Fabricating Shaped and Patterned Supramolecular Multi-Gelator Objects via Diffusion-Adhesion Gel Assembly

We report the use of acid-diffusion to assemble core-shell supramolecular gel beads with different low-molecular-weight gelators (LMWGs) in the core and shell. These gel beads grow a shell of dibenzylidenesorbitol-based DBS-COOH onto a core comprising DBS-CONHNH2 and agarose that has been loaded with acetic acid. Diffusion of the acid from the core triggers shell assembly. The presence of DBS-CONHNH2 enables the gel core to be loaded with metal nanoparticles (NPs) as the acyl hydrazide reduces metal salts in situ. The pH-responsiveness of DBS-COOH allows responsive assembly of the shell with both temporal and spatial control. By fixing multiple gel beads in a petri dish, the cores become linked to one another by the as-sembled DBS-COOH gel shell – a process we describe as diffusion-adhesion assembly. By controlling the geometry of the beads with respect to one another, it is possible to pattern the structures, and using a layer-by-layer approach, 3D objects can be fabricated. If some of the beads are loaded with basic DBS-carboxylate instead of CH3COOH, they act as a ‘sink’ for diffusing protons, preventing DBS-COOH shell assembly in the close proximity. Those beads do not adhere to the remainder of the growing gel object and can be simply removed once diffusion-assembly is complete, acting as templates, and enabling the fabrication of 3D ‘imprinted’ multi-gel architectures. Pre-loading the gel beads with AuNPs or AgNPs suspends these func-tional units within the cores at precisely-defined locations within a wider gel object. In summary, this approach enables the fabrication of shaped and patterned gels with embedded metal NPs – such objects have potential next-generation applica-tions in areas including soft nanoelectronics and regenerative medicine.