Publications
264 results found
Casadevall i Solvas X, Prodromakis T, Turek V, et al., 2012, Microfluidic evaporator for on-chip sample concentration, Lab on A Chip
Prodromakis T, Chua LO, 2012, Two Centuries of Memristors, Chaos, CNN, Memristors and Beyond, Publisher: World Scientific
Gelencsér A, Prodromakis T, Toumazou C, et al., 2011, A Biomimetic Model of the Outer Plexiform Layer by Incorporating Memristive Devices, Nature Precedings
In this paper we present a biorealistic model for the first part of the early vision processing by incorporating memristive nanodevices. The architecture of the proposed network is based on the organisation and functioning of the outer plexiform layer (OPL) in the vertebrate retina. We demonstrate that memristive devices are indeed a valuable building block for neuromorphic architectures, as their highly non-linear and adaptive response could be exploited for establishing ultra-dense networks with similar dynamics to their biological counterparts. We particularly show that hexagonal memristive grids can be employed for faithfully emulating the smoothing-effect occurring at the OPL for enhancing the dynamic range of the system. In addition, we employ a memristor-based thresholding scheme for detecting the edges of grayscale images, while the proposed system is also evaluated for its adaptation and fault tolerance capacity against different light or noise conditions as well as distinct device yields.
Rao C, Chaudhry UA, Camelliti P, et al., 2011, Abstract 10748: Structured Culture Scaffolds Force the Maturation of Calcium Transients in Rat Neonatal Ventricular Myocytes, Circulation, Scientific Sessions 2011, Publisher: American Heart Association, ISSN: 0009-7322
Ibrahim M, Lazarevic SM, Siedlecka U, et al., 2011, Abstract 10542: Telethonin Regulates Transverse Tubule Structure and Ca2+ Induced Ca2+ Release in Mouse Ventricular Myocytes, Circulation, Scientific Sessions 2011, Publisher: American Heart Association, ISSN: 0009-7322
Liu Y, Georgiou P, Prodromakis T, et al., 2011, An Extended CMOS ISFET Model Incorporating the Physical Design Geometry and the Effects on Performance and Offset Variation, IEEE Transactions on Electron Devices, Vol: 58, Pages: 4414-4422, ISSN: 0018-9383
This paper presents an extended model for theCMOS-based Ion-Sensitive-Field-Effect-Transistor (ISFET), incorporating design parameters associated with the physicalgeometry of the device. This can, for the first time, provide a good match between calculated and measured characteristics bytaking into account the effects of non-idealities such as threshold voltage variation and sensor noise. The model is evaluated through a number of devices with varying design parameters (chemical sensing area and MOSFET dimensions) fabricated ina commercially-available 0.35μm CMOS technology. Threshold voltage, subthreshold slope, chemical sensitivity, drift and noisewere measured and compared to the simulated results. The first and second order effects are analysed in detail and it is shown that the sensors’ performance was in agreement with the proposed model.
Prodromakis T, Peh BP, Papavassiliou C, et al., 2011, A Versatile Memristor Model With Non-linear Dopant Kinetics, IEEE Transactions on Electron Devices, Vol: 58, Pages: 3099-3105, ISSN: 0018-9383
Georgiou P, Prodromakis T, Constandinou TG, et al., 2011, Sensor Array for Measuring Neural Activity
A sensor system comprising a substrate and integrated onto the substrate an array (7) of sensor elements (1), each sensor element comprising one or more inductors (3), one or more electrochemical sensors (4), and one or more optical sensors (2). The system further comprising a controller configured in use to separately address each of the sensor elements (1) to drive the respective inductors and receive outputs of the respective sensors.
Goh ZDC, Georgiou P, Constandinou TG, et al., 2011, A CMOS-based ISFET Chemical Imager with Auto-Calibration Capability, IEEE Sensors Journal, Vol: 11, Pages: 3253-3260, ISSN: 1530-437X
This paper presents a novel auto-calibration technique for eliminating sensor mismatch in CMOS-based chemical imagers. Designed using an 8x8 array comprising of pH sensitive Ion Sensitive Field Effect Transistors (ISFETs), the chemical imager is capable of implementing a gradient based calibration algorithm by biasing programmable-gate (PG) ISFETs at a common operating point when exposed to a solution of homogenous pH. The system was fabricated in a typical 0.35um CMOS technology and demonstrated a fast rate of convergence (500ms per iteration) while a convergence accuracy of 45mV on a gain of 10 (0.5% relative standard error and 2% pixel-to-pixel variation) was achieved. A maximum pH sensitivity of 57mV/pH is also reported.
