A team of engineers in the United States has discovered that ordinary liquids can snap apart like solids. Not bend, not thin out, not slowly drip away – snap. With a noise loud enough to startle the researcher running the experiment.
The finding overturns something scientists thought they understood about the most familiar substance in the world.
“The fracture caused a very loud snapping noise that actually startled me,” said Thamires Lima, an engineer at Drexel University in Philadelphia who led the research. “I thought at first the machine had broken, but soon realised that the noise came from the stretching fluid.”
The study was published in the journal Physical Review Letters.
What liquids are supposed to do
Ask any physics student what makes a liquid different from a solid and they will give you an answer that has held since the foundations of the subject were laid: solids break, liquids flow. Pull a piece of metal hard enough and it stretches until it snaps. Pull a liquid and it simply thins out – like honey stretching from a spoon – until it separates into droplets. That is not a break. It is just flowing in a new direction.
Lima and her colleagues were not trying to challenge this. They were running a standard test on a thick, tar-like hydrocarbon liquid for a project with ExxonMobil, measuring how much force it takes to stretch a liquid. The machine is called an extensional rheometer. It grips a sample and pulls it apart at a controlled speed.
What they got was not what they expected.
Instead of slowly thinning and parting, the liquid resisted – then fractured. Suddenly. With a crack.
“What we observed was so unexpected that we needed to repeat the experiments a few more times to make sure it was real,” said Nicolas Alvarez, the professor at Drexel whose lab led the research. “Once we confirmed the phenomenon, the research became an entirely different scientific endeavour.”
Why it happened
The key turned out to be speed. Liquids can only flow away from stress if given enough time to do so. Pull too quickly and the liquid cannot redistribute itself fast enough. Stress builds – exactly as it does in a solid – until something gives. The result is a brittle fracture: the same sudden failure seen when glass shatters or a metal rod breaks under tension.
The breaking point for the liquids tested was around 2 megapascals of tension – roughly the force you would feel if a bag of ten bricks caught on your fingernail as it fell.
The team repeated the test with a chemically different liquid adjusted to the same viscosity. It fractured at the same stretching rate. They also varied temperature to change each sample’s viscosity, and found the liquid broke at a stress level proportional to that same 2 megapascal threshold each time.
The conclusion: it is viscosity – a liquid’s resistance to flow – that controls whether it can snap. This means the effect may apply to any sufficiently thick liquid, regardless of its chemistry.
“This is likely true for all simple liquids, including common examples such as water and oil,” Lima said.
Why it matters
The implications reach well beyond the laboratory. Engineers who design hydraulic systems, fuel injectors, and industrial pumps all work with liquids under high-speed, high-force conditions. If those liquids can fracture, the calculations used to build those systems may need to be revised.
In medicine, blood is a liquid. Whether it can fracture under extreme conditions – in a damaged heart valve, for instance – is now an open question.
In manufacturing, 3D printing and fibre spinning both work by stretching liquid materials. A better understanding of when those liquids break rather than stretch could lead to stronger, more consistent products.
The research team says its next step is to pin down the precise mechanism. One hypothesis is cavitation – the formation and collapse of tiny vapour bubbles inside the liquid.
Sources
Thamires A. Lima, Nicolas J. Alvarez, Stuart E. Smith, Kazem V. Edmond, Manesh Gopinadhan, Emmanuel Ulysse. “Unexpected Solidlike Fracture in Simple Liquids.” Physical Review Letters, 136 (12), 26 March 2026. https://doi.org/10.1103/t2vy-32wr
Institutional press release Drexel University. “Drexel Researchers Discover Liquids Have a Breaking Point.” 28 March 2026. https://drexel.edu/news/archive/2026/March/liquid-breaking-point
Ray Jackson holds a BSc in Electrical Engineering from the University of Manitoba and a PhD in Physics from Carleton University. His reporting interests include Current and Future Technologies, Engineering and Artificial Intelligence.