University of Auckland: Growth-Induced Bending of 3D Printed Samples Based on PET-RAFT Polymerization

4D printed objects are 3D printed objects made with smart materials that respond to environmental stimuli, like liquid and heat, or return to an original form after deformation. Researchers from the University of Auckland published a paper regarding 3D printing and growth-induced bending based on photo electron/energy transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization.

By adding reversible deactivation radical polymerization (RDRP) constituents to a 3D printed structure to create “living” materials, which keep polymerizing on-demand, allows structures to be built with post-production functionality and modularity. But, as the Auckland team states, “this forms only half of the solution.”

RAFT processes have been used as a controlled polymerization technique to help with self-assembling macromolecules and block copolymerization. They previously demonstrated photo-RAFT polymerization 3D printing under several visible wavelengths, showing that a facile surface modification “could be performed on the samples after printing with a range of different monomers.”

Graphical abstract

“For this work, we further optimized the PET-RAFT 3D printing formulation and demonstrated the 3D printability using a commercial DLP 3D printer with standard 405nm light sources,” they wrote. “We also explore the 4D post-production modification capabilities of the 3D printed object using green light (λmax = 532 nm).”

The PET-RAFT recipe they used, below, adds a tertiary amine and the photo redox catalyst EY, the latter of which “is raised to an excited state (EY*) under irradiation where it then has several pathways to release its energy.” This is useful for 3D printing, since it’s a desirable “oxygen tolerant pathway.”

(A) Chemical structures of Eosin Y (EY), 2-(butylthiocarbonothioylthio) propanoic acid (BTPA), poly (ethylene glycol) diacrylate (PEGDA, average Mn = 250 g/mol), N, N-dimethylacrylamide (DMAm), and triethanolamine (TEtOHA). (B) Proposed combined PET-RAFT mechanism showing tertiary amine pathway by Qiao, Boyer, and Nomeir15, 23-25 (C) Reaction scheme for PET-RAFT polymerization of our 3D printing resin. (D) Schematic of a standard DLP 3D printer.

In their previous research, they used a 3D printing resin that was much slower to polymerize, and produced brittle objects. This time, they made several changes to the resin, such as replacing the RAFT agent CDTPA with BTPA and adjusting monomer composition.

“The development of an optimized 3D printing resin formula for use in a commercial DLP printer (λmax = 405nm, 101.86µW/cm2) was the first step in this research. Thus, several criteria were used to determine the quality of the optimized resin; the optimized resin must be able to hold its form in 60 seconds or less exposure time, the printed objects must have a good layer to layer resolution and binding, must be an accurate representation of the CAD model, and the resin must be stable enough to be reusable for consecutive runs,” the team explained.

They kept these criteria in mind while creating and testing new resin recipes with Photo Differential Scanning Calorimetry (Photo-DSC) and a 400-500 nm light source range.

“A monomer to RAFT agent ratio of 500:1 was chosen as a balance between a faster build speed, and a high enough RAFT concentration to perform post-production modifications,” they said. “For the first step in optimization we decided to compare two asymmetric RAFT agents, CDTPA and BTPA.”

Photo-DSC plot showing resin composition of [BTPA]: [PEGDA]: [EY]: [TEtOHA] = 1:500:0.01:20 (blue), [BTPA]: [PEGDA]: [DMAm]: [EY]: [TEtOHA] = 1:350:150:0.01:20 (green), [BTPA]: [PEGDA]: [DMAm]: [EY]: [TEtOHA] = 1:150:350:0.01:20 (red), [CDTPA]: [PEGDA]: [EY]: [TEOHA] = 1:500:0.01:20 (black), and [CDTPA]:[PEGDA]:[EY]:[TEA] = 1:200:0.01:2 (orange) form our previous PET-RAFT work, were compared to find an optimum new resin formula. The effects of different RAFT agent and comonomer ratio are noticeable on the maximum heat flow and the peak position of tmax.

The first formula, [BTPA]: [PEGDA]: [EY]: [TEtOHA] = 1:500:0.01:20, had a limited inhibition period, while [CDTPA]: [PEGDA]: [EY]: [TEtOHA] = 1:500:0.01:20 had a longer one.

“These results help to demonstrate the increase in polymerization rate that can be achieved by using BTPA in place of CDTPA,” they noted.

Because of its high glass transition temperature, DMAm was added as a comonomer in [PEGDA]: [DMAm] = 70:30 and 30:70 ratios. This slowed the polymerization rate for the resin formulas [BTPA]: [PEGDA]: [DMAm]: [EY]: [TEtOHA] = 1:350:150:0.01:20 and [BTPA]: [PEGDA]: [DMAm]: [EY]: [TEtOHA] = 1:150:350:0.01:20, but it was still faster than the CDTPA formulation. The researchers used this formulation to 3D print samples for dynamic mechanical analysis (DMA) and 4D post-production modification.

UV-Vis absorption spectra; (A) EB under 405nm (397.45µW/cm2) exposure for; initial (black), 10 (red), 20 (blue), 30 (magenta) and 40 minutes (olive). (B) EY under 405nm exposure for; initial, 10, 20, 30 and 40 minutes.

It’s important that photocatalysts don’t have issues like photobleaching or photodegradation during a photocatalytic process. Above, you can see a comparison in absorbance loss between organic photocatalysts EY and Erythrosin B (EB), “using their absorbance curves after different periods of 405 nm light irradiation.”

“Both showed a noticeable gradual decrease in UV absorbance which could likely be due to irreversible photodegradation, given that the effect remains after the sample has been stored overnight in a dark environment and measured again,” the team explained.

After longer periods of time, the EB solution started changing color, but this didn’t happen with the EY formulation, which is why the team kept it in their 3D-RAFT resin composition. A photostable catalyst, like EY, makes it possible for the 3D printing process to continue undisturbed.

