High Throughput Microfluidic Electrical Impedance Flow Cytometry for Assay of Micro Particles

Recent advances in microfluidics and microfabrication techniques have led to a variety of portable and inexpensive lab-on-a-chip devices to make quantitative assays of microscale and nanoscale bioparticles. Among them, electrical impedance flow cytometers have become an indispensable tool in clinical and research laboratories for analysis of micro/nano bio-objects. Because of their simplicity and capability of single cell analysis, electrical impedance flow cytometers have been used widely to detect and characterize latex beads, pollen, biological cells, bacteria, viruses and DNA. One long standing drawback of the electrical impedance flow cytometers is their low throughput, namely they can only process a small amount of analyte at one time. To enable rapid analysis and real time detection of micro and nano objects, high throughput microfluidic electrical impedance flow cytometers have been developed to analyze a large volume of sample in a reasonable time. These devices are especially useful for rapid detection of bio-objects present in ultra low concentrations without a need for tedious preconcentration. In this article, we will review the state-of-the-art high throughput microfluidic electric impedance sensors for rapid analysis of micro bioparticles, including 1) multi-channel Coulter counters, 2) multiplexed resistive pulse sensors, 3) electrical impedance spectroscopy sensors and 4) radio frequency high bandwidth particle counters. Advantages and limitations of each type of impedance sensors are discussed.