Spinnable hydrogel marbles: A dynamic miniature molecule concentrator for efficient water decontamination and colorimetric detection

The efficient accumulation of molecules from dilute solutions is crucial for facilitating pollutant decontamination, trace analyte detection, and chemical reactions. However, current methods to concentrate molecules are limited by prolonged processing times, high energy consumption, and a narrow range of applicable molecules. Herein, we introduce a magnetic-responsive spinnable hydrogel marble (SHM) as a miniature molecule concentrator for efficient water decontamination and sensing applications. The spinning motion of SHM creates a dynamic water-water interface within an aqueous environment, generating a vortex-like hydrodynamic flow that actively delivers molecules into the embedded hydrogel microdroplet. Notably, the SHM achieves a remarkable ∼95 % decontamination efficiency for cationic organic water pollutants in just 15 min while simultaneously concentrating molecules within SHM by ≥300-fold, a feat that remains challenging with conventional non-dynamic liquid interface. Moreover, the SHM also doubles as a versatile concentrator-cum-detection platform for ultrasensitive colorimetric sensing of organic pollutants in real wastewater at >99 % accuracy, thereby allowing the on-site readout of water chemistry using naked eyes or smartphone for prompt intervention. By enabling the efficient and swift concentration of molecules in an energy-efficient manner, our unique design effectively addresses the drawbacks of traditional approaches and creates enormous opportunities for diverse analytical, environmental, and chemical applications.