The 3D printed samples that underwent DMA analysis were:

  • optimized RAFT resin before and after post-production modification
  • non-3D printed DMA sample by PET-RAFT polymerization in bulk
  • 3D printed free radical polymerization (FRP) control sample

The first type were 3D printed with a 30 µm thickness, a 60 second attachment time, and 30 seconds of exposure per each of the 53 layers. The second was fabricated with the same optimized formula “but polymerized in bulk using an external mold and a conventional 405nm lamp external,” while the FRP samples were printed with the same monomer composition and parameters but used a “conventional photoinitiator, phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO).”

DMA plot showing (black) storage modulus (E’) and (black dashed) Tan δ from 3D printed DMA sample by normal FRP of resin formula [PEGDA]: [DMAm]: [TPO] = 350:150 and 2wt% TPO; (blue) the E’ and (blue dashed) Tan δ from 3D-RAFT printed DMA sample using resin formula [BTPA] :[PEGDA]: [DMAm]: [EY]: [TEtOHA] = 1:350:150:0.01:20; (green) the E’ and (green dashed) Tan δ from the post-print modified DMA sample; lastly (red) the E’ and (red dashed) Tan δ from the non-3D printed DMA sample prepared by normal PET-RAFT polymerization in bulk.

A temperature ramp (2˚C/min) was performed in order to find the storage modulus (E’) and glass transition temperature (Tg) of the samples, and there was a major change “in the E’ to 80 MPa and Tg to 15˚C” when the samples were compared to ones that weren’t 3D printed but instead polymerized in a mold.

“This layer-by-layer construction appeared to play a major role in the E’ at room temperature of the overall sample,” the team noted. “Each layer in the 3D printed sample received equal light irradiation (apart from attachment layer where specified), whereas in the bulk samples light had to penetrate through the entire thickness of the resin.”

Samples printed with RAFT resin had methyl methacrylate (MMA) monomer inserted post-production “in a growth medium devoid of solvent,” and DMA was used to analyze the effect of this modification on the prints’ mechanical properties, as well as “the relative effect on E’ and Tg of the sample.”

“The E’ at room temperature of the sample had decreased to 100 MPa but the Tg remained constant at about 19˚C,” they explained. “These limited changes can largely be attributed to the fact that BTPA is an asymmetric RAFT agent, all the growth being surface focused thus limiting the mechanical effects on the 3D printed RAFT sample.”

A1) CAD model for shapes upon 3 × 3 cm base. A2) Corresponding 3D-RAFT objects printed using DLP 3D printer. B1) Kiwi bird CAD model upon tiered base. B2) Corresponding 3D-RAFT printed object.

Once they determined the optimal RAFT 3D printing resin, the researchers designed CAD models for the objects they would print. They arranged different shapes, like triangles and Kiwi birds, on top of square and hexagonal base plates and circular coins, in order to see how the PET-RAFT resin formulation could handle features like corners and curves.

“These objects generally represented an accurate 3D print of the corresponding CAD model, confirming that the current 3D-RAFT resin was capable of printing 3D objects using a 405nm DLP 3D printer (λmax = 405 nm, 101.86µW/cm2),” they noted.

“Objects printed with 3D-RAFT also displayed an actual build speed of 2286 µm/hr (calculated from the actual height of printed objects over the full print time) consistent with that of the theoretical build speed, which is significantly faster than our previous PET-RAFT resin formula…”

Only limited shrinkage occurred on these prints, and after being washed for two days each in ethanol, THF, and DMSO, the team did not note a visible loss in yellow “arising from the trithiocarbonate group of the RAFT agent.” The 3D-RAFT resin was also reusable over more than ten prints.

“Having demonstrated that we could reliably print objects using our new RAFT resin, we endeavoured to demonstrate that these objects had retained their desired “living” behavior and could undergo post-production modification,” the team wrote.

They immersed half of a 3D-RAFT printed strip in a growth medium containing [BA]: [EY]: [TEtOHA] = 500:0.01:20 in DMSO. Then, a green 532 nm LED light was directed onto one of its faces, and after 15 minutes, “the strip showed moderate curvature.” They could see the strip was bending considerably after 15 more minutes, and it was also much softer, with the irradiated face paler than the other, and the growth medium was cloudier.

Optical images and graphical representations of growth-induced bending process. (A) The initial 3D-RAFT printed strip. (B) 3D-RAFT strip after 15 minutes monodirectional green light irradiation (532nm, 58.72µW/cm2) in a growth medium of DMSO and BA. (C) The same strip after 30 minutes monodirectional green light irradiation in the same growth medium. (D) Reaction scheme for the photo-catalyzed insertion of BA monomer under green light irradiation.

They next performed some control experiments. First, they tried the same thing with an FRP printed strip and a [PEGDA]: [DMAm] = 350:150 and 2wt% TPO growth medium, but this did not bend. A 3D-RAFT printed strip was left to soak in the original growth medium, without any light irradiation, for 24 hours, “to ensure that the bending was coming from growth rather than an alternate stimulus such as solvent swelling,” and saw no changes. Finally, they tried the same original process to return the bent 3D-RAFT strip back to its original form by shining the green light at it from the opposite direction. While it ultimately worked, it took three hours of irradiation to bend the strip back, which “indicates the unfavorability of introducing stress on the opposing side of the strip by our current methods.”

“To the best of our knowledge, this is the first demonstration of the growth of new material into the surface of an existing 3D printed object using RAFT polymerization to induce a bending response,” they concluded.

“In summary, we have further developed a 3D printable RAFT resin formula with an improved build speed up to 2286 µm/hr and demonstrated its ability to undergo 4D post-production transformation. We first demonstrated a facile method for growth induced bending of 3D-RAFT printed strips which opens an alternative pathway for movement and modification of these printed objects.”

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Recycling Plastics in Fabrication & Design: 3D Printing Raw Materials from Plastic Waste

Alaeddine Oussai, Zoltán Bártfai, László Kátai, and István Szalkai explore ways to improve recycling in 3D printing, releasing the details of their recent study in ‘Development of 3D Printing Raw Materials from Plastic Waste.’

