UW-Madison Engineers Discover "Negative Viscosity" Propelling Cells
University of Wisconsin-Madison engineers have identified a groundbreaking phenomenon called "negative viscosity" that propels cells, directly challenging previous understanding of how cells move in groups. This significant discovery was made by Jacob Notbohm, an associate professor of mechanical engineering, and PhD student Molly McCord, and was published on December 4, 2025, in the prestigious journal PRX Life.
Understanding Negative Viscosity
Negative viscosity refers to a situation where, contrary to standard physical rules, resistance propels movement rather than impeding it. In biological systems, this implies an injection of energy into the flow of cells. Researchers observed that regions exhibiting negative viscosity showed elevated metabolic activity, indicating an increased energy demand as cells convert nutrients into energy to facilitate this unusual process.
Pioneering Measurement Techniques
The team developed a novel method to directly measure viscosity within cell groups. They conducted intricate experiments using optical imaging to analyze how a single layer of epithelial cells deformed a soft gel surface during migration. This innovative approach allowed them to precisely calculate the forces produced by the cells.
Analysis of the data, focusing on various multicellular regions, revealed the unexpected presence of negative viscosity in certain cell groups. This finding suggests that understanding collective cell motion requires considering both positive and negative viscosity.
Implications for Human Health
This pioneering research may significantly contribute to improved models for cell motion. Such advancements hold considerable potential applications in human health, including accelerating wound healing and supporting essential processes in tissue development.
Support for the Research
The work received crucial support from the National Science Foundation (grant no. CMMI-2205141) and the National Institutes of Health (grant no. R35GM151171).