Eccentric magnetic microcapsule for on-demand transportation, release, and evacuation in microfabrication fluidic networks

Abstract

In this study, an eccentric magnetic microcapsule is reported for on-demand transportation, release, and evacuation in a micro-fabrication fluidic network. Using a droplet-based microfluidic technology, monodisperse magnetic polydimethylsiloxane (PDMS) core-shell microcapsules with a small eccentric ferrofluid core and a big aqueous core are fabricated from templates of dual-cored water-in-oil-in-water ((W1+W2)/O/W) double-emulsion droplets. The eccentric ferrofluid core enables the microcapsule to have flexible magnetic responsibility and orientation property, and the aqueous core can realize the encapsulation and release of nanoliter-scale encapsulants. Each microcapsule can be magnetic-guided by an external magnetic field to travel in microchannels along a designated route, and thus transport the encapsulated cargo (the aqueous core) to the targeted region. Then, the promptly shell rupture of the microcapsule due to the action of a time-averaged electrical stress from Maxwell-Wagner structural polarization in an externally-imposed alternating-current (AC) electric field allows the release of cargo into the region. Moreover, the empty microcapsule after release of the aqueous core can be magnetic-guided to evacuate from the device. Finally, to prove the practical utility of the eccentric magnetic microcapsule for on-demand transportation and release of nanoliter-scale encapsulant, this microcapsule is used to targeted convey fluorescent nanoparticles, which not only can serve as tracers to show the release of the aqueous core, but also can be cargoes themselves for bioimaging, sensing, and so on.