Cool rollerball-pen ink to draw circuits!

Two professors from the University of Illinois have combined their talents to use the idea of printing circuits onto non-standard materials by developing a conductive ink that can be used in a traditional roller ball ink pen to draw circuits by hand onto paper and other porous materials. In their paper published in Advanced Materials, team leads Jennifer Lewis, Jennifer Bernhard and colleagues describe how they were able to make a type of ink from silver nanoparticles that would remain a liquid while in the pen, but would dry like regular ink once applied. The pen could was then used to draw a functioning LCD display and an antenna.

To make the ink, the team produced silver nanoparticles by reducing a silver nitrate solution along with an acid to prevent the particles from growing too large. Afterwards the acid was removed and the viscosity of the ink modified using hydroxyethyl cellulose to get just the right consistency. The result is a sort of liquid metal that dries on contact and which can be used to conduct electricity, hence its ability to be used in the creation of a circuit.

  

Up till now, most research on printing circuits onto non-standard materials, such as paper, have been done using inkjet printers or even airbrushes. This new approach would allow circuits to be drawn quicker and much cheaper, or even on-the-fly, as no other hardware is needed. Such a low cost device might create a market for throwaway circuits or even super cheap batteries. Paper was used in the study because it is considered to be the most suitable non-standard material for printing circuits due to its wide availability, low cost, ability to be bent and shaped, and the fact that it is biodegradable.

The paper used in study was folded after testing to see how the circuit would hold up, and discovered it took folding several thousand times before the ink pathways were broken.

The team next plans to look into other types of materials that might be used to make conductive ink for their pen, hoping to open up the door to all kinds of inks that can be used for a wide variety of purposes.

Nanotechnology leads to massive increase in memory capacity

There are two very exciting recent advances in nanotechnology may soon result in a massive increase in memory capacities of your DVDs and iPods. Researchers at the Centre for Micro-Photonics at the Swinburne University of Technology in Victoria, Australia, created a new material that could lead to new discs that can store 10,000 times more data than your average DVDs.

The material is made up of layers of gold nanorods suspended in clear plastic spun flat on a glass substrate. Multiple data patterns can be written and read within the same area in the material without interfering with each other. Using three wavelengths and two polarizations of light, the Australian researchers have written six different patterns within the same area. They've further increased the storage density to 1.1 terabytes per cubic centimeter by writing data to stacks of as many as 10 nanorod layers.

Also Berkeley researcher  created a physical memory cell composed of an iron nanoparticle that can be moved back and forth in a nanotube. The position of the iron particle represents the state of the bit, which leads to very dense and highly stabile memory arrays, resulting in very long lifetime.

Silicon Optical Chips by nanofabrication tools

In an effort to make it easier to build inexpensive, next-generation silicon-based electro-optical chips, which allow computers to move information with light and electricity, a University of Washington photonics professor, Dr. Michael Hochberg and his research team are developing design tools and using commercial nanofabrication tools.

Silicon optical chips are critical to the Air Force because of their size, weight, power, rapid cycle time, program risk reduction and the improvements they can offer in data communications, lasers and detectors. 

The UW researchers are working on system design and validation so they can imitate what's been done in electronics by stabilizing and characterizing some processes so that the transition from photonics to systems can be smooth.

Silicon photonics has developed over the last decade, and the transition from using devices to systems is something that has only recently occurred.

The digital electronics revolution over the past 40 years has had a transformative effect on how the Air Force systems are built, and hopefully it has similar impact on photonic systems.The researchers' current goal is to work first on test runs for the new optical chips for commercial uses and on developing some software tools that will make the design process easier.

AFOSR program manager, Dr. Gernot S. Pomrenke, agrees with Prof. Hochberg. "Integrating silicon photonics will impact Air Force, DoD and commercial avionics," he said. "AFRL has been a leader in developing and supporting this technology over the last two decades and the OpSIS program will help in transitioning silicon photonics into new system capabilities."

