#UT Dallas nanotechnology research leads to super-elastic conducting fibers Abstract: An international research team based at The University of Texas at Dallas has made electrically conducting fibers that can be stretched reversibly to over 14 times their initial length and
whose electrical conductivity increases 200-fold when stretched. The research team is using the new fibers to make artificial muscles,
as well as capacitors whose energy storage capacity increases about tenfold when the fibers are stretched. Fibers and cables derived from the invention might one day be used as interconnects for super-elastic electronic circuits;
robots and exoskeletons having great reach; morphing aircraft; giant-range strain sensors; failure-free pacemaker leads;
and super-stretchy charger cords for electronic devices. In a study published in the July 24 issue of the journal Science,
the scientists describe how they constructed the fibers by wrapping lighter-than-air, electrically conductive sheets of tiny carbon nanotubes to form a jellyroll-like sheath around a long rubber core.
The new fibers differ from conventional materials in several ways. For example, when conventional fibers are stretched,
the resulting increase in length and decrease in cross-sectional area restricts the flow of electrons through the material.
But even a"giant"stretch of the new conducting sheath-core fibers causes little change in their electrical resistance
said Dr. Ray Baughman, senior author of the paper and director of the Alan G. Macdiarmid Nanotech Institute at UT Dallas. One key to the performance of the new conducting elastic fibers is the introduction of buckling into the carbon nanotube
sheets. Because the rubber core is stretched along its length as the sheets are being wrapped around it,
when the wrapped rubber relaxes, the carbon nanofibers form a complex buckled structure, which allows for repeated stretching of the fiber."
"Think of the buckling that occurs when an accordion is compressed, which makes the inelastic material of the accordion stretchable,
"said Baughman, the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas."We make the inelastic carbon nanotube sheaths of our sheath-core fibers super stretchable by modulating large buckles with small buckles,
so that the elongation of both buckle types can contribute to elasticity. These amazing fibers maintain the same electrical resistance,
even when stretched by giant amounts, because electrons can travel over such a hierarchically buckled sheath as easily as they can traverse a straight sheath."
"Dr. Zunfeng Liu, lead author of the study and a research associate in the Nanotech Institute,
said the structure of the sheath-core fibers"has further interesting and important complexity.""Buckles form not only along the fiber's length,
but also around its circumference.""Shrinking the fiber's circumference during fiber stretch causes this second type of reversible hierarchical buckling around its circumference,
even as the buckling in the fiber direction temporarily disappears, "Liu said.""This novel combination of buckling in two dimensions avoids misalignment of nanotube
and rubber core directions, enabling the electrical resistance of the sheath-core fiber to be insensitive to stretch."
"By adding a thin overcoat of rubber to the sheath-core fibers and then another carbon nanotube sheath,
the researchers made strain sensors and artificial muscles in which the buckled nanotube sheaths serve as electrodes
and the thin rubber layer is a dielectric, resulting in a fiber capacitor. These fiber capacitors exhibited a capacitance change of 860 percent
when the fiber was stretched 950 percent.""No presently available material-based strain sensor can operate over nearly as large a strain range,
"Liu said. Adding twist to these double-sheath fibers resulted in fast, electrically powered torsional
--or rotating--artificial muscles that could be used to rotate mirrors in optical circuits or pump liquids in miniature devices used for chemical analysis,
said Dr. Carter Haines BS'11, Phd'15, a research associate in the Nanotech Institute and an author of the paper.
In the laboratory, Nan Jiang, a research associate in the Nanotech Institute, demonstrated that the conducting elastomers can be fabricated in diameters ranging from the very small--about 150 microns,
or twice the width of a human hair--to much larger sizes, depending on the size of the rubber core."
"Individual small fibers also can be combined into large bundles and plied together like yarn or rope,
"she said.""This technology could be well-suited for rapid commercialization, "said Dr. Raquel Ovalle-Robles MS'06 Phd'08, an author on the paper and chief research and intellectual properties strategist at Lintec of America's Nanoscience & Technology Center."
"The rubber cores used for these sheath-core fibers are inexpensive and readily available, "she said."
