Electric impedance spectroscopy using microchannels with integrated metal electrodes

Microelectric impedance measurement systems containing microchannels with integrated gold electrodes were fabricated to enable EI measurements of femtoliter (10(-15)) volumes of liquid or gas. The microinstruments were characterized using samples of air, partially deionized water, and saline solutions with various ionic concentrations over the frequency range of 100 Hz to 2 MHz. Resulting spectral patterns varied systemically as a function of ionic concentration. In addition to industrial sensing applications, this technology may prove to be beneficial in monitoring microsystems utilizing on-chip fluid chemistry, measuring the dielectric dispersion of polymer solutions, and determining the electrical properties of isolated biological materials. [296].