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Biomedical Circuits and Systems, IEEE Transactions on

Issue 6 • Date Dec. 2009

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  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Biomedical Circuits and Systems publication information

    Page(s): C2
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  • Special Issue on Selected Papers from BiOCAS 2008 Guest Editors' Introduction

    Page(s): 361 - 362
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  • A Micropower Tilt-Processing Circuit

    Page(s): 363 - 369
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1358 KB) |  | HTML iconHTML  

    This paper describes a novel analog circuit for extracting the tilt angle from the output of a linear microelectromechanical-system accelerometer. The circuit uses the accelerometer signal, together with the gravitational acceleration vector, to generate the tilt signal. Using a current-mode representation with metal-oxide semiconductor devices operating in weak inversion, the appropriate trigonometric function has been realized to compute tilt. Furthermore, implementing a long-time constant filter to extract the mean tilt level provides adaptation to the static tilt level. Specifically, this circuit has been designed as part of an implantable vestibular prosthesis to provide inclination signals for bypassing dysfunctional otolith end organs. The circuit has been fabricated in AustriaMicroSystems 0.35-mum 2P4M complementary metal-oxide semiconductor technology, and this paper presents the theory, implementation, and measured results. View full abstract»

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  • Experimental Study of a TET System for Implantable Biomedical Devices

    Page(s): 370 - 378
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    Time-varying magnetic fields can be used to transfer power across the skin to drive implantable biomedical devices without the use of percutaneous wires. However, the main challenges of a transcutanoues energy transfer (TET) system are the temperature rise caused by power loss in the implanted circuitry and the changes in positioning between the external and internal coils due to fitting and changes in posture. This study presents a TET system with a closed-loop frequency-based power regulation method to deliver the right amount of power to the load under variable coil coupling conditions. After implanting a TET system into adult sheep, the temperature rise in the internal and external coils of a TET system was measured for power delivery in the range of 5 W to 15 W. The sheep was housed in a temperature controlled (16 plusmn1degC, humidity 50plusmn10%) room, in accordance with the standard protocols implemented at the University of Auckland for sheep studies. A power-loss analysis for the overall system was performed. The system was capable of regulating power for axially aligned separations of up to 16 mm. The maximum power efficiency of the overall system was 82.1% and a maximum temperature rise of 2.7degC was observed on the implanted secondary coil. View full abstract»

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  • NeuralWISP: A Wirelessly Powered Neural Interface With 1-m Range

    Page(s): 379 - 387
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    We present the NeuralWISP, a wireless neural interface operating from far-field radio-frequency RF energy. The NeuralWISP is compatible with commercial RF identification readers and operates at a range up to 1 m. It includes a custom low-noise, low-power amplifier integrated circuit for processing the neural signal and an analog spike detection circuit for reducing digital computational requirements and communications bandwidth. Our system monitors the neural signal and periodically transmits the spike density in a user-programmable time window. The entire system draws an average 20 muA from the harvested 1.8-V supply. View full abstract»

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  • Wireless Micropower Instrumentation for Multimodal Acquisition of Electrical and Chemical Neural Activity

    Page(s): 388 - 397
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    The intricate coupling between electrical and chemical activity in neural pathways of the central nervous system, and the implication of this coupling in neuropathologies, such as Parkinson's disease, motivates simultaneous monitoring of neurochemical and neuropotential signals. However, to date, neurochemical sensing has been lacking in integrated clinical instrumentation as well as in brain-computer interfaces (BCI). Here, we present an integrated system capable of continuous acquisition of data modalities in awake, behaving subjects. It features one channel each of a configurable neuropotential and a neurochemical acquisition system. The electrophysiological channel is comprised of a 40-dB gain, fully differential amplifier with tunable bandwidth from 140 Hz to 8.2 kHz. The amplifier offers input-referred noise below 2 muV rms for all bandwidth settings. The neurochemical module features a picoampere sensitivity potentiostat with a dynamic range spanning six decades from picoamperes to microamperes. Both systems have independent on-chip, configurable DeltaSigma analog-to-digital converters (ADCs) with programmable digital gain and resolution. The system was also interfaced to a wireless power harvesting and telemetry module capable of powering up the circuits, providing clocks for ADC operation, and telemetering out the data at up to 32 kb/s over 3.5 cm with a bit-error rate of less than 10-5. Characterization and experimental results from the electrophysiological and neurochemical modules as well as the full system are presented. View full abstract»