Using plastic and dealing with the trash it produces has become normal around the world—leaving many to look back on the years when we enjoyed products in reusable glass containers—like milk, for example. The authors point out that while plastic waste, regarding type and quality, varies around the world, many types are suitable for re-use. For 3D printing, however, recycling processes are still being heavily explored:

“The current applications for using recycled plastics in fabrication and design are fairly limited, on a small scale, plastics (such as ABS, HDPE, or PET) are shredded and formed into pellets, and then either extruded into lament to be used in existing 3D printers, or injection molded into small parts and pieces of larger components.”

“At a large scale, recycled HDPE is melted into sheets and either used directly as sheets in construction, or then heat formed from a sheet into components for construction. These methods of fabrication using recycled plastics are the norm because of their affordability and straightforward processes, yet each method leaves some complexity to be desired.”

For this study, the researchers focused on both polyethylene terephthalate (PET), often referred to as polyester, and polylactic acid (PLA). While it is true that recycling can be both complicated and confusing for consumers everywhere, there are four basic exercises associated with the process:

  • Mechanical reprocessing into equivalent products
  • Secondary processing into products with ‘lower properties’
  • Chemical constituent recovery
  • Quaternary energy recovery

PET recycling circle

Known as a #1 recycling plastic, PET is made of monomer ethylene terephthalate. This is a material often used to make plastic bottles, as well as thin films and solar cells, offering high mechanical strength and temperature resistance.

End markets for PET recirculates in Europe and in the USA (Petcore, 2011; Napcor, 2011).

PLA is one of the most common types of 3D printing filament, known for its plant-based nature and resulting biodegradability. And while its true nature in terms of degrading are still being explored, this material is used widely by users and researchers too, featured in studies exploring the potential for a more circular economy, development of biodegradable blends, direct waste printing with pellets, and much more.

“Although PLA is a biodegradable material, which would significantly reduce environmental pollution associated with its waste, the knowledge behind this material recycling and changes in the properties of PLA upon its multiple processing is a very important subject of discussion,” state the authors.

Other materials like polyvinyl chloride (PVC) can break down in only several days. PVC is also affordable and offers the potential for making high-performance parts. Polyethylene’s PE’s are also commonly used, offering density, toughness, and flexibility.

Today, overall recycling efforts, and within 3D printing also, are geared toward less use of energy, less sorting during the process, and the eventual inclusion of what are now non-recyclables. Currently only poly (ethylene terephthalate) (PET) and polyethylene (as 9 and 37% of the annual plastic produced) are being mechanically processed.

The researchers mention a previous research solution as they developed a ‘crusher,’ for re-using plastic. The device consists of a crusher and extruder, along with 12 blades.

overview of the complete design of the crusher

Overview of the complete design of the extruder

Other recycling methods include chemical technology; however, the researchers point out that right it is considered to be too expensive due to the amount of energy it consumes. They point out that incineration is an option too.

“In the current scenario there is growing demand and interest towards chemical recycling methods with low energy demand along with compatibility of mixed plastic waste to overcome the need for sorting and expanding the recycling technologies to traditional non-recyclable polymers,” concluded the researchers.

What do you think of this news? Let us know your thoughts; join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Development of 3D Printing Raw Materials from Plastic Waste’]

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Aalto University Develops a Novel Bioink for Cardiac Tissue Applications

Finland is one of Europe’s most forested nations. Over 70 percent of the country’s boreal forest is covered with spruce, pine, downy birch, and silver birch. But beyond the splendor of the Finnish woodlands, all these trees have one thing in common, and that is nanocellulose. A light solid substance obtained from plant matter which comprises cellulose nanofibrils (CNF) and is considered a pseudo-plastic that possesses the property of specific kinds of gels that are generally thick in normal conditions. Overall, it is a very environmentally friendly and non-toxic substance that is compatible with the human body and has the potential to be used for a range of medical applications.

In 2018, the Department of Bioproducts and Biosystems at Aalto University, located just outside Helsinki, began searching for new ideas to revitalize one of the country’s traditional economic engines, forests (which are handled sustainably thanks to renewable forest resources). At the time, they noticed that one of the possible applications could be working with nanocellulose. Forward two years and the researchers have come up with a new bioink formulation praising nanocellulose at its basis.

Thanks to the structural similarity to extracellular matrices and excellent biocompatibility of supporting crucial cellular activities, nanocellulose-based bioprinting has clearly emerged for its potential in tissue engineering and regenerative medicine. The qualities of the generally thick and fluid light substance make it an excellent match to develop bioinks that are both suitable and scalable in their production, but also have consistent properties. However, there have been major challenges in processing nanocellulose.

As described by Aalto University researchers in a recently published paper in the science journal ACS Publication, the unresolved challenges of bioink formulations based on nanocelluloses are what stops the substance from becoming one of the preferred components for 3D bioprinting structures. This is why Finnish researchers focused on developing a single-component bioink that could be used to create scaffolds with potential applications in cardiac biomedical devices, while fundamentally dealing with some of the limitations of using nanocellulose-based bioinks.

A co-author of the paper and a doctoral candidate at Aalto’s Department of Bioproducts and Biosystems, Rubina Ajdary, told 3DPrint.com that “other than natural abundance and as a renewable resource, nanocellulose has demonstrated to have an outstanding performance in tissue engineering.” She also suggested that “recent efforts usually consider the use of nanocellulose in combination with other biopolymers, for example, in multicomponent ink formulations or to encapsulate nanoparticles. But we were interested in investigating the potential of monocomponent nanocellulose 3D printed scaffolds that did not require crosslinking to develop the strength or solidity.”

