Tech
Advanced sensors peer inside the ‘black box’ of metal 3D printing
With the ability to print metal structures with complex shapes and unique mechanical properties, metal additive manufacturing (AM) could be revolutionary. However, without a better understanding of how metal AM structures behave as they are 3D printed, the technology remains too unreliable for widespread adoption in manufacturing and part quality remains a challenge.
Researchers in Lawrence Livermore National Laboratory (LLNL)’s nondestructive evaluation (NDE) group are tackling this challenge by developing first-of-their-kind approaches to look at how materials and structures evolve inside a metal AM structure during printing. These NDE techniques can become enabling technologies for metal AM, giving manufacturers the data they need to develop better simulations, processing parameters and predictive controls to ensure part quality and consistency.
“If you want people to use metal AM components out in the world, you need NDE,” said David Stobbe, group leader for NDE ultrasonics and sensors in the Materials Engineering Division (MED). “If we can prove that AM-produced parts behave as designed, it will allow them to proliferate, be used in safety-critical components in aerospace, energy and other sectors and hopefully open a new paradigm in manufacturing.”
Measuring in the middle
NDE techniques involve sending signals like X-rays, ultrasound or electrical currents through objects and observing signal changes to infer information or reconstruct an image of what’s inside. NDE is important for quality control in all manufactured parts, but for metal AM, it can also help catch printing problems before it’s too late.
Most metal AM techniques use heat to bind material together, and since metals are extremely sensitive to heat, structures can change a lot during printing. Heat diffuses from the print surface into the already-printed structure, which can affect how well the material binds, create failure-inducing defects and lead to inconsistent products.
“Evolving processes in the subsurface need to be measured and characterized if you want to have a consistent print quality,” said Saptarshi Mukherjee, a research scientist in the Lab’s Atmospheric, Earth and Energy Division (AEED). “This is very challenging because most of the current NDE technologies cannot see through heat, and even infrared cameras and antennas only detect heat at the surfaces.”
Mukherjee is part of a project to monitor internal temperature during laser powder-bed fusion (LPBF) metal AM using eddy currents, swirling loops of electrical current induced by applying magnetic fields. Eddy currents are sensitive to electrical conductivity, and since conductivity is a function of temperature, eddy current sensors provide real-time localized temperature information from inside structures.
Simulations from collaborators at Michigan State University suggested the approach was viable, and the group validated it with a simple experiment, resulting in a recent paper published in Scientific Reports.
“To our knowledge, this is the first time that eddy current sensors have been used to look at these very rapid non-equilibrium thermal processes, which are suggestive of the sort of thermal processes you would see in a metal AM process,” said MED postdoc Ethan Rosenberg.
Rosenberg is now leading the experimental testing for a follow-up study using closer to real-world conditions such as non-uniform heating and faster timescales.
Trailblazers
NDE group leader Joe Tringe launched the first Laboratory-Directed Research and Development (LDRD) project in the area in 2018 and ever since, the group has been treading new ground to keep pace with metal AM.
In their first project, the group showed that millimeter wave signatures could efficiently characterize the shape of individual droplets of liquid metal used to create structures in liquid metal jetting. They eventually collected enough data to train a machine learning algorithm to predict droplet shape.
“If we can combine that feedback with system modeling, we may be able to learn whether the print parameters are working or if they need to be changed, in real time, so that we end up with what we want when we’re done,” said Stobbe.
Follow-up projects expanded to electrical resistance tomography—which measures changes in a current’s voltage and electrical potential—X-ray computed tomography, ultrasound and neutron detection, with an emphasis on lattice structures and other complicated geometries.
The group also uses NDE to inspect processing parameters like sonication—using ultrasonic waves to create vibrations and improve homogenization—in laser-based metal AM.
In a recent study published in Communications Materials, the group and collaborators at Pennsylvania State University and Argonne National Laboratory proved they could use high-speed synchrotron X-ray imaging for these measurements. The technique is the first step toward understanding sonication’s impact on printing, which will help manufacturers optimize the process to improve part quality.
