#More than 80%Efficiency Attained in New Ultralow-power Circuit Researchers at MIT developed a new ultralow-power circuit that improves efficiency of energy harvesting to more than 80 percent.
This can lead the way to tiny, solar-powered sensors. The latest buzz in the information technology industry regards he Internet of thingsthe idea that vehicles, appliances, civil-engineering structures, manufacturing equipment,
and even livestock would have embedded their own sensors that report information directly to networked servers,
aiding with maintenance and the coordination of tasks. Realizing that vision, however, will require extremely low-power sensors that can run for months without battery changes or,
even better, that can extract energy from the environment to recharge. Last week, at the Symposia on VLSI Technology And circuits, MIT researchers presented a new power converter chip that can harvest more than 80 percent of the energy trickling into it,
even at the extremely low power levels characteristic of tiny solar cells. Previous experimental ultralow-power converters had efficiencies of only 40 or 50 percent.
Moreover, the researcherschip achieves those efficiency improvements while assuming additional responsibilities. Where its predecessors could use a solar cell to either charge a battery
or directly power a device, this new chip can do both, and it can power the device directly from the battery.
All of those operations also share a single inductor the chip main electrical component which saves on circuit board space
but increases the circuit complexity even further. Nonetheless, the chip power consumption remains low. e still want to have battery-charging capability,
and we still want to provide a regulated output voltage, says Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on the new paper. e need to regulate the input to extract the maximum power,
and we really want to do all these tasks with inductor sharing and see which operational mode is the best.
And we want to do it without compromising the performance, at very limited input power levels 10 nanowatts to 1 microwatt for the Internet of things.
The prototype chip was manufactured through the Taiwan Semiconductor Manufacturing Company University Shuttle Program. Ups and downs The circuit chief function is to regulate the voltages between the solar cell, the battery,
and the device the cell is powering. If the battery operates for too long at a voltage that either too high or too low
for instance, its chemical reactants break down, and it loses the ability to hold a charge. To control the current flow across their chip, El-Damak and her advisor, Anantha Chandrakasan,
the Joseph F. and Nancy P. Keithley Professor in Electrical engineering, use an inductor, which is a wire wound into a coil.
When a current passes through an inductor, it generates a magnetic field, which in turn resists any change in the current.
Throwing switches in the inductor path causes it to alternately charge and discharge, so that the current flowing through it continuously ramps up
and then drops back down to zero. Keeping a lid on the current improves the circuit efficiency
since the rate at which it dissipates energy as heat is proportional to the square of the current.
Once the current drops to zero, however, the switches in the inductor path need to be thrown immediately;
otherwise, current could begin to flow through the circuit in the wrong direction, which would drastically diminish its efficiency.
The complication is that the rate at which the current rises and falls depends on the voltage generated by the solar cell,
which is highly variable. So the timing of the switch throws has to vary, too.
Electric hourglass To control the switchestiming, El-Damak and Chandrakasan use an electrical component called a capacitor,
which can store electrical charge. The higher the current, the more rapidly the capacitor fills.
When it full, the circuit stops charging the inductor. The rate at which the current drops off
however, depends on the output voltage, whose regulation is the very purpose of the chip. Since that voltage is fixed,
the variation in timing has to come from variation in capacitance. El-Damak and Chandrakasan thus equip their chip with a bank of capacitors of different sizes.
As the current drops, it charges a subset of those capacitors, whose selection is determined by the solar cell voltage.
Once again, when the capacitor fills, the switches in the inductor path are flipped. n this technology space,
there usually a trend to lower efficiency as the power gets lower, because there a fixed amount of energy that consumed by doing the work,
says Brett Miwa, who leads a power conversion development project as a fellow at the chip manufacturer Maxim Integrated. f youe only coming in with a small amount,
it hard to get most of it out, because you lose more as a percentage.
El-Damak design is unusually efficient for how low a power level she at. ne of the things that most notable about it is that it really a fairly complete system,
he adds. t really kind of a full system-on-a chip for power management. And that makes it a little more complicated
a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature.
So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy. m
#Breakthrough Technique Accurately Detects the andednessof Molecules A new technique that can determine whether a molecule is present in a left
-or right-handed form may have a multitude of practical applications, potentially leading to new and improved drugs, diagnosis methods, and pesticides.
Scientists have demonstrated for the first time the ability to rapidly, reliably and simultaneously identify the andednessof different molecules in a mixture.
