Nanotechnology

Chemical thermometers – a breakthrough that cater the need in microelectronics industry

2020-07-21T23:29:00.001+05:30

With the massive miniaturisation of electronic components, density of the electronic components has been enhanced significantly along with the flowing of heat which results in overheating of the components. But conventional methods are unable to estimate the temperature in the electronic components due to limitation imposed by size of it.

Researchers have recently devised a solution of the above issue by fabricating a molecular film and using it in an electronic component of a nanometric scale. The film is made by spin crossover molecules, a temperature sensitive molecule, which is extremely stable even after several uses. Due to the bi-stability property of these molecules, these molecules exist into two electronic states with difference physical property and interchange the states by absorbing and loosing energy.

Once deposited in the form of a film on an electronic component, the optical properties of SCO molecules change depending on the temperature, enabling this chemical thermometer to establish a nanometric-scale thermal map of the surface of microelectronic circuits. The devise will soon be sued at industrial scale with improved design.

New material for lithium-ion storage - Graphdiyne

2020-07-20T02:44:00.001+05:30

Researchers has devised new two-dimensional carbon based materials – called Graphydiyne.

Carbon is the anode material in lithium-ion batteries. Its layered structure allows lithium ions to travel in and out of the spaces between layers during battery cycling. Carbon has a highly conductive two-dimensional hexagonal crystal lattice, and they form a stable, porous network for efficient electrolyte penetration. However, the fine-tuning of the structural and electrochemical properties is difficult as these carbon materials are mostly prepared from polymeric carbon matter in a top-down synthesis.

Graphdiyne being a hybrid two-dimensional network made of hexagonal carbon rings bridged by two acetylene units, has been used as a nanoweb membrane for the separation of isotopes. However, its distinct electronic properties and web-like structure also make graphdiyne suitable for electrochemical applications. Changshui Huang from the Chinese Academy of Sciences, Beijing, and colleagues have investigated the lithium-storage capabilities and electrochemical properties of tailor-made, electronically adjusted graphdiyne derivatives.

The scientists synthesized the graphdiyne derivatives in a bottom-up approach by adding precursors on a copper foil, which self-organized to form ordered layered nanostructures with distinct electrochemical and morphological properties.

Among these functional groups, those exerting electron-withdrawing effects reduced the band gap of graphdiyne and increased its conductivity, the authors reported. The cyano group was especially effective and, when used as an anodic material, the cyano-modified graphdiyne demonstrated excellent lithium-storage capacity and was stable for thousands of cycles, as the authors reported.

The authors conclude that modified graphdiyne can be prepared by a bottom-up strategy, which is also best suited to build functional two-dimensional carbon material architectures for batteries, capacitors, and other electrocatalytic devices.

Storage solution using silicon in battery with the aid of nanotechnology

2020-05-10T20:30:00.000+05:30

Silicon along with carbon nanotubes has been used to develop a nanostructure to make an effective design for battery anodes. CNT is used to strengthen the material and modify the way the silicon interacts with lithium, which has been extensively used in electrical cars and other devices.

Scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory have used a novel way to use silicon. Silicon, used in computer chips is attractive as it can hold 10 times the electrical charge per gram compared to graphite. The trouble is, silicon expands greatly when it encounters lithium, and it is too weak to withstand the pressure of electrode manufacturing.

To tackle these issues, a unique nanostructure that prevents silicon's expansion when it is mixed with carbon. Scientist work, which was recently published in the journal Nature Communications, could inform new electrode material designs for other types of batteries and eventually help increase the energy capacity of the lithium-ion batteries in electric cars, electronic devices, and other equipment.

How they do it!!

A conductive and stable form of carbon, graphite is well suited to packing lithium ions into a battery's anode as it charges. Silicon can take on more lithium than graphite, but it tends to expand about 300 percent in volume, causing the anode to break apart. The researchers created a porous form of silicon by aggregating small silicon particles into microspheres about 8 micrometers in diameter.

