Hagh brings design and training of disordered materials to MechSE

2/21/2024 Taylor Parks

New assistant professor Varda Hagh's research interests include the study of memory formation in materials, training of disordered materials for novel functionality, and design of bio-inspired metamaterials and reconfigurable and shape-shifting materials.

Written by Taylor Parks

Varda Hagh

Last fall, MechSE welcomed Assistant Professor Varda Hagh to its faculty community. Hagh, who primarily focuses on the physics of soft matter, completed their Ph.D. at Arizona State University and did their postdoctoral studies at the University of Chicago’s James Franck Institute.

“I heard from colleagues that the UIUC environment is very collaborative and interdisciplinary,” Hagh said of their interest in coming to Illinois. “The fact that the barriers for people to talk across disciplines are so low really got me excited and I could see myself collaborating with researchers from different departments.”

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Hagh uses models to demonstrate how changing the local structure in a network changes its rigidity.

Hagh’s research interests include the study of memory formation in materials, training of disordered materials for novel functionality, and design of bio-inspired metamaterials and reconfigurable and shape-shifting materials.

“I look at materials through a discrete lens that is independent of scale,” Hagh said of their interest in disordered materials. “Through this lens, the material’s geometrical configuration and local properties become fundamental determinants of its physical behavior.” This phenomenon becomes more prominent when the material does not have to adhere to a particularly ordered structure. “This type of disorder introduces a lot of possibilities for the material to exist in all sorts of configurations with locally varying properties that would each lead to different material behavior at the global scale,” they added.

Hagh’s postdoctoral research, which focused on investigating the disordered structural and dynamical properties of glasses and jammed packings of soft particles, set the stage for their current research.

“What I do is explore the enormous space of possibilities for disordered materials and manipulate their local properties in a systematic and algorithmic way to guide them to a state of being that’s unusual and extraordinary,” Hagh said.  

Diagram showing radii and sound training
From training packings of soft particles to training caterpillars: Hagh illustrates how training the configuration of consituent parts can lead to different global behavior. The images in the bottom panel are taken from an online video demonstrating the group response of Cape lappet caterpillars to human voice.

For instance, a piece of foam used for chair cushions has a positive Poisson’s ratio, meaning that when compressed longitudinally, it will expand transversely to preserve its volume. “However, by paying attention to the foam’s structure and viewing it as a mechanical network at the microscopic level, we encounter an opportunity for innovation,” Hagh said. By systematically adjusting and altering the network’s local properties, such as stiffness and the natural rest-lengths of the connections between constituent parts, the foam network can be “trained” to exhibit a negative Poisson’s ratio.

“This alteration in the foam’s behavior is extraordinary,” Hagh explained. “In its new state, the foam would contract transversely when compressed longitudinally, which is a departure from the normal response of ordinary foams. Such a transformation demonstrates not only the malleability of disordered materials under precise control, but also opens up new avenues for designing materials with tailored response for advanced applications.”

Although most of Hagh’s work has been theoretical and computational, they look forward to performing experiments in new areas in their research lab. “At the moment, I am very excited about exploring the relationship between physical configuration and structure of caterpillar colonies and the emergent group signals that they display in response to external stimuli. We are going to play tones of varying frequencies and observe groups of caterpillars change their dance moves as we rearrange them carefully into new group configurations in the colony.”

Hagh has set up a soft matter research lab to study soft materials from a variety of perspectives. Students who are interested in potential research opportunities should inquire at hagh@illinois.edu.

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This story was published February 21, 2024.