31 research outputs found

    High-performance wireless power and data transfer interface for implantable medical devices

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    D’importants progĂšs ont Ă©tĂ© rĂ©alisĂ©s dans le dĂ©veloppement des systĂšmes biomĂ©dicaux implantables grĂące aux derniĂšres avancĂ©es de la microĂ©lectronique et des technologies sans fil. NĂ©anmoins, ces appareils restent difficiles Ă  commercialier. Cette situation est due particuliĂšrement Ă  un manque de stratĂ©gies de design capable supporter les fonctionnalitĂ©s exigĂ©es, aux limites de miniaturisation, ainsi qu’au manque d’interface sans fil Ă  haut dĂ©bit fiable et faible puissance capable de connecter les implants et les pĂ©riphĂ©riques externes. Le nombre de sites de stimulation et/ou d’électrodes d’enregistrement retrouvĂ©s dans les derniĂšres interfaces cerveau-ordinateur (IMC) ne cesse de croĂźtre afin d’augmenter la prĂ©cision de contrĂŽle, et d’amĂ©liorer notre comprĂ©hension des fonctions cĂ©rĂ©brales. Ce nombre est appelĂ© Ă  atteindre un millier de site Ă  court terme, ce qui exige des dĂ©bits de donnĂ©es atteingnant facilement les 500 Mbps. Ceci Ă©tant dit, ces travaux visent Ă  Ă©laborer de nouvelles stratĂ©gies innovantes de conception de dispositifs biomĂ©dicaux implantables afin de repousser les limites mentionnĂ©es ci-dessus. On prĂ©sente de nouvelles techniques faible puissance beaucoup plus performantes pour le transfert d’énergie et de donnĂ©es sans fil Ă  haut dĂ©bit ainsi que l’analyse et la rĂ©alisation de ces derniĂšres grĂące Ă  des prototypes microĂ©lectroniques CMOS. Dans un premier temps, ces travaux exposent notre nouvelle structure multibobine inductive Ă  rĂ©sonance prĂ©sentant une puissance sans fil distribuĂ©e uniformĂ©ment pour alimenter des systĂšmes miniatures d’étude du cerveaux avec des models animaux en ilbertĂ© ainsi que des dispositifs mĂ©dicaux implantbles sans fil qui se caractĂ©risent par une capacitĂ© de positionnement libre. La structure propose un lien de rĂ©sonance multibobines inductive, dont le rĂ©sonateur principal est constituĂ© d’une multitude de rĂ©sonateurs identiques disposĂ©s dans une matrice de bobines carrĂ©es. Ces derniĂšres sont connectĂ©es en parallĂšle afin de rĂ©aliser des surfaces de puissance (2D) ainsi qu’une chambre d’alimentation (3D). La chambre proposĂ©e utilise deux matrices de rĂ©sonateurs de base, mises face Ă  face et connectĂ©s en parallĂšle afin d’obtenir une distribution d’énergie uniforme en 3D. Chaque surface comprend neuf bobines superposĂ©es, connectĂ©es en parallĂšle et rĂ©ailsĂ©es sur une carte de circuit imprimĂ© deux couches FR4. La chambre dispose d’un mĂ©canisme naturel de localisation de puissance qui facilite sa mise en oeuvre et son fonctionnement. En procĂ©dant ainsi, nous Ă©vitons la nĂ©cessitĂ© d’une dĂ©tection active de l’emplacement de la charge et le contrĂŽle d’alimentation. Notre approche permet Ă  cette surface d’alimentation unique de fournir une efficacitĂ© de transfert de puissance (PTE) de 69% et une puissance dĂ©livrĂ©e Ă  la charge (PDL) de 120 mW, pour une distance de sĂ©paration de 4 cm, tandis que le prototype de chambre complet fournit un PTE uniforme de 59% et un PDL de 100 mW en 3D, partout Ă  l’intĂ©rieur de la chambre avec un volume de chambre de 27 × 27 × 16 cm3. Une Ă©tape critique avant d’utiliser un dispositif implantable chez les humains consiste Ă  vĂ©rifier ses fonctionnalitĂ©s sur des sujets animaux. Par consĂ©quent, la chambre d’énergie sans fil conçue sera utilisĂ©e afin de caractĂ©riser les performances d’ une interface sans fil de transmisison de donnĂ©es dans un environnement rĂ©aliste in vivo avec positionement libre. Un Ă©metteur-rĂ©cepteur full-duplex (FDT) entiĂšrement intĂ©grĂ© qui se caractĂ©rise par sa faible puissance est conçu pour rĂ©aliser une interfaces bi-directionnelles (stimulation et enregistrement) avec des dĂ©bits asymĂ©triques: des taux de tramnsmission plus Ă©levĂ©s sont nĂ©cessaires pour l’enregistrement Ă©lectrophysiologique multicanal (signaux de liaison montante) alors que les taux moins Ă©levĂ©s sont utilisĂ©s pour la stimulation (les signaux de liaison descendante). L’émetteur (TX) et le rĂ©cepteur (RX) se partagent une seule antenne afin de rĂ©duire la taille de l’implant. L’émetteur utilise la radio ultra-large bande par impulsions (IR-UWB) basĂ©e sur l’approche edge combining et le RX utilise la bande ISM (Industrielle, Scientifique et MĂ©dicale) de frĂ©quence central 2.4 GHz et la modulation on-off-keying (OOK). Une bonne isolation (> 20 dB) est obtenue entre le TX et le RX grĂące Ă  1) la mise en forme les impulsions Ă©mises dans le spectre UWB non rĂ©glementĂ©e (3.1-7 GHz), et 2) le filtrage espace-efficace (Ă©vitant l’utilisation d’un circulateur ou d’un diplexeur) du spectre du lien de communication descendant directement au niveau de l’ amplificateur Ă  faible bruit (LNA). L’émetteur UWB 3.1-7 GHz utilise un e modultion OOK ainsi qu’une modulation par dĂ©placement de phase (BPSK) Ă  seulement 10.8 pJ / bits. Le FDT proposĂ© permet d’atteindre 500 Mbps de dĂ©bit de donnĂ©es en lien montant et 100 Mbps de dĂ©bit de donnĂ©es de lien descendant. Il est entiĂšrement intĂ©grĂ© dans un procĂ©dĂ© TSMC CMOS 0.18 um standard et possĂšde une taille totale de 0.8 mm2. La consommation totale d’énergie mesurĂ©e est de 10.4 mW (5 mW pour RX et 5.4 mW pour TX au taux de 500 Mbps).In recent years, there has been major progress on implantable biomedical systems that support most of the functionalities of wireless implantable devices. Nevertheless, these devices remain mostly restricted to be commercialized, in part due to weakness of a straightforward design to support the required functionalities, limitation on miniaturization, and lack of a reliable low-power high data rate interface between implants and external devices. This research provides novel strategies on the design of implantable biomedical devices that addresses these limitations by presenting analysis and techniques for wireless power transfer and efficient data transfer. The first part of this research includes our proposed novel resonance-based multicoil inductive power link structure with uniform power distribution to wirelessly power up smart animal research systems and implanted medical devices with high power efficiency and free positioning capability. The proposed structure consists of a multicoil resonance inductive link, which primary resonator array is made of several identical resonators enclosed in a scalable array of overlapping square coils that are connected in parallel and arranged in power surface (2D) and power chamber (3D) configurations. The proposed chamber uses two arrays of primary resonators, facing each other, and connected in parallel to achieve uniform power distribution in 3D. Each surface includes 9 overlapped coils connected in parallel and implemented into two layers of FR4 printed circuit board. The chamber features a natural power localization mechanism, which simplifies its implementation and eases its operation by avoiding the need for active detection of the load location and power control mechanisms. A single power surface based on the proposed approach can provide a power transfer efficiency (PTE) of 69% and a power delivered to the load (PDL) of 120 mW, for a separation distance of 4 cm, whereas the complete chamber prototype provides a uniform PTE of 59% and a PDL of 100 mW in 3D, everywhere inside the chamber with a chamber size of 27×27×16 cm3. The second part of this research includes our proposed novel, fully-integrated, low-power fullduplex transceiver (FDT) to support bi-directional neural interfacing applications (stimulating and recording) with asymmetric data rates: higher rates are required for recording (uplink signals) than stimulation (downlink signals). The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by space-efficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier (LNA). The UWB 3.1-7 GHz transmitter using OOK and binary phase shift keying (BPSK) modulations at only 10.8 pJ/bit. The proposed FDT provides dual band 500 Mbps TX uplink data rate and 100 Mbps RX downlink data rate. It is fully integrated on standard TSMC 0.18 nm CMOS within a total size of 0.8 mm2. The total power consumption measured 10.4 mW (5 mW for RX and 5.4 mW for TX at the rate of 500 Mbps)