The electrode with porous silicon structure exhibits a change in thickness of less than 20 percent while accommodating twice the charge of a typical graphite anode. However, unlike previous versions of porous silicon, the microspheres also exhibited extraordinary mechanical strength, thanks to carbon nanotubes that make the spheres resemble balls of yarn.

The researchers created the structure sequentially, starting by coating the carbon nanotubes with silicon oxide. Next, the nanotubes were put into an emulsion of oil and water. Then they were heated to boiling. The coated carbon nanotubes condense into spheres when the water evaporates. Then aluminum and higher heat is used to convert the silicon oxide into silicon, followed by immersion in water and acid to remove by-products. What emerges from the process is a powder composed of the tiny silicon particles on the surface of carbon nanotubes.

Device fabricated to produce high power high frequency waves

2020-03-29T14:45:00.000+05:30

Recently Researchers have succeeded to develop a nanodevice that can run 10 times faster than present transistors. The device enables the generation of high-power terahertz waves which are difficult to produce otherwise. Terahertz (THz) waves fall between microwave and infrared radiation in the electromagnetic spectrum, oscillating at frequencies of between 100 billion and 30 trillion cycles per second. Generation of these waves have immense impact on security and medical imaging, sensing, cancer therapy and high-speed wireless communications due to the ability to carry vast quantities of data. These waves can penetrate paper, clothing, wood and walls. It can detect air pollution.

However, THz waves are not widely used because they are costly and cumbersome to generate. But researchers led by Prof. Elison Matioli, built a nanodevice that can generate extremely high-power THz waves.

The compact, cheaper fully electric nanodevice generates high-intensity waves by producing a voltage from 10 V (or lower) to 100 V in the range of a picosecond. The device consists of two metal plates placed very close together, down to 20 nanometres apart. When potential difference between these two plates is applied, electrons surge towards one of the plates (plasma). Once the voltage reaches a certain threshold, the electrons are emitted almost instantly to the second plate. This rapid movement enabled by such fast switches creates a high-intensity pulse that produces high-frequency waves. When hooked up to antennas, the system can produce and radiate high-power THz waves.

The new nanodevice can create both high-energy and high-frequency pulses, unlike present high frequency semiconductor devices, which can only sustain with a few volts before breaking out. The new device has been proposed to surmount these constraint by nanoplasma and state-of-the-art nanoscale fabrication techniques

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

2014-11-02T00:30:00.000+05:30

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)

2014-10-26T17:26:00.000+05:30

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

2014-10-09T12:35:00.000+05:30

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

2014-06-01T02:29:00.000+05:30

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

2014-05-28T22:35:00.001+05:30

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

2014-05-23T20:49:00.000+05:30

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

2014-04-06T15:04:00.000+05:30

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.

Manipulation of Cells and molecules by biomolecular mechanical tweezers

2014-03-30T00:32:00.000+05:30

A new type of biomolecular tweezers could help researchers to study how mechanical forces affect the biochemical activity of cells and proteins. The devices, too small to see without a microscope, use opposing magnetic and electrophoretic forces to precisely stretch the cells and molecules, holding them in position so that the activity of receptors and other biochemical activity can be studied.

Arrays of the tweezers could be combined to study multiple molecules and cells simultaneously, providing a high-throughput capability for assessing the effects of mechanical forces on a broad scale.

For example, a cell that's binding the extracellular matrix may bind with one receptor while the matrix is being stretched, and a different receptor when it's not under stress. Those binding differences could drive changes in cell phenotype and affect processes such as cell differentiation. A device like this will allow us to interrogate what the specific binding sites are and what the specific binding triggers are.

Scientists have been able to study how single cells or proteins are affected by mechanical forces, but their activity can vary considerably from cell-to-cell and among molecules. The new tweezers, which are built using nanolithography, can facilitate studying thousands or more cells and proteins in aggregate.

At the center of the tweezers are few micron polystyrene microbeads that contain superparamagnetic nanoparticles. The tiny beads are engineered to adhere to a sample being studied. That sample is attached to a bead on one side, and to a magnetic pad on the other. The magnet draws the bead toward it, while an electrophoretic force created by current flowing through a gold wiring pattern pushes the bead away. The device simultaneously pushes and pulls on the same particle.

