Publications
217 results found
Lepipas G, Holmes AS, 2024, Miniature water flow energy harvester based on Savonius-type microturbine: an experimental study, Smart Materials and Structures, Vol: 33, ISSN: 0964-1726
In this experimental study, a miniature turbine-based water flow energy harvester designed for the purpose of providing power to wireless sensors within water pipes is reported. The device comprises a Savonius-type turbine and a radial flux permanent magnet electromagnetic generator. The two are magnetically coupled so that, while the turbine is submerged in the water flow, the generator operates in air. The device is cylindrical with a diameter of 0.8 cm and a length of 7.2 cm and, when inserted through a hole in a pipe wall so that only the turbine protrudes into the flow, it presents a cross-sectional area to the flow of only 1.25 cm2. Manufacturing was achieved through a blend of conventional machining methods, laser cutting, rapid prototyping, and the utilization of flexible printed circuit board technology for the generator stator. To ensure low friction and minimize cut in speed, ceramic ball bearings were employed. The prototype can function effectively at water velocities as low as 0.5 m s−1, generating electrical power within the range of 125 µW–5.1 mW when subjected to flow speeds between 0.5 and 2 m s−1. A maximum overall efficiency of 2.2% is achieved, when the water speed is 0.8 m s−1. Performance curves derived from experimental testing of the turbine for a range of rotor designs, obtained on a water flow rig, are presented and discussed.
Yang SKE, Kiziroglou ME, Yeatman EM, et al., 2023, Acoustic flow sensor using a passive bell transducer, IEEE Sensors Journal, Vol: 23, Pages: 20553-20560, ISSN: 1530-437X
Sensing based on a passive transducer that is wirelessly linked to a nearby data collection node can offer an attractive solution for use in remote, inaccessible, or harsh environments. Here we report a pipe flow sensor based on this principle. A transducer mounted inside the pipe generates an acoustic signal that is picked up by an external microphone. The passive transducer comprises a cavity with a trapped ball that can oscillate in response to flow. Its collisions generate an acoustic signal correlated to the flow speed. The transducer is implemented on a 6 mm diameter probe and characterized as a water flow meter. The time - average microphone voltage output is calculated by an analogue circuit, without any further signal processing. With the microphone mounted on the probe, and for flow rates in the range 0.35 m/s to 6.5 m/s, correlation between the sensor voltage output and flow rate data from a commercial flow meter is demonstrated with a worst-case accuracy of 2%. This was achieved by simple averaging of the acoustic pulse train over a 5-second time interval. Consistent correlation with the microphone mounted on the pipe wall at distances up to 150 mm from the probe location is also reported. These results demonstrate the viability of remote acoustic flow sensing using passive structures and offer a simple and minimally invasive flow monitoring method.
Chavda M, Zeeshan M, O'Sullivan C, et al., 2023, Magnetic-Induction-Based Positioning System Using Dual Multiplexing Technique, IEEE SENSORS LETTERS, Vol: 7, ISSN: 2475-1472
Carandell M, Toma DM, Holmes AS, et al., 2023, Experimental Validation of a Fast-Tracking FOCV-MPPT Circuit for a Wave Energy Converter Embedded into an Oceanic Drifter, JOURNAL OF MARINE SCIENCE AND ENGINEERING, Vol: 11
Carandell M, Holmes A, Toma D, et al., 2023, Effect of the sampling parameters in FOCV-MPPT circuits for fast-varying EH sources, IEEE Transactions on Power Electronics, Vol: 38, Pages: 2695-2708, ISSN: 0885-8993
The fractional open-circuit voltage (FOCV) method is extensively used in low-power energy harvesting (EH) sources to extract maximum power. For fast-varying EH sources, a fast sampling rate is required. This work theoretically analyzes the influence of the sampling time and period on the harvested power of sinusoidal EH sources. In addition, the circuit limitations to achieve a fast sampling rate are presented and circuits to deal with them proposed and implemented. Furthermore, one of the circuits is based on a novel pseudoFOCV method and achieves the fastest sampling rate. Experimental tests are performed with a 2 Hz, 1 to 3 V sinusoidal source having an output resistance of 127 Ω, and the results are shown to agree with theoretical predictions. It is shown that the harvested power increases with the sampling rate when the sampling time is negligible (sampling 15 times faster than the source frequency extracts around 99% of the maximum), and for fixed sampling times, there is an optimum sampling rate where the harvested power is maximum. The first result is generic and valid for methods other than the FOCV. Tests were also performed with a small-scale wave energy converter placed in a linear shaker emulating a sea environment. Harvested power increases by 25% with respect using a commercial FOCV unit with a low sampling rate.
