Pentagonal tiles pave the way towards organic electronics

New research paves way for next generation of ultra-small electronic devices.

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New research paves way for the nanoscale self-assembly of organic building blocks, a promising new route towards the next generation of ultra-small electronic devices.

Ring-like molecules with unusual five-fold symmetry bind strongly to a copper surface, due to a substantial transfer of charge, but experience remarkably little difficulty in sideways diffusion, and exhibit surprisingly little interaction between neighbouring molecules.  This unprecedented combination of features is ideal for the spontaneous creation of high-density stable thin films, comprising a pavement of these organic pentagonal tiles, with potential applications in computing, solar power and novel display technologies.

Currently, commercial electronics use a top-down approach, with the milling or etching away of inorganic material, such as silicon, to make a device smaller. For many years the computing power of a given size of computer chip has been doubling every eighteen months (a phenomenon known as Moore’s law) but a limit in this growth is soon expected.  At the same time, the efficiency of coupling electronic components to incoming or outgoing light (either in the generation of electricity from sunlight, or in the generation of light from electricity in flat-screen displays and lighting) is also fundamentally limited by the development of fabrication techniques at the nanometre scale (a nanometre being one billionth of a metre).

Researchers are therefore looking for ingenious solutions in the creation of ever smaller electronics. The field of nanotechnology is taking a bottom-up approach of creating electronics using naturally self-assembling organic components, such as polymers, which will be capable of spontaneously forming devices with the desired electronic or optical characteristics.

The latest findings are from scientists at the University of Cambridge and Rutgers University who are working on the development of new classes of organic thin films on surfaces.  By studying the fundamental forces at play in self-assembling thin films, they are developing the knowledge that will allow them to tailor these films into molecular-scale organic-electronic devices, creating smaller components than would ever be possible with conventional fabrication techniques.

Dr Holly Hedgeland, of the Department of Physics at the University of Cambridge, one of the co-authors of the paper, said: “With the semiconductor industry currently worth an estimated $249 billion per year there is a clear motivation towards a molecular scale understanding of innovative technologies that could come to replace those we use today.”

It is not simply the electronic properties of a molecule on a surface that will control its potential to form part of a device, but also whether it will move by itself into the required structural configuration and remain stable in that position even if the device becomes heated in use.

Molecules that are strongly bound to the substrate with a high degree of transfer of charge offer a range of new possibilities, though little is currently known of their behaviour. A number of organic molecules, usually featuring carbon rings across which electronic charge can conduct, potentially demonstrate the right electronic properties, but the long-range forces which will govern their self-assembly during the first phases of growth often remain a mystery.

Now the interdisciplinary team based in the Departments of Physics and Chemistry at the University of Cambridge, and the Department of Chemistry and Chemical Biology at Rutgers University, have reported the first dynamical measurements for a new class of organic thin film where cyclopentadienyl molecules (C₅H₅) receive significant electronic charge from the surface, yet diffuse easily across the surface and show interactions with each other that are much weaker than would typically be expected for the amount of charge transferred.

Hedgeland explained: “By coupling the experimental helium spin echo technique with advanced first-principles calculations, we were able to study the dynamic behaviour of a cyclopentendienyl layer on a copper surface, and to deduce that the charge transfer between the metal and the organic molecule was occurring in a counter-intuitive sense.”

Dr Marco Sacchi, of the Department of Chemistry at the University of Cambridge, who carried out the calculations that helped explain the startling new experimental results, said that “the key to the unique behavior of cyclopentadienyl lies in its pentagonal (five-fold) symmetry, which prevents it latching onto any one site within the triangular (three-fold) symmetry of the copper surface through directional covalent bonds, leaving it free to move easily from site to site; at the same time, its internal electronic structure is just one electron short of an extremely stable `aromatic’ configuration, encouraging a high degree of charge transfer from the surface and creating a strong non-directional ionic bond.”

The researchers’ findings, reported in Physical Review Letters today, Friday 06 May, highlight the potential of a new category of molecular adsorbate, which could fulfil all the criteria required for useful application.