"The only exotic component is the carbon nanotube aerogel sheet used for the fiber sheath.""Last year, UT Dallas licensed to Lintec of America a process Baughman's team developed to transform carbon nanotubes into large-scale structures, such as sheets.
Lintec opened its Nanoscience & Technology Center in Richardson, Texas, less than 5 miles from the UT Dallas campus,
to manufacture carbon nanotube aerogel sheets for diverse applications.#####The Science research was supported by the Air force Office of Scientific research, the Robert A. Welch Foundation, the U s army, the National institutes of health, the National Science Foundation and the Office of Naval Research.
Several funding sources from China and Brazil also contributed. In addition to Baughman, Liu, Haines, Jiang and Ovalle-Robles, paper authors based at UT Dallas'Nanotech Institute are research scientists Dr. Shaoli Fang and Dr. Marcio Lima,
and research associates Dr. Xavier Lepro and Dr. Jiangtao Di. Contributors based in the UT Dallas Department of Mechanical engineering include Dr. Hongbing Lu
professor; Dr. Dong Qian, associate professor; and Xuemin Wang, research assistant. Researchers also contributed from universities in Florida, China and Brazil l
#Reshaping the solar spectrum to turn light to electricity: UC Riverside researchers find a way to use the infrared region of the sun's spectrum to make solar cells more efficient A huge gain in this direction has now been made by a team of chemists at the University of California,
Riverside that has found an ingenious way to make solar energy conversion more efficient. The researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in"upconverting"photons in the visible and near-infrared regions of the solar spectrum."
"The infrared region of the solar spectrum passes right through the photovoltaic materials that make up today's solar cells,
"explained Christopher Bardeen, a professor of chemistry. The research was a collaborative effort between him
and Ming Lee Tang, an assistant professor of chemistry.""This is energy lost, no matter how good your solar cell.
The hybrid material we have come up with first captures two infrared photons that would normally pass right through a solar cell without being converted to electricity,
then adds their energies together to make one higher energy photon. This upconverted photon is absorbed readily by photovoltaic cells,
generating electricity from light that normally would be wasted.""Bardeen added that these materials are essentially"reshaping the solar spectrum
"so that it better matches the photovoltaic materials used today in solar cells. The ability to utilize the infrared portion of the solar spectrum could boost solar photovoltaic efficiencies by 30 percent or more.
In their experiments, Bardeen and Tang worked with cadmium selenide and lead selenide semiconductor nanocrystals.
The organic compounds they used to prepare the hybrids were diphenylanthracene and rubrene. The cadmium selenide nanocrystals could convert visible wavelengths to ultraviolet photons,
while the lead selenide nanocrystals could convert near-infrared photons to visible photons. In lab experiments
the researchers directed 980-nanometer infrared light at the hybrid material, which then generated upconverted orange yellow fluorescent 550-nanometer light,
almost doubling the energy of the incoming photons. The researchers were able to boost the upconversion process by up to three orders of magnitude by coating the cadmium selenide nanocrystals with organic ligands,
providing a route to higher efficiencies.""This 550--nanometer light can be absorbed by any solar cell material,
"Bardeen said.""The key to this research is the hybrid composite material--combining inorganic semiconductor nanoparticles with organic compounds.
Organic compounds cannot absorb in the infrared but are good at combining two lower energy photons to a higher energy photon.
By using a hybrid material, the inorganic component absorbs two photons and passes their energy on to the organic component for combination.
The organic compounds then produce one high-energy photon. Put simply, the inorganics in the composite material take light in;
the organics get light out.""Besides solar energy, the ability to upconvert two low energy photons into one high energy photon has potential applications in biological imaging, data storage and organic light-emitting diodes.
Bardeen emphasized that the research could have wide-ranging implications.""The ability to move light energy from one wavelength to another, more useful region, for example,
from red to blue, can impact any technology that involves photons as inputs or outputs,
"he said.#####The research was supported by grants from the National Science Foundation and the US ARMY.
The research was conducted also by the following coauthors on the research paper: Zhiyuan Huang (first author), Xin Li, Melika Mahboub, Kerry M. Hanson, Valerie M. Nichols and Hoang Le.
