Bio-Inspired Superhydrophilic Urchin-Like Supramolecular Structures Formed by Co-Assembly of Simple Metabolites

Abstract

Numerous natural surfaces exhibit unique wetting behaviors, typically attributed to a synergy between two-tier micro/nanoscale hierarchical structures and specific material chemistry. Replicating these surfaces is often challenging because it relies on harsh, complex synthesis methods for inorganic materials. As a versatile extension of traditional self-assembly, heterogeneous molecular assembly offers a programmable route toward complex hierarchical biomimicry. Here, we study the coassembly of two simple metabolites, riboflavin and 2,6-diaminopurine, to demonstrate this approach for constructing functional materials. We found that the co-assembled structures exhibit an urchin-like morphology and employed various characterization methods to investigate the interaction between the two metabolite building blocks. The co-assembled structures exhibit superhydrophilic characteristics that were not achieved with unimolecular components, underscoring the advantages of a co-assembled system. Although the unimolecular components are hydrophilic and possess surface hydrophilic groups, as demonstrated by X-ray photoelectron spectroscopy (XPS) analysis, this alone is insufficient to construct a superhydrophilic surface. This was confirmed by measuring the water contact angle (WCA) of the coated hydrophilic glass coverslip in contact with the co-assembled structures and the unimolecular components, which rendered the glass superhydrophilic. Inspired by the amphiphilic nature of the Namib desert beetle’s back used for water harvesting, we coated a hydrophobic surface with the co-assembled structures. This modification transformed the surface to superhydrophilic, highlighting the importance of surface texture in conjunction with surface chemistry in establishing superwetting behavior. This study provides important insights into the interplay between the coassembly of metabolite building blocks and functional materials and establishes an innovative yet simple design route for developing functional surfaces.