Tiny implantable fuel cell harvests energy from the brain

This silicon wafer consists of glucose fuel cells of varying sizes; the largest is 64 by 64 mm

A new implantable fuel cell that harvests the electrical power from the brain promises to usher in a new generation of bionic implants. Designed by MIT researchers, it uses glucose within the cerebrospinal fluid surrounding the brain to generate several hundred microwatts of power without causing any detrimental effects to the body. The technology may one day provide a whole new level of reliability and self-efficiency for all sorts of implantable brain-machine interfaces that would otherwise have to rely on external power sources.

So far, two computer chip-shaped fuel cells have been tested in a saline solution simulating the cerebrospinal fluid. The prototypes come in one square millimeter and two square millimeter varieties. They work by oxidizing glucose present in the cerebrospinal fluid at the surface of an activated platinum anode and then converting the oxygen into water at the cathode end of the cell, where single-walled carbon nanotubes are embedded. Electrons stripped from the glucose in the process are used to generate electricity.

One of the advantages of a fuel cell over a battery is that it can operate indefinitely provided an uninterrupted supply of fuel and oxygen. The new tiny fuel cell could potentially operate continuously for decades. Current brain-machine interfaces, on the other hand, are either powered wirelessly, through electrical induction, or by disposable batteries that need to be surgically replaced after several years.

Although not yet tested in an actual brain, a lot has been done to gauge the fuel cell’s safety. It turned out that it consumes glucose at 2.8 to 28 percent of the rate at which the simple sugar is replenished by the organism, so no adverse effects should be caused. Similarly, the calculated levels of oxygen consumption have been shown to be low enough not to shift the oxygen balance in the brain. Since it’s said to be the first-ever attempt at using the cerebrospinal fluid as the fuel medium for an implantable fuel cell, the scientists are exploring a completely new field ... one that has so far proved very promising.

Rahul Sarpeshkar, an associate professor of electrical engineering and computer science at MIT and leader of the team behind the project, is already preparing for tests on animals, and then on humans. Should the results confirm that the full cells cause no detrimental effect to the organism, it will be possible to manufacture them together with integrated circuits on a single silicon wafer. Implants powered by this technology may one day help tackle blindness, paralysis and various deep brain disorders.

Source: MIT

"Nanoscale sandwich" technique could mean thinner, cheaper solar cells

Using what they call the 'nanoscale sandwich' technique, researchers have created ultra-thin solar cells that are just as efficient as conventional thicker ones 

We certainly hear a lot about solar cells that are able to convert larger and larger percentages of the sun’s energy into electricity. That’s all very well and good, but if those more-efficient solar cells are too expensive, they will still ultimately prove impractical for everyday use. Researchers from North Carolina State University, however, have found a way of creating “ultra-thin” solar cells that should create just as much electricity as their thicker siblings, but at a lower cost.

The new cells are made using what is called a “nanoscale sandwich” design. The process starts with a pattern being laid down on a transparent dielectric substrate, using regular lithography techniques. That pattern forms the substrate into tiny structures measuring between 200 and 300 nanometers in height – when viewed in cross-section, they resemble the crenelations along the top of a medieval castle.

Next, a very thin layer of the active material is deposited onto the altered substrate. This “active layer” is what actually converts the solar energy into electricity. Finally, on top of that layer, another layer of the dielectric material is deposited. This results in a dielectric/active material/dielectric sandwich.

The crenelated shape of this sandwich allows the two dielectric layers to serve as highly-efficient optical antennas, focusing the solar energy onto the layer of active material – this means that less of that material can be used, without a loss in performance.

“We created a solar cell with an active layer of amorphous silicon that is only 70 nanometers (nm) thick,” said Dr. Linyou Cao, co-author of a paper on the research. “This is a significant improvement, because typical thin-film solar cells currently on the market that also use amorphous silicon have active layers between 300 and 500 nm thick.”

He added that the same technique could be used to create solar cells incorporating other active materials, such as cadmium telluride, copper indium gallium selenide, and organic materials.

His paper was recently published in the journal Nano Letters.

MIT researchers develop all-carbon solar cell

An atomic-force microscope image of a layer of single-walled carbon nanotubes deposited on a silicon surface, which is the first step in manufacturing the new solar cell

Researchers at MIT have developed a new type of photovoltaic cell made with carbon nanotubes that captures solar energy in the near-infrared region of the spectrum, which conventional silicon solar cells don’t. The new design means solar cell efficiency could be greatly increased, boosting the chances to make solar power a more popular source of energy.

