How To Give Strengh To 3D Printed Objects

Allowing users to create objects from simple toys to custom prosthetic parts, plastics are a popular 3D printing material. But these printed parts are mechanically weak — a flaw caused by the imperfect bonding between the individual printed layers that make up the 3D part. Researchers at Texas A&M University, in collaboration with scientists in the company Essentium, Inc. have now developed the technology needed to overcome 3D printing’s “weak spot.” By integrating plasma science and carbon nanotube technology into standard 3D printing, the researchers welded adjacent printed layers more effectively, increasing the overall reliability of the final part.

Texas A&M and Essentium researchers have developed the technology to weld adjacent 3D printed layers more effectively, increasing the reliability of the final product

Finding a way to remedy the inadequate bonding between printed layers has been an ongoing quest in the 3D printing field,” said Micah Green, associate professor in the Artie McFerrin Department of Chemical Engineering. “We have now developed a sophisticated technology that can bolster welding between these layers all while printing the 3D part.”

Plastics are commonly used for extrusion 3D printing, known technically as fused-deposition modeling. In this technique, molten plastic is squeezed out of a nozzle that prints parts layer by layer. As the printed layers cool, they fuse to one another to create the final 3D part. However, studies show that these layers join imperfectly; printed parts are weaker than identical parts made by injection molding where melted plastics simply assume the shape of a preset mold upon cooling. To join these interfaces more thoroughly, additional heating is required, but heating printed parts using something akin to an oven has a major drawback. “If you put something in an oven, it’s going to heat everything, so a 3D-printed part can warp and melt, losing its shape,” Green said. “What we really needed was some way to heat only the interfaces between printed layers and not the whole part.”

To promote inter-layer bonding, the team turned to carbon nanotubes. Since these carbon particles heat in response to electrical currents, the researchers coated the surface of each printed layer with these nanomaterials. Similar to the heating effect of microwaves on food, the team found that these carbon nanotube coatings can be heated using electric currents, allowing the printed layers to bond together.

To apply electricity as the object is being printed, the currents must overcome a tiny space of air between the printhead and the 3D part. One option to bridge this air gap is to use metal electrodes that directly touch the printed part, but Green said this contact can introduce inadvertent damage to the part.

The team collaborated with David Staack, associate professor in the J. Mike Walker ‘66 Department of Mechanical Engineering, to generate a beam of charged air particles, or plasma, that could carry an electrical charge to the surface of the printed part. This technique allowed electric currents to pass through the printed part, heating the nanotubes and welding the layers together.

With the plasma technology and the carbon nanotube-coated thermoplastic material in place, Texas A&M and Essentium researchers added both these components to conventional 3D printers. When the researchers tested the strength of 3D printed parts using their new technology, they found that their strength was comparable to injection-molded parts.

The holy grail of 3D printing has been to get the strength of the 3D-printed part to match that of a molded part,” Green said. “In this study, we have successfully used localized heating to strengthen 3D-printed parts so that their mechanical properties now rival those of molded parts. With our technology, users can now print a custom part, like an individually tailored prosthetic, and this heat-treated part will be much stronger than before.”

The findings have been published in the  journal Nano Letters.

Source: https://today.tamu.edu/

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/

How To Recycle Greenhouse Gases into Fuel and Hydrogen

Scientists have taken a major step toward a circular carbon economy by developing a long-lasting, economical catalyst that recycles greenhouse gases into ingredients that can be used in fuel, hydrogen gas, and other chemicals. The results could be revolutionary in the effort to reverse global warming, according to the researchers. The study was published in Science.

Newly developed catalyst that recycles greenhouse gases into ingredients that can be used in fuel, hydrogen gas and other chemicals

We set out to develop an effective catalyst that can convert large amounts of the greenhouse gases carbon dioxide and methane without failure,” said Cafer T. Yavuz, paper author and associate professor of chemical and biomolecular engineering and of chemistry at KAIST (Korea).

The catalyst, made from inexpensive and abundant nickel, magnesium, and molybdenum, initiates and speeds up the rate of reaction that converts carbon dioxide and methane into hydrogen gas. It can work efficiently for more than a month.

This conversion is called ‘dry reforming’, where harmful gases, such as carbon dioxide, are processed to produce more useful chemicals that could be refined for use in fuel, plastics, or even pharmaceuticals. It is an effective process, but it previously required rare and expensive metals such as platinum and rhodium to induce a brief and inefficient chemical reaction.

Other researchers had previously proposed nickel as a more economical solution, but carbon byproducts would build up and the surface nanoparticles would bind together on the cheaper metal, fundamentally changing the composition and geometry of the catalyst and rendering it useless.

