Characterisation of Skin-based THz Communication Channel for Nano-scale Body-centric Wireless Networks

PhDIn pursuit of enhancing the capabilities of healthcare diagnostics and monitoring, the electromagnetic spectrum has been utilized efficiently from the MHz up to THz and beyond. The era of smart phones, wearable devices and on-body networks have unfolded plethora of health applications with efficient channel communication mechanisms, faster data transfer rates and multi-user functionalities. With the advancement in material fabrication and spectroscopic techniques, a new realm of healthcare nanodevices have emerged with immense potential to garner in-depth information of the human body, real-time of tissue morphology, molecular features, hydration level and atmospheric water vapour on channel parameters. In addition to this, engineered skin substitute models: 2D collagen and 3D organotypics, are investigated to address the importance of individual biological features comprising of water dynamics and cell culture, affecting the channel parameters. The experimental results of various tissue samples, skin substitutes and numerical evalua-tion of channel parameters can be used to further improve the communication capabilities of in-body nanonetworks. The original contributions on characterization of skin substitutes can be applied to study various health conditions, effects of drugs and skin ageing on a molecular level. The results presented in this thesis, foresee an increasing demand in skin substitute models due to their biological flexibility and control according to desired medical applications. monitoring and tackle medical emergencies. A collection of these devices with sensing capabilities together form a nanonetwork performing computing tasks such as storage, actuation, data transfer and communication. The thesis brings forth the analysis and optimization of channel parameters; such as pathloss and molecular noise temperature, when the proposed in-body nanodevices communicate amongst each other in the terahertz (THz) range. The novel contribution of the work is mapping the optical properties of human skin by bringing together the measurement of various skin tissues and its influence on channel parameters. In the later part of the thesis, emphasis is given on the individual biological entities of the tissue contributing to channel parameters, such as collagen as an abundant protein, variation in fibrous extra-cellular matrix due to fibroblast cells and amalgamation of different layers; namely, epidermis and dermis of the skin. Recently proposed graphene-based antennas resolve the cumbersomeness of existing medical devices by drastically reducing its size to a few hundreds of nanometres. These biocompatible nanodevices focus on exchanging the intricate details of the human body via nanoscale electromagnetic communication in the terahertz domain of the spectrum. The thesis aims to investigate the material properties of skin tissues with terahertz time do-main spectroscopy and numerically evaluate the channel parameters for in-body nanoscale networks that potentially would form an essential part of a hierarchical body-centric communication network extending from inside the human body to a wider community network. The results are presented in regards to the complexity of human tissue as a channel medium. The measured refractive index and absorption coefficient data is applied to numerically calculate channel pathloss and molecular noise temperature. The results provide a real-time analysi