Microfluidic sensor for noncontact detection of cell flow in a microchannel

A microfluidic sensor for detection of cells flowing in a microchannel is presented. The sensor consists of a PDMS (PolyDiMethylSiloxane) layer with two planar microreservoirs connected by a microchannel. The bottom sides of the microreservoirs are faced to two sensing electrodes realized on a PCB (Printed Circuit Board). A noncontact measurement is ensured by an insulator layer between the electrodes and the fluid. Particles flowing in the microchannel cause changes in the conductivity of the narrow path formed by the fluid, producing variations in the impedance between the electrodes. A tailored electronic interface based on a DDS (Direct Digital Synthesis) device is proposed to measure the impedance variations. In the experimental tests, the cell flow is detected by changes in the effective capacitance and conductance between electrodes. These preliminary results are promising for biological measurements such as counting and sizing of cells in different matrices.