With the advent of neuronal oscillators in bioelectronic medicine, it has become increasingly important to understand the effect of magnetic fields on the biological rhythms they produce. In particular, cardiac pacemakers must be... more
With the advent of neuronal oscillators in bioelectronic medicine, it has become increasingly important to understand the effect of magnetic fields on the biological rhythms they produce. In particular, cardiac pacemakers must be resilient to the magnetic fields applied during magnetic resonance imaging, but it is not known whether the nonlinearity of the neuron response would amplify some the known effects of magnetic fields in semiconductor devices. Here, we have performed a series of experiments probing the oscillations of a silicon neuron in a static magnetic field of 3T applied in the plane of the substrate and perpendicular to it. The neuron was fabricated from complementary metal-oxide-semiconductor integrated circuits, which integrated currents in the nA range to compute the output of the Hodgkin-Huxley model. The experiment reveals a small magnetic field-induced dephasing of neuron oscillations which is slightly larger when the magnetic field is in the plane rather than per...
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This article provides a new approach to extract piezoelectric energy harvester properties, namely, capacitance and current, from the increase of voltage with time on a storage capacitor after full wave rectification. The work provides a... more
This article provides a new approach to extract piezoelectric energy harvester properties, namely, capacitance and current, from the increase of voltage with time on a storage capacitor after full wave rectification. The work provides a derivation of a more complete expression for the development of the output voltage with time, from which the equilibrium expression used in earlier publications appears as a limiting case. This new formulation enables an accurate estimate of the sinusoidal driving current and the shunt capacitance to be made without recourse to direct measurement. Using the analysis with both simulated and experimental data, a four‐step procedure is proposed that requires only the measurement of the initial slope of the voltage–time profile and the final settling value. This approach allows the much studied method of converting the piezoelectric output into charge stored on a capacitor to provide a unique indirect measurement method of the driving current and device ...
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Research Interests: Engineering, Condensed Matter Physics, Materials Science, Signal Processing, Mechanics of Materials, and 13 moreAnisotropy, Energy Harvesting, Porosity, DIELECTRIC, Composite Material, Ceramic, Smart Materials and Structures, CHEMICAL SCIENCES, Piezoelectricity, Dielectric Permittivity, Electrical And Electronic Engineering, Civil and Structural Engineering, and piezoelectric properties
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Recordings made directly from the nervous system are a key tool in experimental electrophysiology and the development of bioelectronic medicines. Analysis of these recordings involves the identification of signals from individual neurons,... more
Recordings made directly from the nervous system are a key tool in experimental electrophysiology and the development of bioelectronic medicines. Analysis of these recordings involves the identification of signals from individual neurons, a process known as spike sorting. A critical and limiting feature of spike sorting is the need to align individual spikes in time. However, electrophysiological recordings are made in extremely noisy environments that seriously limit the performance of the spike-alignment process. We present a new centroid-based method and demonstrate its effectiveness using deterministic models of nerve signals. We show that spike alignment in the presence of noise is possible with a 30 dB reduction in minimum SNR compared to conventional methods. We present a mathematical analysis of the centroid method, characterising its fundamental operation and performance. Further, we show that the centroid method lends itself particularly well to hardware realisation and we...
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Flexible pyroelectric energy generators provide unique features for harvesting temperature fluctuations which can be effectively enhanced using meshed electrodes that improve thermal conduction, convection and radiation into the... more
Flexible pyroelectric energy generators provide unique features for harvesting temperature fluctuations which can be effectively enhanced using meshed electrodes that improve thermal conduction, convection and radiation into the pyroelectric. In this paper, thermal radiation energy is continuously harvested with pyroelectric free standing Polyvilylidene Difluoride (PVDF) films over a large number of heat heat cycles using a novel micro-sized symmetrical patterned meshed electrode. It is shown that, for the meshed electrode geometries considered in this work, the polarisation-field (P-E), current-field (I-E) characteristics and device capacitance are unaffected since the fringing fields were generally small; this is verified using numerical simulations and comparison with experimental measurements. The use of meshed electrodes has been shown to significantly improve both the open circuit voltage (16 V to 59 V) and closed-circuit current (9 nA to 32 nA). The pyroelectric alternating c...
