Engineers solve energy puzzle: How energy levels align in a critical group of advanced materials

ScienceDaily (Nov. 6, 2011) — University of Toronto materials science and engineering (MSE) researchers have demonstrated for the first time the key mechanism behind how energy levels align in a critical group of advanced materials. This discovery is a significant breakthrough in the development of sustainable technologies such as dye-sensitized solar cells and organic light-emitting diodes (OLEDs).

Transition metal oxides, which are best-known for their application as super-conductors, have made possible many sustainable technologies developed over the last two decades, including organic photovoltaics and organic light-emitting diodes. While it is known that these materials make excellent electrical contacts in organic-based devices, it wasn't known why -- until now.

In research published in Nature Materials, MSE PhD Candidate Mark T. Greiner and Professor Zheng-Hong Lu, Canada Research Chair (Tier I) in Organic Optoelectronics, lay out the blueprint that conclusively establishes the principle of energy alignment at the interface between transition metal oxides and organic molecules.

"The energy-level of molecules on materials surfaces is like a massive jigsaw puzzle that has challenged the scientific community for a very long time," says Professor Lu. "There have been a number of suggested theories with many critical links missing. We have been fortunate to successfully build these links to finally solve this decades-old puzzle."

With this piece of the puzzle solved, this discovery could enable scientists and engineers to design simpler and more efficient organic solar cells and OLEDs to further enhance sustainable technologies and help secure our energy future.

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The above story is reprinted from materials provided by University of Toronto Faculty of Applied Science & Engineering.

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Journal Reference:

Mark T. Greiner, Michael G. Helander, Wing-Man Tang, Zhi-Bin Wang, Jacky Qiu, Zheng-Hong Lu. Universal energy-level alignment of molecules on metal oxides. Nature Materials, 2011; DOI: 10.1038/nmat3159

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Self-replication process holds promise for production of new materials

ScienceDaily (Oct. 12, 2011) — New York University scientists have developed artificial structures that can self-replicate, a process that has the potential to yield new types of materials. In the natural world, self-replication is ubiquitous in all living entities, but artificial self-replication has been elusive. The new discovery is the first steps toward a general process for self-replication of a wide variety of arbitrarily designed seeds. The seeds are made from DNA tile motifs that serve as letters arranged to spell out a particular word. The replication process preserves the letter sequence and the shape of the seed and hence the information required to produce further generations.

The work, conducted by researchers in NYU's Departments of Chemistry and Physics and its Center for Soft Matter Research, appears in the latest issue of the journal Nature.

This process holds much promise for the creation of new materials. DNA is a robust functional entity that can organize itself and other molecules into complex structures. More recently DNA has been used to organize inorganic matter, such as metallic particles, as well. The re-creation by the NYU scientists of this type of assembly in a laboratory raises the prospect for the eventual development of self-replicating materials that possess a wide range of patterns and that can perform a variety of functions. The breakthrough the NYU researchers have achieved is the replication of a system that contains complex information. Thus, the replication of this material, like that of DNA in the cell, is not limited to repeating patterns.

To demonstrate this self-replication process, the NYU scientists created artificial DNA tile motifs -- short, nanometer-scale arrangements of DNA. Each tile serves as a letter -- A or B -- that recognizes and binds to complementary letters A' or B'. In the natural world, the DNA replication process involves complementary matches between bases -- adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C) -- to form its familiar double helix. By contrast, the NYU researchers developed an artificial tile or motif, called BTX (bent triple helix molecules containing three DNA double helices), with each BTX molecule composed of 10 DNA strands. Unlike DNA, the BTX code is not limited to four letters -- in principle, it can contain quadrillions of different letters and tiles that pair using the complementarity of four DNA single strands, or "sticky ends," on each tile, to form a six-helix bundle.

In order to achieve self-replication of the BTX tile arrays, a seed word is needed to catalyze multiple generations of identical arrays. BTX's seed consists of a sequence of seven tiles -- a seven-letter word. To bring about the self-replication process, the seed is placed in a chemical solution, where it assembles complementary tiles to form a "daughter BTX array" -- a complementary word. The daughter array is then separated from the seed by heating the solution to ~ 40 oC. The process is then repeated. The daughter array binds with its complementary tiles to form a "granddaughter array," thus achieving self-replication of the material and of the information in the seed -- and hence reproducing the sequence within the original seed word. Significantly, this process is distinct from the replication processes that occur within the cell, because no biological components, particularly enzymes, are used in its execution -- even the DNA is synthetic.

