Breakthrough in flexible electronics enabled by inorganic-based laser lift-off

 

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This schematic picture shows the flexible crossbar memory developed via the ILLO process.

A research team led by Prof. Keon Jae Lee of KAIST provides an easier methodology to realize high performance flexible electronics by using the Inorganic-based Laser Lift-off (ILLO), which enables nanoscale processes for high density flexible devices and high temperature processes that were previously difficult to achieve on plastic substrates.

Flexible electronics have been touted as the next generation in electronics in various areas, ranging from consumer electronics to bio-integrated medical devices. In spite of their merits, insufficient performance of organic materials arising from inherent material properties and processing limitations in scalability have posed big challenges to developing all-in-one flexible electronics systems in which display, processor, memory, and energy devices are integrated. The high temperature processes, essential for high performance electronic devices, have severely restricted the development of flexible electronics because of the fundamental thermal instabilities of polymer materials.

A research team headed by Professor Keon Jae Lee of the Department of Materials Science and Engineering at KAIST provides an easier methodology to realize high performance flexible electronics by using the Inorganic-based Laser Lift-off (ILLO).

The ILLO process involves depositing a laser-reactive exfoliation layer on rigid substrates, and then fabricating ultrathin inorganic electronic devices, e.g., high density crossbar memristive memory on top of the exfoliation layer. By laser irradiation through the back of the substrate, only the ultrathin inorganic device layers are exfoliated from the substrate as a result of the reaction between laser and exfoliation layer, and then subsequently transferred onto any kind of receiver substrate such as plastic, paper, and even fabric.

This ILLO process can enable not only nanoscale processes for high density flexible devices but also the high temperature process that was previously difficult to achieve on plastic substrates. The transferred device successfully demonstrates fully-functional random access memory operation on flexible substrates even under severe bending.

Professor Lee said, "By selecting an optimized set of inorganic exfoliation layer and substrate, a nanoscale process at a high temperature of over 1000 °C can be utilized for high performance flexible electronics. The ILLO process can be applied to diverse flexible electronics, such as driving circuits for displays and inorganic-based energy devices such as battery, solar cell, and self-powered devices that require high temperature processes."

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Story Source:

The above story is based on materials provided by ResearchSEA. Note: Materials may be edited for content and length.

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Journal Reference:

1. Seungjun Kim, Jung Hwan Son, Seung Hyun Lee, Byoung Kuk You, Kwi-Il Park, Hwan Keon Lee, Myunghwan Byun, Keon Jae Lee. Flexible Crossbar-Structured Resistive Memory Arrays on Plastic Substrates via Inorganic-Based Laser Lift-Off. Advanced Materials, 2014; 26 (44): 7480 DOI: 10.1002/adma.201402472

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New plastic that disappears when you want it to

 

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Plastic populates our world through everything from electronics to packaging and vehicles. Once discarded, it resides almost permanently in landfills and oceans. A discovery by researchers at North Dakota State University, Fargo, holds scientific promise that could lead to a new type of plastic that can be broken down when exposed to a specific type of light and is reduced back to molecules, which could then be used to create new plastic.

Published in Angewandte Chemie, the proof of concept experiment outlines the work of researchers in the Center for Sustainable Materials Science at NDSU. The multidisciplinary team includes researchers from the Department of Chemistry and Biochemistry: Mukund Sibi, university distinguished professor; Sivaguru Jayaraman, James A. Meier professor; postdoctoral fellow Saravana Rajendran; graduate student Ramya Raghunathan; postdoctoral fellow Retheesh Krishnan; and staff scientist Angel Ugrinov; as well as Dean Webster, professor and chair of the Department of Coatings and Polymeric Materials and postdoctoral fellow Ivan Hevus.