Creating a Green tomorrow with Nano-Paints

 With the many advantages of nano-materials coming to the fore every day, paint manufacturers are replacing conventional paints with those made from nano-particles. They are found to increase scratch resistance, have water repellency properties, provide UV protection, improve durability and have self-cleaning and anti-microbial properties. 

The application of these paints promises to achieve better energy ratings for buildings, better indoor air quality and fewer allergy-related illnesses than the conventional paints, which are usually composed of toxic VOCs (volatile organic compounds). Nanotechnology has helped in development of non-toxic coating systems, which not only stop the appearance of algae and fungal growth but also destroy antibiotic resistant bacteria that are commonly found in hospitals.

The growing awareness of reducing carbon footprints and improve energy costs has led to a widespread use of nano-paints, which are eco-friendly, cost-effective and healthy for the people and environment right now as well as in the future. Thermal insulating paints reduce the amount of heat penetrating into the buildings, thus keeping the inner environments cool and reducing the load on air conditioning systems. This in turn contributes greatly in reducing the world carbon output, thus enabling us to take effective steps towards fighting global-warming.

The US Navy also uses nano-coatings to paint their ships and repair worn out parts. They ensure that the algae do not grow on the metal parts and are instantly washed away by the ocean waters. The coatings are corrosion free; non-toxic and hence do their bit in saving marine life. Graphene based Electro Static paints are also being increasingly used in the Automobile industry.

Paints using nanotechnology are non hazardous to the human health and the environment. They play an important role in reducing pollution by binding with the pollutants and breaking them down. They are easier to clean, smoothly structured and last longer.

Nanotechnology has greatly improved the way the paints make our buildings look more beautiful, make them more eco-friendly and durable while making them energy and cost efficient.

Transistor Created by Single Electron

A University of Pittsburgh-led team has created a single-electron transistor which can act as a building block for powerful computer memories, advanced electronic materials and quantum computers.

The transistor's central component consists of only one or two electrons of 1.5 nanometers in diameter. That flexibility would make the transistor important to a range of computational applications, from memories to quantum processors, powerful devices.

In addition, the tiny central island could be used as an artificial atom for developing new classes of artificial electronic materials, such as exotic superconductors with properties not found in natural materials, explained.

Scientist cited their device as SketchSET, or sketch-based single-electron transistor. Using the sharp conducting probe of an atomic force microscope, electronic devices such as wires and transistors of nanometer dimensions can be created at the interface of a crystal of strontium titanate and a 1.2 nanometer thick layer of lanthanum aluminate. The electronic devices can then be erased and the interface used anew.

The SketchSET -- which is the first single-electron transistor made entirely of oxide-based materials -- consists of an island formation that can house up to two electrons. The number of electrons on the island -- which can be only zero, one, or two -- results in distinct conductive properties. Wires extending from the transistor carry additional electrons across the island.

One of the advantages of a single-electron transistor is its extreme sensitivity to an electric charge. Another property of these oxide materials is ferroelectricity, which allows the transistor to act as a solid-state memory. The ferroelectric state can, in the absence of external power, control the number of electrons on the island, which in turn can be used to represent the 1 or 0 state of a memory element. A computer memory based on this property would be able to retain information even when the processor itself is powered down, researcher commented. The ferroelectric state also is expected to be sensitive to small pressure changes at nanometer scales, making this device potentially useful as a nanoscale charge and force sensor.

Solar Cell fabricated by High Bandgap Inorganic Zinc Oxide Nanowire Arrays

Arrays of core/shell nanowires had previously been theorized as a potential structure that, while composed of chemically more stable large bandgap inorganic materials, should also be capable of absorbing the broad range of the wavelengths present in sunlight. High bandgap semiconductors are generally considered not effective at absorbing most of the available wavelengths in solar radiation by themselves. For instance, high bandgap zinc oxide (ZnO) is transparent in the visible but absorptive in the ultraviolet range, and thus is widely used in sunscreens but was not considered useful in solar cells.