The research, led by chemists at The University of Nottingham and the VU University Amsterdam, and published in the academic journal Nature Communications,
The breakthrough could be important in developing effective molecules for use in a wide range of industries everything from the development of safer new drugs and disease diagnosis to less toxic pesticides.
It is common for these so-called chiral molecules to exist in just one form in biological systems,
For example, although both forms of amino acid molecules the building blocks of life itself can be made in the laboratory,
The chirality of these biomolecules also strongly affects the way in which they interact with other molecules,
The chemistry of life Dr Ivan Powis, Professor of Chemical Physics in the University School of Chemistry, who led the research,
t similar with things like sugars and for much bigger macromolecules such as DNA. People will be familiar with the double helix
for instance the well-known malformation of the limbs of infants of pregnant women taking the Thalidomide drug to relieve morning sickness that occurred around 1960.
Mass-Selected Photoelectron Circular Dichroism (MS-PECD) uses circularly polarised light produced by a laser to ionise the molecules using a couple of photons to knock an electron out of the chiral molecule to leave a positively charged ion behind.
and electron those reaching the detectors simultaneously are very likely to have come from the same molecule.
and the technique is much more detailed by looking at energies involved scientists can see many other things about the molecule,
In addition to the development of effective new drugs and diagnosis methods for diseases including cancer, it could potentially lead to new reenpesticides using pheromones tailored specifically to attract pollinators
and trees when under stress and detectors to identify concentrations in air samples could be used to monitor our changing ecology.
While in the food industry, the technique could allow companies to refine the flavours of the food
was funded by the Division of Chemical sciences of The netherlands Organisation for Scientific research, with further European support from LASERLAB-EUROPE and the Marie Curie Initial Training Network ICONIC t
re-emitting the energy as infrared light, and thus they both constrain what astronomers can see
and control much of the energy balance in the interstellar medium. Not least, in the early stages of a star evolution the dust can coagulate into large clumps the first step towards forming planets.
These two molecules are thought to be the most abundant silicon-carbon species in the dust-forming part of the stellar environment,
and dust carriers of Sic bonds, Apj Letters, 2015; 806 L3 doi: 10.1088/2041-8205/806/1/L3 Source:
and still be deciphered accurately by a receiver. This advance has the potential to increase the data transmission rates for the fiber optic cables that serve as the backbone of the internet, cable wireless and landline networks.
The research is published in the June 26 issue of the journal Science. The new study presents a solution to a longstanding roadblock to increasing data transmission rates in optical fiber:
beyond a threshold power level, additional power increases irreparably distort the information traveling in the fiber optic cable. oday fiber optic systems are a little like quicksand.
which in turn extends how far signals can travel in optical fiber without needing a repeater, said Nikola Alic, a research scientist from the Qualcomm Institute, the corresponding author on the Science paper and a principal of the experimental effort.
In lab experiments the researchers at UC San diego successfully deciphered information after it traveled a record-breaking 12,000 kilometers through fiber optic cables with standard amplifiers and no repeaters,
which are electronic regenerators. The new findings effectively eliminate the need for electronic regenerators placed periodically along the fiber link.
These regenerators are effectively supercomputers and must be applied to each channel in the transmission. The electronic regeneration in modern lightwave transmission that carries between 80 to 200 channels also dictates the cost and,
more importantly, prevents the construction of a transparent optical network. As a result, eliminating periodic electronic regeneration will drastically change the economy of the network infrastructure
ultimately leading to cheaper and more efficient transmission of information. The breakthrough in this study relies on wideband requency combsthat the researchers developed.
The frequency comb described in this paper ensures that the signal distortions called the rosstalkthat arises between bundled streams of information traveling long distances through the optical fiber are predictable,
and therefore, reversible at the receiving end of the fiber. rosstalk between communication channels within a fiber optic cable obeys fixed physical laws.
In this study, we present a method for leveraging the crosstalk to remove the power barrier for optical fiber
a professor in the Department of Electrical and Computer engineering at UC San diego and the senior author on the Science paper. ur approach conditions the information before it is sent even,
so the receiver is caused free of crosstalk by the Kerr effect. The photonics experiments were performed at UC San diego Qualcomm Institute by researchers from the Photonics Systems Group led by Radic.
Pitch Perfect Data transmission The UC San diego researchersapproach is akin to a concert master who tunes multiple instruments in an orchestra to the same pitch at the beginning of a concert.
