Figure 4.
(a) Initial random distribution of 30 μm polystyrene particles in the central area at the droplet-substrate interface when the droplet volume and particle concentration are 15 μL and 0.20 mg/mL, respectively, (b) Aggregation of 30 μm polystyrene particles after 10 s of acoustic field with a 6 Vpp driving voltage and 112 kHz excitation frequency, (c) Fluorescent signal enhancement ratio versus driving voltage for 30 μm polystyrene particles, (d) Initial random distribution of 470 nm carboxyl magnetic particles in the central area at the droplet-substrate interface when the droplet volume and particle concentration are 15 μL and 0.10 mg/mL, respectively, (e) Aggregation of 470 nm carboxyl magnetic particles after 1 min of acoustic field with an 8 Vpp driving voltage and 112 kHz excitation frequency, (f) Fluorescent signal enhancement ratio versus driving voltage for 470 nm carboxyl magnetic particles. Scale bars: 500 μm.