Electrostatic Force Microscopy (EFM): Imaging electric charge using microbial nanowires: Breakthrough in protein based nanoelectronics

Recent study carried out by UMass Amherst researchers has showed that electric charges propagate along microbial nanowires of the microbe Geobacter just as they do in carbon nanotubes.

Physicists affirmed that injection of electrons at one end in the microbial nanowires lit up the whole filament as the electrons propagated through the nanowire, similar to the other highly conductive materials. The technique applied here is known as electrostatic force microscopy (EFM). This technique has immense environment implications as conversion of waste to biogas is possible by conducting electricity through these wires. The nanowires permit Geobacter to live on iron and other metals in the soil, significantly changing soil chemistry and playing an important role in environmental cleanup. Microbial nanowires are also key components in the ability of Geobacter to produce electricity, a novel capability that is being adapted to engineer microbial sensors and biological computing devices.

In biological materials, electrons typically move by hopping along discrete biochemical stepping-stones that can hold the individual electrons. By contrast, electrons in microbial nanowires are delocalized, not associated with just one molecule, leading to metallic-like conductivity phenomena.

This investigation not only brings up an important new principle in biology but also in materials science. Natural amino acids, when arranged correctly, can propagate charges similar to molecular conductors. It opens exciting opportunities for protein-based nanoelectronics due to the fact that manipulating microbes for electrical application seems feasible. Efforts are also directed towards building electronic sensors to detect environmental contaminants and microbiological computers using Geobacter.

Mechanosensation device by molybdenum disulfide (MoS2)

In a breakthrough invention, scientists have successfully executed an experiment of piezoelectricity and the piezotronic effect in an atomically thin material, molybdenum disulfide (MoS₂), resulting in a unique electric generator and mechanosensation devices; although the piezoelectric effect in this material had already been predicted theoretically.

Piezoelectricity is defined as a phenomenon in which pressure generates an electrical voltage in a material or vice-versa. But no experimental observation of piezoelectricity has been made yet for few atom thickness material. The observation of molybdenum disulfide material has unfolded the potential for new types of mechanically controlled electronic devices.

In an interesting application of this phenomenon, this material could be made as a wearable device, integrated into clothing, to convert energy from your body movement to electricity and power wearable sensors or medical devices, or perhaps supply enough energy to charge cell phone.

There are two keys to using molybdenum disulfide for generating current: using an odd number of layers and flexing it in the proper direction. The material is highly polar, but an even number of layers cancels out the piezoelectric effect. The material's crystalline structure also is piezoelectric in only certain crystalline orientations.

Group of researchers placed thin flakes of MoS₂ on flexible plastic substrates and determined how their crystal lattices were oriented using optical techniques. They then patterned metal electrodes onto the flakes and measure current flow as the samples were mechanically deformed. They monitored the conversion of mechanical to electrical energy, and observed voltage and current outputs.

The researchers also noted that the output voltage reversed sign when they changed the direction of applied strain, and that it disappeared in samples with an even number of atomic layers, confirming theoretical predictions published last year. The presence of piezotronic effect in odd layered MoS₂ was also observed for the first time.

To be piezoelectric, a material must break central symmetry. A single atomic layer of MoS₂ has such a structure, and should be piezoelectric. However, in bulk MoS₂, successive layers are oriented in opposite directions, and generate positive and negative voltages that cancel each other out and give zero net piezoelectric effect.

In fact, MoS₂ is just one of a group of 2D semiconducting materials known as transition metal dichalcogenides, all of which are predicted to have similar piezoelectric properties. These are part of an even larger family of 2D materials whose piezoelectric materials remain unexplored. The research could lead to complete atomic-thick nanosystems that are self-powered by harvesting mechanical energy from the environment. This study also reveals the piezotronic effect in two-dimensional materials for the first time, which greatly expands the application of layered materials for human-machine interfacing, robotics, MEMS, and active flexible electronics.