Because the forces can be varied, the tweezers can be used to study structures of widely different size scales, from protein molecules to cells. Absolute forces in the nano-Newton range applied by the two sources overcome the much smaller effects of Brownian motion and thermal energy, allowing the tweezers to hold the cells or molecules without constant adjustment.

As a proof of principle for the system, the researchers demonstrated its ability to distinguish between antigen binding to loaded magnetic beads coated with different antibodies. When a sufficient upward force is applied, non-specific antibody coated beads are displaced from the antigen-coated device surface, while beads coated with the specific antibody are more strongly attracted to the surface and retained on it.

Nanotechnology Breakthroughs by International Business Machines Corporation (IBM)

2014-03-15T15:19:00.004+05:30

Source : http://www-03.ibm.com/press/attachments/28488.pdf

In chronological order:

1981 - IBM scientists invent the Scanning Tunneling Microscope, giving ready access for the first time to the nanoscale world of individual atoms and molecules on electrically conducting substrates.

1986 -The Atomic Force Microscope is invented by IBM and Stanford University scientists, quickly becoming the workhorse of nanoscience, providing general purpose imaging and manipulation in the nanometer realm.

1986 - IBM scientists Gerd Binnig and Heinrich Rohrer win the Nobel Prize in Physics for the Scanning Tunneling Microscope.

1988 - IBM scientists observe photon emission from local nanometer-sizes areas stimulated by a scanning tunneling microscope, allowing phenomena such as luminescence and fluorescence to be studied on the nanometer scale.

1989 - IBM Fellow Don Eigler is the first to controllably manipulate individual atoms on a surface, using the STM to spell out "I-B-M" by positioning 35 xenon atoms, and in the process, perhaps creating the world’s smallest corporate logo.

1991 -IBM scientists demonstrate an atomic switch, a significant milestone on the road to the eventual design of electronic devices of atomic dimensions.

1993 – Scientists at IBM and NEC independently discover single-wall carbon nanotubes and the methods to produce them using metal catalysts.

1996 - IBM scientists extend STM manipulation techniques to position individual molecules at room temperature for the first time.

1996 - The world's smallest abacus is created out of 10 atoms by scientists at IBM, another major milestone in engineering at the nanoscale.

1998 - IBM scientists and partners discover a molecular wheel, which shows promise for making nanoscale mechanical gears and motors.

2000 - IBM and university researchers develop nanomechanical sensors using tiny silicon fingers to detect minute quantities of biochemical substances and to recognize specific patterns of DNA.

2001 - IBM's "constructive destruction" method overcomes major hurdle for building computer chips beyond silicon with a method to separate semiconducting and metallic nanotubes to form a working transistor on the nanoscale

2001 - IBM scientists unveil the world's first single-molecule computer circuit, carbon nanotube transistors transformed into logic-performing integrated circuits, a major step toward molecular computers.

2002 - IBM researchers build world's smallest operating computing circuits using a molecule cascade, wherein molecules move in a manner analogous to falling dominos.

2003 -- Scientists from IBM, Columbia University and the University of New Orleans demonstrate the first three-dimensional self assembly of magnetic and semiconducting nanoparticles, a modular assembly method that enables scientists to bring almost any materials together.

2003 - IBM scientists demonstrate the world's smallest solid-state light emitter, suggesting that carbon nanotubes may be suitable for optoelectroinics.

2004 -- IBM scientists develop a new technique called “spin-flip spectroscopy” to study the properties of atomic-scale magnetic structures. They use this technique to measure a fundamental magnetic property of a single atom -- the energy required to flip its magnetic orientation.

2004 – IBM scientists measure the tiny magnetic force from a single electron spin using an ultra sensitive magnetic resonance force microscope, showing the potential of vastly extending the sensitivity of magnetic resonance imaging (MRI).

