In a discovery that could reshape how scientists think about fluids, researchers at Drexel University have found that under certain conditions, a simple liquid can break apart like a solid. The study, published in Physical Review Letters, shows that viscous liquids can suddenly fracture when stretched with enough force.

This unexpected behavior points to viscosity, or a liquid’s resistance to flowing, as a key factor in how liquids respond to stress. It also suggests new ways liquids could be controlled in technologies ranging from hydraulics and 3D printing to biological systems like blood flow.

“Our findings show that if pulled apart with enough force per area, a simple liquid — a liquid that flows — will reach what we call a point of ‘critical stress,’ when it will actually fracture like a solid. And this is likely true for all simple liquids, including common examples, such as water and oil,” said Thamires Lima, PhD, an assistant research professor in Drexel’s College of Engineering, who helped to lead the research. “This fundamentally changes our understanding of fluid dynamics.”