In fact, the Biobased Colloids and Materials (BiCMat) research group at Aalto University, led by Orlando Rojas, proposed heterogeneous acetylation of wood fibers to ease their deconstruction into acetylated nanocellulose (AceCNF). As a unique biomaterial opportunity in 3D scaffold applications, the team considered using nanocelluloses due to the natural, easy to sterilize, and high stability porosity of the substance, and chose to introduce AceCNF for the generation of 3D printed scaffolds for implantation in the human body. The team then went on to evaluate the interactions of the scaffolds with cardiac myoblast cells.
“Most modifications make the hydrogels susceptible to dimensional instability after 3D printing, for instance, upon drying or wetting. This is exacerbated if the inks are highly diluted, which is typical of nanocellulose suspensions, forming gels at low concentrations,” went on Ajdary. “This instability is one of the main reasons why nanocellulose is mainly combined with other compounds. Instead, in this research, we propose heterogeneous acetylation of wood fibers to ease their deconstruction into acetylated nanocellulose for direct ink writing. A higher surface charge of acetylated nanocellulose, compared to native nanocellulose, reduces aggregation and favors the retention of the structure after extrusion even in significantly less concentration.”
This is exactly why it was important for the researches to develop a single component bioink. Nanocellulose has shown promises when combined with other biopolymers and particles. However, Ajdary insists that benefits including similarity to the extracellular matrix, high porosity, high swelling capacity, ease of surface modification, and shear thinning behavior of cellulose, encouraged them to study the potential of monocomponent surface-modified nanocelluloses.

Acetylated nanocellulose (Credit: Aalto University School of Chemical Engineering)

The team at Aalto University used the sustainable and widely available nanocelluloses to make several formulations of bioinks and evaluate them, including unmodified nanocellulose CNF, Acetylated CNF (AceCNF), and TEMPO-oxidized CNF.
To 3D bioprint the hydrogels, researchers used Cellink bioprinters, something Ajdary attributed to the user-friendliness of the device and because it provided a lot of flexibility to test different types of hydrogels and emulsions produced in the research group.
In this new process, the single-component nanocellulose inks were first 3D printed into scaffolds using Cellink’s BIO X bioprinter, which is equipped with a pneumatic print head was used to extrude single filaments and form the 3D structures. Then freeze-dried to avoid extensive shrinkage, and sterilized under UV light. After sterilization the scaffold was ready and cells seeded on the samples.
“3D structures of acetylated nanocellulose are highly stable after extrusion in far less concentrations. The lower concentration in wet condition facilitates the scaffold with higher porosity after dehydration which can improve the cell penetration in the structure and assist in nutrient transport to the cells as well as in the transport of metabolic waste,” specified Ajdary.
The researchers claim that the method was successful as the 3D printed scaffolds were compatible with the cardiomyoblast cells, enabling their proliferation and attachment, and revealing that the constructs are not toxic. Although still in research stages, these bioinks and technique can be used for the inexpensive, consistent fabrication and storage of constructs that can be applied as base materials for cardiac regeneration.
What is novel in this study is the particular focus on single-component nanocellulose-based bioinks that open up a possibility for the reliable and scale-up fabrication of scaffolds appropriate for studies on cellular processes and for tissue engineering. Since this is an ongoing research, we can expect to read more published material from Aalto University researchers as they continue testing their unique technique even further.

Scaffolds corresponding to 3D printed AceCNF (Credit: Aalto University)

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3D Printing with Bioplastics: Engineering Biodegradable PHA Blends

Jackie Anderson offers a review regarding one of the most critical 3D printing topics today: materials. As innovation continues to grow, so do the options regarding software, hardware, and different types of plastics (along with many other alternatives today).

In ‘Engineering Biodegradable PHA Blends,’ Anderson explores issues with plastic waste, and the need to use more environmentally friendly materials as 3D printing filaments.

While other plastics such as acrylonitrile butadiene styrene (ABS) are often used in 3D printing, bioplastics like polylactic acid (PLA) are popular due to their ability to biodegrade, but still, there are other materials superior in that area; in fact, previous research has shown that thin films of other bioplastics like polyhydroxyalkanoates (PHA) may degrade in as little as 1.2 to 2.4 months. This is promising in eliminating the amount of waste that could emerge from 3D printing discards, with Anderson reminding us that plastics can take ‘hundreds to thousands of years to degrade,’ causing harm to every living creature.

“Plastic is a toxic pollutant that causes damage on a wide scale to many different species and environments, and it is necessary that solutions are found to reduce this impact,” states Anderson.

Bioplastics are used in so many different projects today, from marine applications to medical implants to manufacturing. Produced from vegetables, food by-products, or micro-organisms, bioplastics are preferable to oil-based printing materials, environmentally. They are also conventionally used in making items like packaging, cutlery, straws, and even fishing net.

In using man-made plastics like PLA, biodegradability is a bonus, but printed parts can take years to break down:

“This makes it an undesirable material for products that require high rates of biodegradation,” states Anderson.

PHA is not as well-known overall, and especially not with novice users. This material biodegrades faster but is more expensive, not as accessible for consumers, and Anderson points out that it is often challenging to use on a larger scale. PHA also presents drawbacks in comparison to other bioplastics, offering less strength, less flexibility, and inferior melting properties. It can, however, be beneficial when added to other materials like PLA.

“There are other similar PHA blends that have been designed for similar purposes and have also shown great potential for commercial use, yet more research needs to be done on different PHA blends to expand this potential,” states Anderson.

Algae-based biopolymers, while still considered more of a novel material, are like PHA as they are produced naturally and biodegrade easily. Along with 3D printing materials, algae plastics are also used to make films, cutlery, and plastic bags.

“Algae plastic is just one of the many new bioplastics being developed and researched to help reduce plastic pollution. These products are beginning to be marketed more frequently and will help minimize plastic pollution if used on large scales to replace oil-based plastics,” explains Anderson.

Still, PLA is a favorite within the 3D printing industry, due to accessibility, affordability, efficiency in production, and some semblance of biodegradability:

“If PLA materials were to be discarded into landfills or abandoned in the environment, they would take several years to degrade, causing pollution like that of regular plastics,” states Anderson.

“This is deceiving because companies claim that PLA can degrade in about 40-90 days, but this is not the case if the materials are not in a controlled lab setting (PLA, 2019). PLA can only degrade efficiently in specific industrial composting conditions with temperatures at or above 55-70 degrees.”

