Mater. Res. Soc. Symp. Proc. Vol. 1 2 © 2014 Materials Research Society DOI: 10.1557/opl.2014.38 Programmable Anisotropic Microparticles for Self-Assembly Applications Jonathan Liu, 1 C. Wyatt Shields IV, 1,2 Oluwatosin Omofoye, 3 Gabriel P. Lopez 1,2,3 1 Department of Biomedical Engineering, Duke University, Durham, NC, USA 2 Research Triangle Material Research Science and Engineering Center (Triangle MRSEC), Durham, NC, USA 3 Department of Mechanical Engineering and Materials Science (MEMS), Duke University, Durham, NC, USA Abstract Colloids with anisotropic shape and properties can enable the assembly of advanced materials otherwise not attainable by microfabrication. In this study, we present a convenient method using common microfabrication tools to generate a diverse array of non-spherical microparticles with well-defined shapes, sizes, electromagnetic properties for self-assembly applications. Projection photolithography onto SU-8 photoresist enabled the production of large aspect ratio microparticles such as cubes, cuboids, cylinders, hexagonal prisms, and parallelepipeds. We characterized these particles to confirm their anisotropic shape and size monodispersity. Fluorescent stains (e.g., Nile red) were mixed into the photoresist prepolymer to enhance the visualization of particle orientation. Particles designed for passive self-assembly were prepared by conventional photolithographic techniques. Particles designed for active assembly were then decorated with metallic patches in precise locations along the surface (e.g., top, side or multiple sides) using electron beam metal evaporation. This metal deposition process can enable orientational control of particles during their assembly in directed fields. After fabrication, large particles (e.g., 1,000 µm 3 ) were released from the substrate via gentle sheer forces, whereas small particles (e.g., 10 µm 3 ) were released by the dissolution of a sacrificial layer underneath the SU-8. Suspending the particles in water with surfactant (or other suitable solvents) provided amenable conditions for their assembly in static or dynamic systems. These conventional methods have the potential to catalyze new research in the fabrication and assembly of anisotropic patchy particles with controllable properties for the hierarchical development of self- assembled micromirrors, biosensors, and photonic crystals as examples. INTRODUCTION Colloidal assembly continues to be a central topic across various disciplines of engineering, chemistry, and biomedical research as well as industrial development due to its versatility for synthesizing a variety of useful structures such as nanowires, crystallites, and other highly ordered materials for creating useful structures such as photonic or phononic devices. In particular, Janus particles are of significant interest and have seen success in the assembly of ordered chains, clusters, and large-scale crystalline lattices [1-5]. However, these structures typically contain spherical components, thereby greatly limiting the potential complexity of achievable architectures. In light of this, we describe a simple approach to generate a variety of 62