High frequency reference electrode

DOEpatents

Kronberg, J.W.

1994-05-31

A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

High frequency reference electrode

DOEpatents

Kronberg, James W.

1994-01-01

A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

A Multi-Channel, Flex-Rigid ECoG Microelectrode Array for Visual Cortical Interfacing

PubMed Central

Tolstosheeva, Elena; Gordillo-González, Víctor; Biefeld, Volker; Kempen, Ludger; Mandon, Sunita; Kreiter, Andreas K.; Lang, Walter

2015-01-01

High-density electrocortical (ECoG) microelectrode arrays are promising signal-acquisition platforms for brain-computer interfaces envisioned, e.g., as high-performance communication solutions for paralyzed persons. We propose a multi-channel microelectrode array capable of recording ECoG field potentials with high spatial resolution. The proposed array is of a 150 mm2 total recording area; it has 124 circular electrodes (100, 300 and 500 μm in diameter) situated on the edges of concentric hexagons (min. 0.8 mm interdistance) and a skull-facing reference electrode (2.5 mm2 surface area). The array is processed as a free-standing device to enable monolithic integration of a rigid interposer, designed for soldering of fine-pitch SMD-connectors on a minimal assembly area. Electrochemical characterization revealed distinct impedance spectral bands for the 100, 300 and 500 μm-type electrodes, and for the array's own reference. Epidural recordings from the primary visual cortex (V1) of an awake Rhesus macaque showed natural electrophysiological signals and clear responses to standard visual stimulation. The ECoG electrodes of larger surface area recorded signals with greater spectral power in the gamma band, while the skull-facing reference electrode provided higher average gamma power spectral density (γPSD) than the common average referencing technique. PMID:25569757

Internal corrosion monitoring of subsea oil and gas production equipment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joosten, M.W.; Fischer, K.P.; Strommen, R.

1995-04-01

Nonintrusive techniques will dominate subsea corrosion monitoring compared with the intrusive methods because such methods do not interfere with pipeline operations. The long-term reliability of the nonintrusive techniques in general is considered to be much better than that of intrusive-type probes. The nonintrusive techniques based on radioactive tracers (TLA, NA) and FSM and UT are expected to be the main types of subsea corrosion monitoring equipment in the coming years. Available techniques that could be developed specifically for subsea applications are: electrochemical noise, corrosion potentials (using new types of reference electrodes), multiprobe system for electrochemical measurements, and video camera inspectionmore » (mini-video camera with light source). The following innovative techniques have potential but need further development: ion selective electrodes, radioactive tracers, and Raman spectroscopy.« less

Localised electrochemical impedance measurements of a polymer electrolyte fuel cell using a reference electrode array to give cathode-specific measurements and examine membrane hydration dynamics

NASA Astrophysics Data System (ADS)

Engebretsen, Erik; Hinds, Gareth; Meyer, Quentin; Mason, Tom; Brightman, Edward; Castanheira, Luis; Shearing, Paul R.; Brett, Daniel J. L.

2018-04-01

Advances in bespoke diagnostic techniques for polymer electrolyte fuel cells continue to provide unique insight into the internal operation of these devices and lead to improved performance and durability. Localised measurements of current density have proven to be extremely useful in designing better fuel cells and identifying optimal operating strategies, with electrochemical impedance spectroscopy (EIS) now routinely used to deconvolute the various losses in fuel cells. Combining the two techniques provides another dimension of understanding, but until now each localised EIS has been based on 2-electrode measurements, composed of both the anode and cathode responses. This work shows that a reference electrode array can be used to give individual electrode-specific EIS responses, in this case the cathode is focused on to demonstrate the approach. In addition, membrane hydration dynamics are studied under current load steps from open circuit voltage. A three-stage process is identified associated with an initial rapid reduction in membrane resistance after 10 s of applying a current step, followed by a slower ramp to approximately steady state, which was achieved after ∼250 s. These results support previously published work that has looked at membrane swelling dynamics and reveal that membrane hydration/membrane resistance is highly heterogeneous.

Corrosion Studies of Wrought and Cast NASA-23 Alloy

NASA Technical Reports Server (NTRS)

Danford, M. D.

1997-01-01

Corrosion studies were carried out for wrought and cast NASA-23 alloy using electrochemical methods. The scanning reference electrode technique (SRET), the polarization resistance technique (PR), and the electrochemical impedance spectroscopy (EIS) were employed. These studies corroborate the findings of stress corrosion studies performed earlier, in that the material is highly resistant to corrosion.

Research notes : evaluation of the performance of reference electrodes embedded in reinforced concrete.

DOT National Transportation Integrated Search

1995-07-01

The objectives of this work were to examine placement strategies for reference electrodes and to evaluate the suitability of graphite reference electrodes as imbedded reference electrodes in reinforced concrete structures that are cathodically protec...

Hearing the Sound in the Brain: Influences of Different EEG References.

PubMed

Wu, Dan

2018-01-01

If the scalp potential signals, the electroencephalogram (EEG), are due to neural "singers" in the brain, how could we listen to them with less distortion? One crucial point is that the data recording on the scalp should be faithful and accurate, thus the choice of reference electrode is a vital factor determining the faithfulness of the data. In this study, music on the scalp derived from data in the brain using three different reference electrodes were compared, including approximate zero reference-reference electrode standardization technique (REST), average reference (AR), and linked mastoids reference (LM). The classic music pieces in waveform format were used as simulated sources inside a head model, and they were forward calculated to scalp as standard potential recordings, i.e., waveform format music from the brain with true zero reference. Then these scalp music was re-referenced into REST, AR, and LM based data, and compared with the original forward data (true zero reference). For real data, the EEG recorded in an orthodontic pain control experiment were utilized for music generation with the three references, and the scale free index (SFI) of these music pieces were compared. The results showed that in the simulation for only one source, different references do not change the music/waveform; for two sources or more, REST provide the most faithful music/waveform to the original ones inside the brain, and the distortions caused by AR and LM were spatial locations of both source and scalp electrode dependent. The brainwave music from the real EEG data showed that REST and AR make the differences of SFI between two states more recognized and found the frontal is the main region that producing the music. In conclusion, REST can reconstruct the true signals approximately, and it can be used to help to listen to the true voice of the neural singers in the brain.

Cochlear Implant Electrode Localization Using an Ultra-High Resolution Scan Mode on Conventional 64-Slice and New Generation 192-Slice Multi-Detector Computed Tomography.

PubMed

Carlson, Matthew L; Leng, Shuai; Diehn, Felix E; Witte, Robert J; Krecke, Karl N; Grimes, Josh; Koeller, Kelly K; Bruesewitz, Michael R; McCollough, Cynthia H; Lane, John I

2017-08-01

A new generation 192-slice multi-detector computed tomography (MDCT) clinical scanner provides enhanced image quality and superior electrode localization over conventional MDCT. Currently, accurate and reliable cochlear implant electrode localization using conventional MDCT scanners remains elusive. Eight fresh-frozen cadaveric temporal bones were implanted with full-length cochlear implant electrodes. Specimens were subsequently scanned with conventional 64-slice and new generation 192-slice MDCT scanners utilizing ultra-high resolution modes. Additionally, all specimens were scanned with micro-CT to provide a reference criterion for electrode position. Images were reconstructed according to routine temporal bone clinical protocols. Three neuroradiologists, blinded to scanner type, reviewed images independently to assess resolution of individual electrodes, scalar localization, and severity of image artifact. Serving as the reference standard, micro-CT identified scalar crossover in one specimen; imaging of all remaining cochleae demonstrated complete scala tympani insertions. The 192-slice MDCT scanner exhibited improved resolution of individual electrodes (p < 0.01), superior scalar localization (p < 0.01), and reduced blooming artifact (p < 0.05), compared with conventional 64-slice MDCT. There was no significant difference between platforms when comparing streak or ring artifact. The new generation 192-slice MDCT scanner offers several notable advantages for cochlear implant imaging compared with conventional MDCT. This technology provides important feedback regarding electrode position and course, which may help in future optimization of surgical technique and electrode design.

Electrocatalytic cermet gas detector/sensor

DOEpatents

Vogt, Michael C.; Shoemarker, Erika L.; Fraioli, deceased, Anthony V.

1995-01-01

An electrocatalytic device for sensing gases. The gas sensing device includes a substrate layer, a reference electrode disposed on the substrate layer comprised of a nonstoichiometric chemical compound enabling oxygen diffusion therethrough, a lower reference electrode coupled to the reference electrode, a solid electrolyte coupled to the lower reference electrode and an upper catalytically active electrode coupled to the solid electrolyte.

Actinide ion sensor for pyroprocess monitoring

DOEpatents

Jue, Jan-fong; Li, Shelly X.

2014-06-03

An apparatus for real-time, in-situ monitoring of actinide ion concentrations which comprises a working electrode, a reference electrode, a container, a working electrolyte, a separator, a reference electrolyte, and a voltmeter. The container holds the working electrolyte. The voltmeter is electrically connected to the working electrode and the reference electrode and measures the voltage between those electrodes. The working electrode contacts the working electrolyte. The working electrolyte comprises an actinide ion of interest. The reference electrode contacts the reference electrolyte. The reference electrolyte is separated from the working electrolyte by the separator. The separator contacts both the working electrolyte and the reference electrolyte. The separator is ionically conductive to the actinide ion of interest. The reference electrolyte comprises a known concentration of the actinide ion of interest. The separator comprises a beta double prime alumina exchanged with the actinide ion of interest.

Electrochemical Detectors in HPLC and Ion Chromatography.

PubMed

Horvai, George; Pungor, ErnÕ

1989-01-01

Back in 1952, the renowned Polish electrochemist Wiktor Kemula introduced chromato-polarography, 1 i.e., polaro-graphic detection for liquid chromatography. This technique continued to develop slowly until the early 1970s (for a review see Reference 2) when modem high-performance liquid chromatography (HPLC) emerged. This new, highly efficient chromatographc method could only be. used with detectors ensuring low dispersion. It was not easy to modify the dropping mercury electrode cells to satisfy this requirement. However, at the same time, electroanalytical chemists, who already had much experience in using carbon-based electrodes for oxidative detection in flow analysis, put forward the idea of oxidative amperometric detection in liquid chromatography. 3,4 In this technique, solid or quasi-solid (paste) electrodes were used and this made possible the construction of miniaturized cells with just a few microliter volume.

Electrocatalytic cermet gas detector/sensor

DOEpatents

Vogt, M.C.; Shoemarker, E.L.; Fraioli, A.V.

1995-07-04

An electrocatalytic device for sensing gases is described. The gas sensing device includes a substrate layer, a reference electrode disposed on the substrate layer comprised of a nonstoichiometric chemical compound enabling oxygen diffusion therethrough, a lower reference electrode coupled to the reference electrode, a solid electrolyte coupled to the lower reference electrode and an upper catalytically active electrode coupled to the solid electrolyte. 41 figs.

Hearing the Sound in the Brain: Influences of Different EEG References

PubMed Central

Wu, Dan

2018-01-01

If the scalp potential signals, the electroencephalogram (EEG), are due to neural “singers” in the brain, how could we listen to them with less distortion? One crucial point is that the data recording on the scalp should be faithful and accurate, thus the choice of reference electrode is a vital factor determining the faithfulness of the data. In this study, music on the scalp derived from data in the brain using three different reference electrodes were compared, including approximate zero reference—reference electrode standardization technique (REST), average reference (AR), and linked mastoids reference (LM). The classic music pieces in waveform format were used as simulated sources inside a head model, and they were forward calculated to scalp as standard potential recordings, i.e., waveform format music from the brain with true zero reference. Then these scalp music was re-referenced into REST, AR, and LM based data, and compared with the original forward data (true zero reference). For real data, the EEG recorded in an orthodontic pain control experiment were utilized for music generation with the three references, and the scale free index (SFI) of these music pieces were compared. The results showed that in the simulation for only one source, different references do not change the music/waveform; for two sources or more, REST provide the most faithful music/waveform to the original ones inside the brain, and the distortions caused by AR and LM were spatial locations of both source and scalp electrode dependent. The brainwave music from the real EEG data showed that REST and AR make the differences of SFI between two states more recognized and found the frontal is the main region that producing the music. In conclusion, REST can reconstruct the true signals approximately, and it can be used to help to listen to the true voice of the neural singers in the brain. PMID:29593487

Electrochemistry in ethanol. I. Reference electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zara, A.J.; de S. Bulhoes, L.O.

1982-01-01

The silver/silver nitrate electrode was found to be a suitable reference electrode in ethanolic solutions (2% v/v in water). The concentration of Ag/sup +/ inside the reference electrode is satisfactory in teh 0.1 to 10 mM concentration range. The liquid junction potential is minimized with sufficient supporting electrolyte (e.g., 0.1 to 0.5 M sodium perchlorate). The electrode is suitable for use as reference electrode in potentiometry and in polarography. Preparation is uncomplicated and the product is stable. 4 figures.

ZnO-Based Microfluidic pH Sensor: A Versatile Approach for Quick Recognition of Circulating Tumor Cells in Blood.

PubMed

Mani, Ganesh Kumar; Morohoshi, Madoka; Yasoda, Yutaka; Yokoyama, Sho; Kimura, Hiroshi; Tsuchiya, Kazuyoshi

2017-02-15

The present study is concerned about the development of highly sensitive and stable microfluidic pH sensor for possible identification of circulating tumor cells (CTCs) in blood. The precise pH measurements between silver-silver chloride (Ag/AgCl) reference electrode and zinc oxide (ZnO) working electrode have been investigated in the microfluidic device. Since there is a direct link between pH and cancer cells, the developed device is one of the valuable tools to examine circulating tumor cells (CTCs) in blood. The ZnO-based working electrode was deposited by radio frequency (rf) sputtering technique. The potential voltage difference between the working and reference electrodes (Ag/AgCl) is evaluated on the microfluidic device. The ideal Nernstian response of -43.71165 mV/pH was achieved along with high stability and quick response time. Finally, to evaluate the real time capability of the developed microfluidic device, in vitro testing was done with A549, A7r5, and MDCK cells.

Evaluation of local electric fields generated by transcranial direct current stimulation with an extracephalic reference electrode based on realistic 3D body modeling

NASA Astrophysics Data System (ADS)

Im, Chang-Hwan; Park, Ji-Hye; Shim, Miseon; Chang, Won Hyuk; Kim, Yun-Hee

2012-04-01

In this study, local electric field distributions generated by transcranial direct current stimulation (tDCS) with an extracephalic reference electrode were evaluated to address extracephalic tDCS safety issues. To this aim, we generated a numerical model of an adult male human upper body and applied the 3D finite element method to electric current conduction analysis. In our simulations, the active electrode was placed over the left primary motor cortex (M1) and the reference electrode was placed at six different locations: over the right temporal lobe, on the right supraorbital region, on the right deltoid, on the left deltoid, under the chin, and on the right buccinator muscle. The maximum current density and electric field intensity values in the brainstem generated by the extracephalic reference electrodes were comparable to, or even less than, those generated by the cephalic reference electrodes. These results suggest that extracephalic reference electrodes do not lead to unwanted modulation of the brainstem cardio-respiratory and autonomic centers, as indicated by recent experimental studies. The volume energy density was concentrated at the neck area by the use of deltoid reference electrodes, but was still smaller than that around the active electrode locations. In addition, the distributions of elicited cortical electric fields demonstrated that the use of extracephalic reference electrodes might allow for the robust prediction of cortical modulations with little dependence on the reference electrode locations.

Effect of EEG Referencing Methods on Auditory Mismatch Negativity

PubMed Central

Mahajan, Yatin; Peter, Varghese; Sharma, Mridula

2017-01-01

Auditory event-related potentials (ERPs) have consistently been used in the investigation of auditory and cognitive processing in the research and clinical laboratories. There is currently no consensus on the choice of appropriate reference for auditory ERPs. The most commonly used references in auditory ERP research are the mathematically linked-mastoids (LM) and average referencing (AVG). Since LM and AVG referencing procedures do not solve the issue of electrically-neutral reference, Reference Electrode Standardization Technique (REST) was developed to create a neutral reference for EEG recordings. The aim of the current research is to compare the influence of the reference on amplitude and latency of auditory mismatch negativity (MMN) as a function of magnitude of frequency deviance across three commonly used electrode montages (16, 32, and 64-channel) using REST, LM, and AVG reference procedures. The current study was designed to determine if the three reference methods capture the variation in amplitude and latency of MMN with the deviance magnitude. We recorded MMN from 12 normal hearing young adults in an auditory oddball paradigm with 1,000 Hz pure tone as standard and 1,030, 1,100, and 1,200 Hz as small, medium and large frequency deviants, respectively. The EEG data recorded to these sounds was re-referenced using REST, LM, and AVG methods across 16-, 32-, and 64-channel EEG electrode montages. Results revealed that while the latency of MMN decreased with increment in frequency of deviant sounds, no effect of frequency deviance was present for amplitude of MMN. There was no effect of referencing procedure on the experimental effect tested. The amplitude of MMN was largest when the ERP was computed using LM referencing and the REST referencing produced the largest amplitude of MMN for 64-channel montage. There was no effect of electrode-montage on AVG referencing induced ERPs. Contrary to our predictions, the results suggest that the auditory MMN elicited as a function of increments in frequency deviance does not depend on the choice of referencing procedure. The results also suggest that auditory ERPs generated using REST referencing is contingent on the electrode arrays more than the AVG referencing. PMID:29066945

In situ electrochemical investigations of the kinetic and thermodynamic properties of nickel-metal hydride traction batteries

NASA Astrophysics Data System (ADS)

Yang, Xiao Guang; Liaw, Bor Yann

Although large ampere hour nickel-metal hydride (Ni-MH) traction batteries are in the stage of being commercialized for electric and hybrid vehicle applications, little is known about their performance characteristics. By using a standard Hg/HgO reference electrode in a commercial Ni-MH battery, we were able to conduct in situ measurements to determine both kinetic and thermodynamic properties of the system, including the characteristics of individual electrodes. Using the galvanostatic intermittent titration technique (GITT), we simultaneously and effectively determined the open-circuit voltage of the battery, the equilibrium electrode potentials, and the diffusion coefficient of proton and hydrogen in the nickel and metal hydride electrode, respectively, as a function of the states of charge (SOC). Using the current-step excitation technique, we found that the internal resistance of the battery primarily comes from the metal hydride electrode, which is greater by one order of magnitude than that of the Ni electrode. The cyclic linear micro-polarization experiments, on the other hand, showed that the charge-transfer resistance of the electrochemical reaction at the metal hydride electrode is about twice larger than that of the Ni counterpart above 20% SOC. In comparison, the internal resistance is an order of magnitude smaller than those of the electrochemical charge-transfer reactions. The micro-polarization technique also allowed us to calculate the exchange current densities of the respective electrode electrochemical reactions and the associated specific exchange current densities. These in situ, simple but detailed, characterizations of the thermodynamic and kinetic properties of the Ni-MH system provided valuable information for better understanding of the battery performance.

Corrosion Studies of 2195 Al-Li Alloy and 2219 Al Alloy with Differing Surface Treatments

NASA Technical Reports Server (NTRS)

Danford, M. D.; Mendrek, M. J.

1998-01-01

Corrosion studies of 2195 Al-Li and 2219 Al alloys have been conducted using the scanning reference electrode technique (SRET) and the polarization resistance (PR) technique. The SRET was used to study corrosion mechanisms, while corrosion rate measurements were studied with the PR technique. Plates of Al203 blasted, soda blasted and conversion coated 2219 Al were coated with Deft primer and the corrosion rates studied with the EIS technique. Results from all of these studies are presented.

Gold nanoparticle decorated multi-walled carbon nanotubes as counter electrode for dye sensitized solar cells.

PubMed

Kaniyoor, Adarsh; Ramaprabhu, Sundara

2012-11-01

A novel counter electrode material for dye sensitized solar cells (DSSCs) composed of nanostructured Au particles decorated on functionalized multi-walled carbon nanotubes (f-MWNTs) is demonstrated for the first time. MWNTs synthesized by catalytic chemical vapor deposition technique are purified and functionalized by treating with concentrated acids. Au nanoparticles are decorated on f-MWNTs by a rapid and facile microwave assisted polyol reduction method. The materials are characterized by X-ray diffractometry, Fourier transform infra red spectroscopy and electron microscopy. The DSSC fabricated with Au/f-MWNTs based counter electrode shows enhanced power conversion efficiency (eta) of 4.9% under AM 1.5G simulated solar radiation. In comparison, the reference DSSCs fabricated with f-MWNTs and Pt counter electrodes show eta of 2.1% and 4.5%. This high performance of Au/f-MWNTs counter electrode is investigated using electrochemical impedance spectroscopy and cyclic voltammetry studies.

A Comparative Study of Average, Linked Mastoid, and REST References for ERP Components Acquired during fMRI

PubMed Central

Yang, Ping; Fan, Chenggui; Wang, Min; Li, Ling

2017-01-01

In simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) studies, average reference (AR), and digitally linked mastoid (LM) are popular re-referencing techniques in event-related potential (ERP) analyses. However, they may introduce their own physiological signals and alter the EEG/ERP outcome. A reference electrode standardization technique (REST) that calculated a reference point at infinity was proposed to solve this problem. To confirm the advantage of REST in ERP analyses of synchronous EEG-fMRI studies, we compared the reference effect of AR, LM, and REST on task-related ERP results of a working memory task during an fMRI scan. As we hypothesized, we found that the adopted reference did not change the topography map of ERP components (N1 and P300 in the present study), but it did alter the task-related effect on ERP components. LM decreased or eliminated the visual working memory (VWM) load effect on P300, and the AR distorted the distribution of VWM location-related effect at left posterior electrodes as shown in the statistical parametric scalp mapping (SPSM) of N1. ERP cortical source estimates, which are independent of the EEG reference choice, were used as the golden standard to infer the relative utility of different references on the ERP task-related effect. By comparison, REST reference provided a more integrated and reasonable result. These results were further confirmed by the results of fMRI activations and a corresponding EEG-only study. Thus, we recommend the REST, especially with a realistic head model, as the optimal reference method for ERP data analysis in simultaneous EEG-fMRI studies. PMID:28529472

A Comparative Study of Average, Linked Mastoid, and REST References for ERP Components Acquired during fMRI.

PubMed

Yang, Ping; Fan, Chenggui; Wang, Min; Li, Ling

2017-01-01

In simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) studies, average reference (AR), and digitally linked mastoid (LM) are popular re-referencing techniques in event-related potential (ERP) analyses. However, they may introduce their own physiological signals and alter the EEG/ERP outcome. A reference electrode standardization technique (REST) that calculated a reference point at infinity was proposed to solve this problem. To confirm the advantage of REST in ERP analyses of synchronous EEG-fMRI studies, we compared the reference effect of AR, LM, and REST on task-related ERP results of a working memory task during an fMRI scan. As we hypothesized, we found that the adopted reference did not change the topography map of ERP components (N1 and P300 in the present study), but it did alter the task-related effect on ERP components. LM decreased or eliminated the visual working memory (VWM) load effect on P300, and the AR distorted the distribution of VWM location-related effect at left posterior electrodes as shown in the statistical parametric scalp mapping (SPSM) of N1. ERP cortical source estimates, which are independent of the EEG reference choice, were used as the golden standard to infer the relative utility of different references on the ERP task-related effect. By comparison, REST reference provided a more integrated and reasonable result. These results were further confirmed by the results of fMRI activations and a corresponding EEG-only study. Thus, we recommend the REST, especially with a realistic head model, as the optimal reference method for ERP data analysis in simultaneous EEG-fMRI studies.

Redox artifacts in electrophysiological recordings

PubMed Central

Berman, Jonathan M.

2013-01-01

Electrophysiological techniques make use of Ag/AgCl electrodes that are in direct contact with cells or bath. In the bath, electrodes are exposed to numerous experimental conditions and chemical reagents that can modify electrode voltage. We examined voltage offsets created in Ag/AgCl electrodes by exposure to redox reagents used in electrophysiological studies. Voltage offsets were measured in reference to an electrode separated from the solution by an agar bridge. The reducing reagents Tris-2-carboxyethly-phosphine, dithiothreitol (DTT), and glutathione, as well as the oxidizing agent H2O2 used at experimentally relevant concentrations reacted with Ag in the electrodes to produce voltage offsets. Chloride ions and strong acids and bases produced offsets at millimolar concentrations. Electrolytic depletion of the AgCl layer, to replicate voltage clamp and sustained use, resulted in increased sensitivity to flow and DTT. Offsets were sensitive to electrode silver purity and to the amount and method of chloride deposition. For example, exposure to 10 μM DTT produced a voltage offset between 10 and 284 mV depending on the chloride deposition method. Currents generated by these offsets are significant and dependent on membrane conductance and by extension the expression of ion channels and may therefore appear to be biological in origin. These data demonstrate a new source of artifacts in electrophysiological recordings that can affect measurements obtained from a variety of experimental techniques from patch clamp to two-electrode voltage clamp. PMID:23344161

Evaluation of a Ag/Ag 2S reference electrode with long-term stability for electrochemistry in ionic liquids

DOE PAGES

Horwood, Corie; Stadermann, Michael

2018-02-08

We report on a reference electrode designed for use in ionic liquids, based on a silver wire coated with silver sulfide. The reference electrode potential is determined by the concentrations of Ag + and S 2-, which are established by the solubility of the Ag 2S coating on the Ag wire. While potential shifts of >100 mV during an experiment have been reported when using silver or platinum wire quasi-reference electrodes, the reference electrode reported here provides a stable potential over several months of experimental use. Additionally, our reference electrode can be prepared and used in a normal air atmosphere,more » and does not need to be assembled and used in a glovebox, or protected from light. In conclusion, the reference electrode has been characterized by voltammetry measurements of ferrocene and cobaltocenium hexafluorophosphate, and was found to slowly drift to more positive potentials at a rate of <1 mV/day for five of the six ionic liquids investigated.« less

Evaluation of a Ag/Ag 2S reference electrode with long-term stability for electrochemistry in ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horwood, Corie; Stadermann, Michael

We report on a reference electrode designed for use in ionic liquids, based on a silver wire coated with silver sulfide. The reference electrode potential is determined by the concentrations of Ag + and S 2-, which are established by the solubility of the Ag 2S coating on the Ag wire. While potential shifts of >100 mV during an experiment have been reported when using silver or platinum wire quasi-reference electrodes, the reference electrode reported here provides a stable potential over several months of experimental use. Additionally, our reference electrode can be prepared and used in a normal air atmosphere,more » and does not need to be assembled and used in a glovebox, or protected from light. In conclusion, the reference electrode has been characterized by voltammetry measurements of ferrocene and cobaltocenium hexafluorophosphate, and was found to slowly drift to more positive potentials at a rate of <1 mV/day for five of the six ionic liquids investigated.« less

Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations

PubMed Central

Meneses, Diogenes; Gunasekara, Dulan B.; Pichetsurnthorn, Pann; da Silva, José A. F.; de Abreu, Fabiane C.; Lunte, Susan M.

2015-01-01

In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration. PMID:25256669

The Corrosion Protection of Magnesium Alloy AZ31B

NASA Technical Reports Server (NTRS)

Danford, M. D.; Mendrek, M. J.; Mitchell, M. L.; Torres, P. D.

1997-01-01

Corrosion rates for bare and coated Magnesium alloy AZ31B have been measured. Two coatings, Dow-23(Trademark) and Tagnite(Trademark), have been tested by electrochemical methods and their effectiveness determined. Electrochemical methods employed were the scanning reference electrode technique (SRET), the polarization resistance technique (PR) and the electrochemical impedance spectroscopy technique (EIS). In addition, general corrosion and stress corrosion methods were employed to examine the effectiveness of the above coatings in 90 percent humidity. Results from these studies are presented.

Construction of Ag/AgCl Reference Electrode from Used Felt-Tipped Pen Barrel for Undergraduate Laboratory

ERIC Educational Resources Information Center

Inamdar, Shaukatali N.; Bhat, Mohsin A.; Haram, Santosh K.

2009-01-01

A reference electrode is one of the prerequisites of electrochemical investigations. Many electrodes are commercially available but are expensive and prone to accidental breakage by students. Here we report a simple, easy-to-fabricate, inexpensive, reliable, unbreakable, and reproducible Ag/AgCl reference electrode. The empty barrel of a…

Percutaneous Irreversible Electroporation of Locally Advanced Pancreatic Carcinoma Using the Dorsal Approach: A Case Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheffer, Hester J., E-mail: hj.scheffer@vumc.nl; Melenhorst, Marleen C. A. M., E-mail: m.melenhorst@vumc.nl; Vogel, Jantien A., E-mail: j.a.vogel@amc.uva.nl

Irreversible electroporation (IRE) is a novel image-guided ablation technique that is increasingly used to treat locally advanced pancreatic carcinoma (LAPC). We describe a 67-year-old male patient with a 5 cm stage III pancreatic tumor who was referred for IRE. Because the ventral approach for electrode placement was considered dangerous due to vicinity of the tumor to collateral vessels and duodenum, the dorsal approach was chosen. Under CT-guidance, six electrodes were advanced in the tumor, approaching paravertebrally alongside the aorta and inferior vena cava. Ablation was performed without complications. This case describes that when ventral electrode placement for pancreatic IRE is impaired,more » the dorsal approach could be considered alternatively.« less

Electrodes for solid state gas sensor

DOEpatents

Mukundan, Rangachary [Santa Fe, NM; Brosha, Eric L [Los Alamos, NM; Garzon, Fernando [Santa Fe, NM

2007-05-08

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

Electrodes for solid state gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukundan, Rangachary; Brosha, Eric L; Garzon, Fernando

2007-05-08

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within themore » die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.« less

Electrodes for solid state gas sensor

DOEpatents

Mukundan, Rangachary; Brosha, Eric L.; Garzon, Fernando

2003-08-12

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

Multi-functional sensor system for molten salt technologies

DOEpatents

Redey, Laszlo [Downers Grove, IL; Gourishankar, Karthick [Downers Grove, IL; Williamson, Mark A [Naperville, IL

2009-12-15

The present invention relates to a multi-functional sensor system that simultaneously measures cathode and anode electrode potentials, dissolved ion (i.e. oxide) concentration, and temperatures in an electrochemical cell. One embodiment of the invented system generally comprises: a reference(saturated) electrode, a reference(sensing) electrode, and a data acquisition system. Thermocouples are built into the two reference electrodes to provide important temperature information.

Improved Electrochemical Detection of Zinc Ions Using Electrode Modified with Electrochemically Reduced Graphene Oxide

PubMed Central

Kudr, Jiri; Richtera, Lukas; Nejdl, Lukas; Xhaxhiu, Kledi; Vitek, Petr; Rutkay-Nedecky, Branislav; Hynek, David; Kopel, Pavel; Adam, Vojtech; Kizek, Rene

2016-01-01

Increasing urbanization and industrialization lead to the release of metals into the biosphere, which has become a serious issue for public health. In this paper, the direct electrochemical reduction of zinc ions is studied using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The graphene oxide (GO) was fabricated using modified Hummers method and was electrochemically reduced on the surface of GCE by performing cyclic voltammograms from 0 to −1.5 V. The modification was optimized and properties of electrodes were determined using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The determination of Zn(II) was performed using differential pulse voltammetry technique, platinum wire as a counter electrode, and Ag/AgCl/3 M KCl reference electrode. Compared to the bare GCE the modified GCE/ERGO shows three times better electrocatalytic activity towards zinc ions, with an increase of reduction current along with a negative shift of reduction potential. Using GCE/ERGO detection limit 5 ng·mL−1 was obtained. PMID:28787832

Evaluation of excitation strategy with multi-plane electrical capacitance tomography sensor

NASA Astrophysics Data System (ADS)

Mao, Mingxu; Ye, Jiamin; Wang, Haigang; Zhang, Jiaolong; Yang, Wuqiang

2016-11-01

Electrical capacitance tomography (ECT) is an imaging technique for measuring the permittivity change of materials. Using a multi-plane ECT sensor, three-dimensional (3D) distribution of permittivity may be represented. In this paper, three excitation strategies, including single-electrode excitation, dual-electrode excitation in the same plane, and dual-electrode excitation in different planes are investigated by numerical simulation and experiment for two three-plane ECT sensors with 12 electrodes in total. In one sensor, the electrodes on the middle plane are in line with the others. In the other sensor, they are rotated 45° with reference to the other two planes. A linear back projection algorithm is used to reconstruct the images and a correlation coefficient is used to evaluate the image quality. The capacitance data and sensitivity distribution with each measurement strategy and sensor model are analyzed. Based on simulation and experimental results using noise-free and noisy capacitance data, the performance of the three strategies is evaluated.