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This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3... more
This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3 ceramics for piezoelectric applications are manufactured for a range of relative densities, α = 0.30-0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3-0 composite and a 'composite in composite' model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients [Formula: see text]. It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy...
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Low temperature thermal to electrical energy converters have the potential to provide a route for recovering waste energy. In this paper, we propose a new configuration of a thermal harvester that uses a naturally driven thermal... more
Low temperature thermal to electrical energy converters have the potential to provide a route for recovering waste energy. In this paper, we propose a new configuration of a thermal harvester that uses a naturally driven thermal oscillator free of mechanical motion and operates between a hot heat source and a cold heat sink. The system exploits a heat induced liquid-vapour transition of a working fluid as a primary driver for a pyroelectric generator. The two-phase instability of a fluid in a closed looped capillary channel of an oscillating heat pipe (OHP) creates pressure differences which lead to local high frequency temperature oscillations in the range of 0.1–5 K. Such temperature changes are suitable for pyroelectric thermal to electrical energy conversion, where the pyroelectric generator is attached to the adiabatic wall of the OHP, thereby absorbing thermal energy from the passing fluid. This new pyroelectric-oscillating heat pipe (POHP) assembly of a low temperature genera...
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Detection and classification of electroneurogram (ENG) signals in the peripheral nervous system can be achieved by velocity selective recording (VSR) using multi-electrode arrays. This paper describes an implantable VSR-based ENG... more
Detection and classification of electroneurogram (ENG) signals in the peripheral nervous system can be achieved by velocity selective recording (VSR) using multi-electrode arrays. This paper describes an implantable VSR-based ENG recording system representing a significant development in the field since it is the first system of its type that can record naturally evoked ENG and be interfaced wirelessly using a low data rate transcutaneous link. The system consists of two CMOS ASICs one of which is placed close to the multi-electrode cuff array (MEC), whilst the other is mounted close to the wireless link. The digital ASIC provides the signal processing required to detect selectively ENG signals based on velocity. The design makes use of an original architecture that is suitable for implantation and reduces the required data rate for transmission to units placed outside the body. Complete measured electrical data from samples of the ASICs are presented that show that the system has t...
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While pathogenic bacteria contribute to a large number of globally important diseases and infections, current clinical diagnosis is based on processes that often involve culturing which can be time-consuming. Therefore, innovative,... more
While pathogenic bacteria contribute to a large number of globally important diseases and infections, current clinical diagnosis is based on processes that often involve culturing which can be time-consuming. Therefore, innovative, simple, rapid and low-cost solutions to effectively reduce the burden of bacterial infections are urgently needed. Here we demonstrate a label-free sensor for fast bacterial detection based on metal-oxide-semiconductor field-effect transistors (MOSFETs). The electric charge of bacteria binding to the glycosylated gates of a MOSFET enables quantification in a straightforward manner. We show that the limit of quantitation is 1.9×10(5) CFU/mL with this simple device, which is more than 10,000-times lower than is achieved with electrochemical impedance spectroscopy (EIS) and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-ToF) on the same modified surfaces. Moreover, the measurements are extremely fast and the sensor can be...
Research Interests: Materials Science, Chemistry, Analytical Chemistry, Biomedical Engineering, Mass Spectrometry, and 15 moreSemiconductors, Nanotechnology, Medicine, Optoelectronics, Humans, Escherichia coli, Dielectric Spectroscopy, Bacteria, Transistor, Bacterial infections, Equipment Design, Biosensing Techniques, Pathogenic Bacteria, Escherichia Coli Infections, and Field effect transistor
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This paper reports a simple and inexpensive method for preparing fine scale (Ø 260 μm) and high-density Magnéli phase (TinO2n−1) conductive ceramic fibres.
