(November 19, 2010 – Marketwire) — Magnolia Solar Corporation (OTCBB: MGLT) welcomed Professor Zhong Lin (Z. L.) Wang, Distinguished Professor and Director, Center for Nanostructure Characterization at Georgia Tech, to its Technical Advisory Board (TAB). Professor Wang is a world-renowned expert in nanostructure growth and characterization of semiconductor materials and devices for energy harvesting technology.

Professor Wang has done pioneering work on Zinc Oxide (ZnO), Zinc Sulphide (ZnS) and related materials-based nanostructures, i.e. nanowires and nanorods growth technology, growth demonstration and pioneering work in its applications for energy harvesting technology and other optical sensor applications. His pioneering work in nanogenerators for energy harvesting has been recognized worldwide as one of the 10 most impacting technologies for the next 10-30 years by MIT Technology Review, New Scientist and other International publications. He is an inventor or co-inventor of many U.S. patents and has authored or co-authored more than 650 publications. Professor Wang is a Fellow of the American Physical Society (APS) and American Association of Advancement of Science (AAAS).

"Magnolia has several government-funded programs in process right now and we’ll use Professor Wang’s expertise in nanostructure materials, growth technology and innovative concepts to help us accelerate the development of the critical technologies required to produce Magnolia’s high efficiency third generation solar cells. Professor Wang will also be advising us on the development of our intellectual property portfolio and in the patent filing process. Programs that Magnolia will be spending considerable effort on during the remainder of this year and throughout 2011," noted Dr. Ashok K. Sood, president and CEO of Magnolia Solar Corporation.

Magnolia is developing solar cell technology to cover the ultraviolet, visible, and infrared part of the solar spectrum with a nano-based thin-film solar cell technology. For more information, please visit www.MagnoliaSolar.com.

Follow Small Times on Twitter.com by clicking www.twitter.com/smalltimes. Or join our Facebook group

(November 19, 2010) — Optically active semiconductor nanopillar arrays now absorb sunlight better than ever, thanks to research carried out at Lawrence Berkeley National Laboratory and the University of California at Berkeley.[1] 

Nanopillar tune-up
"By tuning the shape and geometry of highly ordered nanopillar arrays of germanium or cadmium sulfide, we have been able to drastically enhance the optical absorption properties of our nanopillars," says Ali Javey, one of the researchers.

Javey and his group were the first to demonstrate a technique by which cadmium sulfide nanopillars can be mass-produced in large-scale flexible modules. In this latest work, they were able to produce nanopillars that absorb light as well or even better than commercial thin-film solar cells, using far less semiconductor material and without the need for antireflective coatings.

"To enhance the broadband optical absorption efficiency of our nanopillars, we used a novel dual-diameter structure that features a small (60 nm) diameter tip with minimal reflectance to allow more light in, and a large (130 nm) diameter base for maximal absorption to enable more light to be converted into electricity," Javey says. "This dual-diameter structure absorbed 99% of incident visible light, compared to the 85% absorption by our earlier nanopillars, which had the same diameter along their entire length."

Work has shown that 3D arrays of semiconductor nanopillars with well-defined diameter, length and pitch excel at trapping light while using less than half the semiconductor material required for thin-film solar cells made of compound semiconductors, such as cadmium telluride, and about 1% of the material used in solar cells made from bulk silicon. But until the work of Javey and his research group, fabricating such nanopillars was a complex and cumbersome procedure.

Alumina foil comes in handy
Javey and his colleagues fashioned their dual-diameter nanopillars from molds they made in 2.5-µm-thick alumina foil (see figure). A two-step anodization process was used to create an array of 1-µm-deep pores in the mold with dual diameters. Gold particles were then deposited into the pores to catalyze the growth of the semiconductor nanopillars.

The germanium nanopillars can be tuned to absorb infrared photons for highly sensitive detectors, and the cadmium sulfide/telluride nanopillars are ideal for solar cells. The fabrication technique is highly generic, Javey says; it could be used with numerous other semiconductor materials as well for specific applications. Recently, he and his group demonstrated that the cross-sectional portion of the nanopillar arrays can also be tuned to assume specific shapes–square, rectangle or circle–by changing the shape of the template.

REFERENCE:

1. Zhiyong Fan et al., Nano Letters, 10 (10), p. 3823 (2010).

(November 17, 2010) — University of California, San Diego NanoEngineers won a grant from the National Institutes of Health (NIH) to develop the tools to manufacture biodegradable frames around which heart tissues — functional blood vessels included — will grow. Developing methods for growing tissues that mimic nature’s fine-grained details, including vasculature, could lead to breakthroughs in efforts to grow replacement cardiac tissues for people who have suffered a heart attack. The work could also lead to better systems for growing and studying cells, including stem cells, in the laboratory.