Haimov E, Chapman A, Bresme F, et al., 2023, Addendum: Theoretical demonstration of a capacitive rotor for generation of alternating current from mechanical motion., Nature Communications, Vol: 14, Pages: 483-483, ISSN: 2041-1723
Chavda M, Chandola A, Malik S, et al., 2023, Development of Time-Multiplexed Magnetic-Induction Based Ranging Systems
Ranging and locating systems are necessary currently. Localization of robots operating underground, miners and machinery in mining environments, and interior environments are few applications that demand a reliable and accurate positioning system. Magnetic-induction (MI) based ranging and positioning system is widely used in such applications because the magnetic permeability of different mediums are almost same. However, the MI based system are complex since multiple transmitters are needed for accurate ranging and positioning. In this paper, we present a time division multiplexing MI based ranging system. A single signal source is needed to excite the magnetic coil sequentially. A prototype is developed and tested for a range of 1 meter with an error less than ± 2 cm.
Holmes AS, Yang SKE, Kiziroglou ME, et al., 2022, Miniaturized wet-wet differential pressure sensor, IEEE Sensors Conference, Publisher: IEEE, ISSN: 1930-0395
We report a miniaturized wet-wet differential pressure sensor with applications in pressure and flow sensing in water networks and other harsh environments. The device is similar in concept to a conventional wet-wet differential pressure sensor in that the sensing element is protected from the external environment by oil-filled cavities closed off by corrugated diaphragms. However, with a package envelope of 11.0 x 4.8 x 3.4 mm 3 , corresponding to a volume of only 0.18 cm 3 , the device is considerably smaller than commercially available wet-wet differential pressure sensors. A high degree of miniaturization has been achieved by using micromachining to fabricate the corrugated diaphragms. Preliminary experimental results are presented showing operation of the device as a delta-pressure flow speed sensor in a water flow test rig.
Malik S, O'Sullivan C, Reddyhoff T, et al., 2022, An acoustic 3D positioning system for robots operating underground, IEEE Sensors Letters, Vol: 6, Pages: 1-4, ISSN: 2475-1472
Underground robots are potentially helpful in many application domains, including geotechnical engineering, agriculture, and archaeology. One of the critical challenges in developing underground robotics is the accurate estimation of the positions of the robots. Acoustic-based positioning systems have been explored for developing an underground 3D positioning system. However, the positioning range is limited due to attenuation in the medium. This letter proposes an underground positioning system that utilizes a novel and easy-to-implement electronic approach for measuringthe acoustic propagation times between multiple transmitters and a receiver. We demonstrate a prototype using four transmitters at the surface and a single buried acoustic sensor as a proof-of-concept. The times of arrival for signals emitted by the different sources are measured by correlating the transmitted and received signals. The distances between the multiple transmitters and a receiver are estimated, and a tri-linearization algorithm is used to estimate the position of the buried sensor in 3D with respect to reference coordinates. The system is tested in a soil tank. The experimental results show that the proposed system is able to estimate the 3D position of buried sensors with an error of less than ±2.5 cm within a measurement field of size 50 cm × 50 cm × 35 cm in X, Y, and Z (width × length × depth). The proposed electronic synchronization approach allows increasing the positioning range of the system by increasing the number of transmittersat the surface. This paves the way for the development of a positioning system for robots operating underground.
Holmes AS, Kiziroglou ME, Yang SKE, et al., 2022, Minimally invasive online water monitor, IEEE Internet of Things Journal, Vol: 9, Pages: 14325-14335, ISSN: 2327-4662
Sensor installation on water infrastructure is challenging due to requirements for service interruption, specialised personnel, regulations and reliability as well as the resultant high costs. Here, a minimally invasive installation method is introduced based on hot-tapping and immersion of a sensor probe. A modular architecture is developed that enables the use of interchangeable multi-sensor probes, non-specialist installation and servicing, low-power operation and configurable sensing and connectivity. A prototype implementation with a temperature, pressure, conductivity and flow multi-sensor probe is presented and tested on an evaluation rig. This paper demonstrates simple installation, reliable and accurate sensing capability as well as remote data acquisition. The demonstrated minimally invasive multi-sensor probes provide an opportunity for the deployment of water quality sensors that typically require immersion such as pH and spectroscopic composition analysis. This design allows dynamic deployment on existing water infrastructure with expandable sensing capability and minimal interruption, which can be key to addressing important sensing parameters such as optimal sensor network density and topology.