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  • Conveying Tactile Feedback in Sensorized Hand Neuroprostheses Using a Biofidelic Model of Mechanotransduction

    Page(s): 398 - 404
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (990 KB) |  | HTML iconHTML  

    One approach to conveying tactile feedback from sensorized neural prostheses is to characterize the neural signals that would normally be produced in an intact limb and reproduce them through electrical stimulation of the residual peripheral nerves. Toward this end, we have developed a model that accurately replicates the neural activity evoked by any dynamic stimulus in the three types of mechanoreceptive afferents that innervate the glabrous skin of the hand. The model takes as input the position of the stimulus as a function of time, along with its first (velocity), second (acceleration), and third (jerk) derivatives. This input is filtered and passed through an integrate-and-fire mechanism to generate a train of spikes as output. The major conclusion of this study is that the timing of individual spikes evoked in mechanoreceptive fibers innervating the hand can be accurately predicted by this model. We discuss how this model can be integrated in a sensorized prosthesis and show that the activity in a population of simulated afferents conveys information about the location, timing, and magnitude of contact between the hand and an object. View full abstract»

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  • A Wireless Integrated Circuit for 100-Channel Charge-Balanced Neural Stimulation

    Page(s): 405 - 414
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    The authors present the design of an integrated circuit for wireless neural stimulation, along with benchtop and in - vivo experimental results. The chip has the ability to drive 100 individual stimulation electrodes with constant-current pulses of varying amplitude, duration, interphasic delay, and repetition rate. The stimulation is performed by using a biphasic (cathodic and anodic) current source, injecting and retracting charge from the nervous system. Wireless communication and power are delivered over a 2.765-MHz inductive link. Only three off-chip components are needed to operate the stimulator: a 10-nF capacitor to aid in power-supply regulation, a small capacitor (< 100 pF) for tuning the coil to resonance, and a coil for power and command reception. The chip was fabricated in a commercially available 0.6- mum 2P3M BiCMOS process. The chip was able to activate motor fibers to produce muscle twitches via a Utah Slanted Electrode Array implanted in cat sciatic nerve, and to activate sensory fibers to recruit evoked potentials in somatosensory cortex. View full abstract»

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  • A Cantilever Sensor With an Integrated Optical Readout for Detection of Enzymatically Produced Homocysteine

    Page(s): 415 - 423
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    Microcantilever sensors have been recognized as a promising sensor platform for various chemical and biological applications. One of their major limitations is that the measurement of cantilever displacement typically involves elaborate off-chip setups with free-space optics. An improved device, known as the optical cantilever, has been proposed recently to eliminate the external optics. The response of the optical cantilever is measured on-chip through integrated waveguides. However, this method has been previously demonstrated only for devices operating in air, whereas most chemical and biological samples are in solution state. We present the first optical cantilever capable of operation in liquid. We test it with the detection of homocysteine with a minimal concentration of 10 muM. The minimal measurable cantilever displacement and surface stress are 5 nm and 1 mN/m, respectively. The presented device will be used in studies of a homocysteine-producing bacterial pathway for the purpose of drug discovery. It can also be extended to various other chemical- or biological-sensing applications by selecting an appropriate surface coating. View full abstract»

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  • Optoelectronic Tweezers as a Tool for Parallel Single-Cell Manipulation and Stimulation

    Page(s): 424 - 431
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    Optoelectronic tweezers (OET) is a promising approach for the parallel manipulation of single cells for a variety of biological applications. By combining the manipulation capabilities of OET with other relevant biological techniques (such as cell lysis and electroporation), one can realize a true parallel, single-cell diagnostic and stimulation tool. Here, we demonstrate the utility of the OET device by integrating it onto single-chip systems capable of performing in-situ, electrode-based electroporation/lysis, individual cell, light-induced lysis, and light-induced electroporation. View full abstract»

