A Conversation Across Disciplines
A decades-long collaboration between two scientists at the Department of Energy's Oak Ridge National Laboratory is reshaping how we understand learning. John Katsaras, a neutron scattering scientist at ORNL's Spallation Neutron Source, and Pat Collier, a cleanroom process engineer at ORNL's Center for Nanophase Materials Sciences, have shown that cellular membranes play a direct role in how memory and learning form in the brain.
"Science is a conversation," said Katsaras. "Many years ago, Pat and I wanted to see what would happen when we combined our scientific interests. He wanted to explore soft matter systems for neuromorphic computing, and I've studied the structure and dynamics of lipid membranes over the past 40 years. We are now applying decades of our soft matter experience to a problem neither one of us would have imagined pursuing five years ago."
The work aims to advance materials science for neuromorphic, or low-power, brain-inspired computing technologies and research on neurological disorders. According to the scientists, the discovery was made possible by ORNL's unique combination of expertise in soft matter science, world-leading neutron capabilities, and co-located user facilities, which allowed researchers to investigate biological membranes in ways not previously possible.
From Droplets to Memory States
The researchers' early experiments used a droplet interface bilayer—water droplets suspended in oil—as a simple model of a cell membrane. These experiments produced unexpected electrical data that helped redirect the research toward neuron membranes involved in memory and learning.
"Our early measurements revealed stable changes in the membrane's electrical behavior—patterns typically associated with neural activity," said Collier.
Over the last five years, the team has built a growing body of evidence. In 2022, they demonstrated that lipid bilayers can mimic key features of long-term memory. More recently, they showed that electrical and mechanical cues can restructure bilayers in ways that support distinct, stable memory states, and they identified mechanisms that allow those states to persist.
Collier described the phenomenon in concrete terms: "In one region of a membrane, a lipid bilayer might rearrange to form a memory resistor, and in another region, it can behave as a memory capacitor. These properties could accelerate the development of new classes of soft materials capable of enhanced, highly versatile neural sensing and computing."
Working with a broad group of collaborators, the researchers developed new experimental approaches and observed results consistent with biological memory and learning occurring in these bilayers, according to Collier.
Implications for Neuromorphic Computing and Neurological Research
The research extends beyond basic membrane physics. Katsaras and Collier have shown that lipid bilayers play an active role in regulating how ions flow through membrane proteins. In upcoming experiments, the team plans to use neutron scattering and lithium to demonstrate how molecules within these membranes rearrange to increase or decrease the flow of potassium ions.
Lithium is widely used to treat bipolar disorder and has been studied for potential neuroprotective effects in neurodegenerative diseases, including Alzheimer's disease. Neutron scattering offers direct, nondestructive, atomic-scale measurements of how lipid bilayers alter the environment surrounding membrane proteins.
The team has also collaborated with researchers at Louisiana State University on rotaxanes—tiny molecular machines that change shape under light and act as molecular switches. Experiments showed that light-triggered changes in rotaxanes can drive membranes to reorganize between memory and learning.
In addition, the scientists have worked closely with researchers at the Oak Ridge Leadership Computing Facility, which hosts Frontier, the world's first exascale supercomputer, to support their research.
The significance of the work is highlighted by ORNL leadership. "This research highlights how ORNL's world-leading expertise in soft matter, advanced characterization and user facilities is enabling discoveries at the intersection of biology, materials science and computing," said Jon Taylor, associate laboratory director for Neutron Sciences at ORNL. "These findings support the lab's mission of translating fundamental science into technologies that address national priorities."