Hedgeland concluded: “The unusual character of the charge transfer in this case prevents the large repulsive interactions between adjacent molecules that would otherwise have been expected, and hence should enable the formation of unusually high-density films. At the same time, the molecules remain highly mobile and yet strongly bound to the surface, with a large degree of thermal stability. In all, this is a combination of physical properties that offers huge potential benefit to the development of new classes of self-assembled organic films relevant for technological applications.”

Self-Organizing Nanotech Could Store 250 DVDs on One Coin-Size Surface

Sapphire crystals may be the next material to transform the electronics industry, thanks to nanotechnology researchers who have announced a new way of storing data that would fit the contents of 250 DVDs on a coin-sized surface. The study, published in Science, illustrates how nanoscale elements can organize themselves over a large sheet of semiconductor film. The researchers expect that when applied to electronic media, their discovery will improve the efficiency of data storage, savings which can then be transferred to improve other pieces of electronics besides just storage, like high-definition screens and solar cells.

Similar attempts have previously been made to improve data storage on semiconductor films, but have consistently failed because the polymers—which are known to link together, on their own, in precise patterns—lose their organized structure when the film being used increases in area, rendering them useless for storing memory. Lead researchers Ting Xu from the University of California at Berkeley and Thomas Russell from the University of Massachusetts at Amherst overcame this by layering the film of block copolymers onto the surface of a commercially available sapphire crystal. When the crystal is cut at an angle—a common procedure known as a miscut—and heated to 1,300 to 1,500 degrees Centigrade (2,372 to 2,732 degrees Fahrenheit) for 24 hours, its surface reorganizes into a highly ordered pattern of sawtooth ridges that can then be used to guide the self-assembly of the block polymers [Science Daily].

With this technique, the only limit to the size of an array of block copolymers is the size of the sapphire, Xu said. Once a sapphire is heated up and the pattern is created, the template could be reused. Both the crystals and the polymer chains could be obtained commercially, Xu said [PC World]. The researchers say the technology could make nearly perfect arrays of semiconductor material that are about 15 times denser than anything achieved previously [Reuters].

Using the technology, it might also be possible to achieve a high-definition picture with 3-nanometer pixels, potentially as large as a stadium JumboTron, Xu said. Another possibility is more dense photovoltaic cells that capture the sun’s energy more efficiently…. The new technology could create chip features just 3nm [nanometers] across, far outstripping current microprocessor manufacturing techniques, which at their best create features about 45nm across [PC World].

Large-scale synthesis of copper nanoparticles by chemically controlled reduction for applications of inkjet-printed electronics

With increasing demands for more economic routes to the manufacture of electronic devices incorporating polymer- based printed circuit boards (PCBs), various techniques for the fabrication of microelectronic devices, including screen printing, nano-imprinting, inkjet printing, and direct printing, are generating increasing interest. Among these methods, inkjet printing is considered to be an economical and highly functional technology for the microscale patterning of metallic traces in microelectronic devices. Conventional lithographic processes are well developed but include multiple steps that are time consuming, uneconomical, and not versatile towards corrective repatterning  However, the employment of inkjet printing can solve many of the problems in a facile and effective manner. The inkjet printing method allows for the patterning of conductive traces onto a substrate in one step, therefore reducing the time, cost, and space consumed and the toxic waste created during the manufacturing process. Nanomaterials are considered to be highly useful for application of materials through inkjet printing technology based on size-dependent mesoscopic properties such as enhanced dispersibility, melting point depression below that of the same bulk material based on more significant surface energy instability, and greater compatibility with various chemical and physical environments due more significant effects from interchangeable surface coatings. Inkjet printing technology employing conductive silver inks has been developed recently in order to manufacture low-cost disposable electronics, such as smart packaging, RF-ID tags, and digital calendars. However, silver as a conductive material has problems due to ion migration at relatively high-temperature and humidity conditions as well as cost-benefit issues compared to copper, which is significantly less expensive for virtually identical bulk conductivities. In this research, a large-scale (5 l), high-throughput (0.2 M) process for the synthesis of copper nanoparticles was developed using a modified polyol process that includes chemical reduction and hot addition. Furthermore, these copper nanoparticles were dispersed into an ether-based solvent, patterned onto various substrates through inkjet printing, and then converted into conductive metallic traces through a relatively low-temperature, reductive sintering process. The results are optimistic, however, there are some disadvantages of copper which must be overcome are that the copper ion is not easily reduced under mild reaction conditions and copper nanoparticles tend to be easily oxidized in air under ambient atmospheric conditions in comparison to noble metals like gold and silver.

