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PatentReed S, Georgiou P, Constandinou TG, 2015,
Method and Apparatus for Sensing a Property of a Fluid
, 8,986,525 B2A device for sensing a property of a fluid comprising a first substrate having formed thereon a sensor configured in use to come into contact with a fluid in order to sense a property of the fluid, and a wireless transmitter for transmitting data over a wireless data link and a second substrate having formed thereon a wireless receiver for receiving data transmitted over said wireless link by said wireless transmitter. The first substrate is fixed to or within said second substrate. Additionally or alternatively, the device comprises a first substrate defining one or more microfluidic structures for receiving a fluid to be sensed and a second substrate comprising or having attached thereto a multiplicity of fluid sensors, the number of sensors being greater than the number of microfluidic structures. The second substrate is in contact with the first substrate such that at least one of the sensors is aligned with the or each microfluidic structure so as to provide an active sensor for the or each structure, and such that one or more of the sensors is or are not aligned with any microfluidic structure and is or are thereby redundant.
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Conference paperWilliams I, Luan S, Jackson A, et al., 2015,
Live Demonstration: A Scalable 32-Channel Neural Recording and Real-time FPGA Based Spike Sorting System
, 11th IEEE Annual Biomedical Circuits and Systems Conference (BioCAS), Publisher: IEEE, Pages: 187-187, ISSN: 2163-4025- Author Web Link
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- Citations: 1
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Conference paperLauteslager T, Nicolaou N, Lande TS, et al., 2015,
Functional neuroimaging using UWB impulse radar: A feasibility study.
, Publisher: IEEE, Pages: 1-4 -
Conference paperDemarchou E, Georgiou J, Nicolaou N, et al., 2014,
Anesthetic-induced changes in EEG activity: a graph theoretical approach
, IEEE Biomedical Circuits and Systems (BioCAS) Conference, Pages: 45-48The dynamic brain networks forming during wakefulness and anesthetic-induced unconsciousness are investigated using time-delayed correlation and graph theoretical measures. Electrical brain activity (EEG) from 10 patients under propofol anesthesia during routine surgery is characterized using the shortest path length, λ, and clustering, c, extracted from time delayed correlation. An increase in λ and c during anesthesiareveals disruption of long-range connections and emergence of more localized neighborhoods. These changes were not a result of volume conduction, as were based on time-delayed correlation. Our observations are in line with theories of anesthetic action and support the use of graph theoretic measures to study emerging brain networks during wakefulness and anesthesia.
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Journal articleParaskevopoulou SE, Wu D, Eftekhar A, et al., 2014,
Hierarchical Adaptive Means (HAM) Clustering for Hardware-Efficient, Unsupervised and Real-time Spike Sorting.
, Journal of Neuroscience Methods, Vol: 235, Pages: 145-156, ISSN: 1872-678XThis work presents a novel unsupervised algorithm for real-time adaptive clustering of neural spike data (spike sorting). The proposed Hierarchical Adaptive Means (HAM) clustering method combines centroid-based clustering with hierarchical cluster connectivity to classify incoming spikes using groups of clusters. It is described how the proposed method can adaptively track the incoming spike data without requiring any past history, iteration or training and autonomously determines the number of spike classes. Its performance (classification accuracy) has been tested using multiple datasets (both simulated and recorded) achieving a near-identical accuracy compared to k-means (using 10-iterations and provided with the number of spike classes). Also, its robustness in applying to different feature extraction methods has been demonstrated by achieving classification accuracies above 80% across multiple datasets. Last but crucially, its low complexity, that has been quantified through both memory and computation requirements makes this method hugely attractive for future hardware implementation.
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Journal articleLuan S, Williams I, Constandinou TG, et al., 2014,
Neuromodulation: present and emerging methods
, Frontiers of Neuroengineering, Vol: 7, ISSN: 1662-6443Neuromodulation has wide ranging potential applications in replacing impaired neural function (prosthetics), as a novel form of medical treatment (therapy), and as a tool for investigating neurons and neural function (research). Voltage and current controlled electrical neural stimulation (ENS) are methods that have already been widely applied in both neuroscience and clinical practice for neuroprosthetics. However, there are numerous alternative methods of stimulating or inhibiting neurons. This paper reviews the state-of-the-art in ENS as well as alternative neuromodulation techniques - presenting the operational concepts, technical implementation and limitations - in order to inform system design choices.
