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Aerogel: the micro structural material of the future

Behind the simple headline “Additive manufacturing of silica aerogels” — the article was published on July 20th in the scientific journal Nature — a groundbreaking development is hidden. Silica aerogels are light, porous foams that provide excellent thermal insulation. In practice, they are also known for their brittle behaviour, which is why they are usually reinforced with fibres or with organic or biopolymers for large-scale applications. Due to their brittle fracture behaviour, it is also not possible to saw or mill small pieces out of a larger aerogel block. Directly solidifying the gel in miniaturised moulds is also not reliably — which results in high scrap rates. This is why aerogels have hardly been usable for small-scale applications.

Stable, well-formed microstructures

The Empa team led by Shanyu Zhao, Gilberto Siqueira, Wim Malfait and Matthias Koebel have now succeeded in producing stable, well-shaped microstructures from silica aerogel by using a 3D printer. The printed structures can be as thin as a tenth of a millimeter. The thermal conductivity of the silica aerogel is just under 16 mW/(m*K) — only half that of polystyrene and even significantly less than that of a non-moving layer of air, 26 mW/(m*K). At the same time, the novel printed silica aerogel has even better mechanical properties and can even be drilled and milled. This opens up completely new possibilities for the post-processing of 3D printed aerogel mouldings.

With the method, for which a patent application has now been filed, it is possible to precisely adjust the flow and solidification properties of the silica ink from which the aerogel is later produced, so that both self-supporting structures and wafer-thin membranes can be printed. As an example of overhanging structures, the researchers printed leaves and blossoms of a lotus flower. The test object floats on the water surface due to the hydrophobic properties and low density of the silica aerogel — just like its natural model. The new technology also makes it possible for the first time to print complex 3D multi-material microstructures.

Insulation materials for microtechnology and medicine

With such structures it is now comparatively trivial to thermally insulate even the smallest electronic components from each other. The researchers were able to demonstrate the thermal shielding of a temperature-sensitive component and the thermal management of a local “hot spot” in an impressive way. Another possible application is the shielding of heat sources inside medical implants, which should not exceed a surface temperature of 37 degrees in order to protect body tissue.

A functional aerogel membrane

3D printing allows multilayer/multi-material combinations to be produced much more reliably and reproducibly. Novel aerogel fine structures become feasible and open up new technical solutions, as a second application example shows: Using a printed aerogel membrane, the researchers constructed a “thermos-molecular” gas pump. This permeation pump manages without any moving parts at all and is also known to the technical community as a Knudsen pump, named after the Danish physicist Martin Knudsen. The principle of operation is based on the restricted gas transport in a network of nanoscale pores or one-dimensional channels of which the walls are hot at one end and cold at the other. The team built such a pump from aerogel, which was doped on one side with black manganese oxide nanoparticles. When this pump is placed under a light source, it becomes warm on the dark side and starts to pump gases or solvent vapours.

Air purification without moving parts

These applications show the possibilities of 3D printing in an impressive way: 3D printing turns the high-performance material aerogel into a construction material for functional membranes that can be quickly modified to suit a wide range of applications. The Knudsen pump, which is driven solely by sunlight, can do more than just pump: If the air is contaminated with a pollutant or an environmental toxin such as the solvent toluene, the air can circulate through the membrane several times and the pollutant is chemically broken down by a reaction catalyzed by the manganese oxide nanoparticles. Such sun-powered, autocatalytic solutions are particularly appealing in the field of air analysis and purification on a very small scale because of their simplicity and durability.

Empa researchers are now looking for industrial partners who want to integrate 3D-printed aerogel structures into new high-tech applications.

Video: https://www.youtube.com/watch?v=Yl8yz28xQbw&feature=emb_logo

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Materials provided by Swiss Federal Laboratories for Materials Science and Technology (EMPA). Original written by Rainer Klose. Note: Content may be edited for style and length.

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Promising new research identifies novel approach for controlling defects in 3D printing

With its ability to yield parts with complex shapes and minimal waste, additive manufacturing has the potential to revolutionize the production of metallic components. That potential, however, is currently limited by one critical challenge: controlling defects in the process that can compromise the performance of 3D-printed materials.

A new paper in the journal Additive Manufacturing points to a possible breakthrough solution: Use temperature data at the time of production to predict the formation of subsurface defects so they can be addressed right then and there. A team of researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, together with a colleague now at Texas A&M University, discovered the possibility.

“Ultimately you would be able to print something and collect temperature data at the source and you could see if there were some abnormalities, and then fix them or start over,” said Aaron Greco, group manager for Argonne’s Interfacial Mechanics & Materials group in the Applied Materials Division (AMD) and a study author. “That’s the big-picture goal.”

For their research, the scientists used the extremely bright, high-powered X-rays at beamline 32-ID-B at Argonne’s Advanced Photon Source (APS), a Department of Energy Office of Science User Facility. They designed an experimental rig that allowed them to capture temperature data from a standard infrared camera viewing the printing process from above while they simultaneously used an X-ray beam taking a side-view to identify if porosity was forming below the surface.

