Reconfiguration, Interrupted Aging, and Enhanced Dynamics of a Colloidal Gel Using Photoswitchable Active Doping

We study quasi-2D gels made of a colloidal network doped with Janus particles activated by light. Following the gel formation, we monitor both the structure and dynamics before, during, and after the activation period. Before activity is switched on, the gel is slowly aging. During the activation, the mobility of the passive particles exhibits a characteristic scale-dependent response, while the colloidal network remains connected, and the gel maintains its structural integrity. Once activity is switched off, the gel stops aging and keeps the memory of the structure inherited from the active phase. Remarkably, the motility remains larger than that of the gel, before the active period. The system has turned into a genuinely softer gel, with frozen dynamics, but with more space for thermal fluctuations. The above conclusions remain valid long after the activity period.

Automated summary

We study the behavior of quasi-2D gels comprised of a colloidal network doped with light-activated Janus particles. The gel ages slowly before the activation, and during the activation, the mobility of passive particles shows a scale-dependent response while the colloidal network remains connected. After activation, the gel retains its structure and becomes a softer gel with frozen dynamics and more space for thermal fluctuations. These conclusions remain valid long after the activity period.