Tang's group helped design the experiments and provided the nanocrystals. The UCR Office of Technology Commercialization has filed a provisional patent on the technology y
#Laboratorial Performance of Nanocomposite Membrane Improved in Water purification The membrane is able to separate dye components from a large amount of water.
In case this product is produced at large scale, it can be used in various industries, including textile, dye production and foodstuff to purify dye pollutants.
Creating the possibility to purify and recycle water and industrial water is an important step towards the conservation of water reservoirs after the consumption
and water shortage crisis. Membrane purification and separation method is known as a very effective and optimum method
which has been confirmed by many researchers. The aim of this research was to produce a polymeric nanocomposite membrane
and to modify its performance. The membrane was tested to purify water and separate dye pollutants as one of the most important pollutions in many industries.
The polymeric membrane is made of polyethersulfone nanocomposite and multiwalled carbon nanotubes were used in its structure. Carbon nanotubes have unique properties
and they have numerous applications in the production of nanocomposite membranes. However, the heterogeneous distribution of nanoparticles in the structure of the membrane polymer can be considered as an important problem.
The surface of nanoparticles was coated with polystyrene sulfonate as a new approach to improve the homogenous distribution of nanoparticles in polymer.
This method significantly affects the distribution of nanoparticles in the membrane polymer and it modifies the structure and the separation performance.
Results of the research have been published in Journal of Hazardous Materials vol. 298, issue 1, 2015, pp. 111-121 1
#Perfect Optical Properties in Production of Aluminum oxide Colloid Nanoparticles Iranian researchers produced nanoparticles in forms of colloids which have very good optical properties and conserve their stability for a long time.
Perfect Optical Properties in Production of Aluminum oxide Colloid Nanoparticles Aluminum oxide colloid nanoparticles have applications in various fields
and industries, including laser, solar cells, production of transistors and nanomedicine. The colloid form of these particles have very interesting properties and characteristics,
and their size, shape and properties at nanometric scale can be controlled very well. According to the researchers, the stability of nanomaterials in long period is one of the most important challenges in the production of nanomaterials.
The large difference between surface and volume energy of nanoparticles is the cause of this problem.
This energy gap, in addition to other parameters such as density difference in electrical charges and type and density of surface atoms,
which are affected by the morphology of the particles, prevent the easily formation of a stable colloid.
These parameters in addition to other obstacles such as the creation of stable chemical complexes in an uncontrolled situation prevents the formation of alumina nanoparticles in form of colloid,
and therefore it is very important to select a certain method to obtain the desirable results.
The produced nanoparticles have very high stability and appropriate optical properties and they can be used in the production of optical devices.
Taking into account the desirable optical properties of the produced nanoparticles, it is expected that an important step is taken in the development of nanotechnology in the field of medicine,
electronics and photonics after passing the required tests and obtaining mass-production of these nanoparticles.
Results of the research have been published in Journal of the American Ceramic Society, vol. 98, issue 6, 2015, pp. 1818-1822.##
###For more information, please click here Copyright Fars News agency If you have a comment, please Contact us.
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content n
#Detecting small metallic contaminants in food via magnetization: A practical metallic-contaminant detecting system using three high-Tc RF superconducting quantum interference devices (SQUIDS) Abstract:
The detection of metallic contaminants in foods is important for our health and safety. However, existing inspection methods have limitations.
For instance, the X-ray radiation method cannot detect contaminants with sizes smaller than 1 mm with current practical X-ray levels,
and it cannot be applied for the inspection of foods that have lactic acid bacteria because X-ray radiation causes ionization of such foods.
In this context, recently, researchers at the Department of Environmental and Life sciences at Toyohashi Tech have developed a practical magnetic metallic contaminant detector using three high-Tc RF superconducting quantum interference devices
(SQUIDS) for food inspection. The detection technique is based on recording the remnant magnetic field of a contaminant using SQUID sensors.
SQUID is a high-sensitivity magnetic sensor based on the superconductivity phenomenon. In the process, a strong magnetic field is applied to food to magnetize the metal fragments inside,
and subsequently, these metals, if they are contained in the food, can be detected by sensing their magnetic fields using SQUID sensors.
This method is advantageous in the sense that it is both safe and provides a high resolution.
