From Molecular Complexity to Unified Laws: Rethinking Membrane Elasticity*

Cell membranes are remarkable adaptive materials, capable of responding to dietary and environmental cues through subtle changes in their molecular composition. Interactions between lipids and sterols—the principal membrane constituents and key design elements in biomimetic applications—play a central role in regulating emergent properties such as fluidity and elasticity. Yet, a consistent framework connecting compositional changes to membrane mechanics has remained elusive, largely due to contradictory observations across different measurement scales. In this talk, I will show that these contradictions resolve in the mesoscopic regime, between molecular and macroscopic dimensions. Using neutron spectroscopy in combination with computational analysis, we demonstrate that bending elasticity follows a unified scaling law with lipid packing density, independent of cholesterol content, lipid unsaturation, or temperature. This result shows that chemical complexity reduces to simple physical principles, in quantitative agreement with theoretical predictions based on chain conformational entropy and elastic stress fields. These findings establish predictive design rules for membrane mechanics and open pathways for engineering lipid-based materials in synthetic biology, biosensing, and therapeutic delivery.