Using PHA and PLA to create a composite for greater strength and biodegradability could be a good solution, allowing users the best of both worlds.

“While these bioplastics each have their own negative qualities, they can be blended together in different ratios to form a desirable new plastic with the beneficial qualities of each of them,” concluded Anderson.

“These new blends could be used for a wide range of applications, from food packaging to 3D printing filaments. Bioplastics cannot solve the plastic waste crisis altogether, but they can limit the future pollution caused by plastic use and help reduce the damage that humans have caused.”

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

An example of a PLA/PHA filament (colorFabb’s Sky Blue PLA/PHA), from ‘Climate Disrupted: The Promise of PHA?’)

[Source / Images: ‘Engineering Biodegradable PHA Blends’]

 

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SmarTech Analysis: Over 1.4 Million Kg of AM Copper Powders to Ship by 2029

SmarTech Analysis has published its most recent report on the copper additive manufacturing (AM) market, “Copper Additive Manufacturing 2020–Market Database and Outlook,” projecting that the segment is growing at a rapid pace. By 2029, we estimate that over 1.4 million kilograms of copper powder, both pure copper and copper alloys, will ship for AM use.

The report is made up of two parts: a market analysis of the copper AM sector and a database forecasting the copper AM segment throughout numerous subsegments and broken out in multiple ways across a 15-year projection period from 2014 to 2029. This includes estimates of how much copper powder (pure and alloy) each metal AM technology family has consumed in the past, does and will consume in the present and future in a range of verticals and geographical regions.

For instance, SmarTech has concluded that copper AM adoption will expand rapidly from now until 2029 at a compound annual growth rate of roughly 43 percent, particularly in the Asia Pacific region. And, while the copper 3D printing market is relatively small compared to titanium, it will represent an increasingly large chunk of the broader copper market.

We also anticipate that the total sales of copper AM systems will grow by 34 percent through to 2029, which will introduce opportunities for copper powder sales across all metal 3D printing families. In particular, powder bed fusion (PBF) and bound metal printing will represent the largest revenue opportunities, though directed energy deposition will also increase its market share, despite its comparatively small size.

3D-printed copper parts, including induction coils, made using Trumpf technology. Image courtesy of Trumpf.

Part of the reason for copper AM’s rapid growth is attributed to improvements in copper 3D printing processes and materials. We know that metal PBF technologies are making advances in the processing of pure copper and copper alloys and that these materials themselves are being formulated in ways that make it easier for PBF systems to 3D print with them. This is demonstrated by work by Trumpf, which is now being expanded via a partnership with Heraeus AMLOY. Additionally, bound metal printing technologies are proving themselves to be increasingly capable of 3D printing copper parts, exemplified by recent news from Markforged.

3D-printed copper parts made using bound metal deposition technology from Markforged. Image courtesy of Markforged.

As far as applications are concerned, the industry is proving valuable the use of copper 3D printing for the production of induction coils—now offered by a variety of service bureaus, including GKN Additive, Phoenix Contact, and GH Induction—and heat transfer components, such as heat exchangers and rocket propulsion parts.

3D-printed copper and stainless steel filters made by ExOne and the University of Pittsburgh.

Interestingly, the COVID-19 pandemic has demonstrated the niche potential of copper 3D printing for producing antimicrobial parts. The report discusses the rise of copper 3D printing for medical applications, including some of the stories that we’ve discussed during our coverage of the disease, such as copper door plates and handles by SPEE3D, antimicrobial filament from Copper3D and reusable copper filters 3D-printed by ExOne.

The report examines the current states of copper 3D printing, across all of the major metal AM technology families. Each present specific obstacles for processing the material using established AM system configurations, due to the metal’s physical characteristics, but each also present unique opportunities.

In addition to the analysis found in the report, the accompanying database has the unique feature of being easily integrated into existing internal market intelligence resources. SmarTech describes it well as an “off-the-shelf resource for market metrics and forecasts,” in that, while the report provides context for the database, the database is a versatile tool for providing actionable intelligence across business units.

Among the companies discussed in the report are EOS, Formalloy, Sandvik, Praxair Surface Technologies, Stratasys Direct Manufacturing, 3T and FIT AG, as well as others already mentioned here.

To learn more about the report and database, view its table of contents, or purchase the two-part resource, visit the SmarTech website.

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Université de Lorraine: Direct Waste Printing with PLA Pellets Versus FDM 3D Printing

French researchers from Université de Lorraine assess 3D printing techniques and recycling feedstocks, detailing their study in the recently published ‘Mechanical Properties of Direct Waste Printing of Polylactic Acid with Universal Pellets Extruder: Comparison to Fused Filament Fabrication on Open-Source Desktop Three-Dimensional Printers.’

While FDM (FFF) 3D printing has become highly accessible and affordable to users around the world, in this study the researchers also focus on the use of fused granular fabrication (FGF). Exploring the potential for continued ‘greening of distributed recycling,’ the researchers assess both FDM and FGF techniques for the desktop, experimenting with the following recycling filaments:

  • Commercial filament
  • Pellets
  • Distributed filament
  • Distributed pellets
  • Waste

Global framework of the experimentation. FFF, fused filament fabrication; FGF, fused granular fabrication; PLA, polylactic acid. Color images are available online.

A large part of the assessment included comprehensive studying of the granules (granulometry) used due to concerns regarding quality of reproducibility in the samples. Cost was substantially reduced, with material costing less than 1 €/kg – in comparison with 20 €/kg for commercial recycled filament. Better affordability coupled with quality in performance offers obvious benefit to users, with the potential for promoting a circular economy and efficient recycling.

“Due to the introduction of the open-source self-replicating rapid prototyper (RepRap), the dominant technology of 3D printing is fused filament fabrication (FFF) using polylactic acid (PLA),” stated the researchers. “Various forms of filament extrusion systems have proven effective at recycling PLA. However, PLA degrades with each cycle through the print/grind/extrude to filament/print loop.”

