Multicompartmental materials by electrohydrodynamic cojetting.

While multicomponent microand nanoscale structures and even atomically blended materials have been in use for centuries in various bulk forms ranging from metal-nanoparticle-doped glasses to crystalline alloys, recent advances in top-down and bottom-up fabrication processes have allowed for improved control over the structure of microand nanoscale multicomponent materials. These multicomponent microstructured materials are important in imaging, drug delivery, sensing, and tissue engineering. A simple example of such a material is the core–shell particle, where the shell could improve the compatibility with the surrounding environment in imaging applications, provide for a controlled release profile in drug delivery, or give tuneable absorption properties in plasmonic particles. While the core–shell configuration has its utility, there is ample room for more complex configurations. In drug delivery and diagnostics, for example, it would be attractive to have a platform where multiple compartments of a microstructured material could be used to: 1) target the desired cells, 2) deliver the desired drug(s) at the desired rate(s) for the required duration(s), and 3) label the treated cells for diagnostic evaluation. Various techniques have been utilized to fabricate multicomponent microstructured materials with core–shell, nested, Janus, and/or granular architecture. Figure 1 depicts examples of multiphase microstructures patterned by various techniques, including the microfluidic sheath flow of granular Janus particles (Figure 1a), laser direct writing of a trapped colloidal fluid (Figure 1b), electrospinning of inorganic– organic hybrid materials in core–sheath and side-by-side configurations (Figure 1c and d), and the electrospray and cellular uptake of water-stable Janus particles (Figure 1e). While the solution-phase syntheses of particles can be scaled up readily, they have not been well suited for the arbitrary placement of multiple components on the microscale. Stan-