Fullerene spheres: as nano-bearing

About 3500 years ago, man invented the wheel to make life easier. Then, thanks to Leonardo Da Vinci's, the wheel was made smaller to obtain ball bearings. Today we are trying to get even smaller: scientists are thinking about nano-bearings. In the future we'll have many nano-machines capable of carrying out the most diverse tasks, for example transporting medicines inside the human body. In order to save energy, many of these vehicles will have to able to move efficiently, using as little energy as possible, and nano-sized ball bearings may help achieve this goal.

Nanomechanical devices will need tiny devices to reduce friction and make movement possible. Fullerene or buckyballs (C60 molecule) seemed to be an excellent candidate for nano-bearings. Scientists thought they could use C60, a hollow carbon nano-sphere as a nano-bearing. Preliminary studies suggested that C60 molecules suddenly become free to rotate at a particular temperature, which hopefully has a role in friction. However, experimental results yielded conflicting results and yet to be verified in which temperature the friction becomes less. 

Simulation has been carried out using tiny tip of an electron microscope bearing a C60 flake, which was dragged over a surface also made of C60. It has been found that when the flake was attached in such a way that it couldn't rotate and the friction did not decrease, even if the temperature is raised. It's as if the bearings making up the flake interlocked with the substrate, with no nano-bearing effect. However, when the flake was free to rotate there was a dramatic drop in friction and the flake could slide over the surface far more smoothly.

Modulated Nanostructure: Nanowire bridging transistors: The new Buzz word for next-generation electronics

Silicon has been established as one of the widely used material in the integrated circuit since approximately 60 years. It is used to fabricate transistors using conventional method, where etching of the layers was done to formulate some structures. However, circuit based on silicon reach its operational speed limit and does not work above certain temperature. In addition to that, ever increasing demand of miniaturization has led to the development of advanced manufacturing technique where nanostructure material plays significant roles along with the addition of other semiconducting material such as gallium nitride. It does not only show promise for a new generation of fast, robust electronic and photonic devices, but also opens up the scope of innovation for the researchers. Such is the case of three dimensional nanowire transistors, developed by scientists of University of California.

 

 One of the technical problem silicon substrate is facing over the years is the lattice parameter mismatch with other materials. Match is necessary due to the growth technique associated with integrated circuit, which in turn faces major limitation as far as the growth material is concerned. To overcome these challenges, nanowire made of semiconductor materials was made on top of silicon surfaces. Due to the lower surface area of nanowire which acquires the place of silicon, problem of lattice mismatch does not arise. The new technology could be used, for example, to build sensors that can operate under high temperatures, for example inside aircraft engines. In the near future, machine will be dependent on a variety of sensors and control systems that operate in extreme environments, such as motor vehicles, boats, airplanes, terrestrial oil and ore extraction, rockets, spacecraft, and bodily implants.

 

The researchers have been able to make these nanowires operate as transistors, and combine them into more complex circuits as well as devices that are responsive to light. They have developed techniques to control the number of nanowires, their physical characteristics and consistency. The technology also leverages the well-established technology for manufacturing silicon integrated circuits.

New nanomaterial for longer battery life

An architecture nanostructured material has been recently developed by researchers at the University of California using nanocrystalline ruthenium oxide coupled with graphene. This technology could improve the quality of the supercapacitors leading to long lasting battery life in portable electronics.

 

The present study showed that two times more energy and power can be achieved with this material compared to commercial supercapacitors. The electrode and/or supercapacitors made with above mentioned nanomaterial can be cycled over 8000 times without any fatigue because of its high energy density. Nanostructured materials also rendered large surface area, high electrical conductivity, short ion diffusion pathways and excellent interfacial integrity, making these high energy supercapacitor electrodes ideal for future energy storage applications.

Self assembled nanostructure through field assisted phase transition

In the year of 2012, scientist developed the idea of using nanoparticles as building block of functional material which can be engineered to make a computer chip that can assemble itself.

The research carried out by researchers of NASA and University of Delware reported an article about the self assembled with specific structures, built by nanomaterials.

They have observed transition of paramagnetic colloids from random structures to organised crystalline structures when an external magnetic field with desired frequency and field strength was applied into it. This kind of phase separation/transition provides the opportunity to build crystals using magnetic field. It is also useful in understanding the phenomena/mechanisms through which the materials are turned into crystalline.

