Photoresponsive and Magnetoresponsive Graphene Oxide Microcapsules Fabricated by Droplet Microfluidics.

Fluid compartmentalization by microencapsulation is important in scenarios where protection or controlled release of encapsulated species, or isolation of chemical transformations is the central concern. Realizing responsive encapsulation systems by incorporating functional nanomaterials is of particular interest. We report here on the development of graphene oxide microcapsules enabled by a single-step microfluidic process. Interfacial reaction of epoxide-bearing graphene oxide sheets and an amine-functionalized macromolecular silicone fluid creates a chemically cross-linked film with micronscale thickness at the surface of water-in-oil droplets generated by microfluidic devices. The resulting microcapsules are monodisperse, mechanically resilient, and shape-tunable constructs. Ferrite nanoparticles are incorporated via the aqueous phase and enable microcapsule positioning by a magnetic field. We exploit the photothermal response of graphene oxide to realize microcapsules with photoresponsive release characteristics and show that the microcapsule permeability is significantly enhanced by near-IR illumination. The dual magnetic and photoresponsive characteristics, combined with the use of a single-step process employing biocompatible fluids, represent highly compelling aspects for practical applications.