While you're up, print me a solar cell

The sheet of paper looks like any other document that might have just come spitting out of an office printer, with an array of colored rectangles printed over much of its surface. But then a researcher picks it up, clips a couple of wires to one end, and shines a light on the paper. Instantly an LCD clock display at the other end of the wires starts to display the time.

Almost as cheaply and easily as printing a photo on your inkjet, an inexpensive, simple solar cell has been created on that flimsy sheet, formed from special “inks” deposited on the paper. You can even fold it up to slip into a pocket, then unfold it and watch it generating electricity again in the sunlight.

The new technology, developed by a team of researchers at MIT, is reported in a paper in the journal Advanced Materials, published online July 8. The paper is co-authored by Karen Gleason, the Alexander and I. Michael Kasser Professor of Chemical Engineering; Professor of Electrical Engineering Vladimir Bulović; graduate student Miles Barr; and six other students and postdocs. The work was supported by the Eni-MIT Alliance Solar Frontiers Program and the National Science Foundation.

The technique represents a major departure from the systems used until now to create most solar cells, which require exposing the substrates to potentially damaging conditions, either in the form of liquids or high temperatures. The new printing process uses vapors, not liquids, and temperatures less than 120 degrees Celsius. These “gentle” conditions make it possible to use ordinary untreated paper, cloth or plastic as the substrate on which the solar cells can be printed.

It is, to be sure, a bit more complex than just printing out a term paper. In order to create an array of photovoltaic cells on the paper, five layers of material need to be deposited onto the same sheet of paper in successive passes, using a mask (also made of paper) to form the patterns of cells on the surface. And the process has to take place in a vacuum chamber.

Barr places a sheet of paper with a mask on it into the vapor-printing chamber.Photo: Patrick Gillooly

The basic process is essentially the same as the one used to make the silvery lining in your bag of potato chips: a vapor-deposition process that can be carried out inexpensively on a vast commercial scale.

The resilient solar cells still function even when folded up into a paper airplane. In their paper, the MIT researchers also describe printing a solar cell on a sheet of PET plastic (a thinner version of the material used for soda bottles) and then folding and unfolding it 1,000 times, with no significant loss of performance. By contrast, a commercially produced solar cell on the same material failed after a single folding.

“We have demonstrated quite thoroughly the robustness of this technology,” Bulović says. In addition, because of the low weight of the paper or plastic substrate compared to conventional glass or other materials, “we think we can fabricate scalable solar cells that can reach record-high watts-per-kilogram performance. For solar cells with such properties, a number of technological applications open up,” he says. For example, in remote developing-world locations, weight makes a big difference in how many cells could be delivered in a given load.

Gleason adds, “Often people talk about deposition on a flexible device — but then they don’t flex it, to actually demonstrate” that it can survive the stress. In this case, in addition to the folding tests, the MIT team tried other tests of the device’s robustness. For example, she says, they took a finished paper solar cell and ran it through a laser printer — printing on top of the photovoltaic surface, subjecting it to the high temperature of the toner-fusing step — and demonstrated that it still worked. Test cells the group produced last year still work, demonstrating their long shelf life.

Barr holds a sheet of paper that has had one of the layers of the solar cell printed on its surface. Photo: Patrick Gillooly

In today’s conventional solar cells, the costs of the inactive components — the substrate (usually glass) that supports the active photovoltaic material, the structures to support that substrate, and the installation costs — are typically greater than the cost of the active films of the cells themselves, sometimes twice as much. Being able to print solar cells directly onto inexpensive, easily available materials such as paper or cloth, and then easily fasten that paper to a wall for support, could ultimately make it possible to drastically reduce the costs of solar installations. For example, paper solar cells could be made into window shades or wallpaper — and paper costs one-thousandth as much as glass for a given area, the researchers say.

For outdoor uses, the researchers demonstrated that the paper could be coated with standard lamination materials, to protect it from the elements.

