Nanoclast iconNanoclast

DNA Data Storage Just Got a Bit More Practical

For two years now, researchers have been storing digital information in the form of DNA, but there has remained some question as to whether it’s a practical solution for digital storage.

Now researchers at the Swiss Federal Institute of Technology in Zurich (ETHZ) have addressed a number of the problems associated with using DNA as data storage—enough so that they believe it can be used for error-free storage of information.  If their solution proves successful, it could open the door for data storage that lasts for a million years.

Researchers around the world have been investigating a variety of new methods for storing digital information because we’ll be lucky if the solutions we have now, like hard drives and servers, can keep faithful records for fifty years. DNA has been among those potential alternatives. But errors during data retrieval have been the method’s bugaboo. Gaps and false information in the encoded data result from chemical degradation and mistakes in DNA sequencing.

In research published in the journal Angewandte Chemie, the Swiss team was able to overcome the problem of chemical degradation of the DNA by encapsulating the genetic material in silica (glass) spheres with diameters of around 150 nanometers.

In order to test the quality of their encapsulation, the researchers simulated a long period of time by storing the information-encoded DNA at temperatures between 60 and 70 degrees Celsius for up to a month. This simulated, within a few weeks, the degradation that would occur over hundreds of years under normal conditions.

After finding that the silica capsules outperformed several other materieals they tested, the researchers then moved on to ensuring that the DNA remained error free.

While advances in DNA sequencing make it possible to read stored data on DNA affordably, affordability and exactitude don’t always go hand in hand. To overcome this problem, the researchers have developed a way to correct any errors based on the Reed-Solomon Codes, error-correcting codes normally used to ensure accurate data recovery after long-distance data transmission.

The scheme adds just a bit more data to ensure that what’s encoded is error free. “In order to define a parabola, you basically need only three points,” said Reinhard Heckel from ETH Zurich’s Communication Technology Laboratory in a press release. “We added a further two in case one gets lost or is shifted.”

Mollusks Show the Way to Better Li-ion Batteries

Biomimicry has served as the foundation for a significant portion of nanotech research. Nature has had a few billion years to work out the most effective way to get things done on the nanoscale so it makes sense to do a fair amount of cribbing from it solutions.

Now researchers at the University of Maryland, Baltimore County (UMBC) have borrowed a process from mollusks to develop a method for improving the properties of lithium-ion (Li-ion) batteries.

Read More

New Manufacturing Method Promises Scalable Graphene Electronics Production

When you hear people sing the praises of graphene, they are usually referring to the single-crystal graphene that has many attractive properties like high electron mobility. Unfortunately, producing that pure single-crystal graphene requires a decidedly unscalable method known as the “Scotch Tape” method; graphene is pulled off in single-layer flakes directly from bulk graphite.

Chemical Vapor Deposition (CVD) has been seen as a bridge between scalability and purity in graphene production. With that technique, graphene is grown on a metal substrate like copper or nickel. But because the graphene eventually has to be peeled off of the metal substrate, the graphene can either be completely ruined or contaminated.

Now researchers at the University of Groningen in the Netherlands have devised a production method based on CVD that eliminates the potential for ruin or contamination while still remaining scalable. It is based on something they discovered when analyzing CVD-grown graphene three years ago.

“When we analyzed a sample of graphene on copper, we made some strange observations,” said Meike Stöhr, one of the researchers, in a press release.

What the researchers observed was that some copper oxide was present next to the copper. In fact, the graphene formed a kind of film on top of the copper oxide. Because oxidized metals are often used in passivation of electronics—a process in which a light coat of a protective oxide is used to create a shell against corrosion—the researchers suspected that the copper oxide layer could leave the graphene’s properties untouched.

In research published in the journal Nano Letters, the Groningen researchers took their initial observations and demonstrated the ability to grow graphene on copper oxide. Most importantly, the process of decoupling the graphene and copper oxide preserves the graphene’s attractive electronic properties.

While Stöhr concedes that their work will need to be duplicated by other research groups, their findings could have a long-reaching impact on the future of graphene devices. If this process enables the growth of large single-domain crystals of graphene, it would be possible to then use common lithographic techniques to etch a host of electronic devices in a way analogous to silicon.

Thermoelectric Nanowires Promise Energy Harvesting From Car Exhaust

Researchers at Sandia National Labs have developed a manufacturing process capable of controlling the crystal orientation, crystal size, and alloy uniformity of nanowires so that they could be used in a range of thermoelectric applications. 

