Chris Toumazou's research while affiliated with Imperial College London and other places

Publications (131)

Conference Paper
The growing cancer burden necessitates the development of cost-effective solutions that provide rapid, precise and personalised information to improve patient outcome. The aim of this study was to develop a novel, Lab-on-Chip compatible method for the detection and quantification of DNA methylation for MGMT, a well-established molecular biomarker f...
Conference Paper
This paper introduces a novel Python script which automates the design process of cancer variant-specific DNA probes, based on the amplification method LAMP (Loop-Mediated Isothermal Amplification). With just an input of the DNA sequence and the mutation base location, the script outputs suggestions of two best fitting primer sets for a given targe...
Preprint
A Deep Autoencoder based content retrieval algorithm is proposed for prediction and differentiation of cancer types based on the presence of epigenetic patterns of DNA methylation identified in genetic regions known as CpG islands. The developed deep learning system uses a CpG island state classification sub-system to complete sets of missing/incom...
Article
Full-text available
Background and objective: Current prototypes of closed-loop systems for glucose control in type 1 diabetes mellitus, also referred to as artificial pancreas systems, require a pre-meal insulin bolus to compensate for delays in subcutaneous insulin absorption in order to avoid initial post-prandial hyperglycemia. Computing such a meal bolus is a ch...
Conference Paper
This paper presents an ISFET sensor pair configured as a traditional MOSFET current mirror. The circuit provides differential pH sensing suitable for DNA detection that requires two or more samples with drift and temperature compensation for thermal cycling. The ISFET current mirror fabricated in unmodified CMOS process gives an exponential respons...
Article
Full-text available
This work describes the preparation of an array of individually addressable pH sensitive microneedles which are sensitized by electrodepositing iridium oxide. The impact of the deposition potential, storage conditions and interferents on the sensor characteristics such as slope, offset, intra- and inter-batch reproducibility is investigated. The de...
Conference Paper
This paper presents a pH-based System-on-Chip DNA methylation quantification platform for real time monitoring of DNA methylation ratio in target genes. The architecture forms a novel autonomous system, capable of providing diagnostic information on the progression of a disease, notably cancer. The system is equipped with drift and trapped charge c...
Article
Full-text available
Vital signs are usually recorded at 4-8 h intervals in hospital patients, and deterioration between measurements can have serious consequences. The primary study objective was to assess agreement between a new ultra-low power, wireless and wearable surveillance system for continuous ambulatory monitoring of vital signs and a widely used clinical vi...
Article
Background and objectives Vital signs are usually recorded at 4–8 h intervals in hospital patients, and deterioration between measurements can have serious consequences. The primary study objective was to assess agreement between a new ultra-low power, wireless and wearable surveillance system for continuous ambulatory monitoring of vital signs and...
Conference Paper
Full-text available
Good control of glucose in diabetes requires minimisation of high and low blood glucose excursions and is critical to reducing the incidence of complications and improving quality of life. A closed-loop insulin delivery system consisting of a glucose sensor, a controller and an insulin pump, has the potential to achieve this and be life changing. W...
Article
The electrical detection of DNA methylation based biomarkers using semiconductor technology shows great promise for early cancer screening. Presented is the very first proof-of-concept example of using CMOS-based technology for real-time DNA methylation detection using Ion-Sensitive Field-Effect Transistors (ISFETs). An electrochemical label-free a...
Article
Volatility is a key parameter when measuring the size of errors made in modelling returns and other financial variables such as exchanged rates. The autoregressive moving-average (ARMA) model is a linear process in time series; whilst in the nonlinear system, the generalised autoregressive conditional heteroskedasticity (GARCH) and Markov switching...
Article
This paper investigates the surface modification of Parylene-C thin films under various oxygen plasma treatment conditions, such as power intensity (50:400 W) and exposure time (1:20 min). The extent of hydrophilicity was investigated through contact angle measurements, and correlations between treatment parameters, film thickness, restoration of h...
