Carlos Portela

d’Arbeloff Career Development Assistant Professor of Mechanical Engineering

Taking 3D architected materials out of the lab and into the real world

Taking 3D architected materials out of the lab and into the real world
material mechanics

Carlos Portela is the d’Arbeloff Career Development Assistant Professor in MIT’s Department of Mechanical Engineering. His research is focused on designing, fabricating, and testing 3D architected materials to address current societal and engineering challenges.

By: Daniel de Wolff

Carlos Portela and his research group at MIT study what could be categorized as the mechanics of materials. More specifically, they fabricate architected materials for which they have designed the microstructure or nanostructure a priori using computer models to understand their mechanical properties. These are new types of materials with customized behaviors based on the interplay between material properties and geometry. To date, architected materials have been primarily studied under a limited set of conditions consisting of static and small deformations—but little is known about their performance under extreme conditions found in the real world.

Portela wants to make architected materials available beyond laboratory settings, and he wants to do it at scale. “Today, architected materials—nanomaterials in general—are realized in small volumes. We want to make sure the fabrication of these materials can be scaled up. This is one of the key problems we are trying to solve in the Portela group.”

Portela arrived at MIT in 2020 to assume his role as an assistant professor in the Department of Mechanical Engineering, but he has been connected to the Institute since collaborating with the MIT Institute for Soldier Technology (ISN) during his graduate and postdoctoral days at Caltech.

Imagine ceramics with rubber-like flexibility or metals imbued with extreme toughness and fracture resistance.

Recently, the Portela group, in conjunction with researchers at MIT ISN, Caltech, and ETH Zürich, collaborated to create an ultralight, carbon-based material that is more efficient than Kevlar or steel at absorbing impacts. They tested the new material, which is designed from nanometer-scale carbon struts to be hundreds-of-times thinner than the width of a human hair, by accelerating 14-micron diameter glass spheres at the material at supersonic speeds and observing the impact in real time. The findings, published in Nature Materials, demonstrate the potential of the newly architected material for dissipating energy, opening up a host of potential industry applications—from helmets to bumpers; anything requiring a protective layer.

“Working at the nanoscale allows us to tap into these very interesting size effects—meaning these materials behave nothing like they would in bulk,” Portela explains. For example, if you knock your glass of water off a table from the right height, it shatters. But what if it didn't? Glass, classified by materials scientists as a ceramic, shatters easily because it is brittle, and like all materials, its physical and mechanical properties are an expression of its composition and structure. With nanoscale ceramics, glass could be designed to wrinkle and bend rather than shatter under typical circumstances—something Portela has demonstrated in his lab. Imagine ceramics with rubber-like flexibility or metals imbued with extreme toughness and fracture resistance.

But it isn’t just the nanoscale that provides the opportunity for developing new materials with novel properties and responses. Working at the microscale, Portela and collaborators are exploring how to reconfigure architected materials to have on-demand properties in real-time. In a recent study, they demonstrated that electrochemically altering the shape of three-dimensional architectures changes the way these materials respond to mechanical vibrations, which allows for the possibility of tuning mechanical waves in the megahertz regime, where medical ultrasound exists. In practical terms, this could provide the possibility of waveguiding ultrasound, meaning you could steer an ultrasonic pulse within the material either by designing the architecture correctly or tuning it in real-time.

He’s also rethinking the traditional approach to architecting materials. For years, periodic and symmetric architectures have been considered the way forward due to their stiffness and strength. But focusing on the stiff- -and-strong regime has led the field to overlook the opportunities presented in the soft materials side of things—it’s an untapped property space for architected materials. And these days, there is a growing demand for multifunctional, tunable soft materials. Think soft robotics, biomedical devices, or even tissue scaffolds.

By mixing a certain ratio of polymers in a beaker and allowing them to separate as they would naturally, Portela observed that they formed intricate, curved, three-dimensional morphologies that were asymmetric and aperiodic, unlike classically architected materials. He has, in essence, used this to develop a new paradigm for self-architecting lightweight materials that could eliminate reliance on expensive fabrication tools like nanoscale 3D printers, potentially solving what is considered one of the greatest challenges in architected materials: scalability. For the last decade, scientists working at the nanoscale have been able to demonstrate novel and interesting properties of architected materials, but only in small sample sizes.

Portela’s latest discovery might change that. “In principle, you could run this reaction in larger and larger volumes in a beaker, and the process will architect itself. It could be a game-changing achievement if it can be realized,” he says.

Industry challenges can help drive our research towards previously unexplored areas, and interacting with ILP members is a great way to discover potential problems that we could be addressing.

Architected materials open up the parameter space for designing new materials that could be critical to addressing current and future challenges in the healthcare, energy, and supercomputing sectors. And pioneering researchers like Carlos Portela are at the forefront of finding pathways to enabling and understanding nano-architected materials. As he sees it, the MIT Industrial Liaison Program plays an essential role in strengthening the relationship between academia and industry and advancing progress in the field. “We want our materials to have real-world applications,” says Portela. “Industry challenges can help drive our research towards previously unexplored areas, and interacting with ILP members is a great way to discover potential problems that we could be addressing but haven't thought of quite yet.”

Carlos Portela
Carlos Portela, d’Arbeloff Career Development Assistant Professor, Department of Mechanical Engineering