    Wireless power transfer for combined sensing and stimulation in implantable biomedical devices

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    Actuellement, il existe une forte demande de Headstage et de microsystĂšmes intĂ©grĂ©s implantables pour Ă©tudier l’activitĂ© cĂ©rĂ©brale de souris de laboratoire en mouvement libre. De tels dispositifs peuvent s’interfacer avec le systĂšme nerveux central dans les paradigmes Ă©lectriques et optiques pour stimuler et surveiller les circuits neuronaux, ce qui est essentiel pour dĂ©couvrir de nouveaux mĂ©dicaments et thĂ©rapies contre des troubles neurologiques comme l’épilepsie, la dĂ©pression et la maladie de Parkinson. Puisque les systĂšmes implantables ne peuvent pas utiliser une batterie ayant une grande capacitĂ© en tant que source d’énergie primaire dans des expĂ©riences Ă  long terme, la consommation d’énergie du dispositif implantable est l’un des principaux dĂ©fis de ces conceptions. La premiĂšre partie de cette recherche comprend notre proposition de la solution pour diminuer la consommation d’énergie des microcircuits implantables. Nous proposons un nouveau circuit de dĂ©calage de niveau qui convertit les niveaux de signaux sub-seuils en niveaux ultra-bas Ă  haute vitesse en utilisant une trĂšs faible puissance et une petite zone de silicium, ce qui le rend idĂ©al pour les applications de faible puissance. Le circuit proposĂ© introduit une nouvelle topologie de dĂ©caleur de niveau de tension utilisant un condensateur de dĂ©calage de niveau pour augmenter la plage de tensions de conversion, tout en rĂ©duisant considĂ©rablement le retard de conversion. Le circuit proposĂ© atteint un dĂ©lai de propagation plus court et une zone de silicium plus petite pour une frĂ©quence de fonctionnement et une consommation d’énergie donnĂ©e par rapport Ă  d’autres solutions de circuit. Les rĂ©sultats de mesure sont prĂ©sentĂ©s pour le circuit proposĂ© fabriquĂ© dans un processus CMOS TSMC de 0,18- mm. Le circuit prĂ©sentĂ© peut convertir une large gamme de tensions d’entrĂ©e de 330 mV Ă  1,8 V et fonctionner sur une plage de frĂ©quence de 100 Hz Ă  100 MHz. Il a un dĂ©lai de propagation de 29 ns et une consommation d’énergie de 61,5 nW pour les signaux d’entrĂ©e de 0,4 V, Ă  une frĂ©quence de 500 kHz, surpassant les conceptions prĂ©cĂ©dentes. La deuxiĂšme partie de cette recherche comprend nos systĂšmes de transfert d’énergie sans fil proposĂ© pour les applications optogĂ©nĂ©tiques. L’optogĂ©nĂ©tique est la combinaison de la mĂ©thode gĂ©nĂ©tique et optique d’excitation, d’enregistrement et de contrĂŽle des neurones biologiques. Ce systĂšme combine plusieurs technologies telles que les MEMS et la microĂ©lectronique pour collecter et transmettre les signaux neuronaux et activer un stimulateur optique via une liaison sans fil. Puisque les stimulateurs optiques consomment plus de puissance que les stimulateurs Ă©lectriques, l’interface utilise la transmission de puissance par induction en utilisant des moyens innovants au lieu de la batterie avec la petite capacitĂ© comme source d’énergie.Notre premiĂšre contribution dans la deuxiĂšme partie fournit un systĂšme de cage domestique intelligent basĂ© sur des barrettes multi-bobines superposĂ©es Ă  travers un rĂ©cepteur multicellulaire implantable mince de taille 1×1 cm2, implantĂ© sous le cuir chevelu d’une souris de laboratoire, et unitĂ© de gestion de l’alimentation intĂ©grĂ©e. Ce systĂšme inductif est conçu pour fournir jusqu’à 35,5 mW de puissance dĂ©livrĂ©e Ă  un Ă©metteur-rĂ©cepteur full duplex de faible puissance entiĂšrement intĂ©grĂ© pour prendre en charge des implants neuronaux Ă  haute densitĂ© et bidirectionnels. L’émetteur (TX) utilise une bande ultra-large Ă  impulsions radio basĂ©e sur des approches de combinaison, et le rĂ©cepteur (RX) utilise une topologie Ă  bande Ă©troite Ă  incrĂ©mentation de 2,4 GHz. L’émetteur-rĂ©cepteur proposĂ© fournit un dĂ©bit de donnĂ©es de liaison montante TX Ă  500 Mbits/s double et un dĂ©bit de donnĂ©es de liaison descendante RX Ă  100 Mbits/s, et est entiĂšrement intĂ©grĂ© dans un processus CMOS TSMC de 0,18-mm d’une taille totale de 0,8 mm2 . La puissance peut ĂȘtre dĂ©livrĂ©e Ă  partir d’un signal de porteuse de 13,56-MHz avec une efficacitĂ© globale de transfert de puissance supĂ©rieure Ă  5% sur une distance de sĂ©paration allant de 3 cm Ă  5 cm. Notre deuxiĂšme contribution dans les systĂšmes de collecte d’énergie porte sur la conception et la mise en oeuvre d’une cage domestique de transmission de puissance sans fil (WPT) pour une plate-forme de neurosciences entiĂšrement sans fil afin de permettre des expĂ©riences optogĂ©nĂ©tiques ininterrompues avec des rongeurs de laboratoire vivants. La cage domestique WPT utilise un nouveau rĂ©seau hybride de transmetteurs