Rapid Concentration of Nanoparticles with DC Dielectrophoresis in Focused Electric Fields

Abstract

We report a microfluidic device for rapid and efficient concentration of micro/nanoparticles with direct current dielectrophoresis (DC DEP). The concentrator is composed of a series of microchannels constructed with PDMS-insulating microstructures for efficiently focusing the electric field in the flow direction to provide high field strength and gradient. The location of the trapped and concentrated particles depends on the strength of the electric field applied. Both 'streaming DEP' and 'trapping DEP' simultaneously take place within the concentrator at different regions. The former occurs upstream and is responsible for continuous transport of the particles, whereas the latter occurs downstream and rapidly traps the particles delivered from upstream. The performance of the device is demonstrated by successfully concentrating fluorescent nanoparticles. The described microfluidic concentrator can be implemented in applications where rapid concentration of targets is needed such as concentrating cells for sample preparation and concentrating molecular biomarkers for detection.

Keywords: DC dielectrophoresis; Electrokinetics; Microfluidics; Nanoparticles.

Figure 1

a Diagram of a simple design for field focusing via insulator posts. The electric field (E) is indicated with field lines. b An insulating ‘tree’ structure for rapid electric field focusing

Figure 2

Diagrams illustrating the fabrication of the microfluidic device containing PDMS-insulating microstructures

Figure 3

a Photograph of the PDMS-insulating microstructure for concentrating of particles. b Diagram showing the microfluidic chip and experimental setup composed of microfabricated insulators, inlet/outlet reservoirs, two electrodes, and a fluorescence microscope

Figure 4

Simulated non-dimensional electric field (E) distribution in the concentrator. The electric field is applied from the ends of the main channel

Figure 5

Concentration of green fluorescent submicron polystyrene particles in the insulating microstructures. a– e Depicts the concentration at different regions as the applied voltage increased.Dark areas are the PDMS structures, and bright (green) areas are the microchannels formed by the PDMS. The flow direction is from the left to the right