Dielectrophoresis: Integrated Approaches for Understanding the Cell

Abstract

The complex permittivity of a biological cell reflects its substance and structure and thus seems to reflect its function, activity, abnormality, life/death, age, and life expectancy. Although it may be very difficult to measure the complex permittivity of each cell, the movement or behavior of the cell as affected by its complex permittivity can be observed under the microscope. The dielectrophoretic force (DEP force) generated on a particle in a nonuniform electric field causes movement of the particle in accordance with its complex permittivity or polarizing characteristics. Thus, differences in the substance or structure of biological cells lead to differences in their movement or behavior in a nonuniform electric field. The principle of dielectrophoresis (DEP) and the estimation of the DEP force are described in this chapter. The distinctive features of DEP are applied in the separation of biological cells, e.g., leukocytes from erythrocytes, leukemia cells from normal leukocytes. This cell separation ability is affected by the frequency and amplitude of the applied voltage. To estimate the DEP force generated on a single cell, the terminal velocity of the cell in the medium should be measured withouttaking it out of the DEP device. The procedure to measure the terminal velocity is also described.