(155f) Fabrication of Monodisperse Microcapsules with Stimuli-Responsive Membranes in Microfluidic Devices

Here we report a novel and simple method for preparation of monodisperse hollow microcapsules with pH-responsive membranes by combining microfluidics and interfacial cross-linking reaction. Using a capillary microfluidic device, uniform-sized oil-in-water-in-oil (O/W/O) emulsions, in which the water phase contains water-soluble chitosan and the inner oil phase contains terephthalaldehyde, are generated as templates for synthesizing microcapsules. The O/W/O emulsions were converted into microcapsules via the cross-linking reaction between terephthalaldehyde molecules and chitosan chains at the O/W interface. The prepared microcapsules have good monodispersity and sphericity with uniform hollow cavity and dense membrane structure, and exhibit diverse pH-sensitive characteristics. In acidic medium with pH ranging from 1.5 to 4.7, the microcapsules swell first, then collapse under osmotic pressure, and finally decompose and dissolve in the acidic solution. On the other hand, in weakly acidic or neutral medium with pH ranging from 5.8 to 7.1, the microcapsules only shrink and finally reach equilibrated state retaining good sphericity and structural integrity.

Keywords: Microcapsules; pH-response; Microfluidics