Microwave Near-Field Detection of Single Biological Cells and Nanoparticles

Microwave interferometry techniques provide a means for constructing very sensitive impedance detectors. The impedance approach is well suited to a lab-on-chip based analysis platform as it is label-free and does not require complicated sample preparation. We describe a microfluidic device capable of detecting single biological cells while in flow. The device has a $40zF/\sqrt{HZ}$ sensitivity. In this paper we show how the approach can be used for detection of mammalian (CHO) cells as well as nanometer scale particles, such as bacteria.