Showing papers on "Electrode array published in 2010"

Electrode array having a rail system and methods of manufacturing the same

Abstract: A device for brain stimulation includes a lead having a longitudinal surface and a distal end. The lead includes a longitudinal rail disposed within the distal end of the lead. The longitudinal rail includes at least two prongs, each prong being configured and arranged to receive at least one segmented electrode. The lead further includes a plurality of segmented electrodes disposed along the longitudinal surface of the lead near the distal end of the lead. Each of the plurality of segmented electrodes is coupled to one of the at least two prongs of the rail.

Development of piezoelectric acoustic sensor with frequency selectivity for artificial cochlea

Abstract: In this paper, we report a novel piezoelectric artificial cochlea which realizes both acoustic/electric conversion and frequency selectivity without an external energy supply. The device comprises an artificial basilar membrane (ABM) which is made of a 40 μm thick polyvinylidine difluoride (PVDF) membrane fixed on a substrate with a trapezoidal slit. The ABM over the slit, which mimics the biological system, is vibrated by acoustic waves and generates electric output due to the piezoelectric effect of PVDF. The width of ABM is linearly varied from 2.0 to 4.0 mm along the longitudinal direction of 30 mm to change its local resonant frequency with respect to the position. A detecting electrode array with 24-elements of 0.50 × 1.0 mm rectangles is made of an aluminum thin film on ABM, where they are located in a center line of longitudinal direction with the gaps of 0.50 mm. Since the device will be implanted into a cochlea filled with lymph fluid in future, the basic characteristics in terms of vibration and acoustic/electric conversion are investigated both in the air and in the silicone oil which is a model of lymph fluid. The in vitro optical measurements show that the local resonant frequency of vibration is varied along the longitudinal direction from 6.6 to 19.8 kHz in the air and from 1.4 to 4.9 kHz in the silicone oil, respectively. Since a resonating place vibrates with relatively large amplitude, the electric output there becomes high and that at the other electrodes remains to be low. Thus, the electric voltages from each electrode realize the frequency selectivity. Furthermore, the effect of surrounding fluid on the vibration is discussed in detail by comparing the experimental results with the theoretical predictions obtained by the Wentzel–Kramers–Brillouin asymptotic method. The theoretical prediction indicates that the surrounding fluid of the higher density induces the larger effective mass for the vibration that results in lower resonant frequency. From these findings, the feasibility of artificial cochlea is confirmed both experimentally and theoretically.

Wafer-scale fabrication of penetrating neural microelectrode arrays

Abstract: The success achieved with implantable neural interfaces has motivated the development of novel architectures of electrode arrays and the improvement of device performance. The Utah electrode array (UEA) is one example of such a device. The unique architecture of the UEA enables single-unit recording with high spatial and temporal resolution. Although the UEA has been commercialized and been used extensively in neuroscience and clinical research, the current processes used to fabricate UEA’s impose limitations in the tolerances of the electrode array geometry. Further, existing fabrication costs have led to the need to develop less costly but higher precision batch fabrication processes. This paper presents a wafer-scale fabrication method for the UEA that enables both lower costs and faster production. More importantly, the wafer-scale fabrication significantly improves the quality and tolerances of the electrode array and allow better controllability in the electrode geometry. A comparison between the geometrical and electrical characteristics of the wafer-scale and conventional array-scale processed UEA’s is presented.

Evaluation of stimulus parameters and electrode geometry for an effective suprachoroidal retinal prosthesis.

Abstract: Several approaches have been proposed for placement of retinal prostheses: epiretinal, subretinal and suprachoroidal. We aimed to systematically evaluate the effectiveness of varying a range of stimulus parameters and electrode geometry for a suprachoroidal electrode array, using cortical evoked responses to monopolar electrical stimulation in cats. Our results indicate that charge thresholds were not dependent on electrode size, pulse widths or position of the return electrode tested, but were dependent on the number of sites stimulated in parallel. Further, we found that the combination of monopolar stimulation with large diameter electrodes, wide pulse widths and parallel stimulation minimized the voltage requirements for stimulation. These results provide useful insights for the design specifications of a low voltage suprachoroidal stimulator.

