Tag Archives: nanotechnology

How To Replace The Thick Glass Lenses by 2D Metalens

In optics, the era of glass lenses may be waning. In recent years, physicists and engineers have been designing, constructing and testing different types of ultrathin materials that could replace the thick glass lenses used today in cameras and imaging systems. Critically, these engineered lenses — known as metalenses — are not made of glass. Instead, they consist of materials constructed at the nanoscale into arrays of columns or fin-like structures. These formations can interact with incoming light, directing it toward a single focal point for imaging purposes.

But even though metalenses are much thinner than glass lenses, they still rely on “high aspect ratio” structures, in which the column or fin-like structures are much taller than they are wide, making them prone to collapsing and falling over. Furthermore, these structures have always been near the wavelength of light they’re interacting with in thickness — until now. In a paper published in the journal Nano Letters, a team from the University of Washington (UW) and the National Tsing Hua University in Taiwan announced that it has constructed functional metalenses that are one-tenth to one-half the thickness of the wavelengths of light that they focus. Their metalenses, which were constructed out of layered 2D materials, were as thin as 190 nanometers — less than 1/100,000ths of an inch thick.

This is the first time that someone has shown that it is possible to create a metalens out of 2D materials,” said senior and co-corresponding author Arka Majumdar, a UW assistant professor of physics and of electrical and computer engineering.

Their design principles can be used for the creation of metalenses with more complex, tunable features, added Majumdar, who is also a faculty researcher with the UW’s Molecular Engineering & Sciences Institute and Institute for Nano-Engineered Systems.

Source: https://www.washington.edu/

Double Layers Of Graphene Conduct Current Without Resistance

Scientists at the Helmholtz Zentrum Berlin (HZB) have found evidence that double layers of graphene have a property that may let them conduct current completely without resistance. They probed the bandstructure at BESSY II with extremely high resolution ARPES and could identify a flat area at a surprising location.

Carbon atoms have diverse possibilities to form bonds. Pure carbon can therefore occur in many forms, as diamond, graphite, as nanotubes, football molecules or as a honeycomb-net with hexagonal meshes, graphene. This exotic, strictly two-dimensional material conducts electricity excellently, but is not a superconductor. But perhaps this can be changed.

In April 2018, a group at MIT, USA, showed that it is possible to generate a form of superconductivity in a system of two layers of graphene under very specific conditions: To do this, the two hexagonal nets must be twisted against each other by exactly the magic angle of 1.1°. Under this condition a flat band forms in the electronic structure. The preparation of samples from two layers of graphene with such an exactly adjusted twist is complex, and not suitable for mass production. Nevertheless, the study has attracted a lot of attention among experts.

But there is one more, much simpler way of flat band formation. This was shown by a group at the HZB around Prof. Oliver Rader and Dr. Andrei Varykhalov with investigations at BESSY II. The samples were provided by Prof. Thomas Seyller, TU Chemnitz. There they are produced using a process that is also suitable for the production of larger areas and in large quantities: A silicon carbide crystal is heated until silicon atoms evaporate from the surface, leaving first a single-layer of graphene on the surface, and then a second layer of graphene. The two graphene layers are not twisted against each other, but lie exactly on top of each other.

This flat area is a prerequisite for superconductivity but only if it is situated exactly at the so-called Fermi energy. In the case of the two-layer graphene, its energy level is only 200 milli-electron volts below the Fermi energy, but it is possible to raise the energy level of the flat area to the Fermi energy either by doping with foreign atoms or by applying an external voltage, the so-called gate voltage.

The findings have been Published in Science Advances.

Source: https://www.helmholtz-berlin.de/

Stem Cell Therapy Could Treat Alzheimer’s And Parkinson’s

Rutgers scientists have created a tiny, biodegradable scaffold to transplant stem cells and deliver drugs, which may help treat Alzheimer’s and Parkinson’s diseases, aging brain degeneration, spinal cord injuries and traumatic brain injuriesStem cell transplantation, which shows promise as a treatment for central nervous system diseases, has been hampered by low cell survival rates, incomplete differentiation of cells and limited growth of neural connections.

So, Rutgers scientists designed bio-scaffolds that mimic natural tissue and got good results in test tubes and mice. These nano-size scaffolds hold promise for advanced stem cell transplantation and neural tissue engineering. Stem cell therapy leads to stem cells becoming neurons and can restore neural circuits.