To read more: Lee, Youngil; Choi, Jun-rak. “Large-scale synthesis of copper nanoparticles by chemically  controlled reduction for applications of inket-printed electronics” Nanotechnology. 19(2008).

Cost reduction in manufacturing of aerospace composites.

Advanced fibre reinforced composites are already extensively used in modern aircraft, due to advantages offered for weight reduction, durability, mechanical performance, etc. However, composite structures in aerospace are usually not associated with low costs. Traditional design methods are very time consuming, materials and production processes very expensive as well as labour intensive. To make full use of the potential of composites, a complete redesign of aircraft structures is necessary. Owing to qualification and certification procedures the introduction of low cost materials or low cost production processes is hindered. This paper describes the results of a collaborative research project aimed at achieving significant cost reductions in the manufacturing of advanced composites for aerospace applications. As part of the cost reduction objectives of the project, an innovative knowledge based engineering approach was followed during the preliminary design and analysis of the wingbox structure. In order to develop a realistic demonstrator, an analysis of an aerodynamically loaded full generic wingbox structure of a business jet type of aircraft was performed. The sizing of the ribs, front spar and rear spar as well as upper and lower skin panels were determined by means of different load cases further on, an optimisation of the wingbox with respect to its weight was performed by using a standard structural concept which is sizing based on the feasilisation methodology. The results are gratifying, since is possible to build them reducing costs, however there is more to research, since some of the process should be carried out in vacuum.

To read more,  look for the work of Van Hattum et al. “Cost reduction in manufacturing of aerospace composites” published  in Plastics, Rubber and Composites 2011 Vol 40, No. 2.

Selective gas sensing with pristine graphene

It has been known for some time that graphene can be used for detection of individual gas molecules adsorbed on its surface. Back in 2007, the discoverers of graphene, Andre Geim and Kostya Novoselov, already reported a graphene sensor that can detect just a single molecule of a toxic gas  In that work, the researchers have shown that gas molecules gently attach themselves to graphene without disrupting its chicken wire structure. They only add or take away electrons from graphene, which results in notable changes in its electrical conductance.


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High-performing supercapacitor electrodes made from self-organizing cobalt oxide nanowires

Commercially available supercapacitors store energy in two closely spaced layers with opposing charges and offer fast charge/discharge rates and the ability to sustain millions of cycles. Researchers have come up with various electrode materials – even as exotic as eggshell membranes – to improve the performance of supercapacitors, focussing mostly on porous carbon due to its high surface areas, tunable structures, good conductivities, and low cost.


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How buckyballs hurt cells

Using computer simulations, University of Calgary biochemist Peter Tieleman, post-doctoral fellow Luca Monticelli and colleagues modeled the interaction between carbon-60 molecules and cell membranes and found that the particles are able to enter cells by permeating their membranes without causing mechanical damage. Their results are published in the current Advance Online Publication of Nature Nanotechnology, the world’s leading nanotechnology journal.

“Buckyballs are already being made on a commercial scale for use in coatings and materials but we have not determined their toxicity,” said Tieleman, a Senior Scholar of the Alberta Heritage Foundation for Medical Research who specializes in membrane biophysics and biocomputing. “There are studies showing that they can cross the blood-brain barrier and alter cell functions, which raises a lot of questions about their toxicity and what impact they may have if released into the environment.”

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With Magnetic Nanoparticles, Scientists Remotely Control Neurons and Animal Behavior

Clusters of heated, magnetic nanoparticles targeted to cell membranes can remotely control ion channels, neurons and even animal behavior, according to a paper published by University at Buffalo physicists in Nature Nanotechnology.

