Low-cost broadband RF impedance spectroscopy in micromachined microfluidic channels

Microfluidic impedance spectroscopy can be used to detect, identify, and characterize analytes in aqueous solutions, including biological materials such as proteins. We demonstrate a low-cost microfluidic device for impedance spectroscopy of samples over a broadband frequency range (200 MHz to 20GHz). The device consists of coplanar waveguide fabricated on a low-loss Isola RF substrate using a bonded two-layer structure with a milled microfluidic channel. Transmission line parameters of the device with various solutions in the channel were measured using a vector network analyzer. These measurements are compared with results obtained from numerical simulation using HFSS (High Frequency Structure Simulator) and broadband measurements obtained with a commercial probe. The results demonstrate the ability of the fabricated device to measure varying transmission parameters due to changing sample properties.