Wide Dynamic Range, Highly Accurate, Low Power CMOS Potentiostat for Electrochemical Sensing Applications

Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularitiesthe designed with a wide output voltage swing were implemented using TSMC 0.18-μm CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 100 pA to 60 uA

Low-Voltage Bulk-Driven Amplifier Design and Its Application in Implantable Biomedical Sensors

The powering unit usually represents a significant component of the implantable biomedical sensor system since the integrated circuits (ICs) inside for monitoring different physiological functions consume a great amount of power. One method to reduce the volume of the powering unit is to minimize the power supply voltage of the entire system. On the other hand, with the development of the deep sub-micron CMOS technologies, the minimum channel length for a single transistor has been scaled down aggressively which facilitates the reduction of the chip area as well. Unfortunately, as an inevitable part of analytic systems, analog circuits such as the potentiostat are not amenable to either low-voltage operations or short channel transistor scheme. To date, several proposed low-voltage design techniques have not been adopted by mainstream analog circuits for reasons such as insufficient transconductance, limited dynamic range, etc. Operational amplifiers (OpAmps) are the most fundamental circuit blocks among all analog circuits. They are also employed extensively inside the implantable biosensor systems. This work first aims to develop a general purpose high performance low-voltage low-power OpAmp. The proposed OpAmp adopts the bulk-driven low-voltage design technique. An innovative low-voltage bulk-driven amplifier with enhanced effective transconductance is developed in an n-well digital CMOS process operating under 1-V power supply. The proposed circuit employs auxiliary bulk-driven input differential pairs to achieve the input transconductance comparable with the traditional gate-driven amplifiers, without consuming a large amount of current. The prototype measurement results show significant improvements in the open loop gain (AO) and the unity-gain bandwidth (UGBW) compared to other works. A 1-V potentiostat circuit for an implantable electrochemical sensor is then proposed by employing this bulk-driven amplifier. To the best of the author’s knowledge, this circuit represents the first reported low-voltage potentiostat system. This 1-V potentiostat possesses high linearity which is comparable or even better than the conventional potentiostat designs thanks to this transconductance enhanced bulk-driven amplifier. The current consumption of the overall potentiostat is maintained around 22 microampere. The area for the core layout of the integrated circuit chip is 0.13 mm2 for a 0.35 micrometer process

A Low-Power, Highly Stabilized Three-Electrode Potentiostat Using Subthreshold Techniques

Implantable micro- and nano- sensors and implantable microdevices (IMDs) have demonstrated potential for monitoring various physiological parameters such as glucose, lactate, CO2 [carbon dioxide], pH, etc. Potentiostats are essential components of electrochemical sensors such as glucose monitoring devices for diabetic patients. Diabetes is a metabolic disorder associated with insufficient production or inefficient utilization of insulin. The most important role of this enzyme is to regulate the metabolic breakdown of glucose generating the necessary energy for human activities. Diabetic patients typically monitor their blood glucose levels by pricking a fingertip with a lancing device and applying the blood to a glucose meter. This painful process may need to be repeated once before each meal and once 1- 4 hour after meal. Patients may need to inject insulin manually to keep the blood glucose level at 3.9-6.7 mmol [mili mol] /liter. Frequent glucose measurement can help reduce the long term complication of this disease which includes kidney disease, nerve damage, heart and blood vessel diseases, gum disease, glaucoma and etc. Having an implanted close loop insulin delivery system can help increase the frequency of glucose measurement and the accuracy of insulin injection. The implanted close loop system consists of three main blocks: (1) an electrochemical sensor in conjunction with a potentiostat to measure the blood glucose level, (2) a control block that defines the level of insulin injection and (3) an implanted insulin pump. To provide a continuous health-care monitoring the implantable unit has to be powered up using wireless techniques. Minimizing the power consumption associated with the implantable system can improve the battery life times or minimize the power transfer through the human body. The focus of this work is on the design of low-power potentiostats for the implantable glucose monitoring system. This work addresses the conventional structures in potentiostat design and the problems associated with these designs. Based on this discussion a modification is made to improve the stability without increasing the complexity of the system. The proposed design adopts a subthreshold biasing scheme for the design of a highly-stabilized, low-power potentiostats

