Cellulose is the most abundant biopolymer in the world and the main component of paper. Modern society requires electronic devices to be more flexible and environmental friendly, which makes cellulose as a good candidate for the next generation of green electronics. However, lots of researches employed “paper-like” petroleum-based polymers to fabricate electronics rather than using real cellulose paper. Cellulose, as a representative of environmental friendly materials, caught into people's attention because of its sustainable nature, ease of functionality, flexibility and tunable surface properties, etc. There are some general challenges about using cellulose for electronics, such as its non-conductivity, porosity and roughness, but these features can be taken advantages of on certain occasions. This thesis focuses on the study of cellulose-based electronic devices by chemical or physical modification of microfibrillated cellulose (MFC). Particularly, three electronic devices were fabricated, including ionic diodes, electric double layer supercapacitors, pseudocapacitors. In addition, a rational design of dye-sensitized solar cell was investigated, although it was not directly cellulose-based, it led the way to the next generation of cellulose-based solar cells. The extraordinary physical and chemical properties of MFC were successfully leveled in those devices, in addition, inspiring and effective fabrication methods were proposed and carried out to solve the major problems faced by paper-based electronics, such as conductivity, flexibility, packaging and designs.

O presente trabalho trata do estudo do fatiamento de cristais de quartzo quanto as suas características e influências na fabricação de micro sistemas eletromecânicos (MEMS). A metodologia é iniciada pelo projeto estruturado de um MEMS, convergindo para um gerador energia elétrica do tipo energy harvest, capaz de gerar energia limpa, renovável, de escala reduzida (micro componente), de baixa potência e com vistas para aplicação comercial. Geração de energia tem se tornado um tema cada vez mais frequente, em especial energia para sistemas autônomos (wireless) aonde o uso de baterias é restritivo ou até mesmo inviável devido às dimensões e dificuldade de manutenção. A fabricação de MEMS é a etapa de maior investimento financeiro e por consequência, maior estudo. No caso do gerador de energia, a ênfase recai sobre os processos de corte, que consomem a maior parte do processo fabril. O objetivo do presente trabalho é avaliar o processo de corte abrasivo do quartzo e a influência dos defeitos impregnados pelo processo, sobre o desempenho de geradores de energia piezelétricos baseados em quartzo sintético e natural. Os processos de corte com uso de fita abrasiva (band saw) e disco abrasivo (dicing saw) se destacaram devido aos bons resultados, disponibilidade, produtividade e baixo custo. Procedimentos de corte também foram realizados em outros materiais - Alumina Policristalina 99,8% e Silício (111) - como estudo comparativo das características do mecanismo de remoção de material aplicado aos processos de corte abrasivos. Os parâmetros de corte foram trabalhados em busca de melhor qualidade, que significa redução da impregnação de falhas (principalmente, o chipping e backside chipping) e melhor acabamento das superfícies geradas pelo corte final. Foram obtidas peças nos planos AT, X, Y e Z, com espessuras a partir de 0,5 mm, segmentadas em larguras de 1 a 7 mm. / This work is a study of characteristics and influences of cutting process in manufacturing of microelectromechanical systems (MEMS) based on quartz single crystal. The methodology starts by the structured design of a MEMS device, converging to an electric power generator device, type energy harvest that generates clean energy, renewable, with small dimensions (micro component) and low power. Power generating has become a frequent topic, especially the power generation for wireless devices systems, which use of batteries can be restrictive or even impracticable because of dimensions and difficult of maintenance. The base of the study is the process manufacturing of MEMS, which is the major investment and because of this, the most studied stage. In the case of a power generator, the emphasis is on the cutting process that consumes most part of the work flow. The objective of this work is evaluate the abrasive cutting process of quartz and the influence of defects generated by the cutting process applied to the performance of piezoelectric power generators based on synthetic and natural quartz crystal. The abrasive cutting process of band saw and dicing saw were featured due availability and high productivity with low cost. Procedures of cutting were also applied in other materials - Alumina Polycrystalline 99,8% and Silicon (111) - as comparison for material removal mechanism in cutting process. The process parameters were optimized to reach better cutting quality, which means reduction in faults (mainly, chipping and backside chippings) and better surface finishing from cutting process. It was obtained pieces from AT, X, Y and Z cutting plans, with thickness starting from 0,5 mm and widths from 1 to 7 mm.

