Impedance technique for measuring dielectrophoretic collection of microbiological particles

Measurement of the impedance change resulting from the collection of microb iological particles at coplanar electrodes is shown to be an effective and potentially quantitative method of detecting dielectrophoresis. Strong corr elations between the frequency-dependent dielectrophoretic collection chara cteristics measured by impedance change and those observed using an establi shed counting method based on image analysis have been obtained for Escheri chia coli. In addition it is shown that the new electrical method can be us ed to sense dielectrophoretic collection of 19 nm diameter latex beads, par ticles too small to be resolved by conventional optical detection systems.