Lead-free Piezoelectric Microgenerator for Energy Autonomous Wireless Sensors ; Microgenerateurs piezoelectriques sans plomb pour capteurs autonomes sans fils

Open Access

Abstract

The overall aim of this PhD work is the investigation of the harvest of power from ambient vibrations at relatively low frequencies < 500 Hz using lead free piezoelectric materials in order to power low power sensors or actuators that are used in the "Internet of things" IOT networks. The rapid growth of communication and information Technology (IT), along with the progress in the semiconductor industry in recent times, has generated growing interest in the field of IoT. The IOT concept comprises of "Smart Structures" with autonomous self-powered sensors, actuators and associated low-power electronics circuits that is spread across a network of wireless sensor nodes (WSNs) that can sense and share data among one another and the master unit. In order to make it fully autonomous it is very important that they are powered independently and therefore it is challenging to replace the depleted energy in the batteries. In this situation, the use of ubiquitous ambient mechanical vibrations to generate electricity for powering the WSNs is a promising choice.Among the various transduction mechanisms to convert vibrational energy to electric energy, piezoelectric transduction has drawn considerable attention because of its simplicity in structure, high energy density and good compatibility with micro/nano fabrication techniques. However, the mostly used high performing piezoelectric ceramics such as Lead Zirconate Titanate (PZT) contains lead which is hazardous. Recently, the European Union has also implemented the Restriction of Hazardous Substances legislation, that has set a strict standard restricting the use of lead-based piezoelectric materials in future electronic devices. This thesis will therefore investigate about novel lead-free materials as a potential candidate for high performance energy harvesting devices. This thesis begins with the basic introduction to the energy harvesting at microscale to power IOT nodes, followed by the chapter on piezoelectric materials and the extraction of their basic properties ...