Piezoelectric energy harvester has become a new powering choice for small electronic device. Due to its piezoelectric effect, electric energy can be obtained from ambient vibrations. This thesis is intending to build a frequency-adjustable piezoelectric energy harvester system. The system is structured with two piezoelectric bimorph beams, which are connected to each other by a spring. The feasibility of the frequency-adjustable piezoelectric energy harvester has been proved by investigating effects of the spring, loading mass and impedance on the operation frequencies.

Small and efficient energy harvesters, as a renewable power supply, draw lots of attention in last few years. This thesis presents a planar rotary electromagnetic generator with copper coils fabricated by printed circuit board (PCB) as inductance and Nd-Fe-B magnets as magnetic member. Coils are fabricated on PCB, which is presumably cost-effective and promising methods. 28-pole Nd-Fe-B magnets with outer diameter of 50 mm and thickness of 2 mm was sintered and magnetized, which can provide magnetic field of 1.4 Tesla. This harvester consists of planar multilayer with multi-pole coils and multi-pole permanent magnet, and the volume of this harvester is about 50x50x2.5 mm3. Finite element analysis is used to design energy harvesting system, and simulation model of the energy harvester is established. In order to confirm the simulation, experiment data are compared with simulation result. The PCB energy harvester prototype can generate induced voltage 1.11 V and 26.54mW output power at rotary speed of 4,000 rpm, and the efficiency of this energy harvester is 31.5%.

Sufficient power supply to run GPS machinery and transmit data on a long-term basis remains to be the key challenge for wildlife tracking technology. Traditional ways of replacing battery periodically is not only time and money consuming but also dangerous to live-trapping wild animals. In this paper, an innovative wildlife tracking collar with multi-source energy harvester with advantage of high efficiency and reliability is proposed. This multi-source energy harvester entails a solar energy harvester and an innovative rotational electromagnetic energy harvester is mounted on the "wildlife tracking collar" which will extend the duration of wild life tracking by 20% time as was estimated. A feedforward and feedback control of DC-DC converter circuit is adopted to passively realize the Maximum Power Point Tracking (MPPT) logic for the solar energy harvester. A novel electromagnetic pendulum energy harvester with motion regulator is proposed which can mechanically rectify the irregular bidirectional swing motion of the pendulum into unidirectional rotational motion of the motor. No electrical rectifier is needed and voltage drops from diodes can be avoided, the EM pendulum energy harvester can provide 200~300 mW under the 0.4g base excitation of 4.5 Hz. The nonlinearity of the disengage mechanism in the pendulum energy harvester will lead to a broad bandwidth frequency response. Simulation results shows the broadband advantage of the proposed energy harvester and experiment results verified that at some frequencies over the natural frequency the efficiency is increased. / Master of Science

Piezoelectric energy harvesters in the road pavement are developed and studied to collect energy from the passing vehicles. A numerical model based on the Westergaard's stress model is proposed to calculate the three dimensional stress distribution in the pavement and the power generation from the piezoelectric harvesters placed inside the pavement. Piezoelectric patch, plate and beam harvesters are designed. Based on proposed numerical models, simulations are conducted to reveal the effects of vehicle velocity as well as the location and size of the Piezo-electric harvesters on the generated power. Optimally designed plate energy harvester attached with four cantilever harvesters generates up to around 28 W electrical power with the assumption of continuum vehicle passing the pavement by 22.2 m/s. This power can be used to collect enough energy in 2 hours to raise the ice temperature with the thickness of 1 cm, covering a 5 m wide road by 20 degree Celsius. / February 2017

Compressed sensing (CS) is an innovative approach of signal processing that facilitates sub-Nyquist processing of bio-signals, such as a neural signal, electrocardiogram (ECG), and electroencephalogram (EEG). This strategy can be used to lower the data rate to realize ultra-low-power performance, As the count of recording channels increases, data volume is increased resulting in impermissible transmitting power. This thesis work presents the implementation of a CMOS-based front-end design with the CS in the standard 180 nm CMOS process. A novel pseudo-random sequence generator is proposed, which consists of two different types of D flip-flops that are used for obtaining a completely random sequence. This thesis work also includes the (reverse electrowetting-on-dielectric) REWOD based energy harvesting model for self-powered bio-sensor which utilizes the electrical energy generated through the process of conversion of mechanical energy to electrical energy. This REWOD based energy harvesting model can be a good alternative to battery usage, particularly for the bio-wearable applications. The comparative analysis of the results generated for voltage, current and capacitance of the rough surface model is compared to that of results of planar surface REWOD.

