Reconfiguration, Interrupted Aging and Enhanced Dynamics of a Colloidal Gel using Photo-Switchable Active Doping

TL;DR

This study investigates light-activated colloidal gels doped with Janus particles, revealing how light induces large-scale reorganization and alters the gel's dynamics, structure, and memory, resulting in a gel with enhanced fluctuations and frozen dynamics.

Contribution

It demonstrates how photo-switchable active doping can control gel reconfiguration, aging, and dynamics, introducing a new method to tune colloidal gel properties with light.

Findings

Light activation causes large-scale gel reorganization.

Post-activation, the gel retains altered dynamics and structure.

The gel maintains its integrity and memory after light is turned off.

Abstract

We study light-activated quasi-2d gels made of a colloidal network doped with Janus particles. Following the gel formation, the internal dynamics of the gel are monitored before, during, and after the light activation. We monitor both the structure and dynamics, before, during and after the illumination period. The mobility of the passive particles exhibits a characteristic scale-dependent response. Immediately following light activation, the gel displays large-scale reorganization, followed by progressive, short-scale displacements throughout the activation period. Albeit subtle structural changes (including pore opening and widening and shortening of strands) the colloidal network remains connected, and the gel maintains its structural integrity. Once activity is switched off, the gel 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 different gel, with frozen dynamics, but with more space for thermal fluctuations. The above conclusions remain valid long after the activity period.