“A lot of things happen in these AM processes that affect the part, but without using NDE techniques, it’s kind of a black box,” said Rosenberg. “With ingenuity and good physical understanding, you can open that box to see what’s happening inside, and that will hopefully help you control the process.”
Enabling the future
The group plans to continue evolving, improving and generalizing a variety of NDE techniques for metal AM, since different techniques are better at measuring different types of information. They also hope to train machine learning algorithms for real-time monitoring and error correction during the print to improve success.
The information they collect along the way will be crucial to enabling widespread adoption of metal AM, and they hope that their work will also help raise awareness of the opportunities for NDE in the emerging field.
“There’s a real gold rush aspect to it,” said Stobbe. “You’re out there doing or measuring things that you know no one has ever done or measured before because this is a new technology, and that’s certainly exciting.”
Other contributors to the work include MED’s Rosa Morales, Jordan Lum, Edward Benavidez and collaborators at the University of Colorado, Boulder.
More information:
Lei Peng et al, In-situ 3D temperature field modeling and characterization using eddy current for metal additive manufacturing process monitoring, Scientific Reports (2025). DOI: 10.1038/s41598-025-94553-6
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Tech
Salesforce Workers Circulate Open Letter Urging CEO Marc Benioff to Denounce ICE
Employees at Salesforce are circulating an internal letter to chief executive Marc Benioff calling on him to denounce recent actions by US Immigration and Customs Enforcement, prohibit the use of Salesforce software by immigration agents, and back federal legislation that would significantly reform the agency.
The letter specifically cites the “recent killings of Renee Good and Alex Pretti in Minneapolis” as catalysts, calling them the “devastating indictment of a system that has discarded human decency.” It’s unclear how many signatories the letter has received so far.
The letter, which has not been reported on previously, is being organized amid Salesforce’s annual leadership kickoff event this week in Las Vegas. During an appearance at the event earlier today, Benioff asked international employees to stand to thank them for attending. He then joked that ICE agents were in the building monitoring them, according to current and former Salesforce employees who spoke to WIRED.
Benioff’s remarks sparked immediate backlash among employees. “Lots of people are furious,” says one source, who asked to remain anonymous for fear of retaliation. Another source tells WIRED that the internal pushback today was significantly more forceful than after Benioff made other controversial comments last fall supporting President Trump’s call to deploy the National Guard to San Francisco to address crime.
Salesforce did not immediately respond to a request for comment from WIRED. Business Insider and 404 Media previously reported on Benioff’s remarks and the reaction to them inside Salesforce.
“We are deeply troubled by leaked documentation revealing that Salesforce has pitched AI technology to U.S. Immigration and Customs Enforcement to help the agency ‘expeditiously’ hire 10,000 new agents and vet tip-line reports,” the letter reads. “Providing ‘Agentforce’ infrastructure to scale a mass deportation agenda that currently detains 66,000 people—73 percent of whom have no criminal record—represents a fundamental betrayal of our commitment to the ethical use of technology.”
The letter argues that Benioff’s voice “carries unique weight in Washington,” pointing to an episode last fall when Trump called off an ICE deployment in San Francisco after what appeared to be outreach from Bay Area tech leaders, including Benioff and Nvidia CEO Jensen Huang. It urges Benioff to use that influence as a “corporate statesman” to issue a public statement condemning what it calls ICE’s unconstitutional conduct and to commit Salesforce to clear “red lines” barring the use of its cloud and AI products for state violence.
Benioff has weighed in on both national and local political issues for years. He supported Democratic presidential candidate Hillary Clinton in 2016 and later became one of the most high-profile backers of Proposition C, a failed San Francisco ballot measure that would have raised taxes to fund programs to address homelessness. In 2020, he donated to the primary campaigns of some Democratic presidential candidates, including Kamala Harris.
