Multi-frequency DEP cytometer employing a microwave interferometer for the dielectric analysis of micro-particles

We present a multi-frequency dielectrophoresis (DEP) based microfluidic device for characterizing the complex dielectric properties of single micron-sized particles while in flow. The device employs a multi-electrode transmission line sensor coupled to a microwave-interferometer, capable of sub-attofarad sensitivity, for detecting the DEP-induced translation of the particle under study. DEP actuation of the particle at different frequencies - which is related to its dielectric response - is sensed as it travels along the sensor. Characterization of the dielectric response of polystyrene micro-spheres using two frequencies is demonstrated.