The research team focuses on biomass, using oilseed from agricultural crops, cellulose, lignin and sucrose to generate building blocks of molecules that are made into polymers to create plastics. One of the grand challenges for the 21st century is sustainability that lessens dependency on fossil fuels. NDSU, in association with the North Dakota Experimental Program to Stimulate Competitive Research (ND EPSCoR), established the Center for Sustainable Materials Science to develop a program for the preparation of polymers and composites using biomass, a renewable resource.

"Real sustainability involves breaking it back into the building blocks. We have shown that we can break it down into the building blocks and re-make the polymer," said Dr. Sibi.

In their proof of concept experiment, the group used fructose, found commonly in fruit, to create a solution of molecules, which was then converted to a plastic (polymer). By exposing the plastic to ultraviolet light at 350 nanometers for three hours, researchers degraded the plastic, reducing it back to the soluble building block molecules from which it began.

Plastics usually don't decay for hundreds of years, creating solid waste issues. They generally degrade slowly, potentially leaching chemicals into the environment or creating toxins in the air when burned.

"This cradle-to-cradle approach to create a plastic which can be degraded easily offers scientific potential for eventual products that could lessen dependence on fossil fuels and decrease the amount of raw materials needed," said Dr. Webster.

"Our strategy has the potential to build novel materials from biomass that are degradable with light after usage, mitigating the stress of unwanted chemicals in our environment. Studies to address these aspects are currently underway in our laboratories," said Dr. Sivaguru Jayaraman.

Dr. Sibi's lab makes monomers and biobased triggers; Dr. Siva's group specializes in photochemical sciences and photo degradation; and Dr. Webster's team works in polymer chemistry.

"It is the teamwork which allows us to do this kind of work. We need everyone's expertise to solve this issue," said Sibi.

The researchers say further study is needed to evaluate the durability and strength of potential plastics derived from biomass before potential product commercialization could occur. "What is the best trigger to use to break them down? What is the best monomer to use? What is the best polymer we can make?" said Sibi.

In the next two years, the group will examine how their process might work with plastics used in cars and electronics, as well as in other items.

This research is based on the support from the National Science Foundation (grant numbers EPS-0814442 and IIA-1355466) for the Center for Sustainable Materials Science (CSMS) at NDSU, a research center in association with the North Dakota Experimental Program to Stimulate Competitive Research.

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Story Source:

The above story is based on materials provided by North Dakota State University. Note: Materials may be edited for content and length.

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Journal Reference:

1. Saravanakumar Rajendran, Ramya Raghunathan, Ivan Hevus, Retheesh Krishnan, Angel Ugrinov, Mukund P. Sibi, Dean C. Webster, Jayaraman Sivaguru. Programmed Photodegradation of Polymeric/Oligomeric Materials Derived from Renewable Bioresources. Angewandte Chemie International Edition, 2014; DOI: 10.1002/anie.201408492

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Blu-ray disc can be used to improve solar cell performance

 

 

An interdisciplinary research team has discovered that the pattern of information written on a Blu-ray disc -- and it doesn't matter if it's Jackie Chan's "Supercop" or the cartoon "Family Guy" -- works very well for improving light absorption across the solar spectrum. And better yet, the researchers know why.

"We had a hunch that Blu-ray discs might work for improving solar cells, and, to our delight, we found the existing patterns are already very good," said Jiaxing Huang, a materials chemist and an associate professor of materials science and engineering in the McCormick School of Engineering and Applied Science. "It's as if electrical engineers and computer scientists developing the Blu-ray technology have been subconsciously doing our jobs, too."

Blu-ray discs contain a higher density of data than DVDs or CDs, and it is this quasi-random pattern, perfected by engineers over decades for data storage, that, when transferred to the surface of solar cells, provides the right texture to improve the cells' light absorption and performance.

Working with Cheng Sun, an associate professor of mechanical engineering at McCormick, Huang and his team tested a wide range of movies and television shows stored on Blu-ray discs, including action movies, dramas, documentaries, cartoons and black-and-white content, and found the video content did not matter. All worked equally well for enhancing light absorption in solar cells.

The findings will be published Nov. 25 in the journal Nature Communications.

