An external control unit implemented for stimulator ASIC testing

This paper presents the design and development of an external control unit (ECU) for a stimulator ASIC testing purposes. The ECU consists of a graphical user interface (GUI) from the PC, a data transceiver and a power transmitter. The GUI was developed using MATLAB for stimulation data setup. The data transceiver was designed using hardware description language (HDL) Verilog code and was implemented in a Virtex-II Pro FPGA board. The overall stimulator ASIC design architecture and its operation for an epiretinal implant application are briefly explained to correlate with the ECU’s design requirements. The flexible multichannel stimulator ASIC was successfully fabricated in a 0.35μm AMS HVCMOS technology. Conducted simulation and measurement results on stimulation waveform generation, supply voltage compliance and external control of supply voltage adaptation validate the functionality of the designed ECU and the stimulator ASIC.Keywords: external control unit; data transceiver; stimulator ASIC; retinal prosthesis; epiretinal implant; stimulation waveform; Manchester data; voltage compliance

Recent Advances in Neural Recording Microsystems

The accelerating pace of research in neuroscience has created a considerable demand for neural interfacing microsystems capable of monitoring the activity of large groups of neurons. These emerging tools have revealed a tremendous potential for the advancement of knowledge in brain research and for the development of useful clinical applications. They can extract the relevant control signals directly from the brain enabling individuals with severe disabilities to communicate their intentions to other devices, like computers or various prostheses. Such microsystems are self-contained devices composed of a neural probe attached with an integrated circuit for extracting neural signals from multiple channels, and transferring the data outside the body. The greatest challenge facing development of such emerging devices into viable clinical systems involves addressing their small form factor and low-power consumption constraints, while providing superior resolution. In this paper, we survey the recent progress in the design and the implementation of multi-channel neural recording Microsystems, with particular emphasis on the design of recording and telemetry electronics. An overview of the numerous neural signal modalities is given and the existing microsystem topologies are covered. We present energy-efficient sensory circuits to retrieve weak signals from neural probes and we compare them. We cover data management and smart power scheduling approaches, and we review advances in low-power telemetry. Finally, we conclude by summarizing the remaining challenges and by highlighting the emerging trends in the field

Wireless Power Transfer Techniques for Implantable Medical Devices:A Review

Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD

Design of Integrated Neural/Modular Stimulators

Ph.DDOCTOR OF PHILOSOPH

Neurostimulator with Waveforms Inspired by Nature for Wearable Electro-Acupuncture

The work presented here has 3 goals: establish the need for novel neurostimulation waveform solutions through a literature review, develop a neurostimulation pulse generator, and verify the operation of the device for neurostimulation applications. The literature review discusses the importance of stimulation waveforms on the outcomes of neurostimulation, and proposes new directions for neurostimulation research that would help in improving the reproducibility and comparability between studies. The pulse generator circuit is then described that generates signals inspired by the shape of excitatory or inhibitory post-synaptic potentials (EPSP, IPSP). The circuit analytical equations are presented, and the effects of the circuit design components are discussed. The circuit is also analyzed with a capacitive load using a simplified Randles model to represent the electrode-electrolyte interface, and the output is measured in phosphate-buffered saline (PBS) solution as the load with acupuncture needles as electrodes. The circuit is designed to be used in different types of neurostimulators depending on the needs of the application, and to study the effects of varying neurostimulation waveforms. The circuit is used to develop a remote-controlled wearable veterinary electro-acupuncture machine. The device has a small form-factor and 3D printed enclosure, and has a weight of 75 g with leads attached. The device is powered by a 500 mAh lithium polymer battery, and was tested to last 6 hours. The device is tested in an electro-acupuncture animal study on cats performed at the Louisiana State University School of Veterinary Medicine, where it showed expected electro-acupuncture effects. Then, a 2-channel implementation of the device is presented, and tested to show independent output amplitude, frequency, and stimulation duration per channel. Finally, the software and hardware requirements for control of the wearable veterinary electro-acupuncture machine are detailed. The number of output channels is limited to the number of hardware PWM timers available for use. The Arduino software implements PWM control for the output amplitude and frequency. The stimulation duration control is provided using software timers. The communications protocol between the microcontroller board and Android App are described, and communications are performed via Bluetooth