Thermo-electrochemical instrumentation of cylindrical Li-ion cells

NASA Astrophysics Data System (ADS)

McTurk, Euan; Amietszajew, Tazdin; Fleming, Joe; Bhagat, Rohit

2018-03-01

The performance evaluation and optimisation of commercially available lithium-ion cells is typically based upon their full cell potential and surface temperature measurements, despite these parameters not being fully representative of the electrochemical processes taking place in the core of the cell or at each electrode. Several methods were devised to obtain the cell core temperature and electrode-specific potential profiles of cylindrical Li-ion cells. Optical fibres with Bragg Gratings were found to produce reliable core temperature data, while their small mechanical profile allowed for low-impact instrumentation method. A pure metallic lithium reference electrode insertion method was identified, avoiding interference with other elements of the cell while ensuring good contact, enabling in-situ observations of the per-electrode electrochemical responses. Our thermo-electrochemical instrumentation technique has enabled us to collect unprecedented cell data, and has subsequently been used in advanced studies exploring the real-world performance limits of commercial cells.

Effect of electrode material and design on sensitivity and selectivity for high temperature impedancemetric NOx sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, L Y; Glass, R S; Novak, R F

2009-09-23

Solid-state electrochemical sensors using two different sensing electrode compositions, gold and strontium-doped lanthanum manganite (LSM), were evaluated for gas phase sensing of NO{sub x} (NO and NO{sub 2}) using an impedance-metric technique. An asymmetric cell design utilizing porous YSZ electrolyte exposed both electrodes to the test gas (i.e., no reference gas). Sensitivity to less than 5 ppm NO and response/recovery times (10-90%) less than 10 s were demonstrated. Using an LSM sensing electrode, virtual identical sensitivity towards NO and NO{sub 2} was obtained, indicating that the equilibrium gas concentration was measured by the sensing electrode. In contrast, for cells employingmore » a gold sensing electrode the NO{sub x} sensitivity varied depending on the cell design: increasing the amount of porous YSZ electrolyte on the sensor surface produced higher NO{sub 2} sensitivity compared to NO. In order to achieve comparable sensitivity for both NO and NO{sub 2}, the cell with the LSM sensing electrode required operation at a lower temperature (575 C) than the cell with the gold sensing electrode (650 C). The role of surface reactions are proposed to explain the differences in NO and NO{sub 2} selectivity using the two different electrode materials.« less

Study of the optimum level of electrode placement for the evaluation of absolute lung resistivity with the Mk3.5 EIT system.

PubMed

Nebuya, S; Noshiro, M; Yonemoto, A; Tateno, S; Brown, B H; Smallwood, R H; Milnes, P

2006-05-01

Inter-subject variability has caused the majority of previous electrical impedance tomography (EIT) techniques to focus on the derivation of relative or difference measures of in vivo tissue resistivity. Implicit in these techniques is the requirement for a reference or previously defined data set. This study assesses the accuracy and optimum electrode placement strategy for a recently developed method which estimates an absolute value of organ resistivity without recourse to a reference data set. Since this measurement of tissue resistivity is absolute, in Ohm metres, it should be possible to use EIT measurements for the objective diagnosis of lung diseases such as pulmonary oedema and emphysema. However, the stability and reproducibility of the method have not yet been investigated fully. To investigate these problems, this study used a Sheffield Mk3.5 system which was configured to operate with eight measurement electrodes. As a result of this study, the absolute resistivity measurement was found to be insensitive to the electrode level between 4 and 5 cm above the xiphoid process. The level of the electrode plane was varied between 2 cm and 7 cm above the xiphoid process. Absolute lung resistivity in 18 normal subjects (age 22.6 +/- 4.9, height 169.1 +/- 5.7 cm, weight 60.6 +/- 4.5 kg, body mass index 21.2 +/- 1.6: mean +/- standard deviation) was measured during both normal and deep breathing for 1 min. Three sets of measurements were made over a period of several days on each of nine of the normal male subjects. No significant differences in absolute lung resistivity were found, either during normal tidal breathing between the electrode levels of 4 and 5 cm (9.3 +/- 2.4 Omega m, 9.6 +/- 1.9 Omega m at 4 and 5 cm, respectively: mean +/- standard deviation) or during deep breathing between the electrode levels of 4 and 5 cm (10.9 +/- 2.9 Omega m and 11.1 +/- 2.3 Omega m, respectively: mean +/- standard deviation). However, the differences in absolute lung resistivity between normal and deep tidal breathing at the same electrode level are significant. No significant difference was found in the coefficient of variation between the electrode levels of 4 and 5 cm (9.5 +/- 3.6%, 8.5 +/- 3.2% at 4 and 5 cm, respectively: mean +/- standard deviation in individual subjects). Therefore, the electrode levels of 4 and 5 cm above the xiphoid process showed reasonable reliability in the measurement of absolute lung resistivity both among individuals and over time.

Early detection of Candida albicans biofilms at porous electrodes.

PubMed

Congdon, Robert B; Feldberg, Alexander S; Ben-Yakar, Natalie; McGee, Dennis; Ober, Christopher; Sammakia, Bahgat; Sadik, Omowunmi A

2013-02-15

We describe the development of an electrochemical sensor for early detection of biofilm using Candida albicans. The electrochemical sensor used the ability of biofilms to accept electrons from redox mediators relative to the number of metabolically active cells present. Cyclic voltammetry and differential pulse voltammetry techniques were used to monitor the redox reaction of K(3)Fe(CN)(6) at porous reticulated vitreous carbon (RVC) (238.7 cm(2)) working electrodes versus Ag/AgCl reference. A shift in the peak potential occurred after 12 h of film growth, which is attributed to the presence of C. albicans. Moreover, the intensity of the ferricyanide reduction peak first increased as C. albicans deposited onto the porous electrodes at various growth times. The peak current subsequently decreased at extended periods of growth of 48 h. The reduction in peak current was attributed to the biofilm reaching its maximum growth thickness, which correlated with the maximum number of metabolically active cells. The observed diffusion coefficients for the bare RVC and biofilm-coated electrodes were 2.2 × 10(-3) and 7.0 × 10(-6) cm(2)/s, respectively. The increase in diffusivity from the bare electrode to the biofilm-coated electrode indicated some enhancement of electron transfer mediated by the biofilm to the porous electrode. Verification of the growth of biofilm was achieved using scanning electron microcopy and laser scanning confocal imaging microscopy. Validation with conventional plating techniques confirmed that the correlation (R(2) = 0.9392) could be achieved between the electrochemical sensors data and colony-forming units. Copyright © 2012 Elsevier Inc. All rights reserved.

Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices

PubMed Central

Nguyen, Cuong M.; Rao, Smitha; Yang, Xuesong; Dubey, Souvik; Mays, Jeffrey; Cao, Hung; Chiao, Jung-Chih

2015-01-01

Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 μm × 500 μm, and 100 μm × 100 μm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. PMID:25686309

Performance evaluation of thermally treated graphite felt electrodes for vanadium redox flow battery and their four-point single cell characterization

NASA Astrophysics Data System (ADS)

Mazúr, P.; Mrlík, J.; Beneš, J.; Pocedič, J.; Vrána, J.; Dundálek, J.; Kosek, J.

2018-03-01

In our contribution we study the electrocatalytic effect of oxygen functionalization of thermally treated graphite felt on kinetics of electrode reactions of vanadium redox flow battery. Chemical and morphological changes of the felts are analysed by standard physico-chemical characterization techniques. A complex method four-point method is developed and employed for characterization of the felts in a laboratory single-cell. The method is based on electrochemical impedance spectroscopy and load curves measurements of positive and negative half-cells using platinum wire pseudo-reference electrodes. The distribution of ohmic and faradaic losses within a single-cell is evaluated for both symmetric and asymmetric electrode set-up with respect to the treatment conditions. Positive effect of oxygen functionalization is observed only for negative electrode, whereas kinetics of positive electrode reaction is almost unaffected by the treatment. This is in a contradiction to the results of typically employed cyclovoltammetric characterization which indicate that both electrodes are enhanced by the treatment to a similar extent. The developed four-point characterization method can be further used e.g., for the component screening and in-situ durability studies on single-cell scale redox flow batteries of various chemistries.

Silver-silver sulfate reference electrodes for use in lead-acid batteries

NASA Astrophysics Data System (ADS)

Ruetschi, Paul

Electrochemical properties of silver-silver sulfate reference electrodes for lead-acid batteries are described, and the following possible applications discussed: Determination of individual capacities of positive and negative plates. Monitoring individual electrode behavior during deep discharge and cell reversal. Optimization charge or discharge parameters, by controlling the current such that pre-determined limits of positive or negative half-cell potential are respected. Observation of acid concentration differences, for example due to acid stratification, by measuring diffusion potentials (concentration-cell voltages). Detection of defective cells, and defective plate sets, in a string of cells, at the end of their service life. Silver-silver sulfate reference electrodes, permanently installed in lead-acid cells, may be a means to improve battery management, and therewith to improve reliability and service life. In vented batteries, reference electrodes may be used to limit positive plate polarization during charge, or float-charge. Limiting the positive half-cell potential to an upper, pre-set value would permit to keep anodic corrosion as low as possible. During cycling, discharge could be terminated when the half-cell potential of the positive electrode has dropped to a pre-set limit. This would prevent excessive discharge of the positive electrodes, which could result in an improvement of cycle life. In valve-regulated batteries, reference electrodes may be used to adjust float-charge conditions such as to assure sufficient cathodic polarization of the negative electrodes, in order to avoid sulfation. The use of such reference electrodes could be beneficial particularly in multi-cell batteries, with overall voltages above 12 V, operated in a partial-state-of-charge.

A review study of (bio)sensor systems based on conducting polymers.

PubMed

Ates, Murat

2013-05-01

This review article concentrates on the electrochemical biosensor systems with conducting polymers. The area of electro-active polymers confined to different electrode surfaces has attracted great attention. Polymer modified carbon substrate electrodes can be designed through polymer screening to provide tremendous improvements in sensitivity, selectivity, stability and reproducibility of the electrode response to detect a variety of analytes. The electro-active films have been used to entrap different enzymes and/or proteins at the electrode surface, but without obvious loss of their bioactivity for the development of biosensors. Electropolymerization is a well-known technique used to immobilize biomaterials to the modified electrode surface. Polymers might be covalently bonding to enzymes or proteins; therefore, thickness, permeation and charge transport characteristics of the polymeric films can be easily and precisely controlled by modulating the electrochemical parameters for various electrochemical techniques, such as chronoamperometry, chronopotentiometry, cyclic voltammetry, and differential pulse voltammetry. This review article is divided into three main parts as given in the table of contents related to the immobilization process of some important conducting polymers, polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polycarbazole, polyaniline, polyphenol, poly(o-phenylenediamine), polyacetylene, polyfuran and their derivatives. A total of 216 references are cited in this review article. The literature reviewed covers a 7 year period beginning from 2005. Copyright © 2013 Elsevier B.V. All rights reserved.

Direct electrochemical reduction of metal-oxides

DOEpatents

Redey, Laszlo I.; Gourishankar, Karthick

2003-01-01

A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

Electrocatalytic cermet sensor

DOEpatents

Shoemaker, E.L.; Vogt, M.C.

1998-06-30

A sensor is described for O{sub 2} and CO{sub 2} gases. The gas sensor includes a plurality of layers driven by a cyclic voltage to generate a unique plot characteristic of the gas in contact with the sensor. The plurality of layers includes an alumina substrate, a reference electrode source of anions, a lower electrical reference electrode of Pt coupled to the reference source of anions, a solid electrolyte containing tungsten and coupled to the lower reference electrode, a buffer layer for preventing flow of Pt ions into the solid electrolyte and an upper catalytically active Pt electrode coupled to the buffer layer. 16 figs.

Electrocatalytic cermet sensor

DOEpatents

Shoemaker, Erika L.; Vogt, Michael C.

1998-01-01

A sensor for O.sub.2 and CO.sub.2 gases. The gas sensor includes a plurality of layers driven by a cyclic voltage to generate a unique plot characteristic of the gas in contact with the sensor. The plurality of layers includes an alumina substrate, a reference electrode source of anions, a lower electrical reference electrode of Pt coupled to the reference source of anions, a solid electrolyte containing tungsten and coupled to the lower reference electrode, a buffer layer for preventing flow of Pt ions into the solid electrolyte and an upper catalytically active Pt electrode coupled to the buffer layer.

Unified Bayesian Estimator of EEG Reference at Infinity: rREST (Regularized Reference Electrode Standardization Technique).

PubMed

Hu, Shiang; Yao, Dezhong; Valdes-Sosa, Pedro A

2018-01-01

The choice of reference for the electroencephalogram (EEG) is a long-lasting unsolved issue resulting in inconsistent usages and endless debates. Currently, both the average reference (AR) and the reference electrode standardization technique (REST) are two primary, apparently irreconcilable contenders. We propose a theoretical framework to resolve this reference issue by formulating both (a) estimation of potentials at infinity, and (b) determination of the reference, as a unified Bayesian linear inverse problem, which can be solved by maximum a posterior estimation. We find that AR and REST are very particular cases of this unified framework: AR results from biophysically non-informative prior; while REST utilizes the prior based on the EEG generative model. To allow for simultaneous denoising and reference estimation, we develop the regularized versions of AR and REST, named rAR and rREST, respectively. Both depend on a regularization parameter that is the noise to signal variance ratio. Traditional and new estimators are evaluated with this framework, by both simulations and analysis of real resting EEGs. Toward this end, we leverage the MRI and EEG data from 89 subjects which participated in the Cuban Human Brain Mapping Project. Generated artificial EEGs-with a known ground truth, show that relative error in estimating the EEG potentials at infinity is lowest for rREST. It also reveals that realistic volume conductor models improve the performances of REST and rREST. Importantly, for practical applications, it is shown that an average lead field gives the results comparable to the individual lead field. Finally, it is shown that the selection of the regularization parameter with Generalized Cross-Validation (GCV) is close to the "oracle" choice based on the ground truth. When evaluated with the real 89 resting state EEGs, rREST consistently yields the lowest GCV. This study provides a novel perspective to the EEG reference problem by means of a unified inverse solution framework. It may allow additional principled theoretical formulations and numerical evaluation of performance.

Mapping the vestibular evoked myogenic potential (VEMP).

PubMed

Colebatch, James G

2012-01-01

Effects of different electrode placements and indifferent electrodes were investigated for the vestibular evoked myogenic potential (VEMP) recorded from the sternocleidomastoid muscle (SCM). In 5 normal volunteers, the motor point of the left SCM was identified and an electrode placed there. A grid of 7 additional electrodes was laid out, along and across the SCM, based upon the location of the motor point. One reference electrode was placed over the sternoclavicular joint and another over C7. There were clear morphological changes with differing recording sites and for the two reference electrodes, but the earliest and largest responses were recorded from the motor point. The C7 reference affected the level of rectified EMG and was associated with an initial negativity in some electrodes. The latencies of the p13 potentials increased with distance from the motor point but the n23 latencies did not. Thus the p13 potential behaved as a travelling wave whereas the n23 behaved as a standing wave. The C7 reference may be contaminated by other evoked myogenic activity. Ideally recordings should be made with an active electrode over the motor point.

Multifunctional reference electrode

DOEpatents

Redey, Laszlo; Vissers, Donald R.

1983-01-01

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Multifunctional reference electrode

DOEpatents

Redey, L.; Vissers, D.R.

1981-12-30

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell are described. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Enhanced hydrogen storage capacity of Ni/Sn-coated MWCNT nanocomposites

NASA Astrophysics Data System (ADS)

Varshoy, Shokufeh; Khoshnevisan, Bahram; Behpour, Mohsen

2018-02-01

The hydrogen storage capacity of Ni-Sn, Ni-Sn/multi-walled carbon nanotube (MWCNT) and Ni/Sn-coated MWCNT electrodes was investigated by using a chronopotentiometry method. The Sn layer was electrochemically deposited inside pores of nanoscale Ni foam. The MWCNTs were put on the Ni-Sn foam with nanoscale porosities using an electrophoretic deposition method and coated with Sn nanoparticles by an electroplating process. X-ray diffraction and energy dispersive spectroscopy results indicated that the Sn layer and MWCNTs are successfully deposited on the surface of Ni substrate. On the other hand, a field-emission scanning electron microscopy technique revealed the morphology of resulting Ni foam, Ni-Sn and Ni-Sn/MWCNT electrodes. In order to measure the hydrogen adsorption performed in a three electrode cell, the Ni-Sn, Ni-Sn/MWCNT and Ni/Sn-coated MWCNT electrodes were used as working electrodes whereas Pt and Ag/AgCl electrodes were employed as counter and reference electrodes, respectively. Our results on the discharge capacity in different electrodes represent that the Ni/Sn-coated MWCNT has a maximum discharge capacity of ˜30 000 mAh g-1 for 20 cycles compared to that of Ni-Sn/MWCNT electrodes for 15 cycles (˜9500 mAh g-1). By increasing the number of cycles in a constant current, the corresponding capacity increases, thereby reaching a constant amount for 20 cycles.

Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

NASA Astrophysics Data System (ADS)

Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

2016-09-01

The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

Junction Potentials Bias Measurements of Ion Exchange Membrane Permselectivity.

PubMed

Kingsbury, Ryan S; Flotron, Sophie; Zhu, Shan; Call, Douglas F; Coronell, Orlando

2018-04-17

Ion exchange membranes (IEMs) are versatile materials relevant to a variety of water and waste treatment, energy production, and industrial separation processes. The defining characteristic of IEMs is their ability to selectively allow positive or negative ions to permeate, which is referred to as permselectivity. Measured values of permselectivity that equal unity (corresponding to a perfectly selective membrane) or exceed unity (theoretically impossible) have been reported for cation exchange membranes (CEMs). Such nonphysical results call into question our ability to correctly measure this crucial membrane property. Because weighing errors, temperature, and measurement uncertainty have been shown to not explain these anomalous permselectivity results, we hypothesized that a possible explanation are junction potentials that occur at the tips of reference electrodes. In this work, we tested this hypothesis by comparing permselectivity values obtained from bare Ag/AgCl wire electrodes (which have no junction) to values obtained from single-junction reference electrodes containing two different electrolytes. We show that permselectivity values obtained using reference electrodes with junctions were greater than unity for CEMs. In contrast, electrodes without junctions always produced permselectivities lower than unity. Electrodes with junctions also resulted in artificially low permselectivity values for AEMs compared to electrodes without junctions. Thus, we conclude that junctions in reference electrodes introduce two biases into results in the IEM literature: (i) permselectivity values larger than unity for CEMs and (ii) lower permselectivity values for AEMs compared to those for CEMs. These biases can be avoided by using electrodes without a junction.

How Different EEG References Influence Sensor Level Functional Connectivity Graphs

PubMed Central

Huang, Yunzhi; Zhang, Junpeng; Cui, Yuan; Yang, Gang; He, Ling; Liu, Qi; Yin, Guangfu

2017-01-01

Highlights: Hamming Distance is applied to distinguish the difference of functional connectivity networkThe orientations of sources are testified to influence the scalp Functional Connectivity Graph (FCG) from different references significantlyREST, the reference electrode standardization technique, is proved to have an overall stable and excellent performance in variable situations. The choice of an electroencephalograph (EEG) reference is a practical issue for the study of brain functional connectivity. To study how EEG reference influence functional connectivity estimation (FCE), this study compares the differences of FCE resulting from the different references such as REST (the reference electrode standardization technique), average reference (AR), linked mastoids (LM), and left mastoid references (LR). Simulations involve two parts. One is based on 300 dipolar pairs, which are located on the superficial cortex with a radial source direction. The other part is based on 20 dipolar pairs. In each pair, the dipoles have various orientation combinations. The relative error (RE) and Hamming distance (HD) between functional connectivity matrices of ideal recordings and that of recordings obtained with different references, are metrics to compare the differences of the scalp functional connectivity graph (FCG) derived from those two kinds of recordings. Lower RE and HD values imply more similarity between the two FCGs. Using the ideal recording (IR) as a standard, the results show that AR, LM and LR perform well only in specific conditions, i.e., AR performs stable when there is no upward component in sources' orientation. LR achieves desirable results when the sources' locations are away from left ear. LM achieves an indistinct difference with IR, i.e., when the distribution of source locations is symmetric along the line linking the two ears. However, REST not only achieves excellent performance for superficial and radial dipolar sources, but also achieves a stable and robust performance with variable source locations and orientations. Benefitting from the stable and robust performance of REST vs. other reference methods, REST might best recover the real FCG of EEG. Thus, REST based FCG may be a good candidate to compare the FCG of EEG based on different references from different labs. PMID:28725175

Determination of set potential voltages for cucumber mosaic virus detection using screen printed carbon electrode

NASA Astrophysics Data System (ADS)

Uda, M. N. A.; Hasfalina, C. M.; Samsuzana, A. A.; Faridah, S.; Rafidah A., R.; Hashim, U.; Ariffin, Shahrul A. B.; Gopinath, Subash C. B.

2017-03-01

Cucumber Mosaic Virus (CMV) is a most dangerous pathogen among the cucurbit plant which it striking cucumbers, zucchinis, squashes, watermelons but it also striking to non-cucurbit such as peppers, tobaccos, celeries, beans and tomatoes. Symptoms shown by this virus when they starting to strike are very significant and at the end can kill the hosts they infected. In order to detect these viruses, biosensor such as screen-printed carbon electrode (SPCE) is developed and fixes a set potential voltage is defined using Chronoamperometry (CM) immunosensor technique. For short introduction, CM is a process which is a constant applied potential voltage between the working and reference electrode is maintained in order to create an electrons transfer for the oxidation or reduction species taking place at the surface of working electrode is measured and in this manuscript, complete details about measurement were used to finding the stable set potential voltages will be pointed out.

Degradation Study by Start-Up/Shut-Down Cycling of Superhydrophobic Electrosprayed Catalyst Layers Using a Localized Reference Electrode Technique.

PubMed

Ferreira-Aparicio, Paloma; Chaparro, Antonio M; Folgado, M Antonia; Conde, Julio J; Brightman, Edward; Hinds, Gareth

2017-03-29

Degradation of a polymer electrolyte membrane fuel cell (PEMFC) with electrosprayed cathode catalyst layers is investigated during cyclic start-up and shut-down events. The study is carried out within a single cell incorporating an array of reference electrodes that enables measurement of cell current as a function of local cathode potential (localized polarization curves). Accelerated degradation of the cell by start-up/shut-down cycling gives rise to inhomogeneous performance loss, which is more severe close to the gas outlet and occurs predominantly during start-up. The degradation consists primarily of loss of cathode catalyst activity and increase in cell internal resistance, which is attributed to carbon corrosion and Pt aggregation in both anode and cathode. Cells with an electrosprayed cathode catalyst layer show lower degradation rates during the first 100 cycles, compared with those of a conventional gas diffusion electrode. This difference in behavior is attributed to the high hydrophobicity of the electrosprayed catalyst layer microstructure, which retards the kinetics of corrosion of the carbon support. In the long term, however, the degradation rate is dominated by the Pt/C ratio in the cathode catalyst layer.

Method and apparatus for electron-only radiation detectors from semiconductor materials

DOEpatents

Lund, James C.

2000-01-01

A system for obtaining improved resolution in room temperature semiconductor radiation detectors such as CdZnTe and Hgl.sub.2, which exhibit significant hole-trapping. A electrical reference plane is established about the perimeter of a semiconductor crystal and disposed intermediately between two oppositely biased end electrodes. The intermediate reference plane comprises a narrow strip of wire in electrical contact with the surface of the crystal, biased at a potential between the end electrode potentials and serving as an auxiliary electrical reference for a chosen electrode--typically the collector electrode for the more mobile charge carrier. This arrangement eliminates the interfering effects of the less mobile carriers as these are gathered by their electrode collector.

Capillary reference half-cell

DOEpatents

Hall, Stephen H.

1996-01-01

The present invention is a reference half-cell electrode wherein intermingling of test fluid with reference fluid does not affect the performance of the reference half-cell over a long time. This intermingling reference half-cell may be used as a single or double junction submersible or surface reference electrode. The intermingling reference half-cell relies on a capillary tube having a first end open to reference fluid and a second end open to test fluid wherein the small diameter of the capillary tube limits free motion of fluid within the capillary to diffusion. The electrode is placed near the first end of the capillary in contact with the reference fluid. The method of operation of the present invention begins with filling the capillary tube with a reference solution. After closing the first end of the capillary, the capillary tube may be fully submerged or partially submerged with the second open end inserted into test fluid. Since the electrode is placed near the first end of the capillary, and since the test fluid may intermingle with the reference fluid through the second open end only by diffusion, this intermingling capillary reference half-cell provides a stable voltage potential for long time periods.

Capillary reference half-cell

DOEpatents

Hall, S.H.

1996-02-13

The present invention is a reference half-cell electrode wherein intermingling of test fluid with reference fluid does not affect the performance of the reference half-cell over a long time. This intermingling reference half-cell may be used as a single or double junction submersible or surface reference electrode. The intermingling reference half-cell relies on a capillary tube having a first end open to reference fluid and a second end open to test fluid wherein the small diameter of the capillary tube limits free motion of fluid within the capillary to diffusion. The electrode is placed near the first end of the capillary in contact with the reference fluid. The method of operation of the present invention begins with filling the capillary tube with a reference solution. After closing the first end of the capillary, the capillary tube may be fully submerged or partially submerged with the second open end inserted into test fluid. Since the electrode is placed near the first end of the capillary, and since the test fluid may intermingle with the reference fluid through the second open end only by diffusion, this intermingling capillary reference half-cell provides a stable voltage potential for long time periods. 11 figs.

Enhanced electrodes for solid state gas sensors

DOEpatents

Garzon, Fernando H.; Brosha, Eric L.

2001-01-01

A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

Synthetic battery cycling techniques

NASA Technical Reports Server (NTRS)

Leibecki, H. F.; Thaller, L. H.

1982-01-01

Synthetic battery cycling makes use of the fast growing capability of computer graphics to illustrate some of the basic characteristics of operation of individual electrodes within an operating electrochemical cell. It can also simulate the operation of an entire string of cells that are used as the energy storage subsystem of a power system. The group of techniques that as a class have been referred to as Synthetic Battery Cycling is developed in part to try to bridge the gap of understanding that exists between single cell characteristics and battery system behavior.

Effects of the choice of reference on the selectivity of a multi-contact nerve cuff electrode.

PubMed

Koh, Ryan G L; Zariffa, Jose

2016-08-01

Tripolar referencing is typically used in nerve cuff electrode recordings due to its ability to maximize the signal-to-noise ratio of contacts at the centre, but this may not be the optimal choice for a multi-contact nerve cuff consisting of contacts in off-centre rings. We conducted a simulation study to compare the effects of 3 different reference types on the recording selectivity of a multi-contact nerve cuff: the tripolar reference (TPR), common average reference (CAR), and multiple tripolar references based on consecutive groups of 3 rings (cTPR). For this purpose, we introduce a novel measure called the contact information metric (CIM). Selectivity was tested in 2 noise settings, one in which white Gaussian noise was added inside the nerve cuff electrode and the other in which electromyogram (EMG) noise was added outside the nerve cuff electrode. The mean CIMs values calculated for the best 8 contacts were 3.42±6.25, 2.70±3.37, and 3.65±1.90 for the TPR, the CAR and the cTPR, respectively, in the case of EMG noise added outside the nerve cuff electrode. This study shows that the use of cTPR reference is the optimal choice for selectivity when using a multi-contact nerve cuff electrode which contains off-centre rings.

On the design of capacitive sensors using flexible electrodes for multipurpose measurements

NASA Astrophysics Data System (ADS)

Thibault, Pierre; Diribarne, Pantxo; Fournier, Thierry; Perraud, Sylvain; Puech, Laurent; Wolf, P.-Etienne; Rousset, Bernard; Vallcorba, Roser

2007-04-01

This article evaluates the potential of capacitive measurements using flexible electrodes to access various physical quantities. These electrodes are made of a thin metallic film, typical thickness 0.2 μm, evaporated on a plastic substrate. Their large flexibility enables them to be mounted in complex geometries such as curved surfaces. In the configuration of planar condensers, using a very sensitive commercial capacitive bridge and a three-terminal measurement method, several measurements are presented. A relative resolution of 10-8 for the thermal expansion of samples is obtained at low temperature in a differential configuration. The same technique adopted for pressure gauge measurements at low temperature led to a typical 0.1 Pa resolution over a dynamic range of 104 Pa. In the configuration of interleaved electrodes, condensers have been used to measure wetting by either bulk liquid helium or by thin continuous helium films in a cylindrical pipe. Both experimental and numerical evidence is provided, showing that the close proximity of a reference ground potential significantly increases the relative sensitivity to fluid wetting. Further, interleaved electrodes can be used to access both the area that is covered by a liquid film but also to determine the thickness of this film, provided it is comparable to the periodicity of the electrode pattern.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branch, Shirmir D.; Lines, Amanda M.; Lynch, John

The electrochemical and spectroelectrochemical applications of an optically transparent thin film electrode chip are investigated. The working electrode is composed of indium tin oxide (ITO); the counter and quasi-reference electrodes are composed of platinum. The stability of the platinum quasi-reference electrode is modified by coating it with a planar, solid state Ag/AgCl layer. The Ag/AgCl reference is characterized with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Open circuit potential measurements indicate that the potential of the planar Ag/AgCl electrode varies a maximum of 20 mV over four days. Cyclic voltammetry measurements show that the electrode chip is comparable to amore » standard electrochemical cell. Randles-Sevcik analysis of 10 mM K3[Fe(CN)6] in 0.1 M KCl using the electrode chip shows a diffusion coefficient of 1.59 × 10-6 cm2/s, in comparison to the standard electrochemical cell value of 2.38 × 10-6 cm2/s. By using the electrode chip in an optically transparent thin layer electrode (OTTLE), the spectroelectrochemical modulation of [Ru(bpy)3]2+ florescence was demonstrated, achieving a detection limit of 36 nM.« less

Actinide-ion sensor

DOEpatents

Li, Shelly X; Jue, Jan-fong; Herbst, Ronald Scott; Herrmann, Steven Douglas

2015-01-13

An apparatus for the real-time, in-situ monitoring of actinide-ion concentrations. A working electrolyte is positioned within the interior of a container. The working electrolyte is separated from a reference electrolyte by a separator. A working electrode is at least partially in contact with the working electrolyte. A reference electrode is at least partially in contact with the reference electrolyte. A voltmeter is electrically connected to the working electrode and the reference electrode. The working electrolyte comprises an actinide-ion of interest. The separator is ionically conductive to the actinide-ion of interest. The separator comprises an actinide, Zr, and Nb. Preferably, the actinide of the separator is Am or Np, more preferably Pu. In one embodiment, the actinide of the separator is the actinide of interest. In another embodiment, the separator further comprises P and O.

Unified Bayesian Estimator of EEG Reference at Infinity: rREST (Regularized Reference Electrode Standardization Technique)

PubMed Central

Hu, Shiang; Yao, Dezhong; Valdes-Sosa, Pedro A.

2018-01-01

The choice of reference for the electroencephalogram (EEG) is a long-lasting unsolved issue resulting in inconsistent usages and endless debates. Currently, both the average reference (AR) and the reference electrode standardization technique (REST) are two primary, apparently irreconcilable contenders. We propose a theoretical framework to resolve this reference issue by formulating both (a) estimation of potentials at infinity, and (b) determination of the reference, as a unified Bayesian linear inverse problem, which can be solved by maximum a posterior estimation. We find that AR and REST are very particular cases of this unified framework: AR results from biophysically non-informative prior; while REST utilizes the prior based on the EEG generative model. To allow for simultaneous denoising and reference estimation, we develop the regularized versions of AR and REST, named rAR and rREST, respectively. Both depend on a regularization parameter that is the noise to signal variance ratio. Traditional and new estimators are evaluated with this framework, by both simulations and analysis of real resting EEGs. Toward this end, we leverage the MRI and EEG data from 89 subjects which participated in the Cuban Human Brain Mapping Project. Generated artificial EEGs—with a known ground truth, show that relative error in estimating the EEG potentials at infinity is lowest for rREST. It also reveals that realistic volume conductor models improve the performances of REST and rREST. Importantly, for practical applications, it is shown that an average lead field gives the results comparable to the individual lead field. Finally, it is shown that the selection of the regularization parameter with Generalized Cross-Validation (GCV) is close to the “oracle” choice based on the ground truth. When evaluated with the real 89 resting state EEGs, rREST consistently yields the lowest GCV. This study provides a novel perspective to the EEG reference problem by means of a unified inverse solution framework. It may allow additional principled theoretical formulations and numerical evaluation of performance. PMID:29780302

A highly efficient microfluidic nano biochip based on nanostructured nickel oxide.