2004 -- IBM scientists manipulate and control the charge state of individual atoms. This ability to add or remove an electron charge to or from an individual atom can help expand the scope of atom-scale research. Switching between different charge states of an individual atom could enable unprecedented control in the study of chemical reactivity, optical properties, or magnetic moment.

2004 -- IBM scientists make breakthrough in nanoscale imaging -- the ability to detect the faint magnetic signal from a single electron buried inside a solid sample is a major milestone toward creating a microscope that can make three-dimensional images of molecules with atomic resolution.

2005 -- Using nanoelectronic fabrication technologies, IBM researchers create a tiny device that slows the speed of light, representing a big advance toward the eventual use of light in place of electricity in the connection of electronic components, potentially leading to vast improvements in the performance of computers and other electronic systems.

2006 -- IBM researchers build the first complete electronic integrated circuit around a single “carbon nanotube” molecule, a new material that shows promise for providing enhanced performance over today’s standard silicon semiconductors. The achievement is significant because the circuit was built using standard semiconductor processes and used a single molecule as the base for all components in the circuit, rather than linking together individually-constructed components. This can simplify manufacturing and provide the consistency needed to more thoroughly test and adjust the material for use in these applications.

2006 -- IBM scientists develop a powerful new technique for exploring and controlling atomic magnetism, an important tool in the quest not only to understand the operation of future computer circuit and data-storage elements as they shrink toward atomic dimensions, but also to lay the foundation for new materials and computing devices that leverage atom-scale magnetic phenomena.

2006 – In a study investigating the fundamentals of molecular electronics, the quantum mechanical effects of attaching gold atoms to a molecule were elucidated. The work demonstrated that it is not only possible to control the atomic-scale geometry of a metal-molecule contact, but also its coupling strength and the phase of the orbital wave function at the contact point.

2007 -- IBM demonstrates the first-ever manufacturing application of "self assembly" used to create a vacuum -- the ultimate insulator -- around nanowires for next-generation microprocessors for its airgap chip technique.

2007 - IBM researchers in collaboration with scientists from the ETH Zurich demonstrate a new, efficient and precise technique to “print” at the nanoscale.

2007 - IBM unveils two nanotechnology breakthroughs as building blocks for atomic structures and devices: Magnetic atom milestone brings single-atom data storage closer to reality; single-molecule switching could lead to molecular computers.

2007 - IBM researchers develop magnetic resonance imaging (MRI) techniques to visualize nanoscale objects. This technique brings MRI capability to the nanoscale level for the first time.

2008 - IBM scientists, in collaboration with the University of Regensburg in Germany, are the first ever to measure the force it takes to move individual atoms on a surface.

2009 – IBM Research builds microscope with 100 million times finer resolution than current MRI, extending three-dimensional MRI to the nanoscale.

2009 - IBM scientists reach a landmark in the field of nanoelectronics: the development and demonstration of novel techniques to measure the distribution of energy and heat in powered carbon nanotube devices. By employing these techniques, IBM researchers have determined how the energy of electrical currents running through nanotubes is converted into heat and dissipated into collective vibrations of the nanotube's atoms, as well as surface vibrations of the substrate beneath it.

2009 - IBM scientists in collaboration with the University of Regensburg, Germany, and Utrecht University, Netherlands, for the first time demonstrate the ability to measure the charge state of individual atoms using non contact atomic force microscopy.

2009 - In an effort to achieve energy-aware computing, the Swiss Federal Institute of Technology Zurich (ETH) and IBM plan to build a first-of-a-kind water-cooled supercomputer that will directly repurpose excess heat for the university buildings. The system is expected to save up to 30 tons of CO2 per year, compared to a similar system using today's cooling technologies.

2009 – IBM launches new research effort for next generation electric energy storage, exploring battery technologies to drive electric vehicle adoption and make energy grids more efficient.

Breakthrough in transistor fabrication without semiconductors

2013-09-03T18:49:00.001+05:30

Michigan Technological University scientists led by professor of physics Yoke Khin Yap have created a quantum tunneling device that acts like like an FET transistor and works at room temperature without using semiconducting materials.

