Passive Electrodes Research Articles

An Increase in Alpha Band Frequency in Resting State EEG after Electrical Stimulation of the Ear in Tinnitus Patients-A Pilot Study.

In our clinic invasive transtympanal promontory positive DC stimulations were first used, with a success rate of 42%. However, non-invasive hydrotransmissive negative DC stimulations are now favored, with improvement being obtained in 37.8% directly after the treatment, and 51.3% in a follow up 1 month after treatment. The further improvement after 1 month may be due to neuroplastic changes at central level as a result of altered peripheral input. The aim of the study was to determine how/whether a single electrical stimulation of the ear influences cortical activity, and whether changes observed in tinnitus after electrical stimulation are associated with any changes in cortical activity recorded in EEG. The study included 12 tinnitus patients (F–6, M-6) divided into two groups. Group I comprised six patients with unilateral tinnitus - unilateral, ipsilateral ES was performed. Group II comprised six patients with bilateral tinnitus—bilateral ES was performed. ES was performed using a custom-made apparatus. The active, silver probe—was immersed inside the external ear canal filled with saline. The passive electrode was placed on the forehead. The stimulating frequency was 250 Hz, the intensity ranged from 0.14 to 1.08 mA. The voltage was kept constant at 3 V. The duration of stimulation was 4 min. The EEG recording (Deymed QEST 32) was performed before and after ES. The patients assessed the intensity of tinnitus on the VAS 1-10.Results: In both groups an improvement in VAS was observed—in group I—in five ears (83.3%), in group II—in seven ears (58.3%). In Group I, a significant increase in the upper and lower limit frequency of alpha band was observed in the central temporal and frontal regions following ES. These changes, however, were not correlated with improvement in tinnitus. No significant changes were observed in the beta and theta bands and in group II. Preliminary results of our research reveal a change in cortical activity after electrical stimulations of the ear. However, it remains unclear if it is primary or secondary to peripheral auditory excitation. No similar studies had been found in the literature.

Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors

Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V−1 s−1.

Gentle, Nondestructive Monitoring of Wound Healing in Cell-Based Assays Using Electrochemical Impedance Spectroscopy

Electrical impedance spectroscopy is a soft analysis methods for living cell cultures, that is non-destructive for cell cultures and allows continuous measurement of cellular changed in real-time. In this work we report on an in vitro impedimetric sensors that measures the confluence and the density of human epithelial cell layers. A mechanically inflicted damage in a confluent cell layer leads to a reduction of the impedance, while the healing of the cell layer was closing the holes and increased impedance. The entire healing process could be tracked in real time via the impedance. To advance existing in vitro cell impedance spectroscopy we have not only used opwn metal electrodes but also electrically insulated interdigitated microelectrodes. The influence of the insulation on sensor performance is experimentally and theoretically analyzed A circuit model was established. In a comparison between open (not passivated) electrodes was made. The best setup for sensitivity and repeatability, which are crucial parameters for cell analysis, will be presented. The presented novel sensor design allows for the integration of alternative electrode materials such as aluminum. This enables cost-effective fabrication of large-volume sensor arrays.