The difficulty arises from the lack of control on scores of active sites over the bulky catalysts surfaces because any refinement procedures attempted also change the nature of the catalyst itself,” Yavuz said.

The researchers produced nickel-molybdenum nanoparticles under a reductive environment in the presence of a single crystalline magnesium oxide. As the ingredients were heated under reactive gas, the nanoparticles moved on the pristine crystal surface seeking anchoring points. The resulting activated catalyst sealed its own high-energy active sites and permanently fixed the location of the nanoparticles — meaning that the nickel-based catalyst will not have a carbon build up, nor will the surface particles bind to one another.

It took us almost a year to understand the underlying mechanism,” said first author Youngdong Song, a graduate student in the Department of Chemical and Biomolecular Engineering at KAIST. “Once we studied all the chemical events in detail, we were shocked.”

The researchers dubbed the catalyst Nanocatalysts on Single Crystal Edges (NOSCE). The magnesium-oxide nanopowder comes from a finely structured form of magnesium oxide, where the molecules bind continuously to the edge. There are no breaks or defects in the surface, allowing for uniform and predictable reactions.

Our study solves a number of challenges the catalyst community faces,” Yavuz said. “We believe the NOSCE mechanism will improve other inefficient catalytic reactions and provide even further savings of greenhouse gas emissions.

Source: https://news.kaist.ac.kr/

Electric 3D-Printed Plastics

Rutgers engineers have embedded high performance electrical circuits inside 3D-printed plastics, which could lead to smaller and versatile drones and better-performing small satellites, biomedical implants and smart structures.

They used pulses of high-energy light to fuse tiny silver wires, resulting in circuits that conduct 10 times more electricity than the state of the art, according to a study in the journal Additive Manufacturing. By increasing conductivity 10-fold, the engineers can reduce energy use, extend the life of devices and increase their performance.

Our innovation shows considerable promise for developing an integrated unit – using 3D printing and intense pulses of light to fuse silver nanoparticles – for electronics,” said senior author Rajiv Malhotra, an assistant professor in the Department of Mechanical and Aerospace Engineering in the School of Engineering at Rutgers University–New Brunswick.

Embedding electrical interconnections inside 3D-printed structures made of polymers, or plastics, can create new paradigms for devices that are smaller and more energy-efficient. Such devices could include CubeSats (small satellites), drones, transmitters, light and motion sensors and Global Positioning Systems. Such interconnections are also often used in antennas, pressure sensors, electrical coils and electrical grids for electromagnetic shielding.

Source: https://news.rutgers.edu/

Plastic Waste Desintegrates Into Nanoparticles

There is a considerable risk that plastic waste in the environment releases nano-sized particles known as nanoplastics, according to a new study from Lund University in Sweden. The researchers studied what happened when takeaway coffee cup lids, for example, were subjected to mechanical breakdown, in an effort to mimic the degradation that happens to plastic in the ocean.The majority of all marine debris is plastic. Calculations have shown that ten per cent of all plastic produced globally ends up in the sea. This plastic waste is subjected to both chemical and mechanical degradation. The sun’s UV rays contribute to the degradation, as do waves, which cause plastic waste to grind against stones on the water’s edge, against the sea floor or against other debris.

Is there a risk that this plastic waste disintegrates to the extent that nanoplastics are released? The research community is divided on whether the degradation process stops at slightly larger plastic fragmentsmicroplastics – or actually continues and creates even smaller particles. The researchers behind the study have now investigated this issue by subjecting plastic material to mechanical degradation under experimental conditions.

We have been able to show that the mechanical effect on the plastic causes the disintegration of plastic down to nano-sized plastic fragments,” says Tommy Cedervall, chemistry researcher at Lund University.

The emphasis of a number of other recent studies from the research community has been on microplastics and their increased distribution among organisms. There are now intense attempts to also identify nanoplastics in the environment. Last year, in an earlier study from Lund University, researchers showed that nano-sized plastic particles can enter the brains of fish and that this causes brain damage which probably disturbs fish behaviour.

It’s important to begin mapping what happens to disintegrated plastic in nature, concludes Tommy Cedervall.

Source: https://www.lunduniversity.lu.se/

Spheres Trick, Trap and Terminate Water Contaminant

Rice University scientists have developed something akin to the Venus’ flytrap of particles for water remediationMicron-sized spheres created in the lab of Rice environmental engineer Pedro Alvarez are built to catch and destroy bisphenol A (BPA), a synthetic chemical used to make plasticsBPA is commonly used to coat the insides of food cans, bottle tops and water supply lines, and was once a component of baby bottles. While BPA that seeps into food and drink is considered safe in low doses, prolonged exposure is suspected of affecting the health of children and contributing to high blood pressure. The good news is that reactive oxygen species (ROS) – in this case, hydroxyl radicals – are bad news for BPA. Inexpensive titanium dioxide releases ROS when triggered by ultraviolet light. But because oxidating molecules fade quickly, BPA has to be close enough to attack. That’s where the trap comes in.

