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Nanowires and Viruses Combine to Create High-Capacity Batteries

While lithium-ion (Li-ion) batteries have managed to elevate hybrid vehicles into a significant segment of the automotive market, all-electric vehicles using that same battery technology have languished as a niche product. Li-ion batteries just don’t have the long charge life or short recharging capabilities that would make all-electric vehicles a good fit for most people’s driving habits. (It also doesn’t help the marketing image of automakers when these all-electric vehicles burst into flames.)

Marketing considerations aside, the recent demise of a few high-profile nanotech companies that tried to make Li-ion batteries for all-electric vehicles may indicate fundamental problems with the current approach. Maybe we need a different battery technology to make all-electric vehicles mainstream.

This realization already began to sink in with the research communities a few years back, and I started noticing more research into Lithium-air batteries.  Lithium-air batteries use the oxidation of lithium at the anode and the reduction of oxygen at the cathode to create a current. This battery design has promised up to 10 times as much energy as a lithium-ion battery at the same weight, giving them an energy density equal to that of gasoline.

Greater storage capacity certainly helps solve one EV limitation, but if a battery technology is going to displace fossil fuels, it also needs to recharge as quickly as—or on par with—filling up a car at gas station. Earlier this year, researchers at Massachusetts Institute of Technology (MIT) and Sandia National Laboratory peered into the lithium oxidation process of Li-air batteries and saw a possible way to speed up battery recharging.

Now researchers—again from MIT—have made progress on both fronts. They took nanowires made of manganese oxide (which is often used as the material for the cathode of Li-air batteries) and coated them with man-made viruses. These viruses create a larger surface area that improves the reaction between the lithium and oxygen, resulting in a greater storage capacity and a faster rate of recharging. A video describing the technology can be seen below.

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Flexible Mobile Devices Get a Flexible Battery Made From Nanotubes

After years of promises that mobile phones were going to become flexible, Samsung announced plans last month to release its flexible phone.

While the Samsung Galaxy Round is not flexible to the extent you can bend it to your heart’s content, it does offer a display that is flexible enough for the manufacturer to curve it. The move has also spurred other mobile device manufacturers to announce their intentions to market similar devices.

With the age of flexible devices seemingly upon us, one of the primary challenges for their development has been the power source. Samsung’s new phone is more or less powered by a standard rigid battery. But both LG and Samsung acknowledged that they are on a quest to develop a flexible battery that will enable a truly flexible phone.

Researchers, who anticipated that the launch of flexible mobile devices would require a flexible power source, have steadily pursued the flexible battery. There have been a few commercial efforts using printed electronics, and some thin-film technologies that have made a splash.

Now researchers at the New Jersey Institute of Technology (NJIT) have developed a flexible battery made from carbon nanotubes that is aimed at powering flexible devices. 

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Tricorder-like Mobile Phones Enabled by Nanotechnology

Your typical mobile phone user—who may be cursing his or her smart phone because the battery runs out after just a few hours of normal usage—may not be thinking: What this phone really needs is a spectrometer built into it. But if they knew what spectrometers could do, they might change their minds.

How about a smart phone that you could wave over the fruit and vegetables at the grocery store in order to determine whether they are ripe? That’s the kind of Star Trek Tricorder, gee-whiz technology that gets people to buy a smart phone.

Researchers at the Technische Universität Dresden and the Fraunhofer Institute for Electron Beam and Plasma Technology in Germany have developed a technology that could enable exactly that kind of capability. The German researchers have created a novel, miniature spectrometer, enabled by metallic nano-antennas, small enough to fit onto a mobile phone.

In addition to checking on the ripeness of produce, it could also serve in a more critical role as a tool for diabetes patients to monitor their blood-sugar levels. Of course, using nanotechnology to make your mobile phone into a portable medical monitor is not a new concept. But what distinguishes this latest research out of Germany is that the thin-film manufacturing technique employed makes the spectrometer sensor compatible with mass production.

Even if you could shrink a spectrometer—which measures light over a specific portion of the electromagnetic spectrum—to its smallest physical dimensions using conventional techniques and have it still work, it would not fit onto a mobile phone. The trick employed by the German researchers is the use of metallic nanowires that serve as nano-antennas to absorb, amplify and redirect the light onto the light detector—a CCD/CMOS chip that houses the antenna array. This makes it possible to miniaturize the spectrometer to a scale never conceived of before. The only limit to the size of the spectrometer is how small you could make the CCD/CMOS chip.

The three-year-long research project, dubbed "nanoSPECS", began in August of this year. Naturally, it is still at a preliminary stage, but the researchers expect that by the end of the project, they will be able to manufacture the graded antenna-array to the 8”-wafer size.

