UC San Diego

It is traditionally difficult to integrate a wide range of nanocomponents into macroscopic or mesoscopic scale systems. Traditional methods of nanofabrication use large scale patterning of homogenous layers, or make use of the intrinsic properties of the particles in to bind them together in an uncontrolled fashion. In this dissertation, a method for the rapid, highly controlled deposition of water soluble nanoparticles is demonstrated. Through the use of direct current controlled electrodes in a buffered solution, nanoparticles are pulled from a dilute solution to a complementary binding surface in a few seconds where they form a single layer. By repeated processing steps we are able to rapidly fabricate multilayered structures using different nanoparticles, making use of both overall directed assembly and the local self assembly of the particles themselves. Because we are able to control the particle concentration, we can effectively control the particle binding rate at the deposition surface. Described in detail is a method for characterizing the deposition process to determine both the optimal parameters (in terms of deposition time and current) for a given particle type, and methods to determine the level of interparticle self binding. Optical fluorescent imaging and electron microscopy were used extensively to characterize the rate of particle accumulation both as a function of current and time for a single deposition, and for the overall process through subsequent layers. The electric field assisted self assembly work was carried out for 40nm and 200nm biotin/streptavidin coated particles, as well as particles covered in various DNA sequences, quantum dots, and gold particles. Particle deposition profiles across the electrode are also discussed, with the root causes for the observed pattern explained using various electric field deposition from this work, as well as some supporting experiments from tangentially related experiments. These experimental results are compared to various simulated systems. Finally some preliminary work on long range, high voltage, high conductivity dielectrophoresis systems is discussed with an eye towards fully integrated sample analysis systems