Materials
NdFeB particles (MQFP-B-20076-089) from Magnequench (China), Ecoflex 00-30 from Smooth-On Inc. (USA), hexane (CH3(CH2)4CH3, extra pure) from Ducksan (South Korea), glycerol (HOCH2CH(OH)CH2OH, 99%) from Thermo Fisher, and blue fluorescent polystyrene particles from Bead & Micro (South Korea) were purchased and used.