Figure 1. Scanning electron microscopy (SEM) image of a scaffold with a honeycomb pore design that Shaochen Chen and colleagues created using an older version of Shaochen Chen’s scaffold manufacturing platform.

Professor Shaochen Chen from the UC San Diego Department of NanoEngineering is the Principal Investigator on the four-year $1.5 million grant from the National Institutes of Health. The grant is funding development of the manufacturing platform necessary to produce these biodegradable frames or “scaffolds.”

“We are creating biomaterials with nanostructures on the inside,” said Chen. “Scientifically there are so many opportunities at the molecular level, and nanoengineering is a perfect fit for that. We expect our new biofabrication platform will yield tissues that mimic natural tissues much more closely.”

One such opportunity is to add new levels of precision and functionality to the scaffolds produced by the “biofabrication platform” that Chen and his collaborators invented and have been improving over the last five years.

With the improved biofabrication platform, engineers in the Department of NanoEngineering within the UC San Diego Jacobs School of Engineering will be able to produce scaffolds with precisely designed systems of nanoscale pores and other microarchitectural details that control how cells interact with each other and with the environment.

“You need to design the pores so the cell can get nutrition and dump waste…pathways for the cell to survive in the system,” explained Chen. 

Figure 2. Scanning electron microscopy (SEM) image of a scaffold with a triangle pore design that Shaochen Chen and colleagues created using an older version of Shaochen Chen’s scaffold manufacturing platform.

The researchers also plan to create scaffolds with tubes, and then seed those tubes with the cells that line blood vessels — endothelial cells — to try to generate functioning vascular systems. The lack of blood vessels in most tissue regeneration systems results in cell death, loss of function, and limits the maximum size of regenerated tissues.

In addition, the chemical properties of the new scaffolds will change from top to bottom, which will create chemical gradients that drive cell growth.

As in previous versions of Chen’s scaffold-building system, cells will be encapsulated within scaffold walls.

“Usually, when researchers grow tissue, they make a scaffold, put the cells in the scaffold and let the cells grow,” explained Chen. “When we fabricate our scaffolds, the cells are already inside the scaffold walls.” Encapsulating cells within the walls encourages uniform seeding of cells.

The scaffolds will be based on natural materials such as hyaluronic acid, a key component of the “extracellular matrix” that provides structural support, wound healing, and a range of other functions to human and other animal tissues. "The hydrogels for our scaffolds can’t be too soft, too sticky or too rigid. They need to fit the needs of the biological tissue," said Chen. Collaborators at Harvard Medical School will grow and characterize the tissues started on the scaffolds.

To manufacture tissue scaffolds, Chen and colleagues have developed and continue to refine a manufacturing process that uses light, precisely controlled mirrors, and a computer projection system. First, the engineers design a three dimensional model of the structure to be printed. Next, the engineers prepare a solution containing both the cells that will eventually grow into the tissue and the polymers that will solidify into the scaffold. When light shines into the solution using the series of mirrors, the scaffold solidifies according to the exact specifications of the projected image. Following these steps, scaffolds are manufactured and cells are encapsulated in scaffold walls as light solidifies the polymers one layer at a time.

"With our biofabrication platform, we can build arbitrary, three-dimensional shapes, like branches of blood vessels, and tubes — large and small," said Chen. "My focus is on the materials fabrication and devices level. This work is applicable to many different types of cells and tissues."

Learn more at http://www.ucsd.edu/

Follow Small Times on Twitter.com by clicking www.twitter.com/smalltimes. Or join our Facebook group

(November 17, 2010) — While offering great promise in a host of new applications, carbon nanotubes (CNTs) could be harmful to humans and a new risk review suggests product designers and others should provisionally treat CNTs "as if" they are hazardous.

Because environmental and health information on CNTs is incomplete and sometimes conflicting, an "anticipatory governance" approach to the technology is needed, according to Mark Philbrick of the Center of Integrated Nanomechanical Systems at the University of California, Berkeley. Anticipatory governance is an approach designed to support decision makers where there is uncertainty about safety, a common situation when managing emerging technologies.

Given the "conflicted character of the data," how "relevant actors" should respond is the central question Philbrick asks in developing strategies for utilizing CNTs. He asserts that treating carbon nanotubes "as if" they are hazardous implies limiting exposure throughout product life-cycles. This means implementing strong engineering controls for CNT research and manufacturing, avoiding applications where CNTs would be routinely released to the environment, and planning for recycling at the end of a product’s useful life. The article also argues, "The anticipatory governance approach is particularly important as innovation rates in nanotechnologies exceed our capacity to assess human and environmental consequences of these innovations, especially when deployed at commercial scales…it helps identify uncertainties in our knowledge and focuses future research to address those gaps." 

The research was funded by the National Science Foundation and  conclusions are detailed in Philbrick’s article, "An Anticipatory Governance Approach to Carbon Nanotubes," in the November issue of the journal Risk Analysis published by the Society for Risk Analysis. The entire November issue is devoted to risk analysis articles related to nanotechnology.

