#fluid dynamics

Ferrofluid - a magnetic colloidal liquid made of suspended iron molecules - guided in real time by a magnet. Recorded via a macro set up at 15 mm.

Scientists stretched a liquid and it snapped like a solid

Under extreme stress, even ordinary liquids can snap like solids—rewriting the rules of fluid physics.

In a surprising discovery that could reshape fluid mechanics, researchers at Drexel University have shown that under certain conditions, a simple liquid can behave like a solid and fracture. The study, published in Physical Review Letters, demonstrates that viscous liquids can abruptly snap when stretched with enough force. This finding suggests that viscosity, or a liquid's resistance to flow, plays a much larger role in its mechanical behavior than scientists previously believed. It also opens the door to new ways of controlling liquids in applications ranging from hydraulics and 3D printing to blood flow in the body. "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."