(Keynote) Optical in-Situ Detection of Passive Oxides on Metals

The passivation and passive oxide films on metals and their in-situ detection were reviewed. Various optical techniques combined with electrochemistry have been used for the in-situ detection of the oxide film. (1) Ellipsometry and refrectometry are available for the thickness measurement. (2) Raman spectroscopy for the composition identification, (3) AC impedance and AC potential modulation reflectance for discussion of semiconducting and dielectric properties. For the investigation of the passive oxide film on metal electrodes, we must first consider whether the passive film-covered electrode system is placed under a stationary state or non-stationary state. Under the stationary state, the current on the passivated metal electrode is determined by a cationic transfer rate (dissolution rate) at the oxide/ solution interface. Because the ionic transfer rates are a function of the potential difference at the oxide/ solution interface and the interfacial potential difference is a function of solution pH, the dissolution rate can be described as a function of solution pH. Under the stationary state, the thickness of oxide film is kept constant and the ionic transfer rates at metal/ oxide and oxide/ solution interfaces and the ionic migration rate in the oxide film are equal to each other. When the stationary CD is the order of 0.01 μA cm–2 or less, time period to reaching the stationary state may be necessary for 1 d or longer and thus the stationary state cannot be easily reached in the experimental time. Usually we discuss the passive oxide films under the pseudo-stationary state condition. When one uses the results during the potentiodynamic condition, one should recognize the results under a non-stationary condition and the results are much different from those under the stationary state and much depend on the starting condition. For iron, aluminum, titanium etc. on which n-type and insulating oxide films are formed, the surface passive oxide linearly grows in thickness with increase of anodic potentials. The ionic migration rate is determined by the electric field in the oxide film according to the high-field ionic migration model after Cabrera and Mott 1-5) i = i0 exp [B(dE/dd)] i0 is a function of densities of migrating species in oxide film and (dE/dd) is a electric field in the oxide film and approximately as described by ΔE/d where ΔE and d is a potential drop in the oxide film and thickness of the oxide film, respectrivily. For example, under constant current oxidation, ΔE/d should be constant and thus thickness (d) is linearly increased with potential increase 6, 7). Under constant potential oxidation, log(i) linearly decreased with (1/d) 8). The difference between the semiconducting and insulating oxide films is seen in the higher potentials than an equilibrium potential of O2/ H2O redox. When the bang-gap energy of the semiconducting oxide is more or less 2.5 eV, the electron transfer between the inner conduction band to the redox species in the solution can occur via the tunneling process over the barrier of the space charge layer. The current corresponding to the oxygen evolution reaction emerges in the passive state and exponentially increases with increase of potential. When the band-gap energy is much larger, the tunneling process is inhibited and no current of the oxygen evolution reaction is observed. The oxide film of the insulating property such as the oxides on aluminum, tantalum, and silica can grow to several 100 nm thickness without evolution of oxygen gas. For the passive oxide film on stainless steel, simple relation between CD and thickness is not establish, because the composition of oxide film changes with time, Cr component enriching with increase of time 9). For the passive film consisting of p-type oxide such as Ni passive oxide, the thickness is not described as a function of potential by a simple relationship 10). References (1) H. Cabrera and N. F. Mott, Rep. Prog. Phys., 12 (1948) 163. (2) N. F. Mott, Trasnact. Faraday Soc., 43 (1947) 429/ (3) K. J. Vetter and F. Gorn, Electrochim. Acta, 18 (1973) 321. (4) K. E. Hesler, Ber. Bunsenges. Phys.Chem., 72 (1968) 1197. (5) N. Sato and T. Noda, Electrochim. Acta, 22 (1977) 839. (6) T. Ohtsuak and N. Nomura, Corros. Sci., 39 (1997) 1253. (7) T. Ohtsuka, Y. Sasaki, and A. hyono, Electrochim. Acta, 131 (2014) 116. (8) T. Nunoko T. Ohtsuka, and T. Sakamoto, Corros. Sci., 49 (2007) 4005. (9) T. Ohtsuka, M. Ueda, M. Abe, J. Eletrochem. Soc., to be submitted (2016). (10) T. Iida and T. Ohtsuka, Corros. Sci., 49 (2007) 1408.