In the report, a team of researchers from Xiamen University in China and the University of North Carolina at Charlotte describe successfully creating zinc oxide (ZnO) nanowires with a zinc selenide (ZnSe) coating to form a material structure known as a type-II heterojunction that has a significantly lower bandgap than either of the original materials. The team reported that arrays of the structured nanowires were subsequently able to absorb light from the visible and near-infrared wavelengths, and show the potential use of wide bandgap materials for a new kind of affordable and durable solar cell.

"High bandgap materials tend to be chemically more stable than the lower bandgap semiconductors that we currently have," noted team member Yong Zhang, a Bissell Distinguished Professor in the Department of Electrical and Computer Engineering and in the Energy Production and Infrastructure Center (EPIC) at the University of North Carolina at Charlotte.

And these nanowire structures can be made using a very low cost technology, using a chemical vapor deposition (CVD) technique to grow the array," he added. "In comparison, solar cells using silicon and gallium arsenide require more expensive production techniques.

Past attempts to use high band gap materials did not actually use the semiconductors to absorb light but instead involved coating them with organic molecules (dyes) that accomplished the photo absorption and simply transmitted electrons to the semiconductor material. In contrast, the team's heterojunction nanowires absorb the light directly and efficiently conduct a current through nano-sized "coaxial" wires, which separate charges by putting the excited electrons in the wires' zinc oxide cores and the "holes" in the zinc selenide shells.

"By making a special heterojunction architecture at the nanoscale, we are also making coaxial nanowires which are good for conductivity," said Zhang. "Even if you have good light absorption and you are creating electron-hole pairs, you need to be able to take them out to the circuit to get current, so we need to have good conductivity. These coaxial nanowires are similar to the coaxial cable in electrical engineering. So basically we have two conducting channels -- the electron going one way in the core and the hole going the other way in the shell."

The nanowires were created by first growing an array of six-sided zinc oxide crystal "wires" from a thin film of the same material using vapor deposition. The technique created a forest of smooth-sided needle-like zinc oxide crystals with uniform diameters (40 to 80 nanometers) along their length (approximately 1.4 micrometers). A somewhat rougher zinc selenide shell was then deposited to coat all the wires. Finally, an indium tin oxide (ITO) film was bonded to the zinc selenide coating, and an indium probe was connected to the zinc oxide film, creating contacts for any current generated by the cell.

"We measured the device and showed the photoresponse threshold to be 1.6 eV," Zhang said, noting that the cell was thus effective at absorbing light wave wavelengths from the ultraviolet to the near infrared, a range that covers most of the solar radiation reaching earth's surface.

Though the use of the nanowires for absorbing light energy is an important innovation, perhaps even more important is the researchers' success in using stable high bandgap inorganic semiconductor materials for an inexpensive but effective solar energy device.

"This is a new mechanism, since these materials were previously not considered directly useful for solar cells," Zhang said. He stressed that the applications for the concept do not end there but open the door to considering a larger number of high bandgap semiconductor materials with very desirable material properties for various solar energy related applications, such as hydrogen generation by photoelectrochemical water splitting.

"The expanded use of type II nanoscale heterostructures also extends their use for other applications as well, such as photodetectors -- IR detector in particular," he noted.

 

Manipulating Molecules for Controlling the Conductance

Nongjian Tao, a researcher at the Biodesign Institute at Arizona State University, has demonstrated a smart way of controlling electrical conductance of a single molecule, by exploiting the molecule's mechanical properties. This type of control could lead to a design of ultra-tiny electrical gadgets. It also renders a platform to perform myriad useful tasks from biological and chemical sensing to improving telecommunications and computer memory. The main challenge with this kind of device is that unconventional effects of the quantum world dominate the device behavior.