But since Trump returned to the White House in January, Benioff has signaled greater support for some Republican leaders. In one interview, he said he strives to stay nonpartisan because he also owns Time magazine. But he also joked that, while he declined to contribute to Trump’s inauguration fund directly, he had “donated” a photo of the president on the magazine’s cover, which named him its 2024 Person of the Year. “He can use the Time magazine cover for free,” Benioff said in the interview with Fortune.
Benioff also faced backlash from Salesforce employees last fall when he suggested the National Guard should be sent to San Francisco to tackle crime ahead of the company’s annual conference in the city. He later apologized for the remarks, explaining they stemmed from genuine concerns about safety. He later reversed his stance and joined Nvidia’s Huang in asking Trump to refrain from sending troops.
Tech
Magnetic mixer improves 3D bioprinting
3D bioprinting, in which living tissues are printed with cells mixed into soft hydrogels, or “bio-inks,” is widely used in the field of bioengineering for modeling or replacing the tissues in our bodies. The print quality and reproducibility of tissues, however, can face challenges. One of the most significant challenges is created simply by gravity — cells naturally sink to the bottom of the bioink-extruding printer syringe because the cells are heavier than the hydrogel around them.
“This cell settling, which becomes worse during the long print sessions required to print large tissues, leads to clogged nozzles, uneven cell distribution, and inconsistencies between printed tissues,” explains Ritu Raman, the Eugene Bell Career Development Professor of Tissue Engineering and assistant professor of mechanical engineering at MIT. “Existing solutions, such as manually stirring bioinks before loading them into the printer, or using passive mixers, cannot maintain uniformity once printing begins.”
In a study published Feb. 2 in the journal Device, Raman’s team introduces a new approach that aims to solve this core limitation by actively preventing cell sedimentation within bioinks during printing, allowing for more reliable and biologically consistent 3D printed tissues.
“Precise control over the bioink’s physical and biological properties is essential for recreating the structure and function of native tissues,” says Ferdows Afghah, a postdoc in mechanical engineering at MIT and lead author of the study.
“If we can print tissues that more closely mimic those in our bodies, we can use them as models to understand more about human diseases, or to test the safety and efficacy of new therapeutic drugs,” adds Raman. Such models could help researchers move away from techniques like animal testing, which supports recent interest from the U.S. Food and Drug Administration in developing faster, less expensive, and more informative new approaches to establish the safety and efficacy of new treatment paths.
“Eventually, we are working towards regenerative medicine applications such as replacing diseased or injured tissues in our bodies with 3D printed tissues that can help restore healthy function,” says Raman.
MagMix, a magnetically actuated mixer, is composed of two parts: a small magnetic propeller that fits inside the syringes used by bioprinters to deposit bioinks, layer by layer, into 3D tissues, and a permanent magnet attached to a motor that moves up and down near the syringe, controlling the movement of the propeller inside. Together, this compact system can be mounted onto any standard 3D bioprinter, keeping bioinks uniformly mixed during printing without changing the bioink formulation or interfering with the printer’s normal operation. To test the approach, the team used computer simulations to design the optimal mixing propeller geometry and speed and then validated its performance experimentally.
“Across multiple bioink types, MagMix prevented cell settling for more than 45 minutes of continuous printing, reducing clogging and preserving high cell viability,” says Raman. “Importantly, we showed that mixing speeds could be adjusted to balance effective homogenization for different bioinks while inducing minimal stress on the cells. As a proof-of-concept, we demonstrated that MagMix could be used to 3D print cells that could mature into muscle tissues over the course of several days.”
By maintaining uniform cell distribution throughout long or complex print jobs, MagMix enables the fabrication of high-quality tissues with more consistent biological function. Because the device is compact, low-cost, customizable, and easily integrated into existing 3D printers, it offers a broadly accessible solution for laboratories and industries working toward reproducible engineered tissues for applications in human health including disease modeling, drug screening, and regenerative medicine.