PubMed

Ali, Md Azahar; Solanki, Pratima R; Patel, Manoj K; Dhayani, Hemant; Agrawal, Ved Varun; John, Renu; Malhotra, Bansi D

2013-04-07

We present results of the studies relating to fabrication of a microfluidic biosensor chip based on nickel oxide nanorods (NRs-NiO) that is capable of directly measuring the concentration of total cholesterol in human blood through electrochemical detection. Using this chip we demonstrate, with high reliability and in a time efficient manner, the detection of cholesterol present in buffer solutions at clinically relevant concentrations. The microfluidic channel has been fabricated onto a nickel oxide nanorod-based electrode co-immobilized with cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) that serves as the working electrode. Bare indium tin oxide served as the counter electrode. A Ag/AgCl wire introduced to the outlet of the microchannel acts as a reference electrode. The fabricated NiO nanorod-based electrode has been characterized using X-ray diffraction, Raman spectroscopy, HR-TEM, FT-IR, UV-visible spectroscopy and electrochemical techniques. The presented NRs-NiO based microfluidic sensor exhibits linearity in the range of 1.5-10.3 mM, a high sensitivity of 0.12 mA mM(-1) cm(-2) and a low value of 0.16 mM of the Michaelis-Menten constant (Km).

A Comparative Study of Standardized Infinity Reference and Average Reference for EEG of Three Typical Brain States

PubMed Central

Zheng, Gaoxing; Qi, Xiaoying; Li, Yuzhu; Zhang, Wei; Yu, Yuguo

2018-01-01

The choice of different reference electrodes plays an important role in deciphering the functional meaning of electroencephalography (EEG) signals. In recent years, the infinity zero reference using the reference electrode standard technique (REST) has been increasingly applied, while the average reference (AR) was generally advocated as the best available reference option in previous classical EEG studies. Here, we designed EEG experiments and performed a direct comparison between the influences of REST and AR on EEG-revealed brain activity features for three typical brain behavior states (eyes-closed, eyes-open and music-listening). The analysis results revealed the following observations: (1) there is no significant difference in the alpha-wave-blocking effect during the eyes-open state compared with the eyes-closed state for both REST and AR references; (2) there was clear frontal EEG asymmetry during the resting state, and the degree of lateralization under REST was higher than that under AR; (3) the global brain functional connectivity density (FCD) and local FCD have higher values for REST than for AR under different behavior states; and (4) the value of the small-world network characteristic in the eyes-closed state is significantly (in full, alpha, beta and gamma frequency bands) higher than that in the eyes-open state, and the small-world effect under the REST reference is higher than that under AR. In addition, the music-listening state has a higher small-world network effect than the eyes-closed state. The above results suggest that typical EEG features might be more clearly presented by applying the REST reference than by applying AR when using a 64-channel recording. PMID:29593490

Real-Time Monitoring of Cellular Bioenergetics with a Multi-Analyte Screen-Printed Electrode

PubMed Central

McKenzie, Jennifer R.; Cognata, Andrew C.; Davis, Anna N.; Wikswo, John P.; Cliffel, David E.

2016-01-01

Real-time monitoring of changes to cellular bioenergetics can provide new insights into mechanisms of action for disease and toxicity. This work describes the development of a multi-analyte screen-printed electrode for the detection of analytes central to cellular bioenergetics: glucose, lactate, oxygen, and pH. Platinum screen-printed electrodes were designed in-house and printed by Pine Research Instrumentation. Electrochemical plating techniques were used to form quasi-reference and pH electrodes. A Dimatix materials inkjet printer was used to deposit enzyme and polymer films to form sensors for glucose, lactate, and oxygen. These sensors were evaluated in bulk solution and microfluidic environments, and found to behave reproducibly and possess a lifetime of up to six weeks. Linear ranges and limits of detection for enzyme-based sensors were found to have an inverse relationship with enzyme loading, and iridium oxide pH sensors were found to have super-Nernstian responses. Preliminary measurements where the sensor was enclosed within a microfluidic channel with RAW 264.7 macrophages were performed to demonstrate the sensors’ capabilities for performing real-time microphysiometry measurements. PMID:26125545

The electrochemistry of "solid/water" interfaces involved in PEM-H2O reactors: part I. The "Pt/water" interfaces.

PubMed

Wang, Qiang; Cha, Chuan-Sin; Lu, Juntao; Zhuang, Lin

2009-01-28

The nature and properties of Pt surfaces in contact with pure water in PEM-H2O reactors were mimetically studied by employing CV measurements with microelectrode techniques. These "Pt/water" interfaces were found to be electrochemically polarizable, and the local interfacial potential relative to reversible hydrogen electrode (RHE) potential in pure water is numerically the same as the potential value measured against a RHE in contact with PEM as the reference electrode. However, the structural parameters of the electric double layer at the "Pt/water" interfaces can be quite different from those at the "Pt/PEM" interfaces, and the kinetics of electrode processes could be seriously affected by the structure of electric double layer in pure water media. Besides, there is active diffusional flow of intermediates of electrode reactions between the "Pt/water" and the "Pt/PEM" interfaces, thus facilitating the active involvement of the "Pt/water" interfaces in the current-generation mechanism of PEM fuel cells and other types of PEM-H2O reactors.

Fabrication and Characterization of a Stabilized Thin Film Ag/AgCl Reference Electrode Modified with Self-Assembled Monolayer of Alkane Thiol Chains for Rapid Biosensing Applications.

PubMed

Rahman, Tanzilur; Ichiki, Takanori

2017-10-13

The fabrication of miniaturized electrical biosensing devices can enable the rapid on-chip detection of biomarkers such as miRNA molecules, which is highly important in early-stage cancer detection. The challenge in realizing such devices remains in the miniaturization of the reference electrodes, which is an integral part of electrical detection. Here, we report on a novel thin film Ag/AgCl reference electrode (RE) that has been fabricated on top of a Au-sputtered glass surface, which was coated with a self-assembled monolayer (SAM) of 6-mercepto-1-hexanol (MCH). The electrode showed very little measurement deviation (-1.5 mv) from a commercial Ag/AgCl reference electrode and exhibited a potential drift of only ± 0.2 mV/h. In addition, the integration of this SAM-modified microfabricated thin film RE enabled the rapid detection (<30 min) of miRNA (let-7a). The electrode can be integrated seamlessly into a microfluidic device, allowing the highly stable and fast measurement of surface potential and is expected to be very useful for the development of miniature electrical biosensors.

Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

NASA Astrophysics Data System (ADS)

Takmakov, Pavel; McKinney, Collin J.; Carelli, Regina M.; Wightman, R. Mark

2011-07-01

Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals.

Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

PubMed Central

Takmakov, Pavel; McKinney, Collin J.; Carelli, Regina M.; Wightman, R. Mark

2011-01-01

Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals. PMID:21806203

Electrophysiological Responses to Expectancy Violations in Semantic and Gambling Tasks: A Comparison of Different EEG Reference Approaches

PubMed Central

Li, Ya; Wang, Yongchun; Zhang, Baoqiang; Wang, Yonghui; Zhou, Xiaolin

2018-01-01

Dynamically evaluating the outcomes of our actions and thoughts is a fundamental cognitive ability. Given its excellent temporal resolution, the event-related potential (ERP) technology has been used to address this issue. The feedback-related negativity (FRN) component of ERPs has been studied intensively with the averaged linked mastoid reference method (LM). However, it is unknown whether FRN can be induced by an expectancy violation in an antonym relations context and whether LM is the most suitable reference approach. To address these issues, the current research directly compared the ERP components induced by expectancy violations in antonym expectation and gambling tasks with a within-subjects design and investigated the effect of the reference approach on the experimental effects. Specifically, we systematically compared the influence of the LM, reference electrode standardization technique (REST) and average reference (AVE) approaches on the amplitude, scalp distribution and magnitude of ERP effects as a function of expectancy violation type. The expectancy deviation in the antonym expectation task elicited an N400 effect that differed from the FRN effect induced in the gambling task; this difference was confirmed by all the three reference methods. Both the amplitudes of the ERP effects (N400 and FRN) and the magnitude as the expectancy violation increased were greater under the LM approach than those under the REST approach, followed by those under the AVE approach. Based on the statistical results, the electrode sites that showed the N400 and FRN effects critically depended on the reference method, and the results of the REST analysis were consistent with previous ERP studies. Combined with evidence from simulation studies, we suggest that REST is an optional reference method to be used in future ERP data analysis. PMID:29615858

Fabrication of a microfluidic Ag/AgCl reference electrode and its application for portable and disposable electrochemical microchips.

PubMed

Zhou, Jianhua; Ren, Kangning; Zheng, Yizhe; Su, Jing; Zhao, Yihua; Ryan, Declan; Wu, Hongkai

2010-09-01

This report describes a convenient method for the fabrication of a miniaturized, reliable Ag/AgCl reference electrode with nanofluidic channels acting as a salt bridge that can be easily integrated into microfluidic chips. The Ag/AgCl reference electrode shows high stability with millivolt variations. We demonstrated the application of this reference electrode in a portable microfluidic chip that is connected to a USB-port microelectrochemical station and to a computer for data collection and analysis. The low fabrication cost of the chip with the potential for mass production makes it disposable and an excellent candidate for real-world analysis and measurement. We used the chip to quantitatively analyze the concentrations of heavy metal ions (Cd(2+) and Pb(2+)) in sea water. We believe that the Ag/AgCl reference microelectrode and the portable electrochemical system will be of interest to people in microfluidics, environmental science, clinical diagnostics, and food research.

Aluminum reference electrode

DOEpatents

Sadoway, Donald R.

1988-01-01

A stable reference electrode for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na.sub.3 AlF.sub.6, wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution.

Device for measuring oxygen activity in liquid sodium

DOEpatents

Roy, P.; Young, R.S.

1973-12-01

A composite ceramic electrolyte in a configuration (such as a closed end tube or a plate) suitable to separate liquid sodium from a reference electrode with a high impedance voltmeter connected to measure EMF between the sodium and the reference electrode as a measure of oxygen activity in the sodium is described. The composite electrolyte consists of zirconiacalcia with a bonded layer of thoria-yttria. The device is used with a gaseous reference electrode on the zirconia-calcia side and liquid sodium on the thoria-yttria side of the electrolyte. (Official Gazette)

Flow Visualization of Low Prandtl Number Fluids using Electrochemical Measurements

NASA Technical Reports Server (NTRS)

Crunkleton, D.; Anderson, T.; Narayanan, R.; Labrosse, G.

2003-01-01

It is well established that residual flows exist in contained liquid metal processes. In 1-g processing, buoyancy forces often drive these flows and their magnitudes can be substantial. It is also known that residual flows can exist during microgravity processing, and although greatly reduced in magnitude, they can influence the properties of the processed materials. Unfortunately, there are very few techniques to visualize flows in opaque, high temperature liquid metals, and those available are not easily adapted to flight investigation. In this study, a novel technique is developed that uses liquid tin as the model fluid and solid-state electrochemical cells constructed from Yttria-Stabilized Zirconia (YSZ) to establish and measure dissolved oxygen boundary conditions. The melt serves as a common electrode for each of the electrochemical cells in this design, while independent reference electrodes are maintained at the outside surfaces of the electrolyte. By constructing isolated electrochemical cells at various locations along the container walls, oxygen is introduced or extracted by imposing a known electrical potential or passing a given current between the melt and the reference electrode. This programmed titration then establishes a known oxygen concentration boundary condition at the selected electrolyte-melt interface. Using the other cells, the concentration of oxygen at the electrolyte-melt interface is also monitored by measuring the open-circuit potentials developed between the melt and reference electrodes. Thus the electrochemical cells serve to both establish boundary conditions for the passive tracer and sense its path. Rayleigh-Benard convection was used to validate the electrochemical approach to flow visualization. Thus, a numerical characterization of the second critical Rayleigh numbers in liquid tin was conducted for a variety of Cartesian aspect ratios. The extremely low Prandtl number of tin represents the lowest value studied numerically. Additionally, flow field oscillations are visualized and the effect of tilt on convecting systems is quantified. Experimental studies of the effect of convection in liquid tin are presented. Three geometries are studied: (1) double electrochemical cell with vertical concentration gradients; (2) double cell with horizontal concentration gradients; and (3) multiple cells with vertical temperature gradients. The first critical Rayleigh number transition is detected with geometry (1) and it is concluded that current measurements are not as affected by convection as EMF measurements. The system is compared with numerical simulations in geometry (2), and oscillating convection is detected with geometry (3).

Pool power control in remelting systems

DOEpatents

Williamson, Rodney L [Albuquerque, NM; Melgaard, David K [Albuquerque, NM; Beaman, Joseph J [Austin, TX

2011-12-13

An apparatus for and method of controlling a remelting furnace comprising adjusting current supplied to an electrode based upon a predetermined pool power reference value and adjusting the electrode drive speed based upon the predetermined pool power reference value.

Teaching pH Measurements with a Student-Assembled Combination Quinhydrone Electrode

ERIC Educational Resources Information Center

Scholz, Fritz; Steinhardt, Tim; Kahlert, Heike; Porksen, Jens R.; Behnert, Jurgen

2005-01-01

A simple combination pH electrode consisting of a solid-state quinhydrone sensor and a solid-state quinhydrone reference electrode is described. Both electrodes are essentially rubber stoppers that are inserted into a special doublewalled holder.

Micromachined three-dimensional electrode arrays for transcutaneous nerve tracking

NASA Astrophysics Data System (ADS)

Rajaraman, Swaminathan; Bragg, Julian A.; Ross, James D.; Allen, Mark G.

2011-08-01

We report the development of metal transfer micromolded (MTM) three-dimensional microelectrode arrays (3D MEAs) for a transcutaneous nerve tracking application. The measurements of electrode-skin-electrode impedance (ESEI), electromyography (EMG) and nerve conduction utilizing these minimally invasive 3D MEAs are demonstrated in this paper. The 3D MEAs used in these measurements consist of a metalized micro-tower array that can penetrate the outer layers of the skin in a painless fashion and are fabricated using MTM technology. Two techniques, an inclined UV lithography approach and a double-side exposure of thick negative tone resist, have been developed to fabricate the 3D MEA master structure. The MEAs themselves are fabricated from the master structure utilizing micromolding techniques. Metal patterns are transferred during the micromolding process, thereby ensuring reduced process steps compared to traditional silicon-based approaches. These 3D MEAs have been packaged utilizing biocompatible Kapton® substrates. ESEI measurements have been carried out on test human subjects with standard commercial wet electrodes as a reference. The 3D MEAs demonstrate an order of magnitude lower ESEI (normalized to area) compared to wet electrodes for an area that is 12.56 times smaller. This compares well with other demonstrated approaches in literature. For a nerve tracking demonstration, we have chosen EMG and nerve conduction measurements on test human subjects. The 3D MEAs show 100% improvement in signal power and SNR/√area as compared to standard electrodes. They also demonstrate larger amplitude signals and faster rise times during nerve conduction measurements. We believe that this microfabrication and packaging approach scales well to large-area, high-density arrays required for applications like nerve tracking. This development will increase the stimulation and recording fidelity of skin surface electrodes, while increasing their spatial resolution by an order of magnitude or more. Although biopotential electrode systems are not without their challenges, the non-invasive access to neural information, along with the potential for automation with associated electronic and software development, is precisely what makes this technology an excellent candidate for the next generation in diagnostic, therapeutic, and prosthetic devices.

Mapping slow waves and spikes in chronically instrumented conscious dogs: implantation techniques and recordings.

PubMed

Ver Donck, L; Lammers, W J E P; Moreaux, B; Smets, D; Voeten, J; Vekemans, J; Schuurkes, J A J; Coulie, B

2006-03-01

Myoelectric recordings from the intestines in conscious animals have been limited to a few electrode sites with relatively large inter-electrode distances. The aim of this project was to increase the number of recording sites to allow high-resolution reconstruction of the propagation of myoelectrical signals. Sets of six unipolar electrodes, positioned in a 3x2 array, were constructed. A silver ring close to each set served as the reference electrodes. Inter-electrode distances varied from 4 to 8 mm. Electrode sets, to a maximum of 4, were implanted in various configurations allowing recording from 24 sites simultaneously. Four sets of 6 electrodes each were implanted successfully in 11 female Beagles. Implantation sites evaluated were the upper small intestine (n=10), the lower small intestine (n=4) and the stomach (n=3). The implants remained functional for 7.2 months (median; range 1.4-27.3 months). Recorded signals showed slow waves at regular intervals and spike potentials. In addition, when the sets were positioned close together, it was possible to re-construct the propagation of individual slow waves, to determine their direction of propagation and to calculate their propagation velocity. No signs or symptoms of interference with normal GI-function were observed in the tested animals. With this approach, it is possible to implant 24 extracellular electrodes on the serosal surface of the intestines without interfering with its normal physiology. This approach makes it possible to study the electrical activities of the GI system at high resolution in vivo in the conscious animal.

Development of an embeddable reference electrode for reinforced concrete structures.

DOT National Transportation Integrated Search

1998-01-01

There is a concern that none of the existing concrete-embeddable reference electrodes that are being used as a convenient means for monitoring the condition of the reinforcing steel in concrete bridges or the operation of cathodic protection systems ...

Aluminum reference electrode

DOEpatents

Sadoway, D.R.

1988-08-16

A stable reference electrode is described for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na[sub 3]AlF[sub 6], wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution. 1 fig.

SAMPLING DEVICE FOR pH MEASUREMENT IN PROCESS STREAMS

DOEpatents

Michelson, C.E.; Carson, W.N. Jr.

1958-11-01

A pH cell is presented for monitoring the hydrogen ion concentration of a fluid in a process stream. The cell is made of glass with a side entry arm just above a reservoir in which the ends of a glass electrode and a reference electrode are situated. The glass electrode contains the usual internal solution which is connected to a lead. The reference electrode is formed of saturated calomel having a salt bridge in its bottom portion fabricated of a porous glass to insure low electrolyte flow. A flush tube leads into the cell through which buffer and flush solutions are introduced. A ground wire twists about both electrode ends to insure constant electrical grounding of the sample. The electrode leads are electrically connected to a pH meter of aay standard type.

Auditory evoked potential P300 in adults: reference values

PubMed Central

Didoné, Dayane Domeneghini; Garcia, Michele Vargas; Oppitz, Sheila Jacques; da Silva, Thalisson Francisco Finamôr; dos Santos, Sinéia Neujahr; Bruno, Rúbia Soares; Filha, Valdete Alves Valentins dos Santos; Cóser, Pedro Luis

2016-01-01

ABSTRACT Objective To establish reference intervals for cognitive potential P300 latency using tone burst stimuli. Methods This study involved 28 participants aged between 18 and 59 years. P300 recordings were performed using a two-channel device (Masbe, Contronic). Electrode placement was as follows: Fpz (ground electrode), Cz (active electrode), M1 and M2 (reference electrodes). Intensity corresponded to 80 dB HL and frequent and rare stimulus frequencies to 1,000Hz and 2,000Hz, respectively. Stimuli were delivered binaurally. Results Mean age of participants was 35 years. Average P300 latency was 305ms. Conclusion Maximum acceptable P300 latency values of 362.5ms (305 + 2SD 28.75) were determined for adults aged 18 to 59 years using the protocol described. PMID:27462895

Electrode-shaping for the excitation and detection of permitted arbitrary modes in arbitrary geometries in piezoelectric resonators.

PubMed

Pulskamp, Jeffrey S; Bedair, Sarah S; Polcawich, Ronald G; Smith, Gabriel L; Martin, Joel; Power, Brian; Bhave, Sunil A

2012-05-01

This paper reports theoretical analysis and experimental results on a numerical electrode shaping design technique that permits the excitation of arbitrary modes in arbitrary geometries for piezoelectric resonators, for those modes permitted to exist by the nonzero piezoelectric coefficients and electrode configuration. The technique directly determines optimal electrode shapes by assessing the local suitability of excitation and detection electrode placement on two-port resonators without the need for iterative numerical techniques. The technique is demonstrated in 61 different electrode designs in lead zirconate titanate (PZT) thin film on silicon RF micro electro-mechanical system (MEMS) plate, beam, ring, and disc resonators for out-of-plane flexural and various contour modes up to 200 MHz. The average squared effective electromechanical coupling factor for the designs was 0.54%, approximately equivalent to the theoretical maximum value of 0.53% for a fully electroded length-extensional mode beam resonator comprised of the same composite. The average improvement in S(21) for the electrode-shaped designs was 14.6 dB with a maximum improvement of 44.3 dB. Through this piezoelectric electrodeshaping technique, 95% of the designs showed a reduction in insertion loss.

An electrocatalytic oxidation and voltammetric method using a chemically reduced graphene oxide film for the determination of caffeic acid.

PubMed

Vilian, A T Ezhil; Chen, Shen-Ming; Chen, Ying-Hui; Ali, M Ajmal; Al-Hemaid, Fahad M A

2014-06-01

The present work describes the characterization of a chemically reduced graphene oxide (CRGO) modified glassy carbon electrode (GCE) for electrochemical investigation of caffeic acid (CA). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), amperometry, and electrochemical impedance spectroscopy (EIS) techniques were used to characterize the properties of the electrode. There was an obvious enhancement of the current response and a decreased over potential for the oxidation of CA. The interfacial electron transfer rate of CA was studied by EIS. Under optimal conditions, the CRGO displayed a linear response range of 1×10(-8) to 8×10(-4) M and the detection limit was 2×10(-9) M (S/N=3), with a sensitivity of 192.21 μA mM(-1) cm(-2) at an applied potential of +0.2V (vs. Ag/AgCl reference), which suggests that the CRGO is a promising sensing materials for the electrochemical investigation of CA. The results showed the good sensitivity, selectivity and high reproducibility of the CRGO modified electrode. Moreover, this modified electrode was further applied to investigate the CA in real samples of wine with satisfactory results. Copyright © 2014 Elsevier Inc. All rights reserved.

Automatic reference selection for quantitative EEG interpretation: identification of diffuse/localised activity and the active earlobe reference, iterative detection of the distribution of EEG rhythms.

PubMed

Wang, Bei; Wang, Xingyu; Ikeda, Akio; Nagamine, Takashi; Shibasaki, Hiroshi; Nakamura, Masatoshi

2014-01-01

EEG (Electroencephalograph) interpretation is important for the diagnosis of neurological disorders. The proper adjustment of the montage can highlight the EEG rhythm of interest and avoid false interpretation. The aim of this study was to develop an automatic reference selection method to identify a suitable reference. The results may contribute to the accurate inspection of the distribution of EEG rhythms for quantitative EEG interpretation. The method includes two pre-judgements and one iterative detection module. The diffuse case is initially identified by pre-judgement 1 when intermittent rhythmic waveforms occur over large areas along the scalp. The earlobe reference or averaged reference is adopted for the diffuse case due to the effect of the earlobe reference depending on pre-judgement 2. An iterative detection algorithm is developed for the localised case when the signal is distributed in a small area of the brain. The suitable averaged reference is finally determined based on the detected focal and distributed electrodes. The presented technique was applied to the pathological EEG recordings of nine patients. One example of the diffuse case is introduced by illustrating the results of the pre-judgements. The diffusely intermittent rhythmic slow wave is identified. The effect of active earlobe reference is analysed. Two examples of the localised case are presented, indicating the results of the iterative detection module. The focal and distributed electrodes are detected automatically during the repeating algorithm. The identification of diffuse and localised activity was satisfactory compared with the visual inspection. The EEG rhythm of interest can be highlighted using a suitable selected reference. The implementation of an automatic reference selection method is helpful to detect the distribution of an EEG rhythm, which can improve the accuracy of EEG interpretation during both visual inspection and automatic interpretation. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Reference electrode for strong oxidizing acid solutions

DOEpatents

Rigdon, Lester P.; Harrar, Jackson E.; Bullock, Sr., Jack C.; McGuire, Raymond R.

1990-01-01

A reference electrode for the measurement of the oxidation-reduction potentials of solutions is especially suitable for oxidizing solutions such as highly concentrated and fuming nitric acids, the solutions of nitrogen oxides, N.sub.2 O.sub.4 and N.sub.2 O.sub.5, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/Ce(III)/70 wt. % HNO.sub.3, and includes a double-junction design with an intermediate solution of 70 wt. % HNO.sub.3. The liquid junctions are made from Corning No. 7930 glass for low resistance and negligible solution leakage.

A Simple Hydrogen Electrode

ERIC Educational Resources Information Center

Eggen, Per-Odd

2009-01-01

This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements…

Impact of rounded electrode corners on breakdown characteristics of AlGaN/GaN high-electron mobility transistors

NASA Astrophysics Data System (ADS)

Yamazaki, Taisei; Asubar, Joel T.; Tokuda, Hirokuni; Kuzuhara, Masaaki

2018-05-01

We investigated the impact of rounded electrode corners on the breakdown characteristics of AlGaN/GaN high-electron mobility transistors. For standard reference devices, catastrophic breakdown occurred predominantly near the sharp electrode corners. By introducing a rounded-electrode architecture, premature breakdown at the corners was mitigated. Moreover, the rate of breakdown voltage (V BR) degradation with an increasing gate width (W G) was significantly lower for devices with rounded corners. When W G was increased from 100 µm to 10 mm, the V BR of the reference device dropped drastically, from 1,200 to 300 V, whereas that of the rounded-electrode device only decreased to a respectable value of 730 V.

A reference electrode based on polyvinyl butyral (PVB) polymer for decentralized chemical measurements.

PubMed

Guinovart, Tomàs; Crespo, Gastón A; Rius, F Xavier; Andrade, Francisco J

2014-04-22

A new solid-state reference electrode using a polymeric membrane of polyvinyl butyral (PVB), Ag/AgCl and NaCl to be used in decentralized chemical measurements is presented. The electrode is made by drop-casting the membrane cocktail onto a glassy carbon (GC) substrate. A stable potential (less than 1 mV dec(-1)) over a wide range of concentrations for the several chemical species tested is obtained. No significant influence to changes in redox potential, light and pH are observed. The response of this novel electrode shows good correlation when compared with a conventional double-junction reference electrode. Also good long-term stability (90±33 μV/h) and a lifetime of approximately 4 months are obtained. Aspects related to the working mechanisms are discussed. Atomic Force Microscopy (AFM) studies reveal the presence of nanopores and channels on the surface, and electrochemical impedance spectroscopy (EIS) of optimized electrodes show low bulk resistances, usually in the kΩ range, suggesting that a nanoporous polymeric structure is formed in the interface with the solution. Future applications of this electrode as a disposable device for decentralized measurements are discussed. Examples of the utilization on wearable substrates (tattoos, fabrics, etc) are provided. Copyright © 2014 Elsevier B.V. All rights reserved.

Cr/ITO semi-transparent n-type electrode for high-efficiency AlGaN/InGaN-based near ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Kim, Hwankyo; Kim, Dae-Hyun; Seong, Tae-Yeon

2017-11-01

We investigated the electrical performance of near ultraviolet (NUV) (390 nm) light-emitting diodes (LEDs) fabricated with various semi-transparent Cr/ITO n-type contacts. It was shown that after annealing at 400 °C, Cr/ITO (10 nm/40 nm) contact was ohmic with a specific contact resistance of 9.8 × 10-4 Ωcm2. NUV AlGaN-based LEDs fabricated with different Cr/ITO (6-12 nm/40 nm) electrodes exhibited forward-bias voltages of 3.27-3.30 V at an injection current of 20 mA, which are similar to that of reference LED with Cr/Ni/Au (20 nm/25 nm/200 nm) electrode (3.29 V). The LEDs with the Cr/ITO electrodes gave series resistances of 10.69-11.98 Ω, while the series resistance is 10.84 Ohm for the reference LED. The transmittance of the Cr/ITO samples significantly improved when annealed at 400 °C. The transmittance (25.8-45.2% at 390 nm) of the annealed samples decreased with increasing Cr layer thickness. The LEDs with the Cr/ITO electrodes exhibited higher light output power than reference LED (with Cr/Ni/Au electrode). In particular, the LED with the Cr/ITO (12 nm/40 nm) electrode showed 9.3% higher light output power at 100 mA than reference LED. Based on the X-ray photoemission spectroscopy (XPS) and electrical results, the ohmic formation mechanism is described and discussed.

Portable probe to measure sensitization of stainless steel

DOEpatents

Park, Jang Y.

1979-01-01

An electrochemical cell for making field measurements of metals such as stainless steel comprises a cylinder containing a reservoir of an electrolyte, a reference electrode, a capillary tube connecting the electrolyte to the surface of the metal to be measured and another electrode in electrical contact with the electrolyte. External connections from the reference electrode, the other electrode, and the sample to a measuring device provide means for maintaining the potential of the electrolyte while sweeping the potential difference between the electrolyte and the metal. Such a sweep enables the determination of a current-voltage characteristic that is a measure of sensitization in the metal.

Membrane reference electrode

DOEpatents

Redey, L.; Bloom, I.D.

1988-01-21

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

Thin Film Electrodes with an Integral Current Collection Grid for Use with Solid Electrolytes

NASA Technical Reports Server (NTRS)

Ryan, M. A.; Kisor, A.; Williams, R. M.; Jeffries-Nakamura, B.; O'Connor, D.

1994-01-01

Thin film, high performance electrodes which can operate in high temperature environments are necessary for many devices which use a solid electrolyte. Electrodes of rhodium-tungsten alloy have been deposited on solid electrolyte using photolytic chemical vapor deposition (PCVD). A technique for depositing electrodes and current collection grids simultaneously has been developed using the prenucleation characteristics of PCVD. This technique makes it possible to fabricate electrodes which allow vapor transport through the thin (<1 (micro)m) portions of the electrode while integral thick grid lines improve the electronic conductivity of the electrode, thus improving overall performance.

Ionic electroactive hybrid transducers

NASA Astrophysics Data System (ADS)

Akle, Barbar J.; Bennett, Matthew D.; Leo, Donald J.

2005-05-01

Ionic electroactive actuators have received considerable attention in the past ten years. Ionic electroactive polymers, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typical types of ionic electroactive polymer transducers include ionic polymers, conducting polymers, and carbon nanotubes. Preliminary research combining multiple types of materials proved to enhance certain transduction properties such as speed of response, maximum strain, or quasi-static actuation. Recently it was demonstrated that ionomer-ionic liquid transducers can operate in air for long periods of time (>250,000 cycles) and showed potential to reduce or eliminate the back-relaxation issue associated with ionomeric polymers. In addition, ionic liquids have higher electrical stability window than those operated with water as the solvent thereby increasing the maximum strain that the actuator can produce. In this work, a new technique developed for plating metal particulates on the surface of ionomeric materials is applied to the development of hybrid transducers that incorporate carbon nanotubes and conducting polymers as electrode materials. The new plating technique, named the direct assembly process, consists of mixing a conducting powder with an ionomer solution. This technique has demonstrated improved response time and strain output as compared to previous methods. Furthermore, the direct assembly process is less costly to implement than traditional impregnation-reduction methods due to less dependence on reducing agents, it requires less time, and is easier to implement than other processes. Electrodes applied using this new technique of mixing RuO2 (surface area 45~65m2/g) particles and Nafion dispersion provided 5x the displacement and 10x the force compared to a transducer made with conventional methods. Furthermore, the study illustrated that the response speed of the transducer is optimized by varying the vol% of metal in the electrode. For RuO2, the optimal loading was approximately 45%. This study shows that carbon nanotubes electrodes have an optimal performance at loadings around 30 vol%, while PANI electrodes are optimized at 95 vol%. Due to low percolation threshold, carbon nanotubes actuators perform better at lower loading than other conducting powders. The addition of nanotubes to the electrode tends to increase both the strain rate and the maximum strain of the hybrid actuator. SWNT/RuO2 hybrid transducer has a strain rate of 2.5%/sec, and a maximum attainable peak-to-peak strain of 9.38% (+/- 2V). SWNT/PANI hybrid also increased both strain and strain rate but not as significant as with RuO2. PANI/RuO2 actuator had an overwhelming back relaxation.

