Printable meta-assemblies enable synergetic colouration

a, Schematic of the fabrication of topological DCPCs by combining inkjet printing with substrate wettability design. b, As-fabricated topological DCPCs controlled by the hydrophilic pins, including the schematics of the designed topological DCPCs (the red dots represent the designed hydrophilic pins), scanning electron microscopy images and bright-field microscopy images of the fabricated topological DCPCs. c, Characterizations of the topological meta-assemblies, including the schematics as well as the bright-field and polarization optical microscopy images of the topological meta-assemblies. On a substrate with homogeneous wettability, microdroplets assume an isotropic circular morphology owing to the surface tension effect, requiring to break the wettability symmetry. Thus, we fabricated the substrate composed of hydrophobic regions and hydrophilic pins. When the ink droplet is printed on the patterned surface, asymmetric dewetting can be triggered, driving the nanoparticles to self-assemble into topological DCPCs. By controlling the pin number and spatial distribution, the DCPC configurations can be designed. Thus, the topological meta-assemblies ranging from circular to octagonal can be precisely fabricated.