Tag Archives: materials

How To Arrange Nanoparticules With a Vinaigrette

Materials scientists at Duke University have theorized a new “oil-and-vinegar” approach to engineering self-assembling materials of unusual architectures made out of spherical nanoparticles. The resulting structures could prove useful to applications in optics, plasmonics, electronics and multi-stage chemical catalysis. Left to their own tendencies, a system of suspended spherical nanoparticles designed to clump together will try to maximize their points of contact by packing themselves as tightly as possible. This results in the formation of either random clusters or a three-dimensional, crystalline structure.

But materials scientists often want to build more open structures of lower dimensions, such as strings or sheets, to take advantage of certain phenomena that can occur in the spaces between different types of particles.  In the new study, Gaurav Arya, associate professor of mechanical engineering and materials science at Duke, proposes a method that takes advantage of the layers formed by liquids that, like a bottle of vinaigrette left on the shelf for too long, refuse to mix together.

When spherical nanoparticles are placed into such a system, they tend to form a single layer at the interface of the opposing liquids. But they don’t have to stay there. By attachingoil” or “vinegarmolecules to the particles’ surfaces, researchers can make them float more on one side of the dividing line than the other.

The particles want to maximize their number of contacts and form bulk-like structures, but at the same time, the interface of the different liquids is trying to force them into two layers,” said Arya. “So you have a competition of forces, and you can use that to form different kinds of unique and interesting structures.”

Arya’s idea is to precisely control the amount that each spherical nanoparticle is repelled by one liquid or the other. And according to his calculations, by altering this property along with others such as the nanoparticles’ composition and size, materials scientists can make all sorts of interesting shapes, from spindly molecule-like structures to zig-zag structures where only two nanoparticles touch at a time. One could even imagine several different layers working together to arrange a system of nanoparticles.

In the proof-of-concept paper, the nanoparticles could be made out of anything. Gold or semiconductors could be useful for plasmonic and electrical devices, while other metallic elements could catalyze various chemical reactions. The opposing substrates that form the interface, meanwhile, are modeled after various types of polymers that could also be used in such applications.

The novel approach appeared online on March 25 in the journal ACS Nano.

Source: https://pratt.duke.edu/

New Quantum Sensor Improves Cancer Treatment

A new quantum sensor developed by researchers at the University of Waterloo’s Institute for Quantum Computing (IQC) in Canada, has proven it can outperform existing technologies and promises significant advancements in long-range 3D imaging and monitoring the success of cancer treatments.

The sensors are the first of their kind and are based on semiconductor nanowires that can detect single particles of light with high timing resolution, speed and efficiency over an unparalled wavelength range, from ultraviolet to near-infrared.

The technology also has the ability to significantly improve quantum communication and remote sensing capabilities.

Interaction of single incident photon pulses and a tapered semiconductor nanowire array photodetector

A sensor needs to be very efficient at detecting light. In applications like quantum radar, surveillance, and nighttime operation, very few particles of light return to the device,” said principal investigator Michael Reimer, an IQC faculty member and assistant professor in the Faculty of Engineering’s electrical and computer engineering department. “In these cases, you want to be able to detect every single photon coming in.

The next generation quantum sensor designed in Reimer’s lab is so fast and efficient that it can absorb and detect a single particle of light, called a photon, and refresh for the next one within nanoseconds. The researchers created an array of tapered nanowires that turn incoming photons into electric current that can be amplified and detected.

Remote sensing, high-speed imaging from space, acquiring long range high resolution 3D images, quantum communication, and singlet oxygen detection for dose monitoring in cancer treatment are all applications that could benefit from the kind of robust single photon detection that this new quantum sensor provides.

The semiconducting nanowire array achieves its high speed, timing resolution and efficiency thanks to the quality of its materials, the number of nanowires, doping profile and the optimization of the nanowire shape and arrangement. The sensor detects a broad spectrum of light with high efficiency and high timing resolution, all while operating at room temperature. Reimer emphasizes that the spectrum absorption can be broadened even further with different materials.