de puissance (TX) et des rĂ©sonateurs multi-bobines segmentĂ©s pour atteindre une efficacitĂ© de transmission de puissance Ă©levĂ©e (PTE) et dĂ©livrer une puissance Ă©levĂ©e sur des distances aussi Ă©levĂ©es que 20 cm. Le rĂ©cepteur de puissance Ă  bobines multiples (RX) utilise une bobine RX d’un diamĂštre de 1 cm et une bobine de rĂ©sonateur d’un diamĂštre de 1,5 cm. L’efficacitĂ© moyenne du transfert de puissance WPT est de 29, 4%, Ă  une distance nominale de 7 cm, pour une frĂ©quence porteuse de 13,56 MHz. Il a des PTE maximum et minimum de 50% et 12% le long de l’axe Z et peut dĂ©livrer une puissance constante de 74 mW pour alimenter le headstage neuronal miniature. En outre, un dispositif implantable intĂ©grĂ© dans un processus CMOS TSMC de 0,18-mm a Ă©tĂ© conçu et introduit qui comprend 64 canaux d’enregistrement, 16 canaux de stimulation optique, capteur de tempĂ©rature, Ă©metteur-rĂ©cepteur et unitĂ© de gestion de l’alimentation (PMU). Ce circuit est alimentĂ© Ă  l’intĂ©rieur de la cage du WPT Ă  l’aide d’une bobine rĂ©ceptrice d’un diamĂštre de 1,5 cm pour montrer les performances du circuit PMU. Deux tensions rĂ©gulĂ©es de 1,8 V et 1 V fournissent 79 mW de puissance pour tout le systĂšme sur une puce. Notre derniĂšre contribution est un systĂšme WPT insensible aux dĂ©salignements angulaires pour alimenter un headstage pour des applications optogĂ©nĂ©tiques qui a Ă©tĂ© prĂ©cĂ©demment proposĂ© par le Laboratoire de MicrosystĂšmes BiomĂ©dicaux (BioML-UL) Ă  ULAVAL. Ce systĂšme est la version Ă©tendue de notre deuxiĂšme contribution aux systĂšmes de collecte d’énergie.Dans la version mise Ă  jour, un rĂ©cepteur de puissance multi-bobines utilise une bobine RX d’un diamĂštre de 1,0 cm et une nouvelle bobine de rĂ©sonateur fendu d’un diamĂštre de 1,5 cm, qui rĂ©siste aux dĂ©fauts d’alignement angulaires. Dans cette version qui utilise une cage d’animal plus petite que la derniĂšre version, 4 rĂ©sonateurs sont utilisĂ©s cĂŽtĂ© TX. De plus, grĂące Ă  la forme et Ă  la position de la bobine de rĂ©pĂ©teur L3 du cĂŽtĂ© du rĂ©cepteur, la liaison rĂ©sonnante hybride prĂ©sentĂ©e peut correctement alimenter la tĂȘte sans interruption causĂ©e par le dĂ©salignement angulaire dans toute la cage de la maison. Chaque 3 tours du rĂ©pĂ©teur RX a Ă©tĂ© enveloppĂ© avec un diamĂštre de 1,5 cm, sous diffĂ©rents angles par rapport Ă  la bobine rĂ©ceptrice. Les rĂ©sultats de mesure montrent un PTE maximum et minimum de 53 % et 15 %. La mĂ©thode proposĂ©e peut fournir une puissance constante de 82 mW pour alimenter le petit headstage neural pour les applications optogĂ©nĂ©tiques. De plus, dans cette version, la performance du systĂšme est dĂ©montrĂ©e dans une expĂ©rience in-vivo avec une souris ChR2 en mouvement libre qui est la premiĂšre expĂ©rience optogĂ©nĂ©tique sans fil et sans batterie rapportĂ©e avec enregistrement Ă©lectrophysiologique simultanĂ© et stimulation optogĂ©nĂ©tique. L’activitĂ© Ă©lectrophysiologique a Ă©tĂ© enregistrĂ©e aprĂšs une stimulation optogĂ©nĂ©tique dans le Cortex Cingulaire AntĂ©rieur (CAC) de la souris.Our first contribution in the second part provides a smart home-cage system based on overlapped multi-coil arrays through a thin implantable multi-coil receiver of 1×1 cm2 of size, implantable bellow the scalp of a laboratory mouse, and integrated power management circuits. This inductive system is designed to deliver up to 35.5 mW of power delivered to a fully-integrated, low-power full-duplex transceiver to support high-density and bidirectional neural implants. The transmitter (TX) uses impulse radio ultra-wideband based on an edge combining approach, and the receiver (RX) uses a 2.4- GHz on-off keying narrow band topology. The proposed transceiver provides dual-band 500-Mbps TX uplink data rate and 100-Mbps RX downlink data rate, and it is fully integrated into 0.18-mm TSMC CMOS process within a total size of 0.8 mm2. The power can be delivered from a 13.56-MHz carrier signal with an overall power transfer efficiency above 5% across a separation distance ranging from 3 cm to 5 cm. Our second contribution in power-harvesting systems deals with designing and implementation of a WPT home-cage for a fully wireless neuroscience platform for enabling uninterrupted optogenetic experiments with live laboratory rodents. The WPT home-cage uses a new hybrid parallel power transmitter (TX) coil array and segmented multi-coil resonators to achieve high power transmission efficiency (PTE) and deliver high power across distances as high as 20 cm. The multi-coil power receiver (RX) uses an RX coil with a diameter of 1 cm and a resonator coil with a diameter of 1.5 cm. The WPT home-cage average power transfer efficiency is 29.4%, at a nominal distance of 7 cm, for a power carrier frequency of 