O presente trabalho trata do estudo do fatiamento de cristais de quartzo quanto as suas características e influências na fabricação de micro sistemas eletromecânicos (MEMS). A metodologia é iniciada pelo projeto estruturado de um MEMS, convergindo para um gerador energia elétrica do tipo energy harvest, capaz de gerar energia limpa, renovável, de escala reduzida (micro componente), de baixa potência e com vistas para aplicação comercial. Geração de energia tem se tornado um tema cada vez mais frequente, em especial energia para sistemas autônomos (wireless) aonde o uso de baterias é restritivo ou até mesmo inviável devido às dimensões e dificuldade de manutenção. A fabricação de MEMS é a etapa de maior investimento financeiro e por consequência, maior estudo. No caso do gerador de energia, a ênfase recai sobre os processos de corte, que consomem a maior parte do processo fabril. O objetivo do presente trabalho é avaliar o processo de corte abrasivo do quartzo e a influência dos defeitos impregnados pelo processo, sobre o desempenho de geradores de energia piezelétricos baseados em quartzo sintético e natural. Os processos de corte com uso de fita abrasiva (band saw) e disco abrasivo (dicing saw) se destacaram devido aos bons resultados, disponibilidade, produtividade e baixo custo. Procedimentos de corte também foram realizados em outros materiais - Alumina Policristalina 99,8% e Silício (111) - como estudo comparativo das características do mecanismo de remoção de material aplicado aos processos de corte abrasivos. Os parâmetros de corte foram trabalhados em busca de melhor qualidade, que significa redução da impregnação de falhas (principalmente, o chipping e backside chipping) e melhor acabamento das superfícies geradas pelo corte final. Foram obtidas peças nos planos AT, X, Y e Z, com espessuras a partir de 0,5 mm, segmentadas em larguras de 1 a 7 mm. / This work is a study of characteristics and influences of cutting process in manufacturing of microelectromechanical systems (MEMS) based on quartz single crystal. The methodology starts by the structured design of a MEMS device, converging to an electric power generator device, type energy harvest that generates clean energy, renewable, with small dimensions (micro component) and low power. Power generating has become a frequent topic, especially the power generation for wireless devices systems, which use of batteries can be restrictive or even impracticable because of dimensions and difficult of maintenance. The base of the study is the process manufacturing of MEMS, which is the major investment and because of this, the most studied stage. In the case of a power generator, the emphasis is on the cutting process that consumes most part of the work flow. The objective of this work is evaluate the abrasive cutting process of quartz and the influence of defects generated by the cutting process applied to the performance of piezoelectric power generators based on synthetic and natural quartz crystal. The abrasive cutting process of band saw and dicing saw were featured due availability and high productivity with low cost. Procedures of cutting were also applied in other materials - Alumina Polycrystalline 99,8% and Silicon (111) - as comparison for material removal mechanism in cutting process. The process parameters were optimized to reach better cutting quality, which means reduction in faults (mainly, chipping and backside chippings) and better surface finishing from cutting process. It was obtained pieces from AT, X, Y and Z cutting plans, with thickness starting from 0,5 mm and widths from 1 to 7 mm.