 In the current research, Tao examines the electromechanical properties of single molecules sandwiched between conducting electrodes. When a voltage is applied, a resulting flow of current can be measured. A particular type of molecule, known as pentaphenylene, was used and its electrical conductance examined.

Scientist was able to vary the conductance simply by changing the orientation of the molecule with respect to the electrode surfaces. Specifically, the molecule's tilt angle was altered, with conductance rising as the distance separating the electrodes decreased, and reaching a maximum when the molecule was poised between the electrodes at 90 degrees.

The reason for the dramatic fluctuation in conductance is due to the pi orbitals of the electrons making up the molecules, and their interaction with electron orbitals in the attached electrodes. Tao opined that pi orbitals may be thought of as electron clouds, projecting perpendicularly from either side of the plane of the molecule. When the tilt angle of a molecule trapped between two electrodes is altered, these pi orbitals can come in contact and blend with electron orbitals contained in the gold electrode. This process is known as lateral coupling. This lateral coupling of orbitals has the effect of increasing conductance.

In the case of the pentaphenylene molecule, the lateral coupling effect was pronounced, with conductance levels increasing up to 10 times as the lateral coupling of orbitals came into greater play. In contrast, the tetraphenyl molecule used as a control for the experiments did not exhibit lateral coupling and conductance values remained constant, regardless of the tilt angle applied to the molecule. Molecules can now be designed to either exploit or minimize lateral coupling effects of orbitals, thereby permitting the fine-tuning of conductance properties, based on an application's specific requirements.

A further self-check on the conductance results was carried out by scientists using a modulation method. Here, the molecule's position was jiggled in 3 spatial directions and the conductance values observed. Only when these rapid perturbations specifically changed the tilt angle of the molecule relative to the electrode were conductance values altered, indicating that lateral coupling of electron orbitals was indeed responsible for the effect. Tao also suggests that this modulation technique may be broadly applied as a new method for evaluating conductance changes in molecular-scale systems.

Nanosilver

Nanosilver is not a new discovery by nanotechnologists - it has been used in various products for over a hundred years,. The antimicrobial effects of minute silver particles, which were then known as "colloidal silver", were known from the earliest days of its use.

As early as the 19th century, minute silver particles were used, for example in antibacterial water filters.

Numerous nanomaterials are currently at the focus of public attention. In particular silver nanoparticles are being investigated in detail, both by scientists as well as by the regulatory authorities. The assumption behind this interest is that they are dealing with a completely new substance. However, nanosilver is by no means the discovery of the 21st century. Silver particles with diameters of seven to nine nm were mentioned as early as 1889. They were used in medications or as biocides to prevent the growth of bacteria on surfaces, for example in antibacterial water filters or in algaecides for swimming pools.

The nanoparticles were known as colloidal silver in those days, but now - extremely small particles of silver. The only new aspect is the use today of the prefix nano. "However," according to Bernd Nowack, "nano does not mean something new, and nor does it mean something that is harmful." When colloidal silver" became available on the market in large quantities in the 1920s it was the topic of numerous studies and subject to appropriate regulation by the authorities. Even in those days the significance of the discovery of nanoparticles and how they worked was realized. But that does not mean that the possible side-effects of nanoparticles on humans and the environment should be played down or ignored. It is important to characterize in exact detail the material properties of nanosilver and not just to use without verifying.

The term nanoparticle is understood to refer to particles whose dimensions are less than 100 nm. Because of their minute size nanoparticles have different properties than those of larger particles of the same material. For example, for a given volume nanoparticles have a much greater surface area, so they are frequently much more reactive than the bulk material. In addition, even in small quantities nanosilver produces more silver ions than solid silver. These silver ions are toxic to bacteria. Whether or not nanosilver represents a risk to humans and the environment is currently the subject of a great deal of investigation.