This new phenomenon could prove worthy for manufacturing new nanoscale self assembled components due to a definite relationship between applied electric field and the conversion of disorder to order structure.

For further reading regarding field assisted phase transition:

http://www.pnas.org/content/109/40/16023.full.pdf+html?sid=d4c55815-5d87-4419-b4da-dd7cc0eaeb9c

Discovery of EIGHTH colour in the rainbow using Carbon nano tube

Scientists have recently “observed” an invisible eighth colour in the rainbow, a discovery that could have wide-ranging implications in the field of military camouflage and modern surveillance.

The invention of the new basic colour in the spectrum of light was made by physicists at the Randall Monroe University in West Virginia, who were investigating packets of photons that are fired through a cloud of ultracold sodium atoms, colliding with the light and slowing it down. This light was then passed through a series of carbon nanotubes in which the incident angle was enough to bounce the photons back on themselves.

The eighth colour can be thought of as the first addition to the traditional spectrum since Isaac Newton first successfully split white light using a triangular prism in 1671.

There is a possibility that this new colour could be the pioneer in the invention of a invisible cover. While current designs rely on physically bending light around an object or shielding it from a small portion of the spectrum, scientists suggest that simply bathing the target in this previously unseen colour could have dramatic results. 
 

The relative simplicity of the new technology could also have impact on the consumer market, as researchers claim, accessing the colour would not be expensive.

Thermocrystal: an excellent idea to control the direction of heat by nanoparticle alloy

An MIT scientist has developed a technique that provides a new way of manipulating heat, allowing it to be controlled much as light waves can be manipulated by lenses and mirrors.

The approach relies on engineered materials consisting of nanostructured semiconductor alloy crystals. Heat is a vibration of matter, a vibration of the atomic lattice of a material like sound. Such vibrations can also be thought of as a stream of phonons, which is equivalent to the photons that carry light. The new approach is similar to recently developed photonic crystals that can control the passage of light.

The spacing of tiny gaps in these materials is tuned to match the wavelength of the heat phonons. It’s a completely new way to manipulate heat. Heat differs from sound in the frequency of its vibrations: Sound waves consist of lower frequencies (up to the kilohertz range, or thousands of vibrations per second), while heat arises from higher frequencies (in the terahertz range, or trillions of vibrations per second).

In order to apply the techniques already developed to manipulate sound, first step was to reduce the frequency of the heat phonons, bringing it closer to the sound range. Phonons for sound can travel for kilometres, but phonons of heat only travel for nanometers. That’s why we couldn’t hear heat even with ears.
Heat also spans a wide range of frequencies, while sound spans a single frequency. To get rid of the problem, the first thing to do is to reduce the number of frequencies of hea, bringing these frequencies down into the boundary zone between heat and sound. Making alloys of silicon that incorporate nanoparticles of germanium in a particular size range accomplished this lowering of frequency, scientist found.

Reducing the range of frequencies was also accomplished by making a series of thin films of the material, so that scattering of phonons would take place at the boundaries. This ends up concentrating most of the heat phonons within a relatively narrow window of frequencies.

Following the application of these techniques, more than 40 percent of the total heat flow is concentrated within a hypersonic range and most of the phonons align in a narrow beam, instead of moving in every direction.
As a result, this beam of narrow-frequency phonons can be manipulated using phononic crystals similar to those developed to control sound phonons. Because these crystals are now being used to control heat instead, these are referred to as thermocrystals, a new category of materials.

These thermocrystals might have a wide range of applications, including in improved thermoelectric devices, which convert differences of temperature into electricity. Such devices transmit electricity freely while strictly controlling the flow of heat.

Most conventional materials allow heat to travel in all directions, like ripples expanding outward from a pebble dropped in a pond; thermocrystals could instead produce the equivalent of those ripples only moving out in a single direction. The crystals could also be used to create thermal diodes; materials in which heat can pass in one direction, but not in the reverse direction. Such a one-way heat flow could be useful in energy-efficient buildings in hot and cold climates.

Other variations of the material could be used to focus heat to concentrate it in a small area. Another intriguing possibility is thermal cloaking, materials that prevent detection of heatto shield objects from detection by visible light or microwaves.

