Fig. 4. Preparation and typical images of multicompartment capsules (MCCs). (a) Preparation of MCCs by the same water–gas microfluidic method described in Fig. 2. A suspension of preformed capsules in an alginate solution is used as the liquid feed through the capillary. Gas pulses are used to dislodge uniform droplets from the tip of the capillary, and the droplets are then introduced into the reservoir solution containing chitosan and Ca²⁺. The droplets are thereby converted into MCCs. (b) Optical micrographs of individual MCCs with different numbers of (identical) internal compartments. The scale bars in the images are 100 μm. (c) Optical micrographs of a population of MCCs having either one or two (identical) internal compartments. The compartments all have a brown color because they contain magnetic Fe₃O₄ nanoparticles.