It’s been a major challenge to develop a reliable therapeutic method for treating central nervous system diseases and injuries,” said study senior author KiBum Lee, a professor in the Department of Chemistry and Chemical Biology at Rutgers University-New Brunswick. “Our enhanced stem cell transplantation approach is an innovative potential solution.

The researchers, in cooperation with neuroscientists and clinicians, plan to test the nano-scaffolds in larger animals and eventually move to clinical trials for treating spinal cord injury. The scaffold-based technology also shows promise for regenerative medicine.

The study included researchers from Rutgers and Kyung Hee University in South Korea. The results have been published in  Nature Communications.

Source: https://www.eurekalert.org/

Swarm Of NanoRobots Can Improve The Efficiency Of Any Machine

The research team of Prof. Massimiliano Esposito of the University of Luxembourg studied the thermodynamics of  nanomachines. All machines convert one form of energy into another form – for example a car engine turns the energy stored in fuel into motion energy. Those processes of energy conversion, described by the theory called thermodynamics, don’t only take place on the macro-level of big machines, but also at the micro-level of molecular machines that drive muscles or metabolic processes and even on the atomic level. The research team of Prof. Massimiliano Esposito of the University of Luxembourg studies the thermodynamics of nanomachines only consisting of a few atoms.

In a paper published in the prestigious scientific journal Physical Review X, they outline how these small machines behave in concert. Their insights could be used to improve the energy efficiency of all kinds of machines, big or small.

Recent progress in nanotechnology has enabled researchers to understand the world in ever-smaller scales and even allows for the design and manufacture of extremely small artificial machines.

There is evidence that these machines are far more efficient than large machines, such as cars. Yet in absolute terms, the output is low compared to the needs we have in daily life applications,” explains Tim Herpich, PhD student at Esposito’s research group and main author of the paper. “That is why we studied how the nanomachines interact with each other and looked at how ensembles of those small machines behave. We wanted to see if there are synergies when they act in concert.”

The researchers found that the nanomachines under certain conditions start to arrange in “swarms” and synchronise their movements. “We could show that the synchronisation of the machines triggers significant synergy effects, so that the overall energy output of the ensemble is far greater than the sum of the individual outputs,” said Prof. Esposito. While this is basic research, the principles outlined in the paper could potentially be used to improve the efficiency of any machine in the future, the researcher explains.

In order to simulate and study the energetic behaviour of swarms of nanomachines, the scientists created mathematical models that are based on existing literature and outcomes of experimental research.

Source: https://wwwen.uni.lu/

How To Make Concrete Leaner, Greener, Stronger And More Elastic

Rice University scientists have developed micron-sized calcium silicate spheres that could lead to stronger and greener concrete, the world’s most-used synthetic material. To Rice materials scientist Rouzbeh Shahsavari and graduate student Sung Hoon Hwang, the spheres represent building blocks that can be made at low cost and promise to mitigate the energy-intensive techniques now used to make cement, the most common binder in concrete.

The researchers formed the spheres in a solution around nanoscale seeds of a common detergent-like surfactant. The spheres can be prompted to self-assemble into solids that are stronger, harder, more elastic and more durable than ubiquitous Portland cement.

Packed, micron-scale calcium silicate spheres developed at Rice University are a promising material that could lead to stronger and more environmentally friendly concrete

Cement doesn’t have the nicest structure,” said Shahsavari, an assistant professor of materials science and nanoengineering. “Cement particles are amorphous and disorganized, which makes it a bit vulnerable to cracks. But with this material, we know what our limits are and we can channel polymers or other materials in between the spheres to control the structure from bottom to top and predict more accurately how it could fracture.”

He said the spheres are suitable for bone-tissue engineering, insulation, ceramic and composite applications as well as cement.

Source: https://news.rice.edu/

Spray-On Electronic Nano-Antennas For Wearables

The promise of wearables, functional fabrics, the Internet of Things, and their “next-generation” technological cohort seems tantalizingly within reach. But researchers in the field will tell you a prime reason for their delayed “arrival” is the problem of seamlessly integrating connection technology — namely, antennas — with shape-shifting and flexible “things.”