Detection of Electrocardiogram by Electrodes with Fabrics Using Capacitive Coupling

NASA Astrophysics Data System (ADS)

Ueno, Akinori; Furusawa, Yoichi; Hoshino, Hiroshi; Ishiyama, Yoji

This article reports on a novel technique for detecting electrocardiogram (ECG) at a condition where thin cloth is interpolated between sensing electrodes and the skin to which the electrodes are attached. The technique is based upon capacitive coupling composed of the electrode, the cloth and the skin, so that the electrode can lead alternating electrocardiographic current through capacitance of the coupling. The technique is also founded on impedance transforming circuit that has extremely high input impedance around 1000GΩ and low output impedance, so as to match high output impedance of the electrode to low input impedance required by subsequent circuitry. A pilot ECG measuring device was manufactured using the technique and experiments showed (1) ECG recordings using the device with silk of 240μm thickness or with cotton of 564μm thickness were quite similar to ECGs recorded from the skin using conventional system, (2) stable ECGs were observed with the silk below 600μm thickness or with the cotton below 1128μm thickness, (3) effects of long-term measurement and perspiration on ECG waveform were negligible. These results prove feasibility of the proposed technique for detecting ECG by electrodes with fabrics.

An independently addressable microbiosensor array: what are the limits of sensing element density?

PubMed

Yu, P; Wilson, G S

2000-01-01

A microdisc sensor array, prepared by thin film technology, has been used as a model for miniaturized multi-functional biosensors. It consists of a series of wells, 20 microns in diameter, possessing a 1000 A Pt layer at the bottom that serves as the indicating electrode. The depth of the wells ranged from 2.3-24 microns, depending on the photoresist employed and the spinning speed used to coat the electrode interconnect grid. Ten such wells were arranged in a circular array within an area of radius 130 microns. The center to center distance between any two of the discs ranged from 30 to 155 microns. Each disc is connected by a conductive film line to corresponding pads on the side of the sensor chip. A cylinder placed on top of the chip array formed the electrochemical cell into which a common reference and counter electrode were placed. The reference electrode was operated at ground potential. Prior to the evaluation of enzyme sensors, an assessment of "chemical cross-talk", the perturbation of sensor response resulting from the overlap of proximal diffusion layers, was made using Fe(CN)6(4-). The preliminary conclusion is that the sensing elements probably must be separated by about 100 microns in order to avoid interference from adjacent sensors. A technique was developed for the precision delivery of enzyme and cross-linking agent to the 2.3 microns cavity, having a capacity of 4 pL. This procedure makes possible the preparation of sensor arrays capable of detecting different analytes by employing different enzymes. The sensors gave reasonably rapid (2-4 s) response with linearity (up to about 10 mM. However, the sensors in the center of the array clearly showed the effects of depletion of substrates by the surrounding sensors.

Lithium loss in the solid electrolyte interphase: Lithium quantification of aged lithium ion battery graphite electrodes by means of laser ablation inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Schwieters, Timo; Evertz, Marco; Mense, Maximilian; Winter, Martin; Nowak, Sascha

2017-07-01

In this work we present a new method using LA-ICP-MS to quantitatively determine the lithium content in aged graphite electrodes of a lithium ion battery (LIB) by performing total depth profiling. Matrix matched solid external standards are prepared using a solid doping approach to avoid elemental fractionation effects during the measurement. The results are compared and matched to the established ICP-OES technique for bulk quantification after performing a microwave assisted acid digestion. The method is applied to aged graphite electrodes in order to determine the lithium immobilization (= "Li loss") in the solid electrolyte interphase after the first cycle of formation. For this, different samples including a reference sample are created to obtain varying thicknesses of the SEI covering the electrode particles. By applying defined charging voltages, an initial lithiation process is performed to obtain specific graphite intercalation compounds (GICs, with target stoichiometries of LiC30, LiC18, LiC12 and LiC6). Afterwards, the graphite electrode is completely discharged to obtain samples without mobile, thus active lithium in its lattice. Taking the amount of lithium into account which originates from the residues of the LiPF6 (dissolved in the carbon components containing electrolyte), it is possible to subtract the amount of lithium in the SEI.

Serotonin (5-HT) released by activated white blood cells in a biological fuel cell provide a potential energy source for electricity generation.

PubMed

Justin, Gusphyl A; Sun, Mingui; Zhang, Yingze; Cui, X Tracy; Sclabassi, Robert

2006-01-01

Previous studies by our group have demonstrated the ability of white blood cells to generate small electrical currents, on the order of 1-3 microA/cm(2), when placed at the anode compartment of a proton exchange membrane (PEM) biological fuel cell. In this research study, an electrochemical technique is used to further investigate the electron transfer ability of activated white blood cells at interfacing electrodes in an attempt to elucidate the mechanism of electron transfer in the original biological fuel cell experiments. Cyclic voltammograms were obtained for human white blood cells using a three-electrode system. The working and counter electrodes were made from carbon felt and platinum, respectively, while the reference was a saturated calomel electrode (SCE). Oxidation peaks were observed at an average potential of 363 mV vs. SCE for the PMA/ionomycin activated white blood cells in glucose solution. However a corresponding reduction peak was not observed, suggesting irreversibility of the redox reaction. The cyclic voltammograms recorded for the white blood cells bear very close similarities to those of the neurotransmitter serotonin (5-HT). Serotonin released by white blood cells into the extracellular environment may be irreversibly oxidized at the working electrode in the cyclic voltammetry experiments and at the PEM biological fuel cell anode in our earlier electrochemical cell studies.

Polyacrylate microspheres composite for all-solid-state reference electrodes.

PubMed

Kisiel, Anna; Donten, Mikołaj; Mieczkowski, Józef; Rius-Ruiz, F Xavier; Maksymiuk, Krzysztof; Michalska, Agata

2010-09-01

A novel concept is proposed for the encapsulation of components within polyacrylate microspheres, prior to their incorporation into a membrane phase. Thus finer and better controlled dispersion of heterogeneous membrane components can be achieved. This concept was verified by using a poly(n-butyl acrylate) membrane-based reference electrode as an example. In this example the proper dispersion of solid constituents of the heterogeneous membrane and prevention of their leakage are both of primary importance. Potassium chloride-loaded poly(n-butyl acrylate) microspheres were prepared and then left in contact with silver nitrate to convert some of the KCl into AgCl. The material obtained was introduced into a poly(n-butyl acrylate) membrane. The reference electrode membranes obtained in this way were characterized with much more stable potential (both in different electrolytes and over time) compared with electrodes prepared by the direct introduction of KCl and AgCl to the membrane.

A new technique based on current measurement for nanoscale ferroelectricity assessment: Nano-positive up negative down

NASA Astrophysics Data System (ADS)

Martin, Simon; Baboux, Nicolas; Albertini, David; Gautier, Brice

2017-02-01

In this paper, we propose a new procedure which aims at measuring the polarisation switching current at the nanoscale on ferroelectric thin films with the atomic force microscope tip used as a top electrode. Our technique is an adaptation of the so-called positive up negative down method commonly operated on large electrodes. The main obstacle that must be overcome to implement such measurement is the enhancement of the signal to noise ratio, in a context where the stray capacitance of the sample/tip/lever/lever holder system generates a dielectric displacement current several orders of magnitude higher than the current to be measured. This problem is solved by the subtraction of the displacement current through a reference capacitance. For the first time, we show an example of nanoscale positive up negative down measurement of the polarisation charge on a PbZrTiO3 thin film and compare the measured value with paraelectric samples. From the comparison with macroscopic measurement, we deduce the effective area of contact between the tip and the sample.

A Multi-Parametric Device with Innovative Solid Electrodes for Long-Term Monitoring of pH, Redox-Potential and Conductivity in a Nuclear Waste Repository

PubMed Central

Daoudi, Jordan; Betelu, Stephanie; Tzedakis, Theodore; Bertrand, Johan; Ignatiadis, Ioannis

2017-01-01

We present an innovative electrochemical probe for the monitoring of pH, redox potential and conductivity in near-field rocks of deep geological radioactive waste repositories. The probe is composed of a monocrystalline antimony electrode for pH sensing, four AgCl/Ag-based reference or Cl− selective electrodes, one Ag2S/Ag-based reference or S2− selective electrode, as well as four platinum electrodes, a gold electrode and a glassy-carbon electrode for redox potential measurements. Galvanostatic electrochemistry impedance spectroscopy using AgCl/Ag-based and platinum electrodes measure conductivity. The use of such a multi-parameter probe provides redundant information, based as it is on the simultaneous behaviour under identical conditions of different electrodes of the same material, as well as on that of electrodes made of different materials. This identifies the changes in physical and chemical parameters in a solution, as well as the redox reactions controlling the measured potential, both in the solution and/or at the electrode/solution interface. Understanding the electrochemical behaviour of selected materials thus is a key point of our research, as provides the basis for constructing the abacuses needed for developing robust and reliable field sensors. PMID:28608820

Carbon Nanotube Thread Electrochemical Cell: Detection of Heavy Metals.

PubMed

Zhao, Daoli; Siebold, David; Alvarez, Noe T; Shanov, Vesselin N; Heineman, William R

2017-09-19

In this work, all three electrodes in an electrochemical cell were fabricated based on carbon nanotube (CNT) thread. CNT thread partially insulated with a thin polystyrene coating to define the microelectrode area was used as the working electrode; bare CNT thread was used as the auxiliary electrode; and a micro quasi-reference electrode was fabricated by electroplating CNT thread with Ag and then anodizing it in chloride solution to form a layer of AgCl. The Ag|AgCl coated CNT thread electrode provided a stable potential comparable to the conventional liquid-junction type Ag|AgCl reference electrode. The CNT thread auxiliary electrode provided a stable current, which is comparable to a Pt wire auxiliary electrode. This all-CNT thread three electrode cell has been evaluated as a microsensor for the simultaneous determination of trace levels of heavy metal ions by anodic stripping voltammetry (ASV). Hg 2+ , Cu 2+ , and Pb 2+ were used as a representative system for this study. The calculated detection limits (based on the 3σ method) with a 120 s deposition time are 1.05, 0.53, and 0.57 nM for Hg 2+ , Cu 2+ , and Pb 2+ , respectively. These electrodes significantly reduce the dimensions of the conventional three electrode electrochemical cell to the microscale.

A Multi-Parametric Device with Innovative Solid Electrodes for Long-Term Monitoring of pH, Redox-Potential and Conductivity in a Nuclear Waste Repository.

PubMed

Daoudi, Jordan; Betelu, Stephanie; Tzedakis, Theodore; Bertrand, Johan; Ignatiadis, Ioannis

2017-06-13

We present an innovative electrochemical probe for the monitoring of pH, redox potential and conductivity in near-field rocks of deep geological radioactive waste repositories. The probe is composed of a monocrystalline antimony electrode for pH sensing, four AgCl/Ag-based reference or Cl - selective electrodes, one Ag₂S/Ag-based reference or S 2- selective electrode, as well as four platinum electrodes, a gold electrode and a glassy-carbon electrode for redox potential measurements. Galvanostatic electrochemistry impedance spectroscopy using AgCl/Ag-based and platinum electrodes measure conductivity. The use of such a multi-parameter probe provides redundant information, based as it is on the simultaneous behaviour under identical conditions of different electrodes of the same material, as well as on that of electrodes made of different materials. This identifies the changes in physical and chemical parameters in a solution, as well as the redox reactions controlling the measured potential, both in the solution and/or at the electrode/solution interface. Understanding the electrochemical behaviour of selected materials thus is a key point of our research, as provides the basis for constructing the abacuses needed for developing robust and reliable field sensors.

Understanding of ammonia transport in PEM fuel cells

NASA Astrophysics Data System (ADS)

Jung, Myunghee

This dissertation investigates ammonia (NH3) as a fuel contaminant to the anode in Proton Exchange Membrane Fuel Cells (PEMFCs). Since NH 3 is fed to the anode in a gas phase and transferred to the cathode, the effect of a contaminant is distributed through MEA and quite complicated. This study is focused on the investigation of mechanism of NH3 transport and the isolation of multiple effects to degrade the performance of fuel cell. An External Reference Electrode (ERE) was employed to decouple the effect of individual electrode and explain the mechanism of NH3 contamination. A mechanism of NH3 transport is proposed and supported by data for various inlet conditions in a N2/N2 laboratory-scale fuel cell at Open Circuit Conditions (OCC). With a commercialized GORE(TM) PRIMEA RTM 5631 MEAs at 70°C, data were obtained utilizing a material balance technique, which uses an ion selective electrode (ISE) to determine the concentration of ammonium ion in the process streams. The results indicate that ammonia is not transported across the membrane when the feeds to both electrodes are dry. However, with humidified feeds ammonia was transported from the anode to the cathode. The data also indicate the water content of in the MEA is the critical factor that causes NH3 crossover in the MEA. Diffusion coefficients of NH3 in MEA are also calculated at different relative humilities. An ERE was developed for PEM fuel cell by using a NafionRTM strip which was used to understand contamination mechanism. The voltage of anode electrode relative to ERE was measured during a polarization curve. The data showed the measurement of individual electrode potential was extremely affected by the misalignment between two electrodes. We compare the overpotential measured from the reference electrode and the calculated overpotential from subtracting the cell voltages between neat hydrogen and a 25 ppm CO in H 2 stream at same current. The studies indicated that the overpotentials obtained from two different methods were same and the location of a Nafion RTM strip on MEA did not affect the measured overpotentials. When NH3 was introduced as a contaminant to the cell at OCC, the thermodynamic potential of the anode electrode was measured for GORETM PRIMEARTM 57 series MEA at 80°C. High Frequency Resistance (HFR) and material balance were also analyzed during the change of thermodynamic potential. The results show that the injected NH3 was absorbed in the MEA until the ion exchange capacity was fully saturated and then NH 3 reaction occurred on the electrode. Finally, we studied how NH 3 contamination process occurs from transient voltage changes of the cell and an individual electrode.

Maxwell-Wagner relaxation in electrical imaging.

PubMed

Korjenevsky, A V

2005-04-01

The electric field tomography (EFT) method exploits interaction of high-frequency electric field with an inhomogeneous conductive medium without contact with the electrodes. The interaction is accompanied by a high-frequency redistribution of free charges inside the medium and leads to small and regular phase shifts of the field in the area surrounding an object. Such a kind of phenomenon is referred to as the Maxwell-Wagner relaxation. Measuring the perturbations of the field using the set of electrodes placed around the object enables us to reconstruct the internal structure of the medium, generally the spatial distribution of a nonlinear combination of permittivity and resistivity. In the case of biomedical applications the result of measurements is determined mainly by the resistivity of the tissues. Three-dimensional simulation based on the finite element method has demonstrated the feasibility of the technique.

Techniques For Mass Production Of Tunneling Electrodes

NASA Technical Reports Server (NTRS)

Kenny, Thomas W.; Podosek, Judith A.; Reynolds, Joseph K.; Rockstad, Howard K.; Vote, Erika C.; Kaiser, William J.

1993-01-01

Techniques for mass production of tunneling electrodes developed from silicon-micromachining, lithographic patterning, and related microfabrication processes. Tunneling electrodes named because electrons travel between them by quantum-mechanical tunneling; tunneling electrodes integral parts of tunneling transducer/sensors, which act in conjunction with feedback circuitry to stabilize tunneling currents by maintaining electrode separations of order of 10 Angstrom. Essential parts of scanning tunneling microscopes and related instruments, and used as force and position transducers in novel microscopic accelerometers and infrared detectors.

Electronic drop sensing in microfluidic devices: automated operation of a nanoliter viscometer

PubMed Central

Srivastava, Nimisha; Burns, Mark A.

2007-01-01

We describe three droplet sensing techniques: a digital electrode, an analog electrode, and a thermal method. All three techniques use a single layer of metal lines that is easy to microfabricate and an electronic signal can be produced using low DC voltages. While the electrode methods utilize changes in electrical conductivity when the air/liquid interface of the droplet passes over a pair of electrodes, the thermal method is based on convective heat loss from a locally heated region. For the electrode method, the analog technique is able to detect 25 nL droplets while the digital technique is capable of detecting droplets as small as 100 pL. For thermal sensing, temperature profiles in the range of 36 °C and higher were used. Finally, we have used the digital electrode method and an array of electrodes located at preset distances to automate the operation of a previously described microfluidic viscometer. The viscometer is completely controlled by a laptop computer, and the total time for operation including setup, calibration, sample addition and viscosity calculation is approximately 4 minutes. PMID:16738725

High rate, long cycle life battery electrode materials with an open framework structure

DOEpatents

Wessells, Colin; Huggins, Robert; Cui, Yi; Pasta, Mauro

2015-02-10

A battery includes a cathode, an anode, and an aqueous electrolyte disposed between the cathode and the anode and including a cation A. At least one of the cathode and the anode includes an electrode material having an open framework crystal structure into which the cation A is reversibly inserted during operation of the battery. The battery has a reference specific capacity when cycled at a reference rate, and at least 75% of the reference specific capacity is retained when the battery is cycled at 10 times the reference rate.

Potentiometric NO2 Sensors Based on Thin Stabilized Zirconia Electrolytes and Asymmetric (La0.8Sr0.2)0.95MnO3 Electrodes

PubMed Central

Zou, Jie; Zheng, Yangong; Li, Junliang; Zhan, Zhongliang; Jian, Jiawen

2015-01-01

Here we report on a new architecture for potentiometric NO2 sensors that features thin 8YSZ electrolytes sandwiched between two porous (La0.8Sr0.2)0.95MnO3 (LSM95) layers—one thick and the other thin—fabricated by the tape casting and co-firing techniques. Measurements of their sensing characteristics show that reducing the porosity of the supporting LSM95 reference electrodes can increase the response voltages. In the meanwhile, thin LSM95 layers perform better than Pt as the sensing electrode since the former can provide higher response voltages and better linear relationship between the sensitivities and the NO2 concentrations over 40–1000 ppm. The best linear coefficient can be as high as 0.99 with a sensitivity value of 52 mV/decade as obtained at 500 °C. Analysis of the sensing mechanism suggests that the gas phase reactions within the porous LSM95 layers are critically important in determining the response voltages. PMID:26205270

A Simple Tiltmeter

NASA Technical Reports Server (NTRS)

Dix, M. G.; Harrison, D. R.; Edwards, T. M.

1982-01-01

Bubble vial with external aluminum-foil electrodes is sensing element for simple indicating tiltmeter. To measure bubble displacement, bridge circuit detects difference in capacitance between two sensing electrodes and reference electrode. Tiltmeter was developed for experiment on forecasting seismic events by changes in Earth's magnetic field.

Condensation enhancement by means of electrohydrodynamic techniques

NASA Astrophysics Data System (ADS)

Butrymowicz, Dariusz; Karwacki, Jarosław; Trela, Marian

2014-12-01

Short state-of-the-art on the enhancement of condensation heat transfer techniques by means of condensate drainage is presented in this paper. The electrohydrodynamic (EHD) technique is suitable for dielectric media used in refrigeration, organic Rankine cycles and heat pump devices. The electric field is commonly generated in the case of horizontal tubes by means of a rod-type electrode or mesh electrodes. Authors proposed two geometries in the presented own experimental investigations. The first one was an electrode placed just beneath the tube bottom and the second one consisted of a horizontal finned tube with a double electrode placed beneath the tube. The experimental investigations of these two configurations for condensation of refrigerant R-123 have been accomplished. The obtained results confirmed that the application of the EHD technique for the investigated tube and electrode arrangement caused significant increase in heat transfer coefficient. The condensation enhancement depends both on the geometry of the electrode system and on the applied voltage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

CATO DM; DAHL MM; PHILO GL

This report documents the results of tests designed to characterize the relationship between temperature and the measured potential of electrodes installed on multi-probe corrosion monitoring systems in waste tanks. This report also documents the results of tests designed to demonstrate the impact of liquid in-leakage into electrode bodies as well as the contamination of primary reference electrodes by diffusion through the electrode tip.

Modeling shape selection of buckled dielectric elastomers

NASA Astrophysics Data System (ADS)

Langham, Jacob; Bense, Hadrien; Barkley, Dwight

2018-02-01

A dielectric elastomer whose edges are held fixed will buckle, given a sufficiently applied voltage, resulting in a nontrivial out-of-plane deformation. We study this situation numerically using a nonlinear elastic model which decouples two of the principal electrostatic stresses acting on an elastomer: normal pressure due to the mutual attraction of oppositely charged electrodes and tangential shear ("fringing") due to repulsion of like charges at the electrode edges. These enter via physically simplified boundary conditions that are applied in a fixed reference domain using a nondimensional approach. The method is valid for small to moderate strains and is straightforward to implement in a generic nonlinear elasticity code. We validate the model by directly comparing the simulated equilibrium shapes with the experiment. For circular electrodes which buckle axisymetrically, the shape of the deflection profile is captured. Annular electrodes of different widths produce azimuthal ripples with wavelengths that match our simulations. In this case, it is essential to compute multiple equilibria because the first model solution obtained by the nonlinear solver (Newton's method) is often not the energetically favored state. We address this using a numerical technique known as "deflation." Finally, we observe the large number of different solutions that may be obtained for the case of a long rectangular strip.

Maximizing Ion Transmission from Atmospheric Pressure into the Vacuum of Mass Spectrometers with a Novel Electrospray Interface

PubMed Central

Krutchinsky, Andrew N.; Padovan, Júlio C.; Cohen, Herbert; Chait, Brian T.

2015-01-01

We have discovered that an electrode containing a conical channel with a small angular divergence can transmit into the vacuum almost 100% of an electrospray ion current produced at atmospheric pressure. Our first implementation of such a conical duct, which we term “ConDuct”, uses a conductive plastic pipette tip containing a ≈1.6° divergent channel at its entrance. We observed that the beam formed by the ConDuct electrode has a very low divergence (< 1°) and persisted for long distances in vacuum. Intrigued by these properties, we incorporated this electrode into a novel atmosphere-to-vacuum ion transmission interface, and devised a technique for evaluating its performance relative to commercial reference interfaces that contain heated metal capillaries. We determined that our new interface transmits at least 400 times more ions than the commercial Thermo LCQ DECA XP atmosphere-to-vacuum interface and 2–3 times more than the commercial interface in the Thermo Velos Orbitrap and the Q Exactive mass spectrometers. We conclude that it might be possible to optimize the properties of the transmitted ions further by manufacturing ConDuct inlet electrodes from metal rather than conductive plastic and by determining the optimum angle of channel divergence and channel length. PMID:25588722

Nano-engineered flexible pH sensor for point-of-care urease detection

NASA Astrophysics Data System (ADS)

Sardarinejad, A.; Maurya, D. K.; Tay, C. Y.; Marshall, B. J.; Alameh, K.

2015-12-01

Accurate pH monitoring is crucial for many applications, such as, water quality monitoring, blood monitoring, chemical and biological analyses, environmental monitoring and clinical diagnostic. The most common technique for pH measurement is based on the use of conventional glass pH electrodes. Glass electrodes have several limitations, such as mechanical fragility, large size, limited shapes and high cost, making them impractical for implementation as Lab-onchips and pH sensor capsules. Various metal oxides, such as RuO2, IrO2, TiO2, SnO2, Ta2O5 and PdO have recently been proposed for the realization of pH sensing electrodes. Specifically, ruthenium oxide exhibits unique properties including thermal stability, excellent corrosion resistance, low hysteresis high sensitivity, and low resistivity. In this paper, we demonstrate the concept of a miniaturized ion selective electrode (ISE) based pH sensor for point-of-care urease monitoring. The sensor comprises a thin film RuO2 on platinum sensing electrode, deposited using E-beam and R.F. magnetron sputtering, in conjunction with an integrated Ag/AgCl reference electrode. The performance and characterization of the developed pH/urea sensors in terms of sensitivity, resolution, reversibility and hysteresis are investigated. Experimental results show a linear potential-versus-urea-concentration response for urea concentrations in the range 0 - 180 mg/ml. Experimental results demonstrate super-Nernstian slopes in the range of 64.33 mV/pH - 73.83 mV/pH for RF sputtered RuO2 on platinum sensing electrode using a 80%:20% Ar:O2 gas ratio. The RuO2 sensor exhibits stable operation and fast dynamic response, making it attractive for in vivo use, wearable and flexible biomedical sensing applications.

Development of three-dimensional integrated microchannel-electrode system to understand the particles' movement with electrokinetics

PubMed Central

Obara, H.; Sapkota, A.; Takei, M.

2016-01-01

An optical transparent 3-D Integrated Microchannel-Electrode System (3-DIMES) has been developed to understand the particles' movement with electrokinetics in the microchannel. In this system, 40 multilayered electrodes are embedded at the 2 opposite sides along the 5 square cross-sections of the microchannel by using Micro Electro-Mechanical Systems technology in order to achieve the optical transparency at the other 2 opposite sides. The concept of the 3-DIMES is that the particles are driven by electrokinetic forces which are dielectrophoretic force, thermal buoyancy, electrothermal force, and electroosmotic force in a three-dimensional scope by selecting the excitation multilayered electrodes. As a first step to understand the particles' movement driven by electrokinetic forces in high conductive fluid (phosphate buffer saline (PBS)) with the 3-DIMES, the velocities of particles' movement with one pair of the electrodes are measured three dimensionally by Particle Image Velocimetry technique in PBS; meanwhile, low conductive fluid (deionized water) is used as a reference. Then, the particles' movement driven by the electrokinetic forces is discussed theoretically to estimate dominant forces exerting on the particles. Finally, from the theoretical estimation, the particles' movement mainly results from the dominant forces which are thermal buoyancy and electrothermal force, while the velocity vortex formed at the 2 edges of the electrodes is because of the electroosmotic force. The conclusions suggest that the 3-DIMES with PBS as high conductive fluid helps to understand the three-dimensional advantageous flow structures for cell manipulation in biomedical applications. PMID:27042247

The central electrode correction factor for high-Z electrodes in small ionization chambers.

PubMed

Muir, B R; Rogers, D W O

2011-02-01

Recent Monte Carlo calculations of beam quality conversion factors for ion chambers that use high-Z electrodes [B. R. Muir and D. W. O. Rogers, Med. Phys. 37, 5939-5950 (2010)] have shown large deviations of kQ values from values calculated using the same techniques as the TG-51 and TRS-398 protocols. This report investigates the central electrode correction factor, Pcel, for these chambers. Ionization chambers are modeled and Pcel is calculated using the EGSnrc user code egs_chamber for three cases: in photon and electron beams under reference conditions; as a function of distance from an iridium-192 point source in a water phantom; and as a function of depth in a water phantom on which a 200 kVp x-ray source or 6 MV beam is incident. In photon beams, differences of up to 3% between Pcel calculations for a chamber with a high-Z electrode and those used by TG-51 for a 1 mm diameter aluminum electrode are observed. The central electrode correction factor for a given value of the beam quality specifier is different depending on the amount of filtration of the photon beam. However, in an unfiltered 6 MV beam, Pcel, varies by only 0.3% for a chamber with a high-Z electrode as the depth is varied from 1 to 20 cm in water. The difference between Pcel calculations for chambers with high-Z electrodes and TG-51 values for a chamber with an aluminum electrode is up to 0.45% in electron beams. The central electrode correction, which is roughly proportional to the chambers absorbed dose sensitivity, is found to be large and variable as a function of distance for chambers with high-Z and aluminum electrodes in low-energy photon fields. In this work, ionization chambers that employ high-Z electrodes have been shown to be problematic in various situations. For beam quality conversion factors, the ratio of Pcel in a beam quality Q to that in a Co-60 beam is required; for some chambers, kQ is significantly different from current dosimetry protocol values because of central electrode effects. It would be best for manufacturers to avoid producing ion chambers that use high-Z electrodes.

In Vitro Quantified Determination of β-Amyloid 42 Peptides, a Biomarker of Neuro-Degenerative Disorders, in PBS and Human Serum Using a Simple, Cost-Effective Thin Gold Film Biosensor.

PubMed

Dai, Yifan; Molazemhosseini, Alireza; Liu, Chung Chiun

2017-07-20

A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffered saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K₄Fe(CN)₆ and K₃Fe(CN)₆. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction. The biosensor was a three-electrode electrochemical system, and the working and counter electrodes were 50 nm thin gold film deposited by a sputtering technique. The reference electrode was a thick-film printed Ag/AgCl electrode. Laser ablation technique was used to define the size and structure of the biosensor. Cost-effective roll-to-roll manufacturing process was employed in the fabrication of the biosensor, making it simple and relatively inexpensive. Self-assembled monolayers (SAM) of 3-Mercaptopropionic acid (MPA) was employed to covalently immobilize the thiol group on the gold working electrode. A carbodiimide conjugation approach using N -(3-dimethylaminopropyl)- N '-ethylcarbodiimide hydrochloride (EDC) and N -hydroxysuccinimide (NHS) was undertaken for cross-linking antibody of β-amyloid 42 to the carboxylic groups on one end of the MPA. The antibody concentration of β-amyloid 42 used was 18.75 µg/mL. The concentration range of β-amyloid 42 in this study was from 0.0675 µg/mL to 0.5 µg/mL for both PBS and undiluted human serum. DPV measurements showed excellent response in this antigen concentration range. Interference study of this biosensor was carried out in the presence of Tau protein antigen. Excellent specificity of this β-amyloid 42 biosensor was demonstrated without interference from other species, such as T-tau protein.

Time Multiplexed Active Neural Probe with 1356 Parallel Recording Sites

PubMed Central

Raducanu, Bogdan C.; Yazicioglu, Refet F.; Lopez, Carolina M.; Putzeys, Jan; Andrei, Alexandru; Rochus, Veronique; Welkenhuysen, Marleen; van Helleputte, Nick; Musa, Silke; Puers, Robert; Kloosterman, Fabian; Van Hoof, Chris; Mitra, Srinjoy

2017-01-01

We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated in-situ circuits for signal source amplification, which are directly located under each electrode. The probe supports the simultaneous recording of all 1356 electrodes with sufficient signal to noise ratio for typical neuroscience applications. For enhanced performance, further noise reduction can be achieved while using half of the electrodes (678). Both of these numbers considerably surpass the state-of-the art active neural probes in both electrode count and number of recording channels. The measured input referred noise in the action potential band is 12.4 µVrms, while using 678 electrodes, with just 3 µW power dissipation per pixel and 45 µW per read-out channel (including data transmission). PMID:29048396

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

NASA Astrophysics Data System (ADS)

Abrar, Md Abu; Dong, Yue; Lee, Paul Kyuheon; Kim, Woo Soo

2016-07-01

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration.

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

PubMed Central

Abrar, Md Abu; Dong, Yue; Lee, Paul Kyuheon; Kim, Woo Soo

2016-01-01

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration. PMID:27465437

Electrochemical microfluidic chip based on molecular imprinting technique applied for therapeutic drug monitoring.

PubMed

Liu, Jiang; Zhang, Yu; Jiang, Min; Tian, Liping; Sun, Shiguo; Zhao, Na; Zhao, Feilang; Li, Yingchun

2017-05-15

In this work, a novel electrochemical detection platform was established by integrating molecularly imprinting technique with microfluidic chip and applied for trace measurement of three therapeutic drugs. The chip foundation is acrylic panel with designed grooves. In the detection cell of the chip, a Pt wire is used as the counter electrode and reference electrode, and a Au-Ag alloy microwire (NPAMW) with 3D nanoporous surface modified with electro-polymerized molecularly imprinted polymer (MIP) film as the working electrode. Detailed characterization of the chip and the working electrode was performed, and the properties were explored by cyclic voltammetry and electrochemical impedance spectroscopy. Two methods, respectively based on electrochemical catalysis and MIP/gate effect were employed for detecting warfarin sodium by using the prepared chip. The linearity of electrochemical catalysis method was in the range of 5×10 -6 -4×10 -4 M, which fails to meet clinical testing demand. By contrast, the linearity of gate effect was 2×10 -11 -4×10 -9 M with remarkably low detection limit of 8×10 -12 M (S/N=3), which is able to satisfy clinical assay. Then the system was applied for 24-h monitoring of drug concentration in plasma after administration of warfarin sodium in rabbit, and the corresponding pharmacokinetic parameters were obtained. In addition, the microfluidic chip was successfully adopted to analyze cyclophosphamide and carbamazepine, implying its good versatile ability. It is expected that this novel electrochemical microfluidic chip can act as a promising format for point-of-care testing via monitoring different analytes sensitively and conveniently. Copyright © 2017 Elsevier B.V. All rights reserved.