The declining cost of photovoltaic (PV) modules has enabled the vision of ubiquitous photovoltaic (PV) power to become feasible. Emerging PV technologies are facilitating the creation of intentionally non-flat PV modules, which create new applications for this sustainable energy generation currently not possible with the traditional rigid, flat silicon-glass modules. However, since the photovoltaic cells are no longer coplanar, there are significant new requirements for the power electronics necessary to convert the native form of electricity into a usable form and ensure maximum energy harvest. Non-uniform insolation from cell-to-cell gives rise to non-uniform current density in the PV material, which limits the ability to create series-connected cells without bypass diode or other ways to shunt current, which is well known in the maximum power tracking literature. This thesis presents a modeling approach to determine and quantify the variations in generation of energy due to intentionally non-flat PV geometries. This will enable the power electronics circuitry to be optimized to harvest maximum energy from PV pixel elements – clusters of PV cells with similar operating characteristics. This thesis systematically compares different geometries with identical two-dimensional projection "footprints" for energy harvest throughout the day. The results show that for the same footprint, a semi-cylindrical surface harvests more energy over a typical day than a flat plate. The modeling approach is then extended to demonstrate that by using non flat geometries for PV panel, the availability of a remotely located stand-alone power system can be increased when compared to a flat panel of same footprint. These results have broad application to a variety of energy scavenging scenarios in which either total energy harvested needs to be maximized or unusual geometries for the PV active surfaces are required, including building-integrated PV. This thesis develops the analysis of the potential energy harvest gain for advanced non-planar PV collectors as a necessary first step towards the design of the power electronics circuits and control algorithms to take advantage of the new opportunities of conformal and non-flat PV collectors.

In this study, with near-field electrospinning technique of PVDF (Polyvinylidene fluoride) piezoelectric nano-fibers and the additional multiwalled-carbon nanotubes(MWCNT), both mechanical strength and piezoelectric characteristics of a single nano-fiber were discussed. Then the behavior of piezoelectric fiber actuators was realized using inverse piezoelectric effect. Near-field electrostatic technology can be used to fabricate PVDF piezoelectric fibers with an excellent piezoelectric property compared with film structures due to a higher piezoelectric coefficient and energy conversion efficiency. It is more suitable to produce micro transducers. By adjusting velocity of a fully parametric x-y stage, DC voltage, and the distance between the needle and collection plate, the morphology and polarization intensity of piezoelectric fiber can fully be controlled. In addition, the optimal parameters of PVDF solution such as PVDF powder weight percentage and MWCNT were also discussed. From the observation of XRD (X-ray diffraction), it reveals a high diffraction peak at 2£c=20.8¢X of piezoelectric crystal £]-phase structure. Finally, the actuation property was tested using DC voltage supply, and fiber has significant deflection in the experiment. The vertical deflection can be observed and compared with model solution of piezoelectric cantilever structure. In the fiber¡¦s direct piezoelectric effect, the result shows that fiber can produce an open circuit voltage of 15mV under a low frequency vibration of 7Hz.

This study used electrospinning to fabricate a polyvinylidene fluoride (PVDF) piezoelectric nanofiber harvesting device with interdigitated electrode to capture ambient energy. According to d33 mechanical-electric energy conversion mode, the energy harvesting device can be applied on the low frequency ambient vibration and impact abilities for the transformation mechanical energy into electrical energy effectively. First, the PVDF powder was mixed in acetone solution uniformly and the dimethyl sulfoxide (DMSO) was mixed with multi-walled carbon nanotube (MWCNT) to prepare PVDF macromolecular solution. The mixed solution was filled in a metals needle injector and contacted hundreds of voltage. After the PVDF drop in the needle was subjected to high electric field, the drop overcame surface tension of the solution itself, then extremely fine PVDF fiber was formed and spun out. The electrospun was collected orderly using X-Y digital control stage and the linear diameter of electrospun can be controlled easily by adjusting the travelling speed of the stage. In the spinning process, as affected by stretching strain and electric field at the same time, the PVDF piezoelectric fiber resulted in electric polarization and transformed £] piezoelectric crystal phase, in which the dipoles are oriented in the same direction. Furthermore, MWCNT was added to improve the mechanical properties of fiber and increase £] phase, to enhance the tensile strength and piezoelectric property of PVDF fiber effectively. Finally, the photolithography was used to fabricate interdigitated electrodes with 100£gm gap on the flexible PI substrate. The PVDF fibers, with a length and diameter of approximately 1cm and 700-1000nm, were aligned on interdigitated electrodes and packaged with the PI film. In order to increase the conversion efficiency of piezoelectric fiber in d33 mode, the PVDF fibers were repolarized in a high electric field. The results showed that the PVDF fiber energy harvesting device can generate 15mV open-circuit voltage under low frequency vibration of 4Hz and generate above 30mV open-circuit voltage under 6Hz vibrations. As compared with the piezoelectric fiber not repolarized by interdigitated electrode, its output voltage was increased by1- 2 times.