Professor Tanaka, whose team has developed the method, says,"We have developed an inspection system that permits contaminant detection in a food package with a height of 100 mm with three high-Tc RF SQUIDS.
To accurately detect even smaller metallic fragments digital filters have also been used to improve the signal-to-noise ratio.
The target size of the metallic contaminant in food with a stand-off distance of 100 mm is 0. 5 mm."
"He continued, "To reduce the impact of noise as much as possible, the sensor is placed inside a square metallic box designed such that food can be tested as it passes through this box.
The box is made of 2-mm iron-nickel alloy plates. Magnetic fields have strong affinities to this iron-nickel alloy.
Thus, magnetic fields around the sensor are concentrated in the walls of this box.""In experiments, the developed system was able to clearly detect a steel ball with a diameter as small as 0. 3 mm.
The system was robust and not affected by electromagnetic waves from nearby mobile phones or from the motion of nearby steel objects.
Therefore, the system is a promising tool to detect contaminants in practical situations, and it can significantly aid in enhancing consumer health and safety.##
###This study is featured in the July 2015 issue of TUT Research: e-newsletter from Toyohashi University of Technology:
www. tut. ac. jp/english/newsletter/contents/2015/01/features/features. html TUT Research is an online quarterly magazine to introduce cutting-edge research in Toyohashi Tech.
Reference: S. Tanaka, T. Ohtani, Y. Narita, Y. Hatsukade, and S. Suzuki,"Development of metallic contaminant detection system using RF High-Tc SQUIDS for food inspection,"IEEE Trans.
Appl. Supercond. Vol. 25, no. 3 june 2015, Art. ID. 1601004 4
#Meet the high-performance single-molecule diode: Major milestone in molecular electronics scored by Berkeley Lab and Columbia University team"Using a single symmetric molecule, an ionic solution and two gold electrodes of dramatically different exposed surface areas,
we were able to create a diode that resulted in a rectification ratio, the ratio of forward to reverse current at fixed voltage, in excess of 200,
which is a record for single-molecule devices, "says Jeff Neaton, Director of the Molecular Foundry, a senior faculty scientist with Berkeley Lab's Materials sciences Division and the Department of physics at the University of California Berkeley,
and a member of the Kavli Energy Nanoscience Institute at Berkeley (Kavli ENSI.""The asymmetry necessary for diode behavior originates with the different exposed electrode areas and the ionic solution,
"he says.""This leads to different electrostatic environments surrounding the two electrodes and superlative single-molecule device behavior."
"With"smaller and faster"as the driving mantra of the electronics industry, single-molecule devices represent the ultimate limit in electronic miniaturization.
In 1974, molecular electronics pioneers Mark Ratner and Arieh Aviram theorized that an asymmetric molecule could act as a rectifier, a one-way conductor of electric current.
Since then, development of functional single-molecule electronic devices has been a major pursuit with diodes-one of the most widely used electronic components-being at the top of the list.
A typical diode consists of a silicon p-n junction between a pair of electrodes (anode and cathode) that serves as the"valve"of an electrical circuit,
directing the flow of current by allowing it to pass through in only one"forward"direction.
The asymmetry of a p-n junction presents the electrons with an"on/off"transport environment.
Scientists have fashioned previously single-molecule diodes either through the chemical synthesis of special asymmetric molecules that are analogous to a p-n junction;
or through the use of symmetric molecules with different metals as the two electrodes. However, the resulting asymmetric junctions yielded low rectification ratios,
and low forward current. Neaton and his colleagues at Columbia University have discovered a way to address both deficiencies."
"Electron flow at molecular length-scales is dominated by quantum tunneling, "Neaton explains.""The efficiency of the tunneling process depends intimately on the degree of alignment of the molecule's discrete energy levels with the electrode's continuous spectrum.
In a molecular rectifier, this alignment is enhanced for positive voltage, leading to an increase in tunneling,
and is reduced for negative voltage. At the Molecular Foundry we developed an approach to accurately compute energy-level alignment
and tunneling probability in single-molecule junctions. This method allowed myself and Zhenfei Liu to understand the diode behavior quantitatively."