This device uses Indium Phosphide (InP) nanowires. Changing the material to Indium Gallium Arsenide (InGaAs), for example, can extend the bandwidth even further towards telecommunications wavelengths while maintaining performance,” Reimer said. “It’s state of the art now, with the potential for further enhancements.”

Once the prototype is packaged with the right electronics and portable cooling, the sensor is ready for testing beyond the lab.  “A broad range of industries and research fields will benefit from a quantum sensor with these capabilities,” said Reimer.

Source: https://uwaterloo.ca/

Atom-Thin Processor

An international team of researchers has reported a breakthrough in fabricating atom-thin processors — a discovery that could have far-reaching impacts on nanoscale chip production and in labs across the globe where scientists are exploring 2D materials for ever-smaller and –faster semiconductors.

The team, headed by New York University Tandon School of Engineering Professor of Chemical and Biomolecular Engineering Elisa Riedo, outlined the research results in the latest issue of Nature Electronics.They demonstrate that lithography using a probe heated above 100 degrees Celsius outperformed standard methods for fabricating metal electrodes on 2D semiconductors such as molybdenum disulfide (MoS₂). Such transitional metals are among the materials that scientists believe may supplant silicon for atomically small chips.

The team’s new fabrication method — called thermal scanning probe lithography (t-SPL) — offers a number of advantages over today’s electron beam lithography (EBL). First, thermal lithography significantly improves the quality of the 2D transistors, offsetting the Schottky barrier, which hampers the flow of electrons at the intersection of metal and the 2D substrate. Also, unlike EBL, the thermal lithography allows chip designers to easily image the 2D semiconductor and then pattern the electrodes where desired. Also, t-SPL fabrication systems promise significant initial savings as well as operational costs: They dramatically reduce power consumption by operating in ambient conditions, eliminating the need to produce high-energy electrons and to generate an ultra-high vacuum. Finally, this thermal fabrication method can be easily scaled up for industrial production by using parallel thermal probes.

Source: https://engineering.nyu.edu/

Graphene’s Consequences On Human Health

As the drive to commercialise graphene continues, it is important that all safety aspects are thoroughly researched and understood. The Graphene Flagship project has a dedicated Work Package studying the impact of graphene and related materials on our health, as well as their environmental impact. This enables safety by design to become a core part of innovation.

Researches and companies are currently using a range of materials such as few layered graphene, graphene oxide and heterostructures. The first step to assess the toxicology is to fully characterise these materials. This work overviews the production and characterisation methods, and considers different materials, which biological effects depend on their inherent properties.


One of the key messages is that this family of materials has varying properties, thus displaying varying biological effects. It is important to emphasize the need not only for a systematic analysis of well-characterized graphene-based materials, but also the importance of using standardised in vitro or in vivo assays for the safety assessment,” says Bengt Fadeel, lead author of this paper working at Graphene Flagship partner Karolinska Institutet, Sweden.

This review correlates the physicochemical characteristics of graphene and related materials to the biological effects. A classification based on lateral dimensions, number of layers and carbon-to-oxygen ratio allows us to describe the parameters that can alter graphene’s toxicology. This can orient future development and use of these materials,” explains Alberto Bianco, from Graphene Flagship partner CNRS, France and deputy leader of the Graphene Flagship Work Package on Health and Environment.

Source: https://graphene-flagship.eu/

Cheap Nano-Catalysts For Better Fuel Cells

Researchers at Daegu Gyeongbuk Institute of Science & Technology (DGIST) in Korea have developed nano-catalysts that can reduce the overall cost of clean energy fuel cells, according to a study published in the Journal of Applied Catalysis B: Environmental.

Polymer electrolyte membrane fuel cells (PEMFCs) transform the chemical energy produced during a reaction between hydrogen fuel and oxygen into electrical energy. While PEMFCs are a promising source of clean energy that is self-contained and mobile – much like the alkaline fuel cells used on the US Space Shuttle – they currently rely on expensive materials. Also, the substances used for catalysing these chemical reactions degrade, raising concerns about reusability and viability.