"This is the first step in the process of creating artificial self-replicating materials of an arbitrary composition," said Paul Chaikin, a professor in NYU's Department of Physics and one of the study's co-authors. "The next challenge is to create a process in which self-replication occurs not only for a few generations, but long enough to show exponential growth."

"While our replication method requires multiple chemical and thermal processing cycles, we have demonstrated that it is possible to replicate not just molecules like cellular DNA or RNA, but discrete structures that could in principle assume many different shapes, have many different functional features, and be associated with many different types of chemical species," added Nadrian Seeman, a professor in NYU's Department of Chemistry and a co-author of the study.

The research was supported by grants from the W.M. Keck Foundation, the MRSEC Program of the National Science Foundation, the National Institute of General Medical Sciences, the Army Research Office, NASA, and the Office of Naval Research.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Tong Wang, Ruojie Sha, Rémi Dreyfus, Mirjam E. Leunissen, Corinna Maass, David J. Pine, Paul M. Chaikin, Nadrian C. Seeman. Self-replication of information-bearing nanoscale patterns. Nature, 2011; 478 (7368): 225 DOI: 10.1038/nature10500

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Self-replication process holds promise for production of new materials

ScienceDaily (Oct. 12, 2011) — New York University scientists have developed artificial structures that can self-replicate, a process that has the potential to yield new types of materials. In the natural world, self-replication is ubiquitous in all living entities, but artificial self-replication has been elusive. The new discovery is the first steps toward a general process for self-replication of a wide variety of arbitrarily designed seeds. The seeds are made from DNA tile motifs that serve as letters arranged to spell out a particular word. The replication process preserves the letter sequence and the shape of the seed and hence the information required to produce further generations.

The work, conducted by researchers in NYU's Departments of Chemistry and Physics and its Center for Soft Matter Research, appears in the latest issue of the journal Nature.

This process holds much promise for the creation of new materials. DNA is a robust functional entity that can organize itself and other molecules into complex structures. More recently DNA has been used to organize inorganic matter, such as metallic particles, as well. The re-creation by the NYU scientists of this type of assembly in a laboratory raises the prospect for the eventual development of self-replicating materials that possess a wide range of patterns and that can perform a variety of functions. The breakthrough the NYU researchers have achieved is the replication of a system that contains complex information. Thus, the replication of this material, like that of DNA in the cell, is not limited to repeating patterns.

To demonstrate this self-replication process, the NYU scientists created artificial DNA tile motifs -- short, nanometer-scale arrangements of DNA. Each tile serves as a letter -- A or B -- that recognizes and binds to complementary letters A' or B'. In the natural world, the DNA replication process involves complementary matches between bases -- adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C) -- to form its familiar double helix. By contrast, the NYU researchers developed an artificial tile or motif, called BTX (bent triple helix molecules containing three DNA double helices), with each BTX molecule composed of 10 DNA strands. Unlike DNA, the BTX code is not limited to four letters -- in principle, it can contain quadrillions of different letters and tiles that pair using the complementarity of four DNA single strands, or "sticky ends," on each tile, to form a six-helix bundle.

In order to achieve self-replication of the BTX tile arrays, a seed word is needed to catalyze multiple generations of identical arrays. BTX's seed consists of a sequence of seven tiles -- a seven-letter word. To bring about the self-replication process, the seed is placed in a chemical solution, where it assembles complementary tiles to form a "daughter BTX array" -- a complementary word. The daughter array is then separated from the seed by heating the solution to ~ 40 oC. The process is then repeated. The daughter array binds with its complementary tiles to form a "granddaughter array," thus achieving self-replication of the material and of the information in the seed -- and hence reproducing the sequence within the original seed word. Significantly, this process is distinct from the replication processes that occur within the cell, because no biological components, particularly enzymes, are used in its execution -- even the DNA is synthetic.

"This is the first step in the process of creating artificial self-replicating materials of an arbitrary composition," said Paul Chaikin, a professor in NYU's Department of Physics and one of the study's co-authors. "The next challenge is to create a process in which self-replication occurs not only for a few generations, but long enough to show exponential growth."

"While our replication method requires multiple chemical and thermal processing cycles, we have demonstrated that it is possible to replicate not just molecules like cellular DNA or RNA, but discrete structures that could in principle assume many different shapes, have many different functional features, and be associated with many different types of chemical species," added Nadrian Seeman, a professor in NYU's Department of Chemistry and a co-author of the study.

