Dielectrophoretic manipulation of polystyrene micro particles in microfluidic systems

In this work, DEP platforms with funnelled and micro-tip electrode patterns were fabricated, and integrated with polydimethylsiloxane (PDMS) microchannel blocks. The DEP platforms were employed to manipulate polystyrene particles of 1 and 3 um. The response of the system was characterised in a wide range of signal magnitudes (1-30 V peak-to-peak) and frequencies (100 kHz to 200 MHz), as well as the liquid flow rates (1 to 10 uL/min). Calculations were also carried out to analyse the DEP spectra of polystyrene particles when suspended in the medium (deionised water) to determine the optimum operating frequency of the DEP systems. Both experimental results and theoretical calculations indicated that polystyrene particles can experience positive and negative DEP forces within certain frequency ranges of the applied electric field, and the crossover frequency (where the DEP force is zero) of the system strongly depends on the conductivities of the particles. Additionally, larger particles experience stronger DEP forces and can be more efficiently concentrated at or repelled along the electrodes. The concentration performance of the DEP systems were evaluated by measuring the thickness of particle streams at different flow rates. Finally, the ability of funnelled and micro-tip electrodes to trap the particles was compared.