Active Particles Enhance Glass Strength by Reducing Brittleness

Researchers from the Tata Institute of Fundamental Research (TIFR) in Hyderabad and Heinrich Heine University (HHU) in Düsseldorf have developed a theoretical framework to reduce the brittleness of stable glasses. The study, led by Rashmi Priya and Smarajit Karmakar, suggests that incorporating self-propelled particles into glass can significantly enhance its strength by altering its failure mechanism.

Stable glasses, known for their high strength, often fail catastrophically when stressed beyond their limits due to their brittleness. This brittleness arises because damage is concentrated into a single shear band, leading to sudden failure. The team proposes that by introducing self-propelled particles, which move randomly, the stress distribution changes, allowing the glass to bear higher loads and fail more gradually.

The researchers used simulations to demonstrate that active particles, which carry their own fuel and move like bacteria or synthetic colloids, can transform the stress-strain curve of glass. Instead of a sharp drop in stress, the curve becomes more gradual, indicating a spread of deformation across multiple bands rather than a single plane. This change is attributed to the interaction between the shear forces and the active particles' motion.

The study highlights that the persistence time of the active particles—how long they move in one direction before changing course—plays a crucial role in this process. Short persistence times cause the particles to strengthen the glass by creating a network of shear bands, while longer times can lead to easier deformation.

While the findings are currently theoretical, the researchers aim to test them experimentally using dense colloidal systems with photoswitchable active particles. This research not only offers a new way to enhance glass strength but also connects the fields of active matter and disordered solid mechanics.