Researchers Discover Liquids Can Snap Like Solids

A team of researchers from Drexel University and ExxonMobil has made a significant discovery in fluid mechanics, revealing that simple liquids can fracture under stress, behaving similarly to solids. This finding challenges existing understandings of liquid behavior and has implications for various applications, including 3D printing and biological systems. The researchers conducted experiments to observe how viscous liquids respond to strong forces, leading to the unexpected observation of liquids snapping when subjected to sufficient stress.

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The experiments involved placing liquids between two metal plates and applying various forces while observing the results with a high-speed camera. The initial snapping event occurred when a tar-like hydrocarbon blend liquid was pulled with a force comparable to that of a bag of bricks suspended from a small area. This phenomenon was later confirmed in another viscous liquid, styrene oligomer. The researchers noted that thicker liquids could crack even when pulled slowly, although the force required remained consistent across different viscosities.

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Chemical engineer Thamires Lima stated, "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." This discovery suggests that the phenomenon may apply to a broader range of liquids, including common substances like water and oil.

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The researchers observed that once the cracking began, it occurred rapidly, at speeds between 500 and 1,500 meters per second. This rapid fracture aligns with the theory of cavitation, where sufficient stress creates tiny vacuum bubbles within the liquid, facilitating its rupture. The speed of the fracture presents challenges for further observation, but it opens avenues for additional research into how these fractures occur in various liquids and under different conditions.

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The implications of this discovery extend to practical applications such as inkjet printing and soft robotics. The researchers emphasize the importance of understanding the mechanics behind this behavior and how it manifests in other liquids. Lima noted, "Now that we have reported this unanticipated behavior, the work of fully understanding why it happens and how the behavior manifests in other liquids is an important next step."

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The research has been published in the journal *Physical Review Letters*, marking a pivotal moment in the study of liquid mechanics. The team is eager to explore further how these findings can be applied to assist in processes like fiber spinning and other applications involving viscous liquids.

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• "The fracture caused a very loud snapping noise that actually startled me." — Thamires Lima, Chemical Engineer, Drexel University

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• "What we observed was so unexpected." — Nicolas Alvarez, Chemical Engineer, Drexel University

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• "It will also be interesting to see how this finding may be applied to assist fiber spinning and other applications that use viscous liquids." — Thamires Lima, Chemical Engineer, Drexel University

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This groundbreaking research not only enhances the understanding of liquid behavior but also sets the stage for future innovations in various scientific and industrial fields.

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