19th July 2016
Smallest ever hard disk writes information atom by atom
Scientists in the Netherlands, working at the limits of miniaturisation, have used one bit per atom to create 1 kilobyte of data storage.
Every day, modern society creates more than a billion gigabytes of new data. To store all this information, it is increasingly important that each single bit occupies as little space as possible. A team of scientists at the Kavli Institute of Nanoscience at Delft University, Netherlands, managed to bring this reduction to the ultimate limit: they built a memory of 1 kilobyte (8,000 bits), where each bit is represented by the position of one single chlorine atom.
"In theory, this storage density would allow all books ever created by humans to be written on a single post stamp", says lead scientist Sander Otte. They reached a storage density of 500 Terabits per square inch (Tbpsi), 500 times better than the best commercial hard disk currently available. His team reports on this breakthrough in Nature Nanotechnology.
In 1959, physicist Richard Feynman challenged his colleagues to engineer the world at the smallest possible scale. In his famous lecture, There's Plenty of Room at the Bottom, he speculated that a platform allowing us to arrange individual atoms, in an exact orderly pattern, would make it possible to store one piece of information per atom. To honour the visionary Feynman, Otte and his team have now coded a section of Feynman's lecture on an area 100 nanometres wide.
STM scan (96 nm wide, 126 nm tall) of the 1 kB memory, written to a section of Feynman's lecture, There's Plenty of Room at the Bottom.
The team used a scanning tunnelling microscope (STM), in which a sharp needle probes the atoms of a surface, one by one. Using these probes, scientists not only see the atoms, but can also push them around: "You could compare it to a sliding puzzle", Otte explains. "Every bit consists of two positions on a surface of copper atoms, and one chlorine atom that we can slide back and forth between these two positions. If the chlorine atom is in the top position, there is a hole beneath it – we call this a 1. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0." Because the chlorine atoms are surrounded by other chlorine atoms, except near the holes, they keep each other in place. That is why this method with holes is much more stable than methods with loose atoms and more suitable for data storage.
The researchers from Delft organised their memory in blocks of 8 bytes (64 bits). Each block has a marker, made of the same type of 'holes' as the raster of chlorine atoms. Inspired by the pixelated square barcodes (QR codes) often used to scan tickets for airplanes and concerts, these markers work like miniature QR codes that carry information about the precise location of the block on the copper layer. The code will also indicate if a block has been damaged, for instance due to some local contaminant or an error in the surface. This allows memory to be scaled up easily to very big sizes, even if the copper surface is not entirely perfect.
The new method offers excellent prospects in terms of stability and scalability. Still, this type of memory should not be expected in commercial use anytime soon: "In its current form, the memory can operate only in very clean vacuum conditions and at liquid nitrogen temperature (77 K), so the actual storage of data on an atomic scale is still some way off," explains Otte. "But through this achievement, we have certainly come a big step closer".
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18th July 2016
Graphene-infused packaging is a million times better at blocking moisture
Plastic packaging might seem impenetrable – and sometimes nearly impossible to remove – but water molecules can still pass through. And this permeability to moisture can limit the lifespan of a product. To better protect goods such as electronics and medicines, U.S. and Indian scientists have developed a new kind of packaging that incorporates a single layer of graphene. They report their material, which reduces by a million-fold how much water can get through, in the journal ACS Nano.
These days, packaging is everywhere, sometimes even on individual fruits or vegetables. Wrapping products from food to electronics in plastic films can protect against dust, bacteria and to some extent water. But to maximise the lifetime of moisture-sensitive devices such as organic light-emitting diodes (OLED) for more than a year, for example, the packaging must restrict water vapour from entering at a rate of less than 0.000001 (10-6) grams per square metre every day, according to study author Praveen C. Ramamurthy. Today's typical packaging is far from achieving that goal. Ramamurthy and colleagues wanted to see whether adding graphene to flexible polymer films would help.
