A Multi-Channel Stimulator With High-Resolution Time-to-Current Conversion for Vagal-Cardiac Neuromodulation

This paper presents an integrated stimulator for a cardiac neuroprosthesis aiming to restore the parasympathetic control after heart transplantation. The stimulator is based on time-to-current conversion. Instead of the conventional current mode digital-to-analog converter (DAC) that uses ten of microamp for biasing, the proposed design uses a novel capacitor time-based DAC offering close to 10 bit of current amplitude resolution while using only a bias current 250 nA. The stimulator chip was design in a 0.18 m CMOS high-voltage (HV) technology. It consists of 16 independent channels, each capable of delivering 550 A stimulus current under a HV output stage that can be operated up to 30 V. Featuring both power efficiency and high-resolution current amplitude stimulation, the design is suitable for multi-channel neural simulation applications

Antena para transferência de potência sem fios para alimentação de dispositivos biomédicos

Trabalho Final de Mestrado para Obtenção do Grau de Mestre em Engenharia BiomédicaÀ semelhança de muitas outras áreas, o campo da medicina tem experimentado novas descobertas e aplicações extraordinárias que fazem com que existam alternativas cada vez mais inovadoras, de modo a melhorar a nossa qualidade de vida. As técnicas de aplicabilidade dos dispositivos médicos implantáveis são um exemplo de como o avanço da tecnologia veio facilitar algumas intervenções cirúrgicas, tornando-as também mais confortáveis para o paciente. No entanto, estes possuem também algumas desvantagens, sendo umas delas a necessidade de usar baterias como fonte de alimentação do dispositivo. Como consequência, estes implantes apresentam um tempo de vida limitado que é geralmente ditado pelo tamanho e capacidade das baterias, e que implica a sua troca com alguma periocidade, trazendo complicações para o paciente. De modo a solucionar este problema, nos últimos anos têm surgido diversos estudos de sistemas que usam antenas para transferir potência para o interior do organismo. No entanto, um dos problemas desta solução é o valor elevado de potência que é refletida quando a antena é colocada em contacto com o corpo humano, causando a desadaptação da mesma. Neste âmbito, e com o objetivo de resolver os problemas descritos, pretendeu-se com esta dissertação apresentar uma antena de dimensões reduzidas, passível de ser utilizada na transferência de potência sem fios, de forma a alimentar um possível dispositivo médico implantável. Para isso, desenhou-se, simulou-se e otimizou-se uma antena para uma banda ISM (902-928 MHz), de modo a estar em contacto com o corpo tendo em conta as propriedades dielétricas e respetivas espessuras das várias camadas do tecido humano. Foram ainda explorados e comparados dois substratos diferentes, nomeadamente o DuPont 951 LTCC (low-temperature cofired ceramics), muito utilizado neste tipo de aplicações e o Rogers RO4360G2, como um material facilmente disponível. Depois de construída o desempenho da antena foi testado numa pessoa e os resultados obtidos foram bastante promissores, permitindo desta forma apresentar uma solução que pode ser interessante num futuro próximo.Like many other areas, the field of medicine has been experiencing new discoveries and extraordinary applications that make alternatives increasingly more innovative, in order to improve our quality of life. The techniques that use mplantable medical devices are an example of how the technology innovation has facilitated some surgical interventions, also making them more comfortable for the patient. However, they also have some disadvantages, one of which is the need to use batteries as power source. Hence, these implants have a limited lifetime that is usually dictated by the size and capacity of the batteries, and that implies their replacement with some periodicity, causing complications for the patient. In order to solve this problem, in recent years, there were several studies of systems that use antennas to transfer power into the body. However, one of the problems with this solution is the high power reflection when the antenna is located in contact with the human body, as it might affect its resonance. In this context and in order to solve the problems described, this dissertation intends to present an antenna with reduced dimensions, which can be used in wireless power transfer, in order to supply a possible implantable medical device. For this purpose, an antenna for the ISM band (902-928 MHz) was designed, simulated and optimized, in order to be in contact with the body, taking into account the dielectric properties and respective thicknesses of the various human tissue layers. Two different substrates were also explored and compared, namely the DuPont 951 LTCC (low-temperature cofired ceramics), widely used in this type of applications and the Rogers RO4360G2, as an easily available material. After the antenna was built, it was tested on a person and the results obtained were very promising, thus allowing to present a solution that may be interesting in the near future.N/