“This issue can be partially controlled by adding virgin PLA to recycled PLA, coatings, or carbon fiber reinforcement.”

By effectively eliminating the need to use filament and move directly to recycling waste, the researchers expect numerous benefits to continue emerging: reduced use of energy, faster production time, and less resources expending in making filament.

The following types of PLA were used:

  • Virgin, commercial PLA 4043D from NatureWorks (pellet form)
  • Recycled PLA filament from Formfutura for FFF printing
  • Recycled PLA filament produced in situ in ‘fablab conditions,’ meant for FFF printing
  • Pelletized feedstock for FGF
  • Shredded PLA from 3D printed waste, for FGF

In experimenting with the FFF system, the researchers used a Prusa i3 running Marlin firmware v1.1.9.

The FGF printer comprised a pellet extruder kit39 adapted to a commercial FFF printer (Créality CR-10S pro48) machine using a Marlin firmware v1.1.19. The pellet extrusion kit uses an auger screw with a diameter, cartridge heater –, and nozzle diameter that mixes and extrudes the melted material. The hot end of the FFF printer was adapted by replacing the pellet extruder prototype as shown in Figure 2. After the mechanical assembly was made, the first experimental tests were carried out to adapt the machine to the new parts and calibrate the formation of an extruded filament by using virgin PLA pellets. The extrusion factor was changed to calibrate the rotation of the screw extruder.

The FGF printer consisted of a pellet extruder attached to a Créality CR-10S pro 3D printer using Marlin firmware v1.1.19.

(a) FFF and (b) FGF printers used in the experimentation. Color images are available online.

Eight test samples were weighed and measured, and then evaluated for the following:

  • Tensile strength
  • Strain
  • Elastic modulus

Printability of shredded PLA materials. Color images are available online.

Printability of shredded PLA materials. Color images are available online.

“Regarding the economic aspect, using the FGF printer with virgin PLA pellets, there is a 65% reduction in printing cost per kilogram and a shorter production time compared with recycled commercial filaments, which is a non-negligible option. The results show that the main cost in 3D FFF printing is in the acquisition of filaments. However, the acquisition of recycled material filaments reduces the cost in relation to the acquisition of virgin material filaments, providing a reduction in the use of virgin raw material in 3D printing,” concluded the researchers.

“Opportunities arise in the possibility of using other types of recycled waste, including flexible and composite (plastic/plastic) materials as has been done on larger systems. Also, main factors such as polymer viscosity, which need to be controlled in the FGF process, are needed.”

Undoubtedly recycling will continue to be an ongoing theme in the 3D printing industry, with previous studies reflecting the state of recycling, solvent recycling, and circular chemical recycling. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Mechanical Properties of Direct Waste Printing of Polylactic Acid with Universal Pellets Extruder: Comparison to Fused Filament Fabrication on Open-Source Desktop Three-Dimensional Printers’]

The post Université de Lorraine: Direct Waste Printing with PLA Pellets Versus FDM 3D Printing appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

Universitat Politècnica de Catalunya BarcelonaTech: Characterization of 3D Printing for Ceramic Fuel Cell Electrolytes

Albert Folch Alcaraz recently submitted a Master’s thesis to the Universitat Politècnica de Catalunya BarcelonaTech. In ‘Mechanical and Microstructural Characterization of 3D Printed Ceramic Fuel Cells Electrolytes,’ Alcaraz delves further into digital fabrication using ceramic as a versatile material for creating solid oxide fuel cells—electrochemical devices capable of transforming chemical energy to electrical energy.

Striving to ‘bring science and society closer together,’ Alcaraz aims to develop energy devices that offer better efficiency, as well as offering clean energy that can be generated with less effect on our environment. Fuel cells are categorized regarding the types of electrolytes contained within, from low temperature (the alkaline fuel cell (AFC), the proton exchange membrane fuel cell, and the phosphoric acid fuel cell (PAFC)) to high temperature (operating at 500 – 1000 oC as two different types, the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC)).

SOFCs are made from ceramic, comprised of an anode that oxidizes and then sends electrons to the external circuit—and the oxidant which feeds into the cathode, thus ‘accepting’ electrons and then undergoing a reduction reaction. Electricity is created via electron flow from the anode to the cathode.

Working schematisation of a SOFC

Solid ceramic electrolytes prevent corrosion, offer superior mechanical performance for smaller, lighter weight structures, but do still present some challenges in terms of processing and temperatures.

“In theory, any gases capable of being electrochemically oxidized and reduced can be used as fuel and oxidant in a fuel cell,” states Alcaraz.

Working scheme of a fuel cell

Physical and chemical characteristics of the four components of a SOFC

For suitable performance, fuel cells must contain the following

  • High conversion efficiency
  • Environmental compatibility
  • Modularity
  • Sitting flexibility
  • Multifuel capability

Different applications of fuel cells; a) Fuel cell in the Toyota Mirai model and, b) a fuel cell for ships as part of a maritime project for the U.S. Department of Energy

More traditional techniques for production with ceramic materials include uniaxial and isostatic pressing, tape casting, slip casting, extrusion, and ceramic injection molding. 3D printing has been used in connection with ceramics and a variety of different projects around the world, to include the use of ceramic brick structures in architecture, porous ceramics with bioinspired materials, and establishing parameters in quality assurance.

Techniques such as powder bed binder jet/inkjet 3D printing are popular with the use of ceramics.

“It must be mentioned that although printed material in plaster-based printers is a ceramic material, if impregnated with and adhesive, it will not be a pure ceramic but a polymer-ceramic composite. As no extreme heating is required during and after processing, colors can be added to the part,” stated Alcaraz.

Examples of powder bed binder jet/inkjet 3D printed parts

Other popular 3D printing methods include selective laser melting (SLM), stereolithography (SLA), and robocasting. Alcaraz noted, however, that 3D printed samples demonstrated 98 percent relative density in comparison to tradition methods—and especially when compared to cold isostatic pressing.

