More than 50 large coal units were commissioned in 2025, up from less than 20 a year over the previous decade, a report says.

The first quarter of the 21st century was unusually warm by historical standards and so a prolonged cold spell this winter is unfamiliar to many people, especially younger Americans.

The shift away from desflurane has contributed to a nearly 30 percent decrease in anesthetic greenhouse gas emissions over a decade, says a study.

New Mexico’s Bootheel region, a typical destination for the bats, has been hit hard by drought.

MIT senior Katie Spivakovsky has been selected as a 2026-27 Churchill Scholar and will undertake an MPhil in biological sciences at the Wellcome Sanger Institute at Cambridge University in the U.K. this fall.

Spivakovsky, who is double-majoring in biological engineering and artificial intelligence, with minors in mathematics and biology, aims to integrate computation and bioengineering in an academic research career focused on developing robust, scalable solutions that promote equitable health outcomes.

At MIT’s Bathe BioNanoLab, Spivakovsky investigates therapeutic applications of DNA origami, DNA-scaffolded nanoparticles for gene and mRNA delivery, and co-authored a manuscript in press at Science. She leads the development of an immune therapy for cancer cachexia with a team supported by MIT’s BioMakerSpace; this work earned a silver medal at the international synthetic biology competition iGEM and was published in the MIT Undergraduate Research Journal. Previously, she worked on Merck’s Modeling & Informatics team, characterizing a cancer-associated protein mutation, and at the New York Structural Biology Center, where she improved cryogenic electron microscopy particle detection models.

On campus, Spivakovsky serves as director of the Undergraduate Initiative in the MIT Biotech Group. She is deeply committed to teaching and mentoring, and has served as a lecturer and co-director for class 6.S095 (Probability Problem Solving), a teaching assistant for classes 20.309 (Bioinstrumentation) and 20.A06 (Hands-on Making in Biological Engineering), a lab assistant for 6.300 (Signal Processing), and as an associate advisor.

“Katie is a brilliant researcher who has a keen intellectual curiosity that will make her a leader in biological engineering in the future. We are proud that she will be representing MIT at Cambridge University,” says Kim Benard, associate dean of distinguished fellowships.

The Churchill Scholarship is a highly competitive fellowship that annually offers 16 American students the opportunity to pursue a funded graduate degree in science, mathematics, or engineering at Churchill College within Cambridge University. The scholarship, established in 1963, honors former British Prime Minister Winston Churchill’s vision for U.S.-U.K. scientific exchange. Since 2017, two Kanders Churchill Scholarships have also been awarded each year for studies in science policy.

MIT students interested in learning more about the Churchill Scholarship should contact Kim Benard in MIT Career Advising and Professional Development.

How can artificial intelligence step out of a screen and become something we can physically touch and interact with?

That question formed the foundation of class 4.043/4.044 (Interaction Intelligence), an MIT course focused on designing a new category of AI-driven interactive objects. Known as large language objects (LLOs), these physical interfaces extend large language models into the real world. Their behaviors can be deliberately generated for specific people or applications, and their interactions can evolve from simple to increasingly sophisticated — providing meaningful support for both novice and expert users.

“I came to the realization that, while powerful, these new forms of intelligence still remain largely ignorant of the world outside of language,” says Marcelo Coelho, associate professor of the practice in the MIT Department of Architecture, who has been teaching the design studio for several years and directs the Design Intelligence Lab. “They lack real-time, contextual understanding of our physical surroundings, bodily experiences, and social relationships to be truly intelligent. In contrast, LLOs are physically situated and interact in real time with their physical environment. The course is an attempt to both address this gap and develop a new kind of design discipline for the age of AI.”

Given the assignment to design an interactive device that they would want in their lives, students Jacob Payne and Ayah Mahmoud focused on the kitchen. While they each enjoy cooking and baking, their design inspiration came from the first home computer: the Honeywell 316 Kitchen Computer, marketed by Neiman Marcus in 1969. Priced at $10,000, there is no record of one ever being sold.

