Panel Discussion

Dielectrophoresis (DEP) has been widely studied for its potential as a biomarker-free method of sorting cells and other bioparticles based on their intrinsic dielectric properties [e.g., 1-8]. Under appropriate experimental conditions the DEP frequency spectrum typically exhibited by a viable mammalian cell in suspension is characterized by two frequencies, fxo1 and fxo2. At these two characteristic frequencies, commonly known as the DEP cross-over frequencies, the effective electrical impedance (i.e., the a.c. conductance and capacitance values) of the cell exactly match those of the fluid it has displaced.

At low frequencies (<10 kHz) viable cells typically exhibit negative DEP and move away from electrodes, with the transition to positive DEP occurring at fxo1 - where the cells move towards high field regions at the electrodes. The investigation, understanding (in terms of cell biology) and biomedical exploitation of this phenomenon can be considered to represent exploration of the ‘1st frontier of cellular dielectrophoresis’. The results of this work, extending over more than 25 years, are now exploited in the form of various commercial devices for clinical and biomedical applications. The status of this activity and possible future trends will be reviewed.

A transition from positive DEP back to negative DEP occurs at fxo2 (~150 MHz [10]). The factors that control the high frequency DEP cross-over at fxo2 have only recently been explored, and the status and implications of this ‘2nd frontier of dielectrophoresis’ will also be discussed in this presentation.

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