In the field of solar cells, it is known that if texture is placed on the surface of a solar cell, light is scattered more effectively, increasing a cell's efficiency. Scientists have long been searching for the most effective texture with a reasonable manufacturing cost.

The Northwestern researchers have demonstrated that a Blu-ray disc's strings of binary code 0s and 1s, embedded as islands and pits to store video information, give solar cells the near-optimal surface texture to improve their absorption over the broad spectrum of sunlight.

In their study, the researchers first selected the Jackie Chan movie "Supercop." They replicated the pattern on the active layer of a polymer solar cell and found the cell was more efficient than a control solar cell with a random pattern on its surface.

"We found a random pattern or texture does work better than no pattern, but a Blu-ray disc pattern is best of all," Huang said. "Then I wondered, why did it work? If you don't understand why, it's not good science."

Huang puzzled over the question of why for some time. One day, his wife, Shaorong Liu, a database engineer at IBM, suggested it likely had something to do with data compression. That was the insight Huang needed.

Huang and Sun then turned to McCormick colleague Dongning Guo, an expert in information theory, to investigate this idea. Guo is an associate professor of electrical engineering and computer science.

The researchers looked closely at the data processing algorithms in the Blu-ray standard and noted the algorithms serve two major purposes:

• Achieving as high a degree of compression as possible by converting the video signals into a seemingly random sequence of 0s and 1s; and
• Increasing error tolerance by adding controlled redundancy into the data sequence, which also limits the number of consecutive 0s and 1s.

These two purposes, the researchers said, have resulted in a quasi-random array of islands and pits (0s and 1s) with feature sizes between 150 and 525 nanometers. And this range, it turns out, works quite well for light-trapping applications over the entire solar spectrum.

The overall broadband absorption enhancement of a Blu-ray patterned solar cell was measured to be 21.8 percent, the researchers report.

"In addition to improving polymer solar cells, our simulation suggests the Blu-ray patterns could be broadly applied for light trapping in other kinds of solar cells," Sun said.

"It has been quite unexpected and truly thrilling to see new science coming out of the intersection of information theory, nanophotonics and materials science," Huang said.

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Story Source:

The above story is based on materials provided by Northwestern University. Note: Materials may be edited for content and length.

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Journal Reference:

1. Alexander J. Smith, Chen Wang, Dongning Guo, Cheng Sun, Jiaxing Huang. Repurposing Blu-ray movie discs as quasi-random nanoimprinting templates for photon management. Nature Communications, 2014; 5: 5517 DOI: 10.1038/ncomms6517

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Northwestern University. "Blu-ray disc can be used to improve solar cell performance." ScienceDaily. ScienceDaily, 25 November 2014. <www.sciencedaily.com/releases/2014/11/141125111816.htm>.

The Microsoft staff - 1978

 

A terceira guerra mundial

 

Fiquem tranquilos meus filhos. Não haverá uma terceira guerra mundial. Pelo menos não o tipo de guerra que o título sugere. Travamos hoje únicamente uma guerra tecnológica. Os países desenvolvidos tem hoje bastante experiência para antever que uma terceira guerra mundial nos moldes da Segunda Grande Guerra, seria exatamete como atear fogo em sua própria casa para livrar-se de um rato. Ou matar a vaca para livrá-la dos carrapatos.

Durmam tranquilos, meus queridos amigos. Não haverá uma terceira guerra mundial.

Mas, por via da dúvidas, considerem construir um abrigo subterrâneo super-seguro, com isolamento contra infiltrações radioativas. Um gerador de eletricidade seria recomendável, bem como algumas toneladas de alimentos conservados em freezeres,  e é claro, bastante água potável, sem esquecer de um gerador de oxigênio altamente eficiente.