If the German researchers are successful, at that point you will have a smart phone that you can wave over a plum or canteloupe to pick the best, and you might even have a way to power the phone so that it would last as long as a Tricorder.

Image: Fraunhofer


Nanotechnology Offers Potential to Predict Football Concussions

American football is a collision sport. And one consequence of repeated collisions between players is concussions. Science is starting to draw a link between these so-called mild brain injuries and the long-term effects they have on the players—namely the onset of chronic traumatic encephalopathy (CTE), a degenerative condition believed to be caused by head trauma and linked to depression and dementia. Recently, the issue has come to a head with the deaths of several former star players and the broadcast of the Frontline report “League of Denial,” which chronicles scientists' long struggle to convince NFL officials to recognize a link between concussions and CTE.

While the NFL has tried to institute rules aimed at limiting the number of concussions that players suffer, the new regulations don’t seem to have stemmed the tide of brain injuries. Each week, a slew of player concussions are reported.

Another avenue being pursued in the hopes of limiting player concussions is the engineering of better helmets to improve head protection. An IEEE Spectrum article published last year, “Ratings for Football Helmets Help Improve Player Safety—But Not Before Another Tragedy,” reported on efforts to measure the effectiveness of different football helmets in reducing head trauma and categorize them based on their efficacy.

Now researchers at Brigham Young University have taken this measurement of helmet impact one step further with immediate, real-time measurements of each hit that a player endures. From those measurements, which are communicated immediately to a hand-held device, coaches know whether a collision is capable of inducing a concussion, even if the player denies any problem. A description of the technology is provided in the video below.

“A coach will know within seconds exactly how hard their player just got hit,” said Jake Merrell, a student at BYU who developed the technology, in a press release. “Even if a player pops up and acts fine, the folks on the sidelines will have data showing that maybe he isn’t OK.”

The heart of the technology is smart foam enabled by nanoparticles, which Merrell has dubbed “ExoNanoFoam.” The nano-enabled foam behaves as a piezoelectric in which pressure on the material produces an electrical voltage. A microcontroller sensor in the helmet reads the electrical voltage produced by the foam, and sends a signal to a handheld tablet equipped with a program that interprets it and delivers  real-time information on the seriousness of the hit sustained by the player.

Since the foam is actually in contact with the player's head, it provides a more accurate measurement of the forces upon the player’s head than the accelerometers that have been used previously to measure these impacts. The drawback with accelerometers is that they measure only of the acceleration or deceleration of the player’s helmet.

Merrell intends to submit his prototype to the upcoming Head Health Challenge, which aims to develop new technologies for measuring impacts in real-time in order to improve player safety.

Photo: Brigham Young University


Nanoparticle Enables Cheap and Easy Test for Blood Clots

Despite the wide range of diseases and conditions that can be diagnosed through a urine test, these tests have failed up till now in being able to detect blood clots. The terrible effects of blood clots include death so a cheap and easy detection method could save lives.

Now researchers at MIT have developed a simple urine test that can detect blood clots.The test centers around an iron oxide nanoparticle that is coated with peptides (short proteins) capable of detecting the enzyme thrombin, which is an indicator of blood clots.

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Engineers Make Electrical Contact to Graphene on It's 1-Atom-Thick Edge

Graphene has presented all sorts of barriers for efforts to apply the material to electronics. It lacks a band gap, so research has focused on engineering one into it. Then even if you could engineer a band gap into the material, its challenging to manufacture at a high quality and high volume.

Another big obstacle is that graphene does not lend itself to being stacked with other materials, something that could be important to making graphene ICs. The reason is that electrical contacts have to be placed on the top surface of the graphene, making the layering of another material on top of those contacts complicated.

Now researchers at Columbia University have developed a way to contact 2-D graphene from its 1-D side.

"No other group has been able to successfully achieve a pure edge-contact geometry to 2-D materials such as graphene," said Columbia electrical engineering professor Ken Shepard in a press release. "This is an exciting new paradigm in materials engineering where instead of the conventional approach of layer by layer growth, hybrid materials can now be fabricated by mechanical assembly of constituent 2-D crystals."

In a research published this week in the journal Science (“One-Dimensional Electrical Contact to a Two-Dimensional Material”), the Shepard and his colleagues created a stack of graphene with boron nitride (which is itself an intensively studied 2-D material, especially in combination with graphene).  After they created a boron-nitride-graphene-boron-nitride sandwich, they etched the stack to expose the edge of the graphene. They then evaporated metal onto those graphene edges to make an electrical contact.

