Michail E. Kiziroglou

Rolling Rod Electrostatic Microgenerator

The difficulty of maximizing the proof mass, and lack of broadband operation, are key issues for miniaturized energy-harvesting devices. Here, a novel electrostatic energy harvester is presented, employing an external free-rolling proof mass to address these issues. A description of the operating principle is given, and the kinetic dynamics of the cylinder are analyzed. The electrostatics of the system are simulated, identifying the device performance for different dielectric dimensions and surface specifications. The fabrication of a prototype device is presented, and physical characterization results demonstrate a successful fabrication technique for dielectric sizes down to 100 nm. Capacitance measurements reveal a capacitance ratio of 4 and are in agreement with simulation results. A voltage gain of 2.4 is demonstrated. The device is suitable for energy harvesting from low-frequency high-amplitude ambient motion sources such as the human body.

Design and Fabrication of Heat Storage Thermoelectric Harvesting Devices

Thermoelectric energy harvesting requires a substantial temperature difference ΔT to be available within the device structure. This has restricted its use to particular applications such as heat engine structural monitoring, where a hot metal surface is available. An alternative approach is possible in cases where ambient temperature undergoes regular variation. This involves using a heat storage unit, which is filled with a phase-change material (PCM), to create an internal spatial temperature difference from temperature variation in time. In this paper, key design parameters and a characterization methodology for such devices are defined. The maximum electrical energy density expected for a given temperature range is calculated. The fabrication, characterization, and analysis of a heat storage harvesting prototype device are presented for temperature variations of a few tens of degrees around 0 °C, corresponding to aircraft flight conditions. Output energy of 105 J into a 10- Ω matched resistive load, from a temperature sweep from +20 °C to -21 °C, then to +25 °C is demonstrated, using 23 g of water as the PCM. The proposed device offers a unique powering solution for wireless sensor applications involving locations with temperature variation, such as structural monitoring in aircraft, industrial, and vehicle facilities.

A MEMS Self-Powered Sensor and RF Transmission Platform for WSN Nodes

We report a new microelectromechanical systems (MEMS) self-powered sensor and RF transmission platform for wireless sensor network (WSN) nodes which can operate at energy levels orders of magnitude lower than current equivalent systems. Using the microgenerator as a power amplifier to drive a passive kick-and-resonate transmitter architecture as an alternative to a standard power hungry transmitter, this platform eliminates the need for both secondary energy storage and power conditioning circuits. This enables a significant reduction in the size, weight, complexity and cost, and allows operation at much lower excitation frequencies. The prototype platform consists of a MEMS rolling-rod microgenerator, the output voltage of which is used to kick a resonant loop antenna. The generator can be directly primed by a suitable voltage-output sensor. This is the first platform to achieve wireless sensor transmission powered only by a MEMS energy harvester.

MEMS Energy Harvesting Powered Wireless Biometric Sensor

One of the main challenges in developing wireless biometric sensors is the requirement for integration of various systems into a very compact device. Such systems include sensing units, conditioning electronics, transmitters and power supplies. In this work, a novel system integration architecture is presented. A unique feature of this new architecture is that the sub-systems are selected and designed for direct output-to-input connection. An array of active pH sensors is used to transform a pH level to an electrical potential in the range of 0 - 2 Volts. This signal is amplified by an electrostatic energy harvester suitable for human motion operation. The amplified signal drives a custom LC transmitter specially designed to suit the harvester output. A system of notable simplicity is achieved and may serve as a demonstrator for other wireless sensors.

Performance of phase change materials for heat storage thermoelectric harvesting

Heat storage energy harvesting devices have promise as independent power sources for wireless aircraft sensors. These generate energy from the temperature variation in time during flight. Previously reported devices use the phase change of water for heat storage, hence restricting applicability to instances with ground temperature above 0 °C. Here, we examine the use of alternative phase change materials (PCMs). A recently introduced numerical model is extended to include phase change inhomogeneity, and a PCM characterization method is proposed. A prototype device is presented, and two cases with phase changes at approximately −9.5 °C and +9.5 °C are studied.