Novel passive ceramic based semi-dry electrodes for recording electroencephalography signals from the hairy scalp

This study reports on a novel passive ceramic-based semi-dry electrode prototype for electroencephalography (EEG) applications. With the help of capillary forces of the porous ceramics pillars, the semi-dry electrodes build a stable electrode/scalp interface by penetrating hair and releasing a small amount saline in a controlled and sustained manner. The semi-dry electrode/scalp impedances were low and stable (44.4±16.9kΩ, n=10), and the variation between nine different positions was less 5kΩ. The semi-dry electrodes have shown non-polarization characteristics and the maximum difference of equilibrium potential between eight electrodes was 579μV. The semi-dry electrodes demonstrated long-term stability, and the impedance only increased by 20kΩ within 8h. EEG signals were simultaneously recorded using a 9-channel gel-based electrode and semi-dry electrode arrays setup on ten subjects. The average temporal cross-correlation between them in the eyes open/closed and the steady state visually evoked potentials (SSVEPs) paradigm were 0.938±0.037 and 0.937±0.027 respectively. Spectral analyses revealed similar response patterns with expected functional responses. Together with the advantages of quick setup, self-application and cleanliness, the result suggests the semi-dry electrode is suitable for emerging real-world EEG applications, such as brain-computer interfaces and wearable EEGs.

Core Muscle Activation During Unstable Overhead Squat Using a Water-Filled Training Tube

PURPOSE:Stability and balance are essential components for functional movement. While these components are often developed by exercising on unstable surfaces, another alternative is to use an unstable implement. The purpose of this study was to use a novel water-filled implement (“slosh tube”) to assess the degree of muscle instability created during an overhead squat. METHODS: Eight men (age= 20.1 ± 1.0y, ht=179.8 ± 4.8cm, mass= 89.2 ± 6.9kg) completed three 30s trials of an overhead squat using an 11.4 kg tube that was partially filled with water. A central valve allowed three conditions of water movement: 50% open, 100% open, and a stable(S), closed valve setting. Subjects completed 8-10 repetitions within each condition using a counter-balanced design. Muscle activation was assessed on the right side, with passive EMG electrodes placed over the belly of the vastus lateralis (VLAT), deltoid, rectus abdominus (AB), and paraspinal muscles. Integrated EMG was measured for each repetition and converted to a %MVC for each muscle. Instability was determined using the natural log of the coefficient of variation across repetitions. A two way repeated measures ANOVA across (contraction, condition) was used to examine concentric and eccentric contractions in each muscle. %MVC was also assessed. RESULTS:No significant instability was seen in any muscles for both CON and ECC. LnCV ranged from 3.0-3.5. Percent MVC activated was significantly greater for the Paraspinal muscle (CON= 53.6 ± 7.4, ECC = 45.1± 9.7%) and VLAT (CON= 332.3 ± 147.5, ECC= 288.8 ± 114.5) but not for the AB (CON= 10.6 ± 5.1, ECC= 9.2 ± 4.6) or the Deltoid ( CON= 41.3 ± 19.4, ECC = 39.7 ± 17.7) CONCLUSIONS: We conclude that the overhead squat using an unstable, water-filled tube maintains deltoid and abdominal muscle activation throughout the squat, but does not induce activation instability across the four muscles studied.

Embedded EEG Recording Module with Active Electrodes for Motor Imagery Brain-Computer Interface

This paper presents a novel modular, portable and low-power electroencephalography (EEG) acquisition system for a Brain-Computer Interface (BCI) application. The system is based on the versatile microcontroller MSP430F5529, to acquire from 4 to 12 EEG channels at 256 Hz with a single 3.7 V supply. The prototype supports both passive and active electrodes; these were also designed and built. Additionally, a graphic visualization interface was developed on the open-source programming language Processing. Common-mode rejection ratio, input-referred noise and magnitude and phase frequency response were measured for each analog EEG channel, these requirements comply the International Federation of Clinical Neurophysiology guidelines. Furthermore, four noise and distortion parameters for AC input signals were evaluated for each ADC channel, based on the IEEE-1241-2000 standard. Power spectrum of EEG recordings using our prototype and the commercial amplifier g.USBamp were compared in open/closed eyes conditions (alfa-band reactivity). It was verified that spectral information retrieval (EEG alfa peak) attained with the prototype is quite similar to the commercial system, and that 60 Hz noise level is reduced when using active instead of passive electrodes, as expected. It was shown that analog pre-processing and noise design considerations are effective ways to get a good quality EEG signal and to enhance certain portions of its frequency spectrum (0.1‑35 Hz). This embedded recording system improves the acquisition of EEG into the frequency bands of interest; the mu (8-13 Hz) and beta (14-27 Hz) EEG rhythms for a motor-imagery BCI application, while rejecting unwanted components (DC, >30 Hz, 60 Hz). With this design, it is possible to reduce noise and interferences in EEG signal to decrease the computational workload in digital post-processing, and thus, may increase the likelihood of achieving a completely stand-alone BCI system for clinical applications.

