Characterization of polydimethylsiloxane (PDMS) as a wearable antenna substrate using resonance and planar structure methods

Abstract

In this paper, a flexible silicon-based elastomer Polydimethylsiloxane (PDMS) is characterized experimentally. For the characterization of the dielectric properties of PDMS, two experimental methods are applied. The first method is based on resonance measurements by the two-resonator method. This method allows the determination of the dielectric constant εr and dielectric loss tangent tanδεr of non-metallized samples in both parallel and perpendicular directions. The obtained values for the dielectric constants differ; εr_par ~ 2.71 (12–36 GHz) and εr_perp ~ 2.558 (6–29 GHz). This material has a weak but measurable anisotropy ~5.7%. The second method is based on the application of different planar structures (resonators and transmission lines) by integrating the PDMS samples without metallization. The proposed two methods give the average value of equivalent isotropic dielectric constant εeq, as equals to 2.66 (εr_par > εeq > εr_perp) and equivalent dielectric loss tangent tanδε_eq, as equals to 0.023 in the frequency interval 2–36 GHz. The results obtained by the analysis of PDMS samples are compared with results for isotropic Polytetrafluoroethylene (PTFE) and Cyclo Olefin Polymer (COP) samples. The analysis performed experimentally proves that PDMS is a good choice as a wearable antenna substrate.