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ABSTRACT: This paper presents a novel miniature airflow energy harvester for wireless sensing applications. The energy harvester consists of a wing that is attached to a cantilever spring. The wing oscillates in response to a steady airflow. An electromagnetic transducer is used to extract electrical energy from the airflow induced oscillations. Both vertical and horizontal orientations have been studied. Experiments have shown that such generator can operate at airflow speeds as low as 1.5m/s which compares well to turbines. When the airflow speed is over 2m/s, the average output power exceeds 90uW, which is sufficient for powering wireless sensor nodes in Heat, Ventilation and Air Condition (HVAC) systems in buildings.
IEEE Sensors Journal 01/2013; 13(2):691-700. · 1.52 Impact Factor
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ABSTRACT: This paper describes the development and implementation of a self-powered control system that autonomously adapts the resonant frequency of an electromagnetic vibration-based energy harvester to ambient vibration frequency. The tuning mechanism adjusts the harvester's spring stiffness by varying the axial tensile force between two permanent magnets. The system adjusts the resonant frequency of the harvester from 64 to 78 Hz, increasing the operational bandwidth of the harvester from 0.26 to 14 Hz, using a single structure. The same tuning principle is also applied to protect the harvester from over range acceleration which could cause physical damage to its structure. The closed loop control uses the phase difference between the harvester output signal and ambient vibration, measured by an accelerometer attached to the vibration source, to adjust the tuning mechanism.
Smart Materials and Structures 09/2010; 19(11):115005. · 2.09 Impact Factor
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ABSTRACT: A novel fabrication process for nanostructures for thermoelectric microgenerators, based on a combination of a traditional silicon micro- fabrication techniques, electroplating and submicron ion-track nano- lithography, is discussed. Ion-track etched polyimide nanotemplates (30-80 nm pore diameters) are used to grow Bi<sub>2</sub>Te<sub>3</sub> nanowires by electroplating. The Bi<sub>2</sub>Te<sub>3</sub> film's microstructural and thermoelectric properties are reported.
Electronics Letters 02/2008; · 0.96 Impact Factor
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ABSTRACT: A fundamental limitation of screen printing is the achievable alignment accuracy and resolution. This paper presents details
of a thick-resist process that improves both of these factors. The technique involves exposing/developing a thick resist to
form the desired pattern and then filling the features with thick film material using a doctor blading process. Registration
accuracy comparable with standard photolithographic processes has been achieved resulting in minimum feature sizes of <50μm
and a film thickness of 100μm. Piezoelectric elements have been successfully poled on a platinised silicon wafer with a measured
d
33 value of 60pCN−1.
Journal of Electroceramics 11/2007; 19(4):327-331. · 1.19 Impact Factor
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ABSTRACT: This paper reports, for the first time, the implementation of a microsystem powered entirely from ambient vibrations. Sufficient electrical energy is harvested to power a radio-frequency (RF) linked accelerometer based microsystem. The microsystem is energy aware and will adjust the measurement/transmit duty cycle according to the available energy; this is typically every 50 seconds during normal operation. The system is fully powered from 45 muW<sub>rms</sub> scavenged by a miniature electromagnetic (EM) vibration energy harvester of volume ; level of 0.6ms<sup>-2</sup>.
Sensors, 2007 IEEE; 11/2007
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ABSTRACT: Electromagnetic vibration powered generators convert kinetic energy present in the application environment into electric energy.
Such generators may be used as an alternative power supply to batteries in wireless sensor systems enabling indefinite and
maintenance free operation. This paper presents an experimental comparison between macro and micro scale electromagnetic generators
based upon an identical magnetic circuit and explores the influence of size on the performance and behaviour of these devices.
The large scale traditionally fabricated generator exhibits the highest power density of 2615nW/mm3 compared to the microgenerator power density of 47nW/mm3. The macro scale device achieves the optimum damping conditions where electromagnetic damping equals parasitic damping. The
level of electromagnetic damping in the micro scale generator is an order of magnitude less than the parasitic damping due
to reduced electromagnetic coupling. This comparison highlights the challenges involved in scaling electromagnetic devices
down in size.
Microsystem Technologies 01/2007; 13(11):1647-1653. · 0.93 Impact Factor
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CoRR. 01/2007; abs/0711.3316.
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CoRR. 01/2007; abs/0711.3314.