Development of the ‘Healthcor’ System as a Cardiac Disorders Symptoms Detector using an Expert System based on Arduino Uno

In the modern era, our lifestyles are very fast-moving; this makes us highly susceptible to diseases, especially those associated with heart problems. In this research, we developed a portable early detection system for cardiac disorders. This system consists of passive electrodes, named SHIELD-EKG-EMG-PA; a shield which allows Arduino-like boards to capture electrocardiography (ECG) and electromyography (EMG) signals, named SHIELD-EKG-EMG, both devices produced by Olimex; a microcontroller, based on Arduino Uno; and an expert system which is implemented by a personal computer. This system detects time intervals of various segments in ECG signals which are captured by the devices; it then analyzes the signals in order to determine whether the patient has cardiac disorders. We call our detecting system the HEALTHCOR system. A database was established, containing various possible values of parameters in ECG signals. The types of diseases that can be detected are heart rhythm disorders including sinus bradycardia, sinus tachycardia, sinus arrhythmia, and cardiac symptoms associated with intervals and the wave height, such as myocardial infarction. From our tests, the accuracy of our system is 96%. The resultant diagnoses of four patients are all appropriate, and used a commercial 12-lead electrocardiograph.

Percutaneous right atrial pacemaker lead repositioning using a regular deflectable ablation catheter.

Lead dislocation is one of the most undesired complications of permanent pacemaker implantation. The rate of dislodgement of atrial pacing leads is nearly 3% [1]. Reopening the pacemaker pocket and repositioning the lead is the most commonly used technique for correcting dislocations which occur in the early period after implantation. However, this increases the risk of pocket infection and increases lead insulation problems. Snare systems and urological baskets have also been used for repositioning atrial leads [2, 3]. We report a patient who experienced dislodgement of the atrial pacemaker lead of a cardiac resynchronization therapy (CRT) device, which was corrected using a regular deflectable ablation catheter by the transfemoral route. A 77-year-old female patient with severe ischemic left ventricular dysfunction and wide QRS had received a CRT device. At the follow-up 1 week after the procedure, atrial sensing and pacing dysfunctions were detected. Fluoroscopy revealed dislodgement of a passive fixation J-shaped atrial lead. Lead repositioning via a percutaneous transfemoral approach was planned to avoid surgical revision. A regular deflectable ablation catheter (steerable 4-mm-tip ablation catheter, Mariner, Medtronic, Minneapolis, USA) was advanced to the right atrium through a 7 Fr introducer from the right femoral vein. We propagated the ablation catheter above the level of the atrial lead and made an anteflexion to the distal portion of the catheter. We captured the distal loop of the atrial lead, then with a slight counterclockwise rotation and pull back we oriented the atrial lead towards the right atrial appendage (Figure 1). The lead functions were normal after the intervention. The patient was discharged the next morning and had normal pacemaker functions at follow-up. Figure 1 Successful atrial lead reposition by deflectable ablation catheter Early lead displacements after pacemaker implantations are the most frequent cause of reintervention in the majority of patients. We performed successful atrial lead repositioning with a deflectable ablation catheter by the percutaneous approach without the need for a surgical operation. However, this technique has a number of contraindications. Percutaneous lead repositioning can only be performed on patients who have passive fixation electrodes and leads with suitable loop anatomy. Conditions which necessitate the removal of the dislocated lead such as serious insulation problems are another contraindication for percutaneous lead repositioning. Repositioning of active fixation leads should be performed surgically. Since our case had a passive fixation atrial lead and a suitable loop anatomy, it was possible to perform the procedure safely. However, operators need to be cautious about dislodgement of other stable leads while performing the procedure, especially in patients with an implanted CRT. Favale et al. reported successful percutaneous atrial lead repositioning in 2 patients with permanent pacemakers and in 1 patient with an implantable cardioverter defibrillator [4]. We believe that our paper is the first one to report percutaneous atrial lead repositioning with a regular deflection ablation catheter in a patient with a CRT device. Although it needs some experience, percutaneous transfemoral lead repositioning is a much less invasive technique and may be preferred as a first-step approach if the patient has acceptable loop anatomy of the atrial lead.

