SUMMARY

Flexible hybrid electronics (FHE) has attracted substantial interest by combining the high performance of silicon integrated circuits (ICs) and mechanical versatility of flexible printed circuits. FHE systems are being increasingly used in health, automotive, and Internet-of-Thing (IoT) applications, where high-frequency communication is an important element for the wireless operation of the FHE devices. Thus, understanding the RF performance of relevant components under various extents of deformation in their operating conditions, such as bending and stretching, is crucial to the reliable design of FHE devices. Most previous studies in literature, however, are focused on the direct current (DC) performance of printed electronics through conductivity measurement. A more accurate evaluation of RF performance of printed electronics requires the characterization of scattering parameters (S-parameters), which concerns changes in the overall geometry, dielectric properties of substrates, and the operating frequency band. The scarcity of experimental data and numerical models for FHE relevant components in the RF regime remains a major obstacle to improving the reliability of FHE devices.

The main objective of this doctoral work is to investigate the RF performance of FHE components under mechanical deformation through the characterization of S-parameters, and to understand the underlying mechanism through which S-parameters are related to changes in geometry, conductivity, and dielectric properties. Experimental measurement of S-parameters of printed transmission lines will be obtained in monotonic and cyclic tests under stretching and bending conditions. Both coplanar waveguides (CPW) and microstrip lines will be considered in this work. Simulation will be performed to understand the role of geometry, conductivity, and dielectric property changes in relation to changes in S-parameters, with the goal of determining the optimized model parameters for improved agreement between simulation and experiments. Finally, the insights gained from experimental and modeling efforts on the printed transmission line will be applied to the simulation of printed antenna under bending and stretching, and the results from such simulations will be validated through experiments.