A Method for Sensing Dielectric Properties of Thin and Flexible Conductive Biocomposites

Abstract

This study investigates the dielectric properties of conductive biocomposites (CBs), which are integral to the development of advanced materials for flexible electronics and medical devices. A novel method employing Microwave Reflectometry (MR) is introduced, utilizing a miniaturized Vector Network Analyzer (m-VNA) and a dedicated sensing element (SE), to extract the dielectric properties of CBs. The method is grounded in a minimization principle, aligning the measured S11 reflection scattering parameter with its electromagnetic (EM) simulation, facilitating a refined process for determining the dielectric properties. The experimental setup was meticulously engineered, optimized, and validated using reference dielectric samples (RDSs) with known dielectric properties. The method was then applied to three innovative CBs, resulting in an accurate extrapolation of their dielectric properties. The findings highlight the method's versatility, cost-efficiency, and applicability to ultra-thin and flexible biopolymer films, offering significant potential for advancements in flexible electronics and bio-sensing applications.

Keywords: conductive biocomposites; dielectric permittivity; dielectric properties; electromagnetic simulations; microwave reflectometry; open ended coaxial probe.

Figure 1

Experimental setup for dielectric property sensing of CBs using the MR technique. The custom-designed SE is in direct contact with the conductive CB under test and connected to the m-VNA, which measures the reflected signal and aids in the accurate determination of the CBs’ dielectric properties. Cross-sectional view (a). Top view (b).

Figure 2

Tensile stress–strain measurement of CBs.

Figure 3

Pipeline of the proposed method for the extrapolation of CBs’ dielectric properties.

Figure 4

Comparison between the simulated and measured values of the $|S_{11}\left(f\right)|$ on reference liquids: methanol, ethanol, and propanol-2.

Figure 5

Comparative analysis of $|S_{11,real}|$ and $|S_{11,mo}|$ parameters: a visualization of the optimized match between experimental measurements and simulations for three CB prototypes.

Figure 6

Dielectric properties in terms of ${\epsilon }^{\prime }\left(f\right)$ and ${\epsilon }^{″}\left(f\right)$ for three CB prototypes extrapolated after the minimization procedure.