Fig. 1. Design of MSA building blocks and the challenge of self-sorting in macroscopic self-assembly.

a Schematic illustration of expanded polystyrene (EPS) building blocks with self-propulsive systems (catalyst of platinum, Pt), anisotropic wettability and magnetic plates. b Motion trajectory of one building block on the surface of H₂O₂ solution. Scale bar: 1 cm. c Snapshot photographs of A-B assembly driven by the capillary attraction at an air/water interface. Scale bars: 5 mm. d Interfacial electrostatic interaction between oppositely charged polyelectrolytes on A-B surfaces after capillary-driven assembly. e The problem of ‘isomers’ present in the assembly of trimers, and f a possible solution of directed assembly via resultant forces from the coupled magnetic ($F_{magnetic}$) and capillary ($F_{capillary}$) interactions. Source data are provided as a Source Data file.