Ac Dielectrophoresis of Tin Oxide Nanobelts Suspended in Ethanol: Manipulation and Visualization

Abstract

This article presents results of detailed and direct real-time observations of the wide variety of SnO(2) nanobelt motions induced by ac dielectrophoresis (DEP) in an innovative microfluidic setup. High ac electric fields were generated on a gold microelectrode (similar to 20 mu m electrode gap) array, patterned on a glass substrate and covered by a similar to 10 mu m tall polydimethylsiloxane (PDMS) microchannel. Ethanol suspended SnO(2) nanobelts were introduced into the microchannel, and the DEP experiments were performed. Negative DEP (repulsion) of the nanobelts was observed in the low-frequency range (<100 kHz) of the applied electric field, which caused rigid body motion as well as deformation of the nanobelts. The negative DEP effect observed in ethanol is unusual and contrary to what is predicted by the Clausius-Mossotti factor (using bulk SnO(2) conductivity and permittivity values) of the dipole approximation theory. In the high-frequency range (similar to 1-10 MHz), positive DEP (attraction) of the nanobelts was observed. Pearl chain formation involving short nanobelts and particles was also observed in the two DEP regimes.