Because thermoelectric materials are capable of generating an electrical current as a result of a difference in temperature between one side of the material and the other, the Sandia team believes the new nanowires could make it possible for carmakers to harvest power from the heat wasted by exhaust systems or lead to more efficient devices for cooling computer chips.

Nanowires have been suggested for a range of applications, but in thermoelectric applications, the quality of the nanowires has heretofore been inadequate. The trick for any thermoelectric material is to combine high electrical conductivity and relatively low thermal conductivity—a property known as thermoelectric efficiency.

Researchers have been investigating a number of nanomaterials for thermoelectric applications; traditional materials possess a relatively poor thermoelectric conversion efficiency or they are prohibitively expensive for commercial uses.

The Sandia researchers turned to nanowires despite their previous poor performance, believing that if they could better control the manufacturing process, they could improve the nanowires’ quality enough to make them a useful thermoelectric material.

In research published in the Cambridge Journal of Materials Research, the Sandia team employed a method known as room-temperature electroforming, which is widely used in commercial electroplating. In electroforming, material is deposited at a constant rate, which results in the nanowires growing uniformly.

This uniformity of composition held for the entire length of each nanowire and even across an array of them. The crystals that made up the nanowires were all oriented in one direction, making it easier for electrons to travel along the conduits.

“There are little nuances in the technique that I do to allow the orientation, the crystal growth, and the composition to be maintained within a fairly tight range,” said Graham Yelton of Sandia in a press release. “It’s turning the knobs of the process to get these things to behave.”

The next step in the research will be to make an electrical contact with the nanowire-based material and to measure the resulting thermoelectric behavior.

One hurdle the team has to overcome: “Thermoelectric materials readily form oxides or intermetallics, leading to poor contact connections or higher electrical contact resistance. That reduces the gains achieved in developing the materials,” Yelton said.

So far the team has had some success in getting good contact at the bottom of an array, but making a connection at the top has proved difficult.

At the moment, the researchers are seeking additional funding to solve the problem of making contacts, and then they plan to characterize the thermal electric properties of the arrays.

Is "Valleytronics" the Next Big Thing in Quantum Computing?

Researchers at the Lawrence Berkeley National Laboratory (LBL) have developed a new pathway to achieving “valleytronics” using two-dimensional (2D) semiconductors.  The LBL researchers believe that this new approach could make valleytronics a more stable alternative to “spintronics” as a replacement for traditional electronics.

The term valleytronics is starting to filter into in the lexicon of cutting-edge electronics research. What it actually means is complicated, but it represents a movement away from exploiting the electrical charge of electrons as a means for storing information and instead using the wave quantum number of an electron in a crystalline material to encode data.

Read More

Transistor Made From Silicene for First Time

Ever since silicene—a one-atom-thick layer of silicon—was first predicted in computer models a decade before graphene was first synthesized in 2004, it’s been on a roller coaster ride. It’s gone from being considered the next big thing to being thought of as an impossibility outside of computer models.

Drawing on an increasing amount of recent research demonstrating that silicene can survive—for at least a little while—outside the virtual world of computer models, researchers at the University of Texas at Austin have taken it all a step further by demonstrating a method for fabricating a field-effect transistor out of silicene. The device reportedly lives up to the switching speeds that had been promised in the computer models. Most importantly, this research marks the first time that anyone has been able to fabricate a transistor out of silicene.

In research published in the journal Nature Nanotechnology, the Texas researchers grew their silicene on a thin film of silver and capped it with aluminum oxide. Adding this light coat of protective oxide to create a protective shell—what’s known in the business as passivation—has recently proven effective in protecting graphene devices.

The researchers took the encapsulated silicene and placed it on a silicon dioxide wafer with the silver side up. They then put patterns into the silver side that would allow for contacts to be made so it could operate as a transistor.

The device was not tested in the open air, but it at least remained stable in vacuum conditions. Of course, this situation is not practical for real-world applications, but the researchers feel that this marks an important step towards realizing commercially viable silicene-based transistors.

The experimental research does confirm some of the theories that had been based solely on computer models. It demonstrated that silicene has electrical properties similar to those of graphene, including allowing electrons to travel through the material without any barriers.

While this research provides some confirmation of silicene’s attractive electronic properties, the research falls somewhat short of supporting the notion that because silicene is made from silicon it will be easier for the electronics industry to adopt. Silicene may be a one-atom-thick relative of silicon, which the electronics industry has characterized for the last half-century, but this research doesn’t seem to indicate that it has become any more friendly to large-scale manufacturing than its more mature cousin.

Nanoballs Inflate Voltage Capacity of Power Cables, Save Energy

While nanotechnology gets a lot of attention for enabling news types of energy generation, such as photovoltaics,  or ushering in a new energy storage technology, it may in fact be in the mundane role of energy savings and efficiency where it may hold the most promise.

