(MIT: Cambridge, MA) -- 3D printing has come a long way since the 1980s, when Chuck Hull pioneered stereolithography—a technique that solidifies liquid resin into solid objects using ultraviolet lasers. Over the decades, 3D printers have evolved from experimental curiosities into tools capable of producing everything from custom prosthetics to complex food designs, architectural models, and even functioning human organs. 

But as the technology matures, its environmental footprint has become increasingly difficult to set aside. The vast majority of consumer and industrial 3D printing still relies on petroleum-based plastic filament. And while “greener” alternatives made from biodegradable or recycled materials exist, they come with a serious trade-off: They’re often not as strong. These eco-friendly filaments tend to become brittle under stress, making them ill-suited for structural applications or load-bearing parts—exactly where strength matters most.

This trade-off between sustainability and mechanical performance prompted researchers at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) and the Hasso Plattner Institute to ask: Is it possible to build objects that are mostly eco-friendly but still strong where it counts?

Their answer is SustainaPrint, a new software and hardware tool kit designed to help users strategically combine strong and weak filaments to get the best of both worlds. Instead of printing an entire object with high-performance plastic, the system analyzes a model through finite element analysis simulations, predicts where the object is most likely to experience stress, and then reinforces just those zones with stronger material. The rest of the part can be printed using greener, weaker filament, reducing plastic use while preserving structural integrity.

“Our hope is that SustainaPrint can be used in industrial and distributed manufacturing settings one day, where local material stocks may vary in quality and composition,” says Maxine Perroni-Scharf, an MIT Ph.D. student, CSAIL researcher, and lead author on a paper presenting the project. “In these contexts, the testing tool kit could help ensure the reliability of available filaments, while the software’s reinforcement strategy could reduce overall material consumption without sacrificing function.” 

For its experiments, the team used Polymaker’s PolyTerra PLA as the eco-friendly filament, and standard or Tough PLA from Ultimaker for reinforcement. A 20% reinforcement threshold was used to show that even a small amount of strong plastic goes a long way. Using this ratio, SustainaPrint was able to recover up to 70% of the strength of an object printed entirely with high-performance plastic.

The team printed dozens of objects, from simple mechanical shapes like rings and beams to more functional household items such as headphone stands, wall hooks, and plant pots. Each object was printed three ways: once using only eco-friendly filament, once using only strong PLA, and once with the hybrid SustainaPrint configuration. The printed parts were then mechanically tested by pulling, bending, or otherwise breaking them to measure how much force each configuration could withstand. 

In many cases, the hybrid prints held up nearly as well as the full-strength versions. For example, in one test involving a dome-like shape, the hybrid version outperformed the version printed entirely in Tough PLA. The team believes this may be due to the reinforced version’s ability to distribute stress more evenly, preventing the brittle failure sometimes caused by excessive stiffness.

“This indicates that in certain geometries and loading conditions, mixing materials strategically may actually outperform a single homogenous material,” says Perroni-Scharf. “It’s a reminder that real-world mechanical behavior is full of complexity, especially in 3D printing, where interlayer adhesion and tool-path decisions can affect performance in unexpected ways.”

A lean, green, eco-friendly printing machine

SustainaPrint starts by letting a user upload their 3D model into a custom interface. By selecting fixed regions and areas where forces will be applied, the software then uses an approach called finite element analysis to simulate how the object will deform under stress. It then creates a map showing pressure distribution inside the structure, highlighting areas under compression or tension. It applies heuristics to segment the object into two categories: those that need reinforcement and those that don’t.

Recognizing the need for accessible and low-cost testing, the team also developed a DIY testing tool kit to help users assess strength before printing. The kit has a 3D-printable device with modules for measuring both tensile and flexural strength. Users can pair the device with everyday items, such as pull-up bars or digital scales, to obtain rough but reliable performance metrics. The team benchmarked its results against manufacturer data and found that its measurements consistently fell within one standard deviation, even for filaments that had undergone multiple recycling.

Although the current system is designed for dual-extrusion printers, the researchers believe that with some manual filament swapping and calibration, it could be adapted for single-extruder setups, too. In its current form, the system simplifies the modeling process by allowing just one force and one fixed boundary per simulation. Although this covers a wide range of common use cases, the team sees future work expanding the software to support more complex and dynamic loading conditions. The team also sees potential in using AI to infer the object’s intended use based on its geometry, which could allow for fully automated stress modeling without manual input of forces or boundaries.

3D for free

The researchers plan to release SustainaPrint as an open-source project, making both the software and testing tool kit available for public use and modification.

Another initiative they aspire to bring to life in the future is education. “In a classroom, SustainaPrint isn’t just a tool, it’s a way to teach students about material science, structural engineering, and sustainable design, all in one project,” says Perroni-Scharf. “It turns these abstract concepts into something tangible.”

As 3D printing becomes increasingly embedded in the manufacturing and prototyping of everything from consumer goods to emergency equipment, sustainability concerns will only intensify. With tools like SustainaPrint, those concerns no longer need to come at the expense of performance. Instead, they can become part of the design process, built into the very geometry of the things we make.

Co-author Patrick Baudisch, a professor at the Hasso Plattner Institute, says, “The project addresses a key question: What is the point of collecting material for recycling when there is no plan to actually ever use that material? Maxine presents the missing link between the theoretical/abstract idea of 3D-printing material recycling and what it actually takes to make this idea relevant.”

Perroni-Scharf and Baudisch wrote the paper with CSAIL research assistant Jennifer Xiao; MIT Department of Electrical Engineering and Computer Science master’s student Cole Paulin; master’s student Ray Wang and Ph.D. student Ticha Sethapakdi (both CSAIL members); Hasso Plattner Institute Ph.D. student Muhammad Abdullah; and associate professor Stefanie Mueller, lead of the Human-Computer Interaction Engineering Group at CSAIL.

The researchers’ work was supported by a Designing for Sustainability Grant from the Designing for Sustainability MIT-HPI Research Program. 

A new software and hardware tool kit called SustainaPrint can help users strategically combine strong and weak filaments to achieve the best of both worlds. Instead of printing an entire object with high-performance plastic, the system analyzes a model, predicts where the object is most likely to be stressed, and reinforces those zones with stronger material. Image credit: Alex Shipps/MIT CSAIL, using assets from Pixabay and the researchers.