Modeling and experimentation of through-the-body RFID links and application to smart prosthesis

The Internet of Things (IoT) is the natural evolution of the current concept of Internet in which even the common objects of our daily lives, uniquely identifiable and equipped with sensing capabilities will be globally connected and able to communicate and cooperate each others to improve the quality of our life. In this scenario even the human body could become a sensing node of the network, able to communicate its needs and health status to healthcare center, boosting the traditional medical model towards the new idea of Pervasive Healthcare. The practical implementation of such Smart-Health services requires an enabling technology, completely transparent to the user and with high degree of pervasiveness as low cost, long lifetime and low power consumption. In this regard, Radio Frequency Identification (RFID) technology can play a key role in the development and implementation of IoT-based personal Healthcare systems. A RFID tag, together with its identification code is in fact able to carry information about the tagged objects e.g. detecting the presence in the environment of gases or humidity when it is functionalized with special chemical compounds, or can be connected to sensors to monitor the temperature or other physical parameters. Moreover, these non-intrusive devices could be spread in the living environments, easily integrated inside clothes or embedded into implanted prosthesis, cardio-vascular stents, realizing in the latter case “augmented” devices able to take care of the human health “from the inside”. This Thesis, investigates the feasibility of passive UHF RFID implants in the human body with particular regard to the area of the limbs in which, normally are implanted orthopedic prostheses, as a result of fractures or degenerative diseases of the musculoskeletal system. The structure of the Thesis is the following: Part I (chapter 1) describes the key role of RFID technology in the implementation of a new model of healthcare in the frame of IoT with some examples of application in the monitoring of environmental parameters (temperature, presence of gases and humidity) and human behavior. The chapter 2 is devoted to the mathematical model to be applied for the analysis of the UHF-RFID radio channel consisting in a region of the human body wherein a passive tag is implanted. Part II investigates the performance of through-the-body channel with reference to a human torso and limb simulators (chapter 3) introducing power budget indicators to determine the feasibility and reliability of the wireless communications. In particular, with regard to implants in the limbs, the analysis will be enhanced by a campaign of measurements carried out on an experimental phantom manufactured with meat and bovine bone, and using a loop antenna as a reference (chapter 4). Part III of this work deals with the integration of a passive tag inside an orthopedic prosthesis (chapter 5). An intramedullary nail will be particularly considered in the analysis but the same considerations can be applied to other types of prosthesis. Also in this case the problem will be addressed either using both numerical simulations and experimental measurements on a prototype of the functionalized intramedullary nail inserted into a limb phantom.