DEVELOPMENT OF A SIMPLIFIED, MASS PRODUCIBLE HYBRIDIZED AMBIENT, LOW FREQUENCY, LOW INTENSITY VIBRATION ENERGY SCAVENGER (HALF-LIVES)

Scavenging energy from environmental sources is an active area of research to enable remote sensing and microsystems applications. Furthermore, as energy demands soar, there is a significant need to explore new sources and curb waste. Vibration energy scavenging is one environmental source for remote applications and a candidate for recouping energy wasted by mechanical sources that can be harnessed to monitor and optimize operation of critical infrastructure (e.g. Smart Grid). Current vibration scavengers are limited by volume and ancillary requirements for operation such as control circuitry overhead and battery sources. This dissertation, for the first time, reports a mass producible hybrid energy scavenger system that employs both piezoelectric and electrostatic transduction on a common MEMS device. The piezoelectric component provides an inherent feedback signal and pre-charge source that enables electrostatic scavenging operation while the electrostatic device provides the proof mass that enables low frequency operation. The piezoelectric beam forms the spring of the resonant mass-spring transducer for converting vibration excitation into an AC electrical output. A serially poled, composite shim, piezoelectric bimorph produces the highest output rectified voltage of over 3.3V and power output of 145uW using ¼ g vibration acceleration at 120Hz. Considering solely the volume of the piezoelectric beam and tungsten proof mass, the volume is 0.054cm3, resulting in a power density of 2.68mW/cm3. Incorporation of a simple parallel plate structure that provides the proof mass for low frequency resonant operation in addition to cogeneration via electrostatic energy scavenging provides a 19.82 to 35.29 percent increase in voltage beyond the piezoelectric generated DC rails. This corresponds to approximately 2.1nW additional power from the electrostatic scavenger component and demonstrates the first instance of hybrid energy scavenging using both piezoelectric and synchronous electrostatic transduction. Furthermore, it provides a complete system architecture and development platform for additional enhancements that will enable in excess of 100uW additional power from the electrostatic scavenger

Resilient energy harvesting systems

PhD ThesisDeveloping resilient sensor systems for deployment in extreme environments is a challenge which silicon carbide, along with other wide band gap materials, stands to play a major role in. However, any system developed will be hindered in its usefulness unless the problem of providing a power supply in these extreme conditions is addressed. This work addresses this need; a wireless sensor node conceived of standard o the shelf components was first developed and used as the basis for the design considerations required for a silicon carbide sensor node. The silicon system developed uses a piezoelectric energy harvester for the power supply and exhibits favourable operating characteristics for low vibration environments. It is capable of continuous operation at 120 mg (1.177 ms2) and at 40 mg operates with a system duty cycle of 0.05. PZT, a standard piezoelectric energy harvesting material, was characterised to 300 C to test its resilience to the conditions found in hostile environments. The material degrades considerably with temperature, with a decrease in Youngs modulus from 66 GPa at room temperature to 8.16 GPa at 300 C. The room temperature value is repeatable once cooled with an observed hysteresis in the upper temperature range. The peak output voltage at resonance also varies with temperature, resulting in an 11.6% decrease in room temperature voltage once the device is heated to 300 C. The output voltage at 300 C is found to be 2.05 V, a considerable decrease from the initial 11.1 V output at room temperature. The decrease in voltage with temperature is not monotonic as maybe expected, the data showing that at 473 K there is an increase in output voltage which is caused by a decrease in mechanical damping. SiC pin diodes were fabricated with wide drift regions to promote a large depletion width, in order to maximise the capture cross section of incident light on the devices. The large drift region produces a high series resistance. However, ll factors above 0.7 show that the device is not signi cantly a ected. SiC is shown to be an e ective UV harvester with an observed increase in output power from 0.17 mWcm2 at room temperature to 0.32 mWcm2 at 600 i K. Fill factor also remains stable with temperature, indicating that the device is not a ected by variation in parameters such as shunt and series resistances or the ideality factor. There are current technological di culties which preclude the manufacture of large area silicon carbide solar cells and as such, an alternative networking solution is presented as a way to increase the output power of the devices. Given that these devices would be subject to long term high temperature exposure, a 700 hour thermal stress test is carried out at 450 C to explore the failure mechanism of the devices. There is an observed decrease in device ll factor which indicates that the device su ers increasing degradation. The data shows that this is caused by increasing series resistance, which reduces the devices ability to output power. SEM imaging and SIMS analysis show this is likely caused by signifcant metal diusion in the contact stack which could potentially be overcome by the addition ofan alternative di usion barrier. Once energy is generated by an energy harvester is must be stored so that it can be used when required. To this end both substrate and on chip storage technologies are discussed in the forms of AlN and HfO2 metal insulator metal (MIM) capacitors. To test the feasibility of both solutions, AlN and HfO2 MIM capacitors were characterised to 300 C. The HfO2 device leakage has a strong temperature dependence as observed in the IV characteristics and the capacitance density does not scale according to parallel plate theory. However, the devices can be e ectively networked and their leakage reduced with series connection. The internal voltage decay of the device is reduced with series connection, due to the di er-ing work functions of the metal-insulator contacts. The alternative AlN solution exhibits substantially weaker temperature dependance and signi cantly improved lm quality. The data shows no existence of a barrier at the insulator - metal interface, as observed in the HfO2 device IV characteristics. The extracted activation energy is stable with temperature at 1.26 +/- 0.15 eV indicating a trap assisted leakage mechanism. This method is more suitable to fabrication of large area storage as it can be fabricated o chip on a less expensive substrate and the devices fabricated exhibit a higher yield than the HfO2 devices

