Meet the Nimble-Fingered Interface of the Future

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All-carbon-nanotube transistor can be crumpled like a piece of paper

The researchers, Shinya Aikawa and coauthors from the University of Tokyo and the Tokyo University of Science, have published their study in a recent issue of Applied Physics Letters.
“The most important thing is that electronics might now be usable in places or situations that were previously not possible,” coauthor Shigeo Maruyama, a mechanical engineering professor at the University of Tokyo, told “Since our device is so flexible and deformable it could potentially be stuck anywhere. This could lead to active electronic devices that are applied like a sticker or an adhesive bandage, as well as to wearable electronics.”

Unlike other field-effect transistors (FETs), the new FET is unique in that all channels and electrodes are made of carbon nanotubes (CNTs), while the substrate is made of highly flexible and transparent poly(vinyl alcohol) (PVA). Previously, the majority of flexible, transparent FETs have used gold or indium tin oxide as electrodes. However, gold decreases the devices’ transparency while brittle indium tin oxide limits the flexibility. A few recent FETs have been made that consist entirely of CNTs, but so far these devices have been built on thick plastic substrates, limiting their flexibility.
 The present device (1 mm curvature) is the most bendable CNT-FET to date without performance degradation. Image credit: Aikawa, et al. ©2012 American Institute of Physics

After patterning the components using standard photolithography and laminating the device with the PVA, the final thickness of the new all-CNT-FET was approximately 15 µm. This thinness made the device highly pliable, with tests showing that the finished transistor could withstand a 1-mm bending radius with almost no changes in electrical properties. Although other transistors have been developed with bendable radii as low as 0.1 mm, the new transistor is the most bendable that experiences no performance degradation. 

After subjecting the transistor to 100 wrinkling cycles, the researchers observed a slight decrease in maximum drain current, which may be due to some broken connections in the CNT network. However, the minimal decrease in maximum drain current, which stabilizes after about 30 cycles, does not affect the overall transconductance, which was not affected by the repeated bending. 
In addition to its flexibility, the all-CNT-FET also has an optical transmittance of more than 80%, which is sufficient to clearly see through the device. The researchers attribute the high flexibility to the inherent robustness of carbon nanotubes, and predict that they could increase the flexibility even further by optimizing the positions of the channels. Overall, the results demonstrate that flexible, transparent all-carbon electronics are coming closer to commercial reality.

“Ongoing topics are to control device properties and to integrate them,” Maruyama said. “If these issues can be resolved, we would like to realize flexible and transparent all-carbon working circuits.”
From physorg

Generating Power from Salty Water: Unique Salt Allows Energy Production to Move Inland

"We are taking two technologies, each having limitations, and putting them together," said Bruce E. Logan, Kappe Professor of Environmental Engineering. "Combined, they overcome the limitations of the individual technologies."

 Microbial reverse dialysis test cell. (Credit: Penn State, Dept of Public Information)

The technologies Logan refers to are microbial fuel cells (MFC) -- which use wastewater and naturally occurring bacteria to produce electricity -- and reverse electrodialysis (RED) -- which produces electricity directly from the salinity gradient between salty and fresh water. The combined technology creates a microbial reverse-electrodialysis cell (MRC). The researchers describe MRCs in  the March 1 edition of Science Express.

RED stacks extract energy from the ionic difference between fresh water and salt water. A stack consists of alternating ion exchange membranes -- positive and negative -- with each RED membrane pair contributing additively to the electrical output. Unfortunately, using only RED stacks to produce electricity is difficult because a large number of membranes is required when using water at the electrodes, due to the need for water electrolysis.

Using exoelectrogenic bacteria -- bacteria found in wastewater that consume organic material and produce an electric current -- reduces the number of stacks needed and increases electric production by the bacteria.

Logan, working with Roland Cusick, graduate student in environmental engineering, and postdoctoral fellow Younggy Kim, placed a RED stack between the electrodes of an MFC to form the MRC.

While the researchers previously showed that an MRC can work with natural seawater, the organic matter in water will foul the membranes without extensive precleaning and treatment of the water. Seawater use restricts MRC operation to coastal areas, but food waste, domestic waste and animal waste contain about 17 gigawatts of power throughout the U.S. One nuclear reactor typically produces 1 gigawatt.