Execution by cannon–Iran–late 19th century

 

Nós, seres humanos, podemos ser qualquer coisa que nos aflore à mente, menos uma: Sermos racionais ou qualquer coisa semelhante ou algo que o valha, em atos como esse da foto.  Esta, como muitas outras imagens provam isso. Nossos  bilhões de neurônios, trilhões de sinapses nervosas e um exército de neuro-transmissores executam apenas um trabalho: Circulam pelo nosso cérebro à uma velocidade espantosa porém sem direção definida, quando se trata de assuntos como esse, de um passado distante mas cuja essencia ainda pode ser examinada, analisada.   A melhor coisa que foi “inventada” para nós é a oração e a meditação.  Isso que se vê na imagem, é tão somente um espetáculo público, nada tendo a ver com justiçamento, com penalidade. Na Idade Média era ainda pior. E pensar que temos na história da humanidade milhões de atos da mesma espécie. Estamos hoje resolvidos? Somos melhores? Aprendemos a lição?  O que se poderia fazer com esse homem que provavelmente era um assassino. Simplesmente executá-lo sumariamente por métodos comuns.  Seriam os espectadores homens sem mácula, homens íntegros, homens que havendo uma chance não fariam algo ainda pior?  O homem que seria executado era tão somente um “bode expiatório” …..   - Pensavam todos:  Com esse tipo de execução teremos a certeza que esse indivíduo morrerá sem sombra de dúvida, e então seremos expiados de qualquer culpa. Nos tornaremos homens sem mácula, sem culpa alguma….

José S de Melo

Researchers develop efficient method to produce nanoporous metals

 

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Nanoporous metals -- foam-like materials that have some degree of air vacuum in their structure -- have a wide range of applications because of their superior qualities.

They posses a high surface area for better electron transfer, which can lead to the improved performance of an electrode in an electric double capacitor or battery. Nanoporous metals offer an increased number of available sites for the adsorption of analytes, a highly desirable feature for sensors.

Lawrence Livermore National Laboratory (LLNL) and the Swiss Federal Institute of Technology (ETH) researchers have developed a cost-effective and more efficient way to manufacture nanoporous metals over many scales, from nanoscale to macroscale, which is visible to the naked eye.

The process begins with a four-inch silicon wafer. A coating of metal is added and sputtered across the wafer. Gold, silver and aluminum were used for this research project. However, the manufacturing process is not limited to these metals.

Next, a mixture of two polymers is added to the metal substrate to create patterns, a process known as diblock copolymer lithography (BCP). The pattern is transformed in a single polymer mask with nanometer-size features. Last, a technique known as anisotropic ion beam milling (IBM) is used to etch through the mask to make an array of holes, creating the nanoporous metal.

During the fabrication process, the roughness of the metal is continuously examined to ensure that the finished product has good porosity, which is key to creating the unique properties that make nanoporous materials work. The rougher the metal is, the less evenly porous it becomes.

"During fabrication, our team achieved 92 percent pore coverage with 99 percent uniformity over a 4-in silicon wafer, which means the metal was smooth and evenly porous," said Tiziana Bond, an LLNL engineer who is a member of the joint research team.

The team has defined a metric -- based on a parametrized correlation between BCP pore coverage and metal surface roughness -- by which the fabrication of nanoporous metals should be stopped when uneven porosity is the known outcome, saving processing time and costs.

"The real breakthrough is that we created a new technique to manufacture nanoporous metals that is cheap and can be done over many scales avoiding the lift-off technique to remove metals, with real-time quality control," Bond said. "These metals open the application space to areas such as energy harvesting, sensing and electrochemical studies."

The lift-off technique is a method of patterning target materials on the surface of a substrate by using a sacrificial material. One of the biggest problems with this technique is that the metal layer cannot be peeled off uniformly (or at all) at the nanoscale.

The research team's findings were reported in an article titled "Manufacturing over many scales: High fidelity macroscale coverage of nanoporous metal arrays via lift-off-free nanofrabication." It was the cover story in a recent issue of Advanced Materials Interfaces.