Design of programmable matter

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (leaves 115-119).Programmable matter is a proposed digital material having computation, sensing, actuation, and display as continuous properties active over its whole extent. Programmable matter would have many exciting applications, like paintable displays, shape-changing robots and tools, rapid prototyping, and sculpture-based haptic interfaces. Programmable matter would be composed of millimeter-scale autonomous microsystem particles, without internal moving parts, bound by electromagnetic forces or an adhesive binder. Particles can dissipate 10 mW heat, and store 6 J energy in an internal zinc-air battery. Photovoltaic cells provide 300 [mu]W outdoors and 3.0 [mu]W indoors. Painted systems can store battery reactants in the paint binder; 6 J / mm3 can be stored, and diffusion is fast enough to transport reactants to the particles. Capacitive power transfer is an efficient method to transfer power to sparse, randomly placed particles. Power from capacitive transfer is proportional to VDD 2: 100[mu]W at 3.3V and 12 mW at 35V. Inter-particle communication is possible via optical, near-field, and far-field electromagnetic systems. Optical systems allow communication with low area (sub-mm) particles, and 24 pJ/bit. Near-field electromagnetic gives precisely controlled neighborhoods, localization capability, and 37 pJ/bit. Far-field radio communication between widely spaced particles may be possible at 60 GHz; antennas that fit inside 1 mm3 exist; complete transceivers do not. A 32-bit CPU uses less than 0.26 mm2 die area, 256K x 8 SRAM uses 1.1 mm2, and 256K x 8 FLASH uses 0.32 mm2. Direct-drive electric and magnetic field systems allow actuation without moving parts inside the particles. Magnetic surface-drive motors designed for operation without bearings are not power-efficient, and parasitic interactions between permanent magnets may limit their usefulness at millimeter particle dimensions. Electrostatic surface-drive motors are power-efficient, but practical only at particle dimensions below a few millimeters. We constructed a prototype paintable display; a distributed PostScript rendering system with 1000 randomly-placed 3.4 cm nodes, each with a CPU, IR communications, and LED. The system is used to render the letter "A." We present a design, not yet constructed, for a literal paintable display, with 1.0 mm rendering particles, each with a microprocessor and memory, and 110 [mu]m display particles, with tri-color LED's and simpler circuitry. Storage of zinc-air battery reactants in the paint binder would provide an 8 hour battery life, and capacitive power distribution would allow continuous operation. We constructed a prototype sliding-cube modular robot, with 3.4 cm nodes. The system uses magnetic surface-drive actuation. We demonstrate horizontal lattice-unit translation. We describe a design, not yet constructed, for a sliding-cube modular robot with 2 mm nodes. The cubes use standard-process CMOS IC's, inserted into a cubic space frame and wire-bonded together. Arrays of passivated electrodes, 1 [mu]m from the surface of the cubes, are used for electrostatic surface-drive actuation, zero-power latching, power transfer, localization, and communication. The design allows actuation from any contacting position. Energy is stored in a standard SMT capacitor inside each node, which is recharged by power transfer through chains of contacting nodes.by Ara N. Knaian.S.M

Transpiration as a Mechanism for Mechanical and Electrical Energy Conversion.