The researchers synthesised a layer of graphene by chemical vapour deposition and using a simple and scalable process, transferred the graphene to a polymer film. Water vapour permeated the material at the target rate of less than 10-6 grams per square metre per day. An accelerated aging test showed that an organic photovoltaic device wrapped in the graphene-infused film would have a lifetime of more than a year compared to less than half an hour if packaged in the polymer without the graphene.
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22nd April 2016
Ultra-long carbyne stronger than graphene is synthesised for the first time
An international team of scientists reports synthesising ultra-long carbyne inside double-walled nanotubes. This exotic form of carbon is even stronger than graphene.
European researchers have successfully stabilised chains of more than 6,400 carbon atoms, using double-walled nanotubes. In a study, published by the journal Nature Materials, they demonstrate a new route for the production of carbyne – infinitely long carbon chains whose mechanical properties surpass those of diamond and graphene. Their method involved using double-walled carbon nanotubes, as shown in these illustrations, to protect the carbon chain from extreme instability in ambient conditions.
Elemental carbon appears in many different forms, some of which are very well-known and have been thoroughly studied: diamond, graphite, graphene, fullerenes, nanotubes and carbyne. Within this "carbon family", carbyne (a truly one-dimensional carbon structure) is the only one that has not been synthesised until now, despite having been studied for more than 50 years. Chemists across the world had been trying to synthesise increasingly longer carbyne chains by using stabilising agents, but the longest chain obtained so far (achieved in 2010) was only 44 carbon atoms.
Now, a research group at the University of Vienna, led by Prof Thomas Pichler, has presented a new, simple means for stabilising these carbon chains with a record-breaking length of more than 6,400 carbon atoms. The previous record has therefore been broken by two orders of magnitude. To do this, they used the confined space inside a double-walled carbon nanotube as a "nano-reactor" to make the ultra-long carbon chains grow, while providing the chains great stability. This could be tremendously important for future applications.
The researchers unambiguously confirmed the existence of these chains by means of structural and optical probes. This direct experimental proof can be seen as a promising step towards obtaining perfectly linear carbon chains, the researchers' final objective. Theoretical studies have shown that after having linear chains grow inside a carbon nanotube, the hybrid system could have a metallic nature – making it possible to control electronic properties. In other words, this new system is not only interesting from a chemical point of view, it could also be very important in the field of nano devices.
According to theoretical models, carbyne has mechanical properties unmatched by any known material. It has twice the tensile stiffness of graphene and nearly three times that of diamond. Furthermore, its electronic properties point towards new nano-electronic applications, such as the development of new magnetic semiconductors, high power density batteries, or in quantum spin transport electronics (spintronics).
However, the researchers point out that to achieve this would require extracting these ultra-long, linear carbon chains from the double-walled nanotube containing them and stabilising them in a liquid environment.
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11th April 2016
The first high-res 3D images of DNA segments
First-of-their-kind images by researchers at Berkeley Lab could aid in the use of DNA to build nanoscale devices.
Credit: Berkeley Lab
An international team working at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has captured the first high-resolution 3-D images from individual double-helix DNA segments, attached at either end of gold nanoparticles. The images detail the flexible structure of the DNA segments, which appear as nanoscale "jump ropes".
This unique imaging capability, pioneered by Berkeley Lab scientists, could aid in the use of DNA segments as building blocks for molecular devices that function as nanoscale drug-delivery systems, markers for biological research, and components for computer memory and electronic devices. It could also lead to images of disease-relevant proteins that have proven elusive for other imaging techniques, and of the assembly process that forms DNA from separate, individual strands.
The shapes of the coiled DNA strands, which were sandwiched between polygon-shaped gold nanoparticles, were reconstructed in 3-D using a cutting-edge electron microscope technique called individual-particle electron tomography (IPET). This was combined with a protein-staining process and sophisticated software that provided structural details down to a scale of just 2 nanometres (nm), or about two billionths of a metre.
"We had no idea about what the double-strand DNA would look like between the nanogold particles," said Gang Ren, a Berkeley Lab scientist who led the research. "This is the first time for directly visualising an individual double-strand DNA segment in 3-D."