This study investigates the vibration of a rotating piezoelectric device that consists of a proof mass that is supported by elastic structures with piezoelectric layers. Vibration of the proof mass causes deformation in the piezoelectric structures and voltages to power electrical loads. The coupled electromechanical equations of motion are derived using Newtonian mechanics and Krichhoff's circuit laws. The free vibration behavior is investigated for devices with identical (tuned) and nonidentical (mistuned) piezoelectric support structures and electrical loads. These devices complex-valued have speed-dependent eigenvalues and eigenvectors as a result of their constant rotation. The imaginary parts of the eigenvalues physically represent the oscillation frequencies of the device. The real parts represent the decay or growth rates of the oscillations, depending on their sign. The complex-valued components of the eigenvectors physically represent the amplitudes and phases of the vibration. The eigenvalue behaviors differ for tuned and mistuned devices. Due to gyroscopic effects, the proof mass in the tuned device only vibrates in either forward or backward decaying circular orbits in single-mode free response. This is proven analytically for all tuned devices. For mistuned devices, the proof mass has decaying elliptical forward and backward orbits. The eigenvalues are shown to be sensitive to changes in the electric load resistances. Closed-form solutions for the eigenvalues are derived for open and close circuits. At high rotation speeds these devices experience critical speeds and instability. Closed-form solutions for the critical speeds are derived. Tuned devices have one degenerate critical speed that separates stable speeds from unstable speeds, where flutter instability occurs. Mistuned devices have two critical speeds. The first critical speed separates stable speeds from speeds where divergence instability occurs. Divergence instability continues for small speeds above the second critical speed. At higher supercritical speeds flutter instability occurs. Transitions between stable and unstable eigenvalues are investigated using root locus diagram. This device has atypical eigenvalue behavior near the critical speeds and stability transitions compared to conventional gyroscopic systems.

Abstract The main objective of this thesis was to use and combine Finite Element Method (FEM) and small signal equivalent circuit models in actuator and energy harvesting design and to study the dynamics of the said designs. The work is divided into four different sections. In the first section, the small signal parameters are derived for a pre-stressed piezoelectric actuator using a series of measurements. In addition, the tunability of the resonance frequency using mass and series capacitors is investigated. In the second section, a piezoelectric Fabry Perot Interferometer actuator is simulated using FEM and the small signal parameters are derived using FEM simulations. The modelled results are compared with the actual measurements and the resonance frequency is found to differ by only 0.8 percent from the measured values when the mirror is attached to the actuator. In the third section a piezoelectric wide band energy harvester is developed with multiple beam topology. Two different designs are compared, one produced using the conventional PZT-steel structure and one with a PZT-LTCC structure. The final section presents an FEM model for a shoe mounted energy harvester and concentrates on the modelling of walking dynamics in FEM. The simulation results are compared to actual measurements and the simulated power values are found to differ by only 7% when the cymbal stroke is below 1.3 mm. The generated model is also expandable to other types of energy harvesters and the methods developed can be used in a variety of different energy harvesting simulations and harvester development. The results show that the equivalent circuit approach together with FEM modelling is a powerful tool in the dynamics design of piezoelectric actuators and energy harvesters. / Tiivistelmä Väitöstyön päätavoitteena oli yhdistää elementtimenetelmät (FEM) ja piensignaalimallit aktuaattorien ja energiankorjuukomponenttien suunnittelussa ja tutkia niiden dynamiikkaa. Työ on jaettu neljään eri osaan. Ensimmäisessä osassa piensignaalimallit johdettiin pietsosähköisestä aktuaattorista mittausten avulla. Lisäksi resonanssitaajuuden muuttamista tutkitaan massan ja sarjaan kytketyn kapasitanssin avulla. Toisessa osassa simuloidaan pietsosähköistä Fabry Perot interferometria käyttäen elementtimenetelmää. Lisäksi komponentin piensignaalimalli luodaan käyttäen simulointimallia. Lopuksi piensignaalimallin ja prototyypin mittaustuloksia verrataan. Mallin resonanssitaajuus poikkeaa mitatusta vain 0.8 %, kun aktuaattoriin on kiinnitetty peili. Kolmannessa osassa kehitetään ja verrataan toisiinsa kahta erilaista laajakaistaista monipalkkista pietsosähköistä energian korjuukomponenttia. Toinen komponenteista on toteutettu perinteisellä PZT-teräs rakenteella ja toinen yhteissintratulla PZT-LTCC rakenteella. Viimeisessä osassa luodaan simulaatio malli kenkään asennetulle cymbal tyyppiselle pietsosähköiselle energian korjuukomponentille ja kävelyn dynamiikkaa tutkitaan. Luotua mallia verrataan prototyypin mittaustuloksiin ja simuloitu energian tuotto poikkeaa vain 7 % alle 1.3 mm puristusliikkeellä. Tulokset osoittivat, että piensignaalimallin ja elementtimenetelmän yhdistäminen on tehokas apu pietsosähköisten aktuaattorien ja energiankorjuukomponenttien dynamiikan suunnittelussa.