Immobilizing enzymes onto electrode arrays by hydrogel photolithography to fabricate multi-analyte electrochemical biosensors

Abstract: This paper describes a biomaterial microfabrication approach for interfacing functional biomolecules (enzymes) with electrode arrays. Poly (ethylene glycol) (PEG) hydrogel photopatterning was employed to integrate gold electrode arrays with the enzymes glucose oxidase (GOX) and lactate oxidase (LOX). In this process, PEG diacrylate (DA)-based prepolymer containing enzyme molecules as well as redox species (vinylferrocene) was spin-coated, registered, and UV cross-linked on top of an array of gold electrodes. As a result, enzyme-carrying circular hydrogel structures (600 μm diameter) were fabricated on top of 300 μm diameter gold electrodes. Importantly, when used with multiple masks, hydrogel photolithography allowed us to immobilize GOX and LOX molecules on adjacent electrodes within the same electrode array. Cyclic voltammetry and amperometry were used to characterize biosensor electrode arrays. The response of the biosensor array was linear for up to 20 mM glucose with sensitivity of 0.9 μA cm−2 mM−1 a...

Predicting the movements of permanently installed electrodes on an active landslide using time‐lapse geoelectrical resistivity data only

Abstract: If electrodes move during geoelectrical resistivity monitoring and their new positions are not incorporated in the inversion, then the resulting tomographic images exhibit artefacts that can obscure genuine time-lapse resistivity changes in the subsurface. The effects of electrode movements on time-lapse resistivity tomography are investigated using a simple analytical model and real data. The correspondence between the model and the data is sufficiently good to be able to predict the effects of electrode movements with reasonable accuracy. For the linear electrode arrays and 2D inversions under consideration, the data are much more sensitive to longitudinal than transverse or vertical movements. Consequently the model can be used to invert the longitudinal offsets of the electrodes from their known baseline positions using only the time-lapse ratios of the apparent resistivity data. The example datasets are taken from a permanently installed electrode array on an active lobe of a landslide. Using two sets with different levels of noise and subsurface resistivity changes, it is found that the electrode positions can be recovered to an accuracy of 4 % of the baseline electrode spacing. This is sufficient to correct the artefacts in the resistivity images, and provides for the possibility of monitoring the movement of the landslide and its internal hydraulic processes simultaneously using electrical resistivity tomography only.

The relationship between electrically evoked compound action potential and speech perception: a study in cochlear implant users with short electrode array.

Abstract: OBJECTIVES To determine the extent to which electrically evoked compound action potential (ECAP) measurements were related with speech perception performance in implant users with a short electrode array and to investigate the relationship between ECAP measures and performance according to specific devices. DESIGN Prospective study. SETTING Tertiary referral center. PATIENTS Seventeen Hybrid cochlear implant users were tested in this study. Subjects were divided into 2 groups: 8 using the Nucleus Hybrid M and 9 using the Nucleus Hybrid RE. In addition, 21 Nucleus Freedom long electrode implant (CI24RE) users also were tested to compare with the results of the old device (CI24M). MAIN OUTCOME MEASURES ECAP growth functions were recorded using either an interphase gap (IPG) of 8 or 45 mus. We then calculated the slope of the growth function and changes in sensitivity with IPG. For each subject, these measures were compared with performance on tests of word recognition. RESULTS The changes in sensitivity using 2 IPGs showed no correlation with the results of word recognition test in Hybrid cochlear implant users. In contrast, relatively strong correlations have been found between the slope of ECAP growth functions and performance on word recognition test. Additionally, when we separate the results of Hybrid M and RE, the slopes of ECAP growth functions from only Hybrid RE CI recipients were significantly correlated with speech performance. The slopes of ECAP growth function in CI24RE users with long electrode also were significantly correlated with performance. However, comparing between 2 independent correlations in RE devices, correlation was higher in Hybrid RE group. CONCLUSION The results presented in this article support the view that slope of the ECAP growth can show significant correlation to performance with a cochlear implant. Furthermore, these results suggest that the strength of the correlation may be related to the specific device. These results suggest that ECAP measures may be useful in developing a test to predict outcomes with the implant.