Goh ZDC, Georgiou P, Constandinou TG, et al., 2011, Live demonstration: A CMOS-based lab-on-chip array for combined magnetic manipulation and opto-chemical sensing, IEEE International Symposium on Circuits and Systems (ISCAS), Pages: 1997-2001, ISSN: 0271-4302
Prodromakis T, Liu Y, Toumazou C, 2011, A Low-Cost Disposable Chemical Sensing Platform Based on Discrete Components, IEEE Electron Device Letters, Vol: 32, Pages: 417-419
A method of fabricating low-cost chemical sens- ing platforms is presented. The device utilizes a discrete metal–oxide–semiconductor field-effect transistor to detect ionic concentrations in electrolytes, with particular emphasis to pH. Measured results indicate a chemical sensitivity of 36.5 mV/pH, while the device exhibits low-leakage currents (in picoamperes) and a drift of 9 mV/h. The proposed technique has a great potential for disposable implementations, while the sensing selectivity of the device can be easily altered, resulting into a versatile platform.
Rao C, Ali NA, Yacoub MH, et al., 2011, The Use of Induced Pluripotent Stem Cell Derived Cardiomyocytes as a Model of Human Disease, Aswan Heart Science Centre: Science and Practice Series
Goh ZDC, Georgiou P, Constandinou TG, et al., 2011, A CMOS-based Lab-on-Chip Array for Combined Magnetic Manipulation and Opto-Chemical Sensing, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 1998-2001, ISSN: 0271-4302
Prodromakis T, Liu Y, Yang J, et al., 2011, A Novel Design Approach for Developing Chemical Sensing Platforms Using Inexpensive Technologies, Proceedings of the IEEE Biomedical Circuits and Systems (BioCAS) Conference
Goh ZDC, Georgiou P, Constandinou TG, et al., 2011, A CMOS-Based Lab-on-Chip Array for Combined Magnetic Manipulation and Opto-Chemical Sensing, IEEE International Symposium on Circuits and Systems (ISCAS), Publisher: IEEE, Pages: 1997-2001
This paper presents a CMOS-based lab-on-chip platform for combined magnetic manipulation and opto-chemical sensing. Within each pixel, a Programmable Gate (PG) ISFET chemical sensor is combined with an active pixel sensor, and is encompassed within an inductive coil. The integrated pixel is tesselated to form an 8×8 array. Fabricated in a commercially available 0.35um CMOS technology, the system can be used for simultaneous optical imaging and pH sensing, and includes auto- calibration mechanisms for eliminating sensor non-idealities. A spatiotemporal magnetic field pattern generator has also been embedded for micro-scale magnetic manipulation. Controlled via a MATLAB based graphical user interface, the system achieves real time data acquisition at 6fps, a pH sensitivity of 57mV/pH and demonstrates magnetic manipulation of micro-beads.
Goh CZD, Georgiou P, Constandinou TG, et al., 2011, A CMOS based ISFET Chemical Imager with Auto-Calibration Capability, IEEE Sensors Journal
Liu Y, Georgiou P, Prodromakis T, et al., 2011, An Extended CMOS ISFET Model Incorporating the Physical Design Geometry and the Effects on Performance and Offset Variation, IEEE Transactions on Electron Devices
Rao C, Chaudhry U, Al-Saud SA, et al., 2011, Structured Culture Scaffolds force the Maturation of Calcium Transients in Rat Neonatal Ventricular Myocytes, Proceedings of The Physiological Society, Physiology 2011, ISSN: 1749-6187
Prodromakis T, Liu Y, Toumazou C, 2011, Low-cost Implementations of pH Monitoring Platforms, IEEE Sensors
Cserey G, Rák Á, Jákli B, et al., 2010, Cellular Nonlinear Networks with Memristive Cell Devices, IEEE International Conference on Electronics, Circuits, and Systems
In this paper, we present (simulation) measurements of a memristor crossbar device. We designed a PCB memristor package and the appropriate measurement board. Technical details of these circuits are presented. Cellular like topology of this crossbar device can provide high density and local connectivity. Our simulation results show that a memristor crossbar can be used as a weight matrix of a cellular neural network. We gave a formula to evaluate the direction of the change of the states of the memristor array in case of a given voltage input.
Prodromakis T, Toumazou C, 2010, A Review on Memristive Devices and Applications, IEEE International Conference on Electronics, Circuits, and Systems
Recent discovery of the memristor has sparked a new wave of enthusiasm and optimism in revolutionising circuit design, marking a new era for the advancement of neuromorphic and analogue applications. In this work, we consider practical applications in which the highly non-linear dynamic response of the memristor can be employed. It is shown that the device can be utilised as a non-volatile memory element and/or a programmable dynamic load, with particular emphasis given into bio-inspired analog implementations that typically exploit the ability of the memristor to support both logic and memory simultaneously. Finally, a novel concept is presented demonstrating the capacity of memristive networks in realising demanding image processing algorithms and more specifically edge detection.
Zain WSW, Prodromakis T, Toumazou C, 2010, A Bulk-Driven ISFET-Based Chemical Mixer, Proceedings of the IEEE Biomedical Circuits and Systems (BioCAS) Conference, Publisher: IEEE
In this work the concept of the chemical mixerfor comparing the pH of two aqueous solutions is introduced. Ionic concentrations are sensed via a pair of ISFETs, which are then translated into signals with frequencies that correspond to the pH values of the solutions. Using the bulk-driven single balanced topology, the number of transistors is significantly reduced, making it suitable for applications where a low supply voltage and low power consumption are essential. Finally, it is demonstrated that the output frequency of the mixer depends on the ΔpH of the solutions under test.