13.56-MHz. It has maximum and minimum PTE of 50% and 12% along the Z axis and can deliver a constant power of 74 mW to supply the miniature neural headstage. Also, an implantable device integrated into a 0.18-mm TSMC CMOS process has been designed and introduced which includes 64 recording channels, 16 optical stimulation channels, temperature sensor, transceiver, and power management unit (PMU). This circuit powered up inside the WPT home-cage using receiver coil with a diameter of 1.5 cm to show the performance of the PMU circuit. Two regulated voltages of 1.8 V and 1 V provide 79 mW of power for all the system on a chip. Our last contribution is an angular misalignment insensitive WPT system to power up a headstage which has been previously proposed by the Biomedical Microsystems Laboratory (BioML-UL) at ULAVAL for optogenetic applications. This system is the extended version of our second contribution in power-harvesting systems. In the updated version a multi-coil power receiver uses an RX coil with a diameter of 1.0 cm and a new split resonator coil with a diameter of 1.5 cm, which is robust against angular misalignment. In this version which is using a smaller animal home-cage than the last version, 4 resonators are used on the TX side. Also, thanks to the shape and position of the repeater coil of L3 on the receiver side, the presented hybrid resonant link can properly power up the headstage without interruption caused by the angular misalignment all over the home-cage. Each 3 turns of the RX repeater has been wrapped up with a diameter of 1.5 cm, in different angles compared to the receiver coil. Measurement results show a maximum and minimum PTE of 53 % and 15 %. The proposed method can deliver a constant power of 82 mW to supply the small neural headstage for the optogenetic applications. Additionally, in this version, the performance of the system is demonstrated within an in-vivo experiment with a freely moving ChR2 mouse which is the first fully wireless and batteryless optogenetic experiment reported with simultaneous electrophysiological recording and optogenetic stimulation. Electrophysiological activity was recorded after delivering optogenetic stimulation in the Anterior Cingulate Cortex (ACC) of the mouse.Currently, there is a high demand for Headstage and implantable integrated microsystems to study the brain activity of freely moving laboratory mice. Such devices can interface with the central nervous system in both electrical and optical paradigms for stimulating and monitoring neural circuits, which is critical to discover new drugs and therapies against neurological disorders like epilepsy, depression, and Parkinson’s disease. Since the implantable systems cannot use a battery with a large capacity as a primary source of energy in long-term experiments, the power consumption of the implantable device is one of the leading challenges of these designs. The first part of this research includes our proposed solution for decreasing the power consumption of the implantable microcircuits. We propose a novel level shifter circuit which converting subthreshold signal levels to super-threshold signal levels at high-speed using ultra low power and a small silicon area, making it well-suited for low-power applications such as wireless sensor networks and implantable medical devices. The proposed circuit introduces a new voltage level shifter topology employing a level-shifting capacitor to increase the range of conversion voltages, while significantly reducing the conversion delay. The proposed circuit achieves a shorter propagation delay and a smaller silicon area for a given operating frequency and power consumption compared to other circuit solutions. Measurement results are presented for the proposed circuit fabricated in a 0.18-mm TSMC CMOS process. The presented circuit can convert a wide range of the input voltages from 330 mV to 1.8 V, and operate over a frequency range of 100-Hz to 100-MHz. It has a propagation delay of 29 ns, and power consumption of 61.5 nW for input signals 0.4 V, at a frequency of 500-kHz, outperforming previous designs. The second part of this research includes our proposed wireless power transfer systems for optogenetic applications. Optogenetics is the combination of the genetic and optical method of excitation, recording, and control of the biological neurons. This system combines multiple technologies such as MEMS and microelectronics to collect and transmit the neuronal signals and to activate an optical stimulator through a wireless link. Since optical stimulators consume more power than electrical stimulators, the interface employs induction power transmission using innovative means instead of the battery with the small capacity as a power source