“It was an ambitious but impractical early attempt at a home kitchen computer,” says Payne, an architecture graduate student. “It made an intriguing historical reference for the project.”

“As somebody who likes learning to cook — especially now, in college as an undergrad — the thought of designing something that makes cooking easy for those who might not have a cooking background and just wants a nice meal that satisfies their cravings was a great starting point for me,” says Mahmoud, a senior design major.

“We thought about the leftover ingredients you have in the refrigerator or pantry, and how AI could help you find new creative uses for things that you may otherwise throw away,” says Payne.

Generative cuisine

The students designed their device — named Kitchen Cosmo — with instructions to function as a “recipe generator.” One challenge was prompting the LLM to consistently acknowledge real-world cooking parameters, such as heating, timing, or temperature. One issue they worked out was having the LLM recognize flavor profiles and spices accurate to regional and cultural dishes around the world to support a wider range of cuisines. Troubleshooting included taste-testing recipes Kitchen Cosmo generated. Not every early recipe produced a winning dish.

“There were lots of small things that AI wasn't great at conceptually understanding,” says Mahmoud. “An LLM needs to fundamentally understand human taste to make a great meal.”

They fine-tuned their device to allow for the myriad ways people approach preparing a meal. Is this breakfast, lunch, dinner, or a snack? How advanced of a cook are you? How much meal prep time do you have? How many servings will you make? Dietary preferences were also programmed, as well as the type of mood or vibe you want to achieve. Are you feeling nostalgic, or are you in a celebratory mood? There’s a dial for that.

“These selections were the focal point of the device because we were curious to see how the LLM would interpret subjective adjectives as inputs and use them to transform the type of recipe outputs we would get,” says Payne.

Unlike most AI interactions that tend to be invisible, Payne and Mahmoud wanted their device to be more of a “partner” in the kitchen. The tactile interface was intentionally designed to structure the interaction, giving users a physical control over how the AI responded.

“While I’ve worked with electronics and hardware before, this project pushed me to integrate the components with a level of precision and refinement that felt much closer to a product-ready device,” says Payne of the course work.

Retro and red

After their electronic work was completed, the students designed a series of models using cardboard until settling on the final look, which Payne describes as “retro.” The body was designed in a 3D modeling software and printed. In a nod to the original Honeywell computer, they painted it red.

A thin, rectangular device about 18 inches in height, Kitchen Cosmo has a webcam that hinges open to scan ingredients set on a counter. It translates these into a recipe that takes into consideration general spices and condiments common in most households. An integrated thermal printer delivers a printed recipe that is torn off. Recipes can be stored in a plastic receptacle on its base.

While Kitchen Cosmo made a modest splash in design magazines, both students have ideas where they will take future iterations.

Payne would like to see it “take advantage of a lot of the data we have in the kitchen and use AI as a mediator, offering tips for how to improve on what you’re cooking at that moment.”

Mahmoud is looking at how to optimize Kitchen Cosmo for her thesis. Classmates have given feedback to upgrade its abilities. One suggestion is to provide multi-person instructions that give several people tasks needed to complete a recipe. Another idea is to create a “learning mode” in which a kitchen tool — for example, a paring knife — is set in front of Kitchen Cosmo, and it delivers instructions on how to use the tool. Mahmoud has been researching food science history as well.

“I’d like to get a better handle on how to train AI to fully understand food so it can tailor recipes to a user’s liking,” she says.

Having begun her MIT education as a geologist, Mahmoud’s pivot to design has been a revelation, she says. Each design class has been inspiring. Coelho’s course was her first class to include designing with AI. Referencing the often-mentioned analogy of “drinking from a firehouse” while a student at MIT, Mahmoud says the course helped define a path for her in product design.

“For the first time, in that class, I felt like I was finally drinking as much as I could and not feeling overwhelmed. I see myself doing design long-term, which is something I didn’t think I would have said previously about technology.” 

What if ultrasound imaging is no longer confined to hospitals? Patients with chronic conditions, such as hypertension and heart failure, could be monitored continuously in real-time at home or on the move, giving health care practitioners ongoing clinical insights instead of the occasional snapshots — a scan here and a check-up there. This shift from reactive, hospital-based care to preventative, community and home-based care could enable earlier detection and timely intervention, and truly personalized care.

