SUMMARY

Nanobelts are a new class of semiconducting metal oxide nanowires with good potential as building blocks for nanoscale devices. The present research focuses on the manipulation of SnO2 nanobelts using microfluidics and electric fields. Dielectrophoresis (DEP) was demonstrated on SnO2 nanobelts, which resulted in the trapping of nanobelts between electrodes. Detailed and direct observations of the wide variety of nanobelt motions induced by DEP forces were made using an optical microscope. High AC electric fields were generated on a gold microelectrode (~ 20 micrometer gap) array, patterned on glass substrate, and covered by a 10 micrometer tall PDMS (polydimethylsiloxane) channel, into which the nanobelt suspension (in ethanol) was introduced for DEP experiments. Negative DEP (repulsion) of the nanobelts was observed in the low frequencies (<100 kHz), which caused rigid body motion as well as deformation of the nanobelts. Evidence of electrophoresis has also been found. In the high frequency range (~ 1 MHz – 10 MHz), positive DEP (attraction) of the nanobelts have been observed. A fluidic nanobelt alignment technique was also studied and used in the fabrication of single nanobelt devices with small electrode gaps. These devices were primarily used for impedance spectroscopy measurements to estimate the nanobelt electrical conductivity. The existence of negative DEP effect is unusual considering the fact that if bulk SnO2 conductivity and permittivity values are used in combination with the electrical properties of the liquid, a simple DEP model predicts positive DEP for the frequencies studied. It is thought that the negative DEP is due to a less conductive layer on the nanobelts. Parametric numerical simulations were conducted using COMSOL Multiphysics software to study the effect of the different parameters affecting the DEP force, and gain additional insights. The DEP force was computed using the Maxwell Stress Tensor (MST) approach.