Publication

Abstract : Colloidal crystals have been explored in the literature for applications in molecular electronics, photonics, sensors, and drug delivery. However, much of the research on colloidal crystals has been focused on nano-sized particles with limited attention directed towards building blocks with dimensions ranging from tens to hundreds of microns. This can be attributed, in part, to the fact that large-scale particles are less prone to assemble in an organized fashion due to the relative absence of thermalizing forces. Nevertheless, ordered arrays of large particles are of interest both as a basis for tissue engineering scaffolds as well as a first step toward large-volume production of micron-scale “patchy particles” (anisotropically-labeled particles). In this work, ultrasonic agitation is being explored as a means of artificially “thermalizing” these particles in order to overcome kinetic barriers to packing in the creation of close packed, highly ordered, crystalline structures from large microparticles (18-100um). The film thickness is adjustable from a monolayler to a multilayer structure by changing the concentration of the solution and through a layer-by layer addition of particles. For this process, we are investigating the significance of substrate and solution properties like surface tension, viscosity, and particle concentration both experimentally and computationally. The interactions between the constituent particles within these colloidal formations can be estimated and analyzed using simulation-techniques. Simulations will not only inform as to what is occurring and ultimately achievable, but may also be used to direct the size, thickness, and quality of the overall crystal. This analysis and control over processing will ideally provide insight into, and control over the formation of a desired crystal structure.