Authors: B.C. Gierhart, S.D. Collins, D.G. Howitt, S.J. Chen and R.L. Smith
Affilation: University of California, Davis, United States
Pages: 20 - 23
Keywords: dielectrophoresis, nanoparticles, gold nanoparticles
Dielectrophoretic assembly of nanoparticles has great utility in creating intricate designer nanoscale structures. Despite their utility, little is known about the mechanisms that govern different assembly morphologies. The magnitude and frequency of the applied field, nanoparticle size, composition, and distribution, and the characteristics of the surrounding medium all play significant roles in the dance of nanoparticle assembly. Some reports on nanoparticle dielectrophoresis indicate a frequency dependent threshold voltage is required to initiate assembly, while other reports indicate assembly velocities are voltage and frequency dependent. Most authors attribute parametric variation primarily to variations in the dielectrophoretic force. It has recently become clear that this simple picture of dielectrophoretic assembly is incomplete. This study examines the influence of voltage, frequency, fluid medium, and nanoparticle size theoretically and experimentally. High resolution TEM visualization of the nanostructures is used to confirm proposed assembly mechanisms. The major frequency dependent influence on deposit morphology is not the Clausius-Mossotti factor within the dielectrophoretic force itself, but instead is AC electroosmotic fluid flow and the influence of the electrical double layer. Measurements of fluid flow velocity show a substantial contribution from AC electroosmotic flow. These mechanisms have not previously been associated with gold nanoparticle dielectrophoresis.