Abstract
In this study, we developed a new fabrication method, the gas/oil/water (gas/O/W) method, for manufacturing large hollow polylactic acid (PLA) microcapsules. This method is based on the generation, growth and/or coalescence of microbubbles inside microdroplets of a dichloromethane (CH_2Cl_2) solution of PLA dispersed in a continuous aqueous phase. Microscopy images clearly showed that the diameter of hollow PLA microcapsules fabricated by the gas/O/W method was 10-20 μm, about one order larger than that of microcapsules obtained by the previously proposed bubble template method. We also identified the equilibrium radius of microbubbles in a closed volume of CH_2Cl_2-nitrogen solution by theoretical analysis. Both experimental and theoretical results showed that the gas/O/W method can be used to fabricate hollow PLA microcapsules including either a large single void or small multiple voids. Furthermore, we clarified the effect of PLA concentration on the equilibrium radius of bubbles in a closed system.