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  • A Low-Power Wide-Range I-V Converter for Amperometric Sensing Applications

    Page(s): 432 - 436
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    This paper presents for the first time experimental results of a current-to-voltage converter that can be used for amperometric sensing of currents ranging from 1 pA to 1 muA. The design strategy is optimized to achieve low power levels and, hence, make the circuit suitable for use in a wearable or implantable sensor. The power reduction is mostly achieved by combining transistors operating in the weak inversion region with floating-gate metal-oxide semiconductor devices and three different gain settings. The power consumption under normal operation is 9.82 muW. View full abstract»

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  • Low-Power Circuits for the Bidirectional Wireless Monitoring System of the Orthopedic Implants

    Page(s): 437 - 443
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    This paper proposes an architecture of the wireless monitoring system for the real-time monitoring of the orthopedic implants, which monitors the implant duty cycle, detects abnormal asymmetry, high amounts of force, and other conditions of the orthopedic implants. Data for diagnosis are communicated wirelessly by the radio-frequency (RF) signal between the embedded chip and the remote circuit. In different working modes, the system can be powered by the RF signal or stiff lead zirconate-titanate (PZT) ceramics which are able to convert mechanical energy inside the orthopedic implant into electrical energy. The power circuits with a variable ratio switched-capacitor (SC) dc-dc converter have been taped out with 0.35-mum complementary metal-oxide semiconductor (CMOS) technology. The test results show that the SC converter can transfer the input voltage that ranges from 5 V to 14 V from the PZT ceramics into the voltage ranging from 2 V to 2.5 V which will be dealt with by a low drop-out circuit in the future work. The total efficiency of the SC converter is from 28% to 42% at full-time working mode. The analog-to-digital converter (ADC) circuits have been fabricated in a 0.18-mum 1P6M CMOS process. The test results show that the ADC chip consumes only 12.5 muW in working mode and 150 nW in the sleep mode. The circuits, including RF circuits, ADC, and the microcontrol unit, have been implemented in a 0.18-mu m CMOS process. Future work includes some clinical experiments test in the application where PZT elements are used for power generation in total knee-replacement implants. View full abstract»

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  • A Silicon Cochlea With Active Coupling

    Page(s): 444 - 455
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    We present a mixed-signal very-large-scale-integrated chip that emulates nonlinear active cochlear signal processing. Modeling the cochlea's micromechanics, including outer hair cell (OHC) electromotility, this silicon (Si) cochlea features active coupling between neighboring basilar membrane (BM) segments-a first. Neighboring BM segments, each implemented as a class AB log-domain second-order section, exchange currents representing OHC forces. This novel active-coupling architecture overcomes the major shortcomings of existing cascade and parallel filter-bank architectures, while achieving the highest number of digital outputs in an Si cochlea to date. An active-coupling architecture Si cochlea with 360 frequency channels and 2160 pulse-stream outputs occupies 10.9 mm2 in a five-metal 1-poly 0.25-mum CMOS process. The chip's responses resemble that of a living cochlea's: Frequency responses become larger and more sharply tuned when active coupling is turned on. For instance, gain increases by 18 dB and Q 10 increases from 0.45 to 1.14. This enhancement decreases with increasing input intensity, realizing frequency-selective automatic gain control. Further work is required to improve performance by reducing large variations from tap to tap. View full abstract»

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  • ISCAS 2010 nono-bio circuit fabrics and systems

    Page(s): 456
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  • 2009 Index IEEE Transactions on Biomedical Circuits and Systems Vol. 3

    Page(s): 457 - 466
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  • Scitopia.org [advertisement]

    Page(s): 467
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  • IEEE Transactions on Biomedical Circuits and Systems Information for authors

    Page(s): 468
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  • IEEE Transactions on Biomedical Circuits and Systems society information

    Page(s): C3
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  • Blank page [back cover]

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Aims & Scope

IEEE Transactions on Biomedical Circuits and Systems (TBioCAS) publishes peer-reviewed manuscripts reporting original and transformative research at the intersection between the life sciences and circuits and systems engineering principles.

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Meet Our Editors

Editor-in-Chief
Gert Cauwenberghs
University of California at San Diego