86 research outputs found
Energy-Optimal Electrical-Stimulation Pulses Shaped by the Least-Action Principle
Electrical stimulation (ES) devices interact with excitable neural tissue toward eliciting action potentials (AP's) by specific current patterns. Low-energy ES prevents tissue damage and loss of specificity. Hence to identify optimal stimulation-current waveforms is a relevant problem, whose solution may have significant impact on the related medical (e. g. minimized side-effects) and engineering (e. g. maximized battery-life) efficiency. This has typically been addressed by simulation (of a given excitable-tissue model) and iterative numerical optimization with hard discontinuous constraints - e.g. AP's are all-or-none phenomena. Such approach is computationally expensive, while the solution is uncertain - e. g. may converge to local-only energy-minima and be model-specific. We exploit the Least-Action Principle (LAP). First, we derive in closed form the general template of the membrane-potential's temporal trajectory, which minimizes the ES energy integral over time and over any space-clamp ionic current model. From the given model we then obtain the specific energy-efficient current waveform, which is demonstrated to be globally optimal. The solution is model-independent by construction. We illustrate the approach by a broad set of example situations with some of the most popular ionic current models from the literature. The proposed approach may result in the significant improvement of solution efficiency: cumbersome and uncertain iteration is replaced by a single quadrature of a system of ordinary differential equations. The approach is further validated by enabling a general comparison to the conventional simulation and optimization results from the literature, including one of our own, based on finite-horizon optimal control. Applying the LAP also resulted in a number of general ES optimality principles. One such succinct observation is that ES with long pulse durations is much more sensitive to the pulse's shape whereas a rectangular pulse is most frequently optimal for short pulse durations
Integrated Circuits and Systems for Smart Sensory Applications
Connected intelligent sensing reshapes our society by empowering people with increasing new ways of mutual interactions. As integration technologies keep their scaling roadmap, the horizon of sensory applications is rapidly widening, thanks to myriad light-weight low-power or, in same cases even self-powered, smart devices with high-connectivity capabilities. CMOS integrated circuits technology is the best candidate to supply the required smartness and to pioneer these emerging sensory systems. As a result, new challenges are arising around the design of these integrated circuits and systems for sensory applications in terms of low-power edge computing, power management strategies, low-range wireless communications, integration with sensing devices. In this Special Issue recent advances in application-specific integrated circuits (ASIC) and systems for smart sensory applications in the following five emerging topics: (I) dedicated short-range communications transceivers; (II) digital smart sensors, (III) implantable neural interfaces, (IV) Power Management Strategies in wireless sensor nodes and (V) neuromorphic hardware
An implantable micro-system for neural prosthesis control and sensory feedback restoration in amputees
In this work, the prototype of an electronic bi-directional interface between the Peripheral
Nervous System (PNS) and a neuro-controlled hand prosthesis is presented. The system is
composed of two Integrated Circuits (ICs): a standard CMOS device for neural recording and
a High Voltage (HV) CMOS device for neural stimulation. The integrated circuits have been
realized in two different 0.35μm CMOS processes available fromAustriaMicroSystem(AMS).
The recoding IC incorporates 8 channels each including the analog front-end and the A/D
conversion based on a sigma delta architecture. It has a total area of 16.8mm2 and exhibits
an overall power consumption of 27.2mW. The neural stimulation IC is able to provide biphasic
current pulses to stimulate 8 electrodes independently. A voltage booster generates a
17V voltage supply in order to guarantee the programmed stimulation current even in case
of high impedances at the electrode-tissue interface in the order of tens of kÂ. The stimulation
patterns, generated by a 5-bit current DAC, are programmable in terms of amplitude,
frequency and pulse width. Due to the huge capacitors of the implemented voltage boosters,
the stimulation IC has a wider area of 18.6mm2. In addition, a maximum power consumption
of 29mW was measured. Successful in-vivo experiments with rats having a TIME
electrode implanted in the sciatic nerve were carried out, showing the capability of recording
neural signals in the tens of microvolts, with a global noise of 7μVrms , and to selectively
elicit the tibial and plantarmuscles using different active sites of the electrode.
