Fabrication of Hierarchically Structured Free‐Standing Supramolecular Hydrogels through Flow‐Driven Reaction‐Diffusion

ABSTRACT Supramolecular hydrogels self‐assembled by small molecular gelators have been recognized as a class of important soft materials. To realize their full potential, the structuring of supramolecular hydrogels at different length scales is required, yet remains a grand challenge. Here, we describe a simple flow‐driven reaction‐diffusion approach for the fabrication of hierarchically structured free‐standing supramolecular hydrogels. The fabrication system comprises a flow channel made by agarose matrix that allows proton solutions to flow inside. Over time, the flowing protons diffuse across the channel wall, thereby triggering the self‐assembly of acid‐sensitive gelators at the channel surface. More interestingly, by adjusting the proton concentration, the self‐assembled hydrogel fibers can be directed to grow along the diffusion direction. As a result, free‐standing hydrogel tubes with aligned hydrogel fibers and different cross‐section shapes are produced. Furthermore, upon a sequential growth of different supramolecular hydrogels at the channel surface, multilayered supramolecular hydrogel tubes can be created. Such a simple flow‐driven reaction‐diffusion approach for the structuring of supramolecular hydrogels at the levels of both fibers and macroscopic hydrogels may further unlock more functions and applications of supramolecular hydrogels.