and used to illuminate computer and television screens–and those are just the most obvious applications, researchers say.

Buckypaper is 10 times lighter but potentially 500 times stronger than steel when sheets of it are stacked and pressed together to form a composite. Unlike conventional composite materials, though, it conducts electricity like copper or silicon and disperses heat like steel or brass. “All those things are what a lot of people in nanotechnology have been working toward as sort of Holy Grails,” said [nanotech expert] Wade Adams [AP].

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Would-be superheros have a cause for celebration, as the ability to walk up walls just got a little closer. Researchers have developed a nanotech superglue modeled on the minute structures on gecko feet that allow the lizards to scamper up sheer surfaces. They say the new glue is three times stronger than previous gecko-inspired glues, and ten times stickier than the lizards themselves.

The gecko owes its gravity-defying capacity to tiny structures that make use of the atomic-scale attractive van der Waals force. Look close enough at a gecko foot and you will see an ordered, forest-like structure — roughly half a million fine hairs that each sprout into hundreds of even thinner, spatula-shaped tips. When these tips come into close contact with a surface they induce strong van der Waals forces that keep the foot anchored — that is, until the gecko decides to peel it off [Physics World].

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A new plastic skin that could protect satellites from both searing and freezing temperatures in space could allow for a new generation of miniature spacecraft, researchers announced yesterday. Satellite designers had hit a wall in the quest to create tiny “micro-spacecraft” that weigh no more than 50 pounds because the temperature controls used on conventional satellites can’t be scaled down.

Lead researcher Prasanna Chandrasekhar says the development could allow small companies to send up individual satellites that better suit their needs rather than sharing space on one large one. As might be expected, the technology also has some other potential uses: “For the military, undetectability is also important, either for surveillance applications or when it comes to zapping other satellites,” Chandrasekhar added. “And when it comes to a [nano-spacecraft] less than 5 kilograms (10 pounds), you can’t really detect it unless it’s within a quarter of a mile of you. Larger spacecraft can be detected from farther, and consequently blasted out of the sky” [SPACE.com]. Chandrasekhar’s company, Ashwin-Ushas Corporation, is developing the technology in partnership with NASA.

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Researchers at the University of California, Berkeley, announced yesterday that they were able to construct a prism that bent light “the wrong way” and so would make an object appear to vanish [Times UK]. Details of the two different experiments will be published separately later this week in Nature and Science.

To bend the light, the scientists used “metamaterials,” mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite [AP]. One group built what they called a metal “fishnet” of alternating silver and magnesium fluoride; the other used tiny silver nanowires. Both created negative refraction: Light is neither absorbed nor reflected by the objects, passing “like water flowing around a rock,” according to the researchers. As a result, only the light from behind the objects can be seen [BBC].

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Researchers have used nets of carbon nanotubes to print electronic circuits on to thin, flexible sheets of plastic, in yet another example of nanotechnology’s expanding possibilities. The work is a major step towards the development of ‘plastic electronics’, where circuits on light, flexible surfaces could provide a range of products from paper-thin displays to intelligent food packaging and smart clothing [Chemistry World].

Everyone from entrepreneurs to the military is dreaming up applications for flexible electronics: They could be used to make a single-page electronic newspaper, for example, or could be formed into an electronic “skin” that covers an entire airplane, and checks the plane’s surface for cracks. Since the typical silicon-based circuits are too rigid to use in such devices, researchers have been trying out new materials. The other major contender is semiconductors that use organic molecules, but those have been shown to have poor performance and reliability.

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A mesh made of tiny metal nanowires could clean up oil spills in the ocean, according to a new report [Nature Nanotechnology, subscription required]. The “nanosponge,” which looks like a thin piece of brown paper, can sit on top of water without ever getting wet, while absorbing 20 times its weight in oil.

The MIT nanotech researchers haven’t tested their invention outside the lab yet, but say the nanosponge could be more effective than materials that are currently used to sop up oil, which often absorb water as well as the targeted oil, and which can’t be reused.

The nanowires, which are each 20 nanometers in diameter, are made of potassium manganese oxide and clump together naturally in dense tangles. The researchers then coated the material with a water-repelling silicone layer.

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