Ultra-Miniaturised CMOS Current Driver for Wireless Biphasic Intracortical Microstimulation

This work shows an ultra-miniaturised and ultralow-power CMOS current driver for biphasic intracortical microstimulation. The CMOS driver is composed of a leakage-based voltage-to-current converter and an H-bridge circuit providing biphasic charge-balanced current stimulation. The circuit has been simulated, fabricated and tested. The current driver consumes 1.87 µW with a supply voltage of 1.8 V, and it occupies a silicon area of 15×12.4 µm 2 . The driver works in linearity in the current range between 23−92 µ

Neurostimulateur hautement intégré et nouvelle stratégie de stimulation pour améliorer la miction chez les paraplégiques

RÉSUMÉ Une lésion de la moelle épinière est un problème dévastateur médicalement et socialement. Pour la population des États-Unis seulement, il y a près de 10 000 nouveaux cas chaque année. A cause des nombreux types de lésions possibles, divers degrés de dysfonctionnement du bas appareil urinaire peuvent en découler. Une lésion est dite complète lors d’une perte totale des fonctions sensorielles et motrices volontaires en dessous du niveau de la lésion. Une lésion incomplète implique que certaines activités sensorielles et/ou motrices soient encore présentes. Si la lésion se produit au dessus du cône médullaire, la vessie développera une hyperréflexie qui se manifeste par des contractions réflexes non-inhibées. Ces contractions peuvent être accompagnées d’une augmentation de l’activité du sphincter externe. Par conséquent, cela mène à un état d’obstruction fonctionnelle de la vessie, qui induit une forte pression intravésicale à chacune des contractions réflexes et qui peut potentiellement endommager le haut appareil urinaire. Dans ce contexte, la neurostimulation est l'une des techniques les plus prometteuses pour la réhabilitation de la vessie chez les patients ayant subi une lésion de la moelle épinière. Le seul neurostimulateur implantable commercialisé, ciblant l'amélioration de la miction et ayant obtenu des résultats satisfaisants, nécessite une rhizotomie (section de certains nerfs) afin de réduire la dyssynergie entre la vessie et le sphincter. Cependant, la rhizotomie est irréversible et peut abolir les réflexes sexuels, de défécation ainsi que les sensations sacrales si encore présents dans le cas de lésions incomplètes. Afin d'éviter la rhizotomie, nous proposons une nouvelle stratégie de stimulation multi-site appliquée aux racines sacrées, et basée sur le blocage de la conduction des nerfs à l'aide d'une stimulation à haute fréquence comme alternative à la rhizotomie. Cette approche permettrait une meilleure miction en augmentant sélectivement la contraction de la vessie et en diminuant la dyssynergie. Huit expériences en phase aigüe ont étés menées sur des chiens pour vérifier la réponse de la vessie et du sphincter urétral externe à la stratégie de stimulation proposée. Le blocage à haute-fréquence (1 kHz) combiné à la stimulation basse-fréquence (30 Hz), a augmenté la différence de pression intra-vésicale/intra-urétrale moyenne jusqu'à 53 cmH2O et a réduit la pression intra-urétrale moyenne jusqu'à hauteur de 86 % relativement au niveau de référence. Dans l’objectif de tester la stratégie de neurostimulation proposée avec des expériences animales en phase chronique, un dispositif de neurostimulation implantable est requis. Un prototype discret implémentant cette stratégie de stimulation a été réalisé en utilisant uniquement des composants discrets disponibles commercialement. Ce prototype est capable de générer des impulsions à une fréquence aussi basse que 18 Hz tout en générant simultanément une forme d’onde alternative à une fréquence aussi haute que 8.6 kHz, et ce sur de multiples canaux. Lorsque tous les étages de stimulation et leurs différentes sorties sont activés avec des fréquences d’impulsions (2 mA, 217 μs) et de sinusoïdes de 30 Hz et 1 kHz respectivement, la consommation de puissance totale est autour de 4.5 mA (rms). Avec 50 mW de puissance inductive disponible par exemple et 4.5 mA de consommation de courant, le régulateur haute-tension peut être réglé à 10 V permettant ainsi une stimulation de 2 mA avec une impédance nerf-électrode de 4.4 kΩ. Le nombre effectif de sorties activées et le maximum réalisable des paramètres de stimulation sont limités par l’énergie disponible fournie par le lien inductif et l’impédance des interfaces nerf-électrode. Cependant, une plus grande intégration du neurostimulateur devient de plus en plus nécessaire à des fins de miniaturisation, de réduction de consommation de puissance, et d’augmentation du nombre de canaux de stimulation. Comme première étape vers une intégration totale, nous présentons la conception d’un neurostimulateur hautement intégré et qui peut être assemblé sur un circuit imprimé de 21 mm de diamètre. Le prototype est basé sur trois circuits intégrés, dédiés et fabriqués en technologie CMOS haute-tension, ainsi qu’un FPGA miniature à faible puissance et disponible commercialement. En utilisant une approche basée sur un abaisseur de tension, où la tension induite est laissée libre jusqu’à 20 V, l’étage d’entrée de récupération de puissance inductive et de données est totalement intégré.----------ABSTRACT Spinal cord injury (SCI) is a devastating condition medically and socially. For the population of USA only, the incidence is around 10 000 new cases per year. SCI leads to different degrees of dysfunction of the lower urinary tract due to a large variety of possible lesions. With a complete lesion, there is a complete loss of sensory and motor control below the level of lesion. An incomplete lesion implies that some sensory and/or motor activity is still present. Most patients with suprasacral SCI suffer from detrusor over-activity (DO) and detrusor sphincter dyssynergia (DSD). DSD leads to high intravesical pressure, high residual urine, urinary tract infection, and deterioration of the upper urinary tract. In this context, neurostimulation is one of the most promising techniques for bladder rehabilitation in SCI patients. The only commercialized implantable neurostimulator aiming for improved micturition and having obtained satisfactory results requires rhizotomy to reduce DSD. However, rhizotomy is irreversible and may abolish sexual and defecation reflexes as well as sacral sensations, if still present in case of incomplete SCI. In order to avoid rhizotomy, we propose a new multisite stimulation strategy applied to sacral roots, and based on nerve conduction blockade using high-frequency stimulation as an alternative to rhizotomy. This approach would allow a better micturition by increasing bladder contraction selectively and decreasing dyssynergia. Eight acute dog experiments were carried out to verify the bladder and the external urethral sphincter responses to the proposed stimulation strategy. High-frequency blockade (1 kHz) combined with low-frequency stimulation (30 Hz) increased the average intravesical-intraurethral pressure difference up to 53 cmH2O and reduced the average intraurethral pressure with respect to baseline by up to 86 %. To test the proposed neurostimulation strategy during chronic animal experiments, an implantable neurostimulateur is required. A discrete prototype implementing the proposed stimulation strategy has been designed using commercially available discrete components. This prototype is capable of generating a low frequency pulse waveform as low as 18 Hz with a simultaneous high frequency alternating waveform as high as 8.6 kHz, and that over different and multiple channels