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Journal of Micromechanics and Microengineering 01/2007; · 2.11 Impact Factor
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ABSTRACT: This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts
external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static
magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally
in the plane of the chip. The volume of this device is approximately 100mm3. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic
FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam
generator design. The predicted voltage levels of 0.7–4.15V can be generated for a two-pole arrangement by tuning the damping
factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate
a maximum power output of 104nW for 0.4g (g=9.81ms−1) input acceleration at 1.615kHz. Other frequencies can be achieved by employing different geometries or materials.
Microsystem Technologies 08/2006; 12(10):1071-1077. · 0.93 Impact Factor
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ABSTRACT: In this paper we, report on the design, simulation and initial results of a microgenerator, which converts external vibrations into electrical energy. Power is generated by means of electromagnetic transduction with static magnets positioned either side of a moving coil located on a silicon structure designed to resonate laterally in the plane of the chip. The development and fabrication of a micromachined microgenerator that uses standard silicon based fabrication techniques and a low cost, batch process is presented. Finite element simulations have been carried out using ANSYS to determine an optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft's Maxwell 2D software have shown voltage levels of 4 to 9 V can be generated from the single beam generator designs. Initial results at atmospheric pressure yield 0.5 μW at 9.81 ms<sup>-2</sup> and 9.5 kHz and emphasise the importance of reducing unwanted loss mechanisms such as air damping.
Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005
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ABSTRACT: Over recent years there has been a growing interest in the field of micro-systems and their applications across a wide range of areas, including sensor-based systems able to operate with full galvanic isolation. This paper details the development of a self-powered system, specifically for sensor applications that can be energised on a test rig by an electromagnetic vibration-powered generator. This enables wireless operation without the use of a battery with a finite service life. The results of two systems designed for remote sensing in condition monitoring applications are discussed. The first system uses a liquid crystal display to provide the system output; the second uses an infra-red link to transmit the data output.
Sensors and Actuators A Physical 01/2004; · 1.80 Impact Factor
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ABSTRACT: A metallic triple-beam resonator with thick-film piezoelectric elements to drive and detect vibrations is presented. The resonator substrate was fabricated by a double-sided photochemical-etching technique and the thick-film piezoelectric elements were deposited by a standard screen-printing process. The resonator, 15.5 mm long and 7 mm wide, has a favoured mode at 6.2 kHz with a Q-factor of 3100.
Electronics Letters 07/2003; · 0.96 Impact Factor
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ABSTRACT: The optimum mode of double-ended tuning-fork-style resonators is a
lateral vibration in the plane of the wafer. Lateral vibrations are
typically excited using the comb drive approach, but this requires
modification to the resonator structure. This paper reports a simple
method for exciting and detecting lateral vibrations without modifying
the resonator, thereby enabling the optimum dynamically balanced
structure to be used. This approach uses plane electrodes positioned
parallel to the resonator's tines to excite the vibrations while the
change in resistance along the length of the resonator enables the
vibrations to be detected. Test devices have been fabricated in
single-crystal silicon using the buried oxide in silicon-on-insulator
wafers as a sacrificial layer. The resonators are 340-μm long,
3-μm thick with tines 2-μm wide. The gap between the tines and the
electrode is 2 μm. Visual inspection in a scanning electron
microscope and electrical tests have confirmed the validity of this
approach
Journal of Microelectromechanical Systems 04/2000; · 2.10 Impact Factor
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12/1999; , ISBN: 9780471346081
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ABSTRACT: A vital requirement for a resonator-based sensor is a high degree of balance in the resonator's chosen mode of vibration. A systematic study of the balance and stress sensitivity of a number of important resonator geometries has been performed. New methods have been developed both to evaluate and optimize the balance of a resonator structure. This paper presents the results of the study, details the methods used and provides some simple design rules for resonators. All the geometries evaluated are realizable as microsensors using silicon micromachining techniques.
Journal of Micromechanics and Microengineering 12/1998; 5(2):103. · 2.11 Impact Factor
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ABSTRACT: This paper is concerned with generators that harvest electrical energy from the kinetic energy present in the sensor nodes environment. These generators have the potential to replace or augment battery power which has a limited lifetime and requires periodic replacement which limits the placement and application of the sensor node.
Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS - DTIP’06, 26-28 April 2006, Stresa, Lago Maggiore, Italy, 6 p.
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ABSTRACT: This paper investigates how the power generated by electromagnetic based vibrational power generators scales with the dimension of the generator. The effects of scaling on the magnetic fields, the coil parameters and the electromagnetic damping are presented. An analysis is presented for both wire-wound coil technology and micro-fabricated coils.
Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS - DTIP’06, 26-28 April 2006, Stresa, Lago Maggiore, Italy, 7 p.
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