The trick was to use boron nitride nanotubes (BNNTs) with quantum dots made from gold. When sufficient voltage is applied to the device, it switches from insulator to a conducting state. When the voltage is low or turned off, it reverts to its natural state as an insulator. There is no leakage current of electrons escaping from the gold dots into the insulating BNNTs, thus keeping the tunneling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat, limiting miniaturization of transistors.

Carpets of boron nitride nanotubes, which are insulators and highly resistant to electrical charge were grown on a substrate. Using lasers, quantum dots (QDs) of gold are deposited as small as three nanometers across on the tops of the BNNTs, forming QDs-BNNTs. BNNTs are the perfect substrates for these quantum dots due to their small, controllable, and uniform diameters, as well as their insulating nature. BNNTs confine the size of the dots that can be deposited. Now if we applied biasing, electrons jumped very precisely from gold dot to gold dot, which is known as quantum tunneling.

Other people have made transistors that exploit quantum tunneling. However, those tunneling field effect transistors have only worked in low temperature. The gold islands have to be on the order of nanometers across to control the electrons at room temperature. If they are too big, too many electrons can flow.

For further reading
http://www.readcube.com/articles/10.1002/adma.201301339?

New material for fuel cell catalyst

2013-09-01T18:11:00.000+05:30

Efficient, robust and economical catalyst materials hold the key to achieving a breakthrough in fuel cell technology. Scientists from Jülich and Berlin have developed a material for converting hydrogen and oxygen to water using a tenth of the typical amount of platinum that was previously required. With the aid of state-of-the-art electron microscopy, the researchers discovered that the function of the nanometre-scale catalyst particles is decisively determined by their geometric shape and atomic structure. This discovery opens up the opportunity for further improved catalysts for energy conversion and storage.

Hydrogen-powered fuel cells are regarded as a clean alternative to conventional combustion engines, as the only substance produced during operation is water. At present, the implementation of hydrogen fuel cells is being hindered by the high material costs of platinum. Large quantities of the expensive noble metal are still required for the electrodes in the fuel cells at which the chemical conversion processes take place. Without the catalytic effect of the platinum, it is not currently possible to achieve the necessary conversion rates.

As catalysis takes place at the surface of the platinum only, material can be saved and, simultaneously, the efficiency of the electrodes improved by using platinum nanoparticles, thus increasing the ratio of platinum surface to material required. Although the tiny particles are around ten thousand times smaller than the diameter of a human hair, the surface area of a kilogram of such particles is huge.

However, more platinum can be saved by mixing it with nickel or copper. Scientist have succeeded in developing efficient metallic catalyst particles for converting hydrogen and oxygen to water using only a tenth of the typical amount of platinum that was previously required.

The new catalyst consists of octrahedral-shaped nanoparticles of a platinum-nickel alloy. The researchers discovered that the unique manner in which the platinum and nickel atoms arrange themselves on the surfaces to accelerate the chemical reaction between hydrogen and oxygen to form water. Round or cubic particles have different atomic arrangements at the surface and are therefore less effective catalysts for the chemical reaction, which could be compensated by using increased amounts of noble metal.

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

2013-09-01T18:10:00.000+05:30

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

Gold nanoparticles to observe the interaction of molecules in liquid

2013-08-04T20:17:00.000+05:30

Thanks to a new device that is the size of a human hair, it is now possible to detect molecules in a liquid solution and observe their interactions. This is of major interest for the scientific community, as there is currently no reliable way of examining both the behavior and the chemical structure of molecules in a liquid in real time.

This process could potentially make a whole new class of measurements possible by bringing together infrared detection techniques and gold nanoparticles, which would be a critical step in understanding basic biological functions as well as key aspects of disease progression and treatment. This could also prove useful for studying the behaviour of proteins, medicines and cells in the blood or pollutants in water.

