State of Utah Center of Excellence for Biomedical Microfluidics

I am currently working on the extension of Cyclical Electrical Field Flow Fraction (CEFFF). CEFFF is a separation technique in which particles are separated according to their electrophoretic mobilities. Cyclical fields are applied on typical Electric field Flow Fraction system (EFFF) systems instead of DC as electrode polarization causes 90% depletion in field in DC systems. Though, from theory it is understood that cyclical fields improve the field. It is still unknown what percentage of field is improved as typical EFFF systems consist of only two electrodes. In CEFFF at the critical frequency the elution time of the particles will be lowest. For frequencies higher or lower than this frequency elution time would be higher than the above mentioned critical frequency. If electrophoretic mobility is known and flow rate of the carrier solution is kept constant, then effective field can be estimated for that given characteristics of carrier solution. The effective field can also be measured if the system contains a reference electrode in addition to existing two electrodes. The goal of this project is to build an integrated electrode in CEFFF system for measuring the effective field and compare it with the estimated effective field from the model.

Theory developed previously on CEFFF is very simple and does not include many important issues Hence there is a need to develop a strong mathematical model which could include all the issues in CEFFF. The major issues in previously developed theory are:

1. The band broadening and the particle interaction issues are not introduced in the previous model so there is need to modify a single particle model to a concentration based two dimensional model using numerical methods which would take into account all of the particles in the channel.
2. The particle is assumed to start near one of the channel walls when the field is initiated to simplify the equations. But practically particles can exist anywhere inside the channel so it would be good to use probability theory rather than assuming particles start at one of the walls.

The final goal of the project is to characterize the polystyrene particles and various catalysts (obtained from Dr. Virkar). Based on CEFFF theory, when characteristics of carrier and field are kept constant, the elution time of particles for certain range of applied frequencies depends only on electrophoretic mobility. Hence after proper calibration of CEFFF system, electrophoretic mobility can be estimated from the elution time data.

Publications:

Journal Papers:

Merugu Srinivas and Bruce K. Gale , “Cyclical Electrical Field Flow Fractionation”, Electrophoresis, submitted.  (Likely publication date Feb 2005).

Invited Papers:

Bruce K Gale, Himanshu J Sant, Avinash Saldanha, Meregu Srinivas, Mahesh Thoppil, “Microfabricated Field Flow Fractionation Systems,” in Proc. of the Second Annual Louisiana Microsystems and Materials Conference, Baton Rouge, LA, August 20-22, 2001.

Reviewed Conference Papers:

Ameya S Kantak, Srinivas Merugu, Bruce K Gale, "Microfabricated Cyclical Electrical Field Flow Fractionation," in Proc. of MicroTAS 2003, Squaw Valley, California, October 5-9, 2003.

Srinivas Merugu, Nithin Narayanan and Bruce K. Gale, "High Throughput Separations Using A Microfabricated Serial Electric SPLITT System," in Proc. of MicroTAS 2003, Squaw Valley, California, October 5-9, 2003.

Conference 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 .

Srinivas Merugu, Nithin Narayanan, and Bruce K. Gale, "Microscale Serial SPLITT Systems," 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 .

Master of Science Thesis

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