490 research outputs found

    Miniaturised Wireless Power Transfer Systems for Neurostimulation: A Review

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    In neurostimulation, wireless power transfer is an efficient technology to overcome several limitations affecting medical devices currently used in clinical practice. Several methods were developed over the years for wireless power transfer. In this review article, we report and discuss the three most relevant methodologies for extremely miniaturised implantable neurostimulator: ultrasound coupling, inductive coupling and capacitive coupling. For each powering method, the discussion starts describing the physical working principle. In particular, we focus on the challenges given by the miniaturisation of the implanted integrated circuits and the related ad-hoc solutions for wireless power transfer. Then, we present recent developments and progresses in wireless power transfer for biomedical applications. Last, we compare each technique based on key performance indicators to highlight the most relevant and innovative solutions suitable for neurostimulation, with the gaze turned towards miniaturisation

    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)

    Fully-Implantable Self-Contained Dual-Channel Electrical Recording and Directivity-Enhanced Optical Stimulation System on a Chip

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    This thesis presents an integrated system-on-a-chip (SoC), designed, fabricated, and characterized for conducting simultaneous dual-channel optogenetic stimulation and electrophysiological recording. An inductive coil as well as power management circuits are also integrated on the chip, enabling wireless power reception, hence, allowing full implantation. The optical stimulation channels host a novel LED driver circuit that can generate currents up to 10mA with a minimum required headroom voltage reported in the literature, resulting in a superior power efficiency compared to the state of the art. The output current in each channel can be programmed to have an arbitrary waveform with digitally-controlled magnitude and timing. The final design is fabricated as a 34 mm2 microchip using a CMOS 130nm technology and characterized both in terms of electrical and optical performance. A pair of custom-designed inkjet-printed micro-lenses are also fabricated and placed on top of the LEDs. The lenses are optimized to enhance the light directivity of optical stimulation, resulting in significant improvements in terms of spatial resolution, power consumption (30.5x reduction), and safety aspects (temperature increase of <0.1c) of the device

    Bioelectronic Sensor Nodes for Internet of Bodies

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    Energy-efficient sensing with Physically-secure communication for bio-sensors on, around and within the Human Body is a major area of research today for development of low-cost healthcare, enabling continuous monitoring and/or secure, perpetual operation. These devices, when used as a network of nodes form the Internet of Bodies (IoB), which poses certain challenges including stringent resource constraints (power/area/computation/memory), simultaneous sensing and communication, and security vulnerabilities as evidenced by the DHS and FDA advisories. One other major challenge is to find an efficient on-body energy harvesting method to support the sensing, communication, and security sub-modules. Due to the limitations in the harvested amount of energy, we require reduction of energy consumed per unit information, making the use of in-sensor analytics/processing imperative. In this paper, we review the challenges and opportunities in low-power sensing, processing and communication, with possible powering modalities for future bio-sensor nodes. Specifically, we analyze, compare and contrast (a) different sensing mechanisms such as voltage/current domain vs time-domain, (b) low-power, secure communication modalities including wireless techniques and human-body communication, and (c) different powering techniques for both wearable devices and implants.Comment: 30 pages, 5 Figures. This is a pre-print version of the article which has been accepted for Publication in Volume 25 of the Annual Review of Biomedical Engineering (2023). Only Personal Use is Permitte

    Intra-Body Communications for Nervous System Applications: Current Technologies and Future Directions

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    The Internet of Medical Things (IoMT) paradigm will enable next generation healthcare by enhancing human abilities, supporting continuous body monitoring and restoring lost physiological functions due to serious impairments. This paper presents intra-body communication solutions that interconnect implantable devices for application to the nervous system, challenging the specific features of the complex intra-body scenario. The presented approaches include both speculative and implementative methods, ranging from neural signal transmission to testbeds, to be applied to specific neural diseases therapies. Also future directions in this research area are considered to overcome the existing technical challenges mainly associated with miniaturization, power supply, and multi-scale communications.Comment: https://www.sciencedirect.com/science/article/pii/S138912862300163

    Biointegrated and wirelessly powered implantable brain devices: a review

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    Implantable neural interfacing devices have added significantly to neural engineering by introducing the low-frequency oscillations of small populations of neurons known as local field potential as well as high-frequency action potentials of individual neurons. Regardless of the astounding progression as of late, conventional neural modulating system is still incapable to achieve the desired chronic in vivo implantation. The real constraint emerges from mechanical and physical diffierences between implants and brain tissue that initiates an inflammatory reaction and glial scar formation that reduces the recording and stimulation quality. Furthermore, traditional strategies consisting of rigid and tethered neural devices cause substantial tissue damage and impede the natural behaviour of an animal, thus hindering chronic in vivo measurements. Therefore, enabling fully implantable neural devices, requires biocompatibility, wireless power/data capability, biointegration using thin and flexible electronics, and chronic recording properties. This paper reviews biocompatibility and design approaches for developing biointegrated and wirelessly powered implantable neural devices in animals aimed at long-term neural interfacing and outlines current challenges toward developing the next generation of implantable neural devices

    Implantable Neural Probes for Brain-Machine Interfaces - Current Developments and Future Prospects

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    A Brain-Machine interface (BMI) allows for direct communication between the brain and machines. Neural probes for recording neural signals are among the essential components of a BMI system. In this report, we review research regarding implantable neural probes and their applications to BMIs. We first discuss conventional neural probes such as the tetrode, Utah array, Michigan probe, and electroencephalography (ECoG), following which we cover advancements in next-generation neural probes. These next-generation probes are associated with improvements in electrical properties, mechanical durability, biocompatibility, and offer a high degree of freedom in practical settings. Specifically, we focus on three key topics: (1) novel implantable neural probes that decrease the level of invasiveness without sacrificing performance, (2) multi-modal neural probes that measure both electrical and optical signals, (3) and neural probes developed using advanced materials. Because safety and precision are critical for practical applications of BMI systems, future studies should aim to enhance these properties when developing next-generation neural probes

    A multi-channel stimulator with an active electrode array implant for vagal-cardiac neuromodulation studies.

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    Background: Implantable vagus nerve stimulation is a promising approach for restoring autonomic cardiovascular functions after heart transplantation. For successful treatment a system should have multiple electrodes to deliver precise stimulation and complex neuromodulation patterns. Methods: This paper presents an implantable multi-channel stimulation system for vagal-cardiac neuromodulation studies in swine species. The system comprises an active electrode array implant percutaneously connected to an external wearable controller. The active electrode array implant has an integrated stimulator ASIC mounted on a ceramic substrate connected to an intraneural electrode array via micro-rivet bonding. The implant is silicone encapsulated for biocompatibility and implanted lifetime. The stimulation parameters are remotely transmitted via a Bluetooth telemetry link. Results: The size of the encapsulated active electrode array implant is 8 mm × 10 mm × 3 mm. The stimulator ASIC has 10-bit current amplitude resolution and 16 independent output channels, each capable of delivering up to 550 ÎŒA stimulus current and a maximum voltage of 20 V. The active electrode array implant was subjected to in vitro accelerated lifetime testing at 70 °C for 7 days with no degradation in performance. After over 2 h continuous stimulation, the surface temperature change of the implant was less than 0.5 °C. In addition, in vivo testing on the sciatic nerve of a male Göttingen minipig demonstrated that the implant could effectively elicit an EMG response that grew progressively stronger on increasing the amplitude of the stimulation. Conclusions: The multi-channel stimulator is suitable for long term implantation. It shows potential as a useful tool in vagal-cardiac neuromodulation studies in animal models for restoring autonomic cardiovascular functions after heart transplantation
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