Prodromakis T, Michelakis K, Toumazou C, 2010, Fabrication and Electrical Characteristics of Memristors with TiO2/TiO2+x active layers, IEEE International Symposium on Circuits and Systems
We report on the fabrication and electrical characterisation of memristors with TiO2/TiO2+x active layer. This active layer is deposited at room temperature with RF-sputtering and consists of two sub-layers, the top one of which containsexcess oxygen atoms. Electrical characterisation of the devices demonstrates similar switching characteristics as previously reported for nano-scale memristors with TiO2/TiO2−x active cores.
Prodromakis T, Liu Y, Constandinou TG, et al., 2010, Exploiting CMOS Technology to Enhance the Performance of ISFET Sensors, IEEE Electron Device Letters, Vol: 31, Pages: 1053-1055, ISSN: 0741-3106
This paper presents a novel method for fabricating ISFET devices in unmodified CMOS technologies. Conventional CMOS ISFETs utilise the protective passivation coating as the sensing membrane, with the sensed potential being coupled down to the floating MOS gate via a stack of conducting and insulating layers. The proposed structure minimises the use of these layers by exploiting the passivation opening mask, normally intended for bondpad openings. Parasitic effects such as reduced transconductance and trapped charge within the floating gate structure are minimised, resulting in a lower VT and improved chemical transconductance efficiency. Other characteristics including chemical sensitivity, reference leakage current and noise power are at comparable levels with conventional CMOS-based ISFET devices.
Prodromakis T, Konstantinidis G, Papavassiliou C, et al., 2010, Interfacial polarisation on gallium arsenide membranes, Micro & Nano Letters, IET, Vol: 5, Pages: 178-180, ISSN: 1750-0443
An investigation on the dielectric properties of gallium arsenide membranes is presented. Particularly, the authors exploit the interfacial polarisation effect of microstrip and coplanar transmission lines on multilayered membrane structures. Such structures are in favour with the Maxwell-Wagner polarisation, which can be used for resembling the dielectric characteristics of high-k materials. The authors demonstrate a technique for attaining large slowing factors while the corresponding dielectric losses are significantly reduced.
Michelakis K, Prodromakis T, Toumazou C, 2010, Cost-effective fabrication of nanoscale electrode memristors with reproducible electrical response, Micro & Nano Letters, Vol: 5, Pages: 91-94, ISSN: 1750-0443
This Letter aims to promote basic research into memristors, which will help provide theorists with much-needed reliable benchmarks and will also aid the technology progress. It addresses an information gap presently in the literature on simple microfabrication techniques for the realisation of such devices. Consequently, a fabrication method is reported for implementing the full active-material stack, requiring a single lithography and evaporation step. A cost-effective technique that can reliably shrink device lateral dimensions towards the nanoscale is also demonstrated. Experimental results confirm the suitability of the proposed methods for fabricating memristors of varying dimensions that exhibit consistent electrical characteristics.
Prodromakis T, Papavassiliou C, 2010, An Experimental Technique for Characterizing Slow-Wave Characteristics of MIS-Like Transmission Lines Using Aqueous Dielectrics, Transactions on Microwave Theory and Techniques, Vol: 58, Pages: 985-993
This work is a study of the dielectric propagation properties of laminar substrates, which are known to support low dispersion modes with very small phase velocities. Slow modes are linked to a polarization mode supported by the insulator–semiconductor interface. The mode spectrum of metal–insulator–semiconductor lines is controlled by the substrate resistivity and the ratio of the semiconductor to insulator layer thicknesses. An experimental investigation of substrate modes normally requires the laborious fabrication of many specimens to cover a useful range of parameter variation. In this paper, we present an experimental platform that supports slow-wave propagation and allows easy adjustment of the parameters affecting the interfacacial polarization mechanism.
Constandinou TG, Georgiou P, Prodromakis T, et al., 2010, A CMOS-based Lab-on-Chip Array for the Combined Magnetic Stimulation and Opto-Chemical Sensing of Neural Tissue, Berkeley, CA, 2010 12th International Workshop on Cellular Nanoscale Networks and their Applications (CNNA), Publisher: IEEE, Pages: 1-6
This paper presents a novel CMOS-based lab-on-chip platform for non-contact magnetic stimulation and recording of neural tissue. The proposed system is the first of its kind to integrate magnetic-stimulation and opto-chemical sensing in a single pixel, tesselated to form an 8 à 8 array. Fabricated in a commercially-available 0.35 ¿m CMOS technology, the system can be intrinsically used for both optical imaging and pH sensing and includes mechanisms for calibrating out sensor variation and mismatch. In addition to sensory acquisition via an integrated 10-bit ADC, a 64-instruction spatiotemporal pattern generator has been embedded within the array for driving the microscale magnetic neural stimulation. In this application the ISFET-based sensors are used to capacitively-couple neuronal charge in close proximity to the floating gate. Optical imaging hardware has also been embedded to provide topographic detail of the neural tissue.
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