Rather than rely on seawater, the researchers used ammonium bicarbonate, an unusual salt. An ammonium bicarbonate solution works similarly to seawater in the MRC and will not foul the membranes. The ammonium bicarbonate is also easily removed from the water above 110 degrees Fahrenheit. The ammonia and carbon dioxide that make up the salt boil out, and are recaptured and recombined for reuse.

"Waste heat makes up 7 to 17 percent of energy consumed in industrial processes," said Logan. "There is always a source of waste heat near where this process could take place and it usually goes unused."

The researchers tested their ammonium bicarbonate MRC and found that the initial production of electricity was greater than that from an MRC using seawater.

"The bacteria in the cell quickly used up all the dissolved organic material," said Logan. "This is the portion of wastewater that is usually the most difficult to remove and requires trickling filters, while the particulate portion which took longer for the bacteria to consume, is more easily removed."

The researchers tested the MRC only in a fill and empty mode, but eventually a stream of wastewater would be run through the cell. According to Logan, MRCs can be configured to produce electricity or hydrogen, making both without contributing to greenhouse gases such as carbon dioxide. The MRC tested produced 5.6 watts per square meter.

Logan also said not having to process wastewater would save about 60 gigawatts.
The King Abdullah University of Science and Technology supported this work.

From sciencedaily

Bacteria Communicate by Touch, New Research Suggests

The findings appeared recently in the journal Genes & Development.
Christopher Hayes, UCSB associate professor of molecular, cellular, and development biology, teamed with graduate students Elie Diner, Christina Beck, and Julia Webb to study uropathogenic E. coli (UPEC), which causes urinary tract infections in humans. They discovered a sibling-like link between cell systems that have largely been thought of as rivals.

 Associate professor Christopher Hayes and graduate student Christina Beck

The paper shows that bacteria expressing a contact--dependent growth inhibition system (CDI) can inhibit bacteria without such a system only if the target bacteria have CysK, a metabolic enzyme required for synthesis of the amino acid cysteine. CysK is shown to bind to the CDI toxin -- an enzyme that breaks RNA ó and activate it.

For a cell system typically thought of as existing only to kill other bacteria -- as CDIs have largely been -- the results are surprising, said Hayes, because they suggest that a CDI+ inhibitor cell has to get permission from its target in order to do the job.

"This is basically the inhibitor cell asking the target cell, 'Can I please inhibit you?'" he explained. "It makes no sense. Why add an extra layer of complexity? Why add a permissive factor? That's an unusual finding.

"We think now that the [CDI] system is not made solely because these cells want to go out and kill other cells," Hayes continued. "Our results suggest the possibility that these cells may use CDI to communicate as siblings and team up to work together; for example, in formation of a biofilm, which lends bacteria greater strength and better odds of survival."

The study points to the enzyme CysK as the potential catalyst to such bacterial communication -- like a secret handshake, or a password. In simpler terms, said Hayes, "If you have the right credentials, you're allowed into the club; otherwise you're turned away. There's a velvet rope, if you will, and if you're not one of the cool kids, you can't get in."

Although only UPEC was studied for this paper, Hayes said that the findings hold potential implications for pathogens from bacterial meningitis to the plague, as well as for plant-based bacteria that can devastate vegetation.

David Low, a UCSB professor of molecular, cellular, and developmental biology and secondary author on the paper, described the work by Hayes's laboratory as potentially groundbreaking for its insights into how bacteria communicate -- and the practical applications that could someday result.
"We are just starting to get some clues that bacteria may be talking to each other with a contact-dependent language," said Low. "They touch and respond to one another in different ways depending on the CDI systems and other genotypic factors. Our hope is that ultimately this work may aid the development of drugs that block or enhance touch-dependent communication, whether the bacteria is harmful or helpful."

The work was supported by grants from the National Institutes of Health and the National Science Foundation.

From sciencedaily

In Space and On Earth, Why Build It, When a Robot Can Build It for You?