Bringing this vision to reality, the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, has launched a new collaborative research project: Wearable Imaging for Transforming Elderly Care (WITEC). 

WITEC marks a pioneering effort in wearable technology, medical imaging, research, and materials science. It will be dedicated to foundational research and development of the world’s first wearable ultrasound imaging system capable of 48-hour intermittent cardiovascular imaging for continuous and real-time monitoring and diagnosis of chronic conditions such as hypertension and heart failure. 

This multi-million dollar, multi-year research program, supported by the National Research Foundation (NRF) Singapore under its Campus for Research Excellence and Technological Enterprise program, brings together top researchers and expertise from MIT, Nanyang Technological University (NTU Singapore), and the National University of Singapore (NUS). Tan Tock Seng Hospital (TTSH) is WITEC’s clinical collaborator and will conduct patient trials to validate long-term heart imaging for chronic cardiovascular disease management.

“Addressing society’s most pressing challenges requires innovative, interdisciplinary thinking. Building on SMART’s long legacy in Singapore as a hub for research and innovation, WITEC will harness interdisciplinary expertise — from MIT and leading institutions in Singapore — to advance transformative research that creates real-world impact and benefits Singapore, the U.S., and societies all over. This is the kind of collaborative research that not only pushes the boundaries of knowledge, but also redefines what is possible for the future of health care,” says Bruce Tidor, chief executive officer and interim director of SMART, who is also an MIT professor of biological engineering and electrical engineering and computer science.

Industry-leading precision equipment and capabilities

To support this work, WITEC’s laboratory is equipped with advanced tools, including Southeast Asia’s first sub-micrometer 3D printer and the latest Verasonics Vantage NXT 256 ultrasonic imaging system, which is the first unit of its kind in Singapore.

Unlike conventional 3D printers that operate at millimeter or micrometer scales, WITEC’s 3D printer can achieve sub‑micrometer resolution, allowing components to be fabricated at the level of single cells or tissue structures. With this capability, WITEC researchers can prototype bioadhesive materials and device interfaces with unprecedented accuracy — essential to ensuring skin‑safe adhesion and stable, long‑term imaging quality.

Complementing this is the latest Verasonics ultrasonic imaging system. Equipped with a new transducer adapter and supporting a significantly larger number of probe control channels than existing systems, it gives researchers the freedom to test highly customized imaging methods. This allows more complex beamforming, higher‑resolution image capture, and integration with AI‑based diagnostic models — opening the door to long‑duration, real‑time cardiovascular imaging not possible with standard hospital equipment.

Together, these technologies allow WITEC to accelerate the design, prototyping, and testing of its wearable ultrasound imaging system, and to demonstrate imaging quality on phantoms and healthy subjects.

Transforming chronic disease care through wearable innovation 

Chronic diseases are rising rapidly in Singapore and globally, especially among the aging population and individuals with multiple long-term conditions. This trend highlights the urgent need for effective home-based care and easy-to-use monitoring tools that go beyond basic wellness tracking.

Current consumer wearables, such as smartwatches and fitness bands, offer limited physiological data like heart rate or step count. While useful for general health, they lack the depth needed to support chronic disease management. Traditional ultrasound systems, although clinically powerful, are bulky, operator-dependent, can only be deployed episodically within the hospitals, and are limited to snapshots in time, making them unsuitable for long-term, everyday use.

WITEC aims to bridge this gap with its wearable ultrasound imaging system that uses bioadhesive technology to enable up to 48 hours of uninterrupted imaging. Combined with AI-enhanced diagnostics, the innovation is aimed at supporting early detection, home-based pre-diagnosis, and continuous monitoring of chronic diseases.

Beyond improving patient outcomes, this innovation could help ease labor shortages by freeing up ultrasound operators, nurses, and doctors to focus on more complex care, while reducing demand for hospital beds and resources. By shifting monitoring to homes and communities, WITEC’s technology will enable patient self-management and timely intervention, potentially lowering health-care costs and alleviating the increasing financial and manpower pressures of an aging population.