Biosensors

A biosensor is defined as a detecting device that combines a transducer with a biologically sensitive and selective component. When a specific target molecule interacts with the biological component, a signal is produced, at transducer level, proportional to the concentration of the substance. Therefore biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques. This book covers a wide range of aspects and issues related to biosensor technology, bringing together researchers from 11 different countries. The book consists of 16 chapters written by 53 authors. The first four chapters describe several aspects of nanotechnology applied to biosensors. The subsequent section, including three chapters, is devoted to biosensor applications in the fields of drug discovery, diagnostics and bacteria detection. The principles behind optical biosensors and some of their application are discussed in chapters from 8 to 11. The last five chapters treat of microelectronics, interfacing circuits, signal transmission, biotelemetry and algorithms applied to biosensing

Smart Embedded Systems for Biomedical Applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Low-power Wearable Healthcare Sensors

Advances in technology have produced a range of on-body sensors and smartwatches that can be used to monitor a wearer’s health with the objective to keep the user healthy. However, the real potential of such devices not only lies in monitoring but also in interactive communication with expert-system-based cloud services to offer personalized and real-time healthcare advice that will enable the user to manage their health and, over time, to reduce expensive hospital admissions. To meet this goal, the research challenges for the next generation of wearable healthcare devices include the need to offer a wide range of sensing, computing, communication, and human–computer interaction methods, all within a tiny device with limited resources and electrical power. This Special Issue presents a collection of six papers on a wide range of research developments that highlight the specific challenges in creating the next generation of low-power wearable healthcare sensors

Biocapteur ampérométrique intégré pour une unité de détection dédiée aux neurotransmetteurs