Porosity refers to tiny, often microscopic “voids” that can occur during the laser printing process and that make a component prone to cracking and other failures.

According to Noah Paulson, a computational materials scientist in the Applied Materials division and lead author on the paper, this work showed that there is in fact a correlation between surface temperature and porosity formation below.

“Having the top and side views at the same time is really powerful. With the side view, which is what is truly unique here with the APS setup, we could see that under certain processing conditions based on different time and temperature combinations porosity forms as the laser passes over,” Paulson said.

For example, the paper observed that thermal histories where the peak temperature is low and followed by a steady decline are likely to be correlated with low porosity. In contrast, thermal histories that start high, dip, and then later increase are more likely to indicate large porosity.

The scientists used machine learning algorithms to make sense out of the complex data and predict the formation of porosity from the thermal history. Paulson said that in comparison to the tools developed by tech giants that use millions of data points, this effort had to make do with a couple hundred. “This required that we develop a custom approach that made the best use of limited data,” he said.

While 3D printers typically come equipped with infrared cameras, the cost and complexity make it impossible to equip a commercial machine with the kind of X-ray technology that exists at the APS, which is one of the most powerful X-ray light sources in the world. But by designing a methodology to observe systems that already exist in 3D printers, that wouldn’t be necessary.

“By correlating the results from the APS with the less detailed results we can already get in actual printers using infrared technology, we can make claims about the quality of the printing without having to actually see below the surface,” explained co-author Ben Gould, a materials scientist in the AMD.

The ability to identify and correct defects at the time of printing would have important ramifications for the entire additive manufacturing industry because it would eliminate the need for costly and time-consuming inspections of each mass-produced component. In traditional manufacturing, the consistency of the process makes it unnecessary to scan every metallic component coming off of the production line.

“Right now, there’s a risk associated with 3D printing errors, so that means there’s a cost. That cost is inhibiting the widespread adoption of this technology,” Greco said. “To realize its full potential, we need to lower the risk to lower the cost.”

This effort is made all the more urgent in recognizing one of the key advantages that additive manufacturing has over traditional manufacturing. “We saw with the recent pandemic response how valuable it would be to be able to quickly adapt production to new designs and needs. 3D technology is very adaptable to those kinds of changes,” added Greco.

Looking ahead, Gould said the research team was hopeful that what he called a “very, very good first step” would allow it to keep improving and expanding the model. “For machine learning, to build accurate models you need thousands and thousands of data points. For this experiment, we had 200. As we put in more data, the model will get more and more exact. But what we did find is very promising.”

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Additive Flight Solutions gains AS9100D certification for its 3D printed aerospace parts 

Additive Flight Solutions (AFS), a joint venture between 3D printer manufacturer Stratasys and Singaporian aircraft specialist SIA Engineering Company (SIAEC), has received AS9100D Certification.  Combining Stratasys’ additive manufacturing knowledge with SIAEC’s expertise in spare parts, AFS has gained international accreditation for its 3D printed aerospace parts. The certification is a standardized quality management and assurance […]

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Author: Paul Hanaphy

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Laser inversion enables multi-materials 3D printing

Additive manufacturing — or 3D printing — uses digital manufacturing processes to fabricate components that are light, strong, and require no special tooling to produce. Over the past decade, the field has experienced staggering growth, at a rate of more than 20% per year, printing pieces that range from aircraft components and car parts to medical and dental implants out of metals and engineering polymers. One of the most widely used manufacturing processes, selective laser sintering (SLS), prints parts out of micron-scale material powders using a laser: the laser heats the particles to the point where they fuse together to form a solid mass.

“Additive manufacturing is key to economic resilience,” say Hod Lipson, James and Sally Scapa Professor of Innovation (Mechanical Engineering). “All of us care about this technology — it’s going to save us. But there’s a catch.”

The catch is that SLS technologies have been limited to printing with a single material at a time: the entire part has to be made of just that one powder. “Now, let me ask you,” Lipson continues, “how many products are made of just one material? The limitations of printing in only one material has been haunting the industry and blocking its expansion, preventing it from reaching its full potential.”

Wondering how to solve this challenge, Lipson and his PhD student John Whitehead used their expertise in robotics to develop a new approach to overcome these SLS limitations. By inverting the laser so that it points upwards, they invented a way to enable SLS to use — at the same time — multiple materials. Their working prototype, along with a print sample that contained two different materials in the same layer, was recently published online by Additive Manufacturing as part of its December 2020 issue.

“Our initial results are exciting,” says Whitehead, the study’s lead author, “because they hint at a future where any part can be fabricated at the press of a button, where objects ranging from simple tools to more complex systems like robots can be removed from a printer fully formed, without the need for assembly.”