The device is based on infrared absorption spectroscopy. Infrared light can already be used to detect elements: The beam excites the molecules, which start to vibrate in different ways depending on their size, composition and other properties. It's like a guitar string vibrating differently depending on its length. The unique vibration of each type of molecule acts as a signature for that molecule.

This technique works very well in dry environments but not at all well in aqueous environments. A large number of molecules need to be present for them to be detected. It's also more difficult to detect molecules in water, as when the beam goes through the solution, the water molecules vibrate as well and interfere with the target molecule's. To get rid of this problem, the researchers have developed a system capable of isolating the target molecules and eliminating interferences.

The device is made up of miniature fluidic chambers with nano scale gold particles on one side of its cover. Now to catch a particular molecule gold nanoparticle is attached with specific antibodies. Once the target element is introduced in to the small chamber, nanoparticles get attached to the target element. This technique makes it possible to isolate the target molecules from the rest of the liquid. But this is not the only role the nanoparticles play. They are also capable of concentrating light in nanometer-size volumes around their surface as a result of plasmonic resonance.

In the chamber, the beam doesn't need to pass through the whole solution. Instead, it is sent straight to the nanoparticle, which concentrates the light. Caught in the trap, the target molecules are the only ones that are so intensely exposed to the photons. The reaction between the molecules and the infrared photons is extremely strong, which means they can be detected and observed very precisely. This technique enables to observe molecules in-situ as they react with elements in their natural environment. This could prove extremely useful for both medicine and biology.

Electrodes made by Carbon Nanotubes for Recording Neuron Activity

2013-07-10T00:39:00.002+05:30

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.

New Graphene Sensor for more sensitive camera

2013-06-02T01:28:00.001+05:30

Recently scientists at Nanyang Technological University invented a new camera sensor which could revolutionize current camera market by its ability to take clear photos in dim conditions.

The new sensor made from graphene, is believed to be the first to be able to detect broad spectrum light, from the visible to mid-infrared, with high photoresponse or sensitivity. This means it is suitable for use in all types of cameras, including infrared cameras, traffic speed cameras, satellite imaging and more.

Not only is the graphene sensor 1,000 times more sensitive to light than current imaging sensors found in today's cameras, it also uses 10 times less energy as it operates at lower voltages. When mass produced, graphene sensors are estimated to cost at least five times cheaper due to its high electrical conductivity among other properties such as durability and flexibility.

This sensor could have great impact not only on the consumer imaging industry, but also in satellite imaging and communication industries, as well as the mid-infrared applications, While designing this sensor, current manufacturing practices have been kept in mind. This means the industry can in principle continue producing camera sensors using the CMOS (complementary metal-oxide-semiconductor) process, which is the prevailing technology used by the majority of factories in the electronics industry. Therefore manufacturers can easily replace the current base material of photo sensors with our new nano-structured graphene material. Cost of manufacturing imaging sensors will fall, which eventually leads to cheaper cameras with longer battery life, if this is adopted by industry.

Researcher came up with an innovative idea to create nanostructures on graphene which will trap light-generated electron particles for a much longer time, resulting in a much stronger electric signal. Such electric signals can then be processed into an image, such as a photograph captured by a digital camera. The trapped electrons is the key to achieving high photoresponse in graphene, which makes it far more effective than the normal CMOS or CCD (charge-coupled device) image sensors. Essentially, the stronger the electric signals generated, the clearer and sharper the photos. The performance of graphene sensor can be further improved through nanostructure engineering of graphene.

Myths about toxic Nanosilver busted

2013-04-01T13:06:00.000+05:30

According to Finnish-Estonian joint research with data obtained on two crustacean species, there is apparently no reason to consider silver nanoparticles more dangerous for aquatic ecosystems than silver ions. The results were reported in the journal Environmental Science and Pollution Research late last year.

Part of the magic of nano-science is that on the scale of a billionth of a metre, matter and materials behave in ways that are not yet known. It is also not very clear what types of effects the nano version of the parent matter will have on its environment.

