Kinetic Energy Harvesting for Wearable Medical Sensors

The process of collecting low-level kinetic energy, which is present in all moving systems, by using energy harvesting principles, is of particular interest in wearable technology, especially in ultra-low power devices for medical applications. In fact, the replacement of batteries with innovative piezoelectric energy harvesting devices can result in mass and size reduction, favoring the miniaturization of wearable devices, as well as drastically increasing their autonomy. The aim of this work is to assess the power requirements of wearable sensors for medical applications, and address the intrinsic problem of piezoelectric kinetic energy harvesting devices that can be used to power them; namely, the narrow area of optimal operation around the eigenfrequencies of a specific device. This is achieved by using complex numerical models comprising modal, harmonic and transient analyses. In order to overcome the random nature of excitations generated by human motion, novel excitation modalities are investigated with the goal of increasing the specific power outputs. A solution embracing an optimized harvester geometry and relying on an excitation mechanism suitable for wearable medical sensors is hence proposed. The electrical circuitry required for efficient energy management is considered as well.publishedVersionPeer reviewe

Electromechanical Properties of 3D Multifunctional Nano-Architected Materials

In this thesis, we explore the fabrication and characterization of 3D architected multifunctional materials in three different categories: varied density for tailored mechanical response, stiff ultra low-k dielectric materials, and direct laser writing of piezoelectric structures at the micron scale. The density of an architected material plays a large role in determining its effective Young’s modulus, strength, and deformation behavior. The first section of this work explores the effect of incorporating two density regions into hollow nanolattices, which results in two distinct mechanical response regions for horizontal interfaces and a combined varying response for a diagonal interface. The second section of this work describes low dielectric constant (low-k) materials, which have gained increasing popularity because of their critical role in developing faster, smaller, and higher performance devices. We report the fabrication of 3D nanoarchitected hollow-beam alumina dielectrics with a k value of 1.06 - 1.10 at 1 MHz that is stable over the voltage range of -20 to 20 V and a frequency range of 100 kHz to 10 MHz, with an effective Young’s modulus of 30 MPa, a strength of 1.07 MPa, a nearly full shape recoverability to its original size after &gt;50% compressions, and outstanding thermal stability with a thermal coefficient of dielectric constant (TCK) of 2.43 x 10-5K-1 up to 800° C. Finally, we report the fabrication of monolithic piezoelectric ZnO structures of arbitrary shape via a polymer complex route. We have confirmed the microstructure using XRD, TEM, and SAED, and have observed its electromechanical response using a novel in-situ experiment.</p

Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

Study, optimization and silicon implementation of a smart high-voltage conditioning circuit for electrostatic vibration energy harvesting system

