655 research outputs found

    A High TCMRR, Inherently Charge Balanced Bidirectional Front-End for Multichannel Closed-Loop Neuromodulation

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    This paper describes a multichannel bidirectional front-end for implantable closed-loop neuromodulation. Stimulation artefacts are reduced by way of a 4-channel H-bridge current source sharing stimulator front-end that minimizes residual charge drops in the electrodes via topology-inherent charge balancing. A 4-channel chopper front-end is capable of multichannel recording in the presence of artefacts as a result of its high total common-mode rejection ratio (TCMRR) that accounts for CMRR degradation due to electrode mismatch. Experimental verification of a prototype fabricated in a standard 180 nm process shows a stimulator front-end with 0.059% charge balance and 0.275 nA DC current error. The recording front-end consumes 3.24 ”W, tolerates common-mode interference up to 1 Vpp and shows a TCMRR > 66 dB for 500 mVpp inputs.Ministerio de Economía y Competitividad TEC2016-80923-POffice of Naval Research (USA) N00014111031

    A vestibular prosthesis with highly-isolated parallel multichannel stimulation.

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    This paper presents an implantable vestibular stimulation system capable of providing high flexibility independent parallel stimulation to the semicircular canals in the inner ear for restoring three-dimensional sensation of head movements. To minimize channel interaction during parallel stimulation, the system is implemented with a power isolation method for crosstalk reduction. Experimental results demonstrate that, with this method, electrodes for different stimulation channels located in close proximity ( mm) can deliver current pulses simultaneously with minimum inter-channel crosstalk. The design features a memory-based scheme that manages stimulation to the three canals in parallel. A vestibular evoked potential (VEP) recording unit is included for closed-loop adaptive stimulation control. The main components of the prototype vestibular prosthesis are three ASICs, all implemented in a 0.6- ÎŒm high-voltage CMOS technology. The measured performance was verified using vestibular electrodes in vitro

    An Energy-Efficient, Dynamic Voltage Scaling Neural Stimulator for a Proprioceptive Prosthesis

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    An Implantable Mixed Analog/Digital Neural Stimulator Circuit

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    Integrated circuit design for implantable neural interfaces

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    Progress in microfabrication technology has opened the way for new possibilities in neuroscience and medicine. Chronic, biocompatible brain implants with recording and stimulation capabilities provided by embedded electronics have been successfully demonstrated. However, more ambitious applications call for improvements in every aspect of existing implementations. This thesis proposes two prototypes that advance the field in significant ways. The first prototype is a neural recording front-end with spectral selectivity capabilities that implements a design strategy that leads to the lowest reported power consumption as compared to the state of the art. The second one is a bidirectional front-end for closed-loop neuromodulation that accounts for self-interference and impedance mismatch thus enabling simultaneous recording and stimulation. The design process and experimental verification of both prototypes is presented herein

    A Partial-Current-Steering Biphasic Stimulation Driver for Vestibular Prostheses

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    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

    A 16-Channel Neural Recording System-on-Chip With CHT Feature Extraction Processor in 65-nm CMOS

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    Next-generation invasive neural interfaces require fully implantable wireless systems that can record from a large number of channels simultaneously. However, transferring the recorded data from the implant to an external receiver emerges as a significant challenge due to the high throughput. To address this challenge, this article presents a neural recording system-on-chip that achieves high resource and wireless bandwidth efficiency by employing on-chip feature extraction. Energy-area-efficient 10-bit 20-kS/s front end amplifies and digitizes the neural signals within the local field potential (LFP) and action potential (AP) bands. The raw data from each channel are decomposed into spectral features using a compressed Hadamard transform (CHT) processor. The selection of the features to be computed is tailored through a machine learning algorithm such that the overall data rate is reduced by 80% without compromising classification performance. Moreover, the CHT feature extractor allows waveform reconstruction on the receiver side for monitoring or additional post-processing. The proposed approach was validated through in vivo and off-line experiments. The prototype fabricated in 65-nm CMOS also includes wireless power and data receiver blocks to demonstrate the energy and area efficiency of the complete system. The overall signal chain consumes 2.6 ÎŒW and occupies 0.021 mmÂČ per channel, pointing toward its feasibility for 1000-channel single-die neural recording systems

    Design and Implementation of a Passive Neurostimulator with Wireless Resonance-Coupled Power Delivery and Demonstration on Frog Sciatic Nerve and Gastrocnemius Muscle

