CIRCUITI E SISTEMI DI ENERGY HARVESTING ELETTROMAGNETICO RF, TERMICO E BIOMECCANICO PER SENSORI AUTONOMI E DISPOSITIVI BIOMEDICI INDOSSABILI

In recent years, the development of electronics and information technology can be considered among the protagonists of social growth and technological progress, now essential for everyday life. The growing number of applications that require global connectivity is going hand in hand with the increasing demand for portable devices, such as in the IoT (Internet of Things) environment, for the distributed monitoring of environmental parameters, the use of wearable devices for human well-being and health or for sports and leisure activities. These devices need a portable and long-lasting source of energy, reliable over time to guarantee prolonged self-sufficiency as much as possible. Historically, batteries have always been considered the only, indispensable energy source in applications for mobile devices, embedded systems, and remote systems; the use of batteries is, however, constraining for many factors, first of all, the limited capacity to supply energy over time, with consequent need for maintenance for replacement or recharging. Although great strides have recently been made on the development of ever more efficient batteries, both in terms of materials and process, and new electronic technologies are moving towards reducing consumption, to date the use of batteries is still limiting in terms of energy supply over time, for various portable applications. In this scenario, the activity of this dissertation focuses on the research and development of energy recovery systems from alternative sources, with reduced environmental impact, which can guarantee potentially unlimited autonomy for low-power portable devices, or standalone autonomous sensors, together with eco-sustainability. In particular, the research carried out focuses on the design and implementation of energy harvesting (EH) systems, single-source or multi-source, for the energy support of wearable devices in the biomedical field and for autonomous sensors used in wireless networks, for example for the widespread and distributed monitoring of the environment. After the introduction to the topic, a chapter dedicated to the review of the literature and the state of the art follows. This step is fundamental, as in any research activity, to identify the various existing techniques as well as the materials used for energy recovery and, moreover, it is fundamental to understand the current problems and limitations that require further analysis and in-depth studies. From this initial review, the main circuit blocks constituting the energy processing chain have been identified and analyzed. The literature review is followed by the author's contributions to RF electromagnetic, Thermoelectric and biomechanical energy harvesting. In particular, chapter 3 is focused on novel design methods for multi-antenna, multi-band and multi-channel power harvester for autonomous sensors and wearables, as well as practical considerations about matching network and antenna design for RF energy harvesting in the field of biomedical applications. Following, chapter 4 introduces the research works centered on thermoelectric and biomechanical energy harvesting. Specifically, the analysis and design methods of the human body’s heat thermoelectric energy harvesting are investigated ad discussed, as well as the possibility to recover the body motion energy by means of piezoelectric transducers. An example of a multisource energy harvesting system design is also presented and discussed. Finally, chapter 5 summarizes the findings and original contributions of this research. Suggestions for further work in this area are then given.