The research was supported by grants from the W.M. Keck Foundation, the MRSEC Program of the National Science Foundation, the National Institute of General Medical Sciences, the Army Research Office, NASA, and the Office of Naval Research.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Tong Wang, Ruojie Sha, Rémi Dreyfus, Mirjam E. Leunissen, Corinna Maass, David J. Pine, Paul M. Chaikin, Nadrian C. Seeman. Self-replication of information-bearing nanoscale patterns. Nature, 2011; 478 (7368): 225 DOI: 10.1038/nature10500

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New nanostructure-based process will streamline production of magnetic materials

ScienceDaily (Sep. 27, 2011) — Scientists at the University of Massachusetts Amherst report that for the first time they have designed a much simpler method of preparing ordered magnetic materials than ever before, by coupling magnetic properties to nanostructure formation at low temperatures.

The innovative process allows them to create room-temperature ferromagnetic materials that are stable for long periods more effectively and with fewer steps than more complicated existing methods. The approach is outlined by UMass Amherst polymer scientist Gregory Tew and colleagues in the Sept. 27 issue of Nature Communications.

Tew explains that his group's signature improvement is a one-step method to generate ordered magnetic materials based on cobalt nanostructures by encoding a block copolymer with the appropriate chemical information to self-organize into nanoscopic domains. Block copolymers are made up of two or more single-polymer subunits linked by covalent chemical bonds.

The new process delivers magnetic properties to materials upon heating the sample once to a relatively low temperature, about 390 degrees (200 degrees Celsius), which transforms them into room-temperature, fully magnetic materials. Most previous processes required either much higher temperatures or more process steps to achieve the same result, which increases costs, Tew says.

He adds, "The small cobalt particles should not be magnetic at room temperature because they are too small. However, the block copolymer's nanostructure confines them locally which apparently induces stronger magnetic interactions among the particles, yielding room-temperature ferromagnetic materials that have many practical applications."

"Until now, it has not been possible to produce ordered, magnetic materials via block copolymers in a simple process," Tew says. "Current methods require multiple steps just to generate the ordered magnetic materials. They also have limited effectiveness because they may not retain the fidelity of the ordered block copolymer, they can't confine the magnetic materials to one domain of the block copolymer, or they just don't produce strongly magnetic materials. Our process answers all these limitations."

Magnetic materials are used in everything from memory storage devices in our phones and computers to the data strips on debit and credit cards. Tew and colleagues have discovered a way to build block copolymers with the necessary chemical information to self-organize into nanoscopic structures one millionth of a millimeter thin, or about 50,000 times thinner than the average human hair.

Earlier studies have demonstrated that block copolymers can be organized over relatively large areas. What makes the UMass Amherst research group's results so intriguing, Tew says, is the possible coupling of long-range organization with improved magnetic properties. This could translate into lower-cost development of new memory media, giant magneto-resistive devices and futuristic spintronic devices that might include "instant on" computers or computers that require much less power, he points out.

He adds, "Although work remains to be done before new data storage applications are enabled, for example making the magnets harder, our process is highly tunable and therefore amendable to incorporating different types of metal precursors. This result should be interesting to every scientist in nanotechnology because it shows conclusively that nano-confinement leds to completely new properties, in this case room temperature magnetic materials."

"Our work highlights the importance of learning how to control a material's nanostructure. We show that the nanostructure is directly related to an important and practical outcome, that is, the ability to generate room-temperature magnets."

"Our work highlights the importance of learning how to control a material's nanostructure. We show that the nanostructure is directly related to an important and practical outcome, that is, the ability to generate room temperature magnets." As part of this study, the UMass Amherst team also demonstrated that using a block copolymer or nanoscopic material results in a material that is magnetic at room temperature. By contrast, using a homopolymer, or unstructured material, leads only to far less useful non- or partial-magnetic materials.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Massachusetts at Amherst.

Journal Reference:

Zoha M. AL-Badri, Raghavendra R. Maddikeri, Yongping Zha, Hitesh D. Thaker, Priyanka Dobriyal, Raja Shunmugam, Thomas P. Russell, Gregory N. Tew. Room temperature magnetic materials from nanostructured diblock copolymers. Nature Communications, 2011; 2: 482 DOI: 10.1038/ncomms1485

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Pressurized vascular systems for self-healing materials

ScienceDaily (Oct. 1, 2011) — Artificial microvascular systems for self-repair of materials damage, such as cracks in a coating applied to a building or bridge, have relied on capillary force for transport of the healing agents. Now, researchers at the Beckman Institute have demonstrated that an active pumping capability for pressurized delivery of liquid healing agents in microvascular systems significantly improves the degree of healing compared with capillary force methods.

In a paper for the Royal Society journal Interface, Nancy Sottos, Scott White, and former graduate student Andrew Hamilton report on their investigation into using an active pumping method for microvascular systems in a paper titled Pressurized vascular systems for self-healing materials. Their inspiration, they write, comes from the fact that nature in its wisdom gives that ability to many biological systems: "Fluid flow in these natural vascular systems is typically driven by a pressure gradient induced by the pumping action of a heart, even in primitive invertebrates such as earthworms."

