Plasmonic Nanoparticles for Optofluidic Applications

This thesis discusses the application of colloidal particles to optofluidic systems. Colloidal particles can be added as a “dopant” to the liquids in these devices to provide functionality that cannot be obtained with homogenous fluids. We examine electrooptic effects in liquid suspensions asymmetric metallic nanoparticles. The theoretical optical properties of gold nanorods and noble metal nanohalfshells are computed and compared with those of actual colloidal dispersions. We discuss the design and fabrication of electro-optic waveguides utilizing these suspensions as the active material. We also study the dynamics of photothermal holograms recorded by nanosecond laser pulses in suspensions of silver nanospheres. Unexpected transients in the grating diffraction efficiency correspond to the nanoscale inhomgeneity of the colloid. Longer timescale decay can be used to measure the thermal conductivity of the liquid as predicted by the established theory of heat conduction. This technique is extended to perform spatial imaging of the thermal diffusivity of immiscible binary liquids. Gold nanosphere coated substrates for microfluidic devices are employed to enable optical actuation of fluids. Nanoparticle absorption of continuous wave laser light was used to trap air bubbles inside partially filled microfluidic channels. Light focused on the array near one side of the trapped bubble will drive a mass flow across the bubble. This evaporative bubble assisted mass transport mechanism can be operated as a pump powered by a stationary laser beam. In addition, the process efficiently separates volatile and non-volatile materials and can concentrate and purify specimens in solution. vi Finally, several schemes for storing and extracting data from subwavelength volumes using spectral multiplexing of semiconductor quantum dots are explored. We demonstrate microfluidic composition and delivery of cocktails of several colors of quantum dots to act as information packets for optical storage. In addition we analyze imaging at the subwavelength level using a patterned surface of quantum dots. The theoretical performance of such a surface is compared to imaging through nanoapertures as is currently implemented in optofluidic microscopy.