This work was supported, in part, by the Safety, Health, and Environmental Discovery Lab (SHED) at MIT, which provides infrastructure and interdisciplinary expertise to help translate biofabrication innovations from lab-scale demonstrations to scalable, reproducible applications.
“At the SHED, we focus on accelerating the translation of innovative methods into practical tools that researchers can reliably adopt,” says Tolga Durak, the SHED’s founding director. “MagMix is a strong example of how the right combination of technical infrastructure and interdisciplinary support can move biofabrication technologies toward scalable, real-world impact.”
The SHED’s involvement reflects a broader vision of strengthening technology pathways that enhance reproducibility and accessibility across engineering and the life sciences by providing equitable access to advanced equipment and fostering cross-disciplinary collaboration.
“As the field advances toward larger-scale and more standardized systems, integrated labs like SHED are essential for building sustainable capacity,” Durak adds. “Our goal is not only to enable discovery, but to ensure that new technologies can be reliably adopted and sustained over time.”
The team is also interested in non-medical applications of engineered tissues, such as using printed muscles to power safer and more efficient “biohybrid” robots.
The researchers believe this work can improve the reliability and scalability of 3D bioprinting, making the potential impacts on the field of 3D bioprinting and on human health significant. Their paper, “Advancing Bioink Homogeneity in Extrusion 3D Bioprinting with Active In Situ Magnetic Mixing,” is available now from the journal Device.
Tech
The Physics Behind the Quadruple Axel, the Most Difficult Jump in Figure Skating
In figure skating, the quadruple axel is generally considered the most difficult jump. Until 2022, when US skater Ilia Malinin—currently riding high as the “Quad God” at the 2026 Winter Olympics—started doing them, they seemed impossible. Landing one, naturally, can give an athlete a higher score. But for skaters who aren’t generational talents like Malinin, grasping exactly how to pull off a quadruple axel can be tricky. But physics can offer some clues.
In 2024, the journal Sports Biomechanics published a study by Toin University researcher Seiji Hirosawa that brought science a little closer to understanding how quad axels work. One of the biggest factors? Getting high. Like 20 inches off the ground high.
In the current scoring system of figure skating competitions, the jury, which in the case of the Milano Cortina Games consists of two technical specialists and a technical controller, assigns a score to each technical element, namely jumps, spins, and steps. However, the scores for the more difficult jumps, such as triple or quadruple jumps, are higher than those for the other technical elements, so skaters must perform them correctly in order to win competitions.
Generally speaking the axel is the most technically complex of the jumps. There are three main types, each distinguished by their takeoffs: toe, blade, or edge. Most are named after the first person to do them; the axel is named after Norwegian skater Axel Paulsen. It is also the only one that involves a forward start, which leads the athlete to perform a half-turn more than other jumps. A simple axel, therefore, requires one and a half rotations to complete, while a quadruple axel requires four and a half rotations in the air.
To shed light on the specific kinematic strategies used by athletes to perform the quadruple axel jump, Hirosawa’s study focused on footage of two skaters who attempted this jump in competition. Using data from what’s known as the Ice Scope tracking system, researchers analyzed several parameters: vertical height, horizontal distance, and skating speed before takeoff and after landing.
Contrary to previous biomechanical studies, which suggested that jump height does not change significantly, Hirosawa’s study found that increasing jump height is crucial to successfully performing a quadruple axel jump. Both skaters, in fact, aimed to achieve significantly greater vertical heights in their attempts to perform this jump than in the triple axel.
“This suggests a strategic shift toward increasing vertical height to master 4A [quadruple axel] jumps, in contrast to previous biomechanical research that did not emphasize vertical height,” the study concluded.
Increased jump height, Hirosawa adds, provides increased flight time by allowing a large number of rotations around the longitudinal axis of the body. Short version: jump higher, turn more. “The results of this study provide valuable insights into the biomechanics of quadruple and triple axel jumps, update existing theories of figure skating research, and provide insights into training strategies for managing complex jumps,” the study concludes.
Easier said than done—unless you’re Ilia Malinin.
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