L'objet de l'étude menée vise la récupération de micro-énergie renouvelable au moyen des matériaux piézoélectriques, pyroélectriques et thermoélectriques. Cette étude porte sur l'optimisation de trois aspects de la récupération de micro-énergie : (i) le couplage entre le générateur et l'environnement, (ii) l'efficacité de conversion d'énergie par le choix adéquat de matériaux et (iii) l'extraction de l'énergie électrique. Des études expérimentales et théoriques ont été menées en premier lieu dans des conditions de laboratoire pour une meilleure compréhension des phénomènes de récupération de micro-énergie, puis dans des conditions réelles pour vérifier les performances effectives des dispositifs réalisés. Concernant l'effet thermoélectrique, une nouvelle méthode de récupération de micro-énergie ambiante et solaire est présentée. Cette méthode utilise les générateurs thermoélectriques et les effets des chaleurs sensibles et latentes des matériaux à changement de phase pour produire des micro-énergies aussi bien de jour que de nuit. Une puissance maximale de 1Wm-2 avec un matériau thermoélectrique (Bi2Te3) a été obtenue. Concernant l'effet pyroélectrique, l'effet des variations des vitesses du vent au cours du temps est exploité. Une variation temporelle maximale de la température de 16°C/mn est disponible, ce qui a conduit à une puissance moyenne récupérée de 0.6mWm-2. Concernant l'effet piézo-électrique, une structure mécanique de type harmonica a été développée ainsi qu'une estimation des efforts d'interaction fluide-structure. Le prototype développé fonctionne à partir des vitesses du vent de 2ms-1 et génère une production d'énergie électrique de 8.9mWm-2. A titre d'illustration, une application typique a été présenté (refroidissement de panneau photovoltaïque). Elle montre une augmentation de la production d'électricité autour de 10%. L'application met en évidence l'utilisation des micro-énergies renouvelables au service de la production de macro-énergie. / The aim of this study is to investigate ambient energy harvesting with coupling effect of piezoelectric, pyroelectric and thermoelectric materials. Three basic problems lie in an energy harvesting process with these coupling effects: (i) design and optimize a structure which is able to accumulate the micro-power from the energy source and transform it into the favorable loading on the active material, (ii) improve the energy conversion efficiency according to the suitable choice of material properties and (iii) develop an energy harvesting circuit which is able to improve the energy conversion efficiency. The developed approach was experimental and numerical studies at first in laboratory conditions for deep understanding of energy harvesting process and then in outside conditions for verifying actual performance of the realized devices. On the thermoelectric coupling effect, a new method of harvesting solar and ambient energy is presented. The method is based on thermoelectric and both sensitive and latent heat effects for energy harvesting day and night. A maximum power generation of 1Wm-2 is achieved with thermoelectric material (Bi2Te3). On the pyroelectric effect, the inherent fluctuation with time of the natural wind speed was used. A maximum time variation of temperature of 16°C/minute was achieved which corresponds to an average power of 0.6mWm-2. On the piezoelectric effect, a mechanical structure which is enlightened from harmonica was developed and dynamic fluid-structure problems were addressed. The developed prototype begins to work for wind speed around 2ms-1 and a maximum power generation of 8.9mWm-2 was achieved. Ultimately, a typical building application (automatic control of water cooling photovoltaic panel) with the harvested solar thermal energy is introduced. The proposed application highlights an example of using harvested micro-energy to improve macro-energy production (around 10%).

