Dielectrophoresis of Gold Nanoparticles

Dielectrophoretic trapping is a separatory/analytical method that is capable of achieving high levels of analyte differentiation using a combination of electroosmotic flow, electrophoresis, and dielectrophoresis. The form of dielectrophoretic device used in these trials was of a gradient insulator-based design that induced the non-uniform electric fields necessary for dielectrophoretic trapping to occur. Development of such microfluidic devices began in the early 2000s and has produced several successful trials and refinements since then. Improvements have led to the ability of these devices to separate analytes to extremely high degrees of resolution as was demonstrated by the simultaneous separation of antibiotic resistant and antibiotic susceptible strains of bacteria in other experiments. The majority of analytes examined with these microfluidic devices have been biological in nature and on the scale of micrometers in size. The objective of this experiment was to test the lower limit of the device's resolution by attempting to use dielectrophoresis to trap gold nanoparticles via the balancing point between electrophoretic and dielectrophoretic mobilities. Trials successfully captured 10 nm fluorophore tagged gold nanoparticles at a mobility ratio of 6.16 x 1011 V2/m3, 60 nm citrate-capped gold nanoparticles at approximately 3.61 x 1010 V2/m3, and bare 10 nm gold nanoparticle aggregates at both 1.63 x 1010 V2/m3 and 1.68 x 1010 V2/m3. The corresponding voltages that were applied to achieve trapping were -1500 V, -2000 V, and -1500 V respectively. These findings were promising but reproducibility of the results was very low, largely due to matters of contaminants entering the devices and preventing the even, continuous flow of the analyte solution. Refinement of the analytical process should be pursued.