Sottos and White, faculty in the College of Engineering at the University of Illinois, and their fellow collaborators from Beckman's Autonomous Materials Systems (AMS) group, have developed different methods for self-healing, including microvascular systems for self-repair of polymers. The vascular system works when reactive fluids are released in response to stress, enabling polymerization that restores mechanical integrity.

For this project, Sottos, White, and Hamilton sought to determine the effectiveness of an active pumping mechanism in a microvascular system because, they wrote, relying on capillary flow to disperse the healing agents "limits the size of healable damage" and because "unpressurized delivery of healing agents requires diffusional mixing -- a relatively slow and highly localized process for typical resin-hardener systems -- to occur for the healing reaction to initiate."

To achieve active pumping the researchers experimented with an external "pump" composed of two computer-controlled pressure boxes that allowed for more precise control over flow. The healing agents in the pump were fed into two parallel microchannels.

The results of using active pumping to deliver healing agents from external reservoirs showed that "a damage volume larger than the total vascular volume was effectively filled and healed. Employing pressure-driven flow removes the reliance upon capillary forces and, in the cases of dynamic pumping, mixing of the two healing agents in the damaged region was enhanced."

The improved mixing of the reactive agents results in "the formation of consistently tougher healed material over the course of numerous damage-heal cycles when compared with the alternative strategy of employing a dense spatial distribution of vascular features to achieve mixing via diffusion alone, resulting in inferior mechanical recovery."

The method reported on in the paper relied on the most effective healing technique for microvascular systems (two separated liquid-phase components that react upon contact following release caused by damage), while the use of an external, actively-controlled pump to deliver the healing agents to the damaged region "removed the constraints of limited healing agent supply."

They found that active pumping improves the degree of mechanical recovery, and that a continuous flow of healing agents from dynamic pumping extends the repeatability of the self-healing response.

"Significant improvements," they write, "are achieved in the degree of healing and the number of healing events possible, compared with prior passive schemes that utilize only capillary forces for the delivery of healing agents."

Sottos said the study was a first step toward integrating active pumping into microvascular systems. Earlier this year Sottos, White, and fellow AMS member Jeff Moore reported on a method for microvascular systems that uses structural composites reinforced with fibers that, when heated, vaporize, leaving tiny channels with multiple functionalities.

"This set-up could be used with any microvascular network, including the structural composites reported on recently," Sottos said. "In future materials, it would be ideal to have the pumping integrated in the materials itself.

"The advance of this paper is the study of active pumping/mixing for healing. We haven't applied this to healing with the structural composites yet; the present study was essential to understand what happens when we pump the healing agents."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Beckman Institute for Advanced Science and Technology. The original article was written by Steve McGaughey.

Journal Reference:

A. R. Hamilton, N. R. Sottos, and S. R. White. Pressurized vascular systems for self-healing materials. J. R. Soc. Interface, September 28, 2011 DOI: 10.1098/%u200Brsif.2011.0508

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Shape memory materials ready for mass production

ScienceDaily (Sep. 27, 2011) — Materials that can remember their shape and switch from one form to another may sound like science fiction, they are actually real and already in use all around us. But the alloy used to produce shape memory materials, based on nickel and titanium is expensive. Some researchers have started looking for cheaper options.

Five years ago, Professor Mirko Gojic, a researcher at the University of Zagreb in Croatia, wondered what his small team of researchers could do to lower the price of 'smart metals': a type of high-tech materials that can remember their original cold-forged shape, returning the pre-deformed shape by heating -- a property that makes them crucial in a series of industries. The idea was there, but problems quickly aroused from lack of money and key equipment. Thanks to the support of EUREKA, the product is now almost finalised and could be rolled out within the next two years. Gojic thinks that this international research project he led could soon turn into commercial production of a cheaper alloy for use in aerospace engineering or electronics.

Shape memory alloys can be produced to many shapes and sizes for various uses. Although not as strong as steel, they are much more elastic and their properties allow them to adopt the needed shape when exposed to high temperatures. They are used in smart phones, robotics and for medical purposes. For example, nickel-titanium alloy balloons that expand and adapt to the shape of a blood vessel when exposed to body temperatures are used in stent grafts and surgery.

One of the key problems with manufacturing such materials is their high price. Gojic and his team embarked on producing a new, cheaper alloy, based on copper, whereas the most-used alloy is built on a half-half mix of titanium and nickel, known under its trade name Nitinol. 'It is also the most expensive alloy, so there is a lot of effort going into finding an economically viable alternative', says Gojic. The research project called RSSMA, for Rapidly Solidified Shape Memory Alloys, lasted three years.