Driving innovation through interdisciplinary collaboration

WITEC is led by the following co-lead principal investigators: Xuanhe Zhao, professor of mechanical engineering and professor of civil and environmental engineering at MIT; Joseph Sung, senior vice president of health and life sciences at NTU Singapore and dean of the Lee Kong Chian School of Medicine (LKCMedicine); Cher Heng Tan, assistant dean of clinical research at LKCMedicine; Chwee Teck Lim, NUS Society Professor of Biomedical Engineering at NUS and director of the Institute for Health Innovation and Technology at NUS; and Xiaodong Chen, distinguished university professor at the School of Materials Science and Engineering within NTU. 

“We’re extremely proud to bring together an exceptional team of researchers from Singapore and the U.S. to pioneer core technologies that will make wearable ultrasound imaging a reality. This endeavor combines deep expertise in materials science, data science, AI diagnostics, biomedical engineering, and clinical medicine. Our phased approach will accelerate translation into a fully wearable platform that reshapes how chronic diseases are monitored, diagnosed and managed,” says Zhao, who serves as a co-lead PI of WITEC.

Research roadmap with broad impact across health care, science, industry, and economy

Bringing together leading experts across interdisciplinary fields, WITEC will advance foundational work in soft materials, transducers, microelectronics, data science and AI diagnostics, clinical medicine, and biomedical engineering. As a deep-tech R&D group, its breakthroughs will have the potential to drive innovation in health-care technology and manufacturing, diagnostics, wearable ultrasonic imaging, metamaterials, diagnostics, and AI-powered health analytics. WITEC’s work is also expected to accelerate growth in high-value jobs across research, engineering, clinical validation, and health-care services, and attract strategic investments that foster biomedical innovation and industry partnerships in Singapore, the United States, and beyond.

“Chronic diseases present significant challenges for patients, families, and health-care systems, and with aging populations such as Singapore, those challenges will only grow without new solutions. Our research into a wearable ultrasound imaging system aims to transform daily care for those living with cardiovascular and other chronic conditions — providing clinicians with richer, continuous insights to guide treatment, while giving patients greater confidence and control over their own health. WITEC’s pioneering work marks an important step toward shifting care from episodic, hospital-based interventions to more proactive, everyday management in the community,” says Sung, who serves as co‑lead PI of WITEC.

Led by Violet Hoon, senior consultant at TTSH, clinical trials are expected to commence this year to validate long-term heart monitoring in the management of chronic cardiovascular disease. Over the next three years, WITEC aims to develop a fully integrated platform capable of 48-hour intermittent imaging through innovations in bioadhesive couplants, nanostructured metamaterials, and ultrasonic transducers.

As MIT’s research enterprise in Singapore, SMART is committed to advancing breakthrough technologies that address pressing global challenges. WITEC adds to SMART’s existing research endeavors that foster a rich exchange of ideas through collaboration with leading researchers and academics from the United States, Singapore, and around the world in key areas such as antimicrobial resistance, cell therapy development, precision agriculture, AI, and 3D-sensing technologies.

Microsoft gives the FBI the ability to decrypt BitLocker in response to court orders: about twenty times per year.

It’s possible for users to store those keys on a device they own, but Microsoft also recommends BitLocker users store their keys on its servers for convenience. While that means someone can access their data if they forget their password, or if repeated failed attempts to login lock the device, it also makes them vulnerable to law enforcement subpoenas and warrants.

The administration has preserved a $9.7 billion Biden-era initiative to bring renewable energy to rural areas.

The audacious plan, which would tap solar energy, collides with President Donald Trump’s efforts to expand fossil fuels to power AI.

Climate hawks and conservatives will clash as highway bill negotiations rev up in the coming weeks.

Congress is weighing several proposals that would add levies to the purchase or ownership of electric vehicles.

A federal judge sided with Sunrise Wind on Monday in its bid to lift the administration’s freeze on construction of the project.

The Sunrise Movement is organizing late-night protests outside hotels housing ICE agents.