Ramachandran S, Zhong Y, Robertson S, et al., 2022, Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding, MATERIALIA, Vol: 23, ISSN: 2589-1529
Yu M, Reddyhoff T, Dini D, et al., 2022, Acoustic emission enabled particle size estimation via low stress-varied axial interface shearing, IEEE Transactions on Instrumentation and Measurement, Vol: 71, ISSN: 0018-9456
Acoustic emission (AE) refers to a rapid release of localized stress energy that propagates as a transient elastic wave and is typically used in geotechnical applications to study stick-slip during shearing, and breakage and fracture of particles. This article develops a novel method of estimating the particle size, an important characteristic of granular materials, using axial interface shearing-induced AE signals. Specifically, a test setup that enables axial interface shearing between a one-dimensional compression granular deposit and a smooth shaft surface is developed. The interface sliding speed (up to 3mm/s), the compression stress (0-135kPa), and the particle size (150μm-5mm) are varied to test the acoustic response. The start and end moments of a shearing motion, between which a burst of AE data is produced, are identified through the variation of the AE count rates, before key parameters can be extracted from the bursts of interests. Linear regression models are then built to correlate the AE parameters with particle size, where a comprehensive evaluation and comparison in terms of estimation errors is performed. For granular samples with a single size, it is found that both the AE energy related parameters and AE counts, obtained using an appropriate threshold voltage, are effective in differentiating the particle size, exhibiting low fitting errors. The value of this technique lies in its potential application to field testing, for example as an add-on to cone penetration test systems and to enable in-situ characterization of geological deposits.
Yang S, Kiziroglou M, Yeatman E, et al., 2021, Passive acoustic transducer as a fluid flow sensor, IEEE Sensors Conference, Publisher: IEEE, Pages: 1-4
Autonomy and minimal disruption are key desirable features for sensors to be deployed in medical, industrial, vehicle and infrastructure monitoring systems. Using a passive structure to transduce the quantity of interest into an acoustic or electromagnetic wave could offer an attractive solution for remote sensing, lifting the requirements of installing active materials, electronics, and power sources in remote, inaccessible, sensitive, or harsh environment locations. Here, we report a simple cavity and ball structure that transduces fluid flow through a pipe into an acoustic signal. A microphone on the outside wall of the pipe records the intensity and arrival rate of the sound pulses generated by collisions between the ball and the cavity walls. Using this approach external measurement of flow is demonstrated with adequate repeatability before any acoustic signal processing. This result is expected to open the way to the implementation of passive, remotely readable sensors for fluid flow and other fluid properties of interest.
Yu M, Reddyhoff T, Dini D, et al., 2021, Using ultrasonic reflection resonance to probe stress wave velocity in assemblies of spherical particles, IEEE Sensors Journal, Vol: 21, Pages: 22489-22498, ISSN: 1530-437X
A high-sensitivity method to measure acousticwave speed in soils by analyzing the reflected ultrasonic signalfrom a resonating layered interface is proposed here.Specifically, an ultrasonic transducer which can be used to bothtransmit and receive signals is installed on a low-high acousticimpedance layered structure of hard PVC and steel, which in turnis placed in contact with the soil deposit of interest. The acousticimpedance of the soil (the product of density and wave velocity)is deduced from analysis of the waves reflected back to thetransducer. A system configuration design is enabled bydeveloping an analytical model that correlates the objectivewave speed with the measurable reflection coefficient spectrum.The physical viability of this testing approach is demonstratedby means of a one-dimensional compression device that probesthe stress-dependence of compression wave velocity of differentsizes of glass ballotini particles. Provided the ratio of thewavelength of the generated wave to the soil particle size issufficiently large the data generated are in agreement with dataobtained using conventional time-of-flight measurements. Inprinciple, this high-sensitivity approach avoids the need for thewave to travel a long distance between multiple transmitterreceiver sensors as is typically the case in geophysical testingof soil. Therefore it is particularly suited to in-situ observation ofsoil properties in a highly compact setup, where only a single transducer is required. Furthermore, high spatialresolution of local measurements can be achieved, and the data are unaffected by wave attenuation as transmitted insoil.
