Particle suspensions were prepared by diluting 5 μm internally green dyed fluorescent polystyrene microspheres (coefficient of variation (CV) < 5%, ThermoFisher Scientific, Waltham, MA, USA), and 13 μm internally red dyed fluorescent polystyrene microspheres (CV < 5%, Thermo Fisher Scientific) in deionized (DI) water containing 0.01% (v/v) Tween 20 (Sigma-Aldrich, San Antonio, TX, USA). Tween 20 was included in suspension to prevent particle aggregation. Before commencing each experiment, the particle solutions were re-suspended by vortex to provide uniform suspensions.
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