Neuromorphic hardware for somatosensory neuroprostheses

In individuals with sensory-motor impairments, missing limb functions can be restored using neuroprosthetic devices that directly interface with the nervous system. However, restoring the natural tactile experience through electrical neural stimulation requires complex encoding strategies. Indeed, they are presently limited in effectively conveying or restoring tactile sensations by bandwidth constraints. Neuromorphic technology, which mimics the natural behavior of neurons and synapses, holds promise for replicating the encoding of natural touch, potentially informing neurostimulation design. In this perspective, we propose that incorporating neuromorphic technologies into neuroprostheses could be an effective approach for developing more natural human-machine interfaces, potentially leading to advancements in device performance, acceptability, and embeddability. We also highlight ongoing challenges and the required actions to facilitate the future integration of these advanced technologies

A Wireless, High-Voltage Compliant, and Energy-Efficient Visual Intracortical Microstimulator

RÉSUMÉ L’objectif général de ce projet de recherche est la conception, la mise en oeuvre et la validation d’une interface sans fil intracorticale implantable en technologie CMOS avancée pour aider les personnes ayant une déficience visuelle. Les défis majeurs de cette recherche sont de répondre à la conformité à haute tension nécessaire à travers l’interface d’électrode-tissu (IET), augmenter la flexibilité dans la microstimulation et la surveillance multicanale, minimiser le budget de puissance pour un dispositif biomédical implantable, réduire la taille de l’implant et améliorer le taux de transmission sans fil des données. Par conséquent, nous présentons dans cette thèse un système de microstimulation intracorticale multi-puce basée sur une nouvelle architecture pour la transmission des données sans fil et le transfert de l’énergie se servant de couplages inductifs et capacitifs. Une première puce, un générateur de stimuli (SG) éconergétique, et une autre qui est un amplificateur de haute impédance se connectant au réseau de microélectrodes de l’étage de sortie. Les 4 canaux de générateurs de stimuli produisent des impulsions rectangulaires, demi-sinus (DS), plateau-sinus (PS) et autres types d’impulsions de courant à haut rendement énergétique. Le SG comporte un contrôleur de faible puissance, des convertisseurs numérique-analogiques (DAC) opérant en mode courant, générateurs multi-forme d’ondes et miroirs de courants alimentés sous 1.2 et 3.3V se servant pour l’interface entre les deux technologies utilisées. Le courant de stimulation du SG varie entre 2.32 et 220μA pour chaque canal. La deuxième puce (pilote de microélectrodes (MED)), une interface entre le SG et de l’arrangement de microélectrodes (MEA), fournit quatre niveaux différents de courant avec la valeur maximale de 400μA par entrée et 100μA par canal de sortie simultanément pour 8 à 16 sites de stimulation à travers les microélectrodes, connectés soit en configuration bipolaire ou monopolaire. Cette étage de sortie est hautement configurable et capable de délivrer une tension élevée pour satisfaire les conditions de l’interface à travers l’impédance de IET par rapport aux