But a breakthrough by researchers in Drexel’s College of Engineering, could now make installing an antenna as easy as applying some bug spray. In research recently published in Science Advances, the group reports on a method for spraying invisibly thin antennas, made from a type of two-dimensional, metallic material called MXene, that perform as well as those being used in mobile devices, wireless routers and portable transducers.

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Spray-applied MXene antennas could open the door for new applications in smart technology, wearables and IoT devices

This is a very exciting finding because there is a lot of potential for this type of technology,” said Kapil Dandekar, PhD, a professor of Electrical and Computer Engineering in the College of Engineering, who directs the Drexel Wireless Systems Lab, and was a co-author of the research. “The ability to spray an antenna on a flexible substrate or make it optically transparent means that we could have a lot of new places to set up networks — there are new applications and new ways of collecting data that we can’t even imagine at the moment.”

Source: https://drexel.edu/

New Solar Cells Could Harvest 85% of Visible Light

Scientists have developed a photoelectrode that can harvest 85 percent of visible light in a 30 nanometers-thin semiconductor layer between gold layers, converting light energy 11 times more efficiently than previous methods. In the pursuit of realizing a sustainable society, there is an ever-increasing demand to develop revolutionary solar cells or artificial photosynthesis systems that utilize visible light energy from the sun while using as few materials as possible. The research team, led by Professor Hiroaki Misawa of the Research Institute for Electronic Science at Hokkaido University (Japan), has been aiming to develop a photoelectrode that can harvest visible light across a wide spectral range by using gold nanoparticles loaded on a semiconductor. But merely applying a layer of gold nanoparticles did not lead to a sufficient amount of light absorption, because they took in light with only a narrow spectral range.

In the study published in Nature Nanotechnology, the research team sandwiched a semiconductor, a 30-nanometer titanium dioxide thin-film, between a 100-nanometer gold film and gold nanoparticles to enhance light absorption. When the system is irradiated by light from the gold nanoparticle side, the gold film worked as a mirror, trapping the light in a cavity between two gold layers and helping the nanoparticles absorb more light. To their surprise, more than 85 percent of all visible light was harvested by the photoelectrode, which was far more efficient than previous methods. Gold nanoparticles are known to exhibit a phenomenon called localized plasmon resonance which absorbs a certain wavelength of light.

“Our photoelectrode successfully created a new condition in which plasmon and visible light trapped in the titanium oxide layer strongly interact, allowing light with a broad range of wavelengths to be absorbed by gold nanoparticles,” says Hiroaki Misawa.

 Source: https://www.global.hokudai.ac.jp/

Portable Machine Harvests Water From Air

Driven by the scarcity of supply, climate change and ground watershed depletion, scientists present a design for a first of its kind portable harvester that mines freshwater from the atmosphere. For thousands of years, people in the Middle East and South America have extracted water from the air to help sustain their populations. Researchers and students from the University of Akron drew inspiration from those examples to develop a lightweight, battery-powered freshwater harvester that could someday take as much as 10 gallons (37,8 liters) per hour from the air, even in arid locations.

I was visiting China, which has a freshwater scarcity problem. There’s investment in wastewater treatment, but I thought that effort alone was inadequate,University of Akron professor Shing-Chung (Josh) Wong said.

Instead of relying on treated wastewater, Wong explained, it might be more prudent to develop a new type of water harvester that takes advantage of abundant water particles in the atmosphere. Freshwater makes up less than 3 percent of the earth’s water sources, and three quarters of that is locked up as ice in the north and south poles. Most water sustainability research is directed toward water supply, purification, wastewater treatment and desalination. Little attention has been paid to water harvesting from atmospheric particles.

Harvesting water from the air has a long history. Thousands of years ago, the Incas of the Andean region collected dew and channeled it into cisterns. More recently, some research groups have been developing massive mist and fog catchers in the Andean mountains and in Africa. Wong’s harvester is directed towards the most abundant atmospheric water sources and uses ground-breaking nanotechnology. If successful, it will produce an agile, lightweight, portable, freshwater harvester powered by a lithium-ion battery.

By experimenting with different combinations of polymers that were hydrophilic — which attracts water — and hydrophobic — which discharges water, the team concluded that a water harvesting system could indeed be fabricated using nanofiber technology. Unlike existing methods, Wong’s harvester could work in arid desert environments because of the membrane’s high surface-area-to-volume ratio. It also would have a minimal energy requirement. “We could confidently say that, with recent advances in lithium-ion batteries, we could eventually develop a smaller, backpack-sized device,” Wong said.