Becker T, Borjesson V, Cetinkaya O, et al., 2021, Energy harvesting for a green internet of things, PSMA
The ubiquitous nature of energy autonomous microsystems, which are easy to install and simple toconnect to a network, make them attractive in the rapidly growing Internet of Things (IoT) ecosystem.The growing energy consumption of the IoT infrastructure is becoming more and more visible. Energyharvesting describes the conversion of ambient into electrical energy, enabling green power suppliesof IoT key components, such as autonomous sensor nodes.Energy harvesting methods and devices have reached a credible state-of-art, but only a few devices arecommercially available and off-the-shelf harvester solutions often require extensive adaption to theenvisaged application. A synopsis of typical energy sources, state-of-the-art materials, and transducertechnologies for efficient energy conversion, as well as energy storage devices and power managementsolutions, depicts a wide range of successful research results. Developing power supplies for actualusage reveals their strong dependence on application-specific installation requirements, powerdemands, and environmental conditions.The industrial challenges for a massive spread of autonomous sensor systems are manifold anddiverse. Reliability issues, obsolescence management, and supply chains need to be analyzed forcommercial use in critical applications. The current gap between use-case scenarios and innovativeproduct development is analyzed from the perspective of the user. The white paper then identifies thekey advantages of energy autonomy in environmental, reliability, sustainability, and financial terms.Energy harvesting could lead to a lower CO2 footprint of future IoT devices by adoptingenvironmentally friendly materials and reducing cabling and battery usage. Further research anddevelopment are needed to achieve technology readiness levels acceptable for the industry. This whitepaper derives a future research and innovation strategy for industry-ready green microscale IoTdevices, providing useful information to the sta
Shi M, Holmes AS, Yeatman EM, 2021, NONLINEAR WIND ENERGY HARVESTING BASED ON MECHANICAL SYNCHRONOUS SWITCH HARVESTING ON INDUCTOR, 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers), Publisher: IEEE, Pages: 964-967, ISSN: 2167-0013
Haimov E, Chapman A, Bresme F, et al., 2021, Theoretical demonstration of a capacitive rotor for generation of alternating current from mechanical motion, Nature Communications, Vol: 12, Pages: 3678-3678, ISSN: 2041-1723
Innovative concepts and materials are enabling energy harvesters for slower motion, particularly for personal wearables or portable small-scale applications, hence contributing to a future sustainable economy. Here we propose a principle for a capacitive rotor device and analyze its operation. This device is based on a rotor containing many capacitors in parallel. The rotation of the rotor causes periodic capacitance changes and, when connected to a reservoir-of-charge capacitor, induces alternating current. The properties of this device depend on the lubricating liquid situated between the capacitor’s electrodes, be it a highly polar liquid, organic electrolyte, or ionic liquid – we consider all these scenarios. An advantage of the capacitive rotor is its scalability. Such a lightweight device, weighing tens of grams, can be implemented in a shoe sole, generating a significant power output of the order of Watts. Scaled up, such systems can be used in portable wind or water turbines.
Shi M, Holmes AS, Yeatman EM, 2021, Stretchable Piezoelectric Tensile Sensor Patterned via Ultraviolet Laser Cutting, 20th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS), Publisher: IEEE, Pages: 8-11
Shi M, Holmes A, Yeatman E, 2020, Piezoelectric wind velocity sensor based on the variation of galloping frequency with drag force, Applied Physics Letters, Vol: 116, ISSN: 0003-6951
In this paper, we demonstrate a miniature energy harvesting wind velocity sensor of simple, low-cost construction, based on a single-degree-of-freedom galloping structure. The sensor consists of a prismatic bluff body with a triangular cross section attached to the free end of acantilever incorporating a commercial polyvinylidene fluoride piezoelectric film. In the wind, the bluff body causes vibration of the cantileverbased on galloping, and the piezoelectric film converts the vibration energy into an electrical signal. We have observed a negative correlationbetween the wind velocity and the vibration frequency, and we demonstrate that this relationship can be used to detect wind velocity directlywith useful accuracy. A simple theoretical model indicates that the frequency shift can be accounted for by the effect of the axial loading dueto form drag. The model shows close agreement with the experimental results. In wind tunnel tests, a prototype wind velocity sensor basedon this principle could measure wind velocities from 4.45 to 10 m/s, with the measured velocity typically being within 4% of the referencevalue obtained using a Pitot tube.
Dou G, Holmes AS, 2020, System integration for plastic electronics using room temperature ultrasonic welding, Advanced Engineering Materials, Vol: 22, Pages: 1-6, ISSN: 1438-1656
Plastic electronics is attracting increasing attention for both high‐end applications such as flexible OLED displays in mobile phones and low‐cost items such as plastic RFID tags for product labelling and tracking. However, there are numerous technological challenges, not the least of which is to develop robust and reliable packaging methods. Unfortunately, most of the established packaging technologies used in conventional silicon electronics are not transferable to plastic electronics due to the high process temperatures involved. We have explored the use of room temperature ultrasonic welding for the realization of multilayer plastic electronic circuits, identifying two distinct modes of ultrasonic welding that can form combined electrical and mechanical connections between adjacent low‐temperature polymer films with either aluminum or printed silver metallisation. We have fabricated fully functional multilayer wireless charging coils and RFID tags to demonstrate the potential of this new system integration approach.
