Wideband microwave interferometry sensor with improved sensitivity for measuring minute variations in dielectric properties of chemical liquids in microfluidic channels.

• We propose an on-chip wideband microwave interferometry sensor for measuring minute variations in the dielectric properties of chemical liquids with a small volume (5 ul). • The relationship between the variations in transmission-zeros and the variations in dielectric properties of the sample are investigated. • The sensitivity of the wideband interferometry sensor is improved about 1.2 times by introducing the ESD at the sensing region. In this paper, we propose an on-chip wideband microwave interferometry sensor to measure minute variations in the dielectric properties of chemical liquids with a marginal volume (5 ul). The device is based on coplanar waveguide (CPW) and slot-line technology. It consists of two uniplanar broadband hybrid ring couplers and two branches. Each branch is loaded with an electrically small discontinuity (ESD), which is the sensing region. If the sensor is unloaded or loaded with the same material under test (MUT), we obtain a transmission-zero. When different MUTs are loaded into the two microfluidic channels, new interference frequencies occur. Variations in transmission-zeros are employed to express variations in the dielectric properties or concentrations of the MUT. Experiments show that the sensitivity of the ESD-inspired interference sensor is higher (average value from 13 GHz to 17 GHz) than that of the wideband interference sensor by 1.2 times. [ABSTRACT FROM AUTHOR]