The new solar cell developed at MIT is a consequence of recent advances in the large-scale production of carbon nanotubes. It also features another type of carbon, a fullerene known as C60 (aka Buckminsterfullerene). The nanotubes have to be very pure, single-walled and of the same symmetrical configuration. The material is transparent to visible light and has to be overlaid on conventional silicon cells to form a hybrid cell that could, in theory, capture most of the energy contained in the sunlight it captures.

This is not the first time researchers have used carbon nanotubes to make solar cells, but researcher Michael Strano and his team found that the new all-carbon cells appear to be stable in air, therefore they did not require a layer of polymer to hold the nanotubes together in position. This characteristic eliminates a stage in the production process that hitherto has made it more complex. The cells require relatively small amounts of highly purified carbon, resulting in a lighter end product.

There are several bright, optimistic spots in this research, the scientists say. Although the proof of concept devices have so far achieved an efficiency of only 0.1 percent, the researchers have already identified some of the sources of inefficiency. For instance, they have noticed that homogenous mixtures of carbon nanotubes are more efficient than heterogeneous ones. Mixing single-walled and multiwalled nanotubes is not a good idea, either.

The scientists are positive they are bound to make high-efficiency near-infrared solar cells, and point out that even a low-efficiency cell that works in that region, capturing energy that current cells waste, would be worthwhile provided costs are low. They are now looking into ways to better control the shape and thickness of the layers of the material.

A paper written by Professor Strano describing the all-carbon solar cell in detail was recently published in the journal Advanced Materials.

German researchers developing higher-efficiency organic solar cells

A flexible organic solar module developed by researchers at the Karlsruhe Institute of Technology

The Karlsruhe Institute of Technology, through its Light Technology Institute, this month will initiate new research on printable organic solar cells. The four-year project aims at increasing the efficiency of such cells to more than 10 percent. These promising, cheaper solar cells can be manufactured using existing techniques such as screen printing and continuous roll-to-roll processes. So far, however, low efficiency rates have stood between these cells and the market.

The methodology the KIT researchers are going to use is based on a tandem architecture, which involves combining multiple solar cells that offer complementary levels of light absorption. They stack two solar cells directly on top of each other and together they can harvest more sunlight and, consequently, achieve better efficiency rates.

Organic solar cells are also known as plastic solar cells. They are light, flexible, semi-transparent, more environmentally-friendly than other types of cells, and offer a quicker return on investment. Such characteristics open up possibilities for exciting new applications, especially in architecture, where the cells could be integrated into the design of buildings. Other areas offering potential for the technology include the manufacturing of automotive parts and consumer goods.

The research will also look into new materials, as well as ways to improve the cells’ stability. All testing will be done in real-life contexts, including manufacturing processes, which will be done in an industry-compatible production environment in order to improve chances of commercially-applicable results.

KIT researchers are not the only ones working to improve organic solar cell efficiency, but if they achieve their desired goal, this type of solar cell could get closer to becoming competitive with standard, non-organic silicon models.

The research has been made possible with €4.25 million (US$5.32 million) in funding from the German Federal Ministry of Education and Research.

Source: Karlsruhe Institute of Technology

Scientists create artificial vascular networks using sugar

The RepRap printer, using molten sugar to create the vascular network's mold and filaments

For a great number of people, the idea of being able to use a patient’s own cells to create lab-grown replacement organs is very appealing. Already, researchers have had success growing urethras (which are essentially hollow tubes), and miniature human livers. Before large, solid, three-dimensional organs can be grown, however, scientists must figure out a reliable way of incorporating blood vessels into them – if the lab-grown organs simply take the form of a block of cells, the cells on the inside won’t be able to receive any nutrients, and will die. Now, a team from the University of Pennsylvania and MIT has devised a way of building such vessels, using sugar.

The scientists use a relatively inexpensive open-source RepRap 3D printer, which extrudes molten sugar – a mixture of sucrose, glucose and dextran is used, as that formulation offers strength (once the sugar hardens), plus biocompatibility with a wide range of cell types. That sugar is used to create a three-dimensional solid-sided mold that has a network of thin filaments of sugar running back and forth within it, from one side of its interior to the other. Those filaments are coated with a thin layer of a corn-derived polymer.

A water-based gel containing organ cells is then poured into the mold, flowing around the filaments. The polymer on the filaments reacts with the gel as it’s solidifying, causing the filaments to dissolve. As the liquified sugar is flushed out of the gel, tiny tunnels in the shape of the filaments are left behind. Nutrient-rich fluids can then be pumped through those vessels, delivering nutrients to cells throughout the gel block.

