Differential capacitively coupled contactless conductivity detection (DC4D) sensor for detection of object in microfluidic channel

In this paper, a novel design of a differential capacitively coupled contactless conductivity detection (DC4D) sensor with thin polydimethylsiloxane (PDMS) protective layer has been developed for detection of objects in microfluidic channel. The capacitive sensor consists of four adjacent electrodes which are arranged to form differential coplanar capacitor structures in order to achieve a high sensitivity and robust operation. The differential capacitance is changed when a micro particle (living cell for instance) crosses the microfluidic channel. This proposed sensor can be used for both conductive and non-conductive fluid media. The simulation inspection reveals that the sensor can detect an object with diameter down to 10 μm in a 50×100 μm cross-section channel, with capacitance change up to 0.05 fF. This novel design can not only detect the present of an object but also volume, velocity, as well as electrical property (conduct/non-conduct) of the investigated object.