Showing papers on "Electrode array published in 2009"

A MEMS-based flexible multichannel ECoG-electrode array.

Abstract: We present a micromachined 252-channel ECoG (electrocorticogram)-electrode array, which is made of a thin polyimide foil substrate enclosing sputtered platinum electrode sites and conductor paths. The array subtends an area of approximately 35 mm by 60 mm and is designed to cover large parts of a hemisphere of a macaque monkey’s cortex. Eight omnetics connectors are directly soldered to the foil. This leads to a compact assembly size which enables a chronic implantation of the array and allows free movements of the animal between the recording sessions. The electrode sites are 1 mm in diameter and were characterized by electrochemical impedance spectroscopy. At 1 kHz, the electrode impedances vary between

A large-scale, wireless electrochemical bipolar electrode microarray.

Abstract: We report a microelectrochemical array composed of 1000 individual bipolar electrodes that are controlled with just two driving electrodes and a simple power supply. The system is configured so that faradaic processes occurring at the cathode end of each electrode are correlated to light emission via electrogenerated chemiluminescence (ECL) at the anode end. This makes it possible to read out the state of each electrode simultaneously. The significant advance is that the electrode array is fabricated on a glass microscope slide and is operated in a simple electrochemical cell. This eliminates the need for microfluidic channels, provides a fabrication route to arbitrarily large electrode arrays, and will make it possible to place sensing chemistries onto each electrode using a robotic spotter.

256-Channel Neural Recording and Delta Compression Microsystem With 3D Electrodes

Abstract: A 3D microsystem for multi-site penetrating extracellular neural recording from the brain is presented. A 16 times 16-channel neural recording interface integrated prototype fabricated in 0.35 mum CMOS occupies 3.5 mm times 4.5 mm area. Each recording channel dissipates 15 muW of power with input-referred noise of 7 muVrms over 5 kHz bandwidth. A switched-capacitor delta read-out data compression circuit trades recording accuracy for the output data rate. An array of 1.5 mm platinum-coated microelectrodes is bonded directly onto the die. Results of in vitro experimental recordings from intact mouse hippocampus validate the circuit design and the on-chip electrode bonding technology.

Development and Implantation of a Minimally Invasive Wireless Subretinal Neurostimulator

Abstract: A wirelessly operated, minimally invasive retinal prosthesis was developed for preclinical chronic implantation studies in Yucatan minipig models. The implant conforms to the outer wall of the eye and drives a microfabricated polyimide stimulating electrode array with sputtered iridium oxide electrodes. This array is implanted in the subretinal space using a specially designed ab externo surgical technique that fixes the bulk of the prosthesis to the outer surface of the sclera. The implanted device is fabricated on a host polyimide flexible circuit. It consists of a 15-channel stimulator chip, secondary power and data receiving coils, and discrete power supply components. The completed device is encapsulated in poly(dimethylsiloxane) except for the reference/counter electrode and the thin electrode array. In vitro testing was performed to verify the performance of the system in biological saline using a custom RF transmitter circuit and primary coils. Stimulation patterns as well as pulse strength, duration, and frequency were programmed wirelessly using custom software and a graphical user interface. Wireless operation of the retinal implant has been verified both in vitro and in vivo in three pigs for more than seven months, the latter by measuring stimulus artifacts on the eye surface using contact lens electrodes.

Silicon-based nanoscale resistive device with adjustable resistance

Abstract: A non-volatile solid state resistive device that includes a first electrode, a p-type poly-silicon second electrode, and a non-crystalline silicon nanostructure electrically connected between the electrodes. The nanostructure has a resistance that is adjustable in response to a voltage being applied to the nanostructure via the electrodes. The nanostructure can be formed as a nanopillar embedded in an insulating layer located between the electrodes. The first electrode can be a silver or other electrically conductive metal electrode. A third (metal) electrode can be connected to the p-type poly- silicon second electrode at a location adjacent the nanostructure to permit connection of the two metal electrodes to other circuitry. The resistive device can be used as a unit memory cell of a digital non- volatile memory device to store one or more bits of digital data by varying its resistance between two or more values.