Driving characteristics of the electrowetting-on-dielectric device using atomic-layer-deposited aluminum oxide as the dielectric

Abstract: Electrowetting on dielectric (EWOD) is useful in manipulating droplets for digital (droplet-based) microfluidics, but its high driving voltage over several tens of volts has been a barrier to overcome. This article presents the characteristics of EWOD device with aluminum oxide (Al2O3, e r ≈ 10) deposited by atomic layer deposition (ALD), for the first time as the high-k dielectric for lowering the EWOD driving voltage substantially. The EWOD device of the single-plate configuration was fabricated by several steps for the control electrode array of 1 mm × 1 mm squares with 50 μm space, the dielectric layer of 1,270 A thick ALD Al2O3, the reference electrode of 20 μm wide line electrode, and the hydrophobic surface treatment by Teflon-AF coating, respectively. We observed the movement of a 2 μl water droplet in an air environment, applying a voltage between one of the control electrodes and the reference electrode in contact with the droplet. The droplet velocity exponentially depending on the applied voltage below 15 V was obtained. The measured threshold voltage to move the droplet was as low as 3 V which is the lowest voltage reported so far in the EWOD researches. This result opens a possibility of manipulating droplets, without any surfactant or oil treatment, at only a few volts by EWOD using ALD Al2O3 as the dielectric.

Touch sensor, display and electronic device

Abstract: A capacitive type touch sensor appropriately detecting an object, and a display and an electronic device including such a touch sensor are provided. The display including a drive electrode receiving a drive signal, a detection electrode located adjacent to the drive electrode, and a dielectric material located between the drive electrode and the detection electrode defining a capacitive area. The detection electrode generates an output signal driven by the drive signal, a detection circuit electrically connected to the detection electrode sensing the output signal. A switch element is electrically connected between the detection electrode and a voltage source providing a predefined voltage level and having a first state and a second state. A display control circuit controls a voltage applied between a display common voltage electrode and a pixel electrode to display an image based on an image signal, and the display common voltage electrode serves as the drive electrode.

Electrode features for hearing preservation and drug delivery strategies.

Abstract: Background/Aims: Reducing the risk of hearing loss after cochlear implantation requires optimization of the electrode array to minimize the physical trauma caused by insertion and placement. Furthermore, the electrode design must be optimized for atraumatic surgical approaches. Even greater levels of protection may be achieved by the use of a drug during and after implantation. The electrode array offers a potential vehicle for drug delivery. Methods: This article reviews the laboratory and clinical data available thus far relating to the importance of electrode design parameters for trauma minimization, and the possibility of further reduction through pharmaceutical intervention. Candidate drugs were identified through literature review and laboratory evaluation. The most promising have been investigated in vitro and in animal models of implantation trauma. Three delivery devices are currently under development to satisfy the specific demands of different therapy regimes. The delivery profiles of each were evaluated through both modelling and bench testing and the concepts investigated in vitro and in vivo. Results: Current evidence favours a thin, flexible electrode array with wires in a zigzag shape. Steroids and an apoptosis inhibitor (AM111) performed well in animal models of electrode trauma and are both good drug candidates for reduction of the risk of hearing loss after implantation. Semi-chronic dexamethasone elution, acute drug delivery by intracochlear catheter, and longer-term delivery through diffusion from a reservoir were all shown to be feasible. Conclusion: An extensive programme focussed on minimizing hearing loss through device optimization and the development of new technologies has yielded positive results and new concepts for further development and clinical application.

Neural interface system

Abstract: The neural interface system of the preferred embodiments includes an electrode array having a plurality of electrode sites and a carrier that supports the electrode array. The electrode array is coupled to the carrier such that the electrode sites are arranged both circumferentially around the carrier and axially along the carrier. A group of the electrode sites may be simultaneously activated to create an activation pattern. The system of the preferred embodiment is preferably designed for deep brain stimulation, and, more specifically, for deep brain stimulation with fine electrode site positioning, selectivity, tunability, and precise activation patterning. The system of the preferred embodiments, however, may be alternatively used in any suitable environment (such as the spinal cord, peripheral nerve, muscle, or any other suitable anatomical location) and for any suitable reason.

A Wafer-Scale Etching Technique for High Aspect Ratio Implantable MEMS Structures.