Due to the fact that silver in nanoparticle form is bactericidal and also fungicidal and also prevents the reproduction of those organisms, it is now used in various consumer goods ranging from wound dressing products to sportswear, says Jukka Niskanen from the Laboratory of Polymer Chemistry at the University of Helsinki, Finland.

While the usefulness of silver has been established, the debate over the toxicity mechanisms of its various forms to microorganisms, but also to non-target species continues. Anne Kahru, Head of the Laboratory of Environmental Toxicology at the National Institute of Chemical Physics and Biophysics, Estonia, highlights on a new field: nanoecotoxicology.

So far, little is known about the environmental effects of silver nanoparticles and their toxicity to aquatic organisms. A joint study from the University of Helsinki and the National Institute of Chemical Physics and Biophysics, Estonia of two types of silver nanoparticles to aquatic crustaceans Daphnia magna and Thamnocephalus platyurus , shows that silver nanoparticles are apparently no more hazardous to aquatic ecosystems than a water-soluble silver salt. The study compared the ecotoxicity of silver nanoparticles and a water-soluble silver salt.

The conclusion was that the environmental risks caused by silver nanoparticles are seemingly not higher than those caused by a silver salt. However, more research is required to reach a clear understanding of the safety of silver-containing particles.

Indeed, silver nanoparticles were found to be ten times less toxic than the soluble silver nitrate -- a soluble silver salt used for the comparison.

To explain this phenomenon, the researchers refer to the variance in the bioavailability of silver to crustaceans in different tested media.

It has been observed that the inorganic and organic compounds dissolved in natural waters (such as humus), water hardness and sulfides have a definite impact on the bioavailability of silver. Due to this, the toxicity of both types of tested nanoparticles and the silver nitrate measured in the course of the study was lower in natural water than in artificial fresh water.

The toxicity of silver nanoparticles and silver ions was studied using two aquatic crustaceans, a water flea (Daphnia magna) and a fairy shrimp (Thamnocephalus platyurus). Commercially available protein-stabilised particles and particles coated with a water-soluble, non-toxic polymer, specifically synthesised for the purpose, were used in the study. First, the polymers were produced utilising a controlled radical polymerisation method. Synthetic polymer-grafted silver particles were then produced by attaching the water-soluble polymer to the surface of the silver with a sulfur bond.

It was previously known from other studies and research results that silver changes the functioning of proteins and enzymes. It has also been shown that silver ions can prevent the replication of DNA. Concerning silver nanoparticles, tests conducted on various species of bacteria and fungi have indicated that their toxicity varies. For example, gram-negative bacteria such as Escherichia coli are more sensitive to silver nanoparticles than gram-positive ones (such as Staphylococcus aureus). The difference in sensitivity is caused by the structural differences of the cell membranes of the bacteria. The cellular toxicity of silver nanoparticles in mammals has been studied as well. It has been suggested that silver nanoparticles enter cells via endocytosis and then function in the same manner as in bacterial cells, damaging DNA and hindering cell respiration. Electron microscope studies have shown that human skin is permeable to silver nanoparticles and that the permeability of damaged skin is up to four times higher than that of healthy skin.

Self healing iPhone!

2013-03-04T23:32:00.001+05:30

Nissan has developed a "self-healing" iPhone case that erases scratches.

Scratch Shield paint developed by Nissan can repair small scratches on a surface in a few hours.
Made from polyrotaxane, the chemical structure of the paint enables it to react to small chips and fill in the gaps.
It's currently used on the Nissan Murano, 370Z, and X-Trail, but the auto manufacturer has found a much larger market for its smart paint in iPhones.

Nissan is testing its Scratch Shield iPhone case with beta customers and some journalists, although this automotive writer was left out of the loop.
Its iPhone case is made from ABS plastic to create a tight and rigid case, and its coated with Scratch Shield paint.

Material That Slows Light Opens New Possibilities in Solar Energy

2013-02-18T19:02:00.000+05:30

University at Buffalo engineers have created a more efficient way to catch rainbows, an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research.