A total of nine firms plan to join the voluntary trial to purchase sustainable aviation fuel through the Singapore Sustainable Aviation Fuel Co. being established.

The plan targets power, steel, cement, refineries and chemicals over the next five years, India’s finance minister said.

The crisis has reignited anger toward President Javier Milei, whose harsh austerity drive has slashed spending on programs and agencies that not only work to combat fires but also protect parks.

Italy’s civil protection agency said two landslides hit the town of Niscemi after torrential rain, impacting the local road network, damaging buildings and disrupting essential services.

More than 100 million people in the United States suffer from metabolic dysfunction-associated steatotic liver disease (MASLD), characterized by a buildup of fat in the liver. This condition can lead to the development of more severe liver disease that causes inflammation and fibrosis.

In hopes of discovering new treatments for these liver diseases, MIT engineers have designed a new type of tissue model that more accurately mimics the architecture of the liver, including blood vessels and immune cells.

Reporting their findings today in Nature Communications, the researchers showed that this model could accurately replicate the inflammation and metabolic dysfunction that occur in the early stages of liver disease. Such a device could help researchers identify and test new drugs to treat those conditions.

This is the latest study in a larger effort by this team to use these types of tissue models, also known as microphysiological systems, to explore human liver biology, which cannot be easily replicated in mice or other animals.

In another recent paper, the researchers used an earlier version of their liver tissue model to explore how the liver responds to resmetirom. This drug is used to treat an advanced form of liver disease called metabolic dysfunction-associated steatohepatitis (MASH), but it is only effective in about 30 percent of patients. The team found that the drug can induce an inflammatory response in liver tissue, which may help to explain why it doesn’t help all patients.

“There are already tissue models that can make good preclinical predictions of liver toxicity for certain drugs, but we really need to better model disease states, because now we want to identify drug targets, we want to validate targets. We want to look at whether a particular drug may be more useful early or later in the disease,” says Linda Griffith, the School of Engineering Professor of Teaching Innovation at MIT, a professor of biological engineering and mechanical engineering, and the senior author of both studies.

Former MIT postdoc Dominick Hellen is the lead author of the resmetirom paper, which appeared Jan. 14 in Communications Biology. Erin Tevonian PhD ’25 and PhD candidate Ellen Kan, both in the Department of Biological Engineering, are the lead authors of today’s Nature Communications paper on the new microphysiological system.

Modeling drug response

In the Communications Biology paper, Griffith’s lab worked with a microfluidic device that she originally developed in the 1990s, known as the LiverChip. This chip offers a simple scaffold for growing 3D models of liver tissue from hepatocytes, the primary cell type in the liver.

This chip is widely used by pharmaceutical companies to test whether their new drugs have adverse effects on the liver, which is an important step in drug development because most drugs are metabolized by the liver.

For the new study, Griffith and her students modified the chip so that it could be used to study MASLD.

Patients with MASLD, a buildup of fat in the liver, can eventually develop MASH, a more severe disease that occurs when scar tissue called fibrosis forms in the liver. Currently, resmetirom and the GLP-1 drug semaglutide are the only medications that are FDA-approved to treat MASH. Finding new drugs is a priority, Griffith says.

“You’re never declaring victory with liver disease with one drug or one class of drugs, because over the long term there may be patients who can’t use them, or they may not be effective for all patients,” she says.

To create a model of MASLD, the researchers exposed the tissue to high levels of insulin, along with large quantities of glucose and fatty acids. This led to a buildup of fatty tissue and the development of insulin resistance, a trait that is often seen in MASLD patients and can lead to type 2 diabetes.

Once that model was established, the researchers treated the tissue with resmetirom, a drug that works by mimicking the effects of thyroid hormone, which stimulates the breakdown of fat.

To their surprise, the researchers found that this treatment could also lead to an increase in immune signaling and markers of inflammation.

“Because resmetirom is primarily intended to reduce hepatic fibrosis in MASH, we found the result quite paradoxical,” Hellen says. “We suspect this finding may help clinicians and scientists alike understand why only a subset of patients respond positively to the thyromimetic drug. However, additional experiments are needed to further elucidate the underlying mechanism.”