Wall-shaped electrodes for reducing the operation voltage of polymer-stabilized blue phase liquid crystal displays

Abstract: Polymer-stabilized blue phase liquid crystal displays based on the Kerr effect are emerging due to their submillisecond response time, wide view and simple fabrication process. However, the conventional in-plane switching device exhibits a relatively high operating voltage because the electric fields are restricted in the vicinity of the electrode surface. To overcome this technical barrier, we propose a partitioned wall-shaped electrode configuration so that the induced birefringence is uniform between electrodes throughout the entire cell gap. Consequently, the operating voltage is reduced by ~ 2.8× with two transistors. The responsible physical mechanisms are explained.

A flexural deformation sensing device and a user interface using the same

Abstract: A sensing device is provided for measuring flexural deformations of a surface. Such a sensing device may be used as a user interface in portable electronic devices. The sensing device comprises at least one cell. The cell comprises a first electrode, a central electrode, a second electrode, a first piezoelectric sensing layer placed between the first electrode and the central electrode, a second piezoelectric sensing layer placed between the central electrode and the second electrode, and a circuit connected to the first, second and the central electrodes. The circuit is configured to measure a first electrical signal between the first electrode and the central electrode, and a second electrical signal between the second electrode and the central electrode. At least one of the first electrical signal and the second electrical signal is responsive to an external stress applied on the sensing device.

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

Abstract: 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.

High-resolution three-dimensional extracellular recording of neuronal activity with microfabricated electrode arrays

Abstract: Microelectrode array recordings of neuronal activity present significant opportunities for studying the brain with single-cell and spike-time precision. However, challenges in device manufacturing constrain dense multisite recordings to two spatial dimensions, whereas access to the three-dimensional (3D) structure of many brain regions appears to remain a challenge. To overcome this limitation, we present two novel recording modalities of silicon-based devices aimed at establishing 3D functionality. First, we fabricated a dual-side electrode array by patterning recording sites on both the front and back of an implantable microstructure. We found that the majority of single-unit spikes could not be simultaneously detected from both sides, suggesting that in addition to providing higher spatial resolution measurements than that of single-side devices, dual-side arrays also lead to increased recording yield. Second, we obtained recordings along three principal directions with a multilayer array and demonstrated 3D spike source localization within the enclosed measurement space. The large-scale integration of such dual-side and multilayer arrays is expected to provide massively parallel recording capabilities in the brain.

Foldable, implantable electrode array assembly and tool for implanting same

Abstract: An electrode array assembly (28) with a frame that is foldable or bendable (32) on which electrodes (36) are disposed. The frame includes tabs (55) that are spaced from adjacent portions of the frame; the electrodes are disposed on the tabs.

Real-time volume imaging using a crossed electrode array

Abstract: This paper describes a unique crossed electrode array for real-time volume ultrasound imaging. By placing orthogonal linear array electrode patterns on the opposite sides of a hemispherically shaped composite transducer substrate, a 2D array can be fabricated using a small fraction of the elements required for a traditional 2D array. The performance of the array is investigated using a computer simulation of the radiation pattern. We show that by using a 288-element crossed electrode pattern it is possible to collect large field of view volume images (60deg times 60degsector) at real-time frame rates (>20 volume images/s), with image contrast and resolution comparable to what can be obtained using a conventional 128-element linear phased array.

Dielectric liquid microlens with well-shaped electrode.

Abstract: A dielectric liquid microlens with a well-shaped electrode is demonstrated. The bottom well-shaped electrode and the top planar electrode induce an inhomogeneous electric field when a voltage is applied, which causes the focal length to change. Adaptive microlenses and microlens arrays with well-shaped electrode are fabricated and their performance is evaluated. The bi-convex structure introduces a larger optical power. Compared with common planar-electrodes liquid lenses, this well-shaped electrode not only inhibits drifting of the liquid but also reduces the operating voltage.

