Figure 4.

(a) Photomicrograph of an individual droplet formed in the microfluidic device approximately10 s after the start of the reaction. The droplet contents were formed by combination of 4 mM CaCl₂ and Na₂CO₃ solutions, and a single rhombohedral calcite particle can clearly be seen within the droplet. (b) SEM micrograph of CaCO₃ particles isolated from microdroplets formed by combination of 4 mM CaCl₂ and Na₂CO₃ solutions. Only rhombohedral crystals between 1 and 2 μm in size were obtained. The inset shows an individual particle at higher magnification. (c) Raman spectrum of one of the crystals shown in (b).