That's just one thing researchers in Hod Lipson's Creative Machines Lab envision with their latest robot prototype. It can autonomously traverse and manipulate a 3-D truss structure, using specially designed gears and joints to assemble and disassemble the structure as it climbs. Lipson is an associate professor of mechanical and aerospace engineering, and of computing and information science at Cornell University.

 Jeremy Blum '12 holds one version of a prototype robot that can autonomously climb, assemble and disassemble truss structures.

The robot's design is detailed in a paper accepted by IEEE Robotics and Automation, to appear soon online and in print. Its co-authors include former visiting scientist Franz Nigl, former visiting Ph.D. student Shuguang Li, and undergraduate Jeremy Blum.

"What gets me most excited is this idea of safety," said Blum, a student researcher working on the project. Having a robot able to climb and reconfigure building structures, even just to deliver materials, would be a step toward making construction zones safer for humans, he said.

The researchers also point to space-exploration applications. Instead of sending astronauts out on a dangerous spacewalk at the International Space Station, a robot could be deployed to repair a damaged truss.

The robot is equipped with an onboard power system, as well as reflectivity sensors so it can identify where it is on the structure. This allows it to maneuver accurately without explicit commands, Blum added.

Lipson said he envisions transforming the built environment with the help of these kinds of technologies. Instead of making buildings out of concrete or other non-recyclable materials, components designed specifically for robots could be used to build or reconfigure structures more efficiently -- for example, after an earthquake, or if an outdated building needed to be torn down in favor of something better.

"Right now, we are very bad at recycling construction materials," Lipson said. "We are exploring a smarter way to allow the assembly, disassembly and reconfiguration of structures."

The project is part of a National Science Foundation Emerging Frontiers in Research and Innovation grant jointly awarded to Lipson at Cornell, Daniela Rus of the Massachusetts Institute of Technology, Mark Yim of the University of Pennsylvania, and Eric Klavins of the University of Washington.

From sciencedaily

Depression: An Evolutionary Byproduct of Immune System?

Some previous proposals for the role of depression in evolution have focused on how it affects behavior in a social context. A pair of psychiatrists addresses this puzzle in a different way, tying together depression and resistance to infection. They propose that genetic variations that promote depression arose during evolution because they helped our ancestors fight infection.

 Could depression be an evolutionary byproduct of the ability to fight infection?

An outline of their proposal appears online in the journal Molecular Psychiatry.
The co-authors are Andrew Miller, MD, William P. Timmie professor of psychiatry and behavioral sciences at Emory and director of psychiatric oncology at Winship Cancer Institute, and Charles Raison, MD, previously at Emory and now at the University of Arizona.

For several years, researchers have seen links between depression and inflammation, or over-activation of the immune system. People with depression tend to have higher levels of inflammation, even if they're not fighting an infection.

"Most of the genetic variations that have been linked to depression turn out to affect the function of the immune system," Miller says. "This led us to rethink why depression seems to stay embedded in the genome."

"The basic idea is that depression and the genes that promote it were very adaptive for helping people -- especially young children -- not die of infection in the ancestral environment, even if those same behaviors are not helpful in our relationships with other people," Raison says.

Infection was the major cause of death in humans' early history, so surviving infection was a key determinant in whether someone was able to pass on his or her genes. The authors propose that evolution and genetics have bound together depressive symptoms and physiological responses that were selected on the basis of reducing mortality from infection. Fever, fatigue/inactivity, social avoidance and anorexia can all be seen as adaptive behaviors in light of the need to contain infection, they write.

The theory provides a new explanation for why stress is a risk factor for depression. The link between stress and depression can be seen as the byproduct of a process that preactivates the immune system in anticipation of a wound, they write.

Similarly, a disruption of sleep patterns can be seen in both mood disorders and when the immune system is activated. This may come from our ancestors' need to stay on alert to fend off predators after injury, Miller says.

Miller and Raison's theory could also guide future research on depression. In particular, the presence of biomarkers for inflammation may be able to predict whether someone will respond to various treatments for depression.

Miller and Raison are involved in ongoing research on whether certain medications, which are normally used to treat auto-immune diseases, can be effective with treatment-resistant depression.