Spread of Excitation Measurements for the Detection of Electrode Array Foldovers : A Prospective Study Comparing 3-Dimensional Rotational X-ray and Intraoperative Spread of Excitation Measurements

Abstract: Objective: The optimal positioning of electrode arrays in the cochlea is extremely important. Our standard approach is to use a 3-dimensional rotational x-ray for the intraoperative determination of the position of the electrode array. We wanted to see if spread of excitation (SOE) is useful for determining the electrode array position within the cochlea. Study Design: Prospective blind study design. Setting: Tertiary University Referral Center (Cochlear Implantation Center Amsterdam-Academic Medical Center, University of Amsterdam). Patients: Seventy-two implanted ears with a Cochlear Freedom device. Intervention: After cochlear implantation, we compared the 3-dimensional rotational x-ray imaging and SOE measurements. The investigators were blinded for the intraoperative surgeon findings and also for the imaging findings. Outcome Measure(s): Electrode array foldovers within the cochlea and the reliability of the SOE measurements. Results: We placed implants in 72 ears in this study, and all procedures seemed to be surgically uneventful. To our surprise, we discovered 4 electrode foldovers in this group. Of the 4 foldovers, 3 were corrected intraoperatively. Conclusion: We found that intraoperative imaging and/or electrophysiologic measurements such as the SOE provide very useful information regarding electrode position within the cochlea. Spread of excitation is effective in detecting electrode array foldovers if the audiologist is experienced. Some software modifications are suggested.

Radial electrode array

Abstract: A sensor array apparatus for monitoring medical signals includes a first flexible substrate defining a central focal point and a second flexible substrate associated with the central focal point. A plurality of medical electrodes are disposed on the periphery of the first flexible substrate and a reference electrode is disposed on the second flexible substrate. A connector is in electrical communication with the medical electrodes and the reference electrode and adapted to connect to an electronic system. Bio-electric information is monitored between one of the medical electrodes and the reference electrode.

Brain-computer interfaces: an overview of the hardware to record neural signals from the cortex.

Abstract: Brain–computer interfaces (BCIs) record neural signals from cortical origin with the objective to control a user interface for communication purposes, a robotic artifact or artificial limb as actuator. One of the key components of such a neuroprosthetic system is the neuro–technical interface itself, the electrode array. In this chapter, different designs and manufacturing techniques will be compared and assessed with respect to scaling and assembling limitations. The overview includes electroencephalogram (EEG) electrodes and epicortical brain–machine interfaces to record local field potentials (LFPs) from the surface of the cortex as well as intracortical needle electrodes that are intended to record single-unit activity. Two exemplary complementary technologies for micromachining of polyimide-based arrays and laser manufacturing of silicone rubber are presented and discussed with respect to spatial resolution, scaling limitations, and system properties. Advanced silicon micromachining technologies have led to highly sophisticated intracortical electrode arrays for fundamental neuroscientific applications. In this chapter, major approaches from the USA and Europe will be introduced and compared concerning complexity, modularity, and reliability. An assessment of the different technological solutions comparable to a strength weaknesses opportunities, and threats (SWOT) analysis might serve as guidance to select the adequate electrode array configuration for each control paradigm and strategy to realize robust, fast, and reliable BCIs.

Real-Time Volume Imaging Using a Crossed Electrode Array

Abstract: This paper describes a unique crossed electrode array for real-time volume ultrasound imaging. By placing orthogonal linear array electrode patterns on the opposite sides of a hemispherically shaped composite transducer substrate, a 2-D array can be fabricated using a small fraction of the elements required for a traditional 2-D array. The performance of the array is investigated using a computer simulation of the radiation pattern. We show that by using a 288-element crossed electrode pattern it is possible to collect large field of view volume images (60° x 60° sector) at real-time frame rates (>20 volume images/s), with image contrast and resolution comparable to what can be obtained using a conventional 128-element linear phased array.

