Bubble-Assisted Dynamic Confinement Enables Programmable Solid-State Photoswitching and Heterogeneous Photoresponsive Architectures.

Abstract

Achieving programmable photoisomerization of azobenzenes in the solid-state remains a long-standing challenge for photoresponsive materials. Here, we introduce a dynamic soft-confinement strategy using bubble-assisted assembly to manipulate molecular aggregation via tunable surface energy at the solid-liquid interface. By controlling the morphologies of microfluidic channels (necktie-like, strip-like, and necklace-like), we achieve distinct self-assembled aggregates of microcubes, corded scaffolds, and microplates, with tailored freedom of the photoswitchable molecule. The strip-like channel, formed by thinning bubble walls, traps metastable intermediates, yielding a corded scaffold structure with favorable light penetration, weaker intermolecular interactions, and loosened molecular packing for isomerization. This design achieves near-quantitative bidirectional E⇆Z photoisomerization (96%-98%) in the solid-state, rivaling solution-like performance. Multi-scale characterization and computational analyses reveal the critical role of confined aggregation kinetics in controlling molecular motion. Furthermore, heterogeneous patterning demonstrates programmable photoresponsive arrays for photomechanical applications. This strategy provides a scalable platform for dynamically controlling supramolecular self-assembly pathways and designing solid-state photoresponsive materials with programmable functions.