Light-programmable photoredox colloids for reconfigurable assemblies

The dynamic self-assembly of colloids under non-equilibrium conditions offers a pathway to reconfigurable materials and adaptive soft systems, yet current approaches often require particle anisotropy, ultraviolet activation, or multiple external fields. Here, we introduce a modular class of photoactive colloids that self-organize into user-defined architectures under visible light alone. These colloids consist of a poly(phosphazene-phloroglucinol) matrix embedding the [Ru(bpy)3]2+ complex, which provides long-lived excited states with efficient redox cycling. Under blue illumination, the colloids generate localized proton gradients that induce phoretic attraction and reversible crystallization, producing ordered domains whose geometry, density, and dimensionality are dictated entirely by structured light fields. Minimal reaction–diffusion simulations that incorporate the rele vant phoretic interactions reproduce the observed behaviors, establishing a mechanistic distinction from optical trapping and other force-based approaches. These findings establish photoredox colloids as optically programmable building blocks for dynamic and reconfigurable materials that bridge photochemistry, soft matter, and artificial self-assembly.