Active Manipulation of Quantum Dots using AC Electrokinetics

The superior optical and electrical properties of quantum dot (QD) nanoparticles are being applied in a new generation of QD devices for microelectronic, nanophotonic, and biomedical systems. Research on integrated QD-based systems has been focused on passive manipulation of QDs including template-guided self-assembly, molecular scaffold-based assembly, and microbead-based assembly. However, little effort has been devoted to development of methods for active manipulation, such as positioning and concentration, of QDs. In this study, we show that 20 nm colloidal QDs can be effectively positioned and concentrated using a combination of dielectrophoresis (DEP) and AC electro-osmosis (ACEO). The long-range fluid motion generated by ACEO entrains QDs to the area near the electrode surface, which facilitates the trapping of QDs by DEP. A systematic investigation was performed to examine electrokinetic processes at different applied frequencies and voltages using a concentric electrode configuration. We demonstrate that QDs can be dynamically positioned with an electric field strength as small as 10 kV/m and define the operating parameters for increasing the concentration of colloidal QDs by 2 orders of magnitude within one minute.