Humidity-resistant ambient-temperature solid-electrolyte amperometric sensing apparatus and methods

DOEpatents

Zaromb, Solomon

2001-01-01

Apparatus and methods for detecting selected chemical compounds in air or other gas streams at room or ambient temperature includes a liquid-free humidity-resistant amperometric sensor comprising a sensing electrode and a counter and reference electrode separated by a solid electrolyte. The sensing electrode preferably contains a noble metal, such as Pt black. The electrolyte is water-free, non-hygroscopic, and substantially water-insoluble, and has a room temperature ionic conductivity .gtoreq.10.sup.-4 (ohm-cm).sup.-1, and preferably .gtoreq.0.01 (ohm-cm).sup.-1. The conductivity may be due predominantly to Ag+ ions, as in Ag.sub.2 WO.sub.4.4AgI, or to F- ions, as in Ce.sub.0.95 Ca.sub.0.05 F.sub.2.95. Electrical contacts serve to connect the electrodes to potentiostating and detecting circuitry which controls the potential of the sensing electrode relative to the reference electrode, detects the signal generated by the sensor, and indicates the detected signal.

Humidity-resistant ambient-temperature solid-electrolyte amperometric sensing apparatus

DOEpatents

Zaromb, Solomon

1994-01-01

Apparatus and methods for detecting selected chemical compounds in air or other gas streams at room or ambient temperature includes a liquid-free humidity-resistant amperometric sensor comprising a sensing electrode and a counter and reference electrode separated by a solid electrolyte. The sensing electrode preferably contains a noble metal, such as Pt black. The electrolyte is water-free, non-hygroscopic, and substantially water-insoluble, and has a room temperature ionic conductivity .gtoreq.10.sup.-4 (ohm-cm).sup.-1, and preferably .gtoreq.0.01 (ohm-cm).sup.-1. The conductivity may be due predominantly to Ag+ ions, as in Ag.sub.2 WO.sub.4.4AgI, or to F- ions, as in Ce.sub.0.95 Ca.sub.0.05 F.sub.2.95. Electrical contacts serve to connect the electrodes to potentiostating and detecting circuitry which controls the potential of the sensing electrode relative to the reference electrode, detects the signal generated by the sensor, and indicates the detected signal.

Photogrammetry-Based Head Digitization for Rapid and Accurate Localization of EEG Electrodes and MEG Fiducial Markers Using a Single Digital SLR Camera.

PubMed

Clausner, Tommy; Dalal, Sarang S; Crespo-García, Maité

2017-01-01

The performance of EEG source reconstruction has benefited from the increasing use of advanced head modeling techniques that take advantage of MRI together with the precise positions of the recording electrodes. The prevailing technique for registering EEG electrode coordinates involves electromagnetic digitization. However, the procedure adds several minutes to experiment preparation and typical digitizers may not be accurate enough for optimal source reconstruction performance (Dalal et al., 2014). Here, we present a rapid, accurate, and cost-effective alternative method to register EEG electrode positions, using a single digital SLR camera, photogrammetry software, and computer vision techniques implemented in our open-source toolbox, janus3D . Our approach uses photogrammetry to construct 3D models from multiple photographs of the participant's head wearing the EEG electrode cap. Electrodes are detected automatically or semi-automatically using a template. The rigid facial features from these photo-based models are then surface-matched to MRI-based head reconstructions to facilitate coregistration to MRI space. This method yields a final electrode coregistration error of 0.8 mm, while a standard technique using an electromagnetic digitizer yielded an error of 6.1 mm. The technique furthermore reduces preparation time, and could be extended to a multi-camera array, which would make the procedure virtually instantaneous. In addition to EEG, the technique could likewise capture the position of the fiducial markers used in magnetoencephalography systems to register head position.

Photogrammetry-Based Head Digitization for Rapid and Accurate Localization of EEG Electrodes and MEG Fiducial Markers Using a Single Digital SLR Camera

PubMed Central

Clausner, Tommy; Dalal, Sarang S.; Crespo-García, Maité

2017-01-01

The performance of EEG source reconstruction has benefited from the increasing use of advanced head modeling techniques that take advantage of MRI together with the precise positions of the recording electrodes. The prevailing technique for registering EEG electrode coordinates involves electromagnetic digitization. However, the procedure adds several minutes to experiment preparation and typical digitizers may not be accurate enough for optimal source reconstruction performance (Dalal et al., 2014). Here, we present a rapid, accurate, and cost-effective alternative method to register EEG electrode positions, using a single digital SLR camera, photogrammetry software, and computer vision techniques implemented in our open-source toolbox, janus3D. Our approach uses photogrammetry to construct 3D models from multiple photographs of the participant's head wearing the EEG electrode cap. Electrodes are detected automatically or semi-automatically using a template. The rigid facial features from these photo-based models are then surface-matched to MRI-based head reconstructions to facilitate coregistration to MRI space. This method yields a final electrode coregistration error of 0.8 mm, while a standard technique using an electromagnetic digitizer yielded an error of 6.1 mm. The technique furthermore reduces preparation time, and could be extended to a multi-camera array, which would make the procedure virtually instantaneous. In addition to EEG, the technique could likewise capture the position of the fiducial markers used in magnetoencephalography systems to register head position. PMID:28559791

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

PubMed Central

Nigl, Thomas P.; Smith, Nathan D.; Lichtenstein, Timothy; Gesualdi, Jarrod; Kumar, Kuldeep; Kim, Hojong

2017-01-01

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition. PMID:29155770

A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS

NASA Astrophysics Data System (ADS)

Faria, Paula; Hallett, Mark; Cavaleiro Miranda, Pedro

2011-12-01

We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm2), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.

The Rechargeability of Silicon-Air Batteries

DTIC Science & Technology

2012-06-01

demand the use of a more stable and accurate reference electrode. The method for constructing such an electrode was chosen to be based on the ferrocene ...three weeks-old electrode, as presented in figure 5b. These findings may be ascribed to some deterioration processes of ferrocene with

Sensor-actuator system for dynamic chloride ion determination.

PubMed

de Graaf, Derk Balthazar; Abbas, Yawar; Gerrit Bomer, Johan; Olthuis, Wouter; van den Berg, Albert

2015-08-12

Chloride is a crucial anion for various analytical applications from biological to environmental applications. In order to measure the chloride ion concentration, a measurement system is needed which can detect this concentration for prolonged times reliably. Chronopotentiometry is a technique which does not need a long term stable reference electrode and is therefore very suitable for prolonged ion concentration measurements. As the used electrode might be fouled by reaction products, this work focuses on a chronopotentiometric approach with a separated sensing electrode (sensor) and actuating electrode (actuator). Both actuation and sensor electrode are made of Ag/AgCl. A constant current is applied to the actuator and will start the reaction between Ag and Cl-, while the resulting Cl- ion concentration change is observed through the sensor, which is placed close to the actuator. The time it takes to locally deplete the Cl- ions is called transition time. Experiments were performed to verify the feasibility of this approach. The performed experiments show that the sensor detects the local concentration changes resulting from the current applied to the actuator. A linear relation between the Cl- ion concentration and the square root of the transition time was observed, just as was predicted by theory. The calibration curves for different chips showed that both a larger sensor and a larger distance between sensor and actuator resulted in a larger time delay between the transition time detected at the actuator and the sensor. Copyright © 2015 Elsevier B.V. All rights reserved.

Surgical anatomy of the round window-Implications for cochlear implantation.

PubMed

Luers, J C; Hüttenbrink, K B; Beutner, D

2018-04-01

The round window is an important portal for the application of active hearing aids and cochlear implants. The anatomical and topographical knowledge about the round window region is a prerequisite for successful insertion for a cochlear implant electrode. To sum up current knowledge about the round window anatomy and to give advice to the cochlear implant surgeon for optimal placement of an electrode. Systematic Medline search. Search term "round window[Title]" with no date restriction. Only publications in the English Language were included. All abstracts were screened for relevance, that is a focus on surgical anatomy of the round window. The search results were supplemented with hand searching of selected reviews and reference lists from included studies. Subjective assessment. There is substantial variability in size and shape of the round window. The round window is regarded as the most reliable surgical landmark to safely locate the scala tympani. Factors affecting the optimal trajectory line for atraumatic electrode insertion are anatomy of the round window, the anatomy of the intracochlear hook region and the variable orientation and size of the cochlea's basal turn. The very close relation to the sensitive inner ear structures necessitates a thorough anatomic knowledge and careful insertion technique, especially when implanting patients with residual hearing. In order to avoid electrode migration between the scalae and to achieve protect the modiolus and the basilar membrane, it is recommended to aim for an electrode insertion vector from postero-superior to antero-inferior. © 2017 John Wiley & Sons Ltd.

Fundamental electrode kinetics

NASA Technical Reports Server (NTRS)

Elder, J. P.

1968-01-01

Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

Evaluation of molecular dynamics simulation methods for ionic liquid electric double layers.

PubMed

Haskins, Justin B; Lawson, John W

2016-05-14

We investigate how systematically increasing the accuracy of various molecular dynamics modeling techniques influences the structure and capacitance of ionic liquid electric double layers (EDLs). The techniques probed concern long-range electrostatic interactions, electrode charging (constant charge versus constant potential conditions), and electrolyte polarizability. Our simulations are performed on a quasi-two-dimensional, or slab-like, model capacitor, which is composed of a polarizable ionic liquid electrolyte, [EMIM][BF4], interfaced between two graphite electrodes. To ensure an accurate representation of EDL differential capacitance, we derive new fluctuation formulas that resolve the differential capacitance as a function of electrode charge or electrode potential. The magnitude of differential capacitance shows sensitivity to different long-range electrostatic summation techniques, while the shape of differential capacitance is affected by charging technique and the polarizability of the electrolyte. For long-range summation techniques, errors in magnitude can be mitigated by employing two-dimensional or corrected three dimensional electrostatic summations, which led to electric fields that conform to those of a classical electrostatic parallel plate capacitor. With respect to charging, the changes in shape are a result of ions in the Stern layer (i.e., ions at the electrode surface) having a higher electrostatic affinity to constant potential electrodes than to constant charge electrodes. For electrolyte polarizability, shape changes originate from induced dipoles that soften the interaction of Stern layer ions with the electrode. The softening is traced to ion correlations vertical to the electrode surface that induce dipoles that oppose double layer formation. In general, our analysis indicates an accuracy dependent differential capacitance profile that transitions from the characteristic camel shape with coarser representations to a more diffuse profile with finer representations.

Electrolytic cell with reference electrode

DOEpatents

Kessie, Robert W.

1989-01-01

A reference electrode device is provided for a high temperature electrolytic cell used to electrolytically recover uranium from spent reactor fuel dissolved in an anode pool, the device having a glass tube to enclose the electrode and electrolyte and serve as a conductive membrane with the cell electrolyte, and an outer metal tube about the glass tube to serve as a shield and basket for any glass sections broken by handling of the tube to prevent their contact with the anode pool, the metal tube having perforations to provide access between the bulk of the cell electrolyte and glass membrane.

Reference electrode for electrolytic cell

DOEpatents

Kessie, R.W.

1988-07-28

A reference electrode device is provided for a high temperature electrolytic cell used to electrolytically recover uranium from spent reactor fuel dissolved in an anode pool, the device having a glass tube to enclose the electrode and electrolyte and serve as a conductive membrane with the cell electrolyte, and an outer metal tube about the glass tube to serve as a shield and basket for any glass sections broken by handling of the tube to prevent their contact with the anode pool, the metal tube having perforations to provide access between the bulk of the cell electrolyte and glass membrane. 4 figs.

Bending Properties of Nickel Electrodes for Nickel-Hydrogen Batteries

NASA Technical Reports Server (NTRS)

Lerch, Brad A.; Wilson, Richard M.; Keller, Dennis; Corner, Ralph

1995-01-01

Recent changes in manufacturing have resulted in nickel-hydrogen batteries that fail prematurely by electrical shorting, This failure is believed to be a result of a blistering problem in the nickel electrodes. In this study the bending properties of nickel electrodes are investigated in an attempt to correlate the bending properties of the electrode with its propensity to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. The effects of specimen curvature and position within the electrode on the bending strength were studied, and within-electrode and batch-to-batch variations were addressed. Two color-imaging techniques were employed to differentiate between the phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hyroxide surface loading on each electrode, thereby relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading.

Event-Related Potential Responses to Task Switching Are Sensitive to Choice of Spatial Filter

PubMed Central

Wong, Aaron S. W.; Cooper, Patrick S.; Conley, Alexander C.; McKewen, Montana; Fulham, W. Ross; Michie, Patricia T.; Karayanidis, Frini

2018-01-01

Event-related potential (ERP) studies using the task-switching paradigm show that multiple ERP components are modulated by activation of proactive control processes involved in preparing to repeat or switch task and reactive control processes involved in implementation of the current or new task. Our understanding of the functional significance of these ERP components has been hampered by variability in their robustness, as well as their temporal and scalp distribution across studies. The aim of this study is to examine the effect of choice of reference electrode or spatial filter on the number, timing and scalp distribution of ERP elicited during task-switching. We compared four configurations, including the two most common (i.e., average mastoid reference and common average reference) and two novel ones that aim to reduce volume conduction (i.e., reference electrode standardization technique (REST) and surface Laplacian) on mixing cost and switch cost effects in cue-locked and target-locked ERP waveforms in 201 healthy participants. All four spatial filters showed the same well-characterized ERP components that are typically seen in task-switching paradigms: the cue-locked switch positivity and target-locked N2/P3 effect. However, both the number of ERP effects associated with mixing and switch cost, and their temporal and spatial resolution were greater with the surface Laplacian transformation which revealed rapid temporal adjustments that were not identifiable with other spatial filters. We conclude that the surface Laplacian transformation may be more suited to characterize EEG signatures of complex spatiotemporal networks involved in cognitive control. PMID:29568260

Application of the shaped electrode technique to a large area rectangular capacitively coupled plasma reactor to suppress standing wave nonuniformity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sansonnens, L.; Schmidt, H.; Howling, A.A.

The electromagnetic standing wave effect can become the main source of nonuniformity limiting the use of very high frequency in large area reactors exceeding 1 m{sup 2} required for industrial applications. Recently, it has been proposed and shown experimentally in a cylindrical reactor that a shaped electrode in place of the conventional flat electrode can be used in order to suppress the electromagnetic standing wave nonuniformity. In this study, we show experimental measurements demonstrating that the shaped electrode technique can also be applied in large area rectangular reactors. We also present results of electromagnetic screening by a conducting substrate whichmore » has important consequences for industrial application of the shaped electrode technique.« less

Detecting the presence of microorganisms

NASA Technical Reports Server (NTRS)

Wilkins, Judd R. (Inventor); Stoner, Glenn E. (Inventor)

1977-01-01

The presence of microorganisms in a sample is determined by culturing microorganisms in a growth medium which is in contact with a measuring electrode and a reference electrode and detecting a change in potential between the electrodes caused by the presence of the microorganisms in the medium with a high impedance potentiometer.

The cadmium electrode: Review of the status of research

NASA Technical Reports Server (NTRS)

Gross, S.; Glockling, R. J.

1976-01-01

Investigations characterizing the negative cadmium electrode used in a nickel cadmium battery cell are summarized with citations to references where more detailed information is available. Emphasis is placed on data pertinent to aerospace applications. An evaluation of some of the published results of cadmium electrode research is included.

Modification of Patterned Nanoporous Gold Thin Film Electrodes via Electro-annealing and Electrochemical Etching

NASA Astrophysics Data System (ADS)

Dorofeeva, Tatiana

Nanostructured materials have had a major impact on various fields, including medicine, catalysis, and energy storage, for the major part due to unique phenomena that arise at nanoscale. For this reason, there is a sustained need for new nanostructured materials, techniques to pattern them, and methods to precisely control their nanostructure. To that end, the primary focus of this dissertation is to demonstrate novel techniques to fabricate and tailor the morphology of a class of nanoporous metals, obtained by a process known as dealloying. In this process, while the less noble constituent of an alloy is chemically dissolved, surface-diffusion of the more noble constituent leads to self-assembly of a bicontinuous ligament network with characteristic porosity of ˜70% and ligament diameter of 10s of nanometers. As a model material produced by dealloying, this work employ nanoporous gold (np-Au), which has attracted significant attention of desirable features, such as high effective surface area, electrical conductivity, well-defined thiol-based surface modification strategies, microfabrication-compatibility, and biocompatibility. The most commonly method used to modify the morphology of np-Au is thermal treatment, where the enhanced diffusivity of the surface atoms leads to ligament (and consequently pore) coarsening. This method, however, is not conducive to modifying the morphology of thin films at specific locations on the film, which is necessary for creating devices that may need to contain different morphologies on a single device. In addition, coarsening attained by thermal treatment also leads to an undesirable reduction in effective surface area. In response to these challenges, this work demonstrates two different techniques that enables in situ modification of np-Au thin film electrodes obtained by sputter-deposition of a precursors silver-rich gold-silver alloy. The first method, referred to as electro-annealing, is achieved by injecting electrical current to np-Au electrodes, which leads coarsening due to a combination of Joule heating and other mechanisms. This method offers the capability to anneal different electrodes to varying degrees of coarsening in one step, by employing electrodes patterns with different cross-sectional areas - easily attained since np-Au can be patterned into arbitrary shapes via photolithography - to control electrode resistivity, thus current density and the amount of electro-annealing of an electrode. A surprising finding was that electro-annealing lead to electrode coarsening at much lower temperatures than conventional thermal treatment, which was attributed to augmented electron-surface atom interactions at high current densities that may in turn enhance surface atom diffusivity. A major advantage of electro-annealing is the ability to monitor the resistance change of the electrode (surrogate for electrode morphology) in real-time and vary the electro-annealing current accordingly to establish a closed-loop electro-annealing configuration. In nanostructured materials, the electrical resistance is often a function of nanostructure, thus changes in resistance can be directly linked to morphological changes of the electrode. Examination of the underlying mechanisms of nanostructure-dependent resistance change revealed that both ligament diameter and grain size play a role in dictating the observed electrode resistance change. The second method relies on electrochemical etching of ligaments to modify electrode morphology in order to maintain both a high effective surface area and large pores for unhindered transport of molecules to/from the ligament surfaces - an important consideration for many physico-chemical processes, such fuel cells, electrochemical sensors, and drug delivery platforms. The advantage of this method over purely chemical approach is that while an entire sample in exposed to the chemical reagent, the etching process does not occur until the necessary electrochemical potential is applied. Similar to the electro-annealing methods, electrical addressability allows for differentially modifying the morphology individual electrodes on a single substrate. The results of this study also revealed that electrochemical etching is a combination of coarsening and etching processes, where the optimization of etching parameters makes it possible precisely control the etching by favoring one process over the other. In summary, the two techniques, taken together in combination with np-Au's compatibility with microfabrication processes, can be extended to create multiple electrode arrays that display different morphologies for studying structure?property relationships and tuning catalysts/sensors for optimal performance.

Collection of ions

DOEpatents

Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore; Bounds, John Alan; Koster, James E.

2001-01-01

The apparatus and method provide an improved technique for detecting ions as the area from which ions are attracted to a detector is increased, consequently increasing the number of ions detected. This is achieved by providing the outer electrodes of the detector connected to the electrical potential, together with alternate intermediate electrodes. The other intermediate electrodes and preferably the housing are grounded. The technique renders such detection techniques more sensitive and gives them a lower threshold at which they can function.

Selenium containing conducting polymer based pyranose oxidase biosensor for glucose detection.

PubMed

Gokoglan, Tugba Ceren; Soylemez, Saniye; Kesik, Melis; Toksabay, Sinem; Toppare, Levent

2015-04-01

A novel amperometric pyranose oxidase (PyOx) biosensor based on a selenium containing conducting polymer has been developed for the glucose detection. For this purpose, a conducting polymer; poly(4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5] selenadiazole) (poly(BSeTT)) was synthesized via electropolymerisation on gold electrode to examine its matrix property for glucose detection. For this purpose, PyOx was used as the model enzyme and immobilised via physical adsorption technique. Amperometric detection of consumed oxygen was monitored at -0.7 V vs Ag reference electrode in a phosphate buffer (50 mM, pH 7.0). K(M)(app), Imax, LOD and sensitivity were calculated as 0.229 mM, 42.37 nA, 3.3 × 10(-4)nM and 6.4 nA/mM cm(2), respectively. Scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to monitor changes in surface morphologies and to run electrochemical characterisations. Finally, the constructed biosensor was applied for the determination of glucose in beverages successfully. Copyright © 2014 Elsevier Ltd. All rights reserved.

Influence of Gap Distance on Vacuum Arc Characteristics of Cup Type AMF Electrode in Vacuum Interrupters

NASA Astrophysics Data System (ADS)

Cheng, Shaoyong; Xiu, Shixin; Wang, Jimei; Shen, Zhengchao

2006-11-01

The greenhouse effect of SF6 is a great concern today. The development of high voltage vacuum circuit breakers becomes more important. The vacuum circuit breaker has minimum pollution to the environment. The vacuum interrupter is the key part of a vacuum circuit breaker. The interrupting characteristics in vacuum and arc-controlling technique are the main problems to be solved for a longer gap distance in developing high voltage vacuum interrupters. To understand the vacuum arc characteristics and provide effective technique to control vacuum arc in a long gap distance, the arc mode transition of a cup-type axial magnetic field electrode is observed by a high-speed charge coupled device (CCD) video camera under different gap distances while the arc voltage and arc current are recorded. The controlling ability of the axial magnetic field on vacuum arc obviously decreases when the gap distance is longer than 40 mm. The noise components and mean value of the arc voltage significantly increase. The effective method for controlling the vacuum arc characteristics is provided by long gap distances based on the test results. The test results can be used as a reference to develop high voltage and large capacity vacuum interrupters.

Fabric-based active electrode design and fabrication for health monitoring clothing.

PubMed

Merritt, Carey R; Nagle, H Troy; Grant, Edward

2009-03-01

In this paper, two versions of fabric-based active electrodes are presented to provide a wearable solution for ECG monitoring clothing. The first version of active electrode involved direct attachment of surface-mountable components to a textile screen-printed circuit using polymer thick film techniques. The second version involved attaching a much smaller, thinner, and less obtrusive interposer containing the active electrode circuitry to a simplified textile circuit. These designs explored techniques for electronic textile interconnection, chip attachment to textiles, and packaging of circuits on textiles for durability. The results from ECG tests indicate that the performance of each active electrode is comparable to commercial Ag/AgCl electrodes. The interposer-based active electrodes survived a five-cycle washing test while maintaining good signal integrity.

Monitoring the fetal heart rate variability during labor.

PubMed

Moslem, B; Mohydeen, A; Bazzi, O

2015-08-01

In respect to the main goal of our ongoing work for estimating the heart rate variability (HRV) from fetal electrocardiogram (FECG) signals for monitoring the health of the fetus, we investigate in this paper the possibility of extracting the fetal heart rate variability (HRV) directly from the abdominal composite recordings. Our proposed approach is based on a combination of two techniques: Periodic Component Analysis (PiCA) and recursive least square (RLS) adaptive filtering. The Fetal HRV of the estimated FECG signal is compared to a reference value extracted from an FECG signal recorded by using a spiral electrode attached directly to the fetal scalp. The results obtained show that the fetal HRV can be directly evaluated from the abdominal composite recordings without the need of recording an external reference signal.

Ballistocardiogram Artifact Removal with a Reference Layer and Standard EEG Cap

PubMed Central

Luo, Qingfei; Huang, Xiaoshan; Glover, Gary H.

2014-01-01

Background In simultaneous EEG-fMRI, the EEG recordings are severely contaminated by ballistocardiogram (BCG) artifacts, which are caused by cardiac pulsations. To reconstruct and remove the BCG artifacts, one promising method is to measure the artifacts in the absence of EEG signal by placing a group of electrodes (BCG electrodes) on a conductive layer (reference layer) insulated from the scalp. However, current BCG reference layer (BRL) methods either use a customized EEG cap composed of electrode pairs, or need to construct the custom reference layer through additional model-building experiments for each EEG-fMRI experiment. These requirements have limited the versatility and efficiency of BRL. The aim of this study is to propose a more practical and efficient BRL method and compare its performance with the most popular BCG removal method, the optimal basis sets (OBS) algorithm. New Method By designing the reference layer as a permanent and reusable cap, the new BRL method is able to be used with a standard EEG cap, and no extra experiments and preparations are needed to use the BRL in an EEG-fMRI experiment. Results The BRL method effectively removed the BCG artifacts from both oscillatory and evoked potential scalp recordings and recovered the EEG signal. Comparison with Existing Method Compared to the OBS, this new BRL method improved the contrast-to-noise ratios of the alpha-wave, visual, and auditory evoked potential signals by 101%, 76%, and 75% respectively, employing 160 BCG electrodes. Using only 20 BCG electrodes, the BRL improved the EEG signal by 74%/26%/41% respectively. Conclusion The proposed method can substantially improve the EEG signal quality compared with traditional methods. PMID:24960423

A 100 electrode intracortical array: structural variability.

PubMed

Campbell, P K; Jones, K E; Normann, R A

1990-01-01

A technique has been developed for fabricating three dimensional "hair brush" electrode arrays from monocrystalline silicon blocks. Arrays consist of a square pattern of 100 penetrating electrodes, with 400 microns interelectrode spacing. Each electrode is 1.5mm in length and tapers from about 100 microns at its base to a sharp point at the tip. The tips of each electrode are coated with platinum and the entire structure, with the exception of the tips, is insulated with polyimide. Electrical connection to selected electrodes is made by wire bonding polyimide insulated 25 microns diameter gold lead wires to bonding pads on the rear surface of the array. As the geometrical characteristics of the electrodes in such an aray will influence their electrical properties (such as impedance, capacitance, spreading resistance in an electrolyte, etc.) it is desirable that such an array have minimal variability in geometry from electrode to electrode. A study was performed to determine the geometrical variability resulting from our micromachining techniques. Measurements of the diameter of each of the 100 electrodes were made at various planes above the silicon substrate of the array. For the array that was measured, the standard deviation of the diameters was approximately 9% of the mean diameter near the tip, 8% near the middle, and 6% near the base. We describe fabrication techniques which should further reduce these variabilities.

Development of Gold Standard Ion-Selective Electrode-Based Methods for Fluoride Analysis

PubMed Central

Martínez-Mier, E.A.; Cury, J.A.; Heilman, J.R.; Katz, B.P.; Levy, S.M.; Li, Y.; Maguire, A.; Margineda, J.; O’Mullane, D.; Phantumvanit, P.; Soto-Rojas, A.E.; Stookey, G.K.; Villa, A.; Wefel, J.S.; Whelton, H.; Whitford, G.M.; Zero, D.T.; Zhang, W.; Zohouri, V.

2011-01-01

Background/Aims: Currently available techniques for fluoride analysis are not standardized. Therefore, this study was designed to develop standardized methods for analyzing fluoride in biological and nonbiological samples used for dental research. Methods A group of nine laboratories analyzed a set of standardized samples for fluoride concentration using their own methods. The group then reviewed existing analytical techniques for fluoride analysis, identified inconsistencies in the use of these techniques and conducted testing to resolve differences. Based on the results of the testing undertaken to define the best approaches for the analysis, the group developed recommendations for direct and microdiffusion methods using the fluoride ion-selective electrode. Results Initial results demonstrated that there was no consensus regarding the choice of analytical techniques for different types of samples. Although for several types of samples, the results of the fluoride analyses were similar among some laboratories, greater differences were observed for saliva, food and beverage samples. In spite of these initial differences, precise and true values of fluoride concentration, as well as smaller differences between laboratories, were obtained once the standardized methodologies were used. Intraclass correlation coefficients ranged from 0.90 to 0.93, for the analysis of a certified reference material, using the standardized methodologies. Conclusion The results of this study demonstrate that the development and use of standardized protocols for F analysis significantly decreased differences among laboratories and resulted in more precise and true values. PMID:21160184

Thermal transport in lithium ion batteries: An experimental investigation of interfaces and granular materials

NASA Astrophysics Data System (ADS)

Gaitonde, Aalok Jaisheela Uday

Increasing usage and recent accidents due to lithium-ion (Li-ion) batteries exploding or catching on fire has inspired research on the characterization and thermal management of these batteries. In cylindrical 18650 cells, heat generated during the battery's charge/discharge cycle is poorly dissipated to the surrounding through its metallic case due to the poor thermal conductivity of the jelly roll, which is spirally wound with many interfaces between electrodes and the polymeric separator. This work presents a technique to measure the thermal conduction across the metallic case-plastic separator interface, which ultimately limits heat transfer out of the jelly roll. The polymeric separator and metallic case are harvested from discharged commercial 18650 battery cells for thermal testing. A miniaturized version of the reference bar method enables measurements of the interface resistance between the case and the separator by establishing a temperature gradient across a multilayer stack consisting of two reference layers of known thermal conductivity and the case-separator sample. The case-separator interfacial conductance is reported for a range of case temperatures and interface pressures. The mean thermal conductance across the case-separator interface is 670 +/- 275 W/(m2K) and no significant temperature or pressure dependence is observed. The effective thermal conductivity of the battery stack is measured to be 0.27 W/m/K and 0.32 W/m/K in linear and radial configurations, respectively. Many techniques for fabricating battery electrodes involve coating particles of the active materials on metallic current collectors. The impact of mechanical shearing on the resultant thermal properties of these packed particle beds during the fabrication process has not yet been studied. Thus, the final portion of this thesis designs and validates a measurement system to measure the effects of mechanical shearing on the thermal conductivity of packed granular beds. This system simultaneously shears the sample while applying a temperature gradient across the particle bed, enabling thermal conductivity measurements using a radial equivalent of the conventional reference bar method. Results of this research, which includes characterization of thermal conductance across the rate limiting separator-case interface, will help improve the design and reliability of lithium ion batteries. Cells of larger dimension and capacity could also be achieved by the improved understanding of thermal transport across the microscopic electrode stack. Better analytic models of the thermal response of the batteries could be constructed, by taking into account the interfacial conductance and thermal conductivity of the electrodes measured in this work. This is of particular importance in the current circumstances, where accidents and safety issues related to lithium ion batteries are on the increase.

Voltammetric analysis apparatus and method

DOEpatents

Almon, A.C.

1993-06-08

An apparatus and method is described for electrochemical analysis of elements in solution. An auxiliary electrode, a reference electrode, and five working electrodes are positioned in a container containing a sample solution. The working electrodes are spaced apart evenly from each other and the auxiliary electrode to minimize any inter-electrode interference that may occur during analysis. An electric potential is applied between the auxiliary electrode and each of the working electrodes. Simultaneous measurements taken of the current flow through each of the working electrodes for each given potential in a potential range are used for identifying chemical elements present in the sample solution and their respective concentrations. Multiple working electrodes enable a more positive identification to be made by providing unique data characteristic of chemical elements present in the sample solution.

A trial of ignition innovation of gasoline engine by nanosecond pulsed low temperature plasma ignition

NASA Astrophysics Data System (ADS)

Shiraishi, Taisuke; Urushihara, Tomonori; Gundersen, Martin

2009-07-01

Application of nanosecond pulsed low temperature plasma as an ignition technique for automotive gasoline engines, which require a discharge under conditions of high back pressure, has been studied experimentally using a single-cylinder engine. The nanosecond pulsed plasma refers to the transient (non-equilibrated) phase of a plasma before the formation of an arc discharge; it was obtained by applying a high voltage with a nanosecond pulse (FWHM of approximately 80 or 25 ns) between coaxial cylindrical electrodes. It was confirmed that nanosecond pulsed plasma can form a volumetric multi-channel streamer discharge at an energy consumption of 60 mJ cycle-1 under a high back pressure of 1400 kPa. It was found that the initial combustion period was shortened compared with the conventional spark ignition. The initial flame visualization suggested that the nanosecond pulsed plasma ignition results in the formation of a spatially dispersed initial flame kernel at a position of high electric field strength around the central electrode. It was observed that the electric field strength in the air gap between the coaxial cylindrical electrodes was increased further by applying a shorter pulse. It was also clarified that the shorter pulse improved ignitability even further.

Postmortem diffusion MRI of the human brainstem and thalamus for deep brain stimulator electrode localization

PubMed Central

Calabrese, Evan; Hickey, Patrick; Hulette, Christine; Zhang, Jingxian; Parente, Beth; Lad, Shivanand P.; Johnson, G. Allan

2015-01-01

Deep brain stimulation (DBS) is an established surgical therapy for medically refractory tremor disorders including essential tremor (ET) and is currently under investigation for use in a variety of other neurologic and psychiatric disorders. There is growing evidence that the anti-tremor effects of DBS for ET are directly related to modulation of the dentatorubrothalamic tract (DRT), a white matter pathway that connects the cerebellum, red nucleus, and ventral intermediate nucleus of the thalamus. Emerging white matter targets for DBS, like the DRT, will require improved 3D reference maps of deep brain anatomy and structural connectivity for accurate electrode targeting. High-resolution diffusion MRI of postmortem brain specimens can provide detailed volumetric images of important deep brain nuclei and 3D reconstructions of white matter pathways with probabilistic tractography techniques. We present a high spatial and angular resolution diffusion MRI template of the postmortem human brainstem and thalamus with 3D reconstructions of the nuclei and white matter tracts involved in ET circuitry. We demonstrate accurate registration of these data to in vivo, clinical images from patients receiving DBS therapy, and correlate electrode proximity to tractography of the DRT with improvement of ET symptoms. PMID:26043869

Microelectrodes in microbial ecology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boots, S.