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Journal articleWilliams I, Constandinou TG, 2014,
Computationally Efficient Modelling of Proprioceptive Signals in the Upper Limb for Prostheses: a Simulation Study
, Frontiers in Neuroscience, Vol: 8, Pages: 1-13Accurate models of proprioceptive neural patterns could one day play an important role in the creation of an intuitive proprioceptive neural prosthesis for amputees. This paper looks at combining efficient implementations of biomechanical and proprioceptor models in order to generate signals that mimic human muscular proprioceptive patterns for future experimental work in prosthesis feedback. A neuro-musculoskeletal model of the upper limb with 7 degrees of freedom and 17 muscles is presented and generates real time estimates of muscle spindle and Golgi Tendon Organ neural firing patterns. Unlike previous neuro-musculoskeletal models, muscle activation and excitation levels are unknowns in this application and an inverse dynamics tool (static optimisation) is integrated to estimate these variables. A proprioceptive prosthesis will need to be portable and this is incompatible with the computationally demanding nature of standard biomechanical and proprioceptor modelling. This paper uses and proposes a number of approximations and optimisations to make real time operation on portable hardware feasible. Finally technical obstacles to mimicking natural feedback for an intuitive proprioceptive prosthesis, as well as issues and limitations with existing models, are identified and discussed.
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Journal articleEftekhar A, Juffali W, El-Imad J, et al., 2014,
Ngram-derived Pattern Recognition for the Detection and Prediction of Epileptic Seizures
, PLOS One, Vol: 9, Pages: 1-15This work presents a new method that combines symbol dynamics methodologies with an Ngram algorithm for the detection and prediction of epileptic seizures. The presented approach specifically applies Ngram-based pattern recognition, after data pre-processing, with similarity metrics, including the Hamming distance and Needlman-Wunsch algorithm, for identifying unique patterns within epochs of time. Pattern counts within each epoch are used as measures to determine seizure detection and prediction markers. Using 623 hours of intracranial electrocorticogram recordings from 21 patients containing a total of 87 seizures, the sensitivity and false prediction/detection rates of this method are quantified. Results are quantified using individual seizures within each case for training of thresholds and prediction time windows. The statistical significance of the predictive power is further investigated. We show that the method presented herein, has significant predictive power in up to 100% of temporal lobe cases, with sensitivities of up to 70–100% and low false predictions (dependant on training procedure). The cases of highest false predictions are found in the frontal origin with 0.31–0.61 false predictions per hour and with significance in 18 out of 21 cases. On average, a prediction sensitivity of 93.81% and false prediction rate of approximately 0.06 false predictions per hour are achieved in the best case scenario. This compares to previous work utilising the same data set that has shown sensitivities of up to 40–50% for a false prediction rate of less than 0.15/hour.
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Journal articleLeene LB, Constandinou TG, 2014,
Ultra-low power design strategy for two-stage amplifier topologies
, Electronics Letters, Vol: 50, Pages: 583-585, ISSN: 0013-5194A novel two-stage amplifier topology and ultra-low power design strategy for two-stage amplifiers that utilises pole zero cancellation to address the additional power requirements for stability are presented. For a 288 nA total bias, the presented amplifier achieves a 1.07 MHz unity gain frequency with a 8560 pF MHz/mA figure of merit.
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Journal articleLuan S, Constandinou TG, 2014,
A Charge-Metering Method for Voltage-Mode Neural Stimulation
, Journal of Neuroscience Methods, Vol: 224, Pages: 39-47, ISSN: 0165-0270Electrical Neural Stimulation is the technique used to modulate neural activity by inducing an instantaneous charge imbalance. This is typically achieved by injecting a constant current and controlling the stimulation time. However, constant voltage stimulation is found to be more energy-efficient although it is challenging to control the amount of charge delivered. This paper presents a novel, fully-integrated circuit for facilitating charge-metering in constant voltage stimulation. It utilises two complementary stimulation paths. Each path includes a small capacitor, a comparator and a counter. They form a mixed-signal integrator that integrates the stimulation current onto the capacitor whilst monitoring its voltage against a threshold using the comparator. The pulses from the comparator are used to increment the counter and reset the capacitor. Therefore, by knowing the value of the capacitor, threshold voltage and output of the counter, the quantity of charge delivered can be calculated. The system has been fabricated in 0.18μm CMOS technology, occupying a total active area of 339μm×110μm. Experimental results were taken using: (1) a resistor-capacitor EEI model and (2) platinum electrodes with ringer solution. The viability of this method in recruiting action potentials has been demonstrated using a cuff electrode with Xenopus Sciatic nerve. For a 10nC target charge delivery, the results of (2) show a charge delivery error of 3.4% and a typical residual charge of 77.19pC without passive charge recycling. The total power consumption is 45μW. The performance is comparable with other publications. Therefore, the proposed stimulation method can be used as a new approach for neural stimulation.
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Conference paperGuven O, Eftekhar A, Hoshyar R, et al., 2014,
Realtime ECG Baseline Removal: An Isoelectric Point Estimation Approach
, IEEE Biomedical Circuits and Systems (BioCAS) Conference, Pages: 29-32This paper presents a novel method for ECG baseline drift removal while preserving the integrity of the ST segment. Baseline estimation is achieved by tracking 3 isoelectric points within the ECG waveform as fiducial markers used in an interpolation filter. These points are determined relative to the QRS complex, which is extracted using a known method (Pan-Tompkins algorithm). The proposed algorithm has been tested extensively using synthetic signals and also validated with real data. The synthetic signals assume a 2mV p-p ECG signal and 300uV p-p baseline drift in the presence of noise artefacts including EMG pickup (20 dB – max. 200uV), and residual power-line interference (50uV p-p). The results show a maximum (worst-case ST-segment distortion) error of 34.7uV (mean), 27.8uV (median) and 21.2uV (std. dev.) across 50 randomly generated synthetic ECG signals each containing 100 heartbeats. Validation of the algorithm applied to signals from the MIT-BIH arrhythmia databases reveals maximum error per P-T intervalwith mean, median and std. dev. of 34.4uV, 35.2uV and 9.6uV respectively with suppressed motion artefacts.