Source: https://www.uakron.edu/

2D Material Revolutionizes Solar Fuel Generation

Following the isolation of graphene in 2004, a race began to synthesize new two-dimensional materials. 2D materials are single-layer substances with a thickness of between one atom and a few nanometers (billionths of a meter). They have unique properties linked to their reduced dimensionality and play a key role in the development of nanotechnology and nanoengineering.

An international group of researchers including Brazilian scientists affiliated with the University of Campinas (UNICAMP) have succeeded in producing a new material with these characteristics.

The researchers extracted a 2D material they call hematene from ordinary iron ore like that mined in many parts of the world, including Brazil. The material is only three atoms thick and is thought to have enhanced photocatalytic properties.

International group of researchers including Brazilian scientists obtain new material from iron ore with application as a photocatalyst

The research was conducted at the Center for Computational Engineering and Sciences (CCES), one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP, and during a research internship abroad that was also supported by FAPESP via a specific scholarship.

Douglas Soares Galvão, a researcher at CCES and one of the authors of the study, told Agência FAPESP about the discovery. “The material we synthesized can act as a photocatalyst to split water into hydrogen and oxygen, so that electricity can be generated from hydrogen, for example, as well as having several other potential applications,” he said.

The new material was exfoliated from hematite, one of the most common minerals on earth and the main source of iron, which is the cheapest metal, used in many products and above all to make steel.

Unlike carbon and its 2D form graphene, hematite is a non-van der Waals material, meaning it is held together by 3D bonding networks rather than by nonchemical and comparatively weaker atomic van der Waals interactions, which are noncovalent (they do not involve the sharing of one or more pairs of electrons by the atoms that participate in the bond).

Because it is a naturally occurring mineral, has highly oriented, large crystals and is a non-van der Waals material, the researchers believe that hematite is an excellent precursor for the exfoliation of novel 2D materials.

Most of the 2D materials synthesized to date were derived from samples of van der Waals solids. Non-van der Waals 2D materials with highly ordered atomic layers and large grains are still rare,” Galvão said.

Hematene was synthesized by the liquid-phase exfoliation of hematite ore in an organic solvent, N,N-dimethylformamide (DMF). Transmission electron microscopy confirmed the exfoliation and formation of hematene in single sheets with a thickness of only three iron and oxygen atoms (monolayer) and in randomly stacked sheets (bilayer).

The innovation is described in an article published in Nature Nanotechnology.

Source: http://agencia.fapesp.br/

 

Orthodontic Surgery Without Incision

Researchers at the Technion-Israel Institute of Technology have developed a nanotechnology that replaces the surgical scalpel with an “enzymatic blade.” In an article published recently in ACS Nano, the researchers describe the application of this technology in a surgical procedure in the oral cavity. The application spares the pain associated with orthodontic surgeries and significantly reduces tissue recovery time.

The study was led by Dr. Assaf Zinger, within the framework of his doctoral research, mentored by Assistant Professor Avi Schroeder, the director of the Laboratory of Targeted Drug Delivery and Personalized Medicine at the Wolfson Faculty of Chemical Engineering. The novel technology is based on rational use of enzymesbiological molecules the body uses to repair itself, as well as on use of nanoparticles for achieving a targeted therapeutic profile.

In the United States alone, approximately five million people undergo orthodontic treatment each year. To speed up treatment, which typically lasts about two years, many undergo invasive surgery, in which collagen fibers that connect the tooth to the underlying bone tissue are cut.

The technology developed at the Technion softens the collagen fibers via the targeted release of collagenase – an enzyme that specifically breaks down collagen. Using techniques developed in Schroeder’s lab, the collagenase is packaged into liposomesnanometric vesicles. As long as the collagenase particles are packaged in the liposome, they are inactive. But with this special nanotechnology, an ointment is applied on the target site, so that the enzyme begins to gradually leak from the liposome and soften the collagen fibers. The researchers performed a series of tests to determine the collagenase concentration optimal for the procedure and to accelerate tissue repair thereafter.

Source: http://t3news.trdf.co.il/