    Recent Advances in Neural Recording Microsystems

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    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

    Coupled resonator based wireless power transfer for bioelectronics

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    Implantable and wearable bioelectronics provide the ability to monitor and modulate physiological processes. They represent a promising set of technologies that can provide new treatment for patients or new tools for scientific discovery, such as in long-term studies involving small animals. As these technologies advance, two trends are clear, miniaturization and increased sophistication i.e. multiple channels, wireless bi-directional communication, and responsiveness (closed-loop devices). One primary challenge in realizing miniaturized and sophisticated bioelectronics is powering. Integration and development of wireless power transfer (WPT) technology, however, can overcome this challenge. In this dissertation, I propose the use of coupled resonator WPT for bioelectronics and present a new generalized analysis and optimization methodology, derived from complex microwave bandpass filter synthesis, for maximizing and controlling coupled resonator based WPT performance. This newly developed set of analysis and optimization methods enables system miniaturization while simultaneously achieving the necessary performance to safely power sophisticated bioelectronics. As an application example, a novel coil to coil based coupled resonator arrangement to wirelessly operate eight surface electromyography sensing devices wrapped circumferentially around an able-bodied arm is developed and demonstrated. In addition to standard coil to coil based systems, this dissertation also presents a new form of coupled resonator WPT system built of a large hollow metallic cavity resonator. By leveraging the analysis and optimization methods developed here, I present a new cavity resonator WPT system for long-term experiments involving small rodents for the first time. The cavity resonator based WPT arena exhibits a volume of 60.96 x 60.96 x 30.0 cm3. In comparison to prior state of the art, this cavity resonator system enables nearly continuous wireless operation of a miniature sophisticated device implanted in a freely behaving rodent within the largest space. Finally, I present preliminary work, providing the foundation for future studies, to demonstrate the feasibility of treating segments of the human body as a dielectric waveguide resonator. This creates another form of a coupled resonator system. Preliminary experiments demonstrated optimized coupled resonator wireless energy transfer into human tissue. The WPT performance achieved to an ultra-miniature sized receive coil (2 mm diameter) is presented. Indeed, optimized coupled resonator systems, broadened to include cavity resonator structures and human formed dielectric resonators, can enable the effective use of coupled resonator based WPT technology to power miniaturized and sophisticated bioelectronics