Abstract: Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah electrode array (UEA), intended for recording and stimulating neural tissue. Fabrication of the UEA is primarily based on the use of dicing and wet etching to achieve high aspect ratio (15:1) penetrating electrodes. An important step in the array fabrication is the etching of electrodes to produce needle-shape electrodes with sharp tips. Traditional etching processes are performed on a single array, and the etching conditions are not optimized. As a result, the process leads to variable geometries of electrodes within an array. Furthermore, the process is not only time consuming but also labor-intensive. This report presents a wafer-scale etching method for the UEA. The method offers several advantages, such as substantial reduction in the processing time, higher throughput and lower cost. More importantly, the method increases the geometrical uniformity from electrode to electrode within an array (1.5 ± 0.5 % non-uniformity), and from array to array within a wafer (2 ± 0.3 % non-uniformity). Also, the etching rate of silicon columns, produced by dicing, are studied as a function of temperature, etching time and stirring rate in a nitric acid rich HF-HNO(3) solution. These parameters were found to be related to the etching rates over the ranges studied and more-importantly affect the uniformity of the etched silicon columns. An optimum etching condition was established to achieve uniform shape electrode arrays on wafer-scale.

Systems and methods for flexible electrodes

Abstract: Disclosed herein are systems and methods for producing and using electrodes, which may be flexible and/or stretchable, and interconnection structures that can be used both externally and/or implanted within the body Electrodes according to various embodiments disclosed herein may be produced by depositing patterned layers of insulating and conductive polymers to form multi-layer circuits The conductive materials and layers in the structure can be exposed on the surface of the structures for use as electrodes A plurality of electrodes may be formed into an electrode array In various embodiments, electrode arrays may be associated with telemetry modules configured to wirelessly transmit data collected by the electrode array to a receiver module

Force of cochlear implant electrode insertion performed by a robotic insertion tool: comparison of traditional versus Advance Off-Stylet techniques.

Abstract: Objective—Robotic cochlear implant electrode array insertion offers substantial potential advantages, namely repeatability and minimization of insertion forces leading to decreased intracochlear trauma. Using such a robotic insertion tool, we sought to analyze force profiles during deployment of stylet-containing electrode arrays using either traditional insertion, in which the stylet is withdrawn after complete insertion of the electrode, or Advance Off-Stylet (AOS) insertion, in which the stylet is withdrawn simultaneous with electrode array insertion. Study design—Prospective. Setting—Tertiary referral center. Intervention(s)—A robotic cochlear implant insertion tool coupled with a force sensing carriage was used to perform electrode array insertions into an anatomically-correct, 3-dimensional scala tympani model during either straight insertion (n=4) or AOS insertion (n=4). Main outcome measure(s)—Both insertion techniques begin with a 7mm straight insertion during which forces were similar averaging approximately 0.006N. For insertion from 7–17mm, traditional insertion forces averaged 0.046 ± 0.027N with a peak of 0.093N and AOS insertion

Fabrication and characterization of solid mercury amalgam electrodes for protein analysis.

Abstract: Gold and carbon electrodes have been largely used as transducers in protein and DNA sensors and arrays. Liquid mercury electrodes, with potential windows allowing detection of DNA and protein reduction processes at highly negative potentials, were considered as useless in such arrays. Here, we show that solid amalgam electrode (SAE) arrays can be prepared as a substitution of liquid mercury in the analysis of the above biomacromolecules. Vacuum metal sputtering on a glass substrate, photolithography, and galvanic mercury amalgam formation were used for fabrication of an inexpensive disposable electrode array. The resulting ultrathin (less than 1 μm) amalgam microelectrodes were characterized with respect to influence of the electrode composition and size on the reproducibility and stability of electrochemical signals. Further characterization was performed using electron microscopy and the well-established ruthenium electrochemistry. Final, optimized, design was applied in protein analysis employing the r...

Sensor electrode array, usage of sensor electrode array, and electrostatic capacity type touch panel

Abstract: PROBLEM TO BE SOLVED: To provide a touch panel that is manufactured by using a thin metallic wire electrode that is stable under environmental variation such as high temperature and humidity, maintains good responsiveness in a large area, and allows multi-touch operation.SOLUTION: An electrostatic capacity type touch panel includes a first sensor electrode array and a second sensor electrode array, which are arranged in an orthogonal array. The first sensor electrode array disposed on a user's side is formed by patterning conductive metal thin wire on a flexible transparent substrate having an easy adhesion layer.