"We are not the only ones to put our efforts into research on copper alloys, we contributed to the extent of the possibilities offered by our infrastructure and benefited greatly from collaborations with international partners." Trans-border cooperation between R&D partners is one of the pre-requisites to receive financial support from EUREKA.

The Croatian team did not have the facilities to produce the new alloy, but the EUREKA grant allowed them to grow an existing collaboration with colleagues from the Faculty of Mechanical Engineering at the University of Maribor, Slovenia who helped to produce the alloys, which were then tested and examined for their characteristics in Croatia. They also collaborated with colleagues from Montanuniversität Leoben in Austria, and the Faculty of Natural Science and Engineering, University of Ljubljana in Slovenia.

'It is difficult to know exactly how much cheaper the final product will be -- it is an important economic parameter to evaluate the success of the project -- and it depends partly on techniques used to produce the alloy, but it would certainly be a cost-effective alternative, as titanium and nickel are far more expensive raw materials than copper and aluminium.' Besides the economic requirements, materials used in the production of alloys also have to comply with a certain level of purity and hold specific properties in order to be worthwhile for the industry. 'Tests so far have shown that we are on the right way and we should be able to enter soon in the production phase', Gojic says.

"We have successfully reached the final stages of the research and testing, notably in setting up a process of 'continuous casting', which is crucial for commercial production," he says. "It is important because it allows you to get an important quantity of semi-product, you can make it without interruptions, allowing for mass production, as it is done with other common metallic materials, such as steel."

The next step will be to pursue research, aiming to have a finalised product within the next one and a half years, followed by the construction of a pilot plant and then finally the take-off of the commercial production. If the next stage of the research goes well it should lead rapidly to the creation of a spin-off pilot firm to manufacture the new alloy. 'This would require more funding and I am considering applying for a further grant that would help us get to the pilot stage, which could then eventually lead to industrial scale manufacturing of the new, cheaper alloy.'

The new alloy has great commercial potential, it would mainly be used in electronics and mechanical industries, since it does not hold the biocompatibility properties of nickel and titanium. It might also find use in the booming market of smartphones and high-tech gadgets. "It would not have been possible for us to improve our knowledge and competencies without EUREKA," Gojic admits.

The grant also allowed the team to put money towards buying new equipment, such as a scanning electronic microscope and equipment for thermal analysis which was important in studying the properties of the alloys developed during the research project. Financing for the new equipment several sources, but the team had to make their own initial investment in order to be granted access to it, and EUREKA allowed them to do so. The team now continues to use this new equipment to develop the project further but also for new research activities in the field of smart materials.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Eureka.

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View the original article here

New nanostructure-based process will streamline production of magnetic materials

ScienceDaily (Sep. 27, 2011) — Scientists at the University of Massachusetts Amherst report that for the first time they have designed a much simpler method of preparing ordered magnetic materials than ever before, by coupling magnetic properties to nanostructure formation at low temperatures.

The innovative process allows them to create room-temperature ferromagnetic materials that are stable for long periods more effectively and with fewer steps than more complicated existing methods. The approach is outlined by UMass Amherst polymer scientist Gregory Tew and colleagues in the Sept. 27 issue of Nature Communications.

Tew explains that his group's signature improvement is a one-step method to generate ordered magnetic materials based on cobalt nanostructures by encoding a block copolymer with the appropriate chemical information to self-organize into nanoscopic domains. Block copolymers are made up of two or more single-polymer subunits linked by covalent chemical bonds.

The new process delivers magnetic properties to materials upon heating the sample once to a relatively low temperature, about 390 degrees (200 degrees Celsius), which transforms them into room-temperature, fully magnetic materials. Most previous processes required either much higher temperatures or more process steps to achieve the same result, which increases costs, Tew says.

He adds, "The small cobalt particles should not be magnetic at room temperature because they are too small. However, the block copolymer's nanostructure confines them locally which apparently induces stronger magnetic interactions among the particles, yielding room-temperature ferromagnetic materials that have many practical applications."

"Until now, it has not been possible to produce ordered, magnetic materials via block copolymers in a simple process," Tew says. "Current methods require multiple steps just to generate the ordered magnetic materials. They also have limited effectiveness because they may not retain the fidelity of the ordered block copolymer, they can't confine the magnetic materials to one domain of the block copolymer, or they just don't produce strongly magnetic materials. Our process answers all these limitations."