Comparing drug-induced seizure-liability in human iPSC-derived and primary mouse neurons grown on micro-electrode arrays

Comparing drug-induced seizure-liability in human iPSC-derived and primary mouse neurons grown on micro-electrode arrays

A novel passive electrode based on porous Ti for EEG recording

In this paper, we present a novel passive electrode based on porous titanium (Ti) for electroencephalography (EEG) recording. There was a reservoir with a capacity of 200μl on the passive electrode. When the slight pressure was applied on the reservoir, the electrolyte in the reservoir permeated from micro-holes of the porous Ti onto the skin. The liquid could provide continuous wet interface between electrode and skin to maintain low and stable contact impedance. After the pressure was removed, the liquid withdrew into the reservoir to make the skin keep clean. Meanwhile, the amount of the permeated liquid was too little to form short circuit of adjacent electrodes. We used physiological saline as the electrolyte because it was not different from conductive gel of the conventional silver/silver chloride (Ag/AgCl) electrode and didn’t cause skin irritations or allergic reactions. The testing results indicated that the passive electrode had a relatively low skin-electrode contact impedance. The alpha rhythm and N100 auditory evoked potential were measured to evaluate the electrode performance for EEG recording.

Development and analysis of a small-size electric field coupling wireless power system

This study intends to fabricate a small-size capacitive wireless transmission device. As to the design of electrode plates, the active electrode is designed in two ways, through row array and column array, and the area of an electrode plate is limited to below 20.25 cm2. Moreover, the passive electrode of row-array electrode plates is designed in three ways: general row array, window array, and rhombus array. As seen from the results of circuit simulation, the transmission efficiency of the capacitive wireless transmission device is as high as 0.7. In the actual circuit experiment, the electrode plate in the window-array design has the highest efficiency at 51%. In addition, the electrode plates in the window array and those in other arrays have higher stability and transmission efficiency. In the rotational angle dislocation experiment, the unit area current amount of the column-array electrode plates in the high coupling region is also smaller than that of the window-array electrode plates. However, the performance of column-array electrode plates reaches higher stability in the angle dislocation experiment, and its anti-angle dislocation is obviously higher than that of the electrode plates designed in the other three row arrays. Moreover, when the area of the column-array electrode plates is 22.25 cm2, the highest transmission distance is 22.5 mm.

Switching “on and off” faradaic electrochemistry at an otherwise passivated electrode using gold-coated magnetic nanoparticles

Herein we combined the use of self-assembled monolayer (SAM) modified electrodes and gold coated magnetic nanoparticles (Au@MNPs) to modulate faradaic electrochemistry when nanoparticles are absorbed on and removed from, a passivated electrode using an external magnetic field. Substantial faradaic electrochemistry of potassium ferricyanide in solution is first prevented by modifying gold electrodes with 11-mercaptoundecanoic acid to form a passivating SAM. Restoration of the faradaic electrochemistry is then achieved by introducing Au@MNPs which are brought to the surface using an external magnetic field. The faradaic electrochemistry can again be suppressed by removing Au@MNPs from the SAM using another external magnetic field.

