When Materials Break: How Heat and Randomness Shape the Fate of Cracks and Adhesion.

Why do some materials hold strong while others suddenly crack or peel apart? This seemingly simple question hides a world of complex physics, where heat and randomness often call the shots.

Two recent scientific studies shed light on this mystery, showing that thermal fluctuations — the tiny, random movements of atoms caused by heat — can play a crucial role in how and when materials fail. These works were carried out as part of Claudia Binetti’s doctoral thesis, supervised by Stefano Giordano at IEMN, and by Giuseppe Puglisi (DICATECh, Bari) and Nicola M. Pugno (Dicam, Trento) on the Italian side.

In the first study, the focus is on adhesion — the subtle force that keeps surfaces stuck together. Think of how a gecko walks on the ceiling, or why a sticky note stays in place. The researchers built a mathematical model that links the microscopic forces between molecules to the larger-scale behavior of materials. Surprisingly, they found that even small temperature changes can cause a sudden loss of adhesion, just like how glue sometimes fails when it gets too warm.

The second study dives into fracture — how cracks start and spread. Conventional wisdom says that materials break when the stress becomes too great. But this work shows that cracks can nucleate much earlier, triggered by seemingly harmless thermal vibrations. Once started, a crack can grow in unexpected ways, driven by random fluctuations that are usually ignored

What ties these two studies together is a multiscale approach — a theoretical framework that connects the unpredictable world of atoms to the visible properties of real-world materials. In both cases, the researchers observed phase transitions: abrupt shifts from one state to another (like sticking to unsticking, or unbroken to cracked), caused not just by force but by randomness amplified by temperature. These transitions help explain how materials can switch behavior suddenly, even under mild conditions.