Piezoelectric nanogenerators (PNGs) are a new class of energy harvesting materials that show potential as a direct energy source for low powered electronics. Recently, piezoelectric polymers have been utilized for PNG technology due to low toxicity, high flexibility, and facile solution processing which provide manufacturing opportunities such as screen printing. Throughout the last decade, countless projects have focused on how to enhance the energy harvesting capabilities of these PNGs through the incorporation of nanoparticle fillers, which have been reported to enhance the piezoelectric properties of the film either directly through their intrinsic piezoelectric properties or through acting as surfaces for the interfacial nucleation of piezoelectric polymer crystals. Herein, two systems of PNGs formed from piezoelectric copolymers poly(vinylidene fluoride-co-hexafluropropylene) or poly(vinylidene fluoride-co-trifluoroethylene) mixed with high aspect ratio zinc oxide nanowires, hydroxyl functionalized multi-walled carbon nanotubes, or carboxylic acid functionalized single walled carbon nanotubes were investigated. Variations of filler type and loading are tested to determine influences on film morphology and piezoelectric properties. Power harvesting tests are conducted to directly determine the effect of nanoparticle addition on the output power of the non-poled devices. Both copolymer systems are found to exhibit a non-linear increase in output power with the increase of nanoparticle filler loading. The crystal polymorph properties of both systems are investigated by Fourier transform infrared spectroscopy. The microstructure of the poly(vinylidene fluoride-co-trifluoroethylene) films are further examined using X-ray diffraction, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy to determine the mechanism behind the increased power harvesting capabilities. As well, explanations for perceived output power from “self-poled” films are briefly explored.

Many of the most pressing global challenges today and in the future center around the scarcity of sustainable energy and water sources. The innovative microbial fuel cell (MFC) technology addresses both as it utilizes bacteria to convert wastewaters into electricity. Advancing this technology requires a better understanding of the optimal materials, designs and conditions involved. The micro-sized MFC was recently developed to serve this need by providing a rapid testing device requiring only a fraction of the materials. Further, development of micro-liter scale MFCs has expanded into potential applications such as remote and self-sustained power sources as well as on-chip energy generators. By using microfabrication, the fabrication and assembly of microsized MFCs is potentially inexpensive and mass produced. The objective of the work within this dissertation was to explore and optimize the micro-sized MFC to maximize power and current generation towards the goal of a usable and application-oriented device. Micro-sized MFCs were examined and developed using four parameters/themes considered most important in producing a high power generating, yet usable device: Anode- The use of nano-engineered carbon nanomaterials, carbon nanotubes and graphene, as anode as well as testing semiconductor industry standard anode contact area materials for enhanced current production. 5 Cathode- The introduction of a membrane-less air cathode to eliminate the need for continuous chemical refills and making the entire device mobile. Reactor design- The testing of four different reactor designs (1-75 μLs) with various features intended to increase sustainability, cost-effectiveness, and usability of the microsized MFC. Fuels- The utilization of real-world fuels, such as industrial wastewaters and saliva, to power micro-sized MFCs. The micro-sized MFC can be tailored to fit a variety of applications by varying these parameters. The device with the highest power production here was designed to be an inexpensive and robust power source in applications like point-of-care diagnostics in developing countries. This 25 μL graphene nanomaterial anode, air cathode device in an inexpensive flexible rubber architecture was powered by saliva and achieved 3.55 μW/cm2 and 35.2 W/m3. The continued optimization of MFC technology promises many interesting and innovative applications.

Speed bump energy harvester, which aims to harvest energy from the passing by vehicles by absorbing their kinetic and potential energy, is designed, fabricated, simulated, and tested in this research. The proposed design is analyzed with a theoretical modelling which has then been validated with a ground test. Result reveals that the prototype has been able to produce up to 600 watts of peak power and around 150 watts of RMS power which is significant number. Further analysis has been done which theoretically suggests that the numbers could be increased up to 1 KW by optimizing the speed bump design and varying the system parameters such as electrical damping, mechanical damping, velocity and weight of the vehicles. Overall, system is able to increase the overall energy density by using Mechanical Motion Rectification (MMR) technology which would allow the increase in the power generation almost by double. Furthermore, different vehicle models have been used to analyze the effectiveness and accuracy of the harvester and also, the effect of harvester on the dynamics of the vehicle has been studied and analyzed in detail. / Master of Science