A more realistic liver model

In the Nature Communications paper, the researchers reported a new type of chip that allows them to more accurately reproduce the architecture of the human liver. The key advance was developing a way to induce blood vessels to grow into the tissue. These vessels can deliver nutrients and also allow immune cells to flow through the tissue.

“Making more sophisticated models of liver that incorporate features of vascularity and immune cell trafficking that can be maintained over a long time in culture is very valuable,” Griffith says. “The real advance here was showing that we could get an intimate microvascular network through liver tissue and that we could circulate immune cells. This helped us to establish differences between how immune cells interact with the liver cells in a type two diabetes state and a healthy state.”

As the liver tissue matured, the researchers induced insulin resistance by exposing the tissue to increased levels of insulin, glucose, and fatty acids.

As this disease state developed, the researchers observed changes in how hepatocytes clear insulin and metabolize glucose, as well as narrower, leakier blood vessels that reflect microvascular complications often seen in diabetic patients. They also found that insulin resistance leads to an increase in markers of inflammation that attract monocytes into the tissue. Monocytes are the precursors of macrophages, immune cells that help with tissue repair during inflammation and are also observed in the liver of patients with early-stage liver disease.

“This really shows that we can model the immune features of a disease like MASLD, in a way that is all based on human cells,” Griffith says.

The research was funded by the National Institutes of Health, the National Science Foundation Graduate Research Fellowship program, NovoNordisk, the Massachusetts Life Sciences Center, and the Siebel Scholars Foundation.

The plastic bottle you just tossed in the recycling bin could provide structural support for your future house.

MIT engineers are using recycled plastic to 3D print construction-grade beams, trusses, and other structural elements that could one day offer lighter, modular, and more sustainable alternatives to traditional wood-based framing.

In a paper published in the Solid FreeForm Fabrication Symposium Proceedings, the MIT team presents the design for a 3D-printed floor truss system made from recycled plastic.

A traditional floor truss is made from wood beams that connect via metal plates in a pattern resembling a ladder with diagonal rungs. Set on its edge and combined with other parallel trusses, the resulting structure provides support for flooring material such as plywood that lies over the trusses.

The MIT team printed four long trusses out of recycled plastic and configured them into a conventional plywood-topped floor frame, then tested the structure’s load-bearing capacity. The printed flooring held over 4,000 pounds, exceeding key building standards set by the U.S. Department of Housing and Urban Development.

The plastic-printed trusses weigh about 13 pounds each, which is lighter than a comparable wood-based truss, and they can be printed on a large-scale industrial printer in under 13 minutes. In addition to floor trusses, the group is working on printing other elements and combining them into a full frame for a modest-sized home.

The researchers envision that as global demand for housing eclipses the supply of wood in the coming years, single-use plastics such as water bottles and food containers could get a second life as recycled framing material to alleviate both a global housing crisis and the overwhelming demand for timber.

“We’ve estimated that the world needs about 1 billion new homes by 2050. If we try to make that many homes using wood, we would need to clear-cut the equivalent of the Amazon rainforest three times over,” says AJ Perez, a lecturer in the MIT School of Engineering and research scientist in the MIT Office of Innovation. “The key here is: We recycle dirty plastic into building products for homes that are lighter, more durable, and sustainable.”

Perez’ co-authors on the study are graduate students Tyler Godfrey, Kenan Sehnawi, Arjun Chandar, and professor of mechanical engineering David Hardt, who are all members of the MIT Laboratory for Manufacturing and Productivity.

Printing dirty

In 2019, Perez and Hardt started MIT HAUS, a group within the Laboratory for Manufacturing and Productivity that aims to produce homes from recycled polymer products, using large-scale additive manufacturing, which encompasses technologies that are capable of producing big structures, layer-by-layer, in relatively short timescales.

