Thermal Shocks Can Erase Memory in Jammed Materials, Boosting Drug Delivery

Scientists at the Raman Research Institute (RRI), Bengaluru, have demonstrated a method to temporarily transform jammed, glass-like materials into a flowing state using sudden temperature changes. This process erases the material's structural memory, offering new possibilities for controlled drug delivery and other applications.

Materials like glass behave mechanically as solids but possess a disordered, liquid-like internal structure. They also retain imprints of their thermal and mechanical history. The RRI team, including PhD student Sonali Kawale and Professor Ranjini Bandyopadhyay, sought ways to erase these imprints by momentarily returning the material to a liquid state.

For their experiments, the researchers used microgels—soft, squishy particles capable of absorbing hundreds of times their weight in water. These particles were densely packed to mimic the disordered state of glass. The team subjected the suspension to controlled temperature changes and observed that the path taken during heating differed from that during cooling, a phenomenon known as asymmetry.

Crucially, they found that applying a sudden, sharp temperature increase—a thermal shock—caused the particles to rearrange, sending the jammed system into a temporary liquid state. This rearrangement erased the memory of the different thermal paths and reduced the asymmetric relaxations within the system. This ability to control and eliminate asymmetries is a significant advance.

The findings have direct implications for drug delivery. Microgel particles are already used to encapsulate drugs, swelling when cool and collapsing at body temperature to release their payload at a targeted site. Understanding how thermal shocks influence structural recovery is therefore vital for designing more effective, controlled-release systems.

The study was published in the Journal of Colloid and Interface Science. Future research will explore how mechanical shocks, as opposed to thermal ones, affect the path-dependent dynamics of these jammed systems.