Conference Paper
This paper presents a novel ISFET based readout system by minimizing the analogue instrumentation. Quantization of sensed pH is realized by means of a novel ISFET pH-to-Time sensor integrated with a time to digital converter (TDC). By using this scheme, interference usually introduced in the analogue front end can be minimized, and time based signa...
Article
Full-text available
We report the development of a novel multi-tier interface which enables the wireless, non-invasive transfer of sufficient amounts of power as well as the collection and transmission of data from low-power, deeply implantable analog sensors. The interface consists of an inductive coupling sub-system and an ultrasonic sub-system. The designed and exp...
Conference Paper
This preliminary study reports on the combined use of wireless accelerometers and wireless EMG sensors for monitoring walking patterns. The sensor data was analyzed in frequency domain through FFT, PSD and time-frequency spectrogram analysis. Accelerometer spectra was found to shift towards lower frequencies (;50 Hz) during asymmetric walking. Medi...
Article
This paper presents an overview of how semiconductor technology is now being used for early detection and therapy of disease. Specifically three areas are described which are currently utilising CMOS technology with tremendous benefit in healthcare. The first being in mobile health whereby CMOS technology enables implementation of a low power intel...
Article
This article presents a personal account of the life and scientifi c journey of Professor Piet Bergveld, the inventor and founding father of the Ion-Sensitive Field Effect Transistor (ISFET). The interview gives a unique overview of how ISFET technology has evolved over the years, and the challenges faced during the development from its initial use...
Article
Variations of the coupling between two inductors in the presence of a strong electrolyte with varying pH value is investigated. Inductors were placed at a distance of 15.875 mm apart. S12 parameters were measured and used as an indicator to the strength of coupling between the two inductors. The pH of the electrolyte solution was reduced from 4.2 t...
Article
We present ion-sensitive field effect transistor-based sensors, integrated with a microfluidic chip, for monitoring pH and potassium cations. The sensor is strategically located at the base of a well so that the response time of the device depends both on the mean flow through the device and the diffusion coefficient of the analyte being monitored....
Article
A method of fabricating low-cost chemical sensing 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...
Article
The use of closely coupled inductors, operating in the region of 10 MHz to 1 GHz, for detection of change in the concentration of ionic species present in a liquid sample, is reported here. The S-parameters were measured for the coupled inductors with liquid samples under varying pH conditions on one inductor only. S12 parameters were used as an in...
Article
We present here, an open-source printed circuit board (PCB) platform for the prototyping, testing and trialing of non-invasive oximeter devices. The system is designed around a dspic33fj128gp804 microcontroller with coding in C. It can control over 100 LED and photodiode devices and has two modes, one for calibration and one for signal interrogatio...
Article
This letter presents a novel method for fabricating ion-sensitive field-effect transistor (ISFET) devices in unmodified CMOS technologies. Conventional CMOS ISFETs utilize 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....
Article
Full-text available
We present a quantitative model for the phototransduction cascade in Drosophila photoreceptors. The process consists of four stages: (1) light absorption by Rhodopsin, (2) signal amplification phase mediated by a G-protein coupled cascade, (3) closed/open state kinetics of the transient receptor potential (TRP) ion channels which regulate the ionic...
Conference Paper
Recently we have completed a system level modelling of the G-protein coupled cascade in Drosophila photoreceptors that converts single photons into transient electrical responses. Many interesting properties were revealed including the underlying mechanisms by which the system generates high quantum efficiency, single photon responses, huge signal...
Conference Paper
In this paper, a novel chemical sensor system utilizing an Ion-Sensitive Field Effect Transistor (ISFET) for pH measurement is presented. Compared to other interface circuits, this system uses auto-zero amplifiers with a pingpong control scheme and array of Programmable-Gate Ion-Sensitive Field Effect Transistor (PG-ISFET). By feedback controlling...
Conference Paper
This paper presents an integrated silicon pancreatic islet to be used for the control algorithm of an artificial pancreas. The system replicates the temporal behaviour of the electrophysiology of the alpha and beta cells which are located in the islet of Langerhans in the pancreas, generating signals which can be used to infuse the two regulatory h...
Conference Paper
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 × 8 array. Fabricated in a commercially-available 0.35 ¿m CMOS technolo...
