State of Utah Center of Excellence for Biomedical Microfluidics
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Cyclical Electrical Field Flow Fractionation (CyElFFF) Cyclical
electrical field flow fractionation [CEFFF] is a new field flow fractionation
techniques. The field applied in CEFFF will be an alternating electric field
rather than a unidirectional field. In CEFFF, particles oscillate in the z
direction rather than accumulating near the walls and their velocities in z
direction will depend on the transport rate (electrophoretic mobility) so the
particles will be at different positions in z direction and elute at different
time intervals.
We have developed a mathematical model for the CEFFF mechanism. We
deduced from the mathematical model that retention in CEFFF depends on
frequency, magnitude of field, and electrophoretic mobility. The experimental
results that were obtained by varying these parameters closely matched with
mathematical model. Figure 1 shows the fractograms we obtained by varying the
magnitude of a square waveform with other parameters being constant (frequency
0.5 Hz and flow rate 1ml/min).
Figure
1 Fractograms
obtained at different magnitudes of square wave voltage applied. From
the figure we can observe that as voltage is increased from 2 volts peak to peak
to 4 volts the elution time decreases as particles move towards middle of the
channel from side walls as magnitude of field is higher. In case of 8,12,16, and
20 peak to peak voltages, as magnitude is increased particles eluted later, as
in this case particles were able to reach the other wall so, as magnitude
becomes higher they reach the other wall faster and are retained their until the
field reverses. The system has also been characterized with regard to frequency and waveform. The advantages of CEFFF are 1) nearly 100% of the applied field acts on particles due to reduction in double layer capacitance and 2) its size independent separation as its mechanism depends only on transport rate of particles (electrophoretic mobility). Note that the Center is organizing the 13th International Symposium on Field- and Flow- based Separations. Students in this area: Ameya Kantak, Merugu Srinivas, Siddharth Chakravarthy Related Papers Ameya Kantak and Bruce K. Gale, "Microscale Cyclical Electrical Field Flow Fractionation," in Proc. Of the 11th International Symposium on Field Flow Fractionation, Cleveland, OH, October 7-10, 2003. Siddharth Chakravarthy and Bruce K. Gale, "PolyPIPosome Characterization using a Combination of Normal and Cyclical Electrical Field Flow Fractionation," in Proc. Of the 11th International Symposium on Field Flow Fractionation, Cleveland, OH, October 7-10, 2003. Meregu Srinivas and Bruce K. Gale, "Cyclical Electrical Field Flow Fractionation," in Proc. Of the 10th International Symposium on Field Flow Fractionation, Amsterdam, Netherlands, July 2-5, 2002. |
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