Magnetic materials are used in everything from memory storage devices in our phones and computers to the data strips on debit and credit cards. Tew and colleagues have discovered a way to build block copolymers with the necessary chemical information to self-organize into nanoscopic structures one millionth of a millimeter thin, or about 50,000 times thinner than the average human hair.

Earlier studies have demonstrated that block copolymers can be organized over relatively large areas. What makes the UMass Amherst research group's results so intriguing, Tew says, is the possible coupling of long-range organization with improved magnetic properties. This could translate into lower-cost development of new memory media, giant magneto-resistive devices and futuristic spintronic devices that might include "instant on" computers or computers that require much less power, he points out.

He adds, "Although work remains to be done before new data storage applications are enabled, for example making the magnets harder, our process is highly tunable and therefore amendable to incorporating different types of metal precursors. This result should be interesting to every scientist in nanotechnology because it shows conclusively that nano-confinement leds to completely new properties, in this case room temperature magnetic materials."

"Our work highlights the importance of learning how to control a material's nanostructure. We show that the nanostructure is directly related to an important and practical outcome, that is, the ability to generate room-temperature magnets."

"Our work highlights the importance of learning how to control a material's nanostructure. We show that the nanostructure is directly related to an important and practical outcome, that is, the ability to generate room temperature magnets." As part of this study, the UMass Amherst team also demonstrated that using a block copolymer or nanoscopic material results in a material that is magnetic at room temperature. By contrast, using a homopolymer, or unstructured material, leads only to far less useful non- or partial-magnetic materials.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Massachusetts at Amherst.

Journal Reference:

Zoha M. AL-Badri, Raghavendra R. Maddikeri, Yongping Zha, Hitesh D. Thaker, Priyanka Dobriyal, Raja Shunmugam, Thomas P. Russell, Gregory N. Tew. Room temperature magnetic materials from nanostructured diblock copolymers. Nature Communications, 2011; 2: 482 DOI: 10.1038/ncomms1485

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Pressurized vascular systems for self-healing materials

ScienceDaily (Oct. 1, 2011) — Artificial microvascular systems for self-repair of materials damage, such as cracks in a coating applied to a building or bridge, have relied on capillary force for transport of the healing agents. Now, researchers at the Beckman Institute have demonstrated that an active pumping capability for pressurized delivery of liquid healing agents in microvascular systems significantly improves the degree of healing compared with capillary force methods.

In a paper for the Royal Society journal Interface, Nancy Sottos, Scott White, and former graduate student Andrew Hamilton report on their investigation into using an active pumping method for microvascular systems in a paper titled Pressurized vascular systems for self-healing materials. Their inspiration, they write, comes from the fact that nature in its wisdom gives that ability to many biological systems: "Fluid flow in these natural vascular systems is typically driven by a pressure gradient induced by the pumping action of a heart, even in primitive invertebrates such as earthworms."

Sottos and White, faculty in the College of Engineering at the University of Illinois, and their fellow collaborators from Beckman's Autonomous Materials Systems (AMS) group, have developed different methods for self-healing, including microvascular systems for self-repair of polymers. The vascular system works when reactive fluids are released in response to stress, enabling polymerization that restores mechanical integrity.

For this project, Sottos, White, and Hamilton sought to determine the effectiveness of an active pumping mechanism in a microvascular system because, they wrote, relying on capillary flow to disperse the healing agents "limits the size of healable damage" and because "unpressurized delivery of healing agents requires diffusional mixing -- a relatively slow and highly localized process for typical resin-hardener systems -- to occur for the healing reaction to initiate."

To achieve active pumping the researchers experimented with an external "pump" composed of two computer-controlled pressure boxes that allowed for more precise control over flow. The healing agents in the pump were fed into two parallel microchannels.

The results of using active pumping to deliver healing agents from external reservoirs showed that "a damage volume larger than the total vascular volume was effectively filled and healed. Employing pressure-driven flow removes the reliance upon capillary forces and, in the cases of dynamic pumping, mixing of the two healing agents in the damaged region was enhanced."

The improved mixing of the reactive agents results in "the formation of consistently tougher healed material over the course of numerous damage-heal cycles when compared with the alternative strategy of employing a dense spatial distribution of vascular features to achieve mixing via diffusion alone, resulting in inferior mechanical recovery."

The method reported on in the paper relied on the most effective healing technique for microvascular systems (two separated liquid-phase components that react upon contact following release caused by damage), while the use of an external, actively-controlled pump to deliver the healing agents to the damaged region "removed the constraints of limited healing agent supply."

They found that active pumping improves the degree of mechanical recovery, and that a continuous flow of healing agents from dynamic pumping extends the repeatability of the self-healing response.

