Mimicking Cacti Spines via Hierarchical Self-Assembly for Water Collection and Unidirectional Transport

Nature utilizes bottom-up approaches to fabricate defined structures with highly complex, anisotropic and functional features. One prominent example is cacti spines, which exhibit a hierarchically structured conical morphology with a longitudinal microstructured surface. Here, a bottom-up approach to fabricate supramolecular microstructured spines is presented by applying a self-assembly protocol. Taking advantage of the capillary forces of vertically aligned polyamide microfibers acts as the structure-directing substrate for site-specific self-assembly of a specific 1,3,5-benzenetricarboxamides from the solution. The morphology of the supramolecular spines covers several hierarchical levels, ultimately resulting in a conical shape with longitudinal self-assembled microgrooves and a superhydrophilic surface. It is demonstrated that these hierarchical conical microstructures are able to transport water droplets unidirectionally.