Nickel-Assisted Dehydration of DNA-Engineered Colloidal Crystals

In colloidal crystal engineering, DNA has enabled precise control over crystal symmetry and architecture through programmable interparticle interactions in aqueous environments. However, practical applications typically require dry-state operation, necessitating robust strategies to transform these assemblies into free-standing solid-state metamaterials. As direct dehydration often induces structural collapse due to DNA deformation and capillary forces, the preservation of structural integrity becomes a critical challenge, particularly for large crystals with macroscopic functionality. Here, we introduce a nickel ion-assisted freeze-drying strategy that combines reversible Ni²⁺-DNA phosphate coordination for stress mitigation with lyophilization to reduce interfacial damage. This approach enables rapid fabrication (within 2 h) of solid-state colloidal crystals while maintaining hierarchical order from nanoscale to macroscale. Structural characterization confirms retention of crystallographic symmetry despite up to 45% lattice contraction, and surface analysis reveals multidimensional defects analogous to those in atomic crystals. Notably, this approach facilitates the fabrication of monolithic single crystals spanning tens of micrometers, featuring flat surfaces and enhanced metallic reflectivity. This work overcomes the rigidity-adaptability trade-off in existing processes, offering a scalable route to colloidal metamaterials for applications in photonic circuits and near-field optical devices.