A microscope image of one of the 3D-printed vascular network templates

When human blood vessel cells were injected into the artificial vascular networks, capillaries spontaneously began sprouting off of the main vessels into the surrounding gel – just like a natural vascular network grows. When liver cells were used in the gel, their production of albumin and urea increased as the nutrient fluid was introduced. Albumin and urea are found naturally in blood and urine (respectively), and their presence is an indicator of proper liver cell function. Additionally, the cells located closest to the vessels showed the highest rate of survival.

While the technology has great promise, the concentration of liver cells in the gel will need to be increased dramatically before an actual replacement liver could be produced. “The therapeutic window for human-liver therapy is estimated at one to 10 billion functional liver cells,” said MIT’s Sangeeta N. Bhatia, one of the team leaders. “With this work, we've brought engineered liver tissues orders of magnitude closer to that goal, but at tens of millions of liver cells per gel we've still got a ways to go.”

He added that they also have to determine how to attach their engineered vascular networks to those already existing within the body.

Another approach to creating lab-grown organs, known as 3D bioprinting, involves depositing two-dimensional layers of cell-containing gel one on top of the other, building these layers up into three-dimensional organs. Although vascular networks can be built into these organs, the vessels end up with structural seams running through them, which can fail under the pressure of circulating fluid. Also, certain types of cells (including liver cells) cannot survive the 3D bioprinting process.

A paper on the research was recently published in the journal Nature Materials. More information is available in the video below.

Source: University of Pennsylvania

Electrically conductive gel holds promise for biological sensors and energy storage devices

Postdoctoral fellow Guihua Yu, Associate Professor Zhenan Bao and visiting scholar Lijia Pan examine the printable, electrically conductive hydrogel

Researchers at Stanford University have created an electrically conductive gel that feels and behaves like biological tissues, but conducts electricity like a metal or semiconductor. The gel can also be printed or sprayed as a liquid before being turned into a gel. The researchers say this combination of characteristics gives the gel enormous promise for developing new biological sensors and energy storage devices.

The jelly-like material was created by Stanford chemical engineering Associate Professor Zhenan Bao, science and engineering Associate Professor Yi Cui and members of their respective labs by binding long chains of the organic compound aniline together using phytic acid, a substance that is the principal storage form of phosphorous in many plant tissues. The acid’s ability to grab up to six polymer chains at once allows an extensively cross-linked network to form.

Unlike commercially available conducting polymers that form a uniform film without any nanostructures, the new gel’s cross-linking produces a complex, sponge-like structure. Innumerable tiny pores expand the gel’s surface area, increasing the amount of charge it can hold, the rapidity of its electrical response, and its ability to sense chemicals.

And because the material doesn’t solidify until the final step of its creation, it can be easily manipulated. By printing or spraying the material as a liquid, manufacturers could construct intricately patterned electrodes at low cost, before turning it into a gel.

In contrast to most hydrogels, which are tied together by a large number of insulating molecules that reduce the material’s overall ability to conduct electrical current, the new hydrogel is highly conductive because phytic acid is a “small-molecule dopant” that lends polymer chains a charge when it links them.

Cui says the gel’s conductance is “among the best you can get through this kind of process,” with a high capacity to hold a charge and the ability to respond unusually quickly to an applied charge. The researchers say that, with these electrical capabilities, combined with the material’s similarity to biological tissue and large surface area, it is well suited to the creation of devices that communicate between biological and technological hardware. These could include medical probes and laboratory sensors, as well as biofuel cells and high-energy density capacitors.

Perhaps most importantly, the gel is cheap and easy to produce. “All it’s made of are commercially available ingredients thrown into a water solution,” said Bao.

The team’s research appears in the journal Proceedings of the National Academy of Sciences (PNAS).

Source: Stanford University

Self-fueled work station concept generates energy while you sit

Unplugged is a prototype of an office work station that powers devices via energy that is collected off the human body

Unplugged is an office work station of the future concept that envisions powering your electronic devices via energy collected off the human body. The prototype was created by Swedish designer Eddi Törnberg as part of his final year thesis at Beckmans College of Design, in Stockholm, and you will be pleased to know that it doesn’t mean you'd be required to pedal away while you work. In fact all you would have to do is move about your office as normal, sit in your chair and let the heat of your body do the rest.

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Incorporating three different modes of self-sustaining energy, this future office would see energy generated from the movement of a person walking across carpet, from the body heat of sitting in a chair and from the process of photosynthesis that occurs in plants.

