### Nicholas Boffi

Harvard University

Nicholas Boffi was interested in physics before he knew exactly what to call it. As a first grader, he played with rubber lacrosse balls near his rural Connecticut home, trying to understand how high they would bounce and how his hand could alter the ball’s force and acceleration. In high school, he explored advanced math and learned physics equations that express the ball’s motion. He first tried programming by adding new features to computer games.

Boffi carried those early interests into Northwestern University’s integrated science program, an undergraduate interdisciplinary track that allowed him to take courses in math, physics, chemistry and biology. A course in nonlinear dynamical systems – complex, often chaotic, processes that are difficult to model accurately – laid important groundwork for Boffi’s future interests.

At the time his math and science interests seemed like puzzle pieces that didn’t fit. “I knew I loved dynamical systems, and I wanted to do computation. But I didn’t see how I could do computation in dynamical systems,” he says.

Boffi built on an undergraduate research project in theoretical quantum chemistry to land a Fulbright fellowship in Israel after he graduated in 2014. Though he had never traveled outside the United States and didn’t speak Hebrew, Boffi was soon taking courses at Tel Aviv University and pursuing computational quantum mechanics research.

But his interest in that subject was waning. During a meeting with his Israeli advisor, Amir Natan, Boffi asked about a set of equations on the office chalkboard. Natan explained that they related to a stalled project, an effort to develop more rigorous, numerical algorithms to improve the accuracy of chemistry simulations. Boffi soon switched to that project. “I’d never had a chance to explore numerical algorithms for their own sake,” he says.

The experience prompted Boffi to pursue a Ph.D. in applied mathematics instead of physics. He headed to Harvard University in 2015, supported by a Department of Energy Computational Science Graduate Fellowship (DOE CSGF).

Boffi chose to work with Chris Rycroft on soft-matter physics, modeling novel materials known as bulk metallic glasses (BMGs), amorphous metals that are moldable like plastics. BMGs show amazing strength, similar to titanium, making them promising materials for human joint replacements, cellphone cases and more. But they also have a puzzling flaw known as shear banding: when subjected to certain combinations of forces, BMGs can develop cracks and fail catastrophically.

Rycroft had developed high-performance computing tools to model BMGs in two dimensions and test new theory describing how and why they fail. Boffi has extended that work to the third dimension. Practically, their work could help engineers build things from BMGs. From a physics perspective, the materials provide “an excellent test case for any theory of plastic deformation in amorphous solids,” he adds.

“It’s a mathematical playground that allows us to test a physical theory by testing the properties of materials that have a lot of practical and engineering relevance,” Boffi says. He hopes to run larger BMG simulations in the near future on Titan, the Cray XK7 supercomputer at the Oak Ridge Leadership Computing Facility.

Boffi also has continued exploring dynamical systems. After his first year at Harvard, he did research with Jean-Jacques Slotine at the Massachusetts Institute of Technology. Working with Slotine, who now co-advises his Ph.D., Boffi has used mathematical tools in dynamical systems and control to better understand how artificial intelligence algorithms work and to develop new control methods.

These parallel research paths are now converging, allowing Boffi to unite his interests in ways that he couldn’t have imagined just five years ago. He hopes to begin using artificial intelligence algorithms he’s developed to extend the modeling work on BMGs and to understand complex nonlinear phenomena in other physical systems.

Control and dynamical systems problems also pop up in biology. During his 2017 practicum at Lawrence Berkeley National Laboratory, Boffi worked with synthetic biologist Adam Arkin on the theory of genetic control circuits. Arkin’s team is trying to develop bacterial cells that could act as drug delivery systems from within the human body, monitoring conditions to deliver just enough antibiotic to wipe out infections without harming beneficial bacteria. Boffi has helped the lab team develop dynamical systems models for constructing such cells and simulations to predict experimental data.

Boffi would like to stay in academia after completing his Ph.D. in 2021. He plans to continue his work on artificial intelligence algorithms and dynamical systems and collaborate closely with physicists or biologists on how to best use these tools in science.

**Image caption:** When bulk metallic glasses (BMGs) are subjected to sufficient shear forces, these superstrong, moldable materials can form cracks in a largely unexplained process known as shear banding. This snapshot comes from a three-dimensional computational model of shear banding in BMGs based on the shear transformation zone theory of amorphous plasticity. *Credit: Nicholas Boffi.*