While there was some concern that the electrical contact between the 3-D metal electrode and the one dimensional edge of the graphene would result in high contact resistance, it didn’t happen. Instead the researchers report that contact resistance was in fact lower than what can currently be achieved by making those contacts at the top of the graphene surface.

"Our novel edge-contact geometry provides more efficient contact than the conventional geometry without the need for further complex processing. There are now many more possibilities in the pursuit of both device applications and fundamental physics explorations,” said Shepard in the press release.

To start pursuing those new possibilities, the researchers are applying the techniques they developed for creating new hybrid materials of all the 2D materials that are gaining such interest of late.

"We are taking advantage of the unprecedented performance we now routinely achieve in graphene-based devices to explore effects and applications related to ballistic electron transport over fantastically large length scales," Cory Dean, who led the research as a postdoc at Columbia, said in the press release. "With so much current research focused on developing new devices by integrating layered 2D systems, potential applications are incredible, from vertically structured transistors, tunneling based devices and sensors, photoactive hybrid materials, to flexible and transparent electronics."

Illustration: Cory Dean/Columbia Engineering


Nanoparticle Both Kills Cancer Cells and Helps Image the Killing Process

The therapeutic capabilities of metallic nanoparticles continue to improve, especially for cancer treatment. Along with their growing therapeutic abilities, they are also piling up diagnostic capabilities as well, like their recent use in enabling iPod drug testing.

Now, thanks to researchers from the University of New South Wales in Australia, metallic nanoparticles have been used to both treat cancer and observe the treatment. This latest development is part of the emerging field of so-called “theranostic” nanoparticles in which the nanoparticle is both a therapeutic and a diagnostic tool.

In a first, the Australian researchers, who published their work in the journal ACS Nano ("Using Fluorescence Lifetime Imaging Microscopy to Monitor Theranostic Nanoparticle Uptake and Intracellular Doxorubicin Release"), used a fluorescence imaging technique to see the release of a drug inside lung cancer cells.

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How an iPod Could Transform Drug Testing

Researchers at Rice University  and a Houston-based startup have developed an iOS app that enables a nanoparticle-based assay to determine a drug’s toxicity to living tissue.

The mobile app essentially provides image analysis to drug screening method that is growing in popularity. The new method aims at replacing in vivo (in living subjects) methods with in vitro (in test tube) tests to determine how drugs affect living tissue.

A Houston-based startup, Nano3D Biosciences, has developed just such an in vitro test, dubbed “BiO Assay.” It creates 3-D tissue structures that mimic the results that previously could only be derived from running tests inside living tissue.

The method is based on magnetic levitation. A magnetic nanoparticle assembly consisting of gold nanoparticles, poly-L-lysine, and magnetic iron oxide binds to cells. This makes the cells themselves become magnetic so theycan be manipulated by an external magnetic field. (We’ve seen a variation on this use of magnetic nanoparticles in a cancer drug that is able to eradicate an ovarian tumor in a day.)  When the magnetic field is applied above the culture plate of the assay, the cells levitate (thus the name) from the bottom of the surface. This levitation results in them aggregating and interacting with each other to form larger 3-D cultures.

The Rice researchers took this technique and added an imaging system for it. In research published in the journal Scientific Reports (“A high-throughput three-dimensional cell migration assay for toxicity screening with mobile device-based macroscopic image analysis”),  the Rice team developed the iOS app as well as the analytic software, scientific protocols, and hardware to go with it. You can see an iPod equipped with the app performing its drug toxicity analysis in the video below.

The app essentially takes time-lapsed images of the 3-D cell cultures that have been exposed to varying levels of a drug. The analytical program then measures each sample and creates time-elapsed movies, graphs and charts of the drug's toxic profile.

“This literally collects about 100 000 data points during a 12-hour, overnight experiment,” said study co-author Shane Neeley, a Rice bioengineering graduate student, in a press release. “That’s all relevant publishable data that relate to the different times, doses, and cell types and other key variables in the experiment.”

Now you may be asking yourself—as I did—why is an iPod app needed for what is essentially a lab-based testing of drug toxicity? If you don’t already have the assay, this app is not going to make your iPod capable of testing the cytotoxicity of the ibuprofen you’re taking.

It turns out the interns of Nano3D Biosciences developed the app because they couldn’t be bothered with taking photos of the assay with their microscopes.

“Without looking in the microscope, just looking at the camera and clicking like a robot, it would take 20 minutes to take pictures of all 96 wells on one plate,” Glauco Souza, Nano3D’s president and chief scientific officer said in the press release. “To analyze that, all 96, with a ruler, took even longer.”

Whether this app will prove useful outside of keeping some lab interns from doing monotonous work remains to be seen. However, the team is trying to see where it can be applied next.