Abstract Many electrical devices already surround us in our everyday life. Some devices monitor car performance and traffic while others exist in handheld devices used by the general public. Electrical devices also control manufacturing processes and protect workers from exposure to hazardous working environment. All these devices require electricity to operate. This exponential growth of low power electronic devices in industry, healthcare, military, transportation and in portable personal devices has led to an urgent need for system integrated energy sources. Many energy harvesting technologies have been developed to serve as a power source in close proximity to the electrical device itself. Solar and magnetic energy harvesters are the most common solutions when conditions are suitable. A more recent technique, called piezoelectric energy harvesting, has raised significant interest among scientists and in industry. Through piezoelectric (ceramic) material mechanical energy can be harvested and converted to electrical energy. This method requires accurate analysis of the kinetic energy experienced by the piezoelectric material so that the mechanics can be suitably designed. At the same time the mechanical design has to protect the piezoelectric material from intense forces that might cause cracks, while still transmitting the kinetic energy efficiently. These requirements usually mean a specific energy harvest design for each ambient energy source at hand. This thesis is focused on energy harvesting from low frequency compressions using piezoelectric ceramic materials. The objective was to manufacture, measure and implement structures that could sustain the forces experienced under the heel of a foot and maximize the harvested energy amount and efficiency. Two different construction designs were developed and optimised with an iterative process. The kinetic energy impulse under the heel part of the foot was studied by measuring the electrical output of the harvester during walking and then analysed with modelling software. The results were used to create a walking profile for a computer controlled piston to study the input energy phase, speed and force influence on the amount of the harvested energy and the efficiency of the harvesting process. Finally, the functionality of the concept was tested in a real environment with an energy harvester inserted inside a running shoe. The developed harvester showed the highest energy density reported in this frequency region. / Tiivistelmä Monet elektroniset laitteet ympäröivät meitä jokapäiväisessä elämässä. Ne tarkkailevat auton toimintaa tai liikennettä ja toiset toimivat aina mukana kulkevissa kannettavissa laitteissa. Töissä ne valvovat valmistusprosesseja tai varoittavat työntekijöitä vaarallisista työolosuhteista. Kaikki nämä laitteet tarvitsevat sähköä toimiakseen. Pienitehoisten elektronisten laitteiden eksponentiaalinen kasvu teollisuudessa, terveyssektorilla, puolustusteollisuudessa, kulkuneuvoissa sekä kannettavassa kulutuselektroniikassa on johtanut suureen tarpeeseen kehittää järjestelmiin integroituja energialähteitä. Monia energiankeräystekniikoita on kehitetty toimimaan elektronisten laitteiden läheisyydessä. Aurinkopaneelit ja magneettiset energiankeräysmenetelmät ovat yleisimpiä ratkaisuja, jos olosuhteet antavat siihen mahdollisuuden. Pietsosähköinen energiankeräys on uudempi tekniikka, joka on herättänyt kasvavaa huomiota tutkimusyhteisössä sekä teollisuudessa. Pietsosähköisen materiaalin avulla mekaaninen energia voidaan muuntaa suoraan sähköiseksi energiaksi. Tässä tekniikassa kineettinen energia tulee analysoida tarkasti mekaniikka suunnittelua varten, jotta se saadaan kohdistettua tehokkaasti pietsosähköiseen materiaaliin. Lisäksi mekaniikan tulee suojata materiaalia voimilta, jotka voivat johtaa murtumiin. Näistä vaatimuksista johtuen jokainen ulkoinen energialähde vaatii yleensä yksilöllisen energiankeräysrakenteen. Tämä väitöstyö keskittyy pietsosähköisten keraamien hyödyntämiseen energiankeräyksessä matalataajuisista