DGIST energy materials scientist Sangaraju Shanmugam and his team have developed active and durable catalysts for PEMFCs that can reduce the overall manufacturing costs. The catalysts were nitrogen-doped carbon nanorods with ceria and cobalt nanoparticles on their surfaces; essentially carbon nanorods containing nitrogen, cobalt and ceria. Ceria (CeO2), a combination of cerium and oxygen, is a cheap and environmentally friendly semiconducting material that has excellent oxygen reduction abilities.

The fibres were made using a technique known as electrospinning, in which a high voltage is applied to a liquid droplet, forming a charged liquid jet that then dries midflight into uniform, nanosized particles. The researchers’ analyses confirmed that the ceria and cobalt particles were uniformly distributed in the carbon nanorods and that the catalysts showed enhanced electricity-producing capacity.

The ceria-supported cobalt on nitrogen-doped carbon nanorod catalyst was found to be more active and durable than cobalt-only nitrogen-doped carbon nanorods and platinum/carbon. They were explored in two important types of chemical reactions for energy conversion and storage: oxygen reduction and oxygen evolution reactions.

The researchers conclude that ceria could be considered among the most promising materials for use with cobalt on nitrogen-doped carbon nanorods to produce stable catalysts with enhanced electrochemical activity in PEMFCs and related devices.

Source: https://www.dgist.ac.kr/

How To Use The Body’s Inbuilt Healing System

Imperial researchers have developed a new bioinspired material that interacts with surrounding tissues to promote healing. Materials are widely used to help heal wounds: Collagen sponges help treat burns and pressure sores, and scaffold-like implants are used to repair broken bones. However, the process of tissue repair changes over time, so scientists are looking to biomaterials that interact with tissues as healing takes place.

Now, Dr Ben Almquist and his team at Imperial College London have created a new molecule that could change the way traditional materials work with the body. Known as traction force-activated payloads (TrAPs), their method lets materials talk to the body’s natural repair systems to drive healing.

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The researchers say incorporating TrAPs into existing medical materials could revolutionise the way injuries are treated.

Our technology could help launch a new generation of materials that actively work with tissues to drive healing,” said Dr Almquist, from mperial’s Department of Bioengineering.
After an injury, cells ‘crawl’ through the collagen ‘scaffolds’ found in wounds, like spiders navigating webs. As they move, they pull on the scaffold, which activates hidden healing proteins that begin to repair injured tissue. The researchers in the study designed TrAPs as a way to recreate this natural healing method. They folded the DNA segments into three-dimensional shapes known as aptamers that cling tightly to proteins. Then, they attached a customisable ‘handle’ that cells can grab onto on one end, before attaching the opposite end to a scaffold such as collagen.
During laboratory testing of their technique, they found that cells pulled on the TrAPs as they crawled through the collagen scaffolds. The researchers tailor TrAPs to release specific therapeutic proteins based on which cells are present at a given point in time.

This is the first time scientists have activated healing proteins using differing cell types in man-made materials. The technique mimics healing methods found in nature. “Creatures from sea sponges to humans use cell movement to activate healing. Our approach mimics this by using the different cell varieties in wounds to drive healing,” explains Dr Almquist.”

This approach is adaptable to different cell types, so could be used in a variety of injuries such as fractured bones, scar tissue after heart attacks, and damaged nerves. New techniques are also desperately needed for patients whose wounds won’t heal despite current interventions, like diabetic foot ulcers, which are the leading cause of non-traumatic lower leg amputationsTrAPs are relatively straightforward to create and are fully man-made, meaning they are easily recreated in different labs and can be scaled up to industrial quantities.

TrAPs could harness the body’s natural healing powers to repair bone

TrAPs provide a flexible method of actively communicating with wounds, as well as key instructions when and where they are needed. This intelligent healing is useful during every phase of the healing process, has the potential to increase the body’s chance to recover, and has far-reaching uses on many different types of wounds. This technology could serve as a conductor of wound repair, orchestrating different cells over time to work together to heal damaged tissues,” said Dr Almquist.