Selective laser sintering traditionally has involved fusing together material particles using a laser pointing downward into a heated print bed. A solid object is built from the bottom up, with the printer placing down a uniform layer of powder and using the laser to selectively fuse some material in the layer. The printer then deposits a second layer of powder onto the first layer, the laser fuses new material to the material in the previous layer, and the process is repeated over and over until the part is completed.

This process works well if there is just one material used in the printing process. But using multiple materials in a single print has been very challenging, because once the powder layer is deposited onto the bed, it cannot be unplaced, or replaced with a different powder.

“Also,” adds Whitehead, “in a standard printer, because each of the successive layers placed down are homogeneous, the unfused material obscures your view of the object being printed, until you remove the finished part at the end of the cycle. Think about excavation and how you can’t be sure the fossil is intact until you completely remove it from the surrounding dirt. This means that a print failure won’t necessarily be found until the print is completed, wasting time and money.”

The researchers decided to find a way to eliminate the need for a powder bed entirely. They set up multiple transparent glass plates, each coated with a thin layer of a different plastic powder. They lowered a print platform onto the upper surface of one of the powders, and directed a laser beam up from below the plate and through the plate’s bottom. This process selectively sinters some powder onto the print platform in a pre-programmed pattern according to a virtual blueprint. The platform is then raised with the fused material, and moved to another plate, coated with a different powder, where the process is repeated. This allows multiple materials to either be incorporated into a single layer, or stacked. Meanwhile, the old, used-up plate is replenished.

In the paper, the team demonstrated their working prototype by generating a 50 layer thick, 2.18mm sample out of thermoplastic polyurethane (TPU) powder with an average layer height of 43.6 microns and a multi-material nylon and TPU print with an average layer height of 71 microns. These parts demonstrated both the feasibility of the process and the capability to make stronger, denser materials by pressing the plate hard against the hanging part while sintering.

“This technology has the potential to print embedded circuits, electromechanical components, and even robot components. It could make machine parts with graded alloys, whose material composition changes gradually from end to end, such as a turbine blade with one material used for the core and different material used for the surface coatings,” Lipson notes. “We think this will expand laser sintering towards a wider variety of industries by enabling the fabrication of complex multi-material parts without assembly. In other words, this could be key to moving the additive manufacturing industry from printing only passive uniform parts, towards printing active integrated systems.”

The researchers are now experimenting with metallic powders and resins in order to directly generate parts with a wider range of mechanical, electrical, and chemical properties than is possible with conventional SLS systems today.

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PostProcess Technologies’ 2020 Post-Printing Trends Survey is now live

PostProcess Technologies has just launched the 2020 iteration of its annual Additive Manufacturing Post-Printing Industry Trends Survey. After a successful debut in 2019, the post-printing (aka post-processing) specialist is again looking to share insights into the 3D printing industry’s most common post-printing methods, most frequently faced challenges, and growth plans. This year’s survey is packed […]

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Author: Kubi Sertoglu

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Raytheon awarded $841K to advance 3D printed military optics

America Makes, an additive manufacturing innovation organization managed by the U.S. Department of Defense, has announced aerospace firm Raytheon Technologies as the awardee of its Additive for eXtreme Improvement in Optical Mounts (AXIOM) Project Call. For its submission titled ‘Topology Optimized Reflective Optics’, the Raytheon team will receive a total of $841K in funding. The […]

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Author: Kubi Sertoglu

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New 3D printing jobs at MyMiniFactory, RMT and Link3D, new appointments at Physna, Fehrmann and more

Welcome to the latest edition of our 3D printing jobs and career moves update for the additive manufacturing sector. If you are looking for a new position in the industry, we keep our 3D Printing job board updated with the latest positions. You can easily apply to any of the posted jobs after creating a […]

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Author: Paul Hanaphy

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Decathlon boosts supply chain with Figure 4 3D printing

Global sporting goods leader Decathlon has integrated 3D Systems’ Figure 4 additive manufacturing technology into its supply chain. The French retailer claims the resin-based technology has streamlined functional part development and shrunk production cycles, while providing a “major competitive edge in terms of speed, precision, and versatility”. Savings at the additive manufacturing lab The line […]

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New 3D printing jobs at ScheMatter, appointments at AMT, Titomic, Dyndrite, BEAMIT and more

Welcome to the latest edition of our 3D printing jobs and career moves update for the additive manufacturing sector. If you are looking for a new position in the industry, we keep our 3D Printing job board updated with the latest positions. You can easily apply to any of the posted jobs after creating a […]

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AREVO and Superstrata reveal custom 3D printed unibody carbon fiber e-Bikes 

AREVO, a Silicon Valley company dedicated to direct digital additive manufacturing of composite materials, has worked with new California-based start-up Superstrata to 3D print the fully-unified carbon composite frames for its upcoming e-bikes.  By producing the frame in a single piece using AREVO’s continuous carbon fibre 3D printing technology, Superstrata has eliminated the need for […]

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Author: Paul Hanaphy