Programming techniques for stimulation with utilization of case electrode

Abstract: This disclosure describes techniques that support delivering electrical stimulation via an electrode on a housing of an implantable medical device (IMD) while substantially simultaneously delivering electrical stimulation via one or more electrodes, having the same polarity as the electrode on the housing, on one or more leads engaged to the IMD. The stimulation may be constant current-based or constant voltage-based stimulation in the form of pulses or continuous waveforms. Delivery of stimulation via both a housing anode and one or more lead anodes, for example, may allow a user to control current paths between the housing electrode and the lead electrode(s) in a relative manner to achieve different electric or stimulation field shapes.

A new cochlear implant electrode design for preservation of residual hearing: a temporal bone study.

Abstract: Conclusions: Success in conservation of residual hearing after cochlear implantation has benefited patients with high levels of residual low frequency hearing who were not previously considered for conventional cochlear implantation. Technological developments play a key role in minimizing trauma to the cochlea during placement of electrodes. Objectives: The Nucleus® Straight Research Array (SRA) has been designed and developed as a collaboration project between our centre and Cochlear Ltd with the objective of minimizing trauma to the cochlea with insertion of the electrode via the round window. Methods: We studied 22 fresh or thawed fresh-frozen human temporal bones implanted by one otosurgeon with the SRA electrode with a standard round window technique used for cochlear implantation. An additional four temporal bones were implanted with a ‘Standard’ straight electrode using the same surgical technique. All insertions were performed in the scala tympani of the cochlea. Results: Evaluation of insertion ...

Electro-thermotherapy of tissue using penetrating microelectrode array

Abstract: Electrosurgical therapy is provided with an electrode array configured to ablate tissue during insertion of the electrode array into tissue being treated. Once the electrode array is fully inserted, deep heating of the treated tissue can be performed by applying an additional waveform to the tissue with the electrode array. Optionally, the electrical waveform can be varied continuously during insertion of the electrode array to control the extent of coagulation at the side walls and at the bottom of the channels produced by tissue ablation.

Pixel circuit of a flat panel display device and method of driving the same

Abstract: A pixel circuit of a flat panel display device and a method for driving thereof are provided. The pixel circuit includes a first transistor having a first gate electrode coupled to a scan line, a second electrode coupled to a data line, a second gate electrode coupled to a controlling signal line, and a first electrode, a second transistor having a first gate electrode coupled to the first electrode of the first transistor, a second electrode coupled to a first voltage source, a second gate electrode coupled to the controlling signal line, and a first electrode, a capacitor coupled between the first gate electrode of the second transistor and the first electrode of the second transistor, and an organic light emitting diode coupled between the first electrode of the second transistor and a second voltage source, in which the threshold voltage of the first and second transistors may be controlled to the required level by supplying a controlling signal of a fixed voltage level to the second gate electrodes of the first and second transistors through the controlling signal line.

Lithium-ion cell with an array of reference electrodes

Abstract: A cluster or array of reference electrode materials is prepared and used to monitor the state of charge of positive and negative active electrode materials of a lithium-ion cell. The reference electrode materials are composed so as to provide useful electrochemical potential values when placed in the same electrolyte in proximity with a positive or negative electrode. The array of reference electrodes includes at least two electrically discrete instances of reference electrode materials. Such duplication of reference material in the array permits confirmation of the present quality and activity of a reference material used for evaluation of positive and/or negative electrode material in a lithium-ion cell.

Sensor device and method for grip and proximity detection

Abstract: An electrical hand-held device is provided with improved proximity detection, which can be placed on a surface and has at least one transmission electrode, at least one reception electrode and at least one compensation electrode arranged between transmission electrode and reception electrode. The transmission electrode and the compensation electrode can be supplied with an electric switching signal of predetermined signal frequency and predetermined signal amplitude. Switching electric signal at the compensation electrode is phase-delayed with respect to the switching electric signal at the transmission electrode. Alternating electric fields radiated at the transmission electrode and the compensation electrode generate a current in the reception electrode, which is representative of an approach of a hand to the hand-held device. The transmission electrode and the reception electrode are arranged in such a way, that the impedance between the transmission electrode and the reception electrode exceeds a predetermined value, which is suitable to keep the current generated in the reception electrode under a predetermined value.