Others have tried to produce solar cells and other electronic components on paper, but the big stumbling block has been paper’s rough, fibrous surface at a microscopic scale. To counter that, past attempts have relied on coating the paper first with some smooth material. But in this research, ordinary, uncoated paper was used — including printer paper, tissue, tracing paper and even newsprint with the printing still on it. All of these worked just fine.

The researchers continue to work on improving the devices. At present, the paper-printed solar cells have an efficiency of about 1 percent, but the team believes this can be increased significantly with further fine-tuning of the materials. But even at the present level, “it’s good enough to power a small electric gizmo,” Bulović says.

Enlarge

A paper solar cell that has been repeatedly folded is illuminated from below and connected to a voltmeter to demonstrate its output (26 V). Image courtesy of the Gleason Lab

“I am very excited by what is being done” by the MIT team, says Peter Harrop, chairman of IDTechEx, which does research on printed electronics. He says that while most researchers have been focusing on large-scale solar installations that could feed into the electric grid, the potential for other applications “is at least as large. Here the key parameters are very different, with disposable consumer goods, wall coverings and other applications with limited life required.”

He adds, “The work at MIT ... is therefore very important. To succeed it must promise low enough cost and low enough sensitivity to humidity.” Other attempts to create printable solar cells have been criticized for failing to meet these criteria, he notes.
This story is republished courtesy of MIT News (http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Provided by Massachusetts Institute of Technology (news : web)

Inspired by teflon, researchers create super durable proteins

More than 50 years ago, NYU-Poly alumni John Gilbert was asked to evaluate a newly- developed material called Teflon. His experiments using the fluorinated polymer as a surface coating for pots and pans helped usher in a revolution in non-stick cookware. Today, NYU-Poly Assistant Professor of Chemical and Biological Sciences Jin Montclare is taking the research theme in a new direction, investigating fluorinated proteins -- a unique class of proteins that may have a wide range of applications from industrial detergents to medical therapeutics.

In a paper published in the current issue of ChemBioChem, Montclare and Peter Baker, who just received his doctoral degree from NYU-Poly, detail their success in creating proteins that are considerably more stable and less prone to denaturation than their natural counterparts. These qualities enable them to retain both their structure and function under high temperatures in which other proteins would simply break down.

Inspired by the ability of fluorinated polymers like Teflon to stabilize surfaces, Montclare and Baker set their sights on developing a process that would allow them to reinforce the interface of proteins, rendering them more resistant to degradation.

“One of the main challenges of proteins—whether they’re in the body or in the lab—is that they are naturally created to function under specific conditions, and to break down under others,” Montclare explained. “A stable protein that was still active and functional under a variety of conditions would open up an extraordinary range of potential for scientists and product developers.”

Through a trick of genetic engineering, the scientists were able to coax a strain of bacteria into taking up amino acids—the building blocks of protein—that were chemically altered by the addition of fluorine. “Nature doesn’t make fluorinated amino acids, but these experiments show that we can create them,” said Montclare. The result was a "fluorinated" protein that can withstand temperatures up to 140 degrees Fahrenheit with no compromise in activity or function.

Next up for Montclare and Baker are experiments to test the limits of their success in creating fluorinated or Teflon-like proteins. They’re hoping that this type of effect can be achieved with a wide range of proteins, especially those used in medicine including some therapeutic cancer drugs. The stable proteins may also some day act as prophylactics to combat exposure to neurotoxic agents (including warfare agents)–something that is of interest to the Department of Defense. The scientists hope to improve the proteins’durability and decrease the need for precise storage conditions, which often include refrigeration to prevent breakdown.

More information: Paper online: http://dx.doi.org/ … ic.201100221

Provided by Polytechnic Institute of New York University

Researchers apply NMR/MRI to microfluidic chromatography

 

By pairing an award-winning remote-detection version of NMR/MRI technology with a unique version of chromatography specifically designed for microfluidic chips, researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have opened the door to a portable system for highly sensitive multi-dimensional chemical analysis that would be impractical if not impossible with conventional technologies.

