(176e) The Controlled Synthesis of Complex Microparticles Using Continuous Flow Lithography and Their Self-Assembly



Precisely shaped polymeric particles and structures are widely used for applications in photonic materials, biomaterials, and self-assembly. Current approaches for particle synthesis are either batch processes or flow-through microfluidic schemes that are based on two-phase systems, limiting the throughput, shape and functionality of the particles. We report a one-phase method that combines the advantages of microscope projection photolithography and microfluidics to continuously form morphologically complex or multifunctional particles down to the colloidal length scale. Acrylate based polymer chemistries can be used to synthesize virtually any two-dimensional extruded shape. We have demonstrated the synthesis of monodisperse polymeric disks, polygons, curved and asymmetric objects in the size range of 5-100 ìm as proof of principle. Polymerization was also carried out across laminar, co-flowing streams to generate particles containing different chemistries, whose relative proportions could be easily tuned. By using appropriate masks, we can synthesize large numbers of particles that have both complex shapes and multiple distinct chemistries. Such anisotropic particles may be used as building blocks for the synthesis of different kinds of self-assembled structures. As a proof of principle, we use this process to synthesize wedge-like particles bearing distinct hydrophilic and hydrophobic sections. These particles are found to orient themselves at oil-water interfaces to minimize the interaction of the hydrophobic surface with water and the hydrophilic surface with oil. In addition, capillary forces also enable such particles to form micelle-like structures in water. We will present a study on how changing particle geometry affects the type of self-assembled structures that are formed.