While the 3-D reconstructions show the basic nanoscale structure of the samples, Ren said the next step will be to improve the resolution to the sub-nanometre scale: "Even in this current state, we begin to see 3-D structures at 1- to 2-nanometre resolution," he said. "Through better instrumentation and improved computational algorithms, it would be promising to push the resolution to that visualising a single DNA helix within an individual protein."
The technique, he said, has already excited interest among some prominent pharmaceutical companies and nanotechnology researchers, and his science team already has dozens of related research projects being planned. In future studies, they could attempt to improve the imaging resolution for complex structures that incorporate more DNA segments as a sort of "DNA origami," Ren said. Researchers hope to build and better characterise nanoscale molecular devices using DNA segments that can, for example, store and deliver drugs to targeted areas in the body.
"DNA is easy to program, synthesise and replicate, so it can be used as a special material to quickly self-assemble into nanostructures and to guide the operation of molecular-scale devices," he said. "Our current study is just a proof of concept for imaging these kinds of molecular devices' structures."
His team's work is published in the journal Nature Communications.
Berkeley Lab researchers Gang Ren (standing) and Lei Zhang. Photo by Roy Kaltschmidt/Berkeley Lab.
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17th February 2016
Tiny crystal stores 360TB of data for billions of years
Scientists have announced a major step forward in creating "5D" data storage that can survive for billions of years.
Scientists at the University of Southampton, England, have achieved a major step forward in the creation of digital data storage that is capable of surviving for billions of years. Using nanostructured glass, researchers from the University's Optoelectronics Research Centre (ORC) have developed the recording and retrieval processes of five dimensional (5D) digital data by femtosecond laser writing.
The storage allows unprecedented properties including 360 terabytes (TB) per disc capacity, thermal stability up to 1,000°C and a virtually unlimited lifetime at room temperature (or 13.8 billion years at 190°C), opening a new era of eternal data archiving. As an extremely stable and safe form of portable memory, the technology could be highly useful in organisations with big archives, such as national archives, museums and libraries, to ensure their information and records are kept perfectly preserved.
The technology was first experimentally demonstrated in July 2013, when a simple 300 kb text file was recorded in 5D. Now, major documents from throughout human history – such as the Universal Declaration of Human Rights, Newton's Opticks, Magna Carta and Kings James Bible – have been saved as digital copies that could survive the human race.
The documents were recorded using an ultrafast laser, producing extremely short and intense pulses of light. The file is written in three layers of nanostructured dots separated by five micrometres (a millionth of a metre). The self-assembled nanostructures change how light travels through glass, modifying the polarisation of light, which is then read by a combination of optical microscope and a polariser, similar to that found in Polaroid sunglasses.
Coined as the "Superman memory crystal", as the glass memory has been compared to the "memory crystals" used in the Superman films, the data is recorded via self-assembled nanostructures created within fused quartz. The information encoding is realised in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures.
Professor Peter Kazansky, from the ORC, comments: "It is thrilling to think that we have created the technology to preserve documents and information and store it in space for future generations. This technology can secure the last evidence of our civilisation: all we've learnt will not be forgotten."
The researchers are presenting their research today at the International Society for Optical Engineering Conference in San Francisco, USA. Their invited paper is titled "Eternal 5D data storage by ultrafast laser writing in glass." The team are now looking for industry partners to further develop and commercialise their ground-breaking new technology.
2nd February 2016
Graphene shown to safely interface with neurons in the brain
Researchers in Europe have demonstrated that graphene can be successfully interfaced with neurons, while maintaining the integrity of these vital nerve cells. It is believed this could lead to greatly improved brain implants.
A new study published in the journal ACS Nano demonstrates how it is possible to interface graphene with neurons, whilst maintaining the integrity of these vital nerve cells. The research was part of the EU's Graphene Flagship – a €1 billion project that aims to bring graphene from laboratories into commercial applications within 10 years. The study involved a collaboration between nanotechnologists, chemists, biophysicists and neurobiologists from the University of Trieste in Italy, the University Castilla-La Mancha in Spain and the Cambridge Graphene Centre in the UK.
