High-throughput and sensitive particle counting by a novel microfluidic differential resistive pulse sensor with multidetecting channels and a common reference channel

High-throughput particle counting by a differential resistive pulse sensing method in a microfluidic chip is presented in this paper. A sensitive differential microfluidic sensor with multiple detecting channels and one common reference channel was devised. To test the particle counting performance of this chip, an experimental system which consists of the microfluidic chip, electric resistors, an amplification circuit, a LabView based data acquisition device was developed. The influence of the common reference channel on the S/N of particle detection was investigated. The relationship between the hydraulic pressure drop applied across the detecting channel and the counting throughput was experimentally obtained. The experimental results show that the reference channel designed in this work can improve the S/N by ten times, thus enabling sensitive high-throughput particle counting. Because of the greatly improved S/N, the sensing gate with a size of 25 x 50 x 10 mu m (W x L x H) in our chips can detect and count particles larger than 1.5 mu m in diameter. The counting throughput increases with the increase in the flowing velocity of the sample solution. An average throughput of 7140/min under a flow rate of 10 mu L/min was achieved. Comparing with other methods, the structure of the chip and particle detecting mechanism reported in this paper is simple and sensitive, and does not have the crosstalking problem. Counting throughput can be adjusted simply by changing the number of the detecting channels.