systèmes précédemment rapportés. Les valeurs nominales de plus grandes tensions d’alimentation sont de ±10V. La sortie de tension mesurée est conformément 10V/phase (anodique ou cathodique) pour les tensions d’alimentation spécifiées. L’incrémentation de tensions d’alimentation à ±13V permet de produire un courant de stimulation de 220μA par canal de sortie permettant d’élever la tension de sortie jusqu’au 20V par phase. Cet étage de sortie regroupe un commutateur haute tension pour interfacer une matrice des miroirs de courant (3.3V /20V), un registre à décalage de 32-bits à entrée sérielle, sortie parallèle, et un circuit dédié pour bloquer des états interdits.----------ABSTRACT The general objective of this research project is the design, implementation and validation of an implantable wireless intracortical interface in advanced CMOS technology to aid the visually impaired people. The major challenges in this research are to meet the required highvoltage compliance across electrode-tissue interface (ETI), increase lexibility in multichannel microstimulation and monitoring, minimize power budget for an implantable biomedical device, reduce the implant size, and enhance the data rate in wireless transmission. Therefore, we present in this thesis a multi-chip intracortical microstimulation system based on a novel architecture for wireless data and power transmission comprising inductive and capacitive couplings. The first chip is an energy-efficient stimuli generator (SG) and the second one is a highimpedance microelectrode array driver output-stage. The 4-channel stimuli-generator produces rectangular, half-sine (HS), plateau-sine (PS), and other types of energy-efficient current pulse. The SG is featured with low-power controller, current mode source- and sinkdigital- to-analog converters (DACs), multi-waveform generators, and 1.2V/3.3V interface current mirrors. The stimulation current per channel of the SG ranges from 2.32 to 220μA per channel. The second chip (microelectrode driver (MED)), an interface between the SG and the microelectrode array (MEA), supplies four different current levels with the maximum value of 400μA per input and 100μA per output channel. These currents can be delivered simultaneously to 8 to 16 stimulation sites through microelectrodes, connected either in bipolar or monopolar configuration. This output stage is highly-configurable and able to deliver higher compliance voltage across ETI impedance compared to previously reported designs. The nominal values of largest supply voltages are ±10V. The measured output compliance voltage is 10V/phase (anodic or cathodic) for the specified supply voltages. Increment of supply voltages to ±13V allows 220μA stimulation current per output channel enhancing the output compliance voltage up to 20V per phase. This output-stage is featured with a high-voltage switch-matrix, 3.3V/20V current mirrors, an on-chip 32-bit serial-in parallel-out shift register, and the forbidden state logic building blocks. The SG and MED chips have been designed and fabricated in IBM 0.13μm CMOS and Teledyne DALSA 0.8μm 5V/20V CMOS/DMOS technologies with silicon areas occupied by them 1.75 x 1.75mm2 and 4 x 4mm2 respectively. The measured DC power budgets consumed by low-and mid-voltage microchips are 2.56 and 2.1mW consecutively

