Microcapsules, particles in the micron size with thin shells and liquid cores, have been used for a variety of delivery applications due to their beneficial cargo-to-encapsulant ratio and tunable release mechanisms. Encapsulation and release is commonly applied in only one direction as a single use carries, limiting their range of applicability. Dynamically and reversibly responsive microcapsules would allow for both self-adjusting release, as well as repeated capture and release of cargo using a recyclable encapsulation microcontainer. Hydrogels are ideal candidates for such dynamic microencapsulation systems due to the wide and facile property tunability by composition and functionality. Charged hydrogels are interesting in particular due to their charge-dependent and pH-responsive swelling and permeability. Direct synthesis methods that yield hydrogel microcapsules dispersed in water exhibiting water cores are highly desirable, but their fabrication through the commonly applied emulsion polymerization is challenging, since hydrophilic monomer phases do not emulsify in water, but instead form homogeneous solutions. Here we present a facile microfluidic process for the synthesis of well-defined and water filled hydrogel microcapsules with tunable mesh-sizes, composition, and macroscopic dimensions without the use of sacrificial oils, solvents, or extensive post-fabrication modifications. Our hydrogel microcapsules are based on thiol-ene synthesis chemistry templated by homogeneously sized double emulsion droplets with less than 10 vol% of shell material. The water-cored hydrogels show dynamic pH-responsive behavior with composition dependent reversible swelling spanning over an order of magnitude in size without compromising the integrity of the microcapsule shell. Additionally, the reversible swelling is accompanied by a change in permeability and molecular weight cut-off, allowing for the capture, trapping, and release of cargo over multiple cycles, expanding the application field of microcapsules to selective purification and separation.

Dynamically responsive hydrogel microcapsules

254th National Meeting (2017)

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