Alexander Pines, a faculty senior scientist in Berkeley Lab's Materials Sciences Division and the Glenn T. Seaborg Professor of Chemistry at the University of California (UC) Berkeley, is one of the word's foremost authorities on NMR (nuclear magnetic resonance) and its daughter technology, MRI (Magnetic Resonance Imaging). In this latest development, he led a collaboration in which a remote detection NMR/MRI technique that can rapidly identify the chemical constituents of samples in microfluidic "lab-on-a-chip" devices was used to perform analyses in a microscale monolithic chromatograph column.

"We have presented the first demonstration that a monolithic chromatograph column can be used to separate small molecules on a timescale that is compatible with NMR/MRI detection, an important first step to portable chromatographic devices," says Vikram Bajaj, a project scientist in the Pines' group who is the corresponding author of a paper describing this work in the journal Analytical Chemistry.

The Analytical Chemistry paper is titled "Remotely Detected NMR for the Characterization of Flow and Fast Chromatographic Separations Using Organic Polymer Monoliths." Co-authoring the paper with Pines and Bajaj were Thomas Teisseyre, Jiri Urban†, Nicholas Halpern-Manners, Stuart Chambers and Frantisek Svec.

Chromatography is one of the indispensable tools of chemistry. By dissolving sample into a fluid – called the "mobile phase" – and flushing it through a solid medium – called the "stationary phase" - chemists can separate the sample's constituent chemical species - called analytes – for identification and measurement, as well as for purification purposes. Analytes will be separated on the basis of how fast each individual species diffuses through the stationary phase.

"The coupling of our remote NMR/MRI technology with monolithic chromatography columns in a microfluidic chip enables us to obtain high resolution, velocity-encoded images of a mobile phase flowing through the stationary phase," Bajaj says. "Our technique provides both real-time peak detection and chemical shift information for small aromatic molecules, and demonstrates the unique power of magnetic resonance, both direct and remote, in studying chromatographic processes."

The coupling of remote NMR/MRI to chromatography was made possible by the polymer monolithic column, a technology developed by Analytical Chemistry paper co-author Frantisek Svec, a chemist who directs the Organic and Macromolecular Synthesis facility at Berkeley Lab's Molecular Foundry, a DOE nanoscience center. In conventional chromatography, the stationary phase column is typically filled with porous polymer beads or some other discrete medium whose physical or chemical properties modulate the diffusion rates of analytes passing through. In Svec's stationary phase, a chromatography column is filled with a monolithic solid polymer – meaning it is a single, continuous piece - that is perforated throughout with nanoscopic pores.

"Polymer monoliths as a separation media can be compared to a single large particle that does not contain inter-particular voids," Svec says. "As a result, all the mobile phase must pass through the stationary phase as convective flow rather than diffusion during chromatographic processes. This convective flow greatly accelerates the rate of analyte separation."

The remote NMR/MRI technology whose development was led by Pines won a 2011 R&D 100 Award. These awards, known as the "Oscars of Innovation," recognize the year's 100 most significant proven technological advances. Through a combination of remote instrumentation, JPEG-style image compression algorithms and other key enhancements, this remote NMR/MRI technology can zoom in on microscopic objects of interest within a sample flowing through the columns of a microfluidic chip with unprecedented spatial and time resolutions.

"Our remote NMR/MRI technology enables time-resolved imaging of multi-channel flow, dispenses with the need for large and expensive magnets for analysis, allows us to analyze complex and unprocessed mixtures in one pass, and adds portability to NMR/MRI," Bajaj says.

The key to the success of remote NMR/MRI technology is the decoupling of the NMR/MRI signal encoding and detection phases. NMR/MRI signals arise from a property found in the atomic nuclei of almost all molecules called "spin," which makes the nuclei act as if they were bar magnets with poles that point either "north" or "south." Obtaining an NMR/MRI signal from a sample depends upon an excess of nuclear spins pointing in one direction or the other. In a conventional NMR/MRI set-up, in which the signal encoding and detection phases take place within one machine, this require the presence of a powerful external magnetic field. The remote NMR/MRI technology developed by Pines and his group, in which NMR?MRI signal encoding and detection are carried out independently, can detect NMR/MRI signals without the need of such a strong magnet, yet it still provides the same outstanding sensitivity of conventional NMR/MRI.

