Nano-objects have properties that are distinctly different from bulk solid-state materials; including unique magnetic, electronic, optical, chemical, and biological characteristics. The controlled distribution of matter or “patchiness” is important for creating anisotropic building blocks that respond with preferential alignment to the application of external fields. As a consequence, the control of materials distributions in micro/nano-objects introduces an additional design parameter - beyond size and shape. Although the reliable and efficient fabrication of building blocks with controllable materials distributions will be of interest for many applications in research and technology, such as imaging probes, building blocks for self-assembly, or drug delivery vehicles, their synthesis has been addressed only in a few specialized cases, and suitable fabrication methods with general applicability are still missing.

We will report on the design and synthesis of polymer-based particles with two and three distinct phases[1,2]. The multiphasic geometry of these particles is induced by the simultaneous electrohydrodynamic jetting of parallel polymer solutions under the influence of an electrical field. Electrified jetting is a process to generate liquid jets by use of electrostatic forces. The high electrical potentials (typically several thousand volts) applied between the jetting liquids that are fed through a capillary and a collecting substrate will induce jetting of the charged liquid. The final morphologies of the resulting nano-objects are mainly determined by the properties of the jetting liquids and the process parameters. In our system, preferential compartmentalization is maintained throughout jetting and solidification and results in biphasic particles with diameters between 100 and 500 nm (approximate size range of viruses or organelles). Using transmission electron microscopy, scanning electron microscopy, and scanning laser confocal microscopy, we demonstrate the applicability of the process to control size, shape, and materials distribution at the nanoscale.

Moreover, the individual phases can be independently loaded with biomolecules or selectively modified with model ligands, as confirmed by confocal microscopy and transmission electron microscopy. These novel types of nanocolloids may enable the design of multicomponent carriers with interesting properties for drug delivery, molecular imaging, or guided self-assembly.

[1] K.-H. Roh, D.C. Martin, J. Lahann, Biphasic Janus Particles With Nanoscale Anisotropy. Nature Materials 2005, 4(10), 759-763. (This article has been highlighted in Small 2, 596-598.) [2] K.-H. Roh, D. C. Martin, J. Lahann, Triphasic Nanocolloids. Journal of the American Chemical Society, 2006 (accepted for publication).