Today, some companies are exploring large-scale additive manufacturing to 3D-print modest-sized homes. These efforts mainly focus on printing with concrete or clay — materials that have had a large negative environmental impact associated with their production. The house structures that have been printed so far are largely walls. The MIT HAUS group is among the first to consider printing structural framing elements such as foundation pilings, floor trusses, stair stringers, roof trusses, wall studs, and joists.

What’s more, they are seeking to do so not with cement, but with recycled “dirty” plastic — plastic that doesn’t have to be cleaned and preprocessed before reuse. The researchers envision that one day, used bottles and food containers could be fed directly into a shredder, pelletized, then fed into a large-scale additive manufacturing machine to become structural composite construction components. The plastic composite parts would be light enough to transport via pickup truck rather than a traditional lumber-hauling 18-wheeler. At the construction site, the elements could be quickly fitted into a lightweight yet sturdy home frame.

“We are starting to crack the code on the ability to process and print really dirty plastic,” Perez says. “The questions we’ve been asking are, what is the dirty, unwanted plastic good for, and how do we use the dirty plastic as-is?”

Weight class

The team’s new study is one step toward that overall goal of sustainable, recycled construction. In this work, they developed a design for a printed floor truss made from recycled plastic. They designed the truss with a high stiffness-to-weight ratio, meaning that it should be able to support a given amount of weight with minimal deflection, or bending. (Think of being able to walk across a floor without it sagging between the joists.)

The researchers first explored a handful of possible truss designs in simulation, and put each design through a simulated load-bearing test. Their modeling showed that one design in particular exhibited the highest stiffness-to-weight ratio and was therefore the most promising pattern to print and physically test. The design is close to the traditional wood-based floor truss pattern resembling a ladder with diagonal, triangular rungs. The team made a slight adjustment to this design, adding small reinforcing elements to each node where a “rung” met the main truss frame.

To print the design, Perez and his colleagues went to MIT’s Bates Research and Engineering Center, which houses the group’s industrial-scale 3D printer — a room-sized industrial machine that is capable of printing large structures at a fast rate of up to 80 pounds of material per hour. For their preliminary study, the researchers used pellets made of a combination of recycled PET polymers and glass fibers — a mixture that improves the material’s printability and durability. They obtained the material from an aerospace materials company, and then fed the pellets into the printer as composite “ink.”   

The team printed four trusses, each measuring 8 feet long, 1 foot high, and about 1 inch wide. Each truss took about 13 minutes to print. Perez and Godfrey spaced the trusses apart in a parallel configuration similar to traditional wood-based trusses, and screwed them into a sheet of plywood to mimic a 4-x-8-foot floor frame. They placed bags of sand and concrete of increasing weight in the center of the flooring system and measured the amount of deflection that the trusses experienced underneath.

The trusses easily withstood loads of 300 pounds, well above the deflection standards set by the U.S. by the Department of Housing and Urban Development. They didn’t stop there, continuing to add weight. Only when the loads reached over 4,000 pounds did the trusses finally buckle and crack.

In terms of stiffness, the printed trusses meet existing building codes in the U.S. To make them ready for wide adoption, Perez says the cost of producing the structures will have to be brought down to compete with the price of wood. The trusses in the new study were printed using recycled plastic, but from a source that he describes as the “crème de la crème of recycled feedstocks.” The plastic is factory-discarded material, but is not quite the “dirty” plastic that he aims ultimately to shred, print, and build.

The current study demonstrates that it is possible to print structural building elements from recycled plastic. Perez is in the process of working with dirtier plastic such as used soda bottles — that still hold a bit of liquid residue — to see how such contaminants affect the quality of the printed product.

If dirty plastics can be made into durable housing structures, Perez says “the idea is to bring shipping containers close to where you know you’ll have a lot of plastic, like next to a football stadium. Then you could use off-the-shelf shredding technology and feed that dirty shredded plastic into a large-scale additive manufacturing system, which could exist in micro-factories, just like bottling centers, around the world. You could print the parts for entire buildings that would be light enough to transport on a moped or pickup truck to where homes are most needed.”

This research was supported, in part, by the Gerstner Foundation, the Chandler Health of the Planet grant, and Cincinnati Incorporated.