Collective systems across length scales display order in their spatiotemporal patterns. These patterns contain information that correlates with their orders and reflects the system dynamics. Here we show the collective patterns and behaviors of up to 250 micro-rafts spinning at the air-water interface and demonstrate the link between order and information in the collective motion. These micro-rafts display a rich variety of collective behaviors that resemble thermodynamic equilibrium phases such as gases, hexatics, and crystals. Moreover, owing to the unique coupling of magnetic and fluidic forces, a number of collective properties and functions emerge as the micro-rafts interact with magnetic potential and nonmagnetic floating objects. Our findings are relevant for analyzing collective systems in nature and for designing collective robotic systems.
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