“It has been demonstrated that the 3D printing specimens present similar micro- and nano- mechanical properties with the sample fabricated by a conventional processing route. In terms of the Vickers Hardness, the 3D printed specimens presented higher values than the specimen produced by CIP,” concluded the researchers. “As far as for the nanoindentation hardness and elastic modulus, the 3DP parts presented similar values of hardness. Nevertheless, it has been found that the values found for the elastic modulus are sensitive to different aspects such as the porosity and the roughness of the parts, giving less concise values.

“Concerning the reduction of printing defects, it is recommended to treat the feedstock before printing in order to achieve an homogenous particle size of the powder and be able to use a nozzle with a smaller diameter in order to enhance the resolution of the final 3D printed part. Finally, it would be interesting to follow the investigation of microcompression of the printed samples in order to extract the compression elastic modulus value through a different experiment and compare it to the nanoindentation technique. Furthermore, in the compression stress-strain curve obtained for the 3D printed specimen it is clear to observe a densification process (serrated zone) due to the presence of internal porosity heterogeneously distributed along the entire specimen.”

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Mechanical and Microstructural Characterization of 3D Printed Ceramic Fuel Cells Electrolytes’]

The post Universitat Politècnica de Catalunya BarcelonaTech: Characterization of 3D Printing for Ceramic Fuel Cell Electrolytes appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

“Best of Adafruit” Photo & Video Series Day 50 #photography #art #design #wfh #bestofadafruit

“Best of Adafruit” Photo & Video Series Day 50 #photography #art #design #wfh #bestofadafruit


Throughout this week, the Adafruit photo team will be posting a “Best of Adafruit” photo each day!

Check in as we take you back to all of our favorite photos and videos.

For our day 50 post, here’s a throwback to one of our favorite wearables learn guides, Cyber Punk Spikes, made out of NinjaFlex 3D printing filament!

Investigating Properties of Virgin, Sieved, and Waste 316L Metallic Powder for SLM 3D Printing

We often see metal 3D printing used to make steel parts, so plenty of research is being done regarding the material properties. Researchers from VSB – Technical University of Ostrava in the Czech Republic published a paper, “Research of 316L Metallic Powder for Use in SLM 3D Printing,” about investigating Renishaw’s AISI 316L powder for use in Selective Laser Melting (SLM) technology.

“Understanding the SLM process is extremely challenging, not only because of the large number of thermal, mechanical and chemical phenomena that take place here, but also in terms of metallurgy. The presence of three states (solid, liquid, gaseous) complicates the ability to analyze and formulate a model formula for proper simulation and prediction of part performance when printed,” they explained. “Since the SLM process operates on a powder basis, this process is more complicated by another factor compared to the use of other bulk material. The properties of the used printing powder define to a large extent the quality of the finished part.”

Because the material can impact an SLM 3D printed part’s final properties, powder research should be done ahead of time for best results. Particle size, shape, flowability, morphology, and size distribution are key factors in making a homogeneous powder layer, and using gas atomization to produce spherical particles helps achieve high packing density; this can also be improved with small particles.

The researchers investigated three phases of metallic powder present in the SLM process – virgin powder (manufacturer-supplied), test powder that had been sieved 30 times, and waste powder “that had settled in the sieve and was no longer being processed and disposed of.” They used a non-magnetic austenitic stainless steel, alloyed with elements like nickel and chromium and containing a low percentage of carbon.

Scanning electron microscopy (SEM) was used to investigate the powder morphology, which “affects the application of metal powder by laser in terms of fluidity and packing density.” First, the shape of the powder particles was measured and evaluated, and then a visual quality evaluation was completed to look at the spherical quality and satellite (shape irregularity) content. The team found that many particles had satellites, but that this number increased in over-sized powder.

Fig. 1. SEM image of virgin powder 316L, magnification x180

“The measurement of virgin powder (Fig. 1) reveals that the production of powder by gas atomization is not perfect and the shape of some particles is not perfectly spherical,” the researchers wrote. “It is also possible to observe satellites (small particles glued to larger ones, Fig. 2), which are again a defect of the production method.”

Fig. 2. Satellite illustration, magnification x900

They found that the particle shape was “not always isometric,” and that cylindrical, elongated, and irregular shapes appeared alongside spherical particles in over-sized powders.

“Another interesting phenomenon was manifested in the sieved powder, where particles with a smoother and more spherical surface were observed than the original particles. This is most likely due to the melting and solidification process that is specific to AM,” they noted.

Fig. 3. Morphological defects – a) particle fusion; b) gas impurities; c) agglomeration – sintered particle;
d) dendritic particle structure; e) spherical particle; f) particles with a satellite

An optical method was used to measure powder porosity. The 316L powder was embedded in a resin, and was “1 mm layer abraded” post-curing before the particles were cut in half and polished with diamond paste. The images captured via microscope were loaded into analysis software, which determined that the total density of the powder was 99.785%.

“In general, pores must be closed from 3/4 of their circumference to be considered pores,” the team explained. “Particles that do not comply with this rule are automatically considered irregular particles.”

Fig. 4. An example of open pores that correspond to the rule (L), and pores that do not conform (R)

The researchers also measured the size of all individual pores and recorded which ones began at 5 µm, though they noted that due to potential image resolution issues, “pore sizes of about 5-8 μm should be taken with some uncertainty.”

Fig. 5. Pore size measurement of 316L metallic powder

A histogram showed that, in the metallic powder particles, the “15 µm pore size was most present,” and that the largest was 30 µm.

Table 3. Measured values of porosity of powder particles

Finally, they used an optical method to measure and examine grain size distribution of the virgin and sifted powder. Using 200x magnification, measurements were taken at five random locations, each of which had roughly 200 particles on which they performed static analysis. The results were processed with statistical software, which created cumulative curves to indicate how many particles were smaller or larger than a certain size.

“Of these, the quantiles d10, d50 and d90 were obtained, which express the cut-off limit within which the size falls to 10, 50, 90 % of the measured particles,” they wrote.