For further reading: http://prl.aps.org/pdf/PRL/v110/i2/e025902

Electrodes made by Carbon Nanotubes for Recording Neuron Activity

Scientists have been studying how neuron communication in the brain relies on glass and metal electrodes to detect the tiny, high speed synaptic potentials. Yet, nanotechnology offers the possibility of scaling down the electrodes so that individual neurons could be tapped in living, moving animals. Researchers at Duke University are now claiming that they developed electrodes made out of self-entangled carbon nanotubes that are a millimeter long and feature a sub-micron tip. Carbon nanotubes have excellent electrical properties and are incredibly strong for their size. The new needles are small enough to penetrate individual cells and record intracellular electrical activity. The Duke team used the new electrodes to make such recordings in live animals and on brain slices and envision using the new electrodes to record neuronal activity for extended periods in freely moving animals.

The computational complexity of the brain depends in part on a neuron’s capacity to integrate electrochemical information from vast numbers of synaptic inputs. The measurements of synaptic activity that are crucial for mechanistic understanding of brain function are also challenging, because they require intracellular recording methods to detect and resolve millivolt scale synaptic potentials. Although glass electrodes are widely used for intracellular recordings, novel electrodes with superior mechanical and electrical properties are desirable, because they could extend intracellular recording methods to challenging environments, including long term recordings in freely behaving animals. Carbon nanotubes (CNTs) can theoretically deliver this advance, but the difficulty of assembling CNTs has limited their application to a coating layer or assembly on a planar substrate, resulting in electrodes that are more suitable for in vivo extracellular recording or extracellular recording from isolated cells. Here a novel, yet remarkably simple, millimeter-long electrode with a sub-micron tip, fabricated from self-entangled pure CNTs can be used to obtain intracellular and extracellular recordings from vertebrate neurons in vitro and in vivo. This fabrication technology provides a new method for assembling intracellular electrodes from CNTs, affording a promising opportunity to harness nanotechnology for neuroscience applications.

Carbon Atom for Ultra-Small Energy-Efficient Electronic Devices

A team of scientists from Tyndall National Institute at University College Cork and the National University of Singapore have designed and fabricated ultra-small devices for energy-efficient electronics. By finding out how molecules behave in these devices, a ten-fold increase in switching efficiency was obtained by changing just one carbon atom. These devices could provide new ways to combat overheating in mobile phones and laptops, and could also aid in electrical stimulation of tissue repair for wound healing.

 Scientists opined that these molecules are very useful because they allow current to flow through them when switched ON and block current flow when switched OFF. The results of the study show that simply adding one extra carbon is sufficient to improve the device performance by more than a factor of ten. Atom-level computer simulations showed how molecules with an odd number of carbon atoms stand straighter than molecules with an even number of carbon atoms. This allows them to pack together more closely. Tightly-packed assemblies of these molecules were formed on metal electrode surfaces and were found to be remarkably free of defects. These high quality devices can suppress leakage currents and so operate efficiently and reliably. The device can be cleanly switched on and off purely on the basis of the charge and shape of the molecules, just like in the biological nanomachines that regulate photosynthesis, cell division and tissue growth.

Modern electronic devices such as telephones and tablets in manufacture today rely on tiny switches approaching molecular sizes. This provides new challenges for electronics but opens up exciting opportunities for blending molecular properties to be used to advantage. This study is an exciting new avenue to exploit molecular design to achieve new ways to perform information processing. A key enabling feature for nanoscale electronics will be the ability to use molecules as rectifiers and switches. By demonstrating the rational design of molecules that rectify current with a large and highly-reproducible ON/OFF ratio, the study provides a key advance towards the creation of technologically viable ultra-small device components. Fifty thousand of the rectifier molecules strung end to end would fit across the diameter of a human hair. Advances in computing, synthesis and characterisation means scientists can now understand and control material at the scale of atoms and molecules.

