(535d) Dielectrophoretic Manipulation of Silica Nanoparticles in Optofluidics

We present a dielectrophoretic (DEP) system in microfluidics capable of nanoparticle positioning for the objective of achieving a dense nanoparticle core and primarily liquid cladding optofluidic system. Various DEP conditions were investigated using 450 nm and 230nm diameter silicon dioxide (SiO2) nanoparticles at several alternating current (AC) voltage amplitudes, flow rates and frequencies. Using an array of curved DEP microelectrodes and by utilizing DEP nanoparticle focusing and repelling capabilities, we were able to form a particle dense stream in the center of the microfluidic channel. A high refractive index core composed of DEP assembled nanoparticles with a lower index cladding composed of DI water and very low concentrations of particles was formed. By introducing visible light as the excitation source, it was observed that the nanoparticle aggregate either guides or scatters light. The larger particles tend to scatter light while the smaller particles tend to guide light. The results illustrate a pioneering accomplishment of a configurable nanoparticle-core liquid cladding waveguide that is relevant for optofluidic, lab-on-a-chip and biosensing applications.