Tiny Magnetic Switch Discovered by Controlling Single Molecule at Room Temperature

A Kiel research group headed by the chemist, Professor Rainer Herges, has succeeded for the first time in directly controlling the magnetic state of a single molecule at room temperature. The switchable molecule could be used both in the construction of tiny electromagnetic storage units and in the medical imaging.

The researchers developed a molecular machine constructed in a similar way to a record player. The molecule consists of a nickel ion surrounded by a pigment ring and a nitrogen atom which hovers above the ring like the tone arm on a record player. When this molecule is irradiated with blue-green light, the nitrogen atom is placed exactly vertically to the nickel ion like a needle. This causes the nickel ion to become magnetic, because the pairing of two electrons is cancelled out. The counter effect is blue-violet light. The nitrogen atom is raised, the electrons form a pair and the nickel ion is no longer magnetic. One can repeat this switching of the magnetic state over 10,000 times by varied irradiation with the two different wavelengths of light, without wearing out the molecular machine or encountering side reactions.

The switch which has been discovered, with its diameter of only 1.2 nanometres, could be used as a tiny magnetic reservoir in molecular electronics. Most of all, hard disk manufacturers may be interested in this, as a higher storage capacity can be achieved by reducing the size of the magnetic particles on the surface of the disks. Professor Herges also believes the use of the magnetic switch in the medical field is feasible. The record player molecule can be used intravenously as a contrast agent in MRT (magnetic resonance tomography) in order to search for tumors or constricted blood vessels. Initial tests in the University Medical Center Schleswig-Holstein's neuroradiology department were successful.

As the signal-to-noise ratio is improved by the switching process, a smaller amount of the contrast agent is required than for the magnetic salts currently being used. In addition, the molecular machine could also serve as a basis for developing new contrast agents to depict such features as temperature, pH value or even certain biochemical markers in the body in a three-dimensional form. Using contrast agents such as these, it could be possible to localize centers of inflammation, detect tumors and visualize many metabolic processes.

Some Cool Ideas of Nanotechnology

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Touchscreens: Made of Carbon Nanotubes

Touchscreens are not a new thing in this rapidly paced technological world. But what it lacks is its viability as far as the price is concerned. In the upcoming Nano Tech Fair 2011 which is scheduled to take place February 16-18, researchers at Fraunhofer are presenting touchscreens that contain carbon nanotubes.

The versatile nature of touchscreen make it a celebrity in the modern technology. Just touching it slightly with the tips of the fingers is enough. One can effortlessly write, navigate, open menu windows or rotate images on touchscreens. Within fractions of a second one touch is translated into control commands that a computer understands. At first glance, this technology borders on the miraculous, but in real life this mystery just is a wafer-thin electrode under the glass surface of the display made of indium-tin-oxide (ITO). This material is nothing short of ideal for use in touchscreens because it is excellent at conducting slight currents and lets the colours of the display pass through unhampered. But, the problem is: indium is not abundant in nature.

Therefore, private industry is very interested in alternatives to ITO that are similarly efficient. The researchers at Fraunhofer have succeeded at coming up with a new material for electrodes that is on the same level as ITO and on top of it is much cheaper. Its main components are carbon nanotubes and low-cost polymers. This new electrode foil is composed of two layers. One is the carrier, a thin foil made of inexpensive polyethylenterephthalate (PET) used for making plastic bottles. Then a mixture of carbon-nanotubes and electrically conducting polymers is added that is applied to the PET as a solution and forms a thin film when it dries.

In comparison to ITO, these combinations of plastics have not been particularly durable because humidity, pressure or UV light put a strain on the polymers. The layers became brittle and broke down. Only carbon nanotubes have made them stable. The carbon nanotubes harden on the PET to create a network where the electrically conducting polymers can be firmly anchored. That means that this layer is durable in the long run. Ivica Kolaric, project manager from Fraunhofer Institute for Manufacturing Engineering and Automation, admits that the electrical resistance of our layer is somewhat greater than that of the ITO, but it's easily enough for an application in electrical systems. Its merits are more than convincing: carbon is not only low-cost and available all over the world. It is also a renewable resource that can be yielded from organic matter such as wood.