Interaction Between Interconnected and Isolated Grounding Systems: A Case Study of Transferred Potentials

The effect caused by ground fault current in a complex system of interacting electrodes is theoretically studied. The calculation applies to a specific case in which a set of interconnected electrodes, which are part of a grounding facility network, are activated by ground fault current. Transferred potentials to adjacent passive electrodes are calculated and the most relevant parameters of the electrode system are evaluated. Finally, the convenience of connecting the grounding electrodes is discussed.

Reduction of NOx and PM in marine diesel engine exhaust gas using microwave plasma

Abatement of NOx and particulate matters (PM) of marine diesel exhaust gas using microwave (MW) non-thermal plasma is presented in this paper. NOx mainly consist of NO and less concentration of NO2 in a typical two stoke marine diesel engine and microwave plasma generation can completely remove NO. MW was generated using two 2kW microwave sources and a saw tooth passive electrode. Passive electrode was used to generate high electric field region within microwave environment where high energetic electrons (1-3eV) are produced for the generation of non-thermal plasma (NTP). 2kW gen-set diesel exhaust gas was used to test our pilot-scale MW plasma reactor. The experimental results show that almost 100% removal of NO is possible for the exhaust gas flow rate of 60l/s. It was also shown that MW can significantly remove soot particles (PM, 10nm to 365nm) entrained in the exhaust gas of 200kW marine diesel engine with 40% engine load and gas flow rate of 130l/s. MW without generating plasma showed reduction up to 50% reduction of PM and with the plasma up to 90% reduction. The major challenge in these experiments was that igniting the desired plasma and sustaining it with passive electrodes for longer period (10s of minutes) as it required fine tuning of electrode position, which was influenced by many factors such as gas flow rate, geometry of reactor and MW power.

Velocity Measurement of EHD Flow Produced by Pin-Multi Concentric Ring Electrodes Generator

Study of EHD flow by using generator corona discharge with electrodes configuration of pin to multi concentric rings (MCR) and pin to single ring (SR) have been curried out. We measured the velocity of EHD flow and determined the comparison of velocity of EHD flow produced by pin to single ring electrodes. The pin needle was made by stainless steel with a length of 50 mm and a tip diameter of 0.14 mm. The multi-ring electrodes constracted by three concentric rings with a metal material connected to each other and each ring has a diameter of 24 mm, 16 mm and 8 mm in width and the same ring thickness is 2 mm and 3 mm. Single ring electrode has a diameter, width and thickness respectively 24 mm , 3 mm and 2 mm. EHD was generated by using a DC high voltage of 10 kV. Pin as an active electrode of corona discharge and concentric rings multi/single ring electrodes as ions collector and passive electrodes. The velocity of EHD flow was measured by a hot-wire anemometer. We found that the velocity of EHD flow with multi-ring concentric electrodes larger than a single ring electrode. The measurement of velocity for two cases of electrodes configuration were limited at the certain voltage due to breackdown and arc phenomena. The maximum velocity of the of EHD flow using a pin-multi rings concentric was 0.7 m/s at a voltage of 6 kV.

Examining lake-bottom structures with the resistivity imaging method in Ilan's Da-Hu Lake in Northeastern Taiwan