"By developing a method that allows us to use magnetic fields to stimulate cells both in vitro and in vivo, this research will help us unravel the signaling networks that control animal behavior," says Arnd Pralle, PhD, assistant professor of physics in the UB College of Arts and Sciences and senior/corresponding author on the paper.

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Military nanotechnology - how worried should we be?

Most of the countries doesn't invest directly in military nanotechnology, most of them just invest in researches in other areas of nanotechnology such as electronics or materials.
But the USA DoD its investing in nanotechnology for defense, trying as always to be the most advanced country in military equipment.

The problem here its that this could affect the civilians, as we all now use have different military spots around cities and countries, most of the time military test involve explosions, imagine tons of nano particles flying around with this explosion polluting the air, the water and the fields, tons of this nano particles with unknown risks and affections to the human body

for mor information follow the next link

Article By Michael Berger, Copyright 2006 Nanowerk LLC

Effect of Interface Structure on Mechanical Properties of Advanced Composite Materials.

Advanced composite materials have the unique combination of outstanding mechanical properties of matrices and reinforcements. The reinforcement/matrix interface in composite materials forms in manufacturing processes and determines the performances of the composite materials. Some reinforcements may not be compatible with matrices in view of their physical and/or chemical properties, which causes premature failure of the composites. Recently, development of nanofiber modified matrices containing reactive graphitic nanofibers has been proposed to promote the wetting of the matrices to certain types of fiber reinforcements. In this paper, the effect of interface structures on the mechanical properties of fiber reinforced composite materials is discussed. Hybrid composite materials/structures are frequently subjected to thermal and mechanical fatigue loading. Aside from external mechanical loadings, thermal effect is identified as an important factor that determines the stress distribution in composite materials. During the curing process, adhesively bonded composite/metal laminate structures are held at elevated temperatures over 120 ◦C, very high residual stresses could build up because of the difference in coefficients of thermal expansion (CTE) for different materials. This thermal mismatch results in delamination or debonding of hybrid composite materials, which facilitates fatigue crack growth in the polymer/metal interface. Thermal cyclic stresses can also be generated from the fluctuation of ambient temperatures. Therefore, the stress state in a hybrid composite material is not only dependent on service conditions, but also affected by the materials processing parameters. The research has suggested that a porous oxide structure is likely to be very suitable for adhesive bonding because of the increase in interface area of nanoporous structure, which results in the high shear loading capability. However, the interface nanostructure remains to be revealed by further systematic study.

To read more go to ACS and search: Gan, Yong. Effect of Interface Strcuture on Mechanical properties of Advanced Composite Materials.  International Journal of Molecular Sciences. 2009, 10, 5115-5134.

Surface Topology of Advanced Alumina/Zirconia Composite Femoral Head as Compared with Commercial Femoral Heads Made of Monolithic Zirconia

Wear of bearing couples is one of the most important factors determining the longevity of a total hip implant. Ceramics have been used as bearing materials in hip joints with the expectation of wear reduction due to their smooth surfaces, low friction, and good wetting properties. All these properties should contribute to extend the in vivo lifetime of the hip joint. However, in vivo surface degradation of some zirconia ceramics has been reported, with the presence of asperities at the articular surfaces of the hip joint becoming a factor in precipitating degenerative changes. Recent topographic analyses of residual stress fields, conducted by confocal Raman and fluorescence spectroscopy on retrieved ceramic femoral heads, revealed clear changes in stress distribution with exposure time in vivo, as well as a possible migration of the polar position of maximum stress. Metastability of zirconia, and the potential effect of surface roughening arising from transformation of tetragonal-to-mono- clinic zirconia, represents a typical environmental effect strongly affecting the structural performance of a hip joint. From a materials science viewpoint, the environmental stability of zirconia has been found to strongly depend on grain size and on the amount and type of stabilizing element Some aspects of zirconia metastability are useful to improve the bulk fracture toughness of the joint material and, thus, have been welcomed by joint designers; however, the drawback is a potential embrittlement and a roughening of the bearing surface with aging in vivo. On the one hand, it is somewhat surprising that manu- facturers are still distributing monolithic zirconia ceramic femoral heads (e.g., in Japan), but fundamental information is lacking on the characteristics of degradation with no direct comparison made among zirconia ceramic heads manufactured by different makers. On the other hand, a new generation of alumina/zirconia composite material has recently become avail- able to the orthopedic community.

