Block Copolymer Microcapsules with Perpendicularly-Perforated Ultrathin Membranes for Controlled Transmembrane Transport

Abstract

Capsules with hollow cores and nanoporous shells enable controlled transmembrane permeation, which is crucial for regulated encapsulation and communication with the surrounding environment. Herein, an ideal platform is designed that simultaneously achieves fast permeation and precise molecular cut-off control by fabricating ultrathin shells with high-density, straight nano-channels. These shells are templated using the cylindrical phase of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymer (BCP), confined within the middle phase of water-in-oil-in-water (W/O/W) double-emulsion droplets. The single-emulsion droplets containing an optimal concentration of amphiphilic surfactant, dioctyl sulfosuccinate sodium salt (DOSS), spontaneously form double-emulsion droplets via water uptake from the surroundings and subsequent coalescence. The inner and outer interfaces are stabilized by DOSS and show neutral affinity to both PS and PDMS domains, facilitating the perpendicular alignment of cylindrical PDMS domains within a continuous PS leaflet during consolidation. Selective etching of PDMS results in the formation of straight cylindrical pores with uniform size and high density. These channels provide diffusion pathways that enhance transmembrane transport while achieving a well-defined molecular cut-off threshold, outperforming other size-selective shells. The resulting perforated shells, offering precision in molecular sieving and significantly enhanced permeation rates, hold great potential for advanced microreactors, microsensors, and artificial cell applications.