Scientists decode century-old puzzle behind glass-like materials
Baku, April 30, AZERTAC
A century-old physics mystery is moving closer to resolution as new research sheds new light on how liquids transform into rigid, glass-like solids without any obvious change in structure, according to TPS-IL. The findings could impact food production, gels, cement, even medicine.
The phenomenon, known as “glass transition,” affects many everyday and industrial materials, from food products to paints and gels, but it has been difficult to predict exactly when a flowing liquid will suddenly stiffen. It has puzzled scientists for more than 100 years because materials can become solid-like in appearance but remain almost unchanged at the microscopic level.
A team of Israeli and German scientists has introduced a new experimental method for observing the transition by tracking tiny particles embedded in the material. The study, conducted by Prof. Haim Diamant and Prof. Yael Roichman of Tel Aviv University’s School of Chemistry, in collaboration with Prof. Stefan Egelhaaf’s group at Heinrich Heine University Düsseldorf, was published in the peer-reviewed Nature Physics.
“The significance of this research lies not only in identifying new signatures of the glass transition, but also in offering a fresh perspective on the phenomenon as a whole,” Diamant said. “Our findings show that the glass transition is not merely a gradual slowing of particle motion, but is accompanied by a profound change in the way momentum is transmitted from point to point within the material.”
The researchers used colloids — liquids filled with microscopic particles — as a model system. Colloids are mixtures where tiny solid particles are suspended in a liquid, allowing the material to flow like a liquid while behaving in complex ways depending on how densely the particles are packed. As the particle density increases, the system becomes crowded until it “jams” and behaves like a solid.
The key innovation was adding very small tracer particles that remain mobile even when the surrounding material slows dramatically. By tracking pairs of these tracers with advanced microscopy, the scientists were able to measure how motion and forces spread through the system in real time.
The results showed a clear shift in how the material behaved. In a liquid, motion spreads over long distances through the system. As it approaches the glassy state, this propagation breaks down, and the material begins to behave more like a solid that absorbs momentum rather than transmitting it.
The study identified three clear signatures of this transition. First, a change in how spatial correlations decay with distance. Second, the emergence of a growing characteristic length scale linked to increasing viscosity. Third, the appearance of opposing motions between neighboring particles, showing the development of resistance to shear, a key property of solids.
Beyond fundamental physics, the method has important practical applications. It could help improve the design and processing of gels, paints, food products, and industrial materials such as cement and ceramic suspensions. Many of these systems can suddenly shift from flowing smoothly to clogging or solidifying, creating major challenges in manufacturing. The new approach offers a way to better predict and control these transitions, improving stability, texture, and performance.
The technique may also benefit biology and medicine, where tissues, blood, and cellular environments often behave like materials that are partly liquid and partly solid. Understanding when and how these systems stiffen could improve research into wound healing, disease progression, and drug delivery systems that rely on controlled changes in material consistency inside the body.
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