    Wireless Simultaneous Stimulation-and-Recording Device (SRD) to Train Cortical Circuits in Rat Somatosensory Cortex

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    The primary goal of this project is to develop a wireless system for simultaneous recording-and-stimulation (SRD) to deliver low amplitude current pulses to the primary somatosensory cortex (SI) of rats to activate and enhance an interhemispheric cortical pathway. Despite the existence of an interhemispheric connection between similar forelimb representations of SI cortices, forelimb cortical neurons respond only to input from the contralateral (opposite side) forelimb and not to input from the ipsilateral (same side) forelimb. Given the existence of this interhemispheric pathway we have been able to strengthen/enhance the pathway through chronic intracortical microstimulation (ICMS) in previous acute experiments of anesthetized rats. In these acute experiments strengthening the interhemispheric pathway also brings about functional reorganization whereby cortical neurons in forelimb cortex respond to new input from the ipsilateral forelimb. Having the ability to modify cortical circuitry will have important applications in stroke patients and could serve to rescue and/or enhance responsiveness in surviving cells around the stroke region. Also, the ability to induce functional reorganization within the deafferented cortical map, which follows limb amputation, will also provide a vehicle for modulating maladaptive cortical reorganization often associated with phantom limb pain leading to reduced pain. In order to increase our understanding of the observed functional reorganization and enhanced pathway, we need to be able to test these observations in awake and behaving animals and eventually study how these changes persist over a prolonged period of time. To accomplish this a system was needed to allow simultaneous recording and stimulation in awake rats. However, no such commercial or research system exists that meets all requirements for such an experiment. In this project we describe the (1) system design, (2) system testing, (3) system evaluation, and (4) system implementation of a wireless simultaneous stimulation-and-recording device (SRD) to be used to modulate cortical circuits in an awake rodent animal model

    Physical principles for scalable neural recoding

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    Simultaneously measuring the activities of all neurons in a mammalian brain at millisecond resolution is a challenge beyond the limits of existing techniques in neuroscience. Entirely new approaches may be required, motivating an analysis of the fundamental physical constraints on the problem. We outline the physical principles governing brain activity mapping using optical, electrical, magnetic resonance, and molecular modalities of neural recording. Focusing on the mouse brain, we analyze the scalability of each method, concentrating on the limitations imposed by spatiotemporal resolution, energy dissipation, and volume displacement. Based on this analysis, all existing approaches require orders of magnitude improvement in key parameters. Electrical recording is limited by the low multiplexing capacity of electrodes and their lack of intrinsic spatial resolution, optical methods are constrained by the scattering of visible light in brain tissue, magnetic resonance is hindered by the diffusion and relaxation timescales of water protons, and the implementation of molecular recording is complicated by the stochastic kinetics of enzymes. Understanding the physical limits of brain activity mapping may provide insight into opportunities for novel solutions. For example, unconventional methods for delivering electrodes may enable unprecedented numbers of recording sites, embedded optical devices could allow optical detectors to be placed within a few scattering lengths of the measured neurons, and new classes of molecularly engineered sensors might obviate cumbersome hardware architectures. We also study the physics of powering and communicating with microscale devices embedded in brain tissue and find that, while radio-frequency electromagnetic data transmission suffers from a severe power–bandwidth tradeoff, communication via infrared light or ultrasound may allow high data rates due to the possibility of spatial multiplexing. The use of embedded local recording and wireless data transmission would only be viable, however, given major improvements to the power efficiency of microelectronic devices