1989-03-15

Understanding the microenvironment of bacteria has presented many challenges for the microbial ecologist. Simple intracellular capillary electrodes have been used in neurophysiology since the 1950s to measure action potentials in ion transport over biological membranes, and ion-selective electrodes were developed soon thereafter for the determination of H{sup +}, Na{sup +}, K{sup +}, and Ca{sup 2+}. However, these analytical techniques did not receive much attention until 1978, when Niels Peter Revsbech and Bo Barker Joergensen at the Institute of Ecology and Genetics, University of Aarhus, Denmark, began using oxygen microelectrodes in their studies of the ecology and biogeochemistry of marine sedimentsmore » and other microbial environments. Today, Revsbech and Joergensen use five types of microelectrodes, two types of oxygen microelectrodes, a combined microelectrode for nitrous oxide and oxygen, a sulfide microelectrode, and a pH microelectrode. The first three microelectrodes have diameters of about 10 {mu}m and the last two of about 50 {mu}m. Some of the electrodes actually contain two or three cathodes plus a reference electrode, all situated behind a polymer membrane. In situ experiments have been done for several years at a water depth of several meters, where the micromanipulator is operated by a diver. Recently measurements were obtained in the deep sea with the microelectrodes mounted on a free-falling vehicle or operated from a submersible vessel.« less

Technique eliminates high voltage arcing at electrode-insulator contact area

NASA Technical Reports Server (NTRS)

Mealy, G.

1967-01-01

Coating the electrode-insulator contact area with silver epoxy conductive paint and forcing the electrode and insulator tightly together into a permanent connection, eliminates electrical arcing in high-voltage electrodes supplying electrical power to vacuum facilities.

Technique for the comparison of light spectra from natural and laboratory generated lightning current arcs

NASA Astrophysics Data System (ADS)

Mitchard, D.; Clark, D.; Carr, D.; Haddad, A.

2016-08-01

A technique was developed for the comparison of observed emission spectra from lightning current arcs generated through self-breakdown in air and the use of two types of initiation wire, aluminum bronze and nichrome, against previously published spectra of natural lightning events. A spectrograph system was used in which the wavelength of light emitted by the lightning arc was analyzed to derive elemental interactions. A lightning impulse of up to 100 kA was applied to a two hemispherical tungsten electrode configuration which allowed the effect of the lightning current and lightning arc length to be investigated. A natural lightning reference spectrum was reconstructed from literature, and generated lightning spectra were obtained from self-breakdown across a 14.0 mm air gap and triggered along initiation wires of length up to 72.4 mm. A comparison of the spectra showed that the generated lightning arc induced via self-breakdown produced a very similar spectrum to that of natural lightning, with the addition of only a few lines from the tungsten electrodes. A comparison of the results from the aluminum bronze initiation wire showed several more lines, whereas results from the nichrome initiation wire differed greatly across large parts of the spectrum. This work highlights the potential use for spectrographic techniques in the study of lightning interactions with surrounding media and materials, and in natural phenomena such as recently observed ball lightning.

The study of effect of solid electrolyte on charge-discharge characteristics of thin-film lithium-ion batteries

NASA Astrophysics Data System (ADS)

Mazaletskiy, L. A.; Lebedev, M. E.; Mironenko, A. A.; Naumov, V. V.; Novozhilova, A. V.; Fedorov, I. S.; Rudy, A. S.

2017-11-01

Results of studies of the solid electrolyte effect on capacitance of thin-film electrodes on the basis of Si-O-Al and VxOy nanocomposites are presented. The studies were carried out by comparing the charge-discharge characteristics of two pairs of the identical electrodes, one of which was covered by LiPON film, within prototypes with two lithium electrodes - the counter and the reference electrode.

RuO2 pH Sensor with Super-Glue-Inspired Reference Electrode

PubMed Central

Wajrak, Magdalena; Alameh, Kamal

2017-01-01

A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices. PMID:28878182

RuO₂ pH Sensor with Super-Glue-Inspired Reference Electrode.

PubMed

Lonsdale, Wade; Wajrak, Magdalena; Alameh, Kamal

2017-09-06

A pH-sensitive RuO₂ electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO₂ working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO₂ pH-sensitive working electrode and a SiO₂-PVB junction-modified RuO₂ reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices.

In vitro biocompatibility and electrical stability of thick-film platinum/gold alloy electrodes printed on alumina

NASA Astrophysics Data System (ADS)

Carnicer-Lombarte, Alejandro; Lancashire, Henry T.; Vanhoestenberghe, Anne

2017-06-01

Objective. High-density electrode arrays are a powerful tool in both clinical neuroscience and basic research. However, current manufacturing techniques require the use of specialised techniques and equipment, which are available to few labs. We have developed a high-density electrode array with customisable design, manufactured using simple printing techniques and with commercially available materials. Approach. Electrode arrays were manufactured by thick-film printing a platinum-gold alloy (Pt/Au) and an insulating dielectric on 96% alumina ceramic plates. Arrays were conditioned in serum and serum-free conditions, with and without 1 kHz, 200 µA, charge balanced stimulation for up to 21 d. Array biocompatibility was assessed using an extract assay and a PC-12 cell contact assay. Electrode impedance, charge storage capacity and charge injection capacity were before and after array conditioning. Main results. The manufactured Pt/Au electrodes have a highly porous surface and exhibit electrical properties comparable to arrays manufactured using alternative techniques. Materials used in array manufacture were found to be non-toxic to L929 fibroblasts by extract assay, and neuronal-like PC-12 cells adhered and extended neurites on the array surfaces. Arrays remained functional after long-term delivery of electrical pulses while exposed to protein-rich environments. Charge storage capacities and charge injection capacities increased following stimulation accounted for by an increase in surface index (real surface area) observed by vertical scanning interferometry. Further, we observed accumulation of proteins at the electrode sites following conditioning in the presence of serum. Significance. This study demonstrates the in vitro biocompatibility of commercially available thick-film printing materials. The printing technique is both simple and versatile, with layouts readily modified to produce customized electrode arrays. Thick-film electrode arrays are an attractive tool that may be implemented for general tissue engineering and neuroscience research.

Recursive grid partitioning on a cortical surface model: an optimized technique for the localization of implanted subdural electrodes.

PubMed

Pieters, Thomas A; Conner, Christopher R; Tandon, Nitin

2013-05-01

Precise localization of subdural electrodes (SDEs) is essential for the interpretation of data from intracranial electrocorticography recordings. Blood and fluid accumulation underneath the craniotomy flap leads to a nonlinear deformation of the brain surface and of the SDE array on postoperative CT scans and adversely impacts the accurate localization of electrodes located underneath the craniotomy. Older methods that localize electrodes based on their identification on a postimplantation CT scan with coregistration to a preimplantation MR image can result in significant problems with accuracy of the electrode localization. The authors report 3 novel methods that rely on the creation of a set of 3D mesh models to depict the pial surface and a smoothed pial envelope. Two of these new methods are designed to localize electrodes, and they are compared with 6 methods currently in use to determine their relative accuracy and reliability. The first method involves manually localizing each electrode using digital photographs obtained at surgery. This is highly accurate, but requires time intensive, operator-dependent input. The second uses 4 electrodes localized manually in conjunction with an automated, recursive partitioning technique to localize the entire electrode array. The authors evaluated the accuracy of previously published methods by applying the methods to their data and comparing them against the photograph-based localization. Finally, the authors further enhanced the usability of these methods by using automatic parcellation techniques to assign anatomical labels to individual electrodes as well as by generating an inflated cortical surface model while still preserving electrode locations relative to the cortical anatomy. The recursive grid partitioning had the least error compared with older methods (672 electrodes, 6.4-mm maximum electrode error, 2.0-mm mean error, p < 10(-18)). The maximum errors derived using prior methods of localization ranged from 8.2 to 11.7 mm for an individual electrode, with mean errors ranging between 2.9 and 4.1 mm depending on the method used. The authors also noted a larger error in all methods that used CT scans alone to localize electrodes compared with those that used both postoperative CT and postoperative MRI. The large mean errors reported with these methods are liable to affect intermodal data comparisons (for example, with functional mapping techniques) and may impact surgical decision making. The authors have presented several aspects of using new techniques to visualize electrodes implanted for localizing epilepsy. The ability to use automated labeling schemas to denote which gyrus a particular electrode overlies is potentially of great utility in planning resections and in corroborating the results of extraoperative stimulation mapping. Dilation of the pial mesh model provides, for the first time, a sense of the cortical surface not sampled by the electrode, and the potential roles this "electrophysiologically hidden" cortex may play in both eloquent function and seizure onset.

Fabrication and performance of Li4Ti5O12/C Li-ion battery electrodes using combined double flame spray pyrolysis and pressure-based lamination technique

NASA Astrophysics Data System (ADS)

Gockeln, Michael; Pokhrel, Suman; Meierhofer, Florian; Glenneberg, Jens; Schowalter, Marco; Rosenauer, Andreas; Fritsching, Udo; Busse, Matthias; Mädler, Lutz; Kun, Robert

2018-01-01

Reduction of lithium-ion battery (LIB) production costs is inevitable to make the use of LIB technology more viable for applications such as electric vehicles or stationary storage. To meet the requirements in today's LIB cost efficiency, our current research focuses on an alternative electrode fabrication method, characterized by a combination of double flame spray pyrolysis and lamination technique (DFSP/lamination). In-situ carbon coated nano-Li4Ti5O12 (LTO/C) was synthesized using versatile DFSP. The as-prepared composite powder was then directly laminated onto a conductive substrate avoiding the use of any solvent or binder for electrode preparation. The influence of lamination pressures on the microstructure and electrochemical performance of the electrodes was also investigated. Enhancements in intrinsic electrical conductivity were found for higher lamination pressures. Capacity retention of highest pressurized DFSP/lamination-prepared electrode was 87.4% after 200 dis-/charge cycles at 1C (vs. Li). In addition, LTO/C material prepared from the double flame spray pyrolysis was also used for fabricating electrodes via doctor blading technique. Laminated electrodes obtained higher specific discharge capacities compared to calendered and non-calendered blade-casted electrodes due to superior microstructural properties. Such a fast and industrially compelling integrative DFSP/lamination tool could be a prosperous, next generation technology for low-cost LIB electrode fabrication.

Method for forming a potential hydrocarbon sensor with low sensitivity to methane and CO

DOEpatents

Mukundan, Rangachary; Brosha, Eric L.; Garzon, Fernando

2003-12-02

A hydrocarbon sensor is formed with an electrolyte body having a first electrolyte surface with a reference electrode depending therefrom and a metal oxide electrode body contained within the electrolyte body and having a first electrode surface coplanar with the first electrolyte surface. The sensor was formed by forming a sintered metal-oxide electrode body and placing the metal-oxide electrode body within an electrolyte powder. The electrolyte powder with the metal-oxide electrode body was pressed to form a pressed electrolyte body containing the metal-oxide electrode body. The electrolyte was removed from an electrolyte surface above the metal-oxide electrode body to expose a metal-oxide electrode surface that is coplanar with the electrolyte surface. The electrolyte body and the metal-oxide electrode body were then sintered to form the hydrocarbon sensor.

Voltametric analysis apparatus and method

DOEpatents

Almon, Amy C.

1993-01-01

An apparatus and method for electrochemical analysis of elements in solution. An auxiliary electrode 14, a reference electrode 18, and five working electrodes 20, 22, 26, 28, and 30 are positioned in a container 12 containing a sample solution 34. The working electrodes are spaced apart evenly from each other and auxiliary electrode 14 to minimize any inter-electrode interference that may occur during analysis. An electric potential is applied between auxiliary electrode 14 and each of the working electrodes 20, 22, 26, 28, and 30. Simultaneous measurements taken of the current flow through each of the working electrodes for each given potential in a potential range are used for identifying chemical elements present in sample solution 34 and their respective concentrations. Multiple working electrodes enable a more positive identification to be made by providing unique data characteristic of chemical elements present in the sample solution.

Electrokinetic In Situ Treatment of Metal-Contaminated Soil

NASA Technical Reports Server (NTRS)

Quinn, Jacqueline; Clausen, Christian A., III; Geiger, Cherie; Reinhart, Debra

2004-01-01

An electrokinetic technique has been developed as a means of in situ remediation of soils, sludges, and sediments that are contaminated with heavy metals. Examples of common metal contaminants that can be removed by this technique include cadmium, chromium, zinc, lead, mercury, and radionuclides. Some organic contaminants can also be removed by this technique. In the electrokinetic technique, a low-intensity direct current is applied between electrodes that have been implanted in the ground on each side of a contaminated soil mass. The electric current causes electro-osmosis and migration of ions, thereby moving aqueous-phase subsurface contaminants from one electrode to the other. The half reaction at the anode yields H+, thereby generating an acid front that travels from the anode toward the cathode. As this acid front passes through a given location, the local increase in acidity increases the solubility of cations that were previously adsorbed on soil particles. Ions are transported towards one electrode or the other which one depending on their respective electric charges. Upon arrival at the electrodes, the ionic contaminants can be allowed to become deposited on the electrodes or can be extracted to a recovery system. Surfactants and other reagents can be introduced at the electrodes to enhance rates of removal of contaminants. Placements of electrodes and concentrations and rates of pumping of reagents can be adjusted to maximize efficiency. The basic concept of electrokinetic treatment of soil is not new. What is new here are some of the details of application and the utilization of this technique as an alternative to other techniques (e.g., flushing or bioremediation) that are not suitable for treating soils of low hydraulic conductivity. Another novel aspect is the use of this technique as a less expensive alternative to excavation: The cost advantage over excavation is especially large in settings in which contaminated soil lies near and/or under industrial buildings and therefore excavation would be made even more expensive by the need to prevent damage to numerous underground pipes and cables.

Advanced Characterization Techniques for Sodium-Ion Battery Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shadike, Zulipiya; Zhao, Enyue; Zhou, Yong-Ning

Sodium (Na)-ion batteries (NIBs) are considered promising alternative candidates to the well-commercialized lithium-ion batteries, especially for applications in large-scale energy storage systems. The electrochemical performance of NIBs such as the cyclability, rate capability, and voltage profiles are strongly dependent on the structural and morphological evolution, phase transformation, sodium-ion diffusion, and electrode/electrolyte interface reconstruction during charge–discharge cycling. Therefore, in-depth understanding of the structure and kinetics of electrode materials and the electrode/electrolyte interfaces is essential for optimizing current NIB systems and exploring new materials for NIBs. Recently, rapid progress and development in spectroscopic, microscopic, and scattering techniques have provided extensive insight intomore » the nature of structural evolution, morphological changes of electrode materials, and electrode/electrolyte interface in NIBs. Here in this review, a comprehensive overview of both static (ex situ) and real-time (in situ or in operando) techniques for studying the NIBs is provided. Lastly, special focus is placed on how these techniques are applied to the fundamental investigation of NIB systems and what important results are obtained.« less

Advanced Characterization Techniques for Sodium-Ion Battery Studies

DOE PAGES

Shadike, Zulipiya; Zhao, Enyue; Zhou, Yong-Ning; ...

2018-02-19

Sodium (Na)-ion batteries (NIBs) are considered promising alternative candidates to the well-commercialized lithium-ion batteries, especially for applications in large-scale energy storage systems. The electrochemical performance of NIBs such as the cyclability, rate capability, and voltage profiles are strongly dependent on the structural and morphological evolution, phase transformation, sodium-ion diffusion, and electrode/electrolyte interface reconstruction during charge–discharge cycling. Therefore, in-depth understanding of the structure and kinetics of electrode materials and the electrode/electrolyte interfaces is essential for optimizing current NIB systems and exploring new materials for NIBs. Recently, rapid progress and development in spectroscopic, microscopic, and scattering techniques have provided extensive insight intomore » the nature of structural evolution, morphological changes of electrode materials, and electrode/electrolyte interface in NIBs. Here in this review, a comprehensive overview of both static (ex situ) and real-time (in situ or in operando) techniques for studying the NIBs is provided. Lastly, special focus is placed on how these techniques are applied to the fundamental investigation of NIB systems and what important results are obtained.« less

Comparisons of Force Measurement Methods for DBD Plasma Actuators in Quiescent Air

NASA Technical Reports Server (NTRS)

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2009-01-01

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators with cylindrical exposed electrodes, as the electrode diameter decrease the force efficiencies increase much faster than a previously reported linear trend. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. Actuators with rectangular cross-section exposed electrodes do not show the same rapid increase at small thicknesses. We have also shown that the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Automatic control and detector for three-terminal resistance measurement

DOEpatents

Fasching, George E.

1976-10-26

A device is provided for automatic control and detection in a three-terminal resistance measuring instrument. The invention is useful for the rapid measurement of the resistivity of various bulk material with a three-terminal electrode system. The device maintains the current through the sample at a fixed level while measuring the voltage across the sample to detect the sample resistance. The three-electrode system contacts the bulk material and the current through the sample is held constant by means of a control circuit connected to a first of the three electrodes and works in conjunction with a feedback controlled amplifier to null the voltage between the first electrode and a second electrode connected to the controlled amplifier output. An A.C. oscillator provides a source of sinusoidal reference voltage of the frequency at which the measurement is to be executed. Synchronous reference pulses for synchronous detectors in the control circuit and an output detector circuit are provided by a synchronous pulse generator. The output of the controlled amplifier circuit is sampled by an output detector circuit to develop at an output terminal thereof a D.C. voltage which is proportional to the sample resistance R. The sample resistance is that segment of the sample between the area of the first electrode and the third electrode, which is connected to ground potential.

Fabrication and characterization of microfabricated on-chip microelectrochemical cell for biosensing applications

NASA Astrophysics Data System (ADS)

Said, N. A. Mohd; Twomey, K.; Herzog, G.; Ogurtsov, V. I.

2017-03-01

The fabrication of on-chip microelectrochemical cell on Si wafer by means of photolithography is described here. The single on-chip microelectrochemical cell device has dimensions of 100 × 380 mm with integrated Pt counter electrode (CE), Ag/AgCl reference electrode (RE) and gold microelectrode array of 500 nm recess depth as the working electrode (WE). Two geometries of electrode array were implemented, band and disc, with fixed diameter/width of 10 µm; and varied centre-to-centre spacing (d) and number of electrodes (N) in the array. The on-chip microelectrochemical cell structure has been designed to facilitate further WE biomodifications. Firstly, the developed microelectrochemical cell does not require packaging hence reducing the production cost and time. Secondly, the working electrode (WE) on the microelectrochemical cell is positioned towards the end of the chip enabling modification of the working electrode surface to be carried out for surface bio-functionalisation without affecting both the RE and CE surface conditions. The developed on-chip microelectrochemical cell was examined with scanning electron microscopy (SEM) and characterised by two electrochemical techniques. Both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed in 1 mM ferrocenecarboxylic acid (FCA) in 0.01 M phosphate buffered saline (PBS) solution at pH7.4. Electrochemical experiments showed that in the case of halving the interspacing distance of the microdisc WE array (50 nm instead of 100 nm), the voltammogram shifted from a steady-state CV (feature of hemispherical diffusion) to an inclined peak-shaped CV (feature of linear diffusion) albeit the arrays had the same surface area. In terms of EIS it was also found that linear diffusion dominates the surface instead of hemispherical diffusion once the interspacing distance was reduced, supporting the fact that closely packed arrays may behave like a macroelectrode

Insulated ECG electrodes

NASA Technical Reports Server (NTRS)

Portnoy, W. M.; David, R. M.

1973-01-01

Insulated, capacitively coupled electrode does not require electrolyte paste for attachment. Other features of electrode include wide range of nontoxic material that may be employed for dielectric because of sputtering technique used. Also, electrode size is reduced because there is no need for external compensating networks with FET operational amplifier.

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

NASA Astrophysics Data System (ADS)

Sarathi, R.; Giridhar, A. V.; Sethupathi, K.

2011-02-01

The UHF signals are generated due to PD formed by particle movement in liquid nitrogen under AC voltages. The levitation voltage of a particle in liquid nitrogen measured through UHF technique and by conventional PD measurement technique is the same, confirming the sensitivity of UHF technique for identification of PD activity. The frequency content of UHF signal generated due to particle movement in liquid nitrogen, under AC voltages, lies in the range 0.5-1.5 GHz. The characteristics of UHF signal generated due to particle movement between the barrier and high voltage/ground electrode is much similar to the signal generated by particle movement in clean electrode gap. Pseudo resonance phenomena can occur in liquid nitrogen due to particle movement. It is also observed that the partial discharge magnitude, in general, be high when the particle moves between the barrier and high voltage electrode when compared to the barrier and the ground electrode. Percentage of clay in epoxy nanocomposites has not altered the levitation voltage of the particle in the electrode gap. Zero span analysis clearly indicates that pseudo resonance occurs when particle moves (in a short gap) between the barrier and high voltage/ground electrode.

High resolution micro-CT scanning as an innovative tool for evaluation of the surgical positioning of cochlear implant electrodes.

PubMed

Postnov, A; Zarowski, A; De Clerck, N; Vanpoucke, F; Offeciers, F E; Van Dyck, D; Peeters, S

2006-05-01

X-ray microtomography (micro-CT) is a new technique allowing for visualization of the internal structure of opaque specimens with a quasi-histological quality. Among multiple potential applications, the use of this technique in otology is very promising. Micro-CT appears to be ideally suited for in vitro visualization of the inner ear tissues as well as for evaluation of the electrode damage and/or surgical insertion trauma during implantation of the cochlear implant electrodes. This technique can greatly aid in design and development of new cochlear implant electrodes and is applicable for temporal bone studies. The main advantage of micro-CT is the practically artefact-free preparation of the samples and the possibility of evaluation of the interesting parameters along the whole insertion depth of the electrode. This paper presents the results of the first application of micro-CT for visualization of the inner ear structures in human temporal bones and for evaluation of the surgical positioning of the cochlear implant electrodes relative to the intracochlear soft tissues.

A new venous infusion pathway monitoring system.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2007-01-01

A new infusion catheter pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer has been developed for hospital and home use. The sensor consists of coaxial three-layer conductive tapes wrapped around the polyvinyl chloride infusion tube. The inner tape is the main electrode, which records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The outside tape layer is a reference electrode to monitor the AC voltage around the main electrode. The center tape layer is connected to system ground and functions as a shield. The microcomputer calculates the ratio of the induced AC voltages recorded by the main and reference electrodes and if the ratio indicates a detached infusion, alerts the nursing station, via the nurse call system or low transmitting power mobile phone.

Development of an Electrochemical Immunosensor for Fumonisins Detection in Foods

PubMed Central

Kadir, Mohamad Kamal Abdul; Tothill, Ibtisam E.

2010-01-01

An electrochemical affinity sensor for the determination of fumonisins mycotoxins (Fms) using monoclonal antibody modified screen-printed gold electrode with carbon counter and silver-silver chloride pseudo-reference electrode is reported in this work. A direct competitive enzyme-linked immunosorbent assay (ELISA) was initially developed, exhibiting a detection limit of 100 µg·L-1 for fumonisins. This was then transferred to the surface of a bare gold screen-printed electrode (SPGE) and detection was performed by chronoamperometry, monitoring the reaction of 3,3’,5,5’-Tetramethylbenzidine dihydrochloride (TMB) and hydrogen peroxide (H2O2) catalysed by HRP at −100 mV potential vs. onboard Ag-AgCl pseudo-reference electrode. The immunosensor exhibited detection limit of 5 µg·L−1 fumonisins with a dynamic range from 1 µg·L−1–1000 µg·L−1. The sensor also performed well in extracted corn samples. PMID:22069591

An all-solid-state reference electrode based on the layer-by-layer polymer coating.

PubMed

Kwon, Nak-Hyun; Lee, Kyung-Sun; Won, Mi-Sook; Shim, Yoon-Bo

2007-09-01

A solid-state reference electrode (SSRE) was fabricated by layering a silicone rubber (SR) film containing KCl on an AgCl surface, then a perfluorinated ionomer film, and finally a polyurethane-based membrane containing an ionophore, a lipophilic ionic additive, and a plasticizer, respectively. The addition of SiCl4 to the polyurethane-based membrane layer enhanced the strength of the membrane in an aqueous solution. The morphologies of the membranes were studied separately by SEM. The fabrication of the Ag/AgCl electrode through this layer-by-layer polymer coating improved the electrode stability enormously. In addition, the potential drift of the SSRE according to the pH of the medium was minimized by introducing a H+-ion-selective ionophore (tridodecylamine; TDDA) into the outmost polymer membrane. The cyclic voltammetric and potentiometric responses using the SSRE and a conventional reference electrode, respectively, were consistent. The SSRE exhibited little potential variation even in the case of the addition of very high concentrations of various salts, such as Na salicylate, LiCl, KCl, CaCl2, MgCl2, KNO3, NaCl, and NaHCO3. The practicability of the proposed SSRE was tested for the determination of blood pH and pCO2 in a flow cell system. The SSRE fabricated in the present study was stable over two years.

Finite difference time domain (FDTD) modeling of implanted deep brain stimulation electrodes and brain tissue.

PubMed

Gabran, S R I; Saad, J H; Salama, M M A; Mansour, R R

2009-01-01

This paper demonstrates the electromagnetic modeling and simulation of an implanted Medtronic deep brain stimulation (DBS) electrode using finite difference time domain (FDTD). The model is developed using Empire XCcel and represents the electrode surrounded with brain tissue assuming homogenous and isotropic medium. The model is created to study the parameters influencing the electric field distribution within the tissue in order to provide reference and benchmarking data for DBS and intra-cortical electrode development.

Fully solution-processing route toward highly transparent polymer solar cells.

PubMed

Guo, Fei; Kubis, Peter; Stubhan, Tobias; Li, Ning; Baran, Derya; Przybilla, Thomas; Spiecker, Erdmann; Forberich, Karen; Brabec, Christoph J

2014-10-22

We report highly transparent polymer solar cells using metallic silver nanowires (AgNWs) as both the electron- and hole-collecting electrodes. The entire stack of the devices is processed from solution using a doctor blading technique. A thin layer of zinc oxide nanoparticles is introduced between photoactive layer and top AgNW electrode which plays decisive roles in device functionality: it serves as a mechanical foundation which allows the solution-deposition of top AgNWs, and more importantly it facilitates charge carriers extraction due to the better energy level alignment and the formation of ohmic contacts between the active layer/ZnO and ZnO/AgNWs. The resulting semitransparent polymer:fullerene solar cells showed a power conversion efficiency of 2.9%, which is 72% of the efficiency of an opaque reference device. Moreover, an average transmittance of 41% in the wavelength range of 400-800 nm is achieved, which is of particular interest for applications in transparent architectures.

Effect of slightly acid pH with or without chloride in radioactive water on the corrosion of maraging steel

NASA Astrophysics Data System (ADS)

Bellanger, G.; Rameau, J. J.

1996-02-01

This study was carried out to ascertain the behavior of maraging steel used in the tanks of French plants for reprocessing radioactive water which may contain chloride ions at pH 3. The rest or corrosion potentials can be either in the transpassive or active regions due to the presence of radiolytic species. The corrosion current and potential depend on the pH and intermediates formed on the surface in the active region; therefore, maraging steel behavior was studied by cyclic voltammetry without and with electrode rotation and different acid pH which provide an indication of mechanisms, modification of local pH and transient formation. In the passive -transpassive region, breakdown and porosity in the oxide appear with or without chloride, according to electrochemical impedance spectroscopy. In presence of chloride, the corrosion kinetics were obtained by cyclic voltammetry and electrochemical impedance spectroscopy. The anodic and cathodic areas of maraging steel corroded by pitting were shown using the Scanning Reference Electrode Technique.

Electroreduction of CO{sub 2} using copper-deposited on boron-doped diamond (BDD)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panglipur, Hanum Sekar; Ivandini, Tribidasari A., E-mail: ivandini.tri@sci.ui.ac.id; Einaga, Yasuaki

Electroreduction of CO{sub 2} was studied at copper-modified boron-doped diamond (Cu-BDD) electrodes as the working electrode. The Cu-BDD electrodes were prepared by electrochemical reduction with various concentrations of CuSO{sub 4} solutions. FE-SEM was utilized to characterize the electrodes. At Cu-BDD electrodes, a reduction peak at around -1.2 V (vs Ag/AgCl) attributtable to CO{sub 2} reductions could be observed by cyclic voltammetry technique of CO{sub 2} bubbled in water containing 0.1M NaCl. Accordingly, electroreduction of CO{sub 2} was conducted at -1.2 V (vs Ag/AgCl) using amperometry technique. The chemical products of the electroreduction analyzed by using HPLC showed the formation of formaldehyde, formicmore » acid, and acetic acid at Cu-BDD electrodes.« less

X-ray Absorption Spectroscopy Characterization of Electrochemical Processes in Renewable Energy Storage and Conversion Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmand, Maryam

2013-05-19

The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. X-ray absorption spectroscopymore » (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the and #916; and mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The and #916; and mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the and #916; and mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.« less

Fabrication of Graphene on Kevlar Supercapacitor Electrodes

DTIC Science & Technology

2011-05-01

fabricated with graphene to investigate its applicability for energy storage devices, as this carbon- based material has a large surface area and...Distribution List 14 iv List of Figures Figure 1. Dip-and-dry technique applied to Kevlar- based electrodes...2  Figure 2. Three-electrode system used for the CV measurements. The (1) working electrode was the Kevlar- based electrode; (2) the counter

Electro-osmotic infusion for joule heating soil remediation techniques

DOEpatents

Carrigan, Charles R.; Nitao, John J.

1999-01-01

Electro-osmotic infusion of ground water or chemically tailored electrolyte is used to enhance, maintain, or recondition electrical conductivity for the joule heating remediation technique. Induced flows can be used to infuse electrolyte with enhanced ionic conductivity into the vicinity of the electrodes, maintain the local saturation of near-electrode regions and resaturate a partially dried out zone with groundwater. Electro-osmotic infusion can also tailor the conductivity throughout the target layer by infusing chemically modified and/or heated electrolyte to improve conductivity contrast of the interior. Periodic polarity reversals will prevent large pH changes at the electrodes. Electro-osmotic infusion can be used to condition the electrical conductivity of the soil, particularly low permeability soil, before and during the heating operation. Electro-osmotic infusion is carried out by locating one or more electrodes adjacent the heating electrodes and applying a dc potential between two or more electrodes. Depending on the polarities of the electrodes, the induced flow will be toward the heating electrodes or away from the heating electrodes. In addition, electrodes carrying a dc potential may be located throughout the target area to tailor the conductivity of the target area.

High-resolution electrical mapping of porcine gastric slow-wave propagation from the mucosal surface.

PubMed

Angeli, T R; Du, P; Paskaranandavadivel, N; Sathar, S; Hall, A; Asirvatham, S J; Farrugia, G; Windsor, J A; Cheng, L K; O'Grady, G

2017-05-01

Gastric motility is coordinated by bioelectrical slow waves, and gastric dysrhythmias are reported in motility disorders. High-resolution (HR) mapping has advanced the accurate assessment of gastric dysrhythmias, offering promise as a diagnostic technique. However, HR mapping has been restricted to invasive surgical serosal access. This study investigates the feasibility of HR mapping from the gastric mucosal surface. Experiments were conducted in vivo in 14 weaner pigs. Reference serosal recordings were performed with flexible-printed-circuit (FPC) arrays (128-192 electrodes). Mucosal recordings were performed by two methods: (i) FPC array aligned directly opposite the serosal array, and (ii) cardiac mapping catheter modified for gastric mucosal recordings. Slow-wave propagation and morphology characteristics were quantified and compared between simultaneous serosal and mucosal recordings. Slow-wave activity was consistently recorded from the mucosal surface from both electrode arrays. Mucosally recorded slow-wave propagation was consistent with reference serosal activation pattern, frequency (P≥.3), and velocity (P≥.4). However, mucosally recorded slow-wave morphology exhibited reduced amplitude (65-72% reduced, P<.001) and wider downstroke width (18-31% wider, P≤.02), compared to serosal data. Dysrhythmias were successfully mapped and classified from the mucosal surface, accorded with serosal data, and were consistent with known dysrhythmic mechanisms in the porcine model. High-resolution gastric electrical mapping was achieved from the mucosal surface, and demonstrated consistent propagation characteristics with serosal data. However, mucosal signal morphology was attenuated, demonstrating necessity for optimized electrode designs and analytical algorithms. This study demonstrates feasibility of endoscopic HR mapping, providing a foundation for advancement of minimally invasive spatiotemporal gastric mapping as a clinical and scientific tool. © 2016 John Wiley & Sons Ltd.