Devices that scavenge power by utilizing energy present in their environment are of interest to researchers for powering sensors in areas where hard-wired connections are not feasible and battery maintenance is costly. Researchers have made of use vibrations, temperature, and other environmental stimuli. In this thesis, transpiration is researched as a mechanism for mechanical and electrical energy conversion. Two energy scavenging devices inspired by the transpiration mechanism in plants were developed and tested. The first is a class of mechanical actuators that operate via the evaporation of water to generate forces per unit length of 5.75 - 67.75 mN/m, angular rotations of 330o and tip deflections of 3.5 mm. The actuators were also studied as a way to achieve bottom-up self assembly by programming deflection profiles into materials using geometric parameters. These actuators can be used in applications for an evaporation-powered and controlled self-assembly of micro components. The experimental work is coupled with the development of an accurate theoretical model based on the principle of virtual work. The second type of devices developed in this thesis use an evaporation-induced flow within leaf-like microvasculature networks to drive the movement of gas bubbles through capacitor plates. This motion allows the charge pumping of an energy conversion circuit. Evaporation-driven flow was enhanced by using porous materials at the fluidic channel outlets to achieve a maximum flow velocity of 1.5 cm/s. Changes in capacitance measured at 1 MHz were between 8 - 10 pF and greater than 30 pF at lower frequencies for each bubble. Current generated by capacitance change was measured to reach up to 1 nA. Using the conversion circuit, voltage outputs up to 5 microvolts were measured for each water to air interface. A theoretical bound of the scavenged power density was calculated as a function of the size of the storage capacitor. Theoretical analysis and simulation results are presented to describe how the circuit can be modified to suit the energy harvesting application. The primary contribution of this thesis is the demonstration that the transpiration mechanism of plants can be mimicked in microscale devices to provide mechanical and electrical energy.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61555/1/rborno_1.pd

A Novel Micro Piezoelectric Energy Harvesting System

(Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007(PhD) -- İstanbul Technical University, Institute of Science and Technology, 2007Bu tezde yeni bir titreşim temelli mikro enerji harmanlayıcı sistemi önerilmiştir. Titreşimler ve ani hareketler, mekanik yapının sadece eğilmesine değil aynı zamanda gerilmesine yol açar, bu sayede sistem doğrusal olmayan bölgede çalışır. İnce piezoelektrik film tabakası mekanik stresi elektrik enerjisine çevirir. Mikrowatt mertebesinde güç seviyeleri mm3’lük aletlerle elde edilebilir, bu da güneş panellerinde elde edilen güç yoğunlukları kadar yüksektir. Algılayıcı kabiliyeti sayesinde bilgi depolayabilen, kum tanesi büyüklüğünde olan ve üretiminde kullanılan temel malzeme silikon olan bu aletler “zeki kum” olarak isimlendirilmiştir. Mekanik yapının modellenmesi ve tasarımı geliştirilmiş ve üretim sonuçları da ayrıca verilmiştir. Sistemin bilgi gönderebilmesi ve alabilmesi amacıyla iyi bilinen RFID teknolojisi tabanlı bir kablosuz haberleşme yöntemi önerilmiştir. Bu bağlamda, paket taşımacılığında sürekli ivme denetleme, sınır güvenliği için kendinden beslemeli algılayıcılar, çabuk bozulan yiyeceklerin taşımacılığında sıcaklık denetleme ve pilsiz kalp atışı algılayıcı gibi birçok uygulama önerilmiştir.In this thesis, a novel, vibration based micro energy harvester system is proposed. Vibrations or sudden movements cause the mechanical structure does not only bend but also stretch, thus working in non-linear regime. The piezoelectric thin film layer converts the mechanical stress into the electrical energy. Microwatts of power can be achieved with a mm3 device which yields a high power density levels on the order of the solar panels. This device is named “smart sand”, because it has also sensor capabilities that can store information, its size is almost a sand grain and the main material used for the fabrication is silicon. The modeling and design of the mechanical structure has been developed and fabrication results have also been given in the thesis. In order for the system to send and receive the information, a wireless communication scheme is proposed which is based on the well-known RFID technology. In this concept, several applications are proposed such as continuous acceleration monitoring in package delivery, self-powered sensors for homeland security, temperature monitoring of the perishable food item delivery and a batteryless heart rate sensor.DoktoraPh

ITER Technical Basis

The Agency is part of its support for the joint venture known as the International Thermonuclear Experimental Reactor (ITER)