La récupération de l'énergie des vibrations est un concept relativement nouveau qui peut être utilisé dans l'alimentation des dispositifs embarqués de puissance à micro-échelle avec l'énergie des vibrations omniprésentes dans l environnement. Cette thèse contribue à une étude générale des récupérateurs de l'énergie des vibrations (REV) employant des transducteurs électrostatiques. Un REV électrostatique typique se compose d'un transducteur capacitif, de l'électronique de conditionnement et d un élément de stockage. Ce travail se concentre sur l'examen du circuit de conditionnement auto-synchrone proposé en 2006 par le MIT, qui combine la pompe de charge à base de diodes et le convertisseur DC-DC inductif de type de flyback qui est entraîné par le commutateur. Cette architecture est très prometteuse car elle élimine la commande de grille précise des transistors utilisés dans les architectures synchrones, tandis qu'un commutateur unique se met en marche rarement. Cette thèse propose une analyse théorique du circuit de conditionnement. Nous avons développé un algorithme qui par commutation appropriée de flyback implémente la stratégie de conversion d'énergie optimale en tenant compte des pertes liées à la commutation. En ajoutant une fonction de calibration, le système devient adaptatif pour les fluctuations de l'environnement. Cette étude a été validée par la modélisation comportementale.Une autre contribution consiste en la réalisation de l'algorithme proposé au niveau du circuit CMOS. Les difficultés majeures de conception étaient liées à l'exigence de haute tension et à la priorité de la conception faible puissance. Nous avons conçu un contrôleur du commutateur haute tension de faible puissance en utilisant la technologie AMS035HV. Sa consommation varie entre quelques centaines de nanowatts et quelques microwatts, en fonction de nombreux facteurs - paramètres de vibrations externes, niveaux de tension de la pompe de charge, la fréquence de la commutation de commutateur, la fréquence de la fonction de calibration, etc.Nous avons également réalisé en silicium, fabriqué et testé un commutateur à haute tension avec une nouvelle architecture de l'élévateur de tension de faible puissance. En montant sur des composants discrets de la pompe de charge et du circuit de retour et en utilisant l'interrupteur conçu, nous avons caractérisé le fonctionnement large bande haute-tension du prototype de transducteur MEMS fabriqué à côté de cette thèse à l'ESIEE Paris. Lorsque le capteur est excité par des vibrations stochastiques ayant un niveau d'accélération de 0,8 g rms distribué dans la bande 110-170 Hz, jusqu'à 0,75 W de la puissance nette a été récupérée.Vibration energy harvesting is a relatively new concept that can be used in powering micro-scale power embedded devices with the energy of vibrations omnipresent in the surrounding. This thesis contributes to a general study of vibration energy harvesters (VEHs) employing electrostatic transducers. A typical electrostatic VEH consists of a capacitive transducer, conditioning electronics and a storage element. This work is focused on investigations of the reported by MIT in 2006 auto-synchronous conditioning circuit, which combines the diode-based charge pump and the inductive flyback energy return driven by the switch. This architecture is very promising since it eliminates precise gate control of transistors employed in synchronous architectures, while a unique switch turns on rarely. This thesis addresses the theoretical analysis of the conditioning circuit. We developed an algorithm that by proper switching of the flyback allows the optimal energy conversion strategy taking into account the losses associated with the switching. By adding the calibration function, the system became adaptive to the fluctuations in the environment. This study was validated by the behavioral modeling. Another contribution consists in realization of the proposed algorithm on the circuit level. The major design difficulties were related to the high-voltage requirement and the low-power design priority. We designed a high-voltage analog controller of the switch using AMS035HV technology. Its power consumption varies between several hundred nanowatts and a few microwatts, depending on numerous factors - parameters of external vibrations, voltage levels of the charge pump, frequency of the flyback switching, frequency of calibration function, etc. We also implemented on silicon, fabricated and tested a high-voltage switch with a novel low power level-shifting driver. By mounting on discrete components the charge pump and flyback circuit and employing the proposed switch, we characterized the wideband high-voltage operation of the MEMS transducer prototype fabricated alongside this thesis in ESIEE Paris. When excited with stochastic vibrations having an acceleration level of 0.8 g rms distributed in the band 110-170 Hz, up to 0.75 $\mu$W of net electrical power has been harvested.PARIS-JUSSIEU-Bib.électronique (751059901) / SudocSudocFranceF

Nonlinear vibration energy harvesters for powering the internet of things

The ever decreasing power consumption in electronic devices and sensors have facilitated the development of autonomous wireless sensor nodes (WSNs), which ushered in the era of the Internet of Things (IoT). However, the problem of long-term power supply to the numerous WSNs pervasively dispersed to enable the IoT is yet to be resolved. This work focuses on the development of novel vibration energy harvesting (VEH) devices and technologies for effective transduction of mostly wide-band and noisy ambient mechanical vibrations to power WSNs. In this thesis meso-scale and MEMS-scale nonlinear and frequency tunable VEH devices have been designed, fabricated and characterized. The first meso-scale VEH prototype developed in this thesis combines a nonlinear bistable oscillator with mechanical impact induced nonlinearity, which exhibits upto 118% broadening in the frequency response over a standalone bistable system. The second meso-scale prototype combines magnetic repulsion induced bistable nonlinearity with stretching induced monostable cubic nonlinearity in a single device structure. The device effectively merged the beneficial features of the individual nonlinear bistable and monostable systems, and demonstrates upto 85% enhanced spectral performance compared to the bistable device. The third prototype is a MEMS-scale device fabricated using spiral silicon spring structure and double-layer planar micro-coils. A magnetic repulsion induced frequency tuning mechanism was incorporated in the prototype, and it was demonstrated that both linear and nonlinear hysteretic frequency responses could be tuned (by upto 18.6%) to match various ambient vibration frequencies. In order to enhance the power generating capability of MEMS-scale electromagnetic devices, an ultra-dense multi-layer micro-coil architecture has been developed. The proposed ultra-dense micro-coil is designed to incorporate double number of turns within the same volume as a conventional micro-coil, and significantly enhance the magnetic flux linkage gradient resulting in higher power output (~4 times). However, attempts to fabricate the ultra-dense coil have not been successful due to lack of proper insulation between the successive coil layers. Finally, a power management system combining diode equivalent low voltage drop (DELVD) circuit and a boost regulator module was developed. It was demonstrated that energy harvested from harmonic and bandlimited random vibrations using linear, nonlinear bistable, and combined nonlinear VEH devices could be conditioned into usable electricity by the power management system with 60% - 75% efficiency. In addition to developing new prototypes and techniques, this thesis recommends directions towards future research for further improvement in vibration energy harvesting devices and technologies