In an optical fiber information is transmitted through multiple communication channels that operate at different frequencies. The electrical engineers used their frequency comb to synchronize the frequency variations of the different streams of optical information,
called the ptical carrierspropagating through an optical fiber. This approach compensates in advance for the crosstalk that occurs between the multiple communication channels within the same optical fiber.
The frequency comb also ensures that the crosstalk between the communication channels is reversible. fter increasing the power of the optical signals we sent by 20 fold,
we could still restore the original information when we used frequency combs at the outset,
said UC San diego electrical engineering Ph d. student Eduardo Temprana, the first author on the paper. The frequency comb ensured that the system did not accumulate the random distortions that make it impossible to reassemble the original content at the receiver.
The laboratory experiments involved setups with both three and five optical channels, which interact with each other within the silica fiber optic cables.
The researchers note that this approach could be used in systems with far more communication channels. Most of today fiber optic cables include more than 32 of these channels,
which all interact with one another. In the Science paper the researchers describe their frequency referencing approach to pre-compensate for nonlinear effects that occur between communication channels within the fiber optic cable.
when it is sent through the optical fiber. With the frequency comb, the information can be unscrambled and fully restored at the receiving end of the optical fiber. e are preempting the distortion effects that will happen in the optical fiber,
said Bill Kuo, a research scientist at the Qualcomm Institute, who was responsible for the comb development in the group.
The same research group published a theoretical paper last year outlining the fact that the experimental results they are now publishing were theoretically possible.
The authors thank Sumitomo Electric Industries for fibers used in the experiments, and Google Inc. for support of this work through a Google research grant.
The University of California has filed a patent on the method and applications of frequency-referenced carriers for compensation of nonlinear impairments in transmission.
Publication: E. Temprana, et al. vercoming Kerr-induced capacity limit in optical fiber transmission, Science 26 june 2015:
Vol. 348 no. 6242 pp. 1445-1448; DOI: 10.1126/science. aab178
#MIT Chemists Develop a Quantum dot Spectrometer Researchers from MIT have designed a quantum dot spectrometer that is small enough to function within a smartphone, enabling portable light analysis. Instruments that measure the properties of light,
known as spectrometers, are used widely in physical, chemical, and biological research. These devices are usually too large to be portable,
but MIT scientists have shown now they can create spectrometers small enough to fit inside a smartphone camera,
using tiny semiconductor nanoparticles called quantum dots. Such devices could be used to diagnose diseases, especially skin conditions,
or to detect environmental pollutants and food conditions, says Jie Bao, a former MIT postdoc and the lead author of a paper describing the quantum dot spectrometers in the July 2 issue of Nature.
This work also represents a new application for quantum dots, which have been used primarily for labeling cells and biological molecules,
as well as in computer and television screens. sing quantum dots for spectrometers is such a straightforward application compared to everything else that wee tried to do,
and I think that very appealing, says Moungi Bawendi, the Lester Wolfe Professor of Chemistry at MIT and the paper senior author.
Shrinking spectrometers The earliest spectrometers consisted of prisms that separate light into its constituent wavelengths
while current models use optical equipment such as diffraction gratings to achieve the same effect. Spectrometers are used in a wide variety of applications,
such as studying atomic processes and energy levels in physics, or analyzing tissue samples for biomedical research and diagnostics.
Replacing that bulky optical equipment with quantum dots allowed the MIT team to shrink spectrometers to about the size of a U s. quarter,
and to take advantage of some of the inherent useful properties of quantum dots. Quantum dots, a type of nanocrystals discovered in the early 1980s, are made by combining metals such as lead
or cadmium with other elements including sulfur, selenium, or arsenic. By controlling the ratio of these starting materials, the temperature,
and the reaction time, scientists can generate a nearly unlimited number of dots with differences in an electronic property known as bandgap,
which determines the wavelengths of light that each dot will absorb. However, most of the existing applications for quantum dots don take advantage of this huge range of light absorbance.
Instead, most applications, such as labeling cells or new types of TV screens, exploit quantum dotsfluorescence a property that is much more difficult to control,
Bawendi says. t very hard to make something that fluoresces very brightly, he says. oue got to protect the dots,
youe got to do all this engineering. Scientists are also working on solar cells based on quantum dots, which rely on the dotsability to convert light into electrons.
However, this phenomenon is understood not well, and is difficult to manipulate. On the other hand, quantum dotsabsorption properties are well known and very stable. f we can rely on these properties,
it is possible to create applications that will have a greater impact in the relative short term,
Broad spectrum The new quantum dot spectrometer deploys hundreds of quantum dot materials that each filter a specific set of wavelengths of light.