Other applications of nanoporous metals include supporting the development of new metamaterials (engineered materials) for radiation-enhanced filtering and manipulation, including deep ultraviolet light. These applications are possible because nanoporous materials facilitate anomalous enhancement of transmitted (or reflected) light through the tunneling of surface plasmons, a feature widely usable by light-emitting devices, plasmonic lithography, refractive-index-based sensing and all-optical switching.

Geoengineering our climate is not a 'quick fix'

 

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The deliberate, large-scale intervention in the Earth's climate system is not a "quick fix" for global warming, according to the findings of the UK's first publicly funded studies on geoengineering.

The deliberate, large-scale intervention in the Earth's climate system is not a "quick fix" for global warming, according to the findings of the UK's first publicly funded studies on geoengineering.

The results of three projects -- IAGP, led by the University of Leeds; SPICE, led by the University of Bristol; and CGG, led by the University of Oxford -- are announced at an event held at The Royal Society, London, on 26 November 2014.

Professor Piers Forster, Professor of Physical Climate Change at the University of Leeds, and the principal investigator of the Integrated Assessment of Geoengineering Proposals (IAGP) project, said: "Our research shows that the devil is in the detail. Geoengineering will be much more expensive and challenging than previous estimates suggest and any benefits would be limited.

"For example, when simulating the spraying of sea salt particles into clouds to try to brighten them, we found that only a few clouds were susceptible and that the particles would tend to coagulate and fall out before reaching the cloud base."

In September 2009, The Royal Society published a report, Geoengineering the climate: science, governance and uncertainty. It influenced research worldwide, identified important gaps and called for a major UK funding programme into geoengineering. The IAGP and SPICE projects were funded the next year, and the CGG project followed in 2012.

IAGP is the UK's first interdisciplinary research study into the controversial issue of geoengineering. It has brought together a range of expertise -- climate modelling, philosophy and engineering -- in addition to understanding public perceptions, to assess geoengineering within wider societal values.

"Cleverly designed simulations create less necessity for real-world testing.. My favourite part of the research involved creating a virtual reality in which we tried to rescue Arctic sea ice by dumping sulphur dioxide into the atmosphere from Stratotanker aircraft flying out of Svalbard in Norway," said Professor Forster.

"Issues around monitoring and predicting the effects of our actions led to huge indecision and highlighted how challenging it would be to ever try and deploy these techniques in the real world."

Researchers working on the Stratospheric Particle Injection for Climate Engineering (SPICE) project took a different tack, but came to a similar cautionary conclusion.

Rather than running simulations, SPICE researchers used volcanoes as models to mimic the effect of a solar geoengineering proposal, in which sulphate aerosols are pumped into the atmosphere to reflect more sunlight back into space. This is a process that also naturally occurs due to particles emitted from volcanic eruptions.

Dr Matthew Watson, a reader in natural hazards from the University of Bristol, and principal investigator for the SPICE project, said: "Whilst it is clear that temperatures could be reduced during deployment, the potential for misstep is considerable. By identifying risks, we hope to contribute to the evidence base around geoengineering that will determine whether deployment, in the face of the threat of climate change, has the capacity to do more good than harm."

In addition to the feasibility of deployment, IAGP researchers organised workshops to gauge people's perceptions of geoengineering. Four public workshops were held in Birmingham, Cardiff, Glasgow and Norwich, and two stakeholder workshops in London, with representation from national government departments, civil society groups and industry.

The idea that geoengineering involves "messing with nature" was found to be a central theme in public discussion groups. The workshops also revealed that, of the geoengineering proposals discussed, carbon dioxide removal approaches were favoured over solar geoengineering approaches.

In both the public discussion groups and stakeholder workshops, climate change mitigation strategies, such as improving energy efficiency measures and scaling up renewable technologies, were preferred to geoengineering proposals.

Professor Forster said: "Consulting the public, policymakers and industry from the start told us that we should only consider geoengineering within the wider context of climate change mitigation and adaptation. Geoengineering is not a 'quick fix' alternative."