The combined experiments and simulations show for the first time that minute improvements in molecule orientation and packing trigger changes in Van-der Waals forces that are sufficiently large to dramatically improve the performance of electronic devices. These van der Waals forces are the weakest of all intermolecular forces and only become significant when summed over large areas. Hence, up until now, the majority of research into ultra-small devices has used stronger pi-pi interactions to stick molecules together, and has ignored the much weaker Van-der Waals interactions. The present study shows, how Van-der Waals effects, which are present in every conceivable molecular scale device, can be tuned to optimise the performance of the device.
The devices are based on molecules that act as diodes by allowing current to pass through them when operated at forward bias and blocking current when the bias is reversed. Molecular rectifiers were first proposed back in 1974, and advances in scientific computing have allowed molecular‐level design to be used over the past decade to develop new organic materials that provide better electrical responses. However, the relative importance of the interactions between the molecules, the nature of the molecule-metal contact and the influence of environmental effects have been questioned. This new research demonstrates that dramatic improvements in device performance may be achieved by controlling the van der Waals forces that pack the molecules together. Simply changing the number of carbon atoms by one provides significantly more stable and more reproducible devices that exhibit an order of magnitude improvement in ON/OFF ratio. The research findings demonstrate the feasibility of boosting device performances by creating tighter seals between molecules.

Excellent Strategy for Fingerprint Identification using Gold nanoparticles

Identifying fingerprints on paper is a commonly used method in police forensic work, but unfortunately it is not easy to make those fingerprints visible. Now, scientists at the Hebrew University of Jerusalem have developed a new approach for making such fingerprints more readily readable.

The new method, created by a team headed by Prof. Yossi Almog and Prof. Daniel Mandler of the Institute of Chemistry at the Hebrew University, uses an innovative chemical process to produce a negative of the fingerprint image rather than the positive image produced under current methods. Unlike the latter, the Hebrew University-developed process is nearly independent of the composition of the sweat residue left behind on the paper.

In many criminal investigations, paper evidence plays an important role, and it is useful to know who has handled such documents as checks, paper currency, notes, etc. Studies have shown that less than half of the fingerprints on paper items can be made sufficiently visible to enable their identification. The main reason for this seems to be the highly variable composition of the sweat left behind on the paper.

The new procedure developed at the Hebrew University avoids these problems. It involves an inversion of an established method in which gold nanoparticles are first deposited onto the invisible fingerprints, followed by elemental silver, similar to the development of a black and white photograph.

 In the conventional technique, the gold particles get stuck to the amino acid components of the sweat in the fingerprints, and then silver is deposited onto the gold. The result is quite often low-contrast impressions of the fingerprints. In the new method, the gold nanoparticles stick directly to the paper surface, but not the sweat. This technique utilizes the sebum from the fingerprints as a medium to avoid this interference. (Sebum is an oily substance secreted by the sebaceous glands that helps prevent hair and skin from drying out.) Treatment with a developer containing silver then turns the areas with gold on them black, resulting in a clear, negative image of the fingerprint.

Since the method relies only on the fatty components in the fingerprints, the sweaty aspects play no role in the imaging process This technique also promises to alleviate another problem; for example if paper has become wet, it has previously been difficult to detect fingerprints because the amino acids in the sweat, which are the primary substrate for current chemical enhancement reactions, are dissolved and washed away by water, whereas the fatty components are barely affected. Thus, the avoidance of the sweat aspect provides a further enhancement for police laboratory.

Emerging idea of cooling of nanoscale Computer chips by Crystals

Researchers at the Carnegie Institution have discovered a new efficient way to pump heat using crystals. The crystals can pump or extract heat, even on the nanoscale, so they could be used on computer chips to prevent overheating or even meltdown, which is currently a major limit to higher computer speeds.

Researchers at the University of Chicago performed the preliminary simulations on ferroelectric crystals materials that have electrical polarization in the absence of an electric field. The electrical polarization can be reversed by applying an external electrical field. The scientists found that the introduction of an electric field causes a giant temperature change in the material, dubbed the electrocaloric effect (a phenomenon in which a material shows a reversible temperature change under an applied electric field), far above a temperature to a so-called paraelectric state.