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    The thesis presented has four goals: to perform a comprehensive literature review on current neurostimulator technology; to outline the current issues with the state-of-the-art; to provide a neurostimulator design that solves these issues, and to characterize the design and demonstrate its neurostimulation features. The literature review describes the physiology of a neuron, and then proceeds to outline neural interfaces and neurostimulators. The neurostimulator design process is then outlined and current requirements in the field are described. The novel neurostimulator circuit that implements a solution that has wireless capability, passive control, and small size is outlined and characterized. The circuit is demonstrated to operate wirelessly with a resonance-coupled multi-channel implementation, and is shown powering LEDs. The circuit was then fabricated in a miniature implementation which utilized a 10 x 20 x 3 mm&179 antenna, and occupied a volume approximating 1 cm&179. This miniature circuit is used to stimulate frog sciatic nerve and gastrocnemius muscle in vitro. These demonstrations and characterization show the device is capable of neurostimulation, can operate wirelessly, is controlled passively, and can be implemented in a small size, thus solving the aforementioned neurostimulator requirements. Further work in this area is focused on developing an extensive characterization of the device and the wireless power delivery system, optimizing the circuit design, and performing in vivo experiments with restoration of motor control in injured animals. This device shows promise to provide a comprehensive solution to many application-specific problems in neurostimulation, and be a modular addition to larger neural interface systems

    Bidirectional Neural Interface Circuits with On-Chip Stimulation Artifact Reduction Schemes

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    Bidirectional neural interfaces are tools designed to “communicate” with the brain via recording and modulation of neuronal activity. The bidirectional interface systems have been adopted for many applications. Neuroscientists employ them to map neuronal circuits through precise stimulation and recording. Medical doctors deploy them as adaptable medical devices which control therapeutic stimulation parameters based on monitoring real-time neural activity. Brain-machine-interface (BMI) researchers use neural interfaces to bypass the nervous system and directly control neuroprosthetics or brain-computer-interface (BCI) spellers. In bidirectional interfaces, the implantable transducers as well as the corresponding electronic circuits and systems face several challenges. A high channel count, low power consumption, and reduced system size are desirable for potential chronic deployment and wider applicability. Moreover, a neural interface designed for robust closed-loop operation requires the mitigation of stimulation artifacts which corrupt the recorded signals. This dissertation introduces several techniques targeting low power consumption, small size, and reduction of stimulation artifacts. These techniques are implemented for extracellular electrophysiological recording and two stimulation modalities: direct current stimulation for closed-loop control of seizure detection/quench and optical stimulation for optogenetic studies. While the two modalities differ in their mechanisms, hardware implementation, and applications, they share many crucial system-level challenges. The first method aims at solving the critical issue of stimulation artifacts saturating the preamplifier in the recording front-end. To prevent saturation, a novel mixed-signal stimulation artifact cancellation circuit is devised to subtract the artifact before amplification and maintain the standard input range of a power-hungry preamplifier. Additional novel techniques have been also implemented to lower the noise and power consumption. A common average referencing (CAR) front-end circuit eliminates the cross-channel common mode noise by averaging and subtracting it in analog domain. A range-adapting SAR ADC saves additional power by eliminating unnecessary conversion cycles when the input signal is small. Measurements of an integrated circuit (IC) prototype demonstrate the attenuation of stimulation artifacts by up to 42 dB and cross-channel noise suppression by up to 39.8 dB. The power consumption per channel is maintained at 330 nW, while the area per channel is only 0.17 mm2. The second system implements a compact headstage for closed-loop optogenetic stimulation and electrophysiological recording. This design targets a miniaturized form factor, high channel count, and high-precision stimulation control suitable for rodent in-vivo optogenetic studies. Monolithically integrated optoelectrodes (which include 12 ”LEDs for optical stimulation and 12 electrical recording sites) are combined with an off-the-shelf recording IC and a custom-designed high-precision LED driver. 32 recording and 12 stimulation channels can be individually accessed and controlled on a small headstage with dimensions of 2.16 x 2.38 x 0.35 cm and mass of 1.9 g. A third system prototype improves the optogenetic headstage prototype by furthering system integration and improving power efficiency facilitating wireless operation. The custom application-specific integrated circuit (ASIC) combines recording and stimulation channels with a power management unit, allowing the system to be powered by an ultra-light Li-ion battery. Additionally, the ”LED drivers include a high-resolution arbitrary waveform generation mode for shaping of ”LED current pulses to preemptively reduce artifacts. A prototype IC occupies 7.66 mm2, consumes 3.04 mW under typical operating conditions, and the optical pulse shaping scheme can attenuate stimulation artifacts by up to 3x with a Gaussian-rise pulse rise time under 1 ms.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147674/1/mendrela_1.pd
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