Hyperthermia with implanted electrodes: in vitro and in vivo correlations.

PubMed

Lilly, M B; Brezovich, I A; Atkinson, W; Chakraborty, D; Durant, J R; Ingram, J; McElvein, R B

1983-03-01

Hyperthermia as a treatment for cancer has elicited much recent interest. However, major difficulties persist both in the technology for heating deep-seated tumors, and in thermal dosimetry. We have investigated a heating technique for deep-seated neoplasms that employs an internal implanted electrode and an external electrode to apply radiofrequency current to a tumor mass. The internal electrode consists of an array of stainless steel needles or wires which define a Faraday cage within the tumor, while the external electrode consists of a variety of electrical conductors at the skin surface. Phantom measurements have closely reproduced calculated temperature distributions. The temperature profiles within the volume enclosed by the internal electrode show relatively homogenous heating. Temperature measurements in a rat tumor model have demonstrated that significant heating within such an internal electrode array is easily obtained. The heating may extend some centimeters outside the electrode. Using a dog model we have shown that with such a treatment technique the temperature profiles obtained are reproducible both spatially and temporally. A case report of a clinical application is presented. A 5 cm bronchogenic carcinoma was easily heated without significant heating of the surrounding normal lung, and without apparent toxicity. Such a technique may be applicable to a variety of operable but unresectable neoplasms. The reproducibility and relative homogeneity of heating suggest possible usefulness in combined modality trials.

Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air

NASA Technical Reports Server (NTRS)

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2008-01-01

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

A Manually Operated, Advance Off-Stylet Insertion Tool for Minimally Invasive Cochlear Implantation Surgery

PubMed Central

Kratchman, Louis B.; Schurzig, Daniel; McRackan, Theodore R.; Balachandran, Ramya; Noble, Jack H.; Webster, Robert J.; Labadie, Robert F.

2014-01-01

The current technique for cochlear implantation (CI) surgery requires a mastoidectomy to gain access to the cochlea for electrode array insertion. It has been shown that microstereotactic frames can enable an image-guided, minimally invasive approach to CI surgery called percutaneous cochlear implantation (PCI) that uses a single drill hole for electrode array insertion, avoiding a more invasive mastoidectomy. Current clinical methods for electrode array insertion are not compatible with PCI surgery because they require a mastoidectomy to access the cochlea; thus, we have developed a manually operated electrode array insertion tool that can be deployed through a PCI drill hole. The tool can be adjusted using a preoperative CT scan for accurate execution of the advance off-stylet (AOS) insertion technique and requires less skill to operate than is currently required to implant electrode arrays. We performed three cadaver insertion experiments using the AOS technique and determined that all insertions were successful using CT and microdissection. PMID:22851233

Evaluation of electrochemical, UV/VIS and Raman spectroelectrochemical detection of Naratriptan with screen-printed electrodes.

PubMed

Hernández, Carla Navarro; Martín-Yerga, Daniel; González-García, María Begoña; Hernández-Santos, David; Fanjul-Bolado, Pablo

2018-02-01

Naratriptan, active pharmaceutical ingredient with antimigraine activity was electrochemically detected in untreated screen-printed carbon electrodes (SPCEs). Cyclic voltammetry and differential pulse voltammetry were used to carry out quantitative analysis of this molecule (in a Britton-Robinson buffer solution at pH 3.0) through its irreversible oxidation (diffusion controlled) at a potential of +0.75V (vs. Ag pseudoreference electrode). Naratriptan oxidation product is an indole based dimer with a yellowish colour (maximum absorption at 320nm) so UV-VIS spectroelectrochemistry technique was used for the very first time as an in situ characterization and quantification technique for this molecule. A reflection configuration approach allowed its measurement over the untreated carbon based electrode. Finally, time resolved Raman Spectroelectrochemistry is used as a powerful technique to carry out qualitative and quantitative analysis of Naratriptan. Electrochemically treated silver screen-printed electrodes are shown as easy to use and cost-effective SERS substrates for the analysis of Naratriptan. Copyright © 2017 Elsevier B.V. All rights reserved.

Membrane Bioprobe Electrodes

ERIC Educational Resources Information Center

Rechnitz, Garry A.

1975-01-01

Describes the design of ion selective electrodes coupled with immobilized enzymes which operate either continuously or on drop-sized samples. Cites techniques for urea, L-phenylalanine and amygdalin. Micro size electrodes for use in single cells are discussed. (GH)

Design, Fabrication and Characterization of an In Silico Cell Physiology lab for Bio Sensing Applications

NASA Astrophysics Data System (ADS)

Haque, A. ul; Rokkam, M.; DeCarlo, A. R.; Wereley, S. T.; Wells, H. W.; McLamb, W. T.; Roux, S. J.; Irazoqui, P. P.; Porterfield, D. M.

2006-04-01

In this paper, we report the design, fabrication and characterization of an In Silico cell physiology biochip for measuring Ca2+ ion concentrations and currents around single cells. This device has been designed around specific science objectives of measuring real time multidimensional calcium flux patterns around sixteen Ceratopteris richardii fern spores in microgravity flight experiments and ground studies. The sixteen microfluidic cell holding pores are 150 by 150 µm each and have 4 Ag/AgCl electrodes leading into them. An SU-8 structural layer is used for insulation and packaging purposes. The In Silico cell physiology lab is wire bonded on to a custom PCB for easy interface with a state of the art data acquisition system. The electrodes are coated with a Ca2+ ion selective membrane based on ETH-5234 ionophore and operated against an Ag/AgCl reference electrode. Initial characterization results have shown Nernst slopes of 30mv/decade that were stable over a number of measurement cycles. While this work is focused on technology to enable basic research on the Ceratopteris richardii spores, we anticipate that this type of cell physiology lab-on-a-chip will be broadly applied in biomedical and pharmacological research by making minor modifications to the electrode material and the measurement technique. Future applications include detection of glucose, hormones such as plant auxin, as well as multiple analyte detection on the same chip.

High voltage performance of a dc photoemission electron gun with centrifugal barrel-polished electrodes

NASA Astrophysics Data System (ADS)

Hernandez-Garcia, C.; Bullard, D.; Hannon, F.; Wang, Y.; Poelker, M.

2017-09-01

The design and fabrication of electrodes for direct current (dc) high voltage photoemission electron guns can significantly influence their performance, most notably in terms of maximum achievable bias voltage. Proper electrostatic design of the triple-point junction shield electrode minimizes the risk of electrical breakdown (arcing) along the insulator-cable plug interface, while the electrode shape is designed to maintain <10 MV/m at the desired operating voltage aiming at little or no field emission once conditioned. Typical electrode surface preparation involves diamond-paste polishing by skilled personnel, requiring several weeks of effort per electrode. In this work, we describe a centrifugal barrel-polishing technique commonly used for polishing the interior surface of superconducting radio frequency cavities but implemented here for the first time to polish electrodes for dc high voltage photoguns. The technique reduced polishing time from weeks to hours while providing surface roughness comparable to that obtained with diamond-paste polishing and with unprecedented consistency between different electrode samples. We present electrode design considerations and high voltage conditioning results to 360 kV (˜11 MV/m), comparing barrel-polished electrode performance to that of diamond-paste polished electrodes. Tests were performed using a dc high voltage photogun with an inverted-geometry ceramic insulator design.

Ion-selective electrodes in organic elemental and functional group analysis: a review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selig, W.

1977-11-08

The literature on the use of ion-selective electrodes in organic elemental and functional group analysis is surveyed in some detail. The survey is complete through Chemical Abstracts, Vol. 83 (1975). 40 figures, 52 tables, 236 references.

Comparison of three‐dimensional analysis and stereological techniques for quantifying lithium‐ion battery electrode microstructures

PubMed Central

TAIWO, OLUWADAMILOLA O.; FINEGAN, DONAL P.; EASTWOOD, DAVID S.; FIFE, JULIE L.; BROWN, LEON D.; DARR, JAWWAD A.; LEE, PETER D.; BRETT, DANIEL J.L.

2016-01-01

Summary Lithium‐ion battery performance is intrinsically linked to electrode microstructure. Quantitative measurement of key structural parameters of lithium‐ion battery electrode microstructures will enable optimization as well as motivate systematic numerical studies for the improvement of battery performance. With the rapid development of 3‐D imaging techniques, quantitative assessment of 3‐D microstructures from 2‐D image sections by stereological methods appears outmoded; however, in spite of the proliferation of tomographic imaging techniques, it remains significantly easier to obtain two‐dimensional (2‐D) data sets. In this study, stereological prediction and three‐dimensional (3‐D) analysis techniques for quantitative assessment of key geometric parameters for characterizing battery electrode microstructures are examined and compared. Lithium‐ion battery electrodes were imaged using synchrotron‐based X‐ray tomographic microscopy. For each electrode sample investigated, stereological analysis was performed on reconstructed 2‐D image sections generated from tomographic imaging, whereas direct 3‐D analysis was performed on reconstructed image volumes. The analysis showed that geometric parameter estimation using 2‐D image sections is bound to be associated with ambiguity and that volume‐based 3‐D characterization of nonconvex, irregular and interconnected particles can be used to more accurately quantify spatially‐dependent parameters, such as tortuosity and pore‐phase connectivity. PMID:26999804

Comparison of three-dimensional analysis and stereological techniques for quantifying lithium-ion battery electrode microstructures.

PubMed

Taiwo, Oluwadamilola O; Finegan, Donal P; Eastwood, David S; Fife, Julie L; Brown, Leon D; Darr, Jawwad A; Lee, Peter D; Brett, Daniel J L; Shearing, Paul R

2016-09-01

Lithium-ion battery performance is intrinsically linked to electrode microstructure. Quantitative measurement of key structural parameters of lithium-ion battery electrode microstructures will enable optimization as well as motivate systematic numerical studies for the improvement of battery performance. With the rapid development of 3-D imaging techniques, quantitative assessment of 3-D microstructures from 2-D image sections by stereological methods appears outmoded; however, in spite of the proliferation of tomographic imaging techniques, it remains significantly easier to obtain two-dimensional (2-D) data sets. In this study, stereological prediction and three-dimensional (3-D) analysis techniques for quantitative assessment of key geometric parameters for characterizing battery electrode microstructures are examined and compared. Lithium-ion battery electrodes were imaged using synchrotron-based X-ray tomographic microscopy. For each electrode sample investigated, stereological analysis was performed on reconstructed 2-D image sections generated from tomographic imaging, whereas direct 3-D analysis was performed on reconstructed image volumes. The analysis showed that geometric parameter estimation using 2-D image sections is bound to be associated with ambiguity and that volume-based 3-D characterization of nonconvex, irregular and interconnected particles can be used to more accurately quantify spatially-dependent parameters, such as tortuosity and pore-phase connectivity. © 2016 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

Microfabricated Patch Clamp Electrodes for Improved Ion Channel Protein Measurements

NASA Astrophysics Data System (ADS)

Klemic, James; Klemic, Kathryn; Reed, Mark; Sigworth, Frederick

2002-03-01

Ion channels are trans-membrane proteins that underlie many cell functions including hormone and neurotransmitter release, muscle contraction and cell signaling cascades. Ion channel proteins are commonly characterized via the patch clamp method in which an extruded glass tube containing ionic solution, manipulated by an expert technician, is brought into contact with a living cell to record ionic current through the cell membrane. Microfabricated planar patch electrodes, micromolded in the silicone elastomer poly-dimethylsiloxane (PDMS) from microlithographically patterned structures, have been developed that improve on this method. Microfabrication techniques allow arrays of patch electrodes to be fabricated, increasing the throughput of the measurement technique. Planar patch electrodes readily allow the automation of cell sealing, further increasing throughput. Microfabricated electrode arrays may be readily integrated with microfluidic structures to allow fast, in situ solution exchange. Miniaturization of the electrode geometry should increase both the signal to noise and the bandwidth of the measurement. Microfabricated patch electrode arrays have been fabricated and measurements have been taken.

Robust tracking of a virtual electrode on a coronary sinus catheter for atrial fibrillation ablation procedures

NASA Astrophysics Data System (ADS)

Wu, Wen; Chen, Terrence; Strobel, Norbert; Comaniciu, Dorin

2012-02-01

Catheter tracking in X-ray fluoroscopic images has become more important in interventional applications for atrial fibrillation (AF) ablation procedures. It provides real-time guidance for the physicians and can be used as reference for motion compensation applications. In this paper, we propose a novel approach to track a virtual electrode (VE), which is a non-existing electrode on the coronary sinus (CS) catheter at a more proximal location than any real electrodes. Successful tracking of the VE can provide more accurate motion information than tracking of real electrodes. To achieve VE tracking, we first model the CS catheter as a set of electrodes which are detected by our previously published learning-based approach.1 The tracked electrodes are then used to generate the hypotheses for tracking the VE. Model-based hypotheses are fused and evaluated by a Bayesian framework. Evaluation has been conducted on a database of clinical AF ablation data including challenging scenarios such as low signal-to-noise ratio (SNR), occlusion and nonrigid deformation. Our approach obtains 0.54mm median error and 90% of evaluated data have errors less than 1.67mm. The speed of our tracking algorithm reaches 6 frames-per-second on most data. Our study on motion compensation shows that using the VE as reference provides a good point to detect non-physiological catheter motion during the AF ablation procedures.2

ELECTROCHEMICAL TECHNIQUE FOR TNT USING DISPOSABLE SCREEN-PRINTED ELECTRODE

EPA Science Inventory

Screen-printed thick film electrodes are demonstrated as voltammetric sensors for measurement of 2,4,6-trinitrotoluene (TNT). The square wave voltammetric (SWV) scan technique is used to measure TNT in as little as 50 uL sample volumes. This electrochemical assay is coupled ...

Postmortem diffusion MRI of the human brainstem and thalamus for deep brain stimulator electrode localization.

PubMed

Calabrese, Evan; Hickey, Patrick; Hulette, Christine; Zhang, Jingxian; Parente, Beth; Lad, Shivanand P; Johnson, G Allan

2015-08-01

Deep brain stimulation (DBS) is an established surgical therapy for medically refractory tremor disorders including essential tremor (ET) and is currently under investigation for use in a variety of other neurologic and psychiatric disorders. There is growing evidence that the anti-tremor effects of DBS for ET are directly related to modulation of the dentatorubrothalamic tract (DRT), a white matter pathway that connects the cerebellum, red nucleus, and ventral intermediate nucleus of the thalamus. Emerging white matter targets for DBS, like the DRT, will require improved three-dimensional (3D) reference maps of deep brain anatomy and structural connectivity for accurate electrode targeting. High-resolution diffusion MRI of postmortem brain specimens can provide detailed volumetric images of important deep brain nuclei and 3D reconstructions of white matter pathways with probabilistic tractography techniques. We present a high spatial and angular resolution diffusion MRI template of the postmortem human brainstem and thalamus with 3D reconstructions of the nuclei and white matter tracts involved in ET circuitry. We demonstrate registration of these data to in vivo, clinical images from patients receiving DBS therapy, and correlate electrode proximity to tractography of the DRT with improvement of ET symptoms. © 2015 Wiley Periodicals, Inc.

Environmental factors affecting corrosion of munitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bundy, K.; Bricka, M.; Morales, A.

1995-12-31

Spent small arms munitions have accumulated for years at outdoor firing ranges operated by the DoD and other groups. Used bullets are often subjected to moisture sources. There is increasing concern that accumulations of lead-based munitions represent potential sources of water and soil pollution. To understand both the severity of and solutions to this problem, it is necessary to measure how rapidly bullets corrode and to determine the soil variables affecting the process. In this study M16 bullets were buried in samples of soil taken from Louisiana army firing ranges. Four environmental conditions were simulated; rain water, acid rain, seamore » water, and 50% sea water/50% acid rain. The three electrode technique was used to measure the bullet corrosion. Graphite rods served as counter electrodes. A saturated calomel reference electrode was used along with a specially constructed salt bridge. Electrochemical measurements were conducted using a computer-controlled potentiostat to determine corrosion potential, soil resistance, and corrosion current. The rate of corrosion was found to markedly increase with decreasing soil pH and increasing chloride and moisture contents, with the chloride content being the most influential variable. High soil resistance and noble corrosion potential were found to be associated with low corrosion rates. This is important since both parameters can be readily measured in the field.« less

Optimization of method for zinc analysis in several bee products on renewable mercury film silver based electrode.

PubMed

Opoka, Włodzimierz; Szlósarczyk, Marek; Maślanka, Anna; Piech, Robert; Baś, Bogusław; Włodarczyk, Edyta; Krzek, Jan

2013-01-01

Zinc is an interesting target for detection as it is one of the elements necessary for the proper functioning of the human body, its excess and deficiency can cause several symptoms. Several techniques including electrochemistry have been developed but require laboratory equipment, preparative steps and mercury or complex working electrodes. We here described the development of a robust, simple and commercially available electrochemical system. Differential pulse (DP) voltammetry was used for this purpose with the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) and 0.05 M KNO3 solution as a supporting electrolyte. The effect of various factors such as: preconcentration potential and time, pulse amplitude and width, step potential and supporting electrolyte composition are optimized. The limits of detection (LOD) and quantification (LOQ) were 1.62 ng/mL and 4.85 ng/mL, respectively. The repeatability of the method at a concentration level of the analyte as low as 3 ng/mL, expressed as RSD is 3.5% (n = 6). Recovery was determined using certified reference material: Virginia Tobacco Leaves (CTA-VTL-2). The recovery of zinc ranged from 96.6 to 106.5%. The proposed method was successfully applied for determination of zinc in bee products (honey, propolis and diet supplements) after digestion procedure.

A study on photoelectrochemical properties of ZnO@ZnS nanostructures synthesized via facile ion-exchange approach

NASA Astrophysics Data System (ADS)

Sharma, Akash; Sahoo, Pooja; Thangavel, R.

2018-05-01

In this work, ZnO nanorods (NRs) were fabricated, on cleaned ITO substrates by using sol-gel spin coating followed by hydrothermal technique. In order to coat zinc sulphide (ZnS) layers on the earlier prepared NRs a facile ion-exchange approach was adopted. The ZnO@ZnS nanostructures so prepared were characterised by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-visible spectroscopy and photoelectrochemical study. XRD spectra confirmed the hexagonal wurtzite structure of all the samples along with preferential c-axis orientation. Further it was also observed from the FESEM images that sulfidation process doesn't affect the structure of ZnO NRs arrays. From the absorption spectra it can be clearly observed that the light absorbing property has increased in within the visible range due to the formation of ZnS layer on the ZnO nanostructures, which is not possible for either of the material individually. The cyclic voltammetry results indicates the enhancement in photocurrent density after illumination for the synthesized nanostructures. The electrocatalytic behaviour of ZnO@ZnS electrodes have been studied using a 3-electrode system in presence of 0.1M NaOH electrolyte solution with respect to an Ag/AgCl reference electrode.

Technique for the comparison of light spectra from natural and laboratory generated lightning current arcs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchard, D., E-mail: mitcharddr@cardiff.ac.uk; Clark, D.; Carr, D.

A technique was developed for the comparison of observed emission spectra from lightning current arcs generated through self-breakdown in air and the use of two types of initiation wire, aluminum bronze and nichrome, against previously published spectra of natural lightning events. A spectrograph system was used in which the wavelength of light emitted by the lightning arc was analyzed to derive elemental interactions. A lightning impulse of up to 100 kA was applied to a two hemispherical tungsten electrode configuration which allowed the effect of the lightning current and lightning arc length to be investigated. A natural lightning reference spectrum wasmore » reconstructed from literature, and generated lightning spectra were obtained from self-breakdown across a 14.0 mm air gap and triggered along initiation wires of length up to 72.4 mm. A comparison of the spectra showed that the generated lightning arc induced via self-breakdown produced a very similar spectrum to that of natural lightning, with the addition of only a few lines from the tungsten electrodes. A comparison of the results from the aluminum bronze initiation wire showed several more lines, whereas results from the nichrome initiation wire differed greatly across large parts of the spectrum. This work highlights the potential use for spectrographic techniques in the study of lightning interactions with surrounding media and materials, and in natural phenomena such as recently observed ball lightning.« less

Improving resistivity survey resolution at sites with limited spatial extent using buried electrode arrays

NASA Astrophysics Data System (ADS)

Kiflu, H.; Kruse, S.; Loke, M. H.; Wilkinson, P. B.; Harro, D.

2016-12-01

Electrical resistivity tomography (ERT) surveys are widely used in geological, environmental and engineering studies. However, the effectiveness of surface ERT surveys is limited by decreasing resolution with depth and near the ends of the survey line. Increasing the array length will increase depth of investigation, but may not be possible at urban sites where access is limited. One novel method of addressing these limitations while maintaining lateral coverage is to install an array of deep electrodes. Referred to here as the Multi-Electrode Resistivity Implant Technique (MERIT), self-driving pointed electrodes are implanted at depth below each surface electrode in an array, using direct-push technology. Optimal sequences of readings have been identified with the "Compare R" method of Wilkinson. Numerical, laboratory, and field case studies are applied to examine the effectiveness of the MERIT method, particularly for use in covered karst terrain. In the field case studies, resistivity images are compared against subsurface structure defined from borings, GPR surveys, and knowledge of prior land use. In karst terrain where limestone has a clay overburden, traditional surface resistivity methods suffer from lack of current penetration through the shallow clay layer. In these settings, the MERIT method is found to improve resolution of features between the surface and buried array, as well as increasing depth of penetration and enhancing imaging capabilities at the array ends. The method functions similar to a cross-borehole array between horizontal boreholes, and suffers from limitations common to borehole arrays. Inversion artifacts are common at depths close to the buried array, and because some readings involve high geometric factors, inversions are more susceptible to noise than traditional surface arrays. Results are improved by using errors from reciprocal measurements to weight the data during the inversion.

A Comparative Study of Different EEG Reference Choices for Diagnosing Unipolar Depression.

PubMed

Mumtaz, Wajid; Malik, Aamir Saeed

2018-06-02

The choice of an electroencephalogram (EEG) reference has fundamental importance and could be critical during clinical decision-making because an impure EEG reference could falsify the clinical measurements and subsequent inferences. In this research, the suitability of three EEG references was compared while classifying depressed and healthy brains using a machine-learning (ML)-based validation method. In this research, the EEG data of 30 unipolar depressed subjects and 30 age-matched healthy controls were recorded. The EEG data were analyzed in three different EEG references, the link-ear reference (LE), average reference (AR), and reference electrode standardization technique (REST). The EEG-based functional connectivity (FC) was computed. Also, the graph-based measures, such as the distances between nodes, minimum spanning tree, and maximum flow between the nodes for each channel pair, were calculated. An ML scheme provided a mechanism to compare the performances of the extracted features that involved a general framework such as the feature extraction (graph-based theoretic measures), feature selection, classification, and validation. For comparison purposes, the performance metrics such as the classification accuracies, sensitivities, specificities, and F scores were computed. When comparing the three references, the diagnostic accuracy showed better performances during the REST, while the LE and AR showed less discrimination between the two groups. Based on the results, it can be concluded that the choice of appropriate reference is critical during the clinical scenario. The REST reference is recommended for future applications of EEG-based diagnosis of mental illnesses.

Study directed at development of an implantable biotelemetry ion detector

NASA Technical Reports Server (NTRS)

Hanley, L. D.; Kress, D.

1971-01-01

A literature search was conducted to currently update known information in the field of ion-selective electrodes. The review attempts to identify present trends in cation and anions selective electrodes pertinent to the area of bioimplantable units. An electronic circuit was designed to provide the high impedance interface between the ion-selective sensors and signal-processing equipment. The resulting design emphasized the need for low power and miniaturization. Many of the circuits were constructed and used to evaluate the ion-selective electrodes. A cuvette capable of holding the ion-selective and the reference electrodes was designed and constructed. This equipment was used to evaluate commercially available ion-selective electrodes and the electrodes designed and constructed in the study. The results of the electrode tests are included.

Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

NASA Astrophysics Data System (ADS)

Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

2017-09-01

The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

Advantage of four-electrode over two-electrode defibrillators

NASA Astrophysics Data System (ADS)

Bragard, J.; Šimić, A.; Laroze, D.; Elorza, J.

2015-12-01

Defibrillation is the standard clinical treatment used to stop ventricular fibrillation. An electrical device delivers a controlled amount of electrical energy via a pair of electrodes in order to reestablish a normal heart rate. We propose a technique that is a combination of biphasic shocks applied with a four-electrode system rather than the standard two-electrode system. We use a numerical model of a one-dimensional ring of cardiac tissue in order to test and evaluate the benefit of this technique. We compare three different shock protocols, namely a monophasic and two types of biphasic shocks. The results obtained by using a four-electrode system are compared quantitatively with those obtained with the standard two-electrode system. We find that a huge reduction in defibrillation threshold is achieved with the four-electrode system. For the most efficient protocol (asymmetric biphasic), we obtain a reduction in excess of 80% in the energy required for a defibrillation success rate of 90%. The mechanisms of successful defibrillation are also analyzed. This reveals that the advantage of asymmetric biphasic shocks with four electrodes lies in the duration of the cathodal and anodal phase of the shock.

Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms▿ †

PubMed Central

Marsili, Enrico; Rollefson, Janet B.; Baron, Daniel B.; Hozalski, Raymond M.; Bond, Daniel R.

2008-01-01

While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 μm) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes. At low scan rates, cyclic voltammetry revealed catalytic electron transfer between cells and the electrode, similar to what has been observed for pure enzymes attached to electrodes under continuous turnover conditions. Differential pulse voltammetry and electrochemical impedance spectroscopy also revealed features that were consistent with electron transfer being mediated by an adsorbed catalyst. Multiple redox-active species were detected, revealing complexity at the outer surfaces of this bacterium. These techniques provide the basis for cataloging quantifiable, defined electron transfer phenotypes as a function of potential, electrode material, growth phase, and culture conditions and provide a framework for comparisons with other species or communities. PMID:18849456

Metal-coated microfluidic channels: An approach to eliminate streaming potential effects in nano biosensors.

PubMed

Lee, Jieun; Wipf, Mathias; Mu, Luye; Adams, Chris; Hannant, Jennifer; Reed, Mark A

2017-01-15

We report a method to suppress streaming potential using an Ag-coated microfluidic channel on a p-type silicon nanowire (SiNW) array measured by a multiplexed electrical readout. The metal layer sets a constant electrical potential along the microfluidic channel for a given reference electrode voltage regardless of the flow velocity. Without the Ag layer, the magnitude and sign of the surface potential change on the SiNW depends on the flow velocity, width of the microfluidic channel and the device's location inside the microfluidic channel with respect to the reference electrode. Noise analysis of the SiNW array with and without the Ag coating in the fluidic channel shows that noise frequency peaks, resulting from the operation of a piezoelectric micropump, are eliminated using the Ag layer with two reference electrodes located at inlet and outlet. This strategy presents a simple platform to eliminate the streaming potential and can become a powerful tool for nanoscale potentiometric biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of an integrated electrochemical system for in vitro yeast viability testing.

PubMed

Adami, Andrea; Ress, Cristina; Collini, Cristian; Pedrotti, Severino; Lorenzelli, Leandro

2013-02-15

This work describes the development and testing of a microfabricated sensor for rapid cell growth monitoring, especially focused on yeast quality assessment for wine applications. The device consists of a NMOS ISFET sensor with Si(3)N(4) gate, able to indirectly monitor extracellular metabolism through pH variation of the medium, and a solid-state reference electrode implemented with PVC membranes doped with lipophilic salts (tetrabutylammonium-tetrabutylborate (TBA-TBB) and Potassium tetrakis(4-chlorphenyl)borate (KTClpB)). The use of a solid state reference electrode enables the implementation of a large number of cell assays in parallel, without the need of external conventional reference electrodes. Microbial growth testing has been performed both in standard culture conditions and on chip at different concentrations of ethanol in order to carry out a commonly used screening of wine yeast strains. Cell growth tests can be performed in few hours, providing a fast, sensitive and low cost analysis with respect to the conventional procedures. Copyright © 2012 Elsevier B.V. All rights reserved.

Corrosion behavior of HPT-deformed TiNi alloys in cell culture medium

NASA Astrophysics Data System (ADS)

Shri, D. N. Awang; Tsuchiya, K.; Yamamoto, A.

2017-09-01

In recent years there are growing interest in fabrication of bulk nanostructured metals and alloys by using severe plastic deformation (SPD) techniques as new alternative in producing bulk nanocrystalline materials. These techniques allows for processing of bulk, fully dense workpiece with ultrafine grains. Metal undergoes SPD processing in certain techniques such as high pressure torsion (HPT), equal-channel angular pressing (ECAP) or multi-directional forging (MDF) are subjected to extensive hydrostatic pressure that may be used to impart a very high strain to the bulk solid without the introduction of any significant change in overall dimension of the sample. The change in the structure (small grain size and high-volume fraction of grain boundaries) of the material may result in the corrosion behavior different from that of the coarse-grained material. Electrochemical measurements were done to understand the corrosion behavior of TiNi alloys before and after HPT deformation. The experiment was carried out using standard three electrode setup (a sample as working electrode; a platinum wire as a counter electrode and a saturated calomel electrode in saturated KCl as a reference electrode) with the surface area of 26.42 mm2 exposed to the EMEM+10% FBS cell culture medium. The measurements were performed in an incubator with controlled environment at 37 °C and 5% CO2, simulating the cell culture condition. The potential of the specimen was monitored over 1 hour, and the stabilized potential was used as the open-circuit potential (EOCP). Potentiodynamic curves were scanned in the potential range from -0.5 V to 1.5 V relative to the EOCP, at a rate of 0.5 mV/s. The result of OCP-time measurement done in the cell culture medium shows that the OCP of HPT-deformed samples shifts towards to the more positive rather than that of BHPT samples. The OCP of deformed samples were ennobled to more than +70 mV for Ti-50mol%. The shift of OCP towards the nobler direction indicates the passive nature of native oxides formed on the surface of the samples. The polarization curve, on the other hand, indicates that the HPT deformation was found to shift the passive current to nobler region. The passive region current density is found to be lower than that of the BHPT, suggesting the passive film formed on the surface of HPT-deformed samples is more protective than that of the BHPT sample. This study has shown that nanocrystallization and amorphization induced by severe plastic deformation change the corrosion behavior of TiNi alloys.

Robust myoelectric signal detection based on stochastic resonance using multiple-surface-electrode array made of carbon nanotube composite paper

NASA Astrophysics Data System (ADS)

Shirata, Kento; Inden, Yuki; Kasai, Seiya; Oya, Takahide; Hagiwara, Yosuke; Kaeriyama, Shunichi; Nakamura, Hideyuki

2016-04-01

We investigated the robust detection of surface electromyogram (EMG) signals based on the stochastic resonance (SR) phenomenon, in which the response to weak signals is optimized by adding noise, combined with multiple surface electrodes. Flexible carbon nanotube composite paper (CNT-cp) was applied to the surface electrode, which showed good performance that is comparable to that of conventional Ag/AgCl electrodes. The SR-based EMG signal system integrating an 8-Schmitt-trigger network and the multiple-CNT-cp-electrode array successfully detected weak EMG signals even when the subject’s body is in the motion, which was difficult to achieve using the conventional technique. The feasibility of the SR-based EMG detection technique was confirmed by demonstrating its applicability to robot hand control.

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

DOE PAGES

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.; ...

2018-02-09

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Fundamental Investigations of Durability at a Polymer Electrolyte-Electrode Interface

DTIC Science & Technology

2008-04-01

before before σ -σ σ after before before σ -σ σ Cleavage of the side chain ether linkage (Fig. 3), which intrudes into the hydrophilic ionic cluster...directly correlated to peroxide yields measured Figure 3: ATR-FTIR Spectrum of Nafion ®112 (H-form) indicating absorption bands obtained using...electrocatalyst-based fuel cell electrode (referred as sacrificial electrode) directly into the liquid electrolyte, in which oxygen reduction was

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Creating virtual electrodes with 2D current steering

NASA Astrophysics Data System (ADS)

Spencer, Thomas C.; Fallon, James B.; Shivdasani, Mohit N.