Integrated Circuits and Systems for Smart Sensory Applications

Connected intelligent sensing reshapes our society by empowering people with increasing new ways of mutual interactions. As integration technologies keep their scaling roadmap, the horizon of sensory applications is rapidly widening, thanks to myriad light-weight low-power or, in same cases even self-powered, smart devices with high-connectivity capabilities. CMOS integrated circuits technology is the best candidate to supply the required smartness and to pioneer these emerging sensory systems. As a result, new challenges are arising around the design of these integrated circuits and systems for sensory applications in terms of low-power edge computing, power management strategies, low-range wireless communications, integration with sensing devices. In this Special Issue recent advances in application-specific integrated circuits (ASIC) and systems for smart sensory applications in the following five emerging topics: (I) dedicated short-range communications transceivers; (II) digital smart sensors, (III) implantable neural interfaces, (IV) Power Management Strategies in wireless sensor nodes and (V) neuromorphic hardware

Remote Powering and Data Communication Over a Single Inductive Link for Implantable Medical Devices

RÉSUMÉ Les implants médicaux électroniques (Implantable Medical Devices - IMDs) sont notamment utilisés pour restaurer ou améliorer des fonctions perdues de certains organes. Ils sont capables de traiter des complications qui ne peuvent pas être guéries avec des médicaments ou par la chirurgie. Offrant des propriétés et des améliorations curatives sans précédent, les IMDs sont de plus en plus demandés par les médecins et les patients. En 2017, le marché mondial des IMD était évalué à 15,21 milliards de dollars. D’ici 2025, il devrait atteindre 30,42 mil-liards de dollars, soutenu par un taux de croissance annuel de 9,24% selon le nouveau rapport publié par Fior Markets. Cette expansion entraîne une augmentation des exigences pour as-surer des performances supérieures, des fonctionnalités supplémentaires et une durée de vie plus longue. Ces exigences ne peuvent être satisfaites qu’avec des techniques d’alimentation avancées, un débit de données élevé et une électronique miniaturisée robuste. Construire des systèmes capables de fournir toutes ces caractéristiques est l’objectif principal d’un grand nombre de chercheurs. Parmi plusieurs technologies sans fil, le lien inductif, qui consiste en une paire de bobines à couplage magnétique, est la technique sans fil la plus largement utilisée pour le transfert de puissance et de données. Cela est dû à sa simplicité, sa sécurité et sa capacité à transmettre à la fois de la puissance et des données de façon bidirectionnelle. Cependant, il existe encore un certain nombre de défis concernant la mise en œuvre d’un tel système de transfert d’énergie et de données sans fil (Wireless Power and Data Transfer - WPDT system). Un défi majeur est que les exigences pour une efficacité de transfert d’énergie élevée et pour une communication à haut débit sont contradictoires. En fait, la bande passante doit être élargie pour des débits de données élevés, mais réduite pour une transmission efficace de l’énergie. Un autre grand défi consiste à réaliser un démodulateur fonctionnant à haute vitesse avec une mise en œuvre simple et une consommation d’énergie ultra-faible. Dans ce projet, nous proposons et expérimentons un nouveau système WPDT dédié aux IMD permettant une communication à haute vitesse et une alimentation efficace tout en maintenant une faible consommation d’énergie, une petite surface de silicium et une mise en œuvre simple du récepteur. Le système proposé est basé sur un nouveau schéma de modulation appelé "Carrier Width Modulation (CWM)", ainsi que sur des circuits de modulation et de démodulation inédits. La modulation consiste en un coupe-circuit synchronisé du réservoir LC primaire pendant un ou deux cycles en fonction des données transmises.----------ABSTRACT Implantable Medical Devices (IMDs) are electronic implants notably used to restore or en-hance lost organ functions. They may treat complications that cannot be cured with medica-tion or through surgery. O˙ering unprecedented healing properties and enhancements, IMDs are increasingly requested by physicians and patients. In 2017, the worldwide IMD market was valued at USD 15,21 Billion. By 2025, it is expected to attain USD 30.42 Billion sus-tained by a compound annual growth rate of 9.24% according to a recent report published by Fior Markets. This expansion is bringing-up more demand for higher performance, additional features, and longer device lifespan and autonomy. These requirements can only be achieved with advanced power sources, high-data rates, and robust miniaturized electronics. Building systems able to provide all these characteristics is the main goal of many researchers. Among several wireless technologies, the inductive link, which consists of a magnetically-coupled pair of coils, is the most widely used wireless technique for both power and data transfer. This is due to its simplicity, safety, and ability to provide simultaneously both power and bidirectional data transfer to the implant. However there are still a number of challenges regarding the implementation of such Wireless Power and Data Transfer (WPDT) systems. One main challenge is that the requirements for high Power Transfer Eÿciency (PTE) and for high-data rate communication are contra-dictory. In fact, the bandwidth needs to be widened for high data rates, but narrowed for eÿcient power delivery. Another big challenge is to implement a high-speed demodulator with simple implementation and ultra-low power consumption. In this project, we propose and experiment a new WPDT system dedicated to IMDs allow-ing high-speed communication and eÿcient power delivery, while maintaining a low power consumption, small silicon area, and simple implementation of the receiver. The proposed system is based on a new Carrier Width Modulation (CWM) scheme, as well as novel modu-lation and demodulation circuits. The modulation consists of a synchronized opening of the primary LC tank for one or two cycles according to the transmitted data. Unlike conventional modulation techniques, the data rate of the proposed CWM modulation is not limited by the quality factors of the primary and secondary coils. On the other hand, the proposed CWM demodulator allows higher-speed demodulation and simple implementation, unlike conven-tional demodulators for a similar modulation scheme. It also o˙ers a wide range of data rates under any selected frequency from 10 to 31 MHz

Wireless power and data transmission to high-performance implantable medical devices

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.Ph.D