"Significant improvements," they write, "are achieved in the degree of healing and the number of healing events possible, compared with prior passive schemes that utilize only capillary forces for the delivery of healing agents."

Sottos said the study was a first step toward integrating active pumping into microvascular systems. Earlier this year Sottos, White, and fellow AMS member Jeff Moore reported on a method for microvascular systems that uses structural composites reinforced with fibers that, when heated, vaporize, leaving tiny channels with multiple functionalities.

"This set-up could be used with any microvascular network, including the structural composites reported on recently," Sottos said. "In future materials, it would be ideal to have the pumping integrated in the materials itself.

"The advance of this paper is the study of active pumping/mixing for healing. We haven't applied this to healing with the structural composites yet; the present study was essential to understand what happens when we pump the healing agents."

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Beckman Institute for Advanced Science and Technology. The original article was written by Steve McGaughey.

Journal Reference:

A. R. Hamilton, N. R. Sottos, and S. R. White. Pressurized vascular systems for self-healing materials. J. R. Soc. Interface, September 28, 2011 DOI: 10.1098/%u200Brsif.2011.0508

Note: If no author is given, the source is cited instead.

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Shape memory materials ready for mass production

ScienceDaily (Sep. 27, 2011) — Materials that can remember their shape and switch from one form to another may sound like science fiction, they are actually real and already in use all around us. But the alloy used to produce shape memory materials, based on nickel and titanium is expensive. Some researchers have started looking for cheaper options.

Five years ago, Professor Mirko Gojic, a researcher at the University of Zagreb in Croatia, wondered what his small team of researchers could do to lower the price of 'smart metals': a type of high-tech materials that can remember their original cold-forged shape, returning the pre-deformed shape by heating -- a property that makes them crucial in a series of industries. The idea was there, but problems quickly aroused from lack of money and key equipment. Thanks to the support of EUREKA, the product is now almost finalised and could be rolled out within the next two years. Gojic thinks that this international research project he led could soon turn into commercial production of a cheaper alloy for use in aerospace engineering or electronics.

Shape memory alloys can be produced to many shapes and sizes for various uses. Although not as strong as steel, they are much more elastic and their properties allow them to adopt the needed shape when exposed to high temperatures. They are used in smart phones, robotics and for medical purposes. For example, nickel-titanium alloy balloons that expand and adapt to the shape of a blood vessel when exposed to body temperatures are used in stent grafts and surgery.

One of the key problems with manufacturing such materials is their high price. Gojic and his team embarked on producing a new, cheaper alloy, based on copper, whereas the most-used alloy is built on a half-half mix of titanium and nickel, known under its trade name Nitinol. 'It is also the most expensive alloy, so there is a lot of effort going into finding an economically viable alternative', says Gojic. The research project called RSSMA, for Rapidly Solidified Shape Memory Alloys, lasted three years.

"We are not the only ones to put our efforts into research on copper alloys, we contributed to the extent of the possibilities offered by our infrastructure and benefited greatly from collaborations with international partners." Trans-border cooperation between R&D partners is one of the pre-requisites to receive financial support from EUREKA.

The Croatian team did not have the facilities to produce the new alloy, but the EUREKA grant allowed them to grow an existing collaboration with colleagues from the Faculty of Mechanical Engineering at the University of Maribor, Slovenia who helped to produce the alloys, which were then tested and examined for their characteristics in Croatia. They also collaborated with colleagues from Montanuniversität Leoben in Austria, and the Faculty of Natural Science and Engineering, University of Ljubljana in Slovenia.

'It is difficult to know exactly how much cheaper the final product will be -- it is an important economic parameter to evaluate the success of the project -- and it depends partly on techniques used to produce the alloy, but it would certainly be a cost-effective alternative, as titanium and nickel are far more expensive raw materials than copper and aluminium.' Besides the economic requirements, materials used in the production of alloys also have to comply with a certain level of purity and hold specific properties in order to be worthwhile for the industry. 'Tests so far have shown that we are on the right way and we should be able to enter soon in the production phase', Gojic says.

"We have successfully reached the final stages of the research and testing, notably in setting up a process of 'continuous casting', which is crucial for commercial production," he says. "It is important because it allows you to get an important quantity of semi-product, you can make it without interruptions, allowing for mass production, as it is done with other common metallic materials, such as steel."

The next step will be to pursue research, aiming to have a finalised product within the next one and a half years, followed by the construction of a pilot plant and then finally the take-off of the commercial production. If the next stage of the research goes well it should lead rapidly to the creation of a spin-off pilot firm to manufacture the new alloy. 'This would require more funding and I am considering applying for a further grant that would help us get to the pilot stage, which could then eventually lead to industrial scale manufacturing of the new, cheaper alloy.'