In this paper, they tested such an advanced composite femoral head with respect to the topologic and phase-stability response of its bearing surface to hydrothermal environment, in comparison with commercially available monolithic zirconia femoral heads. They found and important improvement in terms of stability in the aluminia/zirconia, specially in their response in OH ^– on the surface. This adds stability, because it inhibits the addition of oxygen to the vacancies of the crystal cell and hydrogen being interstiatilly located in the lattice.

To read more about it, search: Pezzotti, Giuseppe; Saito, Takuma; Takahashi, Yasuhito. “Surface topology of advanced aluminia/zirconia composite femoral head compared with commercial femroral heads of monolithic zirconia”.  ACS 94:(3) 2011. 945-950.

Nanoscale MRI

A research study titled ‘Coherent Sensing of a Mechanical Resonator with a Single Spin Qubit’ by Ania Bleszynski Jayich from the University of California - Santa Barbara (UCSB) brings the future quantum computer and nanoscale magnetic resonance imaging (MRI) one step closer to reality.

The study findings have been reported in the journal Science’s online version, Science Express. The study is based on a project at Harvard University where Jayich worked on an experiment that integrated diamond’s nitrogen-vacancy (NV) centers to nanomechanical resonators.

Jayich explained that diamond’s NV center is its unique defect, which demonstrates a quantum magnetic behavior called spin. The combination of a magnetic mechanical resonator and an individual spin in diamond forms a device capable of generating or selecting particular frequencies, paving the way to develop a novel nanoscale sensing technique for applications in technology and biology.

According to Jayich, one of the possible future applications of the novel technique is MRI on a nanoscale to image protein structures. Jayich informed that physics, which will enable the NV center to determine a resonator’s magnetic field, may help realize MRI on the nanoscale. It may develop more accurate MRI that can see more.

Jayich further said that there is a possibility for such a combination to be developed and used as a potential way to develop a quantum computer or a hybrid quantum system.

Jayich partnered on the work with J.G.E. Harris from Yale, Peter Rabl from the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Science and the Harvard University research team comprising Mikhail Lukin, Steven Bennett, Quirin Unterreithmeier and Shimon Kolkowitz.

Source: http://www.ia.ucsb.edu/pa/display.aspx?pkey=2655

New materials? liquid crystal behavior at smaller scales

A team of international scientists led by Juan J. de Pablo, a Professor of Chemical and Biological Engineering at the University of Wisconsin-Madison, has discovered that the manipulation of liquid crystals at the nanoscale can make the molecules they interact to self-assemble, thus paving the way to develop innovative materials with novel properties.

The results of the computer simulation study have been reported in the Nature journal. The study reveals the possibility of spontaneously forming new nanoscale morphologies using liquid crystals. The computational study simulated the characteristics of numerous rod-shaped liquid crystal molecules confined inside nano-sized liquid droplets. The study demonstrated that these liquid crystal molecules are capable of self-assembling when the droplets are cooled.

Professor de Pablo explained that the cooling process forms a liquid crystal phase because the liquid droplets become ordered upon cooling. What surprised the team was the behavior of the liquid crystallinity inside the droplets that stimulated the self-organization of water and other molecules present at the droplets’ interface, called surfactants, to form nanodomains.

This result shows that the interface molecules assume a homogeneous distribution when a liquid crystal is absent. However, the presence of a liquid crystal makes them to create an ordered nanostructure. de Pablo informed that the study results offer the possibility to create new structures and materials through the formation of these ordered nanophases by manipulating them either through surfactant concentration or droplet size.