Electromechanical and biological evaluations of 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 as a lead-free piezoceramic for implantable bioelectronics

Smart implantable electronic medical devices are being developed to deliver healthcare that is more connected, personalised, and precise. Many of these implantables rely on piezoceramics for sensing, communication, energy autonomy, and biological stimulation, but the piezoceramics with the strongest piezoelectric coefficients are almost exclusively lead-based. In this article, we evaluate the electromechanical and biological characteristics of a lead-free alternative, 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 (BNT-6BT), manufactured via two synthesis routes: the conventional solid-state method (PIC700) and tape casting (TC-BNT-6BT). The BNT-6BT materials exhibited soft piezoelectric properties, with d33 piezoelectric coefficients that were inferior to commonly used PZT (PIC700: 116 pC/N; TC-BNT-6BT: 121 pC/N; PZT-5A: 400 pC/N). The material may be viable as a lead-free substitute for soft PZT where moderate performance losses up to 10 dB are tolerable, such as pressure sensing and pulse-echo measurement. No short-term harmful biological effects of BNT-6BT were detected and the material was conducive to the proliferation of MC3T3-E1 murine preosteoblasts. BNT-6BT could therefore be a viable material for electroactive implants and implantable electronics without the need for hermetic sealing

Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors

This reprint is a collection of the Special Issue "Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors" published in Nanomaterials, which includes one editorial, six novel research articles and four review articles, showcasing the very recent advances in energy-harvesting and self-powered sensing technologies. With its broad coverage of innovations in transducing/sensing mechanisms, material and structural designs, system integration and applications, as well as the timely reviews of the progress in energy harvesting and self-powered sensing technologies, this reprint could give readers an excellent overview of the challenges, opportunities, advancements and development trends of this rapidly evolving field

