We realized and characterized a flow-rate control independent cell concentration sensor using Double Electrical Sensing Zones and control volume. We could count cells in control volume through the difference of counted cell numbers at two sensing zone before and after the control volume. From cells inside control volume, we calculated cell concentration.
In this experimental study, we used red blood cell(RBC). We obtained counting condition in our preliminary test: medium(PBS buffer) conductivity of 1.6 S/m for sensitivity of sensing zones and threshold voltage of 1V for counting cells. In that condition, we measured RBC concentration with concentration sensor of conventional Single Electrical Sensing Zone as well as the proposed Double Electrical Sensing Zones. The maximum error of the previous sensors and the present sensor compared to Hemacytometer are 20% and 20.6% respectively, which are nearly included in error boundary of Hemacytometer. We observed that the performance of cell concentration sensor with Double Electrical Sensing Zones is not effected by the flow-rate change during the measurement of RBC concentration, although cell concentration sensor with Single Electrical Sensing Zone can not measure RBC concentration with the flow-rate variation.
In this work, we demonstrated that the proposed sensor has enough performance comparing with conventional cell sensor in spite of the variation of the flow rate. This advantage makes it easy to integrate the cell concentration sensor with other components of integrated biological analysis systems.