In order to get a completely implantable interface, a biocompatible and biostable package
was designed. It hosts the developed ICs with the minimal electronics required for their
proper operation. The package consists of an alumina tube closed at both extremities by
two ceramic caps hermetically sealed on it. Moreover, the two caps serve as substrate for
the hermetic feedthroughs to enable the device powering and data exchange with the external
digital controller implemented on a Field-Programmable Gate Array (FPGA) board. The
package has an outer diameter of 7mm and a total length of 26mm. In addition, a humidity
and temperature sensor was also included inside the package to allow future hermeticity
and life-time estimation tests.
Moreover, a wireless, wearable and non-invasive EEG recording system is proposed in order
to improve the control over the artificial limb,by integrating the neural signals recorded from
the PNS with those directly acquired from the brain. To first investigate the system requirements,
a Component-Off-The-Shelf (COTS) device was designed. It includes a low-power 8-
channel acquisition module and a Bluetooth (BT) transceiver to transmit the acquired data
to a remote platform. It was designed with the aimof creating a cheap and user-friendly system
that can be easily interfaced with the nowadays widely spread smartphones or tablets by means of a mobile-based application. The presented system, validated through in-vivo experiments, allows EEG signals recording at different sample rates and with a maximum
bandwidth of 524Hz. It was realized on a 19cm2 custom PCB with a maximum power consumption
of 270mW
Electronic systems for the restoration of the sense of touch in upper limb prosthetics
In the last few years, research on active prosthetics for upper limbs focused
on improving the human functionalities and the control. New methods have
been proposed for measuring the user muscle activity and translating it into
the prosthesis control commands. Developing the feed-forward interface so
that the prosthesis better follows the intention of the user is an important
step towards improving the quality of life of people with limb amputation.
However, prosthesis users can neither feel if something or someone is
touching them over the prosthesis and nor perceive the temperature or
roughness of objects. Prosthesis users are helped by looking at an object,
but they cannot detect anything otherwise. Their sight gives them most
information. Therefore, to foster the prosthesis embodiment and utility,
it is necessary to have a prosthetic system that not only responds to the
control signals provided by the user, but also transmits back to the user
the information about the current state of the prosthesis.
This thesis presents an electronic skin system to close the loop in prostheses
towards the restoration of the sense of touch in prosthesis users. The
proposed electronic skin system inlcudes an advanced distributed sensing
(electronic skin), a system for (i) signal conditioning, (ii) data acquisition,
and (iii) data processing, and a stimulation system. The idea is to integrate
all these components into a myoelectric prosthesis.
Embedding the electronic system and the sensing materials is a critical issue
on the way of development of new prostheses. In particular, processing
the data, originated from the electronic skin, into low- or high-level information
is the key issue to be addressed by the embedded electronic system.
Recently, it has been proved that the Machine Learning is a promising
approach in processing tactile sensors information. Many studies have
been shown the Machine Learning eectiveness in the classication of input
touch modalities.More specically, this thesis is focused on the stimulation system, allowing
the communication of a mechanical interaction from the electronic skin
to prosthesis users, and the dedicated implementation of algorithms for
processing tactile data originating from the electronic skin. On system
level, the thesis provides design of the experimental setup, experimental
protocol, and of algorithms to process tactile data. On architectural level,
the thesis proposes a design
ow for the implementation of digital circuits
for both FPGA and integrated circuits, and techniques for the power
management of embedded systems for Machine Learning algorithms
Remote Powering and Data Communication Over a Single Inductive Link for Implantable Medical Devices
RÉSUMÉ Les implants médicaux électroniques (Implantable Medical Devices - IMDs) sont notamment utilisés pour restaurer ou améliorer des fonctions perdues de certains organes. Ils sont capables de traiter des complications qui ne peuvent pas être guéries avec des médicaments ou par la chirurgie. Offrant des propriétés et des améliorations curatives sans précédent, les IMDs sont de plus en plus demandés par les médecins et les patients. En 2017, le marché mondial des IMD était évalué à 15,21 milliards de dollars. D’ici 2025, il devrait atteindre 30,42 mil-liards de dollars, soutenu par un taux de croissance annuel de 9,24% selon le nouveau rapport publié par Fior Markets. Cette expansion entraîne une augmentation des exigences pour as-surer des performances supérieures, des fonctionnalités supplémentaires et une durée de vie plus longue. Ces exigences ne peuvent être satisfaites qu’avec des techniques d’alimentation avancées, un débit de données élevé et une électronique miniaturisée robuste. Construire des systèmes capables de fournir toutes ces caractéristiques est l’objectif principal d’un grand nombre de chercheurs.