From sciencedaily

City with Superfast Internet Invites Innovators to Play

Citizens in Chattanooga, Tennessee, have access to one-gigabit-per-second Internet—that's 100 times the U.S. national average, and fast enough to download a two-hour movie in about five seconds. The only question is: what to do with it?

 Wired up: These fiber-optic cables provide one-gigabit-per-second data to 150,000 homes and businesses in Chattanooga, Tennessee.

The city is hoping a contest with $300,000 in prize money will help answer that question. Entrants are invited to come up with clever ways of making use of the city's blisteringly fast Internet, which was installed in late 2010 with a $111 million U.S. Department of Energy grant, as part of federal stimulus efforts that also built out the city utility's long-planned smart grid. 

Some early entries include health-care applications, such as transferring larger files like CT scans in real-time so that specialists can serve a larger area. Ideas contributed by students include a platform for high-definition video debates, and international collaborations with students in Sri Lanka, London, Jamaica, and elsewhere.

But even if some great ideas come out of the contest, the fact remains that most people in the U.S. still have access to only relatively slow Internet connections. Late last year, the United States ranked 25th in the world for average available Internet speed. By the end of this year, South Korea, a world leader in Internet speed, will provide one-gigabit service nationwide for about $27 a month.

Furthermore, where superfast Internet is available in the U.S., it is typically prohibitively expensive. The Chattanooga service has been available for more than a year to 150,000 residential and commercial customers for $350 per month, but it has so far found only eight residential subscribers and 18 commercial ones.

Even so, in Tennessee they are optimistic that the contest will bring rewards. "Eventually, these fatter pipes will get filled with bandwidth-eating applications," says Jack Studer, partner at the Lamp Post Group, a VC firm in Chattanooga that, along with companies including Alcatel, Cisco, and IBM, is sponsoring the contests.

"What we are trying to do is inject some capital into innovation, with the goal of driving demand for higher-bandwidth networks and jump-start adoption across the country and world," Studer says. "We plan to do this for multiple years—in the second and third year, we may see a revolutionary jump to things we may not be thinking about now." 

 Get connected: A utility box in Chattanooga.

The $300,000 prize money will be split among students and entrepreneurs. Ten startups will get $15,000 this summer to develop and test their gigabit business ideas. A local judging panel will give a $100,000 prize for the winner. A separate student contest will carry a $50,000 prize. The deadline for entries is March 1.

Chattanooga is the only place in the United States providing such high-speed service. But others are on the way: Google is going into the Internet service provider business, stringing fiber on telephone poles in Kansas City, Missouri, and adjacent Kansas City, Kansas. The first of its customers should get a connection by the middle of 2012, a spokesman says. 

Video is the fastest-growing bandwidth-hogging app, and it could be an important driving force for faster Internet speeds. Google is, in fact, hoping to provide a TV service as part of its broadband efforts. Earlier this month, the company filed applications with the Missouri Public Service Commission and the Kansas Corporation Commission that would allow it to supply a TV service.
The U.S. Federal Communications Commission in 2010 defined "basic broadband" as at least four-megabits-per-second download speed and one-megabit-per-second upload speed. The efforts in Chattanooga and Kansas City are a step toward carrying out the FCC's ambitious National Broadband Plan, which aims to not only provide this minimal level of service to every community, but also to achieve the more ambitious goal of providing a majority of households with 100-megabit-per-second service by 2020. 

The Chattanooga network was built by the city-owned Electric Power Board. The utility uses the fiber partly for a smart electric grid that does things like detect overloads and reroute power on the fly to avoid costly brownouts.

History suggests that faster broadband spurs innovation and new business, says Rob Vietzke, vice president of network services at Internet2, a networking consortium that provides blazing fast Internet to research labs and government agencies. For example, in 2005, YouTube emerged with an application enabled by the growing availability of broadband in U.S. homes and businesses. "Projects like Chattanooga and Kansas City reopen the opportunity for innovation," Vietzke says. "You can't predict exactly what will happen, but it lays the groundwork for people to think differently about how they do their work."

