What is it about?

Simple molecular liquids such as water or glycerol are of great importance for technical applications, in biology or for understanding properties in the liquid state. Upon deformation, Newtonian fluids like glycerol are expected to exhibit viscous behavior, and only when deformed on very short timescales, below the molecular diffusion time of a single molecule, is a solid-like elastic response expected. We have revealed a strong, rubber-like elasticity in the Newtonian fluid glycerol by analyzing the dynamics of a laser-driven free surface bubble. Not only do we find an elasticity persistent for four orders of magnitude longer than the diffusion time but also observe tolerance to large deformations only found in rubber-like materials.

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Why is it important?

We find an elasticity is persistent for microseconds, hence four orders of magnitude longer than the molecular diffusion time of a single glycerol molecule. Our observations are independent of surface tension and require the existence of a transient state with solid-like long-range correlations different from the liquid bulk state. This invites us to revisit our understanding of the liquid state. And could be likewise relevant in a technological or biological background where the timescales for this metastable state are potentially accessible and glycerol is a fundamental component.

Perspectives

The existence of such a rubber-like state in liquid glycerol raises the question: Are similar effects possible in other liquid substances? In particular the creation of elastic bubbles in water would be a major achievement because it is the most important and well-studied liquid with implications for multiple scientific fields.

Dr. Sascha W. Epp
Max-Planck-Gesellschaft zur Forderung der Wissenschaften

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This page is a summary of: Rubber-like elasticity in laser-driven free surface flow of a Newtonian fluid, Proceedings of the National Academy of Sciences, June 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2301956120.
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