The quantum dot filters are printed into a thin film and placed on top of a photodetector such as the charge-coupled devices (CCDS) found in cellphone cameras.
The researchers created an algorithm that analyzes the percentage of photons absorbed by each filter,
then recombines the information from each one to calculate the intensity and wavelength of the original rays of light.
The more quantum dot materials there are, the more wavelengths can be covered and the higher resolution can be obtained.
In this case, the researchers used about 200 types of quantum dots spread over a range of about 300 nanometers.
and Bao showed a beautiful way to exploit the controlled optical absorption of semiconductor quantum dots for miniature spectrometers.
an associate professor of physics at the University of California at Berkeley who was involved not in the research.
which vary greatly in their ability to damage skin. he central component of such spectrometers the quantum dot filter array is fabricated with solution-based processing and printing,
The research was funded by MIT Institute for Soldier Nanotechnologies. Publication: Jie Bao & Moungi G. Bawendi, colloidal quantum dot spectrometer, Nature 523,670 (02 july 2015;
doi: 10.1038/nature1457 e
#New Technique Uses Regenerative Capacity of Stem Cells to Eliminate HIV Scientists at UCLA have developed a new technique that harnesses the regenerative capacity of stem cells to generate an immune response to HIV,
Scientists at the UCLA Eli and Edythe Broad Center of Regenerative medicine and Stem Cell Research are one step closer to engineering a tool that could one day arm the body immune system to fight HIV and win.
The new technique harnesses the regenerative capacity of stem cells to generate an immune response to the virus. The findings were published today in the journal Molecular Therapy. e hope this approach could one day allow HIV-positive individuals to reduce
said Scott Kitchen, the study lead author and a member of the Broad Stem Cell Research center. e also think this approach could possibly be extended to other diseases.
Kitchen also is a member of the UCLA AIDS Institute and an associate professor of medicine in the division of hematology and oncology at the David Geffen School of medicine at UCLA. Kitchen and his colleagues were the first to report the use of an engineered molecule called a chimeric antigen receptor,
or CAR, in blood-forming stem cells. Blood-forming stem cells are capable of turning into any type of blood cell,
including T cells, the white blood cells that are central to the immune system. In a healthy immune system, T cells can usually rid the body of viral or bacterial infection.
But HIV is too strong and mutates too rapidly for T cells to fight against the virus. The researchers inserted a gene for a CAR into blood-forming stem cells in the lab. The CAR,
which is a two-part receptor that recognizes an antigen, was engineered to be carried by T cells
and direct them to locate and kill HIV-infected cells. The CAR-modified blood stem cells were transplanted then into HIV-infected mice that had been engineered genetically with human immune systems.
As a result, HIV infection causes disease similar to that in humans. The researchers found that the CAR-carrying blood stem cells successfully turned into functional T cells that could kill HIV-infected cells in the mice.
The result was a decrease in HIV levels of 80 to 95 percent. The findings strongly suggest that stem cell-based gene therapy with a CAR may be a feasible and effective treatment for chronic HIV infection in humans.
The world leading infectious killer, HIV has caused approximately 40 million deaths worldwide since it was identified first in the early 1980s.
Once HIV invades the body, it targets the very immune cells that are working against it,
using the machinery of T cells to make copies of itself to spread through the body.
This kills the T cells and weakens the immune system so much that the body can fight even a simple infection.
and millions more at risk of infection, do not have adequate access to prevention and treatment,
and there is still no practical cure, said Jerome Zack, professor of medicine and of microbiology,
immunology and molecular genetics in the UCLA David Geffen School of medicine and a co-author of the study. ith the CAR approach,
we aim to change that. Zack is co-director of the UCLA AIDS Institute and is affiliated with UCLA Jonsson Comprehensive Cancer Center and a member of the Broad Stem Cell Research center.
Previous studies by Kitchen and Zack demonstrated similar results with other T cell receptors, although it is known that HIV could mutate away from those receptors.
Another shortcoming of T cell receptors used in previous clinical studies was that they could not be used universally in patients
Kitchen said the CAR approach is more flexible and potentially more effective because it could theoretically be employed in anyone.
The study first author was Anjie Zhen, a postdoctoral fellow at UCLA in the Division of Hematology/Oncology, the UCLA AIDS Institute and the Broad Stem Cell Research center.