The office carpet would incorporate piezo-electric elements that have been woven into the fabric. When someone walks over the carpet square or rolls the office chair back and forth, energy can be then collected and put to use. Meanwhile the plant in the corner is not just for aesthetics or clean air - similar to the Moss Table prototype which was developed by designers and scientists at the University of Cambridge, Unplugged draws energy from the plant’s natural process of photosynthesis.

Finally a thermoelectric office chair would convert temperatures into an electric current using the heat of the human body. Naturally the seat warms up when you sit in it while the base metal elements remains cold and it is the difference between these two temperatures that allows an energy current to be generated.

While it is unlikely that Törnberg's prototype can actually generate enough energy to power a laptop (or even a desk lamp) the idea gives us food for thought as energy-harvesting technology evolves along with low-energy consumption electronic devices .

Source: Eddi Törnberg via The Atlantic Cities

Scientists capture the shadow cast by a single atom

Image of the shadow of a single ytterbium atom

A team of researchers at Griffith University has managed to stretch the capabilities of microscopy to its ultimate limit. Culminating a five-years effort, the scientists have obtained a digital image of the shadow cast by a single atom, in a development that might soon lead to important advances in scientific observations ranging from the very big to the very small.

Holding an atom in place long enough to take its picture has been within our technological grasp for some time. This is done by isolating the atom inside a chamber and holding it still through electrical forces, a method known as a radiofrequency Paul Trap (named after Wolfgang Paul, who shared the Nobel Prize in Physics in 1989 for this work).

The researchers trapped single ytterbium ions using this technique and exposed them to a very specific frequency of laser light. Under this light, the atom's shadow was cast onto a detector and then captured by a digital camera. This was possible because of a super high-resolution microscope, which makes the shadow dark enough to see. No other facility in the world sports a resolution high enough to allow for such an extreme feat.

The process requires extreme precision, as changing the frequency of the light illuminating the atom by just one part in a billion is already enough to make the shadow disappear.

"Atoms only respond to very specific light frequencies, and these frequencies are different for each element. The very fine frequency control that we use is a fairly standard feature of modern atomic physics experiments," Professor Kielpinski, who led the research efforts, told Gizmag. The breakthrough pushes microscopy to its ultimate limit because, as Kielpinksi explained, it is impossible to see anything smaller than an atom using visible light.

But the researchers' ultimate goal wasn't just to take a simple picture. Absorption imaging plays a fundamental role in modern scientific research, from astronomical observations of dust clouds to biomicroscopy. Measuring how much light a single atom can absorb is crucial to understanding exactly how far scientists can stretch the limits of this imaging technique.

Using their results, the researchers can now predict how much light an atom should absorb when forming a shadow, measure whether the microscope is achieving maximum contrast, and adjust their parameters accordingly to achieve the best possible image quality without damaging the samples. This is important because an excessive amount of X-rays or UV light could damage fragile biological samples, such as DNA strands.

A paper describing the results was published on the scientific journal Nature Communications.

Source: Griffith University

Synthetic protein kick-starts the immune system to prevent all strains of the flu

The synthetic protein EP67 acts on the immune system to attack the influenza virus (Colorized influenza A virus pictured) before it is detected

We’ve seen promising moves towards developing a universal or near-universalinfluenza vaccine, but researchers at the Donald P. Shiley BioScience Center have taken a different tack to ward of the crafty virus. Although the flu virus actively keeps the immune system from detecting it for a few days, giving it time to gain a foothold, the researchers have found that a powerful synthetic protein, known as EP67, can kick start the immune system so that it reacts almost immediately to all strains of the virus.

Previously, EP67 had primarily been used to help activate the immune response by being added to a vaccine. But Joy Phillips, Ph.D from San Diego State University and her colleague Sam Sanderson Ph.D. from the University of Nebraska Medical Center, saw potential for the protein to work on its own.

Because EP67 acts on the immune system rather than the virus itself, it functions the same regardless of the flu strain. Compare this to the flu vaccine that needs to be tailored to match the currently circulating strain.

“When you find out you’ve been exposed to the flu, the only treatments available now target the virus directly but they are not reliable and often the virus develops a resistance against them,” Phillips said. “EP67 could potentially be a therapeutic that someone would take when they know they’ve been exposed that would help the body fight off the virus before you get sick.”

Phillips adds that EP67 could also be used in the event of a new strain of infectious disease, before the pathogen has even been identified, citing SARS or the 2009 H1N1 influenza outbreak as previous examples where the protein may have proven useful.

Testing EP67 on mice infected with the flu virus, the researchers found that those given a dose of EP67 within 24 hours of infection didn’t get sick – or as sick – as those that weren’t treated with EP67. With the level of illness in mice measured by weight loss, mice infected with the flu typically lose 20 percent of their body weight, while those treated with EP67 lost an average of just six percent. More importantly, Phillips said, the mice treated a day after being infected with a lethal dose of influenza didn’t die.

