Perforated Microcapsules with Selective Permeability Created by Confined Phase Separation of Polymer Blends

Semipermeable microcapsules have a great potential in controlled release of drugs, protection of catalysts, and immunoisolation of cells. However, a method to create such microcapsules with precisely controlled cutoff value and high mechanical stability remains an important challenge. Herein we report microfluidic approach to create microcapsules with size-selective permeability using phase separation of polymer blends in ultrathin middle layer of double-emulsion drops. The blend strongly confined in two-dimensional space exhibit local phase separation, instead of global separation. This enables the perforation of microcapsule membrane by selectively removing one of the phase-separated polymeric domains. The resultant monolithic membrane has uniform pores which connect the interior and the exterior of the microcapsules, thereby providing size-selective permeability. The pore size can be precisely tuned by regulating the extent of phase separation; this enables the control of cutoff value for permeation.