Prof. Laura Ballerini, lead neuroscientist in the study: "For the first time, we interfaced graphene to neurons directly, without any peptide coating used in the past to favour neuronal adhesion. We then tested the ability of neurons to generate electrical signals known to represent brain activities and found that the neurons retained unaltered their neuronal signalling properties. This is the first functional study of neuronal synaptic activity using uncoated, graphene-based materials."
Using electron microscopy and immuno-fluorescence in rat brain cell cultures, the researchers observed that the neurons interfaced well with the untreated graphene electrodes – remaining healthy, transmitting normal electric impulses and, importantly, showing no adverse glial reaction which can lead to damaging scar tissue. This is therefore the first step towards using pristine, graphene-based material for a neuro-interface.
Graphene-based electrodes implanted in the brain could restore sensory functions for amputees or paralysed patients, or treat individuals with motor disorders such as epilepsy or Parkinson's disease. Further into the future, perhaps they could be used to enhance or upgrade the abilities of normal, healthy people too, bringing the age of transhumanism closer to reality.
Too often, the modern electrodes used for neuro-interfaces (based on tungsten or silicon) suffer partial or complete loss of signal over time. This is often caused by scar tissue formation during the electrode insertion and by its rigid nature preventing the electrode from moving with the natural movements of the brain. Graphene, by contrast, appears to be a highly promising material to solve these problems. It has excellent conductivity, flexibility, biocompatibility and stability within the body.
"Hopefully this will pave the way for better deep brain implants to both harness and control the brain, with higher sensitivity and fewer unwanted side effects," said Ballerini.
"These initial results show how we are just at the tip of the iceberg when it comes to the potential of graphene and related materials in bio-applications and medicine," said Professor Andrea Ferrari, Director of the Cambridge Graphene Centre. "The expertise developed at the Cambridge Graphene Centre allows us to produce large quantities of pristine material in solution, and this study proves the compatibility of our process with neuro-interfaces."
21st January 2016
Nanoparticles kill 90% of antibiotic-resistant bacteria
Light-activated nanoparticles able to kill over 90% of antibiotic-resistant bacteria have been demonstrated at the University of Colorado.
Salmonella bacteria under a microscope. Photo by NIAID / Wikipedia.
Antibiotic-resistant bacteria such as Salmonella, E. Coli and Staphylococcus infect some two million people and kill 23,000 in the U.S. each year. Efforts to defeat these so-called "superbugs" have consistently fallen short, due to the bacteria's ability to adapt rapidly and develop immunity to common antibiotics such as penicillin. In 2014, the World Health Organisation declared this a "major global threat" and warned that the world is heading for a post-antibiotic era, in which even common infections and minor injuries which have been treatable for decades can once again kill.
In this ever-escalating evolutionary battle with drug-resistant bacteria, we may soon have an advantage, however, thanks to adaptive, light-activated nanotherapy developed by scientists at the University of Colorado Boulder. Their latest research suggests that the solution to this big global problem might be to think small – very small.
In findings published by the journal Nature Materials, researchers at the Department of Chemical and Biological Engineering and the BioFrontiers Institute describe new light-activated nanoparticles known as "quantum dots." These dots, which are 20,000 times smaller than a human hair and resemble the tiny semiconductors used in consumer electronics, successfully killed 92% of drug-resistant bacterial cells in a lab-grown culture.
"By shrinking these semiconductors down to the nanoscale, we're able to create highly specific interactions within the cellular environment that only target the infection," said Prashant Nagpal, senior author of the study.
Credit: University of Colorado Boulder / BioFrontiers Institute
Previous research has shown that metal nanoparticles – created from silver and gold, among various other metals – can be effective at combating antibiotic resistant infections, but can indiscriminately damage surrounding cells as well. Quantum dots, however, can be tailored to particular infections thanks to their light-activated properties. The dots remain inactive when in darkness, but can be "activated" on command by exposing them to light, allowing researchers to modify the wavelength in order to alter and kill the infected cells.