Since EP67 is active in animals, including birds, the researchers say their research also has huge implications for veterinary applications.

The team plans to also examine the effect EP67 has in the presence of a number of other pathogens and will take a closer look at how exactly the synthetic protein functions within different cells in the body.

The researcher’s study is published in the Public Library of Science journal PLoS ONE.

Triboelectric generator could allow electricity-generating touchscreens

The pyramid patterns created in a polymer sheet increase current production in the new triboelectric generator 

Researchers at the Georgia Institute of Technology have taken advantage of the triboelectric effect, which sees an electric charge generated through friction between two different materials, to develop a generator that could supplement power produced by piezoelectric nanogenerators previously developed at Georgia Tech. The triboelectric generator could be used to produce electricity from activities such as walking and even has the potential to create touchscreens that generate their own power.

“The fact that an electric charge can be produced through this [triboelectric] principle is well known,” said Zhong Lin Wang, a Regents professor in the School of Materials Science & Engineering at the Georgia Institute of Technology. “What we have introduced is a gap separation technique that produces a voltage drop, which leads to a current flow, allowing the charge to be used. This generator can convert random mechanical energy from our environment into electric energy.”

The team’s triboelectric generator generates a charge when a sheet of polyester, which tends to donate electrons, rubs against a sheet of polydimethylsiloxane (PDMS), which accepts electrons. Immediately after the two polymer surfaces rub together, they are mechanically separated, creating an air gap that isolates the charge on the PDMS surface and forms a separation of the positive and negative charges (known as a diploe moment).

Connecting an electrical load between the two surfaces will result in the flow of a small electric current to equalize the charge potential. Therefore, by continuously rubbing the surfaces together and then quickly separating them, the generator can produce a small alternating current. An external deformation is used to press the surfaces together and slide them to create the rubbing motion.

“For this to work, you have to use to two different kinds of materials to create the different electrodes,” Wang explained. “If you rub together surfaces made from the same material, you don’t get the charge differential.”

The researchers say the technique could be used to create a very sensitive self-powered active pressure sensor for potential use with organic electronic or opto-electronic systems. Since the sensors can detect pressure as low as around 13 millipascals, they would be sensitive enough to produce a small current that can be detected to indicate contact from something as small as a feather or water droplet touching the surface of the triboelectric generator.

Additionally, because the devices can be made around 75 percent transparent, there is the potential for the technology to be used in touch screens to replace existing sensors. “Transparent generators can be fabricated on virtually any surface,” said Wang. “This technique could be used to create very sensitive transparent sensors that would not require power from a device’s battery.”

Although rubbing smooth surfaces together will generate a charge, Wang and his team have managed to increase the current by using micro-patterned surfaces. After testing line, cube and pyramid surface patterning, they found that surfaces patterned with pyramids generated the most electrical current: as much as 18 volts at about 0.13 microamps per square centimeter.

This enhanced generating capacity of the pyramid-patterned surface was due to the air voids created between the patterns improving the capacitance change and facilitating charge separation.

The team fabricated the triboelectric generators by first creating a mold from a silicon wafer, onto which the friction-enhancing patterns were formed in recess using traditional photolithography and either a wet or dry etching process. The molds were then treated with a chemical to prevent the PDMS from sticking.

The liquid PDMS elastomer and cross-linker were then mixed and spin-coated onto the mold, and peeled off as a thin film after thermal curing. The resulting PDMS film, complete with surface patterning, was then fixed onto an electrode surface made of indium tin oxide (ITO) coated with polyethylene terephthalate (PET) by a thin PDMS bonding layer. The entire structure was then covered with another ITO-coated PET film to form a sandwich structure.

“The entire preparation process is simple and low cost, making it possible to be scaled up for large scale production and practical applications,” Wang said.

Wang added that the generators are robust, continuing to generate a current even after days of use and after more than 100,000 cycles of operation. The team’s next step is to create systems that include a way to store the current generated.

“Friction is everywhere, so this principle could be used in a lot of applications,” Wang added. “We are combining our earlier nanogenerator and this new triboelectric generator for complementary purposes. The triboelectric generator won’t replace the zinc oxide nanogenerator, but it has its own unique advantages that will allow us to use them in parallel.”

The research was funded by the National Science Foundation, the Department of Energy and the U.S. Air Force. Details of the triboelectric generator are reported in the June issue of the journal Nano Letters.