Terahertz and Photonic Bio-Electromagnetic Intrabody Communication for Wireless Nanosensor Networks

Abstract

In the last decade, major advancements in the field of micro and nanoelectronics, photonics, elctro- mechanical systems and wireless communication technologies have enabled the development of compact wearable devices, with applications in diverse fields such as medical wellness, sports and fitness, security as well as business operations. Despite their potential, existing wearable devices are only able to measure few physiological parameters, such as heart rate, temperature, or blood pressure. On the other hand, recent advances in nanotechnology have enabled the development of novel nanosensors that are able to detect different types of interactions at the nanoscale with unprecedented accuracy. Recently, in vivo nanosensing systems, which can operate inside the human body in real-time, have been proposed as a way to provide faster and more accurate disease diagnosis and treatment compared to traditional technologies. Nanosensors have permitted breakthrough applications that revolutionized the medical field through nanobiosensing, non-invasive drug delivery as well as early detection of cancer at the molecular level. This thesis develops a novel intrabody channel model to characterize bio-electromagnetic signal prop- agation and distortion between plasmonic nanoprobes and nanodetectors through the different body components, including blood and other body fluids, fat and skin. Unlike the commonly simplified channel models where the human body is treated as a cascaded multi-layered media, the intrabody channel is characterized at Terahertz (THz) from the nanodetector perspective. At the nanoscale, the body is a collection of different types of elements, including cells, organelles, proteins, and molecules, with different geometries and arrangements as well as different electromagnetic (EM) properties. The model presented throughout this thesis represents the first framework for a full-wave intrabody channel model at THz. One of the unique features of the presented model is that it accounts for the intra- body signal degradation at the nanoscale due to the combined effects of wave spreading, absorption and scattering. The mathematical formulation for spreading incorporates the effect of the nanosenor directivity based on a Gaussian beam distribution. As for absorption, both the Beer-Lambert law and the Double Debye model have been deployed in an analytical framework. The scattering effect is accurately modeled for both small and large body particles using Rayleigh scattering and van de Hulst approximation, respectively. Furthermore, since the absorption phenomenon is associated with heat emission, light-matter photothermal interaction is studied by presenting a genuine mathematical model which incorporates the thermodynamic processes derived based on the heat-diffusion theory. At the larger scale, signal degradation due to the discrepancies of the human tissue layers is also analyzed in this thesis. A cross-layer cascaded transmission line model has been deployed and used for THz wave propagation from the wearable device to the intrabody nanosensor, and vice versa. Not only has a systematic methodology for the analytical design and modeling of intrabody commu- nication at THz been comprehended in this thesis, but also a compact plasmonic nanoantenna for enhanced emission and detection of intrabody THz radiation has been carefully designed and critically analyzed. The presented framework of the nanoantenna captures the impact of the material com- plex conductivity and the nanostructured geometry on the propagation properties of Surface Plasmon Polariton (SPP) waves on the antenna.

Date of Award	Apr 2017
Original language	American English
Supervisor	Raed Shubair (Supervisor)