Dielectric Spectroscopy of Fluids and Polymers for Microwave Microfluidic Circuits and Antennas

The permittivity response from 0.5 to 40 GHz of ethyl acetate (C
₄
H
₈
O
₂
), ethylene glycol (CH
₂
OH)
₂
, castor oil (C
₅₇
H
₁₀₄
O
₉
), liquid paraffin, and other fluids commonly used for microwave microfluidic antennas and circuits is reported. The response of selected polymer solids, such as polydimethylsiloxane (PDMS), acrylonitrile butadiene styrene (ABS), acrylic, nylon, and others, used in microfluidics and 3-D printing of microwave structures was also studied from 0.5 to 20 GHz. Permittivity measurements were taken with a coaxial probe. Using a nonlinear least-squares fitting routine, the Cole-Cole dielectric relaxation model parameters are found for each material under test, thereby providing an analytic expression for their permittivity response.