Acoustic Power Transfer Leveraging Piezoelectricity and Metamaterials

Acoustic power transfer, or ultrasonic power transfer (UPT) more specifically, has received growing attention as a viable approach for wireless power delivery to low-power electronic devices. It has found applications in powering biomedical implants, sensors in sealed metallic enclosures, and sensors deep in the ocean. The design of an efficient UPT system requires coupled multiphysics modeling to establish strategies toward maximizing the transferred power. This work, first, investigates different analytical and numerical models to analyze the performance of UPT systems to increase the transferred power. Various electromechanical models are developed to represent the transducer (transmitter or receiver) and overall system dynamics for a broad range of aspect ratios covering the diverse UPT applications. The main challenges that limit UPT system efficiency such as attenuation, power divergence, and reflection due to impedance mismatch issues are investigated using the developed models. These effects are investigated at the system level with an application to transfer power through metallic barriers using bonded piezoelectric disc transducers. A complete system for transferring power from the battery of a transmitter to the DC load of a receiver is designed and simulated, then experimentally tested. The experimental results of the system agree well with the modeling predictions, and the system can deliver 17.5 W to a DC load with a total DC-to-DC efficiency of 66 %. A second system with a portable and detachable dry-coupled transmitter is also experimentally tested. The dry-coupled system can deliver 3 W of DC power with 50 % efficiency from a 9V battery. Novel approaches using acoustic metamaterials/phononic crystals are introduced to enhance the efficiency of UPT through wave focusing. Specifically, two 3D phononic crystal structures based on air in a 3D-printed polymer matrix are introduced to manipulate acoustic waves both under water and in air. Two designs for gradient-index lenses are fabricated and experimentally characterized to focus acoustic waves on a piezoelectric receiver, thereby dramatically enhancing the power output. Finally, acoustic and electrical impedance matching are investigated for sending both power and data using ultrasonic waves. Several impedance matching techniques are proposed to maximize transducer bandwidth, power efficiency, as well as sensitivity for underwater data transfer. A novel approach is introduced for achieving simultaneous power and data transfer using frequency multiplexing with a single transducer. The introduced designs allow for configurable matching for maximizing power efficiency, maximizing data transfer, or simultaneously sending power to the transducer while receiving data with lower bandwidth.Ph.D

Biomedical Engineering

Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development

An Ultrasonically Powered and Controlled Ultra-High-Frequency Biphasic Electrical Neurostimulator

This paper presents the design of a neurostimulator performing biphasic ultra-high-frequency electrical stimulation while being driven from ultrasound energy. Unlike conventional constant current or constant voltage stimulators or state-of-the-art ultra-high-frequency stimulators, the system does not convert the input AC signal into regulated DC for storing power and supplying the elements of the circuits. Instead, it uses the received ultrasonic signal frequency (≥1 MHz) for electrically stimulating the tissue directly, and it achieves biphasic stimulation with external control and without storing extra power. This results in a highly efficient and miniature circuit, which has the potential to be used in bioelectronic medicine for stimulating small peripheral nerves deep inside the body. The operation of the circuit was first simulated in LTSpice using a lumped elements model for the impedance of the piezoelectric receivers and the load. Finally, a prototype was tested in vitro with commercial transducers and platinum-iridium electrodes as load.Accepted author manuscriptBio-Electronic

An Ultrasonically Powered and Controlled Ultra-High-Frequency Biphasic Electrical Neurostimulator

This paper presents the design of a neurostimulator performing biphasic ultra-high-frequency electrical stimulation while being driven from ultrasound energy. Unlike conventional constant current or constant voltage stimulators or state-of-the-art ultra-high-frequency stimulators, the system does not convert the input AC signal into regulated DC for storing power and supplying the elements of the circuits. Instead, it uses the received ultrasonic signal frequency (≥1 MHz) for electrically stimulating the tissue directly, and it achieves biphasic stimulation with external control and without storing extra power. This results in a highly efficient and miniature circuit, which has the potential to be used in bioelectronic medicine for stimulating small peripheral nerves deep inside the body. The operation of the circuit was first simulated in LTSpice using a lumped elements model for the impedance of the piezoelectric receivers and the load. Finally, a prototype was tested in vitro with commercial transducers and platinum-iridium electrodes as load.</p