Close up, the spheres reveal themselves as flower-like collections of titanium dioxide petals. The supple petals provide plenty of surface area for the Rice researchers to anchor cyclodextrin molecules. Cyclodextrin is a benign sugar-based molecule often used in food and drugs. It has a two-faced structure, with a hydrophobic (water-avoiding) cavity and a hydrophilic (water-attracting) outer surface. BPA is also hydrophobic and naturally attracted to the cavity. Once trapped, ROS produced by the spheres degrades BPA into harmless chemicals.

In the lab, the researchers determined that 200 milligrams of the spheres per liter of contaminated water degraded 90 percent of BPA in an hour, a process that would take more than twice as long with unenhanced titanium dioxide. The work fits into technologies developed by the Rice-based and National Science Foundation-supported Center for Nanotechnology-Enabled Water Treatment because the spheres self-assemble from titanium dioxide nanosheets.

Petals” of a titanium dioxide sphere enhanced with cyclodextrin as seen under a scanning electron microscope. When triggered by ultraviolet light, the spheres created at Rice University are effective at removing bisphenol A contaminants from water.

Most of the processes reported in the literature involve nanoparticles,” said Rice graduate student and lead author Danning Zhang. “The size of the particles is less than 100 nanometers. Because of their very small size, they’re very difficult to recover from suspension in water.

The research is detailed in the American Chemical Society journal Environmental Science & Technology.

Source: http://news.rice.edu/

‘WasteShark’, The Aquadrone That Cleans The Ocean Waste

A swarm of autonomous robots that can swim across bodies of water to collect garbage might be the key to saving the oceans. A few years ago, RanMarine Technology, a company from the Netherlands, has introduced WasteShark, an aquadrone that works like a smart vacuum cleaner (essentially, a Roomba for the seas) to gather wastes that end up in waterways before they accumulate into a great big patch in the middle of the Pacific Ocean.

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The operational cost of the vehicle… will be almost nothing. You are basically using compressed air. You are not paying for fuel and also you do not need cooling,” said Mahmoud Yasser, a student who helped design it. The team is now looking to raise funding to expand the project and mass produce the vehicles. They believe they can eventually get the vehicles to top 100 kilometers an hour and run for 100 kilometers before needing to come up for air.

Every year, about 1.4 billion pounds of trash end up in the ocean. Plastics, styrofoam, and other nonbiodegradable materials get dumped into the waters, eaten by fishes and birds or collect into what has become the Great Pacific Garbage Patch — a gyre of debris between California and Hawaii bigger than AlaskaTrash in seas and oceans have become a huge problem, but the WasteShark might be able to help.

RanMarine said that its aquadrones are inspired by whale sharks, “nature’s most efficient harvesters of marine biomass.” The company claims that the vessels can collect up to 200 liters of waste before it needs to be emptied and swim across the water for 16 hours. The WasteShark are autonomous as it can intelligently wade through water and collect trash using sensors. It is equipped with a GPS to track its movements.

Source: https://www.techtimes.com/

Plastic-Eating Enzyme

Scientists have engineered an enzyme which can digest some of our most commonly polluting plastics, providing a potential solution to one of the world’s biggest environmental problems. The discovery could result in a recycling solution for millions of tonnes of plastic bottles, made of polyethylene terephthalate, or PET, which currently persists for hundreds of years in the environment. The research was led by teams at the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory (NREL) and is published in Proceedings of the National Academy of Sciences (PNAS).

 Professor John McGeehan at the University of Portsmouth and Dr Gregg Beckham at NREL solved the crystal structure of PETase—a recently discovered enzyme that digests PET— and used this 3D information to understand how it works. During this study, they inadvertently engineered an enzyme that is even better at degrading the plastic than the one that evolved in nature. The researchers are now working on improving the enzyme further to allow it to be used industrially to break down plastics in a fraction of the time.

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Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans, or washed up on once pristine beaches all over the world. “We can all play a significant part in dealing with the plastic problem, but the scientific community who ultimately created these ‘wonder-materials’, must now use all the technology at their disposal to develop real solutions,” said Professor McGeehan, Director of the Institute of Biological and Biomedical Sciences in the School of Biological Sciences at Portsmouth,

Source: http://uopnews.port.ac.uk/