"In collaboration with Columbia University's Latha Venkataraman and Luis Campos and their respective research groups, Neaton and Liu fabricated a high-performing rectifier from junctions made of symmetric molecules with molecular resonance
in nearly perfect alignment with the Fermi electron energy levels of the gold electrodes. Symmetry was broken by a substantial difference in the size of the area on each gold electrode that was exposed to the ionic solution.
Owing to the asymmetric electrode area, the ionic solution, and the junction energy level alignment, a positive voltage increases current substantially;
a negative voltage suppresses it equally significantly.""The ionic solution, combined with the asymmetry in electrode areas, allows us to control the junction's electrostatic environment simply by changing the bias polarity,
"Neaton says.""In addition to breaking symmetry, double layers formed by ionic solution also generate dipole differences at the two electrodes,
which is the underlying reason behind the asymmetric shift of molecular resonance. The Columbia group's experiments showed that with the same molecule and electrode setup,
a nonionic solution yields no rectification at all.""The Berkeley Lab-Columbia University team believes their new approach to a single-molecule diode provides a general route for tuning nonlinear nanoscale-device phenomena that could be applied to systems beyond single-molecule junctions
and two-terminal devices.""We expect the understanding gained from this work to be applicable to ionic liquid gating in other contexts,
and mechanisms to be generalized to devices fabricated from two-dimensional materials, "Neaton says.""Beyond devices, these tiny molecular circuits are petri dishes for revealing
and designing new routes to charge and energy flow at the nanoscale. What is exciting to me about this field is its multidisciplinary nature-the need for both physics and chemistry-and the strong beneficial coupling between experiment and theory."
"With the increasing level of experimental control at the single-molecule level, and improvements in theoretical understanding and computational speed and accuracy, we're just at the tip of the iceberg with
what we can understand and control at these small length scales.""Neaton, Venkataraman and Campos are the corresponding authors of a paper describing this research in Nature Nanotechnology.
The paper is titled"Single-molecule diodes with high rectification ratios through environmental control.""Other co-authors are Brian Capozzi, Jianlong Xia, Olgun Adak, Emma Dell, Zhen-Fei Liu and Jeffrey Taylor r
#Sol-gel capacitor dielectric offers record-high energy storage If the material can be scaled up from laboratory samples,
devices made from it could surpass traditional electrolytic capacitors for applications in electromagnetic propulsion, electric vehicles and defibrillators.
Capacitors often complement batteries in these applications because they can provide large amounts of current quickly.
The new material is composed of a silica sol-gel thin film containing polar groups linked to the silicon atoms and a nanoscale self-assembled monolayer of an octylphosphonic acid,
which provides insulating properties. The bilayer structure blocks the injection of electrons into the sol-gel material
providing low leakage current, high breakdown strength and high energy extraction efficiency.""Sol-gels with organic groups are well known
and fatty acids such as phosphonic acids are noted well known Joseph Perry, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of technology."
"But to the best of our knowledge, this is the first time these two types of materials have been combined into high-density energy storage devices."
"The research, supported by the Office of Naval Research and the Air force Office of Scientific research, was reported July 14 in the journal Advanced Energy Materials.
The need for efficient, high-performance materials for electrical energy storage has been growing along with the ever-increasing demand for electrical energy in mobile applications.
Dielectric materials can provide fast charge and discharge response, high energy storage, and power conditioning for defense, medical and commercial applications.
But it has been challenging to find a single dielectric material able to maximize permittivity, breakdown strength, energy density and energy extraction efficiency.
Perry and colleagues in Georgia Tech's Center for Organic photonics and Electronics (COPE) had been working on other capacitor materials to meet these demands
but were satisfied not with the progress. The hybrid sol-gel materials had shown potential for efficient dielectric energy storage because of their high orientational polarization under an electric field,
so the group decided to pursue these materials for the new capacitor applications. Using an aluminized mylar film coated with the hybrid sol-gel capacitor material,
they showed that the capacitor could be rolled and rerolled several times while maintaining high energy density, demonstrating its flexibility.
But they were still seeing high current leakage. To address that, they deposited a nanoscale self-assembled monolayer of n-octylphosphonic acid on top of the hybrid sol-gel.
