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This work presents a high-voltage, high-precision bi-directional multi-channel system capable of stimulating neural activity through bi-phasic pulses of amplitude up to ∓50 V while recording very low-voltage responses as low as tens of microvolts. Most of the systems reported from the scientific community possess at least one of the following common limitations: low stimulation voltages, low gain capabilities, or insufficient bandwidth to acquire a wide range of different neural activities. While systems can be found that present remarkable capabilities in one or more specific areas, a versatile system that performs over all these aspects is missing. Moreover, as many novel materials, like silicon carbide, are emerging as biocompatible interfaces, and more specifically as neuronal interfaces, it becomes mandatory to have a system operating across a wide range of voltages and frequencies for both physiological and electrical compatibility testing. The system designed and proven during this doctoral research effort features a ∓50 V bi-phasic pulse generator, 62 to 100 dB of software selectable amplification, and a wide 18 Hz to 12 kHz bandwidth. In addition to design and realization we report about biological testing consisting in the acquisition of neural signals from tissue cultures using an MEA where faithful signal recording was achieved with superior fidelity to a commercial system used to sample signals from the same culture. The only system parameter that was less robust than the commercial system was the noise level, which due to our higher bandwidth was somewhat expected. More importantly our custom electronics outperformed in terms of lower delay and lower cost of realization. All of these results plus suggested future works are listed for the reader's convenience.

abstract: The recording of biosignals enables physicians to correctly diagnose diseases and prescribe treatment. Existing wireless systems failed to effectively replace the conventional wired methods due to their large sizes, high power consumption, and the need to replace batteries. This thesis aims to alleviate these issues by presenting a series of wireless fully-passive sensors for the acquisition of biosignals: including neuropotential, biopotential, intracranial pressure (ICP), in addition to a stimulator for the pacing of engineered cardiac cells. In contrast to existing wireless biosignal recording systems, the proposed wireless sensors do not contain batteries or high-power electronics such as amplifiers or digital circuitries. Instead, the RFID tag-like sensors utilize a unique radiofrequency (RF) backscattering mechanism to enable wireless and battery-free telemetry of biosignals with extremely low power consumption. This characteristic minimizes the risk of heat-induced tissue damage and avoids the need to use any transcranial/transcutaneous wires, and thus significantly enhances long-term safety and reliability. For neuropotential recording, a small (9mm x 8mm), biocompatible, and flexible wireless recorder is developed and verified by in vivo acquisition of two types of neural signals, the somatosensory evoked potential (SSEP) and interictal epileptic discharges (IEDs). For wireless multichannel neural recording, a novel time-multiplexed multichannel recording method based on an inductor-capacitor delay circuit is presented and tested, realizing simultaneous wireless recording from 11 channels in a completely passive manner. For biopotential recording, a wearable and flexible wireless sensor is developed, achieving real-time wireless acquisition of ECG, EMG, and EOG signals. For ICP monitoring, a very small (5mm x 4mm) wireless ICP sensor is designed and verified both in vitro through a benchtop setup and in vivo through real-time ICP recording in rats. Finally, for cardiac cell stimulation, a flexible wireless passive stimulator, capable of delivering stimulation current as high as 60 mA, is developed, demonstrating successful control over the contraction of engineered cardiac cells. The studies conducted in this thesis provide information and guidance for future translation of wireless fully-passive telemetry methods into actual clinical application, especially in the field of implantable and wearable electronics. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

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La maladie de Parkinson est la seconde maladie neuro-dégénérative la plus fréquente à travers le monde. Dans ce contexte, le projet de recherche associé à cette thèse vise à améliorer le traitement symptomatique de la maladie de Parkinson, par le développement de procédés de stimulation cérébrale profonde adaptative. Le travail de cette thèse repose sur la conception d’un ASIC d’enregistrement et de traitement de signaux neuronaux, répondant à divers enjeux :un traitement continu et en temps réel focalisé sur des bandes spécifiques très basses-fréquences et largement configurables. L’objectif est d’utiliser l’information traitée pour le contrôle et la génération d’un signal de stimulation. Cet ASIC a été développé, caractérisé électroniquement et utilisé dans un contexte in vivo. Un système en boucle fermée a été réalisé à partir de cet ASIC, se montrant fonctionnel. Ces validations expérimentales in vivo ouvrent de nombreuses possibilités d’investigation du concept de stimulation cérébrale en boucle fermée. / Parkinson’s disease is the second most common neurodegenerative diseases throughout theworld. In this context, the research project associated with this thesis is to improve the symptomatictreatment of Parkinson’s disease through the development process of deep brain stimulationadaptive. The work of this thesis is based on the design of an ASIC for recording andprocessing of neural signals, in response to a variety of issues : ongoing treatment and real-timefocus on specific bands of very low-frequency and highly configurable. The goal is to use theprocessed information to the control and generation of a stimulation signal. This ASIC wasdeveloped, characterized and used electronically in a context in vivo. A closed-loop system wasmade from the ASIC, showing functional. These in vivo validations open up many possibilitiesfor investigation of the concept of closed-loop brain stimulation.

abstract: The ability to monitor electrophysiological signals from the sentient brain is requisite to decipher its enormously complex workings and initiate remedial solutions for the vast amount of neurologically-based disorders. Despite immense advancements in creating a variety of instruments to record signals from the brain, the translation of such neurorecording instrumentation to real clinical domains places heavy demands on their safety and reliability, both of which are not entirely portrayed by presently existing implantable recording solutions. In an attempt to lower these barriers, alternative wireless radar backscattering techniques are proposed to render the technical burdens of the implant chip to entirely passive neurorecording processes that transpire in the absence of formal integrated power sources or powering schemes along with any active circuitry. These radar-like wireless backscattering mechanisms are used to conceive of fully passive neurorecording operations of an implantable microsystem. The fully passive device potentially manifests inherent advantages over current wireless implantable and wired recording systems: negligible heat dissipation to reduce risks of brain tissue damage and minimal circuitry for long term reliability as a chronic implant. Fully passive neurorecording operations are realized via intrinsic nonlinear mixing properties of the varactor diode. These mixing and recording operations are directly activated by wirelessly interrogating the fully passive device with a microwave carrier signal. This fundamental carrier signal, acquired by the implant antenna, mixes through the varactor diode along with the internal targeted neuropotential brain signals to produce higher frequency harmonics containing the targeted neuropotential signals. These harmonics are backscattered wirelessly to the external interrogator that retrieves and recovers the original neuropotential brain signal. The passive approach removes the need for internal power sources and may alleviate heat trauma and reliability issues that limit practical implementation of existing implantable neurorecorders. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2014

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