    Doctor of Philosophy

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    dissertationThis dissertation describes the use of cortical surface potentials, recorded with dense grids of microelectrodes, for brain-computer interfaces (BCIs). The work presented herein is an in-depth treatment of a broad and interdisciplinary topic, covering issues from electronics to electrodes, signals, and applications. Within the scope of this dissertation are several significant contributions. First, this work was the first to demonstrate that speech and arm movements could be decoded from surface local field potentials (LFPs) recorded in human subjects. Using surface LFPs recorded over face-motor cortex and Wernickes area, 150 trials comprising vocalized articulations of ten different words were classified on a trial-by-trial basis with 86% accuracy. Surface LFPs recorded over the hand and arm area of motor cortex were used to decode continuous hand movements, with correlation of 0.54 between the actual and predicted position over 70 seconds of movement. Second, this work is the first to make a detailed comparison of cortical field potentials recorded intracortically with microelectrodes and at the cortical surface with both micro- and macroelectrodes. Whereas coherence in macroelectrocorticography (ECoG) decayed to half its maximum at 5.1 mm separation in high frequencies, spatial constants of micro-ECoG signals were 530-700 ?m-much closer to the 110-160 ?m calculated for intracortical field potentials than to the macro-ECoG. These findings confirm that cortical surface potentials contain millimeter-scale dynamics. Moreover, these fine spatiotemporal features were important for the performance of speech and arm movement decoding. In addition to contributions in the areas of signals and applications, this dissertation includes a full characterization of the microelectrodes as well as collaborative work in which a custom, low-power microcontroller, with features optimized for biomedical implants, was taped out, fabricated in 65 nm CMOS technology, and tested. A new instruction was implemented in this microcontroller which reduced energy consumption when moving large amounts of data into memory by as much as 44%. This dissertation represents a comprehensive investigation of surface LFPs as an interfacing medium between man and machine. The nature of this work, in both the breadth of topics and depth of interdisciplinary effort, demonstrates an important and developing branch of engineering

    New Techniques in Gastrointestinal Endoscopy

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    As result of progress, endoscopy has became more complex, using more sophisticated devices and has claimed a special form. In this moment, the gastroenterologist performing endoscopy has to be an expert in macroscopic view of the lesions in the gut, with good skills for using standard endoscopes, with good experience in ultrasound (for performing endoscopic ultrasound), with pathology experience for confocal examination. It is compulsory to get experience and to have patience and attention for the follow-up of thousands of images transmitted during capsule endoscopy or to have knowledge in physics necessary for autofluorescence imaging endoscopy. Therefore, the idea of an endoscopist has changed. Examinations mentioned need a special formation, a superior level of instruction, accessible to those who have already gained enough experience in basic diagnostic endoscopy. This is the reason for what these new issues of endoscopy are presented in this book of New techniques in Gastrointestinal Endoscopy

    Bidirectional Propulsion of Devices Along the Gastrointestinal Tract Using Electrostimulation

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    This thesis describes a method for propelling devices such as video capsule endoscopes in either direction along the small intestines using electrostimulation-induced muscular contractions. When swallowed, passive diagnostic ‘one-shot’ devices rely on sporadic peristaltic movement, possibly missing vital ‘areas of interest’. This bidirectional propulsion method provides active control for that all-important ‘second look’. Design considerations, within the dimensional constraints, required a device shape that would achieve maximum propulsion from safely induced useful contractions produced by the electrodes and encapsulated miniature electrostimulator. Construction materials would have to produce minimal friction against the mucosal surface while having the physical properties to facilitate construction and electrode attachment. Design investigations included coefficient of friction measurements of different construction materials and the evaluation of different capsule and electrode dimensions over a range of stimulation parameters, to obtain optimal propulsion. A swallowable 11 mm diameter device was propelled at 121 mm/min with stimulation parameters of 12.5 Hz, 20 ms, at 20 V in an anaesthetised pig. A modified passive video capsule endoscope was propelled at 120 mm/min with stimulation parameters of 12.5 Hz, 20 ms, at 10 V in an unanaesthetised human volunteer. A radio-controlled capsule incorporating an electrostimulator, voltage converter and 3 V power supply was propelled at 60 mm/min with stimulation parameters of 12.5 Hz, 20 ms, and 30 V in an anaesthetised pig. 4 Other possible uses of electrostimulation were investigated including propulsion of anally administered large intestine devices and introduction of the intestinal mucosal surface into a biopsy chamber. Results are presented. The ultimate aim of the project was to provide bidirectional propulsion for wireless remote controlled devices along the gastrointestinal tract utilising contractile force produced by electrostimulation of the intestinal wall. The controllability of this system could provide clinicians with a real time view of the entire small intestines without surgical enteroscopy
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