Less than a nanometer thick the monolayer serves as an insulating layer.""Our silica sol-gel is a hybrid material
because it has polar organic groups attached to the silica framework that gives the sol-gel a high dielectric constant,
and in our bilayer dielectric, the n-octylphosphonic acid groups are inserted between the sol-gel layer
and the top aluminum layer to block charge injection into the sol-gel, "Perry explained."
"It's really a bilayer hybrid material that takes the best of both reorientation polarization and approaches for reducing injection and improving energy extraction."
"In their structures, the researchers demonstrated maximum extractable energy densities up to 40 joules per cubic centimeter, an energy extraction efficiency of 72 percent at a field strength of 830 volts per micron,
and a power density of 520 watts per cubic centimeter. The performance exceeds that of conventional electrolytic capacitors and thin-film lithium ion batteries,
though it doesn't match the lithium ion battery formats commonly used in electronic devices and vehicles.""This is the first time I've seen a capacitor beat a battery on energy density,
"said Perry.""The combination of high energy density and high power density is uncommon in the capacitor world."
"Researchers in Perry's lab have been making arrays of small sol-gel capacitors in the lab to gather information about the material's performance.
The devices are made on small substrates about an inch square.""What we see when we apply an electric field is that the polarization response
-which measures how much the polar groups line up in a stable way with the field-behaves in a linear way,
"said Perry.""This is what you want to see in a capacitor dielectric material.""The next step will be to scale up the materials to see if the attractive properties transfer to larger devices.
If that is successful, Perry expects to commercialize the material through a startup company or SBIR project."
"The simplicity of fully solution-based processes for our dielectric material system provides potential for facile scale up and fabrication on flexible platforms,
"the authors wrote in their paper.""This work emphasizes the importance of controlling the electrode-dielectric interface to maximize the performance of dielectric materials for energy storage application
#Self-assembling, biomimetic membranes may aid water filtration Abstract: A synthetic membrane that self assembles and is produced easily may lead to better gas separation,
water purification, drug delivery and DNA recognition, according to an international team of researchers. This biomimetic membrane is composed of lipids--fat molecules
--and protein-appended molecules that form water channels that transfer water at the rate of natural membranes,
and self-assembles into 2-dimensional structures with parallel channels.""Nature does things very efficiently
and transport proteins are amazing machines present in biological membranes, "said Manish Kumar, assistant professor of chemical engineering, Penn State."
"They have functions that are hard to replicate in synthetic systems.""The researchers developed a second-generation synthetic water channel that improves on earlier attempts to mimic aquaporins-natural water channel proteins--by being more stable and easier to manufacture.
The peptide-appended pillar 5 arenes (PAP) are also more easily produced and aligned than carbon nanotubes, another material under investigation for membrane separation.
Kumar and co-authors report their development in a recent issue of the Proceedings of the National Academy of Science."
"We were surprised to see transport rates approaching the'holy grail'number of a billion water molecules per channel per second,
"said Kumar.""We also found that these artificial channels like to associate with each other in a membrane to make 2-dimentional arrays with a very high pore density."
"The researchers consider that the PAP membranes are an order of magnitude better than the first-generation artificial water channels reported to date.
The propensity for these channels to automatically form densely packed arrays leads to a variety of engineering applications."
"The most obvious use of these channels is perhaps to make highly efficient water purification membranes,
"said Kumar.#####Other researchers on this project include Yue-xiao Shen, Mustafa Erbakan and Patrick Saboe, graduate students in chemical engineering;
Peter Butler, professor of biomedical engineering; Sheereen Majd, assistant professor of biomedical engineering and You Jung Kang, graduate student in bioengineering, all at Penn State.
Also participating were Aleksei Aksimentiev, associate professor of physics and Karl Decker, graduate student, University of Illinois at Urbana-Champaign;
Junli Hou and Wen Si, Fundan University, Shanghai, China; Thomas Walz, professor of cell biology and Rita de Zorzi, postdoctoral fellow, Harvard Medical school.
The National Science Foundation, the U s army Corps of Engineers, an Extreme Science and Engineering Discovery Allocation and the Blue waters petascale supercomputer system at University of Illinois supported parts of this research h
Overtext Web Module V3.0 Alpha
Copyright Semantic-Knowledge, 1994-2011