MEMS energy harvester for wireless biosensors

This paper reports a motion energy harvester integrated with a battery-less wireless transmitter, and the successful transmission of low power pulses representing sensor data. An electrostatic harvester, primed by voltage representing sensor data, delivers output pulses to a resonant transmitter with an integrated antenna. This is the first ever reported demonstration, to our knowledge, of wireless sensor transmission solely powered by MEMS energy harvesting devices.

Aircraft Strain WSN Powered by Heat Storage Harvesting

The combination of ultra-low-power wireless communications and energy harvesting enables the realization of autonomous wireless sensor networks. Such networks can be usefully applied in commercial aircraft where wireless sensing solutions contribute to weight reduction and increased ease of installation and maintenance. This paper presents, for the first time, a complete energy-autonomous wireless strain monitoring system for aircraft. The system is based on a multimode wireless time-division multiple access (TDMA) medium access control (MAC) protocol that supports automatic configuration and a time-stamping accuracy better than 1 ms. The energy supply depends solely on an innovative thermoelectric energy harvester, which takes advantage of the changes in environmental temperature during takeoff and landing. The system was successfully integrated and passed the functional and flight-clearance tests that qualify it for use in a flight-test installation.

A Motion-Powered Piezoelectric Pulse Generator for Wireless Sensing via FM Transmission

A motion-powered pulse generator using piezoelectric transduction is reported in this paper for wireless sensing devices. A metallic rolling ball is implemented in the prototype as an inertial proof mass excited by external motions at random low frequency. Taking advantage of the metallic proof mass, magnetic coupling can be achieved to actuate the piezoelectric cantilever by attaching tip magnets to the free end. In addition, self-synchronous switching is achieved by applying electrodes to the track of the rolling ball. A new passive prebiasing mechanism is introduced to improve the performance of the pulse generator. Both simulation and experimental results were conducted to demonstrate the improvement. Experimental results show that 76% more energy can be extracted by the prebias mechanism compared to the unbiased case. A transmission circuit based on a Colpitts oscillator was built to test the performance of the capacitor-powered oscillator, which is designed as the load of the pulse generator. By adding a voltage control component, the transmission circuit is capable of encoding a sensor signal by frequency modulation, which demonstrates the feasibility of implementing a motion-powered wireless sensing prototype based on the piezoelectric pulse generator.

Acoustic energy transmission in cast iron pipelines

In this paper we propose acoustic power transfer as a method for the remote powering of pipeline sensor nodes. A theoretical framework of acoustic power propagation in the ceramic transducers and the metal structures is drawn, based on the Mason equivalent circuit. The effect of mounting on the electrical response of piezoelectric transducers is studied experimentally. Using two identical transducer structures, power transmission of 0.33 mW through a 1 m long, 118 mm diameter cast iron pipe, with 8 mm wall thickness is demonstrated, at 1 V received voltage amplitude. A nearlinear relationship between input and output voltage is observed. These results show that it is possible to deliver significant power to sensor nodes through acoustic waves in solid structures. The proposed method may enable the implementation of acousticpowered wireless sensor nodes for structural and operation monitoring of pipeline infrastructure.

Opportunities for Sensing Systems in Mining

Pervasive sensing—the capability to deploy large numbers of sensors, to link them to communication networks, and to analyze their collective data—is transforming many industries. In mining, networked sensors are already used for remote operation, automation, including driverless vehicles, health, and safety, and exploration. In this paper, the state-of-the-art sensing and monitoring technologies are assessed as solutions against the main challenges and opportunities in the mining industry. Localization, mapping, remote operation, maintenance, and health and safety are identified as the main beneficiaries from rapidly developing technologies, such as 3-D visualization, augmented reality, energy autonomous sensor nodes, distributed sensing, smart network protocols, and big data analytics. It is shown that the identification and management of ore grade, in particular, which transcends each stage of the mining process, may critically benefit from certain arising sensing technologies, where major efficiency improvements are possible in exploration, extraction, haulage, and processing activities.