Design Of Resonant Piezoelectric Devices PDF Download

All electronic devices need power sources to perform their functions including computing, communication, and sensing. Traditional high-capacity and long-lifetime batteries have a drawback of being bulky and face challenges for implementation and integration into today's increasingly miniaturized devices such as many portable devices and microelectromechanical systems (MEMS). Directly harvesting energy from environments is a very attractive approach to supplying energy for low-power electronics and sensors. In recent years, many materials and techniques for harvesting ambient energy to power electronic devices have been explored. After a comprehensive survey of existing energy harvesting techniques, we choose to focus on investigating the conversion of mechanical vibrations to electricity by using piezoelectric devices. In this active research area, currently there are a number of important open challenges, including how to achieve highest possible energy conversion efficiency, and how to demonstrate novel practical applications. This thesis work first investigates and validates the fundamentals of resonant-mode piezoelectric energy harvesting to gain understandings of design principles toward achieving high energy conversion efficiency. We then design devices and circuits to demonstrate using spectra-selective energy harvesting to power up optoelectronic devices for solid-state lighting in ambient air.We first describe measurement and modeling of energy harvesters based on oscillating piezoelectric cantilevers, along with careful calibration of energy conversion properties of such devices in their dynamic response. We employ thin-film lead zirconate titanate (PZT)-based cantilevers fabricated by laser micromachining, with efficient proof masses enabled by a heavy alloy with a low melting temperature (65°C) for tuning frequency and damping. By measuring devices with different circuit parameters, and analyzing the energy conversion in time-domain oscillations, we show a model that quantitatively reveals the effects of the loading circuit for energy harvesting. We also show the effects of device dimensions on their vibrations and converted voltage output waveforms. In harvesting vibrational energy through cycles of oscillations (in 80Hz-1 kHz devices), we obtained a 25% energy conversion efficiency. After carefully studying the principles of the PZT cantilevers, we demonstrate a miniature system on a circuit board for harvest vibrational energy from a small service pump. The miniature system features resonance-matched designs of the cantilevers, and the integration with a full-wave rectifying circuit and a smoothing capacitor in a less than 1cm2 area. The system is calibrated to have a power generation density of 173.6μW/mm3 is demonstrated to be capable of lighting up a blue LED using the harvested vibrational energy.