There are a whole series of implementations for the new technology. This foil is flexible and can be used in a variety of ways. Even with this photovoltaic foils can be made to corrugated roofs or other uneven structures. The researcher has already set up pilot production where the foil can be enhanced for a wide range of applications.

A New Transistor made of Molybdenite: Thinner than Silicon and better than Graphene

In a recent advancement, scientist claimed that molybdenite could be extremely useful in fabricating smaller and more energy efficient electronic chips because of its distinct advantages over traditional silicon or graphene for use in electronics applications.

A discovery made at EPFL's Laboratory of Nanoscale Electronics and Structures (LANES) could play an important role in electronics. It was divulged that researchers can now make transistors that are smaller and more energy efficient. Research carried out in the Laboratory has revealed that molybdenite, or MoS₂, is a very effective semiconductor. This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. But it had not yet been extensively studied for use in electronics.

Molybdenite is a two-dimensional material, very thin and easy to use in nanotechnology. It has real potential in the fabrication of very small transistors, light-emitting diodes (LEDs) and solar cells.  

When comparing its advantages with silicon, currently the primary component used in electronic and computer chips, , it was seen that it is  less voluminous that silicon, which is a three-dimensional material.

One of molybdenite's advantages is that it is in a 0.65-nanometer-thick sheet of MoS₂, the electrons can move around as easily as in a 2-nanometer-thick sheet of silicon, explains Kis, one of the scientists in LANES. He also commented that it's not currently possible to fabricate a sheet of silicon as thin as a monolayer sheet of MoS₂. Another advantage of molybdenite is that it can be used to make transistors that consume 100,000 times less energy in standby state than traditional silicon transistors. A semi-conductor with a band-gap must be used to turn a transistor on and off, and molybdenite's 1.8 electron-volt gap is ideal for this purpose.

And again if we take the graphene, whose discovery in 2004 earned University of Manchester physicists André Geim and Konstantin Novoselov the 2010 Nobel Prize in Physics, it showed that existence of the band gap in molybdenite also gives it an advantage over graphene. That is why molybdenite considered today by many scientists as the electronics material of the future, as graphene doesn't have a gap, and it is very difficult to artificially reproduce one in the material

Nanocomposites to monitor wind turbine blade structure

Gary D. Seidel, assistant professor of aerospace engineering in the College of Engineering atVirginia Tech developed a carbon nanotube-enhanced composite for structural health monitoring sensors to improve the resiliency of huge wind turbine blades.

Wind turbine blades enjoy a steady wind but can be damaged by gust-induced vibrations. Seidel proposes to create tiny sensor patches that can be selectively placed in key locations where it is anticipated that damage will start. The patches are made of the same base material as the blade but sprinkled with carbon nanotubes, resulting in a nanocomposite sensor which adds negligible weight to the structure.

The submicroscopic carbon nanotubes can be highly conductive, like invisible, extremely lightweight, electrical wires. Placing the highly conducting carbon nanotubes inside a polymer material makes the resulting nanocomposite patch's conductivity sensitive to deformation. As the material is deformed by a stress on the blade, the nanotubes shift, move closer together, and their conductivity jumps – one mechanism behind the phenomenon known as a piezoresistive response. The change in the nanocomposite conductivity sends a signal to the wind turbine control center, allowing the operator to then know which blade is stressed and should be turned off to prevent further damage to that turbine.

Seidel's focus is on assessing the sensing capabilities of the nanocomposite and building multiscale models for use in structural health monitoring software algorithms. His preliminary models have demonstrated that he can create nanocomposites that respond to stresses with conductivity changes.

Based on the mechanism behind the piezoresistive response of our nanocomposites, necessary tools will be created for nanocomposite sensor development and tailoring for the wind turbine blade application.