Parmi plusieurs technologies sans fil, le lien inductif, qui consiste en une paire de bobines à couplage magnétique, est la technique sans fil la plus largement utilisée pour le transfert de puissance et de données. Cela est dû à sa simplicité, sa sécurité et sa capacité à transmettre à la fois de la puissance et des données de façon bidirectionnelle.
Cependant, il existe encore un certain nombre de défis concernant la mise en œuvre d’un tel système de transfert d’énergie et de données sans fil (Wireless Power and Data Transfer - WPDT system). Un défi majeur est que les exigences pour une efficacité de transfert d’énergie élevée et pour une communication à haut débit sont contradictoires. En fait, la bande passante doit être élargie pour des débits de données élevés, mais réduite pour une transmission efficace de l’énergie. Un autre grand défi consiste à réaliser un démodulateur fonctionnant à haute vitesse avec une mise en œuvre simple et une consommation d’énergie ultra-faible.
Dans ce projet, nous proposons et expérimentons un nouveau système WPDT dédié aux IMD permettant une communication à haute vitesse et une alimentation efficace tout en maintenant une faible consommation d’énergie, une petite surface de silicium et une mise en œuvre simple du récepteur. Le système proposé est basé sur un nouveau schéma de modulation appelé "Carrier Width Modulation (CWM)", ainsi que sur des circuits de modulation et de démodulation inédits. La modulation consiste en un coupe-circuit synchronisé du réservoir LC primaire pendant un ou deux cycles en fonction des données transmises.----------ABSTRACT
Implantable Medical Devices (IMDs) are electronic implants notably used to restore or en-hance lost organ functions. They may treat complications that cannot be cured with medica-tion or through surgery. O˙ering unprecedented healing properties and enhancements, IMDs are increasingly requested by physicians and patients. In 2017, the worldwide IMD market was valued at USD 15,21 Billion. By 2025, it is expected to attain USD 30.42 Billion sus-tained by a compound annual growth rate of 9.24% according to a recent report published by Fior Markets. This expansion is bringing-up more demand for higher performance, additional features, and longer device lifespan and autonomy. These requirements can only be achieved with advanced power sources, high-data rates, and robust miniaturized electronics. Building systems able to provide all these characteristics is the main goal of many researchers.
Among several wireless technologies, the inductive link, which consists of a magnetically-coupled pair of coils, is the most widely used wireless technique for both power and data transfer. This is due to its simplicity, safety, and ability to provide simultaneously both power and bidirectional data transfer to the implant.
However there are still a number of challenges regarding the implementation of such Wireless Power and Data Transfer (WPDT) systems. One main challenge is that the requirements for high Power Transfer Eÿciency (PTE) and for high-data rate communication are contra-dictory. In fact, the bandwidth needs to be widened for high data rates, but narrowed for eÿcient power delivery. Another big challenge is to implement a high-speed demodulator with simple implementation and ultra-low power consumption.
