Thomas R. O'Donnell

Materials roundup: disappearing antennae, metal molding, tiny cubes and pond scum

In University research on May 13, 2014 at 6:43 am

 

As I was messing around with arctic research, zombie tractors and NGSS – and doing my taxes – there was a burst of materials science news out of Iowa State University and its on-campus Department of Energy facility, the Ames Laboratory.

It’s all about putting stuff together in new ways for new purposes – whether it’s electronics that (maybe) melt in your mouth, a machine that spits out metal objects, minuscule building blocks that line up just right, or tiny, powerful catalysts to create diesel from relatives of common pond scum. (That last bit isn’t a reference to your Uncle Purvis, the one who lives in that crappy mobile home.)

Almost all the work is fundamental, but some projects are easier to grasp and have more immediate applications than others.

The guy getting attention for the vanishing electronics is Reza Montazami, an assistant professor of mechanical engineering. The idea is to create what he calls “transient” devices – ones that melt, either after a set time or in response to a signal. Transient devices have obvious uses for medicine, as implantable devices the body would merely absorb after the devices serve their purpose; for security, with gadgets that could self-destruct lest they fall into the wrong hands; and even for consumer use, like a credit card that could degrade if lost or stolen.

All that’s a long way off, although Montazami says he’s made a degradable antenna capable of transmitting data. A recent paper in the journal Advanced Functional Materials details some of the work, particularly efforts to control the rate at which the transient stuff degrades. Above is a nifty video of an LED winking out and dissolving in water. KCCI-TV of Des Moines also did a report.

What’s interesting to me about Montazami’s transient materials is that a typical kitchen has some of the ingredients: sucrose – common sugar – and gelatin. Looking at just the abstract (not as good as reading the full paper, I know), it appears he and his colleagues add these to a matrix made with polyvinyl alcohol, a nontoxic, water-soluble polymer. Could the material even be edible?

The abstract indicates Montazami and his colleagues can extend or shorten the lifespan of the transient materials by adjusting the proportions of ingredients.

Other ISU researchers involved are mechanical engineering professor Nastaran Hashemi; postdoctoral researchers Handan Acar and Simge Cinar; and Mahendra Thunga, a postdoc in materials science and engineering and an Ames Laboratory associate. (FULL DISCLOSURE: I used to carpool with this guy.)

Meanwhile, the Ames Laboratory got a new three-dimensional printer this winter. That doesn’t sound like a big deal, since hobbyists everywhere have taken up 3-D printing and the machines are on the verge of becoming household appliances.

But most of those print in plastic, laying down layer after layer to translate a computer model into a tangible object. Ames Lab’s machine prints in metal, using lasers to melt metal powders and deposit the hot material, bit by bit, on a substrate. Metal printers are more complex and expensive than standard 3-D printers. At this point, they’re mostly custom-producing components rather than mass-producing them.

For Ames Lab, it’s less what the machines produce than what goes into them. The device is part of the lab’s Critical Materials Institute, which aims to find new materials that rely less on rare-earth elements from foreign sources.

Institute scientists will use the printer to try out new materials, like untested alloys. Materials often behave differently when they’re in small amounts, like thin films, than they do in bulk quantities. The printer will let the researchers build chunks of alloys for testing.

 

The 3-D printer fits with Ames Lab’s historic approach of putting elements together to see what kinds of new, hopefully useful, properties the compounds have. It used to be educated guesswork, but now computational chemists use powerful new machines and more precise and efficient algorithms to predict a material’s properties before it’s made. That lets experimentalists narrow their search to the combinations most likely to yield the desired qualities.

The third interesting bit of materials news shows how computer models provide insights and suggest new avenues for experiments. It may be the most difficult to grasp, but it could lead to new substances with desirable qualities, like strength or conductivity.

In essence, Ames Lab researcher Alex Travesset and graduate assistant Chris Knorowski have calculated a way to make nanocubes line up. Nanocubes are blocks of material billionths of a meter in size. Nanoscale materials are hot commodities these days, with more familiar objects like nanoparticles and nanotubes starting to make their way into electronics and consumer products.

Nanocubes are desirable for some applications because they stack more tightly than nanoparticles. Think of the difference between a jar of marbles and a pallet of boxes.

But unlike nanoparticles, the tiny cubes are particular about how they line up. They’ll fit together only if their sides are oriented to adjoining blocks in certain ways. It’s a bit like trying to stack magnetic cubes: because of their polarity, each must sit a particular way for them to form a solid block. That anisotropic behavior can frustrate efforts to get the cubes organized into a regularly repeating structure that may be key to working with them nanocubes or getting desired properties, like light reflectivity.

"Hairy" polymer-coated nanocubes and DNA-coated nanocubes get in line. Image from the Ames Laboratory website.

“Hairy” polymer-coated nanocubes and DNA-coated nanocubes get in line. Image from the Ames Laboratory website.

Knorowski (who’s actually lead author on a paper about the research, published in the Journal of the American Chemical Society) and Travesset used a theoretical model to see what would happen if the cubes were coated. In one case, they calculated the effects of a polymer coating, creating so-called “hairy” cubes. In another scenario, they reckoned what would happen if the cubes were coated with single-stranded DNA and paired with cubes coated with complementary DNA.

DNA, as most high school biology students know, is comprised of bases (coded as C, T, A, and G for the chemicals comprising them) that will pair only with complementary bases. So it’s possible to put single strands of DNA on cubes that are “programmed” to match up with complementary strands placed on other cubes, like jigsaw puzzle pieces.

The Ames Lab duo’s model showed both kinds of coated cubes self-assembled into regular structures, but the DNA coating allowed for a greater degree of control. As Travesset says in the lab’s release, “With DNA, you can encode information about which cubes are going to assemble with which other cubes. It gives you a more precise way to target relevant self-assembled structures.”

The study, in essence, shows this is possible, given physical and chemical properties. Now it’s the experimentalists’ job to test it in the real world.

Finally, in (relatively) late-breaking nano-news (I sound like Mork from Ork), an Ames Lab release issued this week is touting its development of specialized particles as catalysts for a cleaner biofuel.

I’m tempted to call it biodiesel, but the release makes a point of  calling it “green diesel,” which the Ames Lab researchers say has a composition closer to that of petroleum diesel. It’s also said to be more stable and denser in energy than biodiesel.

It starts with algae, a promising biofuel feedstock currently under study. One idea is to use waste carbon dioxide from power plants to boost the growth of oil-containing algae, which are related to the tiny green plants found on common farm ponds, under controlled environments. But it takes two steps and expensive catalysts like platinum to process algae oil into biofuel.

The Ames Lab group created structured porous nanoparticles containing a chemical that captures fatty acids in the algae oil. The particles also contained even smaller  nanoparticles that catalyze the acids’ conversion into green diesel. In essence, the dual-function tiny beads do both steps at once.

The kicker is in the catalyst: The group first used nickel, a plentiful and cheap element, to convert the fatty acids. But they also tried iron, which is even less expensive and more common, and found it worked even better than nickel.

The research, led by Ames Lab scientist Igor Slowing, is published in the May issue of the Journal of Catalysis.

Uncle Purvis will be proud.

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