January 16, 2026
Maureen Searcy
UChicago biophysicists probe the mechanics of extremely thin films
Complex systems, such as human bodies or supercomputers, are made up of smaller systems, sometimes down to the thickness of a single atom or molecule. Understanding the behavior of small-scale systems, including extremely thin films, is essential for biology and medicine, technology, and fundamental knowledge of matter.
When you squeeze films that are one molecule thick, they react in a variety of ways to relieve the stress. For instance, they can buckle, but they may also relax while remaining flat. Yet exactly how and why such films relax rather than buckle is still a mystery.
A new study by a team of UChicago biophysicists investigated how thin films react to physical force. They developed a model to help predict how a material will behave based on its properties, and, through simulations, identified a specific mechanism key to relaxation.
An elastic framework
Lipid monolayers are thin films composed of a single layer of molecules with one hydrophilic and one hydrophobic side, like detergent, that spontaneously form between substances that don’t mix, like air and water. They serve various functions in living organisms, found in the ears, eyes, and lungs, and can be used to study biological membranes as well as self-organizing matter.
UChicago biophysicists used lipid monolayers to study the way thin films become unstable—by folding or relaxing—under compression.
The initial question was whether the researchers could create a model that mathematically captures the different modes of instability, to show when a material might buckle versus when it might relax and thereby identify an underlying mechanism.
To build such a model, they treated the film like an elastic sheet.
“Instead of looking at a lipid monolayer as a group of individual lipids, we look at it as if it is a homogenous material, like a rubber band,” said first author Anna Gaffney, PhD’26, a Biophysics graduate student in Ka Yee C. Lee’s Chemistry group and Luka Pocivavsek’s Surgery group at the time of this research. “Now the whole material responds in a certain way.”
The model was designed to input certain properties, such as stiffness, to control the outcome. When they ran simulations that ended in relaxation, the results revealed that it was triggered by a process called shear banding.
Shear banding is when localized areas of the film slide and shift to relieve the stress, leaving the other areas unaffected. Picture a crowded city bus with seated and standing riders arriving at a bus stop. The standing passengers pack in closer to clear the aisle while those seated remain in place.
The researchers validated these results by comparing the simulated shear band patterns to those seen in microscope images.
Medical and technological applications
The model described in this study shows that buckling and shear banding aren’t distinct phenomena—they are options for thin films with different material properties to relax their stress. But those are not the only ways films react to stress. For instance, a film can crack.
The mathematical framework Gaffney and her collaborators developed has the potential to unify all potential instability modes and provide the ability to predict which materials will react in which ways.
“The ability to really understand the mechanics of the system could help with creation of better, possibly cheaper, synthetic monolayers,” said Gaffney, who is now a postdoctoral fellow in the Department of Surgery with Nhung Nguyen. These could advance medical applications, such as improved synthetic lung surfactant—the layer of lipids and proteins crucial to lung function that premature babies often lack. Monolayers also play a role in technology, including flexible electronics, sensors, and energy storage.
The team’s next steps involve moving from two-dimensional modeling into the third dimension.
They currently have extensive data on how material responds in a single plane. They are now in the process of building a model that incorporates the material on which the monolayer rests. For instance, if the film is floating on a layer of water, that adds resistance, which is what allows folding to occur.
“We’re adding complexity to our model to see if we can produce the different responses,” said Gaffney. “We want to see how far we can push it.”
Citation: A.D. Gaffney, D. Liu, D. Samal, A.R. Carotenuto, L. Deseri, M. Fraldi, K.Y.C. Lee, L. Pocivavsek, & N. Nguyen, From relaxation to buckling: A continuum elastic framework connecting surface instabilities of highly compressed lipid thin films, Proc. Natl. Acad. Sci. U.S.A. 122 (36) e2502369122, (2025).
Funding: The National Science Foundation, the National Institutes of Health, and the Progetti di Rilevante Interesse Nazionale.