Ultrafast micropumping by biased alternating current electrokinetics

Abstract: This paper reports dramatic improvements in flow rate over conventional alternating current (ac) electrokinetic micropumps by exploiting asymmetry in electric potentials over the electrodes. A micropump consisting of a planar asymmetric electrode array was tested using ac signals with and without a direct current (dc) bias. All experiments were done at 100 kHz Vac. The pumping velocity is much faster with a dc voltage, in some cases by an order of magnitude, reaching a linear velocity of up to 2.5 mm/s with only 5.4 Vrms. The discovery presents an exciting opportunity for microfluidics. Future improvement can be anticipated with additional optimization.

System and method for maintaining a distribution of currents in an electrode array using independent voltage sources

Abstract: In one technique, a desired electrical current distribution on at least three active electrodes is selected. An electrical energy perturbation is generated on at least one electrode. A current-to-voltage relationship at each active electrode is estimated based on the energy perturbation. The current-to-voltage relationship for each active electrode takes into account current flow through other active electrodes. The voltage distribution necessary to achieve the desired current distribution is determined based on the estimated current-to-voltage relationship. Voltage-regulated energy is conveyed between the electrodes and tissue in accordance with the determined electrical voltage distribution. In another technique, an electrical energy perturbation on at least one of the electrodes is generated. Network resistances for each of at least three active electrodes are computed in response to the energy perturbation. The network resistances represent the resistances between the electrodes and common node to which the electrodes are connected.

Simultaneous and non-simultaneous dual electrode stimulation in cochlear implants: evidence for two neural response modalities

Abstract: Conclusion: There are two modalities of dual electrode stimulation: a shifting, continuous excitation, which is the desired effect, and a split excitation with considerable variation in loudness. The first one most likely occurs in the basal turn, with adjacent contacts, stimulated simultaneously rather than sequentially. Objectives: This study examines the effects on place pitch and loudness of simultaneous current steering and sequential stimulation. These can give cochlear implant patients access to more perceptual channels than physical contacts in the electrode array. Materials and methods: For both lateral wall and perimodiolar electrodes, simultaneous current steering as well as sequential stimulation, place pitch and loudness of the percept were predicted with a computational model of the implanted human cochlea. The loudness predictions were validated with psychophysical loudness balancing experiments. Results: Simultaneous stimulation with adjacent electrode contacts in the basal end of the coch...

Shaping Nanoelectrodes for High-Precision Dielectrophoretic Assembly of Carbon Nanotubes

Abstract: To achieve high-precision dielectrophoretic (DEP) assembly of carbon nanotubes (CNTs) for nanoelectronic circuits and nanoelectromechanical systems (NEMS), a technique is investigated both theoretically and experimentally for shaping the local geometries of nanoelectrodes to control the electrohydrodynamic behavior of CNTs. Motion trajectories and positions of CNTs assembled on electrodes are predicted based on calculated DEP forces and torques. Both simulation and experimental results show that the geometries of two opposing electrodes significantly affect the precision and robustness with which CNTs can be deposited. Experimental investigation of an electrode array demonstrates that the spacing between neighboring electrode pairs should be larger than twice the width of electrodes to avoid overlapping electric fields and unstable DEP forces; otherwise, unequally distributed electric fields and DEP forces induce a significant number of assembly failures in the array.