Source: http://www.news.wisc.edu/20630

Advanced Technology and Aplications Through Boron Nitride Nanotubes

The innovative technology was jointly developed by the National Institute of Aerospace (NIA), the Jefferson Lab of the U.S. Department of Energy, and NASA Langley Research Center. As per the deal, BNNT LLC bought the intellectual property rights to synthesize BNNTs (Boron Nitride Nanotubes) used for commercial and scientific research.

BNNTs were first manufactured in 1995. Since then, they have been provided only in small amounts to other research laboratories. BNNT LLC plans to use sophisticated methods for increasing present production rates of BNNTs by a factor of 100.

BNNTs have a structure analogous to that of carbon nanotubes. These powerful versatile nanotubes demonstrate exotic properties that are useful in the research and commercial industry. They can be used to manufacture ceramic and polymer composites to produce a new range of aerospace components, batteries, thin coatings, armor, and dentistry products. They find use in fire retardant cabling, radiation shielding, electrical insulation, energy harvesting, sensors and robotics. Their biomedical applications include cancer treatment, and bone and nerve tissue regeneration.

BNNTs demonstrate piezoelectricity, which means they generate electricity due to pressure. They offer protection against ultraviolet and neutron radiation and can withstand extreme temperatures in the range of up to 800°C. NASA believes that BNNTs’ energy harvesting quality enables safer and longer aerospace mission by delivering auxiliary power for health monitoring systems and electronic devices.

According to Catharine Fay, BNNT Program Manager at NASA Langley Research Center, this technology will not only be used for the synthesis of BNNTs, but could also be used to produce other nanomaterials that are critical for mission applications.

Source: http://www.nasa.gov/centers/langley/news/releases/2012/12-031.html

Low-cost DNA Sequencing Device Using Nanopores

A team of researchers from the Yale University and Oak Ridge National Laboratory (ORNL) has developed nanopores with a radio-frequency electric field that can trap segments of biomolecules such as DNA.

This technique for high-speed genomic sequencing device shows promise in bringing down the cost of human genome sequencing. This work is part of an initiative by the National Institutes of Health’s National Human Genome Research Institute to promote research on reducing the cost of human genome sequencing.

The research team has reported its hypothesis, computation and experimental results in a paper titled ‘Tunable Aqueous Virtual Micropore,’ published in the journal, Small. The team demonstrated that a charged nano or micro particle like a DNA segment can be trapped in an aqueous virtual pore. The water enabled a stable environment to maintain the integrity of DNA, while the virtual walls let the DNA to traverse the nanopore without interplaying with physical walls.

They were able to manipulate the stability and size of a virtual nanopore by applying external electric fields. This was not possible with a physical nanopore. Later, they formed the aqueous nanopore embedded in water on the basis of a linear Paul trap that detains particles in the presence of an oscillating electric field. It also experimentally demonstrated the trapping functionality of the aqueous nanopore by proving water’s capability in stabilizing trapping mechanisms.

Project Director Predrag Krstic informed that since a single DNA polymer is passed through a synthetic nanopore, the team reads electric signals that detect DNA bases by physically detecting single molecules. If the low-cost technique becomes achievable, then genomic sequencing can be utilized in daily clinical treatments, Krstic concluded.

Source: http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20120424-00

Wound healing and anti-aging aplications for Chitosan nanoparticles

Chitosan is a naturally available biodegradable and non-toxic polysaccharide, which can stop infection in wounds and improve the wound-healing process by promoting the growth of skin cells. It has also been assessed as an additive for use in antimicrobial textiles for producing clothes for healthcare and other professionals.

Chitosan nanoparticles have demonstrated efficient antimicrobial activity against Escherichia coli and Staphylococcus saprophyticus. These materials find applications as a wound-healing material to prevent opportunistic infection and promote wound healing.

The research team utilized an ionic gelation process and sodium tripolyphosphate for producing their chitosan nanoparticles. In the ionic gelation process, bonds are formed between polymer strands by a cross-linking process. Under these conditions, the ionic gelation process eliminates the requirement for toxic chemicals or complicated preparative chemistry. Chitosan nanoparticles can also be produced in the presence of antimicrobial agents such as silver or copper ions. The team’s initial test results demonstrate the improved antimicrobial activity of the composite materials against two representative bacteria types.