The average particle size only increases a little by repeatedly sieving the metallic powder, but because of irregular particles, agglomerated or molten particles larger than 45 μm, they fall through the mesh. Results show that <10 µm particles are reduced, while larger particles are increased, in the sift powder. But, the team notes that the powder is still usable.

“The sift powder showed an increase in particle volume and surface area while circularity decreased, indicating that virgin powder generally has a higher sphericity,” the team explained.

They found defects like agglomeration, gas impurities, and particulate fusions at all three stages, but since the powder is still usable, they concluded that SLM is both an economic and ecological technology. The researchers listed several measures to take in order to “achieve the best possible consolidation,” such as high purity, fine surface, low internal porosity, tight particle distribution, and as few surface pores and satellites as possible.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.

The post Investigating Properties of Virgin, Sieved, and Waste 316L Metallic Powder for SLM 3D Printing appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

NASA Seeks Proposals to Advance AM Techniques for High Temperature Materials

The National Aeronautics and Space Administration (NASA) is seeking proposals from university research teams to develop unique, disruptive, and transformational space technologies that are currently at low technology readiness levels (TRL) but have the potential to lead to dramatic improvements at the system level. One of the topics of the Space Technology Research Grants (STRG) Program, Early Stage Innovations (ESI) appendix focuses on the advancement of additive manufacturing (AM) processing techniques for high-temperature materials.

Supporting education and research is a great way to advance the space exploration capabilities of NASA. In fact, according to the space agency, investment in innovative low-TRL research increases knowledge and capabilities in response to new questions and requirements; stimulates innovation, and allows more creative solutions to problems constrained by schedule and budget. Further suggesting that investment in fundamental research activities has historically benefited the United States by generating new industries and spin-off applications.

As an extension of the Space Technology Mission Directorate (STMD), the STRG Program is fostering the development of innovative, low-TRL technologies for advanced space systems. The goal of this particular endeavor is to accelerate the development of groundbreaking, high-risk but high-payoff, space technologies. It is not necessarily directed at a specific mission, but instead will support the future space exploration and science needs of NASA, other government agencies, and the commercial space sector; especially as plans for space colonization, lunar exploration, and future journeys to Mars advance.

Universities help drive many NASA projects today, researching everything from cube sat 3D printing to aerospace high-volume manufacturing. This new NASA solicitation is only for accredited US university proposals, and the research teams that apply for the STRG program can choose to focus on the advancement of AM processing techniques to improve properties of high-temperature refractory metals, particularly tungsten and tungsten alloys, as well as other refractory metals and alloys.

Deep space exploration mission prep (Credit: NASA)

As described by the agency, all the submitted proposals working on additive manufacturing processing techniques for refractory metals should address at least one of the following research areas:

  • Improving high-temperature material properties,
  • Improving surface roughness from the AM process to minimize future post-processing needs,
  • Altering surface characteristics to tailor emissivity and wetting properties (for example, to make them either hydrophobic or hydrophilic),
  • Developing AM techniques to eliminate/minimize porosity and microcracking of AM parts,
  • Developing post-processing techniques to eliminate/minimize the porosity and microcracking of AM parts,
  • Developing techniques and processes to improve the grain structure of AM refractory metals,
  • Developing AM techniques capable of fabricating with multiple metals at once, one of which is a refractory metal or alloy,
  • Developing refractory alloys that provide optimal properties for parts fabricated by AM methods.

Due to their high melting points and density, refractory metals and alloys are capable of operating at extreme temperatures and have become the frontrunners for many high-temperature aerospace components, as well as other high-temperature applications, such as nuclear reactors, electric furnaces, and welding.

Of all the metals in pure form, tungsten has the highest melting point of 6,192°F (3,422°C) and is often alloyed with other metals for strength. As some of the toughest materials found in nature, refractory metals could be ideal for spacecraft applications that have to endure severe heat during space travel. Space shuttles, for example, used to face intense temperatures when re-entering the Earth’s atmosphere, as high as 3000°F (1649°C). If space adventurers expect to travel to Mars and beyond, spacecraft need to be protected, and this early-stage research could determine the bases for the future development of protection needed for safe space journeys.

The aerospace industry is increasingly turning to AM for thermal management systems that are capable of operating at extreme temperatures. The agency proposed integrated thermal management systems as one example where additive manufacturing plays a fundamental role in enabling technology. High-temperature thermal management systems are potentially disruptive to a wide range of high-temperature NASA applications such as wing leading-edge systems, solar probes, and Nuclear Thermal Propulsion (NTP); and can benefit from improvements in the fabrication of refractory metal casing materials.

During this early stage research, NASA is solely focused on manufacturing under Earth’s gravity, and there is still no mention of demonstrating additive manufacturing capabilities in space. However, we can probably expect that as this research moves forward, zero gravity fabrication will be of interest.

European Space Agency astronaut Luca Parmitano tests experiments in space (Credit: NASA)

With a maximum award of $650,000 for a research period of three years or less, this research grant represents a great opportunity for academics focusing on AM processing techniques.

NASA considers that these investments create, fortify, and nurture the talent base of highly skilled engineers, scientists, and technologists to improve the country’s technological and economic competitiveness. The ESI Appendix challenges universities to examine the theoretical feasibility of new ideas and approaches that are critical to making science, space travel, and exploration more effective, affordable, and sustainable.

Historically black colleges and universities along with other minority-serving institutions are encouraged to submit proposals. Moreover, NASA encourages submission of ESI proposals by women, members of underrepresented minority groups, persons with disabilities, and faculty members who are early in their career.

As NASA seeks to develop unique, disruptive, and transformational space technologies, university researchers get a chance to participate in the next generation of space exploration efforts, that are a complement to many of the agency’s ongoing programs. The solicitation is available here and universities have time until May 20, 2020, to present their notice of intent, and until June 17, 2020, for proposals.

The post NASA Seeks Proposals to Advance AM Techniques for High Temperature Materials appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.