(222f) Frequency Sweep Rate Dependence on the Dielectrophoretic Response of Polystyrene Beads and Red Blood Cells

Dielectorphoresis (DEP) uses alternating current (AC) electric fields to polarize biological particles with experiments usually completed at static (fixed) frequencies.  Developing DEP response spectra for biological particles from static frequency experiments is laborious, yet essential in determining the differences in dielectric properties.  This work completed DEP experiments at multiple frequencies within a single experiment by sweeping the frequency with time to determine the DEP response spectra from less experiments. The optimal frequencey sweep rate was established using homogeneous 6.08μm polystyrene (PS) beads as a model system.  This frequency sweep rate technique was extended to ~7μm red blood cells (RBC), to verify its applicability.  A microfluidic device with Ti-Au quadrapole electrodes was used to subject the PS beads and RBCs to 10Vpp AC electric fields at frequencies between 0.010-2.0MHz with the sweeping rates ranging from 0.00080 to 0.17 MHz/s.  The PS beads displayed only negative DEP behavior over these frequencies with the sweep rate influencing the response time.  Faster sweep rates showed a lag in the DEP behavior for the PS beads as compared to the static frequency DEP responses, attributed to the dielectric relaxation time.  This establishes the experimental parameter that the frequency sweep rate must be slower than the particle polarization time to achieve incremental polarization.  Frequency sweep rates close to 0.00080 MHz/s yielded DEP behaviors consistent with static frequency DEP response for PS beads and RBCs.