Toward Brain Area Sensor Wireless Network

RÉSUMÉ De nouvelles approches d'interfaçage neuronal de haute performance sont requises pour les interfaces cerveau-machine (BMI) actuelles. Cela nécessite des capacités d'enregistrement/stimulation performantes en termes de vitesse, qualité et quantité, c’est à dire une bande passante à fréquence plus élevée, une résolution spatiale, un signal sur bruit et une zone plus large pour l'interface avec le cortex cérébral. Dans ce mémoire, nous parlons de l'idée générale proposant une méthode d'interfaçage neuronal qui, en comparaison avec l'électroencéphalographie (EEG), l'électrocorticographie (ECoG) et les méthodes d'interfaçage intracortical conventionnelles à une seule unité, offre de meilleures caractéristiques pour implémenter des IMC plus performants. Les avantages de la nouvelle approche sont 1) une résolution spatiale plus élevée - en dessous dumillimètre, et une qualité de signal plus élevée - en termes de rapport signal sur bruit et de contenu fréquentiel - comparé aux méthodes EEG et ECoG; 2) un caractère moins invasif que l'ECoG où l'enlèvement du crâne sous une opération d'enregistrement / stimulation est nécessaire; 3) une plus grande faisabilité de la libre circulation du patient à l'étude - par rapport aux deux méthodes EEG et ECoG où de nombreux fils sont connectés au patient en cours d'opération; 4) une utilisation à long terme puisque l'interface implantable est sans fil - par rapport aux deux méthodes EEG et ECoG qui offrent des temps limités de fonctionnement. Nous présentons l'architecture d'un réseau sans fil de microsystèmes implantables, que nous appelons Brain Area Sensor NETwork (Brain-ASNET). Il y a deux défis principaux dans la réalisation du projet Brain-ASNET. 1) la conception et la mise en oeuvre d'un émetteur-récepteur RF de faible consommation compatible avec la puce de capteurs de réseau implantable, et, 2) la conception d'un protocole de réseau de capteurs sans fil (WSN) ad-hoc économe en énergie. Dans ce mémoire, nous présentons un protocole de réseau ad-hoc économe en énergie pour le réseau désiré, ainsi qu'un procédé pour surmonter le problème de la longueur de paquet variable causé par le processus de remplissage de bit dans le protocole HDLC standard. Le protocole adhoc proposé conçu pour Brain-ASNET présente une meilleure efficacité énergétique par rapport aux protocoles standards tels que ZigBee, Bluetooth et Wi-Fi ainsi que des protocoles ad-hoc de pointe. Le protocole a été conçu et testé par MATLAB et Simulink.----------ABSTRACT New high-performance neural interfacing approaches are demanded for today’s Brain-Machine Interfaces (BMI). This requires high-performance recording/stimulation capabilities in terms of speed, quality, and quantity, i.e. higher frequency bandwidth, spatial resolution, signal-to-noise, and wider area to interface with the cerebral cortex. In this thesis, we talk about the general proposed idea of a neural interfacing method which in comparison with Electroencephalography (EEG), Electrocorticography (ECoG), and, conventional Single-Unit Intracortical neural interfacing methods offers better features to implement higher-performance BMIs. The new approach advantages are 1) higher spatial resolution – down to sub-millimeter, and higher signal quality − in terms of signal-to-noise ratio and frequency content − compared to both EEG and ECoG methods. 2) being less invasive than ECoG where skull removal Under recording/stimulation surgery is required. 3) higher feasibility of freely movement of patient under study − compared to both EEG and ECoG methods where lots of wires are connected to the patient under operation. 4) long-term usage as the implantable interface is wireless − compared to both EEG and ECoG methods where it is practical for only a limited time under operation. We present the architecture of a wireless network of implantable microsystems, which we call it Brain Area Sensor NETwork (Brain-ASNET). There are two main challenges in realization of the proposed Brain-ASNET. 1) design and implementation of power-hungry RF transceiver of the implantable network sensors' chip, and, 2) design of an energy-efficient ad-hoc Wireless Sensor Network (WSN) protocol. In this thesis, we introduce an energy-efficient ad-hoc network protocol for the desired network, along with a method to overcome the issue of variable packet length caused by bit stuffing process in standard HDLC protocol. The proposed ad-hoc protocol designed for Brain-ASNET shows better energy-efficiency compared to standard protocols like ZigBee, Bluetooth, and Wi-Fi as well as state-of-the-art ad-hoc protocols. The protocol was designed and tested by MATLAB and Simulink

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

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