They developed a hyperbolic metamaterial waveguide, which is an advanced microchip made of alternate ultra-thin films of metal and semiconductors and insulators. The waveguide halts and ultimately absorbs each frequency of light, at slightly different places in a vertical direction, to catch series of wavelengths.

Electromagnetic absorbers have been studied for many years, especially for military radar systems. Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band.

Ultra-thin films are developed that will slow the light and therefore allow much more efficient absorption. Light is made of photons; because they move extremely fast are difficult to control. In their initial attempts to slow light, researchers relied upon cryogenic gases. But because cryogenic gases are very cold, this process is not industrially feasible.

Earlier researchers made nano-scale-sized grooves in metallic surfaces at different depths, which altered the optical properties of the metal. While the grooves worked, they had limitations; the energy of the incident light cannot be transferred onto the metal surface efficiently, which hindered its use for practical applications. The hyperbolic metamaterial waveguide solves that problem because it is a large area of patterned film that can collect the incident light efficiently. It is referred to as an artificial medium with subwavelength features whose frequency surface is hyperboloid, which allows it to capture a wide range of wavelengths in different frequencies including visible, near-infrared, mid-infrared, terahertz and microwaves.

It could lead to advancements in an array of fields. For example, in electronics there is a phenomenon known as crosstalk, in which a signal transmitted on one circuit or channel creates an undesired effect in another circuit or channel. The on-chip absorber could potentially prevent this.

The on-chip absorber may also be applied to solar panels and other energy-harvesting devices. It could be especially useful in mid-infrared spectral regions as thermal absorber for devices that recycle heat after sundown.

Technology such as the Stealth bomber involves materials that make planes, ships and other devices invisible to radar, infrared, sonar and other detection methods. Because the on-chip absorber has the potential to absorb different wavelengths at a multitude of frequencies, it could be useful as a stealth coating material.

For further reading: http://www.nature.com/srep/2013/130213/srep01249/full/srep01249.html

Carbon Atom for Ultra-Small Energy-Efficient Electronic Devices

2013-01-23T20:25:00.000+05:30

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.

“Antenna” like InP nanowires for high solar efficiency

2013-01-21T23:25:00.000+05:30

In a recent study, researchers from Lund University in Sweden have shown how nanowires could pave the way for more efficient and cheaper solar cells. This finding first shows that it is possible to use nanowires to manufacture solar cells.

Research on solar cell nanowires is on the rise globally. Until now the unattained dream figure was ten per cent efficiency; but now scientists are able to report an efficiency of 13.8 per cent.

The nanowires are made of the semiconductor material indium phosphide and work like antennae that absorb sunlight and generate power. The nanowires are assembled on surfaces of one square millimetre which can hold four million nanowires. A nanowire solar cell can produce an effect per active surface unit several times greater than today's silicon cells.

Nanowire solar cells have not yet made it beyond the laboratory, but the plan is that the technology could be used in large solar power plants in sunny regions.

The Lund researchers have now managed to identify the ideal diameter of the nanowires and how to synthesize them.

The right size is essential for the nanowires to absorb as many photons as possible. If they are just a few tenths of a nanometre, their function is significantly impaired. The silicon solar cells that are used to supply electricity for domestic use are relatively cheap, but inefficient because they are only able to utilise a limited part of the effect of the sunlight. The reason is that one single material can only absorb part of the spectrum of the light.

Research carried out alongside that on nanowire technology therefore aims to combine different types of semiconductor materials to make efficient use of a broader part of the solar spectrum. The disadvantage of this is that they become extremely expensive and can therefore only be used in applications such as on satellites and military planes.

However, this is not the case with nanowires. Because of their small dimensions, the same sort of material combinations can be created with much less effort, which offers higher efficiency at a low cost. The process is also less complicated. In this study, the researchers have shown that the nanowires can generate power at the same level as a thin film of the same material, even if they only cover around 10 per cent of the surface rather than 100 per cent.

For further studies:

http://www.sciencemag.org/content/early/2013/01/16/science.1230969

Excellent Strategy for Fingerprint Identification using Gold nanoparticles

2012-11-18T16:19:00.002+05:30

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.