Conference Paper
This paper presents a novel configuration for Ion sensitive Field Effect Transistors (ISFETs) to be used as a threshold detector during a Single Nucleotide Polymorphism (SNP) base pair match. ISFET-based inverters are used as reaction threshold detectors to convey the chemical reaction level to a logic output once a threshold has been reached. Usin...
Article
A fully balanced highly linear CMOS operational transconductance amplifier (OTA) is presented. The proposed circuit combines a cross-coupled channel length modulation cell with a tunable-gain current mirror. Good linearity over a wide tuning range is achieved. As an example, the OTA has been used in designing a second-order tunable VCO. Both the OT...
Article
This paper presents a high-dynamic range CMOS image sensor architecture incorporating light-controlled oscillating pixels which can act as front-end for an investigative optobionic retinal prosthesis research effort. Each pixel acts as an independent oscillator, whose frequency is proportional to the local light intensity. A 9×9 pixel array has bee...
Conference Paper
Full-text available
This paper presents an analogue VLSI circuit which implements three particular receptors of the chemical synapse: AMPA, GABA<sub>A</sub> and GABA<sub>B</sub>. The dynamics of postsynaptic receptor is implemented in CMOS current mode circuits. Furthermore with the implementation of chemical sensors in CMOS technology, the possibility of realising co...
Conference Paper
This paper presents a novel readout circuit for a pH sensitive programmable-gate ion-sensitive field effect transistor (PG-ISFET) to overcome bias issues due to threshold voltage variation and increase output-referred sensitivity. Compared to other commonly-used ISFET readouts, this circuit uses two extra programmable nodes which are driven by a fe...
Conference Paper
This paper presents a novel CMOS based PG-ISFET (programmable gate-ion sensitive field effect transistor) and readout for compensation of large threshold voltages observed with ISFETs fabricated in a standard CMOS process. The proposed device uses a capacitively coupled floating gate to allow tunability of its operating point to counteract the pres...
Conference Paper
Exploding health care demands and costs of aging and stressed populations necessitate the use of more in-home monitoring and personalized health care. Electronics hold great promise to improve the quality and reduce the cost of health care. The speakers in this hot topic session will discuss the field of health care electronics from all aspects. Fi...
Article
Recent developments have used light-activated channels or transporters to modulate neuronal activity. One such genetically-encoded modulator of activity, channelrhodopsin-2 (ChR2), depolarizes neurons in response to blue light. In this work, we first conducted electrophysiological studies of the photokinetics of hippocampal cells expressing ChR2, f...
Article
This paper presents a microcontroller-based neural interface capable of producing arbitrary current-mode wave-forms for use in developing and evaluating electrical stimulation strategies. The presented application-specific customisation focuses on charge-balanced biphasic waveforms delivered to a bipolar electrode configuration, although the hardwa...
Conference Paper
This paper introduces Chemical Bionics in which the biochemical physiology of cells in the body are implemented in VLSI to make novel bio-inspired therapeutic devices. As an example, the glucose dependant electrophysiology of the pancreatic beta cell is implemented in silicon to form a novel bio-inspired prosthetic for glucose homeostasis of Type I...
Article
Neuroprosthetics is a relatively new topic but it has already shown its potential. Since the application of this science, it has already significantly improved the quality of life of over 60,000 individuals who previously suffered from severely impaired hearing or total deafness. Today, through use of cochlear implants, children born totally deaf c...
Conference Paper
This demonstration presents the first bio-inspired approach to glucose management of type-1 diabetic patients using a real-time closed-loop insulin delivery system. The delivery system consists of a glucose biosensor, used with the silicon beta-cell to drive a motorized pump. Glucose-induced bursting of beta cells in the pancreas are used to contro...
Conference Paper
This paper presents a CMOS image sensor intended for a novel optoelectronic retinal prosthesis. Each pixel acts as an independent oscillator, whose frequency is controlled by the incident light intensity. A 9 x 9 pixel array was fabricated in AMS 0.35 mum CMOS Opto Process. Each pixel's area amounts to 25600 mum<sup>2</sup> with the array occupying...