Electrode array detector for microchip capillary electrophoresis

Abstract: Selectivity and resolution for analyses conducted using microfluidic devices can be improved by increasing the total number of individual detection elements in the device. Here, a poly(dimethylsiloxane) capillary electrophoresis microchip was fabricated with an integrated electrode array for selective detection of small molecules. Eight individually addressable gold electrodes were incorporated in series after a palladium current decoupler in the separation channel of an electrophoresis microchip. The electrode array device was characterized using a mixture of biologically relevant analytes and xenobiotics: norepinephrine, 4-aminophenol, acetaminophen, uric acid, and 3,4-dihydroxyphenylacetic acid. Separation efficiencies as high as 9000 ± 1000 plates (n = 3) for 3,4-dihydroxyphenylacetic acid and limits of detection as low as 2.6 ± 1.2 µM (n = 3) for norepinephrine were obtained using this device. After characterizing the performance of the device, potential step detection was conducted at the array electrodes and selective detection achieved based upon differences in redox potentials for individual analytes. Utilization of potential step detection was particularly advantageous for resolving co-migrating species; resolution of 3,4-dihydroxy-L-phenylalanine from acetaminophen using potential control was demonstrated. Finally, a human urine sample was analyzed using potential step detection to demonstrate the applicability of this device for complex sample analysis.

Universal electrode array for monitoring brain activity

Abstract: Methods of monitoring brain activity signals in a patient are described, including the steps of identifying a lobe or lobes of the patient's brain in which the patient's seizures originate; selecting an electrode array from a plurality of predetermined dispersed electrode patterns based on the identified lobe or lobes of the brain; implanting the electrode array within the patient's cranium to place the electrodes in contact with the identified lobe or lobes of the brain; and coupling the electrodes to an seizure advisory system. Also described is a seizure advisory system that includes an electrode array having fewer than 32 electrodes in a predetermined dispersed radial pattern, adapted to be implanted through a single opening in the skull, and to be deployed in the predetermined dispersed radial pattern to detect a brain activity signal. The system also includes a communication assembly and an external assembly.

Imaging of electrode position in relation to electrode functioning after cochlear implantation

Abstract: This study assessed the electrode position in cochlear implant patients and evaluated the extent to which the electrode position is determinative in the electrophysiological functioning of the cochlear implant system. Five consecutively implanted adult patients received a multichannel cochlear implant. In all patients, the electrical impedance and the electrically evoked compound action potentials were recorded immediately after implantation. Multislice computer tomography was performed 6 weeks postoperatively before switch-on of the cochlear implant. The electrode position relative to the modiolus was assessed and correlated to the electrophysiological measurements. All electrodes were fully inserted; this was confirmed by computer tomography. The individual electrode distance toward the modiolus could be most precisely analyzed for the basal part of the electrode array. It was thus decided to study the data of electrodes one, four, and seven. No correlation was found between electrical impedance and electrode distance. A significant correlation was found between electrode distance and the electrically evoked compound action potentials, with a 96% probability using Kendall’s rank correlation. We conclude that the electrode–modiolus distance is of importance to the stimulation of auditory nerve fibers. Future developments in imaging will further improve and refine our insight in the relation between electrode positioning.

Optically hidden electromagnetic source for generation of spatially non uniform magnetic field and tunable devices made thereof

Abstract: An electromagnetic source has an electrode structure coupled to a substrate. The electrode structure has interspaced electrodes, at least one of which is spiral-shaped. At least one electrical contact interconnects the electrodes of the electrode structure. The electrode structure is responsive to an applied electrical current to generate a spatially non-uniform magnetic field. This field can act on a LC layer such that optical properties of the layer are controllable.

Thin film transistor, active matrix substrate, and image pickup device

Abstract: A thin film transistor including: source and drain electrodes, an active layer that contacts the source and drain electrodes and contains an oxide semiconductor, a gate electrode that controls current flowing between the source and drain electrodes via the active layer, a first insulating film that separates the gate electrode from the source and drain electrodes and the active layer, a bias electrode that is arranged at the opposite side of the active layer from the gate electrode, and has an electric potential fixed independently from the gate electrode, and a second insulating film that separates the bias electrode from the source and drain electrodes and the active layer.