One possible application of one-gigabit service involves streaming super-high definition video at four or more times the resolution of current HD technology, Vietzke says. Such high-quality streams could be useful for telemedicine and realistic remote meetings, but would require at least 100-megabit service, he adds.

Internet2, for its part, is working on delivering 100-gigabit service, initially to research centers in Indiana and Ohio—useful for such applications as crunching data from genomics research and from particle physics experiments at the Large Hadron Collider. (Some scientific instruments dish out even more data—deep-space telescopes, for example, can generate one terabit a second.)

All of this is way beyond the perceived needs of the average Chattanoogan. "Anything that makes my Netflix streaming move faster is okay with me," quips Tom Balázs, an assistant professor of English at the University of Tennessee in Chattanooga.

By David Talbot
From Technology Review

Why a Portable DNA Device Could Yield Better Data

Oxford Nanopore Technologies announced recently that it has two products capable of sequencing DNA by reading the chemical bases in a DNA molecule directly, as it is threaded through a nanoscopic hole in a protein. The U.K.-based company will begin selling a simple, disposable, portable $900 DNA-reading device, and a more comprehensive desktop model, by the end of the year.

 Mini sequencer: The MinION from Oxford Nanopore plugs into a computer like a USB memory stick. The single-use sequencer will be on the market for under $900 sometime this year.

If Oxford Nanopore's technology can do what the company claims, it will be "a total game-changer," says Jeffery Schloss, director for technology development at the National Human Genome Research Institute, part of the National Institutes of Health. 

The technology relies on the fact that a DNA base, or a combination of bases on a DNA strand creates a characteristic disruption in a current as it passes through the nanopore. Electrodes measure the change in current flow as DNA molecules are fed through protein nanopores; an electrical gradient drives the DNA through the pore, while molecular "controllers" attached to the molecules mechanically slow them down so that their electrical signals may be recorded. 

This approach has two important advantages.
First, the system is compact and doesn't require a supply of expensive reagents. That means sequencing can come out of the lab, making it useful for personalized medicine or for use in resource-poor clinics. Indeed, the disposable sequencer the company is about to introduce is the size of a USB memory stick. 

Second, the technology reads much longer stretches of DNA than other rapid sequencing approaches, which means it has the potential to be better at spotting important "structural variants" related to disease. These variants occur when a whole segment of chromosome is moved, inverted, duplicated, or otherwise changed. When DNA is chopped into shorter stretches to be sequenced and then put back together on a computer, it is easier to miss, or misinterpret, such variants.

The best way to identify variants is still to use conventional sequencing methods, which are highly accurate but also expensive and slow. Other rapid sequencers released in recent years are fast and inexpensive, but Schloss believes Oxford Nanopore's may have an edge when it comes to spotting structural variants.

Better structural information could be useful for personalized medicine. Among other things, it could identify cases of translocation, a chromosomal abnormality in which large stretches of DNA break away from the chromosome where they belong and reattach someplace else. These mutations can cause cancer and other diseases. 

The company's portable nanopore sequencers could be used in the field—for example, to quickly identify or sequence a new strain of bacteria. A spokesperson for Oxford Nanopore says the portable sequencers might be used to monitor wound care in hospitals or to aid in on-site monitoring of agricultural sites for food safety.

At a research conference last week in Marco Island, Florida, Oxford Nanopore reported continuously sequencing 100,000-base stretches of DNA in the lab—sequences about 10 to 100 times longer than any other company has read. Pacific Biosciences' newest commercial machines are capable of sequencing up to 3,000 bases at once, says the company's director of product management, Edwin Hauw. 

But nanopore sequencing could go way beyond this. In theory, the only limit on the length the system can sequence is researchers' ability to prepare the inherently fragile samples. Human chromosomes encompass a million or so DNA bases.

The Oxford Nanopore system so far has a raw error rate of 4 percent. In the short term this might be improved by sequencing the same strand of DNA multiple times, threading it back and forth through the pore. However, the company says that in the coming months it will make improvements to the nanopore and the algorithms associated with the DNA analysis that will also reduce the error rate. 

By Katherine Bourzac
From Technology Review