Conference Paper
A CMOS based ion sensitive chemical imager chip is presented for real time spatio- temporal monitoring of chemical activity. Ion-sensitive field effect transistors (ISFETs) implemented on an unmodified process (AMS 0.35 um) are used as the chemical input to the analogue circuits. A 3 x 11 array has been designed and fabricated for monitoring applic...
Article
Full-text available
A novel monolithic implementation of a Wu–King profiled antenna intended for use in critical time-domain/UWB/imaging applications is presented. The simulated device was fabricated on a high-resistivity Si substrate on top of which a layer of GaAs is grown, segmented and patterned to serve as the radiating element. The device's measured return loss...
Conference Paper
Full-text available
This paper describes a novel partial-current-steering stimulation drive for implantable neural prosthetics. The drive hardware momentarily delivers a charge-balanced asymmetric stimulus to a dummy load before steering towards the stimulation electrodes. In this fashion, power is conserved whilst still gaining from the benefits of current steering....
Article
A front-end circuit for interfacing to differential capacitive sensors, including certain microelectromechanical systems, is presented. The system combines a self-resetting, biphasic integrator with a difference timer, producing a word parallel output representing the differential capacitance. The measurable capacitance range is tunable by means of...
Article
This work describes a preliminary study based on a time-frequency analysis tool, the Hilbert-Huang transform, which can be applied to the analysis of signals deemed, to some degree, nonstationary and nonlinear. Through implementation in a software programming environment and testing on a sample of patient data sets, we demonstrate the potential of...
Article
We present here a biomorphic CMOS colour opponent retinal processing algorithm and chip, representing the image-processing of the human macula lutea, with simulated and measured results. This chip has colour selective photodiodes (representing blue and red retinal cone cells) implemented without any post processing, using the intrinsic absorption o...
Chapter
The 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 mov...
Article
This paper presents the concept of a current mode readout circuit for the ion-sensitive field effect transistor (ISFET) to be used as a pH sensor. An ISFET in conjunction with a current mirror with global feedback to the source terminal yields linearity between a wide dynamic pH range and output. Operating the ISFET and current source in the weak i...
Article
Full-text available
The accurate monitoring of the physiological status of cells, tissues and whole organisms demands a new generation of devices capable of providing accurate data in real time with minimal perturbation of the system being measured. To deliver on the promise of cell-bionics advances over the past decade in miniaturization, analogue signal processing,...
Conference Paper
This paper presents a novel interface for ion-sensitive field effect transistors (ISFET) in which operation at a fixed electrical bias is achieved by voltage clamping. The chosen topology provides pH-dependent current and voltage output signals to drive an appropriate output stage. The circuit can be operated in either strong or weak inversion, dep...
Conference Paper
This paper proposes a miniaturized optoelectronic system suitable for the optical stimulation of genetically engineered retinal ganglion cells (RGCs) and focuses upon the synthesis and performance characteristics of a key circuit component needed for the programmable stimulator chip of the system: a wide tuning range voltage-controlled oscillator (...
Conference Paper
We present an adaptive, current-mode analogue neuron circuit (Boahen, 1996), which adapts its spiking output frequency and pulse width relative to the magnitude and vector of the computation of its input nodes. By modulating the pulse width to represent the output vector signed double byte data transfer protocol along a single channel is enabled: d...
Conference Paper
Full-text available
A spiking chemical sensor (SCS) is presented for detection of neurogenic ion concentration associated with active nerve fibres in nerve bundles. Based on the "integrate-and-fire" circuit, the SCS uses a chemically-modified ISFET front end encoding the sense data in the spike domain. Used in an array, it provides a spatio-temporal map of chemical ac...
Conference Paper
Full-text available
This work presents an eight channel neural stimulator interface based on an address event communication protocol. The system developed decodes, integrates and interleaves the spike patterns using a continuous interleave sampling (CIS) strategy, which drives a complex biphasic current waveform to a bipolar electrode configuration. This paper describ...