"While we can always count on these superbugs to adapt and fight the therapy, we can quickly tailor these quantum dots to come up with a new therapy and therefore fight back faster in this evolutionary race," said Nagpal.
The specificity of this innovation may help reduce or eliminate the potential side effects of other treatment methods, as well as provide a path forward for future development and clinical trials.
"Antibiotics are not just a baseline treatment for bacterial infections, but HIV and cancer as well," said Anushree Chatterjee, an assistant professor in the Department of Chemical and Biological Engineering at CU-Boulder and a senior author of the study. "Failure to develop effective treatments for drug-resistant strains is not an option, and that's what this technology moves closer to solving."
Nagpal and Chatterjee are co-founders of PRAAN Biosciences, a Colorado-based startup that can sequence genetic profiles using just a single molecule – technology that may aid in the diagnosis and treatment of superbug strains. The authors have filed a patent on their new quantum dot technology.
19th December 2015
New microscope is 2,000 times faster
A new atomic force microscope developed by MIT can scan images 2,000 times faster than existing commercial models. This allows it to capture near-real-time video of nanoscale processes.
State-of-the-art atomic force microscopes (AFMs) are designed to capture images of structures as small as a fraction of a nanometre – a million times smaller than the width of a human hair. In recent years, AFMs have produced desktop-worthy close-ups of atom-sized structures, from DNA strands to individual bonds changing between molecules. But scanning these images is a meticulous, time-consuming process. AFMs have therefore been used mostly for static samples as they are too slow to capture active, changing environments.
Now engineers at MIT have designed an atomic force microscope that scans images 2,000 times faster than existing commercial models. With this new high-speed instrument, the team produced images of chemical processes taking place at the nanoscale, at a rate that is close to real-time video.
In one demonstration of the instrument’s capabilities, the researchers scanned a 70- by-70-micron sample of calcite as it was first immersed in deionised water and later exposed to sulphuric acid. Zooming into an area of interest, they observed the acid eating away at the calcite, expanding existing nanometre-sized pits in the material that quickly merged and led to a layer-by-layer removal of calcite along the material’s crystal pattern, over a period of several seconds.
Calcite immersed in deionised water.
Sulphuric acid creating pits in the calcite.
Professor of Mechanical Engineering at MIT, Kamal Youcef-Toumi, says the instrument’s sensitivity and speed will enable scientists to watch atomic-sized processes play out as high-resolution “movies.”
“People can see, for example, condensation, nucleation, dissolution, or deposition of material, and how these happen in real-time – things that people have never seen before,” he says. “This is fantastic to see these details emerging. And it will open great opportunities to explore all of this world that is at the nanoscale.”
The MIT researchers' achievement was made possible through an innovative new technique. This involved controlling the movement of the needle over the sample surface with two actuators (a small, fast scanner and a larger, slower one) in combination with a set of algorithms to ensure they never interfered with each other. At present, this method provides scans at eight to 10 frames per second, but further research is underway to increase this.
“We want to go to real video, which is at least 30 frames per second,” Youcef-Toumi says. “Hopefully we can work on improving the instrument and controls so that we can do video-rate imaging while maintaining its large range and keeping it user-friendly. That would be something great to see.”
The team's design and images, which are based on the PhD work of Iman Bozchalooi – now a postdoc in the Department of Mechanical Engineering – appear in the journal Ultramicroscopy.
19th November 2015
Nanosubmarines powered by light
Nano-scale submarines built from 244 atoms and capable of moving at 2 cm per second have been demonstrated by Rice University.
Credit: Loïc Samuel/Rice University
In a study published by Nano Letters, scientists from Rice University in Texas describe how they built and tested nanoscale submarines, which are able to move with incredible speed. The single-molecule, 244-atom submersibles each have a motor powered by ultraviolet light. With each full revolution the motor's tail-like propeller drives the sub forwards a distance of 18 nanometres (nm). However, the motors run at over a million RPM, giving a top speed of nearly two centimetres (0.8 inches) per second: a breakneck pace on the molecular scale.
