Juncheng Bao

Temperature controlled measurement setup for permittivity extraction of water up to 40 GHz from 10 to 40 °C

The proposed system in this paper enables the temperature controlled permittivity extraction of liquids up to 40 GHz from 10 to 40 °C. The temperature controlled environment consists of a temperature controlled chuck, probe station and a CPW microwave sensor that is coupled to a miniature T-type thermocouple. A large thermal mass and a platinum wire resistor ensure a precise reference temperature. Challenges in the sensor fabrication and measurements are discussed and further improvements are proposed for higher accuracy measurements. Extracted permittivity of water agrees well with the empirical models available in the literature.

Uniplanar microwave heater for digital microfluidics

This paper reports on a 4 GHz microwave droplet heater for digital microfluidics. The uniplanar device was fabricated using a gold-on-quartz process and was optimized for uniform heating within a 1 μL droplet. Microwave measurements show excellent agreement with COMSOL simulations. The uniformity of the induced temperature within the droplet was experimentally validated using fluorescence microscopy using a temperature sensitive fluorophore.

Investigation of thermal effect caused by different input power of biosensor using a novel microwave and optical sensing system for biological liquids

In this paper, we present a novel measurement system combining microwave vector network analysis with high-speed multi-channel fluorescence microscopy. Microwave and fluorescent measurement of 1 mM rhodamine B water solution was accomplished simultaneously with our system. No thermal effect was observed using the temperature dependent fluorescence of rhodamine B when the input power of the device varies from −21.99 dBm to 4.90 dBm. This novel system will enable us to correlate microwave and optical methods for biological characterization.

Liquid measurements at microliter volumes using 1-port coplanar interdigital capacitor

A coplanar waveguide based 1-port interdigital capacitor is presented as 0.1 μΕ dielectric liquid sensor for frequencies up to 1 GHz. An equivalent circuit circuit of the sensor is given, from which capacitance C and conductance G are used to compute the complex permittivity of the material under test (MUT). 3D FEM simulations show a linear relationship between real and imaginary parts of the complex permittivity of the MUT and the C and G of the equivalent circuit, respectively, which has been validated by measurements on water-isopropanol mixtures. Time-resolved spectral measurements on bakers yeast cells were also conducted and are analysed in this paper.

A bottom-up cell modeling strategy using broadband microwave and millimeter wave dielectric spectroscopy

In this paper we introduce a bottom-up microwave and millimeter wave modeling strategy for membrane bound biological systems. The approach is based on the stepwise integration of bulk liquid and membrane dielectric spectroscopy data into 3D biophysical models that are amenable to efficient electromagnetic computation. The purpose of this modeling effort is to develop more understanding of microwave electric field interactions with biological systems from a molecular biology point of view. The proposed strategy allows the systematic study of dielectric interactions within increasingly more complex membrane bound biological systems.