Hierarchical Tubular Structures Grown from the Gel/Liquid Interface

Abstract

Three dimensional hierarchical materials are widespread in nature but are difficult to synthesize by using self-assembly/organization. Here, we employ a gel-liquid interface to obtain centimeter-long ∼100 μm diameter tubes with complex mineral wall structures that grow from the interface into solution. The gel, made from gelatin, is loaded with metal chloride salt, whereas the solution is a high pH anion source. Tubes were obtained with a range of cations (Ca(2+) , Sr(2+) , Ba(2+) , Cu(2+) , and Zn(2+) ) and anions (CO3 (2-) and PO4 (3-) ). The crystalline phases found in the tube walls corresponded to expectations from solution chemistries and phase solubilities. The growth mechanism is found to be akin to that of chemical gardens. The divalent cations modify the strength of the gelatin gel in a manner that involves not only simple electrostatic screening, but also ion-specific effects. Thus, tubes were not obtained for those ions and/or concentrations that significantly changed the gel's mechanical structure. At high Cu(2+) loading, for example, vertical convection bands, not Liesegang bands, were observed in the gels.

Tubular Structures of Calcium Carbonate: Formation, Characterization, and Implications in Natural Mineral Environments

“…Several previous studies have reported the formation and ex situ characterization of calcium carbonate-based tubular structures synthesized by immersion of Ca 2 + -containing salts pellets in Na 2 CO 3 solutions, [13,26,27] or by growth on cationexchange membranes [38,39] and gel/liquid interfaces. [40] However, dynamic diffusion and precipitation processes occurring during the growth and subsequent ripening have not been studied yet in this system. In the present work, we have applied the approaches previously developed for silica gardens [3,10] to monitor time-dependent chemical gradients across tubular CaCO 3 membranes.…”

Chemobrionic structures in tissue engineering: self-assembling calcium phosphate tubes as cellular scaffolds

“…For instance, precipitate self-assembly can also be made to occur at the interface between cation loaded hydrogels and anionic solutions. 12,13 These systems have also been adapted to accommodate the growth of mineral at non-planar surfaces, such as gel spheres encapsulated with reactant ions. 14,15 Alternatively, the controlled injection of a cationic solution into an anionic reservoir (and vice versa), can provide unique insights into growth regimes during self-assembly and offer greater influence over precipitate composition.…”

Bio-inspired flow-driven chitosan chemical gardens

“…28 In the emerging field of chemobrionics, 21,29 where the spatiotemporal growth of chemical structures are addressed, experimental work on chemical gardens involves reactions of metallic cations most with the use of inorganic materials. [22][23][24][30][31][32][33][34] However, pure organic/hydrogel garden-like structures are still not investigated. The extension from inorganic to organic garden formations is always a challenge for the researchers, and the complete understanding of the underlying mechanism behind these formations is not fully resolved.…”