An anticipatory approach is particularly important until the toxicity and behavior of CNTs in the environment are better understood, especially as they can remain airborne for extended periods, and share some characteristics with asbestos. While a few rodent studies have found similarities between the health effects of inhaling both substances, there is not enough data to draw firm conclusions.

The article notes the promise held out by CNTs is immense: some types conduct electricity and heat better than copper, others are stronger than steel while weighing less than aluminum, and yet others could be used in targeted drug delivery. These properties could find uses in aircraft frames, sensors, and electrical transmission. Nevertheless, treating them "as if" they are hazardous is a prudent course of action given uncertainty about their potential health consequences, the author said. 

Risk Analysis: An International Journal is published by the nonprofit Society for Risk Analysis (SRA). SRA is a multidisciplinary, interdisciplinary, scholarly, international society that provides an open forum for all those who are interested in risk analysis. Risk analysis is broadly defined to include risk assessment, risk characterization, risk communication, risk management, and policy relating to risk, in the context of risks of concern to individuals, to public and private sector organizations, and to society at a local, regional, national, or global level. www.sra.org

Follow Small Times on Twitter.com by clicking www.twitter.com/smalltimes. Or join our Facebook group

(November 16, 2010) — Metallic and semiconducting single-wall carbon nanotubes (SWCNT) can be distinguished using a new imaging tool for rapidly screening the structures, researched at the Weldon School of Biomedical Engineering, Purdue University. The technology may hasten the use of nanotubes in creating a new class of computers and electronics that are faster and consume less power than those in use today.

Metallic versions form unavoidably during the CNT manufacturing process, contaminating the semiconducting nanotubes. Now researchers have discovered that an advanced imaging technology could solve this problem, said Ji-Xin Cheng, an associate professor of biomedical engineering and chemistry at Purdue University. "The imaging system uses a pulsing laser to deposit energy into the nanotubes, pumping the nanotubes from a ground state to an excited state," he said. "Then, another laser called a probe senses the excited nanotubes and reveals the contrast between metallic and semiconductor tubes."

The technique, called transient absorption, measures the "metallicity" of the tubes. The detection method might be combined with another laser to zap the unwanted metallic nanotubes as they roll off of the manufacturing line, leaving only the semiconducting tubes.

Findings are detailed in a research paper, "Fast Mapping of Metallicity in Individual Single-Walled Carbon Nanotubes Using a Transient Absorption Optical Microscope" appearing online this week in the journal Physical Review Letters and authored by Purdue physics doctoral student Yookyung Jung; biomedical engineering research scientist Mikhail N. Slipchenko; Chang-Hua Liu, an electrical engineering graduate student at the University of Michigan; Alexander E. Ribbe, manager of the Nanotechnology Group in Purdue’s Department of Chemistry; Zhaohui Zhong, an assistant professor of electrical engineering and computer science at Michigan; and Yang and Cheng. The Michigan researchers produced the nanotubes.

Single-wall nanotubes are formed by rolling up a one-atom-thick layer of graphite called graphene, which could eventually rival silicon as a basis for computer chips. In spite of the outstanding properties of single-walled carbon nanotubes, the co-existence of metallic and semiconducting SWCNTs as a result of synthesis has hindered their electronic and photonic applications. Researchers in Cheng’s group, working with nanomaterials for biomedical studies, were puzzled when they noticed the metallic nanoparticles and semiconducting nanowires transmitted and absorbed light differently after being exposed to the pulsing laser. Researcher Chen Yang, a Purdue assistant professor of physical chemistry, suggested the method might be used to screen the nanotubes for nanoelectronics.

"When you make nanocircuits, you only want the semiconducting ones, so it’s very important to have a method to identify the metallic nanotubes," Yang said.

The nanotubes have a diameter of about 1 nanometer, or roughly the length of 10 hydrogen atoms strung together, making them far too small to be seen with a conventional light microscope. "They can be seen with an atomic force microscope, but this only tells you the morphology and surface features, not the metallic state of the nanotube," Cheng said.

The transient absorption imaging technique represents the only rapid method for telling the difference between the two types of nanotubes. The technique is "label free," meaning it does not require that the nanotubes be marked with dyes, making it potentially practical for manufacturing, he added.

The researchers performed the technique with nanotubes placed on a glass surface. Future work will focus on performing the imaging when nanotubes are on a silicon surface to determine how well it would work in industrial applications.

"We have begun this work on a silicon substrate, and preliminary results are very good," Cheng said.

Future research also may study how electrons travel inside individual nanotubes.

The research is funded by the National Science Foundation. Learn more at https://engineering.purdue.edu/BME/, Weldon School of Biomedical Engineering

Follow Small Times on Twitter.com by clicking www.twitter.com/smalltimes. Or join our Facebook group