The new alloy has great commercial potential, it would mainly be used in electronics and mechanical industries, since it does not hold the biocompatibility properties of nickel and titanium. It might also find use in the booming market of smartphones and high-tech gadgets. "It would not have been possible for us to improve our knowledge and competencies without EUREKA," Gojic admits.

The grant also allowed the team to put money towards buying new equipment, such as a scanning electronic microscope and equipment for thermal analysis which was important in studying the properties of the alloys developed during the research project. Financing for the new equipment several sources, but the team had to make their own initial investment in order to be granted access to it, and EUREKA allowed them to do so. The team now continues to use this new equipment to develop the project further but also for new research activities in the field of smart materials.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Eureka.

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Graphene may gain an on-off switch, adding semiconductor to long list of material's achievements

ScienceDaily (June 17, 2011) — A team of researchers has proposed a way to turn the material graphene into a semiconductor, enabling it to control the flow of electrons with a laser "on-off switch."

Graphene is thinnest and strongest material ever discovered. It's a layer of carbon atoms only one-atom thick, but 200 times stronger than steel. It also conducts electricity extremely well and heat better than any other known material. It is almost completely transparent, yet so dense that not even atoms of helium can penetrate it. In spite of the impressive list of promising prospects, however, graphene appears to lack a critical property -- it doesn't have a "band gap."

A band gap is the basic property of semiconductors, enabling materials to control the flow of electrons. This on-off property is the foundation of computers, encoding the 0s and 1s of computer languages.

Now, a team of researchers at the National University of Córdoba and CONICET in Argentina; the Institut Catala de Nanotecnologia in Barcelona, Spain; and RWTH Aachen University, Germany; suggest that illuminating graphene with a mid-infrared laser could be a key to switch off conduction, thereby improving the possibilities for novel optoelectronic devices.

In an article featured in Applied Physics Letters, the researchers report on the first atomistic simulations of electrical conduction through a micrometer-sized graphene sample illuminated by a laser field. Their simulations show that a laser in the mid-infrared can open an observable band gap in this otherwise gapless material.

"Imagine that by turning on the light, graphene conduction is turned off, or vice versa. This would allow the transduction of optical into electrical signals," says Luis Foa Torres, the researcher leading this collaboration. "The problem of graphene interacting with radiation is also of current interest for the understanding of more exotic states of matter such as the topological insulators."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

Herna´n L. Calvo, Horacio M. Pastawski, Stephan Roche, Luis E. F. Foa Torres. Tuning laser-induced band gaps in graphene. Applied Physics Letters, 2011; 98 (23): 232103 DOI: 10.1063/1.3597412

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Graphene may gain an on-off switch, adding semiconductor to long list of material's achievements

ScienceDaily (June 17, 2011) — A team of researchers has proposed a way to turn the material graphene into a semiconductor, enabling it to control the flow of electrons with a laser "on-off switch."

Graphene is thinnest and strongest material ever discovered. It's a layer of carbon atoms only one-atom thick, but 200 times stronger than steel. It also conducts electricity extremely well and heat better than any other known material. It is almost completely transparent, yet so dense that not even atoms of helium can penetrate it. In spite of the impressive list of promising prospects, however, graphene appears to lack a critical property -- it doesn't have a "band gap."

A band gap is the basic property of semiconductors, enabling materials to control the flow of electrons. This on-off property is the foundation of computers, encoding the 0s and 1s of computer languages.

Now, a team of researchers at the National University of Córdoba and CONICET in Argentina; the Institut Catala de Nanotecnologia in Barcelona, Spain; and RWTH Aachen University, Germany; suggest that illuminating graphene with a mid-infrared laser could be a key to switch off conduction, thereby improving the possibilities for novel optoelectronic devices.

In an article featured in Applied Physics Letters, the researchers report on the first atomistic simulations of electrical conduction through a micrometer-sized graphene sample illuminated by a laser field. Their simulations show that a laser in the mid-infrared can open an observable band gap in this otherwise gapless material.

"Imagine that by turning on the light, graphene conduction is turned off, or vice versa. This would allow the transduction of optical into electrical signals," says Luis Foa Torres, the researcher leading this collaboration. "The problem of graphene interacting with radiation is also of current interest for the understanding of more exotic states of matter such as the topological insulators."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

Herna´n L. Calvo, Horacio M. Pastawski, Stephan Roche, Luis E. F. Foa Torres. Tuning laser-induced band gaps in graphene. Applied Physics Letters, 2011; 98 (23): 232103 DOI: 10.1063/1.3597412

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here