Along these lines, researchers at the Chalmers University of Technology in Sweden have demonstrated that the addition of carbon nanoballs (also known as C60, Buckyballs, and fullerenes) into the plastic insulation used in high-voltage lines enable the cables handle up to 26 percent more voltage than standard cables.

Read More

Graphene Becomes Magnetic and Electric at Same Time

Combining the electric with the magnetic in one material has become a hot research pursuit lately. First researchers exploited the natural properties of bismuth ferrite. Then researchers engineered both electric and magnetic polarization in perovskite—a material that does not have that property naturally.

Now researchers at the University of California Riverside have brought this combination of the electric and the magnetic to the wonder material, graphene.

Of course, it is possible to induce magnetism in graphene by doping the material with magnetic impurities. Unfortunately, that process comes at the high cost of eliminating all the attractive electrical properties of graphene, such as its high conductivity.

The UC Riverside researchers found a way to make graphene magnetic without sacrificing its attractive electrical properties.

Read More

Perovskite Manipulated To Carry Both Electrical and Magnetic Polarization

Researchers at the University of Liverpool in the UK have demonstrated the ability to manipulate a material so that it has both magnetic and electrical polarization, a feature that could lead to low-power electrical writing of information with non-destructive magnetic reading, and logic devices that can operate without charge current flow.

A fair amount of research has gone into exploiting this property of both electrical and magnetic polarization in bismuth ferrite, which has the rare property of possessing a permanent local magnetic field while always possessing an electric polarization that can be switched by applying an electric field.

However, in research published in the journal Science, the Liverpool team employed crystal chemistry to engineer specific atomic displacements in a layered perovskite to give it properties it did not previously possess. Perovskites are a class of crystals that have become all the rage, especially in the world of photovoltaics, because of their low cost, high charge-carrier mobility, and long diffusion lengths. In real world terms, this means that the electrons in perovskite-based photovoltaics can travel through thicker solar cells, which absorb more light and thereby generate more electricity than thinner cells.

In these most recent experiments, concern for perovskites’ attractive properties in photovoltaics were set aside so that the perovskite crystal could be engineered to have a novel set of properties.

“By designing in the required atomic-level changes using both computation and experiment together, we produced three properties (polarization, magnetization, magnetoelectricity) from a material that initially displayed none of them,” said Liverpool professor Matthew Rosseinsky, in a press release.

Rosseinsky added: “We were able to demonstrate that the magnetization and polarization are coupled by measuring the linear magnetoelectric coefficient, a key physical quantity for the integration of such materials in a device. This coupling arises because both properties are produced by the same single set atomic motions that we built in to the material.”

While these developments could potentially lead to applications for information storage, the researchers concede that a number of challenges still have to be overcome before making that step, including switching the polarization and making the material more electrically insulating.

Graphene Devices Stand the Test of Time

In the decade since graphene was first synthesized, researchers have been preoccupied about overcoming the fact that the material lacks an inherent band gap, which limits its potential in digital logic applications.

While researchers have been reasonably successful at engineering a band gap into graphene in the lab, there is another looming show stopper: How robust is the material when facing real-world environments?

Now researchers from AMO GmbH in Germany and Spain-based Graphenea SE have demonstrated a sophisticated encapsulation technique that they claim is easily reproducible and should allow graphene devices in normal atmosphere to last for several months.

What typically is the death knell for graphene is partly the result of the environment and also the impurities in the production process. As far as the environment is concerned, moisture or oxygen causes the problem. From the production side, the residue from lithography processes adhere to the graphene and change its doping level unintentionally.

The doping levels change the properties that make graphene so attractive in the first place—such as its conductivity and its optical properties. As a result, all the great capabilities that graphene is heralded for are largely lost.

In research published in the Royal Society of Chemistry journal Nanoscale,  the team first identified this problem and then devised their encapsulation technique to overcome it.

The researchers applied their encapsulation technique to field-effect devices using aluminum oxide, an encapsulation material that is often used in making organic light-emitting diodes (OLEDs).

To a technique known in the business as passivation, in which a light coat of a protective oxide is used to create a shell against corrosion, the researchers added a bit of a wrinkle. They were able to grow the oxide layer using an oxidized layer of aluminum that served as as the seed for further growth. This new twist to the passivation technique managed to stabilize the device characteristics over several months when stored and measured in ambient atmosphere.

The researchers believe that this development serves as a major step torward getting graphene devices into real-world applications.

Advertisement

Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
Contributor
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
Load More