In this study, we used the electrical resistivity method for imaging subsurface structures of lake-bottom sediment in Da-Hu Lake in Ilan, Taiwan. Floating passive electrodes were used for the surveys in the study area. We deployed eighteen survey lines across the lake, and executed the survey with the Schlumberger and Wenner array. There are two geological cores, DH-7A and DH-7B, located at different locations in Da-Hu Lake. The cores were carefully collected for the purpose of the sediment and dating analyses, as well as for the geochemical testing, which can be useful to climate-change studies covering the past 10,000years. The inverted images clarify the spatial relationships between the sediment and basement structures. The sediments above the resistive rock basement consisted of the sand sediments (from 45 to 60Ωm) and mud sediments (less than 30Ωm). The results of our study show that a sandy layer comprising slate debris with a resistivity of 45 to 60Ωm is located 3 to 8m under the water's surface in the eastern part of the lake, and the outcomes confirm the findings from the DH-7A core data. The resistivity spatial distribution suggests that the lake's sand layer originally came from a region east of the lake. We also found a sharp linear resistivity structure in the western part of the lake. The structure's strike is consistent with observations from the normal fault's surface outcrops near the western part of the lake. Consequently, we infer that this structure line might be a stretch of the normal fault and that the two cores are located at the hanging wall as well. In addition, the results show that we can use the electrical resistivity imaging method with floating passive electrodes to investigate the lake-bottom in detail.

Observation of nanometer-sized electro-active defects in insulating layers by fluorescence microscopy and electrochemistry.

We report a method to study electro-active defects in passivated electrodes. This method couples fluorescence microscopy and electrochemistry to localize and size electro-active defects. The method was validated by comparison with a scanning probe technique, scanning electrochemical microscopy. We used our method for studying electro-active defects in thin TiO2 layers electrodeposited on 25 μm diameter Pt ultramicroelectrodes (UMEs). The permeability of the TiO2 layer was estimated by measuring the oxidation of ferrocenemethanol at the UME. Blocking of current ranging from 91.4 to 99.8% was achieved. Electro-active defects with an average radius ranging between 9 and 90 nm were observed in these TiO2 blocking layers. The distribution of electro-active defects over the TiO2 layer is highly inhomogeneous and the number of electro-active defect increases for lower degree of current blocking. The interest of the proposed technique is the possibility to quickly (less than 15 min) image samples as large as several hundreds of μm(2) while being able to detect electro-active defects of only a few tens of nm in radius.

Cooperative dry-electrode sensors for multi-lead biopotential and bioimpedance monitoring

Cooperative sensors is a novel measurement architecture that allows the acquiring of biopotential signals on patients in a comfortable and easy-to-integrate manner. The novel sensors are defined as cooperative in the sense that at least two of them work in concert to measure a target physiological signal, such as a multi-lead electrocardiogram or a thoracic bioimpedance.This paper starts by analysing the state-of-the-art methods to simultaneously measure biopotential and bioimpedance signals, and justifies why currently (1) passive electrodes require the use of shielded or double-shielded cables, and (2) active electrodes require the use of multi-wired cabled technologies, when aiming at high quality physiological measurements.In order to overcome the limitations of the state-of-the-art, a new method for biopotential and bioimpedance measurement using the cooperative sensor is then presented. The novel architecture allows the acquisition of the aforementioned biosignals without the need of shielded or multi-wire cables by splitting the electronics into separate electronic sensors comprising each of two electrodes, one for voltage measurement and one for current injection. The sensors are directly in contact with the skin and connected together by only one unshielded wire. This new configuration requires one power supply per sensor and all sensors need to be synchronized together to allow them to work in concert.After presenting the working principle of the cooperative sensor architecture, this paper reports first experimental results on the use of the technology when applied to measuring multi-lead ECG signals on patients. Measurements performed on a healthy patient demonstrate the feasibility of using this novel cooperative sensor architecture to measure biopotential signals and compliance with common mode rejection specification accordingly to international standard (IEC 60601-2-47) has also been assessed.By reducing the need of using complex wiring setups, and by eliminating the presence of central recording devices (cooperative sensors directly sense and store the measured biosignals on the site), the depicted novel technology is a candidate to a novel generation of highly-integrated, comfortable and reliable technologies that measure physiological signals in real-life scenarios.

GaN Micromechanical Resonators with Meshed Metal Bottom Electrode.

This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO2) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient (d33) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF2) etch and therefore eliminating the need for backside lithography and etching.