"These are the fastest-moving molecules ever seen in solution," says chemist James Tour, one of the study authors.
While they can't be steered yet, the study has proved that molecular motors are powerful enough to drive the sub-10-nanometre craft through solutions of moving molecules of about the same size.
From a nano-scale point of view, "this is akin to a person walking across a basketball court with 1,000 people throwing basketballs at him," Tour said.
Tour's group has extensive experience with molecular machines. A decade ago, his lab demonstrated nanocars – single-molecule cars with four wheels, axles and independent suspensions that could be "driven" across a surface. Over the years, many research groups have created microscopic machines featuring motors – but most have either used or generated toxic chemicals. A motor conceived in the last decade by Dutch researchers proved suitable for the Rice submersibles, which were produced in a 20-step chemical synthesis.
"These motors are well-known and used for different things," said Victor García-López, lead author and Rice graduate student. "But we were the first to propose they can be used to propel nanocars – and now submersibles."
Credit: Victor García-López/Rice University
The motors, which operate more like a bacteria's flagellum than a propeller, complete each revolution in four steps. When excited by light, the double bond that holds the rotor to the body becomes a single bond, allowing it to rotate a quarter step. As the motor seeks to return to a lower energy state, it jumps adjacent atoms for another quarter turn. This process repeats as long as the light is on. Once built, the team turned to Gufeng Wang at North Carolina State University to measure how well the nanosubs moved.
"We had used scanning tunnelling microscopy and fluorescence microscopy to watch our cars drive, but that wouldn't work for the submersibles," explained Tour. "They would drift out of focus pretty quickly."
The North Carolina team sandwiched a drop of diluted acetonitrile liquid containing a few nanosubs between two slides, then used a custom confocal fluorescence microscope to hit it from opposite sides with both ultraviolet light (for the motor) and a red laser (for the pontoons). The microscope's laser defined a column of light in the solution, in which tracking occurred, García-López said: "That way, the NC State team could guarantee it was analysing only one molecule at a time."
The team hopes future nanosubs will be able to carry cargoes for medical and other purposes. "There's a path forward," García-López said. "This is the first step, and we've proven the concept. Now we need to explore opportunities and potential applications."
18th October 2015
New crystal captures carbon from humid gas
A new material with micropores might be a way to fight climate change. Scientists have created crystals that capture carbon dioxide much more efficiently than previously known materials, even in the presence of water.
One way to mitigate climate change could be to capture carbon dioxide (CO2) from the air. So far this has been difficult, since the presence of water prevents the adsorption of CO2. Complete dehydration is a costly process. Scientists have now created a stable and recyclable material, where the micropores within the crystal have different adsorption sites for carbon dioxide and water.
“As far as I know, this is the first material that captures CO2 in an efficient way in the presence of humidity,” says Osamu Terasaki, Professor at the Department of Materials and Environmental Chemistry at Stockholm University. “In other cases, there is competition between water and carbon dioxide and water usually wins. This material adsorbs both, but the CO2 uptake is enormous.”
The new material is called SGU-29, named after Sogang University in Korea, and is the result of international cooperation. It is a copper silicate crystal that forms two nanotube regions – one hydrophobic and one hydrophilic – repelling water while trapping carbon dioxide. The material could be used for capturing carbon directly from the atmosphere, and especially to clean emissions from power plants or other sources.
“CO2 is always produced with moisture, and now we can capture CO2 from humid gases. Combined with other systems that are being developed, the waste carbon can be used for new valuable compounds. People are working very hard and I think we will be able to do this within five years. The most difficult part is to capture carbon dioxide, and we have a solution for that now,” concludes Terasaki.
Major advances in carbon capture and storage will be needed if the world is to avoid 2°C or higher of global warming. Current emission plans by the world's nations ahead of the UN climate change conference in Paris next month fall well short of what is truly needed. Materials such as that demonstrated by Terasaki could pave the way towards a new generation of cheaper, more efficient and widespread carbon sequestration in the coming years and decades. His team's research is published this week in the journal Science.