Conference Paper
Full-text available
Restoring the sensation of inertia in individuals with balance-related impairments is achievable through development of an artificial vestibular prosthesis, based on the cochlear implant paradigm. The vestibular system, however, involves added complexity in surgical methods required for reliable implantation, thus limiting widespread feasibility. T...
Conference Paper
Full-text available
This paper describes the development of a novel physiological platform aiming at the on-line, in-situ, multi-parametric, multi-channel, physicochemical, spatiotemporal monitoring of stem cell cultures. The three main operational components are: a) miniaturized electro-chemical (bio)sensors; b) real-time data acquisition system tailored to the senso...
Conference Paper
This demonstrator presents an ultra low power mixed-signal implementation of a cochlear prosthesis system. A laptop PC provides an audio stimulus to the cochlear chip. A microcontroller on the demonstrator board monitors the output channels of the chip and returns these to the PC to be displayed as a spectrogram. The audiological settings of the im...
Article
Novel biosensors, based on immobilized creatininase, creatinase and urease are developed, using ISFETs with weak inversion at pH 6–8 and 37.0 °C. The ISFETs with circuitry, demonstrate a linear relationship of urea and creatinine at the range of 0–200 and 0–20 mM, respectively. Preliminary results show that biosensors operating in weak inversion mo...
Conference Paper
Heart Variability Analysis (HRV) is not suitable for real-time processing on a resource-limited, single sensor network node, such as a Body Sensor Network (BSN) node, due to the high sampling rate (> 200H z) required to digitise ECG signals and the non-preemtable nature of operating systems such as tinyOS. Both reasons combined dictate that the pro...
Conference Paper
This paper describes the implementation of a prototype platform designed for the experimentation in the development of a non-invasive retinal prosthesis. The platform presented here is highly programmable and reconfigurable as required for experimentation. It provides retinomorphic encoding and optoelectronic stimulation. The purpose of the project...
Conference Paper
In this paper we present a biologically inspired circuit capable of implementing the membrane potential behaviour of the pancreatic beta cell. This is important as it is correlated with insulin release which is required for regulating blood glucose at a healthy level. Dysfunction of these cells is the main cause of various forms of diabetes. A nano...
Conference Paper
A hybrid vision chip is presented for real-time object-based processing for tasks such as positioning and sizing of enclosed objects. This system presents the first artificial silicon retina capable of position and size determination of multiple objects in true parallel fashion. Based on a novel distributed algorithm, this approach uses the input i...
Article
The identification of single nucleotide polymorphisms (SNP) is a subject receiving considerable attention owing to the possibility of diagnosing and screening for diseases they are connected with. Currently, the emphasis for their detection is using DNA hybridisation methods and the development of novel, mainly fluorescent based methods for hybridi...
Article
It is desirable to be able to stimulate neural cells for many different therapeutic applications. Light stimulation has many advantages over electrical stimulation if it can be achieved. Neural cells are not naturally light sensitive but they can be transformed using different strategies. Here we examine the case of genetically engineered neurons e...
Article
This paper presents the novel concept of adopting bit stream processing at the output stage of a parallel ∆−Σ FM-to-digital converter. Addition of bit streams by interleaving allows speed to be traded with circuit complexity, chip area and power consumption. The conventional implementation employing a summing tree is substituted by a simple and com...
Article
A weak inversion region is shown to exist in ion-sensitive field effect transistor (ISFET) sensors. It is therefore proposed that the ISFET and its chemically sensitive (ChemFET) counterparts be used as translinear elements in the synthesis of novel biochemical input stages which perform real-time mathematical manipulation of biochemical signals. A...
Article
This paper presents a CMOS implementation of a low-voltage micropower G<sub>m</sub>-C biquad with on-chip automatic tuning. The filter is suitable for any kind of application involving low-frequency ranges, and very low-power consumption, such as biomedical devices. The operational transconductance amplifier (OTA) is implemented with the transistor...
Article
A novel pH sensor input stage is presented using the ISFET biased in the weak inversion region so that current levels are of the order of nanoamps. Translinear current mode circuit techniques are introduced as a way of mathematically manipulating chemical/biochemical signals coded as weak inversion current. The circuit presented is an example of ap...