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Conference paperYoshizaki S, Serb A, Liu Y, et al., 2014,
Octagonal CMOS Image Sensor with Strobed RGB LED Illumination for Wireless Capsule Endoscopy
, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 1857-1860 -
Conference paperYang Y, Boling S, Eftekhar A, et al., 2014,
Computationally efficient feature denoising filter and selection of optimal features for noise insensitive spike sorting
, IEEE Annual Meeting of the Engineering in Biology and Medicine Society (EMBC), Publisher: IEEE -
Conference paperReverter F, Prodromakis T, Liu Y, et al., 2014,
Design Considerations for a CMOS Lab-on-Chip Microheater Array to Facilitate the in vitro Thermal Stimulation of Neurons
, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 630-633 -
Book chapterShepherd LM, Constandinou TG, Toumazou C, 2014,
Towards ultra-low power bio-inspired processing
, Body Sensor Networks, Publisher: Springer London, Pages: 273-299, ISBN: 9781447163732The natural world is analogue and yet the modern microelectronic world with which we interact represents real world data using discrete quantities manipulated by logic. In the human space, we are entering a new wave of body-worn biosensor technology for medical diagnostics and therapy. This new trend is beginning to see the processing interface move back to using continuous quantities, which are more or less in line with the biological processes. We label this computational paradigm “bio-inspired” because of the ability of silicon chip technology which enables the use of inherent device physics, allowing us to approach the computational efficiencies of biology. From a conceptual viewpoint, this has led to a number of more specific morphologies including neuromorphic and retinomorphic processing. These have led scientists to model biological systems such as the cochlea and retina and gain not only superior computational resource efficiency (to conventional hearing aid or camera technology), but also an increased understanding of biological and neurological processes.
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Journal articleNavajas J, Barsakcioglu D, Eftekhar A, et al., 2014,
Minimum Requirements for Accurate and Efficient Real-Time On-Chip Spike Sorting
, Journal of Neuroscience Methods, Pages: 51-64 -
Journal articleBarsakcioglu D, Liu Y, Bhunjun P, et al., 2014,
An Analogue Front-End Model for Developing Neural Spike Sorting Systems
, IEEE Transactions on Biomedical Circuits and Systems, Vol: 8, Pages: 216-227 -
Conference paperZheng L, Leene L, Liu Y, et al., 2014,
An Adaptive 16/64 kHz, 9-bit SAR ADC with Peak-Aligned Sampling for Neural Spike Recording
, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 2385-2388 -
Conference paperWilliams I, Constandinou TG, 2013,
Modelling muscle spindle dynamics for a proprioceptive prosthesis
, Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBS), Publisher: IEEEMuscle spindles are found throughout our skeletalmuscle tissue and continuously provide us with a sense of our limbs position and motion (proprioception). This paper advances a model for generating artificial muscle spindle signalsfor a prosthetic limb, with the aim of one day providing amputees with a sense of feeling in their artificial limb. By utilising the Opensim biomechanical modelling package the relationship between a joints angle and the length of surrounding muscles is estimated for a prosthetic limb. This is then applied to the established Mileusnic model to determine the associated muscle spindle firing pattern. This complete system model is then reduced to allow for a computationallyefficient hardware implementation. This reduction is achieved with minimal impact on accuracy by selecting key monoarticular muscles and fitting equations to relate joint angle to muscle length. Parameter values fitting the Mileusnic modelto human spindles are then proposed and validated against previously published human neural recordings. Finally, a model for fusimotor signals is also proposed based on data previously recorded from reduced animal experiments.
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Conference paperLeene LB, Luan S, Constandinou TG, 2013,
A 890fJ/bit UWB transmitter for SOC integration inhigh bit-rate transcutaneous bio-implants
, IEEE International Symposium on Circuits and Systems (ISCAS)The paper presents a novel ultra low power UWBtransmitter system for near field communication in transcutaneous biotelemetries. The system utilizes an all-digital architecture based on minising the energy dissipated per bit transmitted by efficiently encoding a packet of pulses with multiple bits and utilizing oscillator referenced delays. This is achieved by introducing a novel bi-phasic 1.65 pJ per pulse UWB pulse generator together with a 72uμW DCO that provide a transmission bandwidth of 77.5 Mb/s with an energy efficiency of 890fJ per bit from a 1.2V supply. The circuit core occupies a compact silicon footprint of 0.026mm2 in a 0.18 μm CMOS technology.
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