Dr Watson added: "Full scale deployment of climate engineering technologies will be the clearest indication that we have failed in our role as planetary stewards, but there is a point at which not deploying some technologies would be unethical."

Meanwhile, the Climate Geoengineering Governance (CGG) project is the world's first project to concentrate on the governance and regulatory challenges posed by both research and possible deployment.

The findings of the CGG project include the likelihood that cost estimates for major projects are unrealistic, and that geoengineering must be located firmly in the context of mitigation and adaptation to climate change.

Furthermore, CGG research has also unearthed a paradox: Geoengineering proposals that are technically the easiest to implement and have the quickest impact may be most difficult to govern, while those that are easiest to govern seem likely to be further away from effective large-scale deployment.

Professor Steve Rayner, the James Martin Professor of Science and Civilization at the University of Oxford, and principal investigator for the CGG project, concludes: "Take everything you hear both for and against geoengineering with a large grain of salt. Mostly it is too soon to know what any of these technology ideas would look like in practice or what would be their true cost and benefit.

"But it's almost certain that geoengineering will be neither a magic bullet nor Pandora's Box."

Additive Manufacturing: La nuova rivoluzione industriale

 

Il 4 dicembre alle ore 17.00 si terrà presso la Bologna Business School l'incontro dedicato alla manifattura per addizione, soluzione che sta portando a una vera e propria rivoluzione industriale.

di MIT Technology Review |

Scrivevano su The Economist della manifattura per addizione: “La diffusione della stampa 3D è destinata a cambiare profondamente il manufacturing, aprendo nuove possibilità per le imprese tradizionali e contribuendo a far nascere nuovi modelli business.”
Per chi è solito seguirci, la stampa 3-D non è una novità e i suoi effetti sulla manifattura sono reali e molteplici (vedi “Una batteria e un “orecchio bionico”: Uno sguardo alle promesse della stampa 3-D", "Fab Lab Reggio Emilia: Un assaggio di MIT", "La stampa 3D: Dall'industria al Home-Made" ed anche "La stampa 3-D sta rivoluzionando la visualizzazione dei Big Data").
Mai, prima d'oggi, un processo produttivo era riuscito a interessare settori industriali tanto differenti. Per questo motivo è bene tornare spesso su questo argomento, così da poterne approfondire la comprensione, apprenderne gli ultimi sviluppi e contribuire alla sua divulgazione.
Ebbene, proprio per parlare di Stampa 3-D, o Additive Manufacturing, vi invitiamo a partecipare all'incontro che si terrà il 4 dicembre presso la Bologna Business School. A discutere del tema “Additive Manufacturing: La nuova rivoluzione industriale”, si incontreranno diversi esperti del settore, fra cui Sandro De Poli, Country CEO di General Electric, Andrea Pontremoli, CEO di Dallara Automobili, Mauro Varretto, Direttore Tecnico di Protocast / Gruppo GE, ed Avio Mauro Antolotti, Presidente di ProtoService.

In questa occasione si parlerà del significato della manifattura per addizione, del perché la 3-D manufacturing sta scatenando una vera rivoluzione industriale e si potrà assistere ad alcuni degli aspetti caratteristici della progettazione e della produzione per stampa 3-D.
(MO)

Meet The Owl With Eyes Like The Night Sky

 

November 20, 2014 | by Justine Alford

Photo credit: wildlife learning center

We all know it can be impossible not to immediately fall in love with cute, fluffy animals with big eyes that melt away your soul. But Zeus takes this to another level.

Zeus is a blind Western screech owl whose eyes truly look like twinkling galaxies. It's almost impossible to stop gazing into them.

His starry eyes are the result of clots of protein and blood pigment, but he also has cataracts. HIs condition is probably the result of an attack by a predator, but it's possible he also had a flying accident. He only has around 10% of his vision, so he cannot be released back into the wild and so stays at the Wildlife Learning Center in California where he receives a lot of TLC.

[Images: wildelifelearningcenter.com]