Reversible Control of Anisotropic Electrical Conductivity using Colloidal Microfluidic Networks; Final rept. 15 Feb-31 Dec 2006

摘要

This research addresses the tunable assembly of reversible colloidal structures within microfluidic networks to engineer multifunctional materials that exhibit a wide range of electrical properties. Our work has focused on studying electric field-directed assembly of gold colloids and understanding how tuning colloidal configurations can be utilized to modulate electrical properties within a microfluidic electric circuit. More specifically, we have found that a single circuit element can act as a variable resistor, capacitor, and inductor by regulating the colloidal structures within the gap between electrodes. Navigating the applied AC voltage-frequency phase space allows us to probe a wide range of colloidal configurations that resemble 'capacitive' and 'resistive' networks in their limiting cases. All colloidal configurations formed were reversible and repeatable, and it was possible to switch from one configuration to other interchangeably. Based on a scaling analysis, different electrokinetic forces that drive assembly have been identified. The scaling analysis was able to consistently interpret experimental observations of particle dynamics over the planar electrode system, and can be extended, within limits, to more complex electrode geometries for future studies.