The electrocaloric effect pumps heat through changing temperature by way of an applied electric field. The effect has been known since the 1930s, but has not been exploited because people were using materials with high transition temperatures. So low transition temperature materials are preferred, as in that way, the effect is larger if the ambient temperature is well above the transition temperature,

Ferroelectrics become paraelectric, that is, have no polarization under zero electric field above their transition temperature, which is the temperature at which a material changes its state from ferroelectric to paraelectric.

 
Scientists used atomic-scale molecular dynamics simulations, where they followed the behavior of atoms in the ferroelectric lithium niobate as functions of temperature and an electrical field.

Phosphor removal from nano iron

A professor at Michigan State University is part of a team developing a new method of removing phosphorus from wastewater; a problem seriously affecting lakes and streams across the world.

Phosphorus is part of all food as well as is in items such as detergents and fertilizer and remains a critical problem as it is always present in human and animal wastes.

Discharge from human and industrial wastewater and runoff into lakes and streams can cause eutrophication, making the water unsuitable for recreational purposes and reducing fish populations, as well as causing the growth of toxic algae.

Researchers have figured out and tested over the past 10 years is how to produce a media, enhanced with nanoparticles composed of iron, that can more efficiently remove larger amounts of phosphorus from water.

Phosphorus that is dissolved in wastewater, like sugar in water, is hard to remove. A nano-media made with waste iron can efficiently absorb it, making it a solid that can be easily and efficiently removed and recovered for beneficial reuse. Their method of phosphorus retrieval is much more cost effective than processing phosphate rock. Research suggests that it is significantly cheaper to recover phosphorus this way.

Molybdenum disulfide (MoS2): New nanomaterial with several advantages

The discovery of graphene, a material just one atom thick and possessing exceptional strength and other novel properties, started an avalanche of research around its use for everything from electronics to optics to structural materials. But new research suggests that was just the beginning: A whole family of two-dimensional materials may open up even broader possibilities for applications that could change many aspects of modern life.

The latest new material, molybdenum disulfide (MoS₂) was first described just a year ago by researchers in Switzerland. But in that year, researchers at MIT who struggled for several years to build electronic circuits out of graphene with very limited results (have already succeeded in making a variety of electronic components from MoS₂. They say the material could help usher in radically new products, from whole walls that glow to clothing with embedded electronics to glasses with built-in display screens.

 Researchers think graphene and MoS₂ are just the beginning of a new realm of research on two-dimensional materials. Like graphene, itself a 2-D form of graphite, molybdenum disulfide has been used for many years as an industrial lubricant. But it had never been seen as a 2-D platform for electronic devices until last year, when scientists at the Swiss university produced a transistor on the material.

 Then MIT researchers found a good way to make large sheets of the material using a chemical vapor deposition process. As there are lots of hindrance in making electronic products out of graphene due to lack of bandgap, MoS₂ just naturally comes with large band gap.

 MoS₂ is widely produced as a lubricant and as others are working on making it into large sheets, scaling up production of the material for practical uses should be much easier than with other new materials. People are able to fabricate a variety of basic electronic devices on the material: an inverter, which switches an input voltage to its opposite; a NAND gate, a basic logic element that can be combined to carry out almost any kind of logic operation; a memory device, one of the key components of all computational devices; and a more complex circuit called a ring oscillator, made up of 12 interconnected transistors, which can produce a precisely tuned wave output.

One potential application of the new material is large-screen displays such as television sets and computer monitors, where a separate transistor controls each pixel of the display. Because the material is just one molecule thick, unlike the highly purified silicon that is used for conventional transistors and must be millions of atoms thick, even a very large display would use only an infinitesimal quantity of the raw materials. This could potentially reduce cost and weight and improve energy efficiency.

Further reading:

arxiv.org/pdf/1208.1078 

 

In the future, it could also enable entirely new kinds of devices. The material could be used, in combination with other 2-D materials, to make light-emitting devices. Instead of producing a point source of light from one bulb, an entire wall could be made to glow, producing softer, less glaring light. Similarly, the antenna and other circuitry of a cellphone might be woven into fabric, providing a much more sensitive antenna that needs less power and could be incorporated into clothing.

 The material is so thin that it's completely transparent, and it can be deposited on virtually any other material. For example, MoS₂ could be applied to glass, producing displays built into a pair of eyeglasses or the window of a house or office.