Giant Step For NanoMaterial Manufacturing

Tiny fibrils extracted from plants have been getting a lot of attention for their strength. These nanomaterials have shown great promise in outperforming plastics, and even replacing them. A team led by Aalto University (Finland) has now shown another remarkable property of nanocelluloses: their strong binding properties to form new materials with any particle.

Cohesion, the ability to keep things together, from the scale of nanoparticles to building sites is inherent to these nanofibrils, which can act as mortar to a nearly infinite type of particles as described in the study. The ability of nanocelluloses to bring together particles into cohesive materials is at the root of the study that links decades of research into nanoscience towards manufacturing.

In a paper just published in Science Advances, the authors demonstrate how nanocellulose can organize itself in a multitude of different ways by assembling around particles to form highly robust materials.

Nanocellulose can also form structures known from pulp technology with the particles

This means that nanocelluloses induce high cohesion in particulate materials in a constant and controlled manner for all particles types. Because of such strong binding properties, such materials can now be built with predictable properties and therefore easily engineered’, explained  the main author, Dr Bruno Mattos, The moment anytime a material is created from particles, one has to first come up with a way to generate cohesion, which has been very particle dependent, ‘Using nanocellulose, we can overcome any particle dependency’, Mattos adds.

The universal potential of using nanocellulose as a binding component rises from their ability to form networks at the nanoscale, that adapt according to the given particles. Nanocelluloses bind micrometric particles, forming sheet-like structures, much like the paper-mâché as done in schools. Nanocellulose can also form tiny fishnets to entrap smaller particles, such as nanoparticles. Using nanocellulose, materials built from particles can be formed into any shape using an extremely easy and spontaneous process that only needs water. Importantly, the study describes how these nanofibers form network following precise scaling laws that facilitates their implementation. This development is especially timely in the era of the nanotechnologies, where combining nanoparticles in larger structures is essential. As Dr Blaise Tardy points out, ‘New property limits and new functionalities are regularly showcased at the nanoscale, but implementation in the real world is rare. Unraveling the physics associated with the scaling of the cohesion of nanofibers is therefore a very exciting first step towards connecting laboratory findings with current manufacturing practices’. For any success, strong binding among the particles is needed, an opportunity herein offered by nanocellulose.

Source: https://www.aalto.fi/

AI-driven Robots Improve Solar Cells

In July 2018, Curtis Berlinguette, a materials scientist at the University of British Columbia in Vancouver, Canada, realized he was wasting his graduate student’s time and talent. He was asked to refine a key material in solar cells to boost its electrical conductivity. But the number of potential tweaks was overwhelming, from spiking the recipe with traces of metals and other additives to varying the heating and drying times.

 

Ada, an AI-driven robot, searches for new solar cell designs at the University of British Columbia

There are so many things you can go change, you can quickly go through 10 million [designs] you can test,” Berlinguette says.

So he and colleagues outsourced the effort to a single-armed robot overseen by an artificial intelligence (AI) algorithm. Dubbed Ada, the robot mixed different solutions, cast them in films, performed heat treatments and other processing steps, tested the films’ conductivity, evaluated their microstructure, and logged the results. The AI interpreted each experiment and determined what to synthesize next. At a meeting of the Materials Research Society (MRS) here last week, Berlinguette reported that the system quickly homed in on a recipe and heating conditions that created defect-free films ideal for solar cells. “What used to take us 9 months now takes us 5 days,” Berlinguette says.

Other material scientists also reported successes with such “closed loop” systems that combine the latest advances in automation with AI that directs how the experiments should proceed on the fly. Drug developers, geneticists, and investigators in other fields had already melded AIs and robots to design and do experiments, but materials scientists had lagged behind. DNA synthesizers can be programmed to assemble any combination of DNA letters, but there’s no single way to synthesize, process, or characterize materials, making it exponentially more complicated to develop an automated system that can be guided by an AI. Materials scientists are finally bringing such systems online. “It’s a superexciting area,” says Benji Maruyama, a materials scientist with the U.S. Air Force Research Laboratory east of Dayton, Ohio. “The closed loop is what is really going to make progress in materials research go orders of magnitude faster.”

With more than 100 elements in the periodic table and the ability to combine them in virtually limitless ways, the number of possible materials is daunting. “The good news is there are millions to billions of undiscovered materials out there,” says Apurva Mehta, a materials physicist at the Stanford Synchrotron Radiation Lightsource in Menlo Park, California. The bad news, he says, is that most are unremarkable, making the challenge of finding gems a needle-in-the-haystack problem. Robots have already helped. They are now commonly used to mix dozens of slightly different recipes for a material, deposit them on single wafers or other platforms, and then process and test them simultaneously. But simply plodding through recipe after recipe is a slow route to a breakthrough, Maruyama says. “High throughput is a way to do lots of experiments, but not a lot of innovation.”

To speed the process, many teams have added in computer modeling to predict the formula of likely gems. “We’re seeing an avalanche of exciting materials coming from prediction,” says Kristin Persson of Lawrence Berkeley National Laboratory (LBNL) in California, who runs a large-scale prediction enterprise known as the Materials Project. But those systems still typically rely on graduate students or experienced scientists to evaluate the results of experiments and determine how to proceed. Yet, “People still need to do things like sleep and eat,” says Keith Brown, a mechanical engineer at Boston University (BU). So, like Berlinguette, Brown and his colleagues built an AI-driven robotics system. Their goal was to find the toughest possible 3D-printed structures. Toughness comes from a blend of high strength and ductility, and it varies depending on the details of a structure, even if the material itself doesn’t change. Predicting which shape will be toughest isn’t feasible, Brown says. “You have to do the experiment.”

Source: https://www.sciencemag.org/

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/

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.

CLICK ON THE IMAGE TO ENJOY THE VIDEO

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/

 

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/