IV-specific Immunity Derived From Chimeric Antigen Receptor-engineered Stem Cells, Molecular Therapy,(8 june 2015;
#Niobium Nanowire Yarns Make High-performance Supercapacitors Using yarns made from niobium nanowire, researchers at MIT have developed a new approach to making supercapacitors.
Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough power to transmit data.
Now, researchers at MIT and in Canada have found a promising new approach to delivering the short
but intense bursts of power needed by such small devices. The key is a new approach to making supercapacitors devices that can store
and release electrical power in such bursts, which are needed for brief transmissions of data from wearable devices such as heart-rate monitors, computers,
or smartphones, the researchers say. They may also be useful for other applications where high power is needed in small volumes
such as autonomous microrobots. The new approach uses yarns, made from nanowires of the element niobium,
as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between).
The concept is described in a paper in the journal ACS Applied materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili,
and three others at the University of British columbia. Nanotechnology researchers have been working to increase the performance of supercapacitors for the past decade.
Among nanomaterials, carbon-based nanoparticles such as carbon nanotubes and graphene have shown promising results, but they suffer from relatively low electrical conductivity,
Mirvakili says. In this new work, he and his colleagues have shown that desirable characteristics for such devices,
such as high power density, are not unique to carbon-based nanoparticles, and that niobium nanowire yarn is a promising alternative. magine youe got some kind of wearable health-monitoring system,
Hunter says, nd it needs to broadcast data, for example using Wi-fi, over a long distance. At the moment, the coin-sized batteries used in many small electronic devices have limited very ability to deliver a lot of power at once,
which is what such data transmissions need. ong-distance Wi-fi requires a fair amount of power,
says Hunter, the George N. Hatsopoulos Professor in Thermodynamics in MIT Department of Mechanical engineering, ut it may not be needed for very long.
Small batteries are suited generally poorly for such power needs, he adds. e know it a problem experienced by a number of companies in the health-monitoring
or exercise-monitoring space. So an alternative is to go to a combination of a battery and a capacitor,
Hunter says: the battery for long-term, low-power functions, and the capacitor for short bursts of high power.
Such a combination should be able to either increase the range of the device, or perhaps more important in the marketplace to significantly reduce size requirements.
The new nanowire-based supercapacitor exceeds the performance of existing batteries, while occupying a very small volume. f youe got an Apple Watch and
I shave 30 percent off the mass, you may not even notice, Hunter says. ut if you reduce the volume by 30 percent,
that would be a big deal, he says: Consumers are very sensitive to the size of wearable devices.
The innovation is especially significant for small devices, Hunter says, because other energy storage technologies such as fuel cells, batteries,
and flywheels tend to be less efficient, or simply too complex to be reduced practical when to very small sizes. e are in a sweet spot,
he says, with a technology that can deliver big bursts of power from a very small device.
Ideally, Hunter says, it would be desirable to have a high volumetric power density (the amount of power stored in a given volume) and high volumetric energy density (the amount of energy in a given volume).
obody figured out how to do that, he says. However, with the new device, e have fairly high volumetric power density, medium energy density,
and a low cost, a combination that could be well suited for many applications. Niobium is a fairly abundant
and widely used material, Mirvakili says, so the whole system should be inexpensive and easy to produce. he fabrication cost is cheap,
he says. Other groups have made similar supercapacitors using carbon nanotubes or other materials, but the niobium yarns are stronger and 100 times more conductive.
Overall, niobium-based supercapacitors can store up to five times as much power in a given volume as carbon nanotube versions.
Niobium also has a very high melting point nearly 2 500 degrees Celsius so devices made from these nanowires could potentially be suitable for use in high-temperature applications.
In addition, the material is highly flexible and could be woven into fabrics, enabling wearable forms; individual niobium nanowires are just 140 nanometers in diameter 140 billionths of a meter across,
or about one-thousandth the width of a human hair. So far, the material has been produced only in lab-scale devices.
The next step, already under way, is to figure out how to design a practical, easily manufactured version,
the researchers say. he work is very significant in the development of smart fabrics and future wearable technologies, says Geoff Spinks, a professor of engineering at the University of Wollongong, in Australia,
who was associated not with this research. This paper he adds, onvincingly demonstrates the impressive performance of niobium-based fiber supercapacitors.
The team also included Phd student Mehr Negar Mirvakili and professors Peter Englezos and John Madden, all from the University of British columbia s
Overtext Web Module V3.0 Alpha
Copyright Semantic-Knowledge, 1994-2011