mekaanisista voimista. Tarkoituksena oli suunnitella, valmistaa, mitata ja asentaa rakenteita, jotka kestävät kantapäähän kohdistuvia voimia kävelyn ja juoksun aikana sekä maksimoida talteen saatava energia ja hyötysuhde. Kaksi erilaista rakennetta suunniteltiin, valmistettiin ja optimoitiin energiankeräystä varten. Kantapäähän kohdistuva kineettinen energia analysoitiin mallinnusohjelmistolla ja mittaamalla sähköinen vaste energiakeräys rakenteesta. Tuloksien avulla suunniteltiin kävelyprofiilia imitoiva mekaaninen männän liike, jonka avulla tutkittiin kohdistettavan voiman nopeuden, vaiheen ja suuruuden vaikutusta energiankeräyksen hyötysuhteeseen ja saatavaan tehoon. Viimeisenä energiankeräysrakenteen toimivuutta testattiin oikeassa ympäristössä asentamalla se juoksukenkään. Kehitetyllä pietsosähköisellä energiakeräimellä saavutettiin korkeimmat raportoidut energiatiheydet käytetyllä taajuusalueella.

Energy Harvesting from Exercise Machines (EHFEM) is an ongoing project pursuing alternate forms of sustainable energy for Cal Poly State University. The EHFEM project seeks to acquire user-generated DC power from exercise machines and sell that energy back to the local grid as AC power. The end goal of the EHFEM project aims to integrate a final design with existing elliptical fitness trainers for student and faculty use in Cal Poly’s Recreational Center. This report examines whether including the DC-DC converter in the EHFEM setup produces AC power to the electric grid more efficiently and consistently than an EHFEM system that excludes a DC-DC converter. The project integrates an overvoltage protection circuit, a DC-DC converter, and a DC-AC microinverter with an available elliptical trainer modified to include an energy converting circuit. The initial expectation was that a DC-DC converter would increase, when averaged over time, the overall energy conversion efficiency of the EHFEM system, and provide a stable voltage and current level for the microinverter to convert DC power into AC power. In actuality, while including a DC-DC converter in a test setup allows the EHFEM system to function with less frequent interruptions, this occurs at the cost of lower efficiency. Testing demonstrates the EHFEM project can convert user-generated DC mechanical power into usable AC electrical power. Retrofitting existing equipment with the EHFEM project can reduce Cal Poly’s energy cost.

This research investigates lower-power lower-voltage analog circuit techniques suitable for wireless sensor applications. Wireless sensors have been used in a wide range of applications and will become ubiquitous with the revolution of internet of things (IoT). Due to the demand of low cost, miniature desirable size and long operating cycle, passive wireless sensors which don't require battery are more preferred. Such sensors harvest energy from energy sources in the environment such as radio frequency (RF) waves, vibration, thermal sources, etc. As a result, the obtained energy is very limited. This creates strong demand for low power, lower voltage circuits. The RF and analog circuits in the wireless sensor usually consume most of the power. This motivates the research presented in the dissertation. Specially, the research focuses on the design of a low power high efficiency regulator, low power Resistance to Digital Converter (RDC), low power Successive Approximation Register (SAR) Analog to Digital Converter (ADC) with parasitic error reduction and a low power low voltage Low Dropout (LDO) regulator. This dissertation includes a low power analog circuit design for the RFID wireless sensor which consists of the energy harvest circuits (an optimized rectifier and a regulator with high current efficiency) and a sensor measurement circuit (RDC), a single end sampling SAR ADC with no error induced by the parasitic capacitance and a digital loop LDO whose line and load variation response is improved. These techniques will boost the design of the wireless sensor and they can also be used in other similar low power design.