Quantitative estimation of biological cell concentration suspended in aqueous medium by using dielectrophoretic impedance measurement method

We describe a new technique that realizes the quantitative estimation of the biological cell concentration in an aqueous medium. The proposed dielectrophoretic impedance measurement method utilizes the positive dielectrophoretic force to capture suspended biological particles onto an interdigitated micro-electrode array in pearl-chain formation. Higher cell concentration results in faster development of the pearl chains, which are electrically connected in parallel within the electrode gap to increase the conductance and capacitance between the electrodes. By monitoring temporal variation of the electrical impedance, it is possible to quantitatively evaluate the cell population according to a theoretical model of the cell collection process. It has been demonstrated that a suspension liquid of Escherichia coli could be accurately assayed in about 10 min at 10(5) cm(-3) concentration.