Fig. 1. Schematic of preparation of DPS shells.

Fig. 2. Diameter measurement of the W1/O compound droplet.

Fig. 3. Stability of W1/O compound droplets prepared by DPS-C: (a) t = t_o, and (b) t = t_o + 10 min.

Fig. 4. TG curves of different DPSs.

Fig. 5. Pyrolysis products of DPS-1 and DPS-C at 500 ^oC: (a) GC plot of DPS-1, (b) GC plot of DPS-C, (c) MS plot for t = 4.5 min, and (d) MS plot for t = 5.8 min.

Fig. 6. Microphotographs of W1/O compound droplets prepared by different methods: (a) mechanical agitation and (b) microfluidic technique.

Fig. 7. Size distributions of DPS shells prepared by microfluidic technique: (a) diameter, and (b) wall thickness.

Fig. 8. Microphotographs of DPS shells of different sizes prepared by different methods: (a) ∼ 100 μm–500 μm diameter, ∼10 μm wall thickness (traditional method), (b) 320 μm diameter, 20 μm wall thickness (microfluidic technique), (c) 1500 μm diameter, 30 μm wall thickness (microfluidic technique), and (d) 2450 μm diameter, 35 μm wall thickness (microfluidic technique).

Fig. 9. Effect of purification on the surface finish of DPS-C shells: (a) before purification, and (b) after purification.

Fig. 10. Surface microphotographs of DPS-3 shells prepared from different W2 phases: (a) 2.0% PVA + 0.5% CaCl₂ and (b) 2.0% PVA + 2.0% CaCl₂.

Fig. 11. Defects of dried DPS shells: (a) deflation, (b) crazes, (c) cracks, and (d) crazes and cracks.