Shi M, Yeatman EM, Holmes AS, 2019, Energy Harvesting Piezoelectric Wind Speed Sensor, 18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Blad TWA, Machekposhti DF, Herder JL, et al., 2018, Vibration Energy Harvesting from Multi-Directional Motion Sources, International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), Publisher: IEEE
Shi M, Yeatman E, Holmes AS, 2018, MINIATURE WIND ENERGY HARVESTER BASED ON FLOW-INDUCED VIBRATION
This work demonstrates an experimental study of wideband wind energy harvesting by self-sustained flow induced vibration. We fabricated a novel folded structure using PET film as a bluffbody, which was directly mountedon a piezoelectric film to generate vibration in wind flow. The lock-in of the flow-induced vibration of the flutter was observed in our work. The vibration frequency of this device was locked at 10.8 Hz, which was its natural frequency, across a wide wind speed range from 5.8 m/s to 12.2 m/s. The continuous resonance gives this device stable output in this wide range of wind speed. Just using a small piezoelectric PVDF film of 3 cm2, the peak power output of our device can achieve 3.16 μW and keep at a high level once the self-sustained flow induced vibration occurs.
Dou G, Holmes AS, Cobb B, et al., 2018, Thermosonic-Adhesive (TS-A) Integration of Flexible Integrated Circuits on Flexible Plastic Substrates, 7th Electronic System-Integration Technology Conference (ESTC), Publisher: IEEE
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Wang P, Zhang J, Spikes HA, et al., 2016, Development of hydrodynamic micro-bearings, 16th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2016), Publisher: IOP Publishing, ISSN: 1742-6588
This paper describes the modelling and testing of mm-scale hydrodynamic bearings which are being developed to improve the efficiency of a cm-scale turbine energy harvester, whose efficiency was previously limited by poorly lubricated commercial jewel-bearings. The bearings were fabricated using DRIE and their performance was assessed using a custom built MEMS tribometer. Results demonstrate that acceptably low friction is achieved when low viscosity liquid lubricants are used in combination with an appropriate choice of friction modifier additive. Further reduction in friction is demonstrated when the step height of bearing is adjusted in accordance with hydrodynamic theory. In parallel with the experiments, hydrodynamic lubricant modelling has been carried out to predict and further optimize film thickness and friction performance. Modelling results are presented and validated against experimental friction data.
Pu SH, Darbyshire DA, Wright RV, et al., 2016, RF MEMS Zipping Varactor With High Quality Factor and Very Large Tuning Range, IEEE ELECTRON DEVICE LETTERS, Vol: 37, Pages: 1340-1343, ISSN: 0741-3106
Pillatsch P, Yeatman EM, Holmes AS, et al., 2016, Wireless power transfer system for a human motion energy harvester, Sensors and Actuators A: Physical, Vol: 244, Pages: 77-85, ISSN: 1873-3069
Human motion energy harvesting as an alternative to battery powering in body worn and implanted devices is challenging during prolonged periods of inactivity. Even a buffer energy storage system will run out of power eventually if there is no external acceleration to the harvester. This paper presents a method to actuate the rotor inside a previously presented rotational piezoelectric energy harvester wirelessly via a magnetic reluctance coupling to an external driving rotor with one or more permanent magnet stacks attached. This makes it possible to recharge a battery or super-capacitor even if a patient is not moving. The use of a permanent magnet coupling has potential advantages compared to traditional inductive or ultrasonic methods, e.g. in terms of tissue damage and transmission depth. Simulation results show the achievable coupling torque for different configurations of magnet geometries and relative positions between the driving magnet stack(s) and the harvester. It is shown that using a single magnet stack yields better results than using two diametrically opposite stacks. Measurements are performed with different magnets, driving frequencies and orientations of the harvester. The results are discussed and successful energy transfer was achieved regardless of the orientation of the device with respect to gravity, which is desirable for real world applications. Lateral misalignment between the harvester and the driving magnet can also be overcome. The largest distance of power transfer reached was 32 mm with the largest magnets tested, and the optimal power output into a resistive load was over 100 μW at a frequency of 25 Hz. The functional volume of the harvester is 1.85 cm3 – similar to the size of a wristwatch.
Otter W, Hu F, Hanham S, et al., 2016, Terahertz metamaterial devices, International Conference on Semiconductor Mid-IR and THz Materials and Optics (SMMO2016)
Leong JY, Zhang J, Reddyhoff T, et al., 2016, Confining of liquids under induced motion, Pages: 555-558
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