The findings are published in Advanced Materials.

Source: https://www.imperial.ac.uk/

 

Megalibrary To Boost Discovery of New Materials

Different eras of civilization are defined by the discovery of new materials, as new materials drive new capabilities. And yet, identifying the best material for a given application—catalysts, light-harvesting structures, biodiagnostic labels, pharmaceuticals and electronic devices—is traditionally a slow and daunting task. The options are nearly infinite, particularly at the nanoscale (a nanometer is one-billionth of a meter) where material propertiesoptical, structural, electrical, mechanical and chemical—can significantly change, even at a fixed composition.

A new study published this week in the Proceedings of the National Academy of Sciences (PNAS) supports the efficacy of a potentially revolutionary new tool developed at Northwestern University to rapidly test millions (even billions) of nanoparticles to determine the best for a specific use.

Laser-induced heating of nanoparticles on micropillars for carbon nanotube growth

When utilizing traditional methods to identify new materials, we have barely scratched the surface of what is possible,” said Northwestern’s Chad A. Mirkin, the study’s corresponding author and a world leader in nanotechnology research and its applications. “This research provides proof-of-concept—that this powerful approach to discovery science works.”

The novel tool utilizes a combinatorial library, or megalibrary, of nanoparticles in a very controlled way. (A combinatorial library is a collection of systematically varied structures encoded at specific sites on a surface). The libraries are created using Mirkin’s Polymer Pen Lithography (PPL) technique, which relies on arrays (sets of data elements) with hundreds of thousands of pyramidal tips to deposit individual polymerdots” of various sizes and composition, each loaded with different metal salts of interest, onto a surface. Once heated, these dots are reduced to metal atoms forming a single nanoparticle at fixed composition and size.

By going small, we create two advantages in high throughput materials discovery,” said Mirkin, the executive director of Northwestern’s International Institute for Nanotechnology (IIN). “First, we can pack millions of features into square-centimeter areas, creating a path for making the largest and most complex libraries, to date. Second, by working at the sub-100 nanometer-length scale, size can become a library parameter, and much of the action, for example, in the field of catalysis, is on this length scale.”

Source: https://news.northwestern.edu/

How To Shrink Objects To The Nanoscale

MIT researchers have invented a way to fabricate nanoscale 3-D objects of nearly any shape. They can also pattern the objects with a variety of useful materials, including metals, quantum dots, and DNA.

MIT engineers have devised a way to create 3-D nanoscale objects by patterning a larger structure with a laser and then shrinking it. This image shows a complex structure prior to shrinking.

It’s a way of putting nearly any kind of material into a 3-D pattern with nanoscale precision,” says Edward Boyden, the Y. Eva Tan Professor in Neurotechnology and an associate professor of biological engineering and of brain and cognitive sciences at MIT. Using the new technique, the researchers can create any shape and structure they want by patterning a polymer scaffold with a laser. After attaching other useful materials to the scaffold, they shrink it, generating structures one thousandth the volume of the original.

These tiny structures could have applications in many fields, from optics to medicine to robotics, the researchers say. The technique uses equipment that many biology and materials science labs already have, making it widely accessible for researchers who want to try it. Boyden, who is also a member of MIT’s Media Lab, McGovern Institute for Brain Research, and Koch Institute for Integrative Cancer Research, is one of the senior authors of the paper, which appears in the Dec. 13 issue of Science. The other senior author is Adam Marblestone, a Media Lab research affiliate, and the paper’s lead authors are graduate students Daniel Oran and Samuel Rodriques.

As they did for expansion microscopy, the researchers used a very absorbent material made of polyacrylate, commonly found in diapers, as the scaffold for their nanofabrication process. The scaffold is bathed in a solution that contains molecules of fluorescein, which attach to the scaffold when they are activated by laser light.