In this project, we propose and experiment a new WPDT system dedicated to IMDs allow-ing high-speed communication and eÿcient power delivery, while maintaining a low power consumption, small silicon area, and simple implementation of the receiver. The proposed system is based on a new Carrier Width Modulation (CWM) scheme, as well as novel modu-lation and demodulation circuits. The modulation consists of a synchronized opening of the primary LC tank for one or two cycles according to the transmitted data. Unlike conventional modulation techniques, the data rate of the proposed CWM modulation is not limited by the quality factors of the primary and secondary coils. On the other hand, the proposed CWM demodulator allows higher-speed demodulation and simple implementation, unlike conven-tional demodulators for a similar modulation scheme. It also o˙ers a wide range of data rates under any selected frequency from 10 to 31 MHz
Electromyogram Interference Reduction In Neural Signal Recording Using Simple RC Compensation Circuits
Neuroprosthesis can partially restore lost motor functionalities of
individuals such as bladder voiding using functional electrical stimulation (FES)
techniques. FES involves applying pattern of electrical current pulses using
implanted electrodes to trigger affected nerves that are damaged due to
paralysis. A neural signal recorded using tripolar cuff electrodes is significantly
contaminated due to the presence of EMG interference from the surrounding
muscles. Conventional neural amplifiers are unable to remove such interferences
and modifications to the design are required. The modification to the design of
the Quasi-tripole (QT) amplifier is considered in this work to minimise the EMG
interferences from neural signal recording. The analogy between this modified
version of QT known as mQT and Wheatstone bridge claims to neutralise the
EMG interference by adding compensation circuit to either end of the outer
electrodes of the tripolar cuff and therefore balancing the bridge. In this work, we
present simple 3 and 2 stage RC compensation circuits to minimise EMG
interference in trying to balance the bridge in the neural frequency band of interest
(500-10kHz). It is shown that simple RC compensation circuit in series reduces
EMG interference only at the spot frequency rather than linearly in the entire
frequency band of interest. However, two and three stages RC ladder
compensation circuits mimicking electrode-electrolyte interface, can minimize the
EMG interference linearly in the entire frequency band of interest, without
requiring any readjustment to their components. The aim is to minimise EMG
interference as close to null as possible. Invitro testing of about 20% imbalanced
cuff electrode with proposed 3 and 2 stage RC ladder compensation circuits
resulted in linear EMG interference reduction atleast by a factor of 6. On an
average, this yielded an improvement of above 80% EMG minimisation, in
contrast to above 90% observed in the optimisation results, when 1Ω
transimpedance (EMG) was introduced into the setup. Further improvements to
the setup and design can give more promising results in reliable neural signal
recording for FES applications
A Low-Power DSP Architecture for a Fully Implantable Cochlear Implant System-on-a-Chip.
The National Science Foundation Wireless Integrated Microsystems (WIMS) Engineering Research Center at the University of Michigan developed Systems-on-a-Chip to achieve biomedical implant and environmental monitoring functionality in low-milliwatt power consumption and 1-2 cm3 volume. The focus of this work is implantable electronics for cochlear implants (CIs), surgically implanted devices that utilize existing nerve connections between the brain and inner-ear in cases where degradation of the sensory hair cells in the cochlea has occurred. In the absence of functioning hair cells, a CI processes sound information and stimulates the nderlying nerve cells with currents from implanted electrodes, enabling the patient to understand speech.
As the brain of the WIMS CI, the WIMS microcontroller unit (MCU) delivers the communication, signal processing, and storage capabilities required to satisfy the aggressive goals set forth. The 16-bit MCU implements a custom instruction set architecture focusing on power-efficient execution by providing separate data and address register windows, multi-word arithmetic, eight addressing modes, and interrupt and subroutine support. Along with 32KB of on-chip SRAM, a low-power 512-byte scratchpad memory is utilized by the WIMS custom compiler to obtain an average of 18% energy savings across benchmarks. A synthesizable dynamic frequency scaling circuit allows the chip to select a precision on-chip LC or ring oscillator, and perform clock scaling to minimize power dissipation; it provides glitch-free, software-controlled frequency shifting in 100ns, and dissipates only 480μW.
A highly flexible and expandable 16-channel Continuous Interleaved Sampling Digital Signal Processor (DSP) is included as an MCU peripheral component. Modes are included to process data, stimulate through electrodes, and allow experimental stimulation or processing. The entire WIMS MCU occupies 9.18mm2 and consumes only 1.79mW from 1.2V in DSP mode. This is the lowest reported consumption for a cochlear DSP.
Design methodologies were analyzed and a new top-down design flow is presented that encourages hardware and software co-design as well as cross-domain verification early in the design process. An O(n) technique for energy-per-instruction estimations both pre- and post-silicon is presented that achieves less than 4% error across benchmarks.
This dissertation advances low-power system design while providing an improvement in hearing recovery devices.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91488/1/emarsman_1.pd
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