The knowledge of the inhibition mechanism of the chiston nanoparticles against bacteria will be helpful in designing high-efficient antibacterial agents. The research team has also showed the skin regenerative properties of the chiston nanoparticles when materials were tested on skin cell keratinocytes and fibroblasts in the laboratory, paving the way to develop anti-aging skin care products.

Source : http://www.inderscience.com

Handle with Care, a new way of manipulating delicate nanoparticles

Scientists routinely trap and move nanoparticles in a solution with "optical tweezers"-a laser focused to a very small point. The tiny dot of laser light creates a strong electric field, or potential well, that attracts particles to the center of the beam. Although the particles are attracted into the field, the molecules of the fluid they are suspended in tend to push them out of the well. This effect only gets worse as particle size decreases because the laser's influence over a particle's movement gets weaker as the particle gets smaller. One can always turn up the power of the laser to generate a stronger electric field, but doing that can fry the nanoparticles too quickly to do anything meaningful with them-if it can hold them at all.

NIST researchers' new approach uses a control and feedback system that nudges the nanoparticle only when needed, lowering the average intensity of the beam and increasing the lifetime of the nanoparticle while reducing its tendency to wander. According to Thomas LeBrun, they do this by turning off the laser when the nanoparticle reaches the center and by constantly tracking the particle and moving the tweezers as the particle moves.

"You can think of it like attracting moths in the dark with a flashlight," says LeBrun. "A moth is naturally attracted to the flashlight beam and will follow it even as the moth flutters around apparently at random. We follow the fluttering particle with our flashlight beam as the particle is pushed around by the neighboring molecules in the fluid. We make the light brighter when it gets too far off course, and we turn the light off when it is where we want it to be. This lets us maximize the time that the nanoparticle is under our control while minimizing the time that the beam is on, increasing the particle's lifetime in the trap."

Using this method at constant average beam power, 100-nanometer gold particles remained trapped 26 times longer than had been seen in previous experiments. Silica particles 350 nanometers in diameter lasted 22 times longer, but with the average beam power reduced by 33 percent. LeBrun says that their approach should be able to be combined with other techniques to trap and hold even smaller nanoparticles for extended periods without damaging them.

Source: http://www.nist.gov/pml/div683/tweezers-050212.cfm

New Dental anti-bacterial Composite

Scientists using nanotechnology at the University of Maryland School of Dentistry have created the first cavity-filling composite that kills harmful bacteria and regenerates tooth structure lost to bacterial decay.

Rather than just limiting decay with conventional fillings, the new composite is a revolutionary dental weapon to control harmful bacteria, which co-exist in the natural colony of microorganisms in the mouth, says professor Huakun Xu.
"Tooth decay means that the mineral content in the tooth has been dissolved by the organic acids secreted by bacteria residing in biofilms or plaques on the tooth surface. These organisms convert carbohydrates to acids that decrease the minerals in the tooth structure," says Xu, director of the Division of Biomaterials and Tissue Engineering in the School's Department of Endodontics, Prosthodontics and Operative Dentistry.

The researchers also have built antibacterial agents into primer used first by dentists to prepare a drilled-out cavity and into adhesives that dentists spread into the cavity to make a filling stick tight to the tissue of the tooth. "The reason we want to get the antibacterial agents also into primers and adhesives is that these are the first things that cover the internal surfaces of the tooth cavity and flow into tiny dental tubules inside the tooth," says Xu. The main reason for failures in tooth restorations, says Xu, is secondary caries or decay at the restoration margins. Applying the new primer and adhesive will kill the residual bacteria, he says.

Fillings made from the School of Dentistry's new nanocomposite, with antibacterial primer and antibacterial adhesive, should last longer than the typical five to 10 years. Xu says a key component of the new nanocomposite is calcium phosphate nanoparticles that regenerate tooth minerals. The antibacterial component has a base of quaternary ammonium and silver nanoparticles along with a high pH, also, the alkaline pH limits acid production by tooth bacteria.