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A method is presented to reduce the interference pickup in nerve cuff recordings. The gains of differential amplifiers connected to the true tripole nerve cuff arrangement are tuned adaptively to null the residual EMG. Simulation results... more
A method is presented to reduce the interference pickup in nerve cuff recordings. The gains of differential amplifiers connected to the true tripole nerve cuff arrangement are tuned adaptively to null the residual EMG. Simulation results show that extraction of the neural signal is possible using this method without the need for high order filtering
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A method is presented that significantly reduces residual EMG artefacts in ENG recording systems. The closed-loop system is based on the true-tripole method however here the gains are adjusted automatically to reduce the EMG contamination
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In an effort to harvest thermal energy and exploit abundantly available waste heat the pyroelectric effect offers the opportunity to convert temperature fluctuations into useable electrical energy. Here, the micropatterning of the surface... more
In an effort to harvest thermal energy and exploit abundantly available waste heat the pyroelectric effect offers the opportunity to convert temperature fluctuations into useable electrical energy. Here, the micropatterning of the surface of a pyroelectric in order to enhance heat transfer and achieve faster and larger temperature fluctuations, which improve pyroelectric energy transformation, is reported. Methods for the fabrication of partially covered electrodes on polyvinylidene difluoride (PVDF) films are developed to investigate and quantify the benefits of such an electrode structure for pyroelectric energy harvesting. The micropattern consists of an array of holes that are etched into the upper aluminum electrodes of free standing ferroelectric PVDF films using a low cost photolithography and wet etching process. Under the application of infrared radiation heating, it is demonstrated that such microfeatures are able to significantly improve the open circuit voltage by 380% a...
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Research Interests: Engineering, Computer Science, Biomedical Engineering, Signal Processing, Neurophysiology, and 13 moreMedicine, Neural Prosthesis, Artificial Neural Networks, Noise, Biomedical Signal Processing, Delays, Electrodes, Action Potentials, Artificial Neural Network, Electrical And Electronic Engineering, Computer Science Neural Networks, Neural nets, and Waveform
Research Interests: Engineering, Electronic Engineering, Computer Science, Biomedical Engineering, Semiconductors, and 12 moreNeurophysiology, Medicine, Fourier Analysis, Computer Simulation, Cmos, Capacitor, Preamplifier, Electrodes, Equipment Design, Electrical And Electronic Engineering, Electric Capacitance, and Switched capacitor
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Research Interests: Materials Engineering, Materials Science, Biomedical Engineering, Electrochemistry, Cell Adhesion, and 15 moreDrug Discovery, Medicine, Adhesion, Biocompatibility, Animals, Cmos, Integrated Circuit, Aluminum oxide, Electrodes, Electrode, Biocompatible Materials, Equipment Design, Corrosion Inhibitor, Electrical Coupling, and Cell Membrane
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In this paper the design, fabrication and testing of a 10-channel array of identical amplifiers suitable for velocity selective electroneurogram (ENG) recording is described. The overall gain per channel is 10,000 and the total... more
In this paper the design, fabrication and testing of a 10-channel array of identical amplifiers suitable for velocity selective electroneurogram (ENG) recording is described. The overall gain per channel is 10,000 and the total input-referred rms noise in a bandwidth 1 Hz - 5 KHz is 290 nV per ...
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The effect of nonlinearity in the extrafascicular field in tripolar electrode cuffs on interference pick-up was investigated. It was concluded that the interference is sensitive to electrode separation, especially in short cuffs. This... more
The effect of nonlinearity in the extrafascicular field in tripolar electrode cuffs on interference pick-up was investigated. It was concluded that the interference is sensitive to electrode separation, especially in short cuffs. This suggests that significant improvements can be obtained by placing the end electrodes a few mm from the cuff ends.