Using two-photon microscopy, which allows for precise targeting of points deep within a structure, the researchers attach fluorescein molecules to specific locations within the gel. The fluorescein molecules act as anchors that can bind to other types of molecules that the researchers add.

You attach the anchors where you want with light, and later you can attach whatever you want to the anchors,” Boyden says. “It could be a quantum dot, it could be a piece of DNA, it could be a gold nanoparticle.” “It’s a bit like film photography — a latent image is formed by exposing a sensitive material in a gel to light. Then, you can develop that latent image into a real image by attaching another material, silver, afterwards. In this way implosion fabrication can create all sorts of structures, including gradients, unconnected structures, and multimaterial patterns,” Oran explains.

Source: http://news.mit.edu/

Ultrathin, Ultralight NanoCardboard For Aerospace

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure. Now, a team of Penn Engineers has demonstrated a new material they call “nanocardboard,” an ultrathin equivalent of corrugated paper cardboard. A square centimeter of nanocardboard weighs less than a thousandth of a gram and can spring back into shape after being bent in half.

Nanocardboard is made out of an aluminum oxide film with a thickness of tens of nanometers, forming a hollow plate with a height of tens of microns. Its , similar to that of corrugated cardboard, makes it more than ten thousand times as stiff as a solid plate of the same mass.

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Nanocardboard is made out of an aluminum oxide film with a thickness of tens of nanometers, forming a hollow plate with a height of tens of microns. Its sandwich structure, similar to that of corrugated cardboard, makes it more than ten thousand times as stiff as a solid plate of the same mass. A square centimeter of nanocardboard weighs less than a thousandth of a gram and can spring back into shape after being bent in half.

Nanocardboard‘s stiffness-to-weight ratio makes it ideal for aerospace and microrobotic applications, where every gram counts. In addition to unprecedented mechanical properties, nanocardboard is a supreme thermal insulator, as it mostly consists of empty space. Future work will explore an intriguing phenomenon that results from a combination of properties: shining a light on a piece of nanocardboard allows it to levitate. Heat from the light creates a difference in temperatures between the two sides of the plate, which pushes a current of air molecules out through the bottom.

Igor Bargatin, Assistant Professor of Mechanical Engineering, along with lab members Chen Lin and Samuel Nicaise, led the study.

They published their results in the journal Nature Communications.

Source: https://phys.org/

New Materials For New Processors

Computers used to take up entire rooms. Today, a two-pound laptop can slide effortlessly into a backpack. But that wouldn’t have been possible without the creation of new, smaller processors — which are only possible with the innovation of new materials. But how do materials scientists actually invent new materials? Through experimentation, explains Sanket Deshmukh, an assistant professor in the chemical engineering department of Virginia Tech whose team’s recently published computational research might vastly improve the efficiency and costs savings of the material design process.

Deshmukh’s lab, the Computational Design of Hybrid Materials lab, is devoted to understanding and simulating the ways molecules move and interact — crucial to creating a new material. In recent years, materials scientists have employed machine learning, a powerful subset of artificial intelligence, to accelerate the discovery of new materials through computer simulations. Deshmukh and his team have recently published research in the Journal of Physical Chemistry Letters demonstrating a novel machine learning framework that trainson the fly,” meaning it instantaneously processes data and learns from it to accelerate the development of computational models. Traditionally the development of computational models are “carried out manually via trial-and-error approach, which is very expensive and inefficient, and is a labor-intensive task,” Deshmukh explained.

This novel framework not only uses the machine learning in a unique fashion for the first time,” Deshmukh said, “but it also dramatically accelerates the development of accurate computational models of materials.” “We train the machine learning model in a ‘reverse’ fashion by using the properties of a model obtained from molecular dynamics simulations as an input for the machine learning model, and using the input parameters used in molecular dynamics simulations as an output for the machine learning model,” said Karteek Bejagam, a post-doctoral researcher in Deshmukh’s lab and one of the lead authors of the study.

This new framework allows researchers to perform optimization of computational models, at unusually faster speed, until they reach the desired properties of a new material.

Source: https://vtnews.vt.edu/