"The bottom line is we are continuing to improve these materials and making them stronger in their antibacterial and remineralizing capacities as well as increasing their longevity," Xu says.

Source: Unversity of Maryland http://www.marylandday.umd.edu/

Tiny 3-D Chips

MIT researchers have developed a MEMS device that allows 3-D sensing on only one chip.

Commonly, two dimensional MEMS devices are manufactured for detecting acceleration processes. Generally, researchers thought that devising three dimensional MEMS involves costly and complicated processes to merge many devices with accurate orientation.

Many researchers attempted to develop three dimensional devices using polymers. These devices were fabricated using lithography and were used in cogs, micro-turbines and small gears.

A postdoctoral researcher from Department of Aeronautics and Astronautics, Fabio Fachin said that silicon, due to its resistance to temperature and durability, can be replaced to polymers. However, he added that the fabrication process is difficult in silicon.

For fabrication, the engineers used a deep reactive ion etching method. Using this method, two dimensional structures are carved into a wafer. Even this method produces only a partial 3-D configuration, because the structures rise over the surface of the chip. Further, the MEMS engineers fabricated the cantilevers or small two-dimensional bridges over the surface of the chip. Finally, with high accuracy, a little force was employed to fix the bridge into the structure.

The team used a residual stress, to overcome the difficulty in the final step of the process. In every bridge structure lays a residual stress even after the disappearance of the applied force. Fachin’s group of researchers followed a previous study, which elaborates about microbeam configurations and formed equational relationship between the residual stress and the flexibility and geometry of a thin material. These calculations were used to modify the bridges to produce the required shape. This analytical tool was used to configure three dimensional devices.

An Associate Professor in aeronautics and astronautics of MIT, Brian Wardle and
Stefan Nikles from MEMSIC co worked with Fachin to develop three dimensional devices.

Source: http://web.mit.edu/newsoffice/2012/three-dimensional-microchips-0228.html

Nanopartículas para tratar tumores de manera no invasiva.

Sotiris E. Pratsinis, profesor de la ETH en Zurich en Suiza, ha sido un investigador visitante desde enero del año en curso en la Uniersität Duisbur-Essen (UDE) y desempeña investigación en nanopartículas.

Pratsinis ha seleccionado la UDE junto con el equipo de investigacion del Dr Markus, profesor de tecnología de procesamiento de nanopartículas en el Institut für Verbrennung und Gasdynamik. El ganó el premio de investigación de la fundación Alexander Von Humboldt, claro, junto con el premio monetario de 60,000.00 euros, y también ha tenido la oportunidad de trabajar en proyectos específicos en universidades de Alemania.

En la ETH en Zurich, Pratsinis se enfoca en la síntesis de combustión de nanomateriales, tecnología de partículas y transferencia de masas. En la UDE, su área de enfoque es conducir estudios de simulaciones por revestimiento en fase gaseosa de las nanoparticulas, esto para entender el mecanismo de enlace y la influencia de las condiciones de síntesis en sus propiedades generales, asi como caracteristicas y propiedades en aplicaciones.

El equipo de Pratsinis ha reconocido la eficiencia de nanopartículas en el proceso de sanación mediante un bio-detector inventado en 2010. El sensor fue producido a partir de cerámicas mixtas sintetizadas por fuego depositadas directamente en electrodos de oro. Este sensor es capaz de detectar diabetes, esto midiendo el contenido de acetona en las exhalaciones del paciente. La eficiencia de entrega del fármaco de las nanopartículas depende de como sean revestidas. Estudios conducidos en la ETH en Zurich demostraron la capacidad de las nanopartículas de detectar células cancerígenas. Pronto, las nanopartículas puede que sean enlazadas a las células cancerígenas, para después destruir dichas células usando radiación electromagnética, ademas, abriendo así el camino para destruir tumores de una forma no invasiva.

Fuente: http://www.uni-due.de/en/index.php