RÉSUMÉ La signalisation chimique intercellulaire façonnée par l’interaction des neurotransmetteurs joue un rôle capital dans le fonctionnement des processus cérébraux. L’analyse de l’activité neuronale chimique en temps réel dans toute sa complexité aiderait les neuroscientifiques à comprendre les mécanismes du cerveau humain et de ses pathologies neurodégénératives. Les systèmes actuellement employés dans les laboratoires de neuroscience sont limités dans leur capacité à fournir des mesures précises et adaptées aux évènements hétérogènes associées à l’activité de plusieurs neurotransmetteurs. Pour ce faire, le laboratoire de neurotechnologies Polystim envisage la conception d’un laboratoire sur puce (LSP) implantable, dédié au monitorage des substances neurochimiques circulant dans l’espace intercellulaire cérébral. Ce mémoire propose une unité de détection électrochimique associée à un tel système et conçue pour la quantification des neurotransmetteurs du liquide intercérébral. Nous proposons une architecture composée de biocapteurs utilisant un potentiostat intégré avec la technologie CMOS comme transducteur et des électrodes de mesure fonctionnalisées avec des nanotubes de carbone pour une détection sensible et sélective. Le potentiostat intégré proposé génère des mesures de temps facilement traitables numériquement qui sont proportionnelles aux courants d’oxydo-réduction produits à l’interface des électrodes de mesure. Sa configuration quantifie séparément les courants d’oxydation et de réduction à l’aide de deux canaux de mesures, selon une technique d’ampérometrie à tension constante. L’architecture est composée d’un amplificateur, d’un comparateur haute vitesse et d’un convertisseur numérique à analogique (Digital to Analog Converter - DAC). Ce dernier est partagé entre les deux canaux de sorte à réduire le temps de mesure total en fonction de l’amplitude des courants détectés. Cette topologie procure un compromis entre la plage dynamique d’entrée, la fréquence d’échantillonnage et la résolution de mesures, trois paramètres importants pour accommoder la détection et la quantification d’une grande variété de neurotransmetteurs en temps-réel. Afin de valider le prototype du potentiostat implémenté, une plateforme multi-électrodes de mesure est fabriquée et fonctionnalisée avec des films composites à base de nanotubes de carbone (Carbon Nanotubes - CNT), pour une détection sélective à la dopamine et au glutamate, deux neurotransmetteurs communs. Le circuit intégré du potentiostat est implémenté avec la technologie 0,13 µm CMOS d’IBM. Un circuit imprimé (Printed Circuit Board - PCB) comprenant un FPGA pour la gestion des signaux de contrôle et l’acquisition des données a été fabriqué pour la caractérisation expérimentale du circuit. Malgré une non-linéarité du DAC intégré fabriqué, des courants d’oxydation et de réduction d’une plage de 600 nA à 20 pA à une fréquence d’échantillonnage minimale de 1,25 kHz ont pu être mesurés expérimentalement en utilisant un DAC commercial externe. Également, le biocapteur formé du potentiostat fabriqué et de la plateforme d’électrodes fonctionnalisées est validé par des mesures biologiques en milieu in vitro concluantes pour différentes concentrations de dopamine et de glutamate en solution, en termes de sensibilité et de sélectivité des mesures ampérométriques obtenues. Ces résultats fondent la preuve de concept du biocapteur proposé comme composant de base de l’unité de détection.----------ABSTRACT Intercellular chemical signaling shaped by the interaction of neurotransmitters plays a crucial role in the functioning of brain processes. The analysis of chemical neural activity in real time in all its complexity would help neuroscientists understand the mechanisms of the human brain and its neurodegenerative diseases. Systems currently used in neuroscience laboratories are limited in their ability to provide accurate and appropriate measurements to the heterogeneous events associated with the activity of several neurotransmitters. Polystim Neurotechnologies Laboratory is therefore designing an implantable Lab on Chip (LOC) dedicated to the monitoring of neurochemicals circulating in the brain's intercellular space that provides the needed features. This thesis presents an electrochemical detection unit associated with such system, designed for the quantification of neurotransmitters in the intracerebral liquid. We propose an architecture composed of biosensors using a potentiostat integrated with CMOS technology as transducer, and measuring electrodes with functionalized carbon nanotubes for sensitive and selective measurements. The proposed integrated potentiostat generates time measurements easily treatable digitally, which are proportional to redox currents produced at the interface of the measuring electrodes. Its configuration separately quantizes oxidation and reduction currents by using two measuring channels, according to a constant voltage amperometry technique. The architecture consists of an amplifier, a high-speed comparator and a digital-to-analog converter (DAC). The latter is shared between the two channels in order to reduce the total measurement time as a function of the detected currents amplitude. This topology provides a compromise between the input dynamic range, sampling frequency and resolution measurements, three important parameters to accommodate the detection and quantification of a wide variety of neurotransmitters in real time. To validate the prototype of the implemented potentiostat, a multi-electrode measuring platform is fabricated and functionalized with composite films based on carbon nanotubes (CNTs), for dopamine and glutamate, two common neurotransmitters, selective detection. The potentiostat integrated circuit is implemented with IBM 0.13 µm CMOS technology. A printed circuit board (PCB) containing an FPGA managing control signals and data acquisition, was made to experimentally characterize the fabricated circuit. Despite the non-linearity of the manufactured integrated DAC, oxidation and reduction currents ranging from 600 nA to 20 pA at a minimum sampling frequency of 1.25 kHz could be measured experimentally using an external commercial DAC. Also, the biosensor formed by the potentiostat and the functionalized electrodes platform is validated by conclusive in vitro biological measurements of dopamine and glutamate in solutions, in terms of sensitivity and selectivity. These results forms the proof of concept of the proposed biosensor as the base component of the detection unit