On-chip collection of particles and cells by AC electroosmotic pumping and dielectrophoresis using asymmetric microelectrodes

Abstract

The recent development of microfluidic "lab on a chip" devices requiring sample sizes <100 lL has given rise to the need to concentrate dilute samples and trap analytes, especially for surface-based detection techniques. We demonstrate a particle collection device capable of concentrating micron-sized particles in a predetermined area by combining AC electroosmosis (ACEO) and dielectrophoresis (DEP). The planar asymmetric electrode pattern uses ACEO pumping to induce equal, quadrilateral flow directed towards a stagnant region in the center of the device. A number of system parameters affecting particle collection efficiency were investigated including electrode and gap width, chamber height, applied potential and frequency, and number of repeating electrode pairs and electrode geometry. The robustness of the on-chip collection design was evaluated against varying electrolyte concentrations, particle types, and particle sizes. These devices are amenable to integration with a variety of detection techniques such as optical evanescent waveguide sensing.

The influence of flow intensity and field frequency on continuous-flow dielectrophoretic trapping

“…Additionally, since this frequency is generally above 20 kHz, ACEO is not apparent. Conversely, studies on optimization of trapping percentage using a combination of ACEO and DEP have generally been performed in the absence of pressure driven background flow [19][20][21][22][23]. With the advent of pressure driven flow, maximum throughput may be increased but the convection of the particles from the edge of the electrodes -where the field gradient is at a maximum -to their center is expected to result in a drop in the trapping percentage as the hydrodynamic force can more easily dominate the weakened DEP [24].…”

Improved particle concentration by cascade AC electroosmotic flow

“…The unique flow structure induced by ACEO enables particles to concentrate into a certain location in a microchannel with electrode array. Previous studies (Bhatt et al 2005;Lian et al 2006;Melvin et al 2011) have discussed the effectiveness of particle concentration by ACEO around electrodes located at limited positions in the fluidic channel. They confirmed that ACEO could collect particles toward a specific zone on electrode depending on the geometry of the electrode array.…”

A Magnetic Micropump Based on Ferrofluidic Actuation

“…Many alterative actuation mechanisms have been proposed to achieve a pumping effect in microfluidic devices, including acoustic-wave-based, rotary, piezoelectric, thermopneumatic, electrostatic, electromagnetic and ferrofluidic methods [16][17][18][19][20][21]. Recently, Lee's group [22][23][24][25] developed an impedance-based micro pump based on electromagnetic actuation and including a copper microcoil, a glass microchannel, a glass cover plate and a PDMS diaphragm with a magnet mounted on its upper surface.…”