"With our remote NMR/MRI technology and the polymer monoliths of Frank Svec's group, we were able to look inside optically opaque microfluidic columns and measure the velocity of the flowing fluid during a chromatographic separation," Bajaj says. "We were also able to demonstrate in-line monitoring of chromatographic separations of small molecules at high flow rates."

Results using the remote NMR/MRI technique with the polymer monoliths showed a much better ability to discriminate between different analytes at the molecular level, Bajaj says, than comparable analysis using spectrometry based on either mass or optical properties. This paves the way for multidimensional analysis, in which the result of a chromatographic separation would be encoded into an NMR/MRI signal by charge, size or some other factor and stored. The encoded fluid would then be run through a second separation and those results would also be encoded into an NRM/MRI signal and stored.

"This would allow us to create a multidimensional chromatography experiment that does not require the fluid volume to be physically partitioned," Bajaj says. "The fluid would, quite literally, be partitioned in the magnetic degrees of freedom instead."

Provided by Lawrence Berkeley National Laboratory (news : web)

Fused indolines made by asymmetrical carbon-carbon coupling

Many drugs are based on natural substances. Because it is usually difficult, if not impossible, to isolate these in sufficient quantities from plants or microorganisms, they must be synthesized in the laboratory. This requires linking carbon atoms – with the right spatial orientation (stereochemistry) relative to each other. In the journal Angewandte Chemie, E. Peter Kündig and a team from the University of Geneva (Switzerland) have now introduced a palladium-catalyzed synthesis that allows them to produce indoline derivatives with the correct spatial arrangement.

When synthesizing large, complex organic molecules, it is generally easier to make smaller individual pieces that can then be linked together to make the final product. The award of the 2010 Nobel Prize in chemistry to R. Heck, E. Negishi, and A. Suzuki for their work on palladium-catalyzed cross-coupling indicates the importance of methods for creating bonds between carbon atoms.

Another complication in the synthesis of natural products is that molecules with identical atomic compositions can have different spatial arrangements. This results from the chirality of carbon centers: when carbon is bound to four different partners, these can be arranged in two different ways that are mirror images of each other (chirality). When two carbon atoms are coupled together, new chiral centers may be formed. Coupling reactions that selectively deliver products with the desired spatial arrangement are thus high on the chemist’s wish list.

Kündig and his co-workers have now made a breakthrough. They have developed a new synthesis for fused indolines, a class of materials that represent an important structural motif in many natural products and pharmaceuticals, including the tumor drug Vinblastin, the antirheumatic drug Ajmalin, and the neurotoxin strychnine. Indoline is a double-ring structure consisting of one aromatic six-carbon ring and a nitrogen-containing five-membered ring; in a fused indoline, the five-membered ring is fused with an additional five- or six-membered ring.

As a starting material, the researchers used a molecule in which the central five-membered ring is still open. One of the carbon atoms to be bound was activated through binding to a bromine atom. Cleavage of the bromine and a hydrogen atom leads to ring closure. This forms a chiral center; so two different spatial arrangements of the product are possible. Thanks to a new special palladium catalyst, the researchers were able to exclusively involve only one C–H bond (of two chemically identical ones) in the reaction. Their success stems form a bulky chiral ligand, known as an N-heterocyclic carbene, which is bound to the palladium atom. The special thing about this novel catalyst is that the selectivity is maintained even at the required high temperatures around 150 C.

More information: E. Peter Kündig, Fused Indolines by Palladium-Catalyzed Asymmetric C-C Coupling Involving an Unactivated Methylene Group, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201102639

Provided by Wiley (news : web)