Dynamic Microcapsules from Complex Emulsion Drops*

Microcapsules are widely employed to protect and release sensitive cargo at predetermined trigger-events and rates. Since common release mechanisms involve degradation or destruction of the protective shell, their functionality is one-directional with single-use applicability. We demonstrate the fabrication of microcapsules that reversibly respond to external stimuli by changing the shell membrane’s property without structural degradation, enabling the repeated and dynamic change of its permeability upon changing trigger events. The encapsulating shell in our system acts as an active gate-keeper, regulating diffusion in and out of the aqueous core compartment. I will describe microfluidic fabrication methods for complex emulsion drops and the development of a number of polymer chemistries that allow for the synthesis of trigger-responsive hydrogel shells directly around water drops without the need of sacrificial templates. The trigger responsive microcapsules are distinctly different from microgels, as the properties in microcapsules are dictated only by the state of the shell membrane that can make up less than 10% of the microparticle. The shape, size, and permeability of the microcapsules are dynamically and actively tunable with external triggers.