Electrochemical test strip, electrochemical test system, and measurement method using the same

Abstract: An electrochemical test strip, an electrochemical test system, and a measurement method using the same are provided. The electrochemical test strip includes an insulating substrate, an electrode system formed on the insulating substrate, and an insulating layer formed on the electrode system. The electrode system includes a set of measurement electrodes, a set of identifying electrodes, and a resistive path having a predetermined resistance value. The set of identifying electrodes is made of metal material, and the resistive path is made of non-metal material. The set of measurement electrodes includes a reference electrode and a working electrode insulated from each other, and the set of identifying electrodes includes a first identifying electrode and a second identifying electrode connected with each other through the resistive path. The insulating layer covers a part of the electrode system, wherein a part of the electrode system not covered by the insulating layer forms a reaction region with a supply port. When a sample is injected into the supply port of the reaction region, the injected sample reaches the set of measurement electrodes and the set of identifying electrodes in sequence.

A hand-held device for electrical impedance myography

Abstract: A device for determining muscle condition of a region of tissue. The device comprises an electrical impedance myography (EIM) portable probe bearing an electrode array. The electrode array comprises excitation electrodes used to apply multi-frequency electrical signals to the region of tissue and pickup electrodes that are used to collect electrical signals resulting from the application of the multi-frequency electrical signals to the region of tissue. To improve accuracy and reproducibility of EIM measurements, the electrode array is reconfigurable to select different subsets of excitation and pickup electrodes so that the electrodes are oriented differently with respect to muscle fibers. Additional devices may be associated with the EIM probe to measure such parameters as temperature, moisture content of the region, quality of contact of electrodes of the electrode array with a surface of the region and pressure with which the EEM probe is applied to the region. The EIM measurements may be adjusted based on these parameters. Also, ultrasound and electrical impedance tomography measurements may supplement the ELM measurements for more complete analysis of the muscle condition.

Capacitive sensor array

Abstract: A capacitive sensor array includes a sensor electrode, a shielding electrode and a background electrode which are surrounded by insulator materials and connected to a control and evaluation circuit. Using the sensor electrode that extends along a first coordinate line, the entry of an object into a space ahead of the sensor electrode is detected. The control and evaluation circuit detects a capacity change of the sensor electrode as compared to a reference potential. The shielding electrode is connected to the sensor electrode via the control and evaluation circuit in such a manner that its potential follows. The three electrodes are arranged behind each other along a second coordinate line that is perpendicular to the first coordinate line. The insulating materials are arrayed between the sensor electrode and the detection zone. The central axis of the cylinder lies within the plane that is formed by the first and second coordinate lines. The insulator materials between the detection zone and the sensor electrode include at least one plastic layer that directly surrounds the sensor electrode and a plastic layer that is arrayed at a specified distance. The insulator materials are arranged so that the relative dielectricity constant initially assumes a relatively high value of the surrounding plastic layer as the distance from the sensor electrode increases, then drops to a value that approaches the value of 1, and then again rises to a relatively high value of the outer plastic layer.

Circuits and methods of producing a reference current or voltage

Abstract: A reference circuit includes a first transistor having a first current electrode, a control electrode, and a second current electrode coupled to a power supply terminal. The reference circuit further includes a resistive element including a first terminal coupled to the control electrode of the first transistor and a second terminal coupled to the first current electrode. Additionally, the reference circuit includes a second transistor including a first current electrode coupled to the second terminal of the resistive element, a control electrode coupled to the second terminal, and a second current electrode coupled to the power supply terminal. The second transistor is configured to produce an output signal related to a voltage at the control electrode of the first transistor.

Adjustable pulmonary vein ablation catheter

Abstract: A medical device is provided, including an elongate body defining a lumen therethrough; a shaft extending through the lumen; and an electrode array coupled to the elongate body at a first end and coupled to the shaft at a second end, where linear manipulation of the shaft causes the electrode array to transition from a first geometric configuration to a second configuration, and where rotational manipulation of the shaft causes the electrode array to transition from the second geometric configuration to a third configuration.

Apparatus and method for detecting terahertz wave

Abstract: A terahertz wave detecting apparatus includes a semiconductor chip 12 , a two-dimensional graphene 14 , a conductive source electrode 15 , and a drain electrode 16 and a gate electrode 17 The two-dimensional graphene 14 is connected to the source electrode and the drain electrode The apparatus further includes a SD voltage detection circuit 18 , a gate voltage applying circuit 19 and a magnetic field generating device 20