“We’re hoping to get this into some high school classrooms here in Houston, and we’re working with one of Houston’s largest community colleges, Lone Star College, to see if it can be used there,” Souza added.


Let's Make the Entire Chip from Graphene

The International Technology Roadmap for Semiconductors (ITRS) predicts that by 2015, copper-based vias that connect the silicon surface to a chips' wiring and connect one layer of wiring to another simply will not be able to do the job anymore. That day is a little over a year away—practically tomorrow in technological innovation terms. As a result, there is a bit of a scramble to find alternatives—not just for vias but for all sorts of interconnects used in integrated circuits (ICs).

Researchers at the University of California, Santa Barbara (UCSB) have taken an initial step in offering one possible alternative: “an integrated circuit design scheme in which transistors and interconnects are monolithically patterned seamlessly on a sheet of graphene.”

It’s been over 30 months since IBM demonstrated that it could make an integrated circuit using graphene; in this most recent research, the UCSB team demonstrated, using a computer model, that its design is feasible.  So where is the disconnect (pun intended)?

The IBM work involved a graphene field-effect transistor and inductor and other circuit components that were monolithically integrated on a single silicon wafer. The UCSB design proposes that every bit of the IC be made from graphene.

"In addition to its atomically thin and pristine surfaces, graphene has a tunable band gap, which can be adjusted by lithographic sketching of patterns—narrow graphene ribbons can be made semiconducting while wider ribbons are metallic,” explained Kaustav Banerjee, professor of electrical and computer engineering and director of the Nanoelectronics Research Lab at UCSB, in a press release. “Hence, contiguous graphene ribbons can be envisioned from the same starting material to design both active and passive devices in a seamless fashion and lower interface/contact resistances."

In the paper that was published in the journal Applied Physics Letters (“Proposal for all-graphene monolithic logic circuits”) the researchers demonstrate “that devices and interconnects can be built using the 'same starting material'—graphene.” While that is intriguing, what may really garner the interest of the semiconductor industry is the research paper's claim that, “all-graphene circuits can surpass the static performances of the 22-[nanometer] complementary metal-oxide-semiconductor devices.”

Commenting on the research, Professor Philip Kim at Columbia University noted: "This work has demonstrated a solution for the serious contact resistance problem encountered in conventional semiconductor technology. [It presents the] innovative idea of using an all-graphene device-interconnect scheme. This will significantly simplify the IC fabrication process of graphene based nanoelectronic devices."

Illustration: UCSB Nanoelectronics Research Lab


Two-Dimensional Materials Tackle the Diode

While graphene by itself has been generating enormous interest in both the research community and outside of it, what many are still missing is that we are in the midst of a two-dimensional material explosion that goes beyond just graphene.

Molybdenum disulfide (MoS2) is beginning to take center stage right behind graphene in the cast of 2-D materials that includes silicene (a single layer of silicon) and boron nitride. Nearly three years ago, MoS2 was revealed as a possible 2-D replacement for three-dimensional silicon in transistors.

Even though MoS2 had an advantage over graphene in that it has an inherent band gap, it was really first imagined as a complement to graphene in applications such as optoelectronics and energy harvesting, where thin, transparent semiconductors are required.

Now researchers at Northwestern have gone back to MoS2's complementary role and combined it with carbon nanotubes to create p-n heterojunction diode. The p-n junction forms the backbone of devices such as solar cells, light-emitting diodes, photodetectors, and lasers.

“The p-n junction diode is among the most ubiquitous components of modern electronics,” said Mark Hersam, director of the Northwestern University Materials Research Center, in a press release. “By creating this device using atomically thin materials, we not only realize the benefits of conventional diodes but also achieve the ability to electronically tune and customize the device characteristics. We anticipate that this work will enable new types of electronic functionality and could be applied to the growing number of emerging two-dimensional materials.”

In a paper published in the journal Proceedings of the National Academy of Sciences (“Gate-tunable carbon nanotube–MoS2 heterojunction p-n diode”), the Northwestern team used single-walled carbon nanotubes as the p-type semiconductor and the MoS2 as n-type semiconductor.

The researchers discovered that when they stacked the two semiconductors vertically on top of each other they formed a heterojunction that allowed for the tuning of the device’s electrical characteristics with an applied gate bias.

In addition to its tunability, the p-n heterojunction diode is highly light sensitive. The researchers exploited this capability by making an ultrafast photodetector with the diode that displayed an electronically tunable wavelength response.

With 2-D materials already proving capable of making field-effect devices, it is hoped that this latest addition of a p-n junction diode made from one will mark an important step in the next generation of electronics.



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

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