2018-06-01

Objective. Current steering techniques have shown promise in retinal prostheses as a way to increase the number of distinct percepts elicitable without increasing the number of implanted electrodes. Previously, it has been shown that ‘virtual’ electrodes can be created between simultaneously stimulated electrode pairs, producing unique cortical response patterns. This study investigated whether virtual electrodes could be created using 2D current steering, and whether these virtual electrodes can produce cortical responses with predictable spatial characteristics. Approach. Normally-sighted eyes of seven adult anaesthetised cats were implanted with a 42-channel electrode array in the suprachoroidal space and multi-unit neural activity was recorded from the visual cortex. Stimuli were delivered to individual physical electrodes, or electrodes grouped into triangular, rectangular, and hexagonal arrangements. Varying proportions of charge were applied to each electrode in a group to ‘steer’ current and create virtual electrodes. The centroids of cortical responses to stimulation of virtual electrodes were compared to those evoked by stimulation of single physical electrodes. Main results. Responses to stimulation of groups of up to six electrodes with equal ratios of charge on each electrode resulted in cortical activation patterns that were similar to those elicited by the central physical electrode (centroids: RM ANOVA on ranks, p  >  0.05 neural spread: one-way ANOVA on Ranks, p  >  0.05). We were also able to steer the centroid of activation towards the direction of any of the electrodes of the group by applying a greater charge to that electrode, but the movement in the centroid was not found to be significant. Significance. The results suggest that current steering is possible in two dimensions between up to at least six electrodes, indicating it may be possible to increase the number of percepts in patients without increasing the number of physical electrodes. Being able to reproduce spatial characteristics of responses to individual physical electrodes suggests that this technique could also be used to compensate for faulty electrodes.

Nanoband array electrode as a platform for high sensitivity enzyme-based glucose biosensing.

PubMed

Falk, Magnus; Sultana, Reshma; Swann, Marcus J; Mount, Andrew R; Freeman, Neville J

2016-12-01

We describe a novel glucose biosensor based on a nanoband array electrode design, manufactured using standard semiconductor processing techniques, and bio-modified with glucose oxidase immobilized at the nanoband electrode surface. The nanoband array architecture allows for efficient diffusion of glucose and oxygen to the electrode, resulting in a thousand-fold improvement in sensitivity and wide linear range compared to a conventional electrode. The electrode constitutes a robust and manufacturable sensing platform. Copyright © 2016 Elsevier B.V. All rights reserved.

A transparent, solvent-free laminated top electrode for perovskite solar cells.

PubMed

Makha, Mohammed; Fernandes, Silvia Letícia; Jenatsch, Sandra; Offermans, Ton; Schleuniger, Jürg; Tisserant, Jean-Nicolas; Véron, Anna C; Hany, Roland

2016-01-01

A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of ~30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes.

A transparent, solvent-free laminated top electrode for perovskite solar cells

NASA Astrophysics Data System (ADS)

Makha, Mohammed; Fernandes, Silvia Letícia; Jenatsch, Sandra; Offermans, Ton; Schleuniger, Jürg; Tisserant, Jean-Nicolas; Véron, Anna C.; Hany, Roland

2016-01-01

A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of 30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes.

Paper-based potentiometric pH sensor using carbon electrode drawn by pencil

NASA Astrophysics Data System (ADS)

Kawahara, Ryotaro; Sahatiya, Parikshit; Badhulika, Sushmee; Uno, Shigeyasu

2018-04-01

A flexible and disposable paper-based pH sensor fabricated with a pencil-drawn working electrode and a Ag/AgCl paste reference electrode is demonstrated for the first time to show pH response by the potentiometric principle. The sensor substrate is made of chromatography paper with a wax-printed hydrophobic area, and various types of carbon pencils are tested as working electrodes. The pH sensitivities of the electrodes drawn by carbon pencils with different hardnesses range from 16.5 to 26.9 mV/pH. The proposed sensor is expected to be more robust against shape change in electrodes on a flexible substrate than other types of chemiresistive/amperometric pH sensors.

Alleviating the Common Confusion Caused by Polarity in Electrochemistry.

ERIC Educational Resources Information Center

Moran, P. J.; Gileadi, E.

1989-01-01

Discussed is some of the confusion encountered in electrochemistry due to misunderstandings of sign conventions and simple mathematical errors. Clarified are issues involving emf series, IUPAC sign conventions, calculation of cell potentials, reference electrodes, the polarity of electrodes in electrochemical devices, and overpotential. (CW)

Characterization of physiochemical properties of polymeric and electrochemical materials for aerospace flight

NASA Technical Reports Server (NTRS)

Rock, M.; Kunigahalli, V.; Khan, S.; Mcnair, A.

1984-01-01

Nickel-cadmium rechargeable batteries are a vital and reliable energy storage source for aerospace applications. As the demand for longer life and more reliable space batteries increases, the understanding and solving of cell aging factors and mechanisms become essential. Over the years, many cell designs and manufacturing process changes have been developed and implemented. Cells fabricated with various design features were life cycled in a simulated low-Earth orbit regime. Following the test program, a comprehensive electrochemical analysis of cell components was undertaken to study cell degradation mechanisms. Discharge voltage degradation or voltage plateau has been observed during orbit cycling, but, its cause and explanation have been the subject of much discussion. A Hg/HgO reference electrode was used to monitor the reference versus each electrode potential during the discharge of a cycled cell. The results indicate that the negative electrode was responsible for the voltage plateau. Cell analysis revealed large crystals of cadmium hydroxide on the surface of the negative electrode and throughout the separator.

The development of sensors and techniques for in situ water quality monitoring

NASA Technical Reports Server (NTRS)

Liu, C. C.

1976-01-01

Enzyme electrodes and chloride ion electrodes were investigated for in situ monitoring of water quality. Preliminary results show that miniature chloride ion electrodes and a phenol sensor are most promising in determining trace contaminants in water.

An EPR and EMF study of Belousov-Zhabotinsky oscillators: Veratric acid and veratraidehyde in a water-acetonitrile medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lalitha, P.V.; Ramaswamy, R.; Ramakrishnan, G.

1992-09-17

Electron paramagnetic resonance and potentiometric techniques using a platinium indicator electrode/ion selective electrode, are used to study Belousov-Zhabotinsky oscillatory reactions involving veratric acid and veratraldehyde as substrates in a mixed medium. These two techniques have yield a good correlation.

A practical guide to using boron doped diamond in electrochemical research.

PubMed

Macpherson, Julie V

2015-02-07

Conducting, boron doped diamond (BDD), in addition to its superior material properties, offers several notable attributes to the electrochemist making it an intriguing material for electrochemical research. These include the widest solvent window of all electrode materials; low background and capacitive currents; reduced fouling compared to other electrodes and; the ability to withstand extreme potentials, corrosive and high temperature/pressure environments. However, BDD is not your typical electrode material, it is a semi-conductor doped degenerately with boron to present semi-metallic characteristics. Input from materials scientists, chemists and physicists has been required to aid understanding of how to work with this material from an electrochemical viewpoint and improve electrode quality. Importantly, depending on how the BDD has been grown and then subsequently treated, prior to electrochemical measurement, the resulting material properties can vary quite significantly from one electrode to the next. This likely explains the variability seen by different researchers working on the same experimental systems. The aim of this "protocols" article is not to provide a state-of-the-art review of diamond electrochemistry, suitable references are provided to the interested reader, but instead serves as a reference point for any researcher wishing to commence work with diamond electrodes and interpret electrochemical data. It provides information on how best to characterise the material properties of the electrode before use and outlines the interplay between boron dopant density, non-diamond-carbon content, grain morphology, surface chemistry and redox couple identity. All should ideally be considered when interpretating electrochemical data arising from the diamond electrode. This will aid the reader in making meaningful comparisons between data obtained by different researchers using different diamond electrodes. The guide also aims to help educate the researcher in choosing which form of BDD is best suited to their research application.

Langmuir Probe Measurements in an Inductively Coupled GEC Reference Cell Plasma

NASA Technical Reports Server (NTRS)

Ji, J. S.; Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

1998-01-01

Measurements of electron number density, electron temperature, and electron energy distribution function (EEDF) using a compensated Langmuir probe have been performed on an inductively (transformer ) coupled Gaseous Electronics Conference (GEC) reference cell plasma. The plasma source is operated with CH4, CF4, or their mixtures with argon. The effect of independently driving the electrode supporting the wafer on the probe data is studied. In particular, we find that the plasma structure depends on the phase in addition to the magnitude of the power coupled to the electrode relative to that of the transformer coil. The Langmuir probe is translated in a plane parallel to the electrode to investigate the spatial structure of the plasma. The probe data is also compared with fluid model predictions.

Analysis of performance losses of direct ethanol fuel cells with the aid of a reference electrode

NASA Astrophysics Data System (ADS)

Li, Guangchun; Pickup, Peter G.

The performances of direct ethanol fuel cells with different anode catalysts, different ethanol concentrations, and at different operating temperatures have been studied. The performance losses of the cell have been separated into individual electrode performance losses with the aid of a reference electrode, ethanol crossover has been quantified, and CO 2 and acetic acid production have been measured by titration. It has been shown that the cell performance strongly depends on the anode catalyst, ethanol concentration, and operating temperature. It was found that the cathode and anode exhibit different dependences on ethanol concentration and operating temperature. The performance of the cathode is very sensitive to the rate of ethanol crossover. Product analysis provides insights into the mechanisms of electro-oxidation of ethanol.

Recording electrocardiograms using 3-limb lead cables instead of the standard 4: a modification to minimize incorrect electrode placements.

PubMed

Soliman, Elsayed Z

2008-01-01

The similarity between and the number of limb lead cables play an important role in the frequency of incorrect connection of limb electrodes. Hence, a modified electrocardiogram (ECG) acquisition procedure is proposed in this brief communication, whereby the left-leg (LL) and right-leg (RL) electrode cables are combined into 1 cable, referred to as combined LL/RL cable. The electrode wires in the combined LL/RL cable are connected to 2 electrodes placed on both sides of the LL. The combined LL/RL cable is unique enough (being thicker) not to be mistaken with the upper limb electrode cables. The proposed modification will not in any way influence the ECG waveforms or amplitudes, and it can be expected to substantially reduce incorrect limb electrode placements.

Capacitive mixing with electrodes of the same kind for energy production from salinity differences

NASA Astrophysics Data System (ADS)

Marino, M.; Kozynchenko, O.; Tennison, S.; Brogioli, D.

2016-03-01

The capacitive mixing technique is aimed at producing renewable energy from salinity differences, for example between sea and river water. The technique makes use of two electrodes that modify their potential in opposite directions when the concentration of the solution in which they are immersed is changed, as a consequence of the dynamics of the electric double layer which forms in the ionic solution. Unfortunately, it is difficult to find two electrodes presenting both optimal performances and opposite potential variations. In order to overcome this problem, we present here a cell scheme with electrodes of the same kind (and thus identical dependence of potential on concentration) which can be operated with a CapMix cycle; it is based on a concentration cell with identical electrodes dipped into two compartments separated by a non-perm-selective porous diaphragm. Thanks to the cyclic operation, the actual cell voltage rise and the power production are close to the values obtained with the traditional scheme, or even higher, depending on the features of the ion transport in the liquid junction region. We present an experimental demonstration of the working principles and we study the power production and energy efficiency in the light of the theory of ion transport in fluids. We show that our technique is competitive with respect to the other CapMix techniques, with the relevant advantage that we make use of only one kind of electrode.

Capacitive mixing with electrodes of the same kind for energy production from salinity differences.

PubMed

Marino, M; Kozynchenko, O; Tennison, S; Brogioli, D

2016-03-23

The capacitive mixing technique is aimed at producing renewable energy from salinity differences, for example between sea and river water. The technique makes use of two electrodes that modify their potential in opposite directions when the concentration of the solution in which they are immersed is changed, as a consequence of the dynamics of the electric double layer which forms in the ionic solution. Unfortunately, it is difficult to find two electrodes presenting both optimal performances and opposite potential variations. In order to overcome this problem, we present here a cell scheme with electrodes of the same kind (and thus identical dependence of potential on concentration) which can be operated with a CapMix cycle; it is based on a concentration cell with identical electrodes dipped into two compartments separated by a non-perm-selective porous diaphragm. Thanks to the cyclic operation, the actual cell voltage rise and the power production are close to the values obtained with the traditional scheme, or even higher, depending on the features of the ion transport in the liquid junction region. We present an experimental demonstration of the working principles and we study the power production and energy efficiency in the light of the theory of ion transport in fluids. We show that our technique is competitive with respect to the other CapMix techniques, with the relevant advantage that we make use of only one kind of electrode.

Nanoscale electrode arrays produced with microscale lithographic techniques for use in biomedical sensing applications.

PubMed

Terry, Jonathan G; Schmüser, Ilka; Underwood, Ian; Corrigan, Damion K; Freeman, Neville J; Bunting, Andrew S; Mount, Andrew R; Walton, Anthony J

2013-12-01

A novel technique for the production of nanoscale electrode arrays that uses standard microfabrication processes and micron-scale photolithography is reported here in detail. These microsquare nanoband edge electrode (MNEE) arrays have been fabricated with highly reproducible control of the key array dimensions, including the size and pitch of the individual elements and, most importantly, the width of the nanoband electrodes. The definition of lateral features to nanoscale dimensions typically requires expensive patterning techniques that are complex and low-throughput. However, the fabrication methodology used here relies on the fact that vertical dimensions (i.e. layer thicknesses) have long been manufacturable at the nanoscale using thin film deposition techniques that are well established in mainstream microelectronics. The authors report for the first time two aspects that highlight the particular suitability of these MNEE array systems for probe monolayer biosensing. The first is simulation, which shows the enhanced sensitivity to the redox reaction of the solution redox couple. The second is the enhancement of probe film functionalisation observed for the probe film model molecule, 6-mercapto-1-hexanol compared with microsquare electrodes. Such surface modification for specific probe layer biosensing and detection is of significance for a wide range of biomedical and other sensing and analytical applications.

Micellar Polymer Encapsulation of Enzymes.

PubMed

Besic, Sabina; Minteer, Shelley D

2017-01-01

Although enzymes are highly efficient and selective catalysts, there have been problems incorporating them into fuel cells. Early enzyme-based fuel cells contained enzymes in solution rather than immobilized on the electrode surface. One problem utilizing an enzyme in solution is an issue of transport associated with long diffusion lengths between the site of bioelectrocatalysis and the electrode. This issue drastically decreases the theoretical overall power output due to the poor electron conductivity. On the other hand, enzymes immobilized at the electrode surface have eliminated the issue of poor electron conduction due to close proximity of electron transfer between electrode and the biocatalyst. Another problem is inefficient and short term stability of catalytic activity within the enzyme that is suspended in free flowing solution. Enzymes in solutions are only stable for hours to days, whereas immobilized enzymes can be stable for weeks to months and now even years. Over the last decade, there has been substantial research on immobilizing enzymes at electrode surfaces for biofuel cell and sensor applications. The most commonly used techniques are sandwich or wired. Sandwich techniques are powerful and successful for enzyme immobilization; however, the enzymes optimal activity is not retained due to the physical distress applied by the polymer limiting its applications as well as the non-uniform distribution of the enzyme and the diffusion of analyte through the polymer is slowed significantly. Wired techniques have shown to extend the lifetime of an enzyme at the electrode surface; however, this technique is very hard to master due to specific covalent bonding of enzyme and polymer which changes the three-dimensional configuration of enzyme and with that decreases the optimal catalytic activity. This chapter details encapsulation techniques where an enzyme will be immobilized within the pores/pockets of the hydrophobically modified micellar polymers such as Nafion ® and chitosan. This strategy has been shown to safely immobilize enzymes at electrode surfaces with storage and continuous operation lifetime of more than 2 years.

Bis(Dioxolene)Bis(Pyridine)Ruthenium Redox Series.

DTIC Science & Technology

1991-08-20

wurking and counter electrodes, and a AgCl/Ag quasi-reference electrode with ferrocene (Fc) as an internal standard. The Fc+/Fc couple was assumed to...assigning the electronic spectra of these species. Similar work has been completed on phosphine substituted species which offer a wider range of

Determination of iodine in bread and fish using the iodide ion-selective electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steiner, J.B.

The purpose of this study was to assess the potential for use of the ion-selective electrode (ISE) as a method for measuring the iodine content in bread and fish. Ashing methods, sample preparation and electrode responses were evaluated. The iodine values obtained using the iodide electrode were compared to iodine values obtained by the arsenic-cerium method (As-Ce). Ashing methods were used in preparing bread and haddock for iodine analysis by the ISE. The values were compared to unashed samples measured by the ISE. Electrode response to iodide was examined by varying the sample pH, measuring electrode equilibrium times, and comparingmore » direct measurement in ppm to iodide values obtained by the method of known addition. Oyster reference tissue with a known iodine concentration was used to determine rates of recovery. For the As-Ce procedure, an alkaline dry ash for two hour followed by colorimetric analysis at 320 nm was recommended. The study showed that the pre-treatment of bread and fish was necessary for ISE measurement. The iodine values obtained by the ISE in the analysis of oyster reference tissue, haddock and bread were not in agreement with their corresponding As-Ce values. Further work needs to be done to determine an ashing procedure that has minimal iodide loss an/or develop sample treatments that will improve the reliability and precision of iodine values obtained using the ion-selective electrode.« less

On the Ageing of High Energy Lithium-Ion Batteries—Comprehensive Electrochemical Diffusivity Studies of Harvested Nickel Manganese Cobalt Electrodes

PubMed Central

Jaguemont, Joris; Van Den Bossche, Peter; Omar, Noshin; Van Mierlo, Joeri

2018-01-01

This paper examines the impact of the characterisation technique considered for the determination of the Li+ solid state diffusion coefficient in uncycled as in cycled Nickel Manganese Cobalt oxide (NMC) electrodes. As major characterisation techniques, Cyclic Voltammetry (CV), Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were systematically investigated. Li+ diffusion coefficients during the lithiation process of the uncycled and cycled electrodes determined by CV at 3.71 V are shown to be equal to 3.48×10−10 cm2·s−1 and 1.56×10−10 cm2·s−1 , respectively. The dependency of the Li+ diffusion with the lithium content in the electrodes is further studied in this paper with GITT and EIS. Diffusion coefficients calculated by GITT and EIS characterisations are shown to be in the range between 1.76×10−15 cm2·s−1 and 4.06×10−12 cm2·s−1, while demonstrating the same decreasing trend with the lithiation process of the electrodes. For both electrode types, diffusion coefficients calculated by CV show greater values compared to those determined by GITT and EIS. With ageing, CV and EIS techniques lead to diffusion coefficients in the electrodes at 3.71 V that are decreasing, in contrast to GITT for which results indicate increasing diffusion coefficient. After long-term cycling, ratios of the diffusion coefficients determined by GITT compared to CV become more significant with an increase about 1 order of magnitude, while no significant variation is seen between the diffusion coefficients calculated from EIS in comparison to CV. PMID:29360787

On the Ageing of High Energy Lithium-Ion Batteries-Comprehensive Electrochemical Diffusivity Studies of Harvested Nickel Manganese Cobalt Electrodes.

PubMed

Capron, Odile; Gopalakrishnan, Rahul; Jaguemont, Joris; Van Den Bossche, Peter; Omar, Noshin; Van Mierlo, Joeri

2018-01-23

This paper examines the impact of the characterisation technique considered for the determination of the L i + solid state diffusion coefficient in uncycled as in cycled Nickel Manganese Cobalt oxide (NMC) electrodes. As major characterisation techniques, Cyclic Voltammetry (CV), Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were systematically investigated. L i + diffusion coefficients during the lithiation process of the uncycled and cycled electrodes determined by CV at 3.71 V are shown to be equal to 3 . 48 × 10 - 10 cm 2 ·s - 1 and 1 . 56 × 10 - 10 cm 2 ·s - 1 , respectively. The dependency of the L i + diffusion with the lithium content in the electrodes is further studied in this paper with GITT and EIS. Diffusion coefficients calculated by GITT and EIS characterisations are shown to be in the range between 1 . 76 × 10 - 15 cm 2 ·s - 1 and 4 . 06 × 10 - 12 cm 2 ·s - 1 , while demonstrating the same decreasing trend with the lithiation process of the electrodes. For both electrode types, diffusion coefficients calculated by CV show greater values compared to those determined by GITT and EIS. With ageing, CV and EIS techniques lead to diffusion coefficients in the electrodes at 3.71 V that are decreasing, in contrast to GITT for which results indicate increasing diffusion coefficient. After long-term cycling, ratios of the diffusion coefficients determined by GITT compared to CV become more significant with an increase about 1 order of magnitude, while no significant variation is seen between the diffusion coefficients calculated from EIS in comparison to CV.

Frameless robot-assisted stereoelectroencephalography in children: technical aspects and comparison with Talairach frame technique.

PubMed

Abel, Taylor J; Varela Osorio, René; Amorim-Leite, Ricardo; Mathieu, Francois; Kahane, Philippe; Minotti, Lorella; Hoffmann, Dominique; Chabardes, Stephan

2018-04-20

OBJECTIVE Robot-assisted stereoelectroencephalography (SEEG) is gaining popularity as a technique for localization of the epileptogenic zone (EZ) in children with pharmacoresistant epilepsy. Here, the authors describe their frameless robot-assisted SEEG technique and report preliminary outcomes and relative complications in children as compared to results with the Talairach frame-based SEEG technique. METHODS The authors retrospectively analyzed the results of 19 robot-assisted SEEG electrode implantations in 17 consecutive children (age < 17 years) with pharmacoresistant epilepsy, and compared these results to 19 preceding SEEG electrode implantations in 18 children who underwent the traditional Talairach frame-based SEEG electrode implantation. The primary end points were seizure-freedom rates, operating time, and complication rates. RESULTS Seventeen children (age < 17 years) underwent a total of 19 robot-assisted SEEG electrode implantations. In total, 265 electrodes were implanted. Twelve children went on to have EZ resection: 4 demonstrated Engel class I outcomes, whereas 2 had Engel class II outcomes, and 6 had Engel class III-IV outcomes. Of the 5 patients who did not have resection, 2 underwent thermocoagulation. One child reported transient paresthesia associated with 2 small subdural hematomas, and 3 other children had minor asymptomatic intracranial hemorrhages. There were no differences in complication rates, rates of resective epilepsy surgery, or seizure freedom rates between this cohort and the preceding 18 children who underwent Talairach frame-based SEEG. The frameless robot-assisted technique was associated with shorter operating time (p < 0.05). CONCLUSIONS Frameless robot-assisted SEEG is a safe and effective means of identifying the EZ in children with pharmacoresistant partial epilepsy. Robot-assisted SEEG is faster than the Talairach frame-based method, and has equivalent safety and efficacy. The former, furthermore, facilitates more electrode trajectory possibilities, which may improve the localization of epileptic networks.

Augmented reality-based electrode guidance system for reliable electroencephalography.

PubMed

Song, Chanho; Jeon, Sangseo; Lee, Seongpung; Ha, Ho-Gun; Kim, Jonghyun; Hong, Jaesung

2018-05-24

In longitudinal electroencephalography (EEG) studies, repeatable electrode positioning is essential for reliable EEG assessment. Conventional methods use anatomical landmarks as fiducial locations for the electrode placement. Since the landmarks are manually identified, the EEG assessment is inevitably unreliable because of individual variations among the subjects and the examiners. To overcome this unreliability, an augmented reality (AR) visualization-based electrode guidance system was proposed. The proposed electrode guidance system is based on AR visualization to replace the manual electrode positioning. After scanning and registration of the facial surface of a subject by an RGB-D camera, the AR of the initial electrode positions as reference positions is overlapped with the current electrode positions in real time. Thus, it can guide the position of the subsequently placed electrodes with high repeatability. The experimental results with the phantom show that the repeatability of the electrode positioning was improved compared to that of the conventional 10-20 positioning system. The proposed AR guidance system improves the electrode positioning performance with a cost-effective system, which uses only RGB-D camera. This system can be used as an alternative to the international 10-20 system.

Pulse-voltammetric glucose detection at gold junction electrodes.

PubMed

Rassaei, Liza; Marken, Frank

2010-09-01

A novel glucose sensing concept based on the localized change or "modulation" in pH within a symmetric gold-gold junction electrode is proposed. A paired gold-gold junction electrode (average gap size ca. 500 nm) is prepared by simultaneous bipotentiostatic electrodeposition of gold onto two closely spaced platinum disk electrodes. For glucose detection in neutral aqueous solution, the potential of the "pH-modulator" electrode is set to -1.5 V vs saturated calomel reference electrode (SCE) to locally increase the pH, and simultaneously, either cyclic voltammetry or square wave voltammetry experiments are conducted at the sensor electrode. A considerable improvement in the sensor electrode response is observed when a normal pulse voltammetry sequence is applied to the modulator electrode (to generate "hydroxide pulses") and the glucose sensor electrode is operated with fixed bias at +0.5 V vs SCE (to eliminate capacitive charging currents). Preliminary data suggest good linearity for the glucose response in the medically relevant 1-10 mM concentration range (corresponding to 0.18-1.8 g L(-1)). Future electroanalytical applications of multidimensional pulse voltammetry in junction electrodes are discussed.

High Pt utilization PEMFC electrode obtained by alternative ion-exchange/electrodeposition.

PubMed

Chen, Siguo; Wei, Zidong; Li, Hua; Li, Li

2010-12-14

High Pt utilization PEMFC electrodes were prepared by an alternative ion-exchange/electrodeposition (AIEE) technique. The results demonstrated that the MEA employing an AIEE electrode with a Pt loading of 0.014 mg Pt cm(-2) exhibits performance approximately 2.2 times larger than that employing a conventional Nafion-bonded Pt/C electrode with a same Pt loading.

Direct electrochemistry of Shewanella loihica PV-4 on gold nanoparticles-modified boron-doped diamond electrodes fabricated by layer-by-layer technique.

PubMed

Wu, Wenguo; Xie, Ronggang; Bai, Linling; Tang, Zuming; Gu, Zhongze

2012-05-01

Microbial Fuel Cells (MFCs) are robust devices capable of taping biological energy, converting pollutants into electricity through renewable biomass. The fabrication of nanostructured electrodes with good bio- and electrochemical activity, play a profound role in promoting power generation of MFCs. Au nanoparticles (AuNPs)-modified Boron-Doped Diamond (BDD) electrodes are fabricated by layer-by-layer (LBL) self-assembly technique and used for the direct electrochemistry of Shewanella loihica PV-4 in an electrochemical cell. Experimental results show that the peak current densities generated on the Au/PAH multilayer-modified BDD electrodes increased from 1.25 to 2.93 microA/cm(-2) as the layer increased from 0 to 6. Different cell morphologies of S. loihica PV-4 were also observed on the electrodes and the highest density of cells was attached on the (Au/PAH)6/BDD electrode with well-formed three-dimensional nanostructure. The electrochemistry of S. loihica PV-4 was enhanced on the (Au/PAH)4/BDD electrode due to the appropriate amount of AuNPsand thickness of PAH layer.

Realization of deep 3D metal electrodes in diamond radiation detectors

NASA Astrophysics Data System (ADS)

Wulz, Thomas; Gerding, William; Lavrik, Nickolay; Briggs, Dayrl; Srijanto, Bernadeta; Lester, Kevin; Hensley, Dale; Spanier, Stefan; Lukosi, Eric

2018-05-01

A fabrication technique to create 3D diamond detectors is presented. Deep reactive ion etching was used to create an array of through-diamond vias (TDVs) in a 2 × 2 × 0.15 mm3 electronic grade single crystal diamond detector. The diameter of the TDVs was nominally 30 μm with a pitch of 100 μm between them. The TDVs were filled with chromium using hexavalent chromium electroplating to create 3D electrodes, which were connected electrically by interdigitated electrodes. The fabricated 3D diamond detector responded to both alpha particles and X-rays, exhibiting a charge collection efficiency of 52.3% at 200 V. Comparing to a diamond detector with the same interdigitated electrodes, but no 3D electrodes, confirms that the 3D electrodes are electrically active within the device. The average resistivity of the 3D electrodes is 2.89 ± 0.03 × 10-5 Ω cm, near that of bulk chromium. These results indicate that this fabrication technique is a potential option for 3D diamond detector fabrication.

CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes.

PubMed

Chervin, Christopher N; Parker, Joseph F; Nelson, Eric S; Rolison, Debra R; Long, Jeffrey W

2016-04-29

The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode-a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte.

Novel LTCC-potentiometric microfluidic device for biparametric analysis of organic compounds carrying plastic antibodies as ionophores: application to sulfamethoxazole and trimethoprim.

PubMed

Almeida, S A A; Arasa, E; Puyol, M; Martinez-Cisneros, C S; Alonso-Chamarro, J; Montenegro, M C B S M; Sales, M G F

2011-12-15

Monitoring organic environmental contaminants is of crucial importance to ensure public health. This requires simple, portable and robust devices to carry out on-site analysis. For this purpose, a low-temperature co-fired ceramics (LTCC) microfluidic potentiometric device (LTCC/μPOT) was developed for the first time for an organic compound: sulfamethoxazole (SMX). Sensory materials relied on newly designed plastic antibodies. Sol-gel, self-assembling monolayer and molecular-imprinting techniques were merged for this purpose. Silica beads were amine-modified and linked to SMX via glutaraldehyde modification. Condensation polymerization was conducted around SMX to fill the vacant spaces. SMX was removed after, leaving behind imprinted sites of complementary shape. The obtained particles were used as ionophores in plasticized PVC membranes. The most suitable membrane composition was selected in steady-state assays. Its suitability to flow analysis was verified in flow-injection studies with regular tubular electrodes. The LTCC/μPOT device integrated a bidimensional mixer, an embedded reference electrode based on Ag/AgCl and an Ag-based contact screen-printed under a micromachined cavity of 600 μm depth. The sensing membranes were deposited over this contact and acted as indicating electrodes. Under optimum conditions, the SMX sensor displayed slopes of about -58.7 mV/decade in a range from 12.7 to 250 μg/mL, providing a detection limit of 3.85 μg/mL and a sampling throughput of 36 samples/h with a reagent consumption of 3.3 mL per sample. The system was adjusted later to multiple analyte detection by including a second potentiometric cell on the LTCC/μPOT device. No additional reference electrode was required. This concept was applied to Trimethoprim (TMP), always administered concomitantly with sulphonamide drugs, and tested in fish-farming waters. The biparametric microanalyzer displayed Nernstian behaviour, with average slopes -54.7 (SMX) and +57.8 (TMP) mV/decade. To demonstrate the microanalyzer capabilities for real applications, it was successfully applied to single and simultaneous determination of SMX and TMP in aquaculture waters. Copyright © 2011 Elsevier B.V. All rights reserved.

Electrochemical Determination of Pentachlorophenol in Water on a Multi-Wall Carbon Nanotubes-Epoxy Composite Electrode

PubMed Central

Remes, Adriana; Pop, Aniela; Manea, Florica; Baciu, Anamaria; Picken, Stephen J.; Schoonman, Joop

2012-01-01

The aim of this study was the preparation, characterization, and application of a multi-wall carbon nanotubes-epoxy composite electrode (MWCNT-EP) with 25%, wt. MWCNTs loading for the voltammetric/amperometric determination of pentachlorophenol (PCP) in aqueous solutions. The structural and morphological aspects of the MWCNT-EP composite electrode were examined by scanning electron microscopy. The electrical properties were characterized by direct-current conductivity measurements in relation with the percolation threshold. The electrochemical behavior of PCP at the MWCNT-EP composite electrode was investigated using cyclic voltammetry in 0.1 M Na2SO4 supporting electrolyte in order to establish the parameters for amperometric/voltammetric determination of PCP. The linear dependence of current vs. PCP concentrations was reached in a wide concentration range from 0.2 to 12 μM PCP using cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry, chronoamperometry, and multiple-pulsed amperometry techniques. The best electroanalytical performances of this composite electrode were achieved using a pre-concentration/square-wave voltammetric technique and also multiple-pulsed amperometry techniques envisaging the practical applications. The ease of preparation, high sensitivity, and stability of this composite electrode should open novel avenues and applications for fabricating robust sensors for detection of many important species. PMID:22969335

Frangible electrochemical cell and sealing technique

NASA Technical Reports Server (NTRS)

Halpert, G.; Haynos, J.; Sherfey, J.

1969-01-01

Electrochemical cell assembly, which includes a positive electrode plate between two negative electrode plates, is both flexible and compact, and frangible under severe shock conditions. Leak-tight integrity of the housing is maintained by polymer-to-polymer fusion bonds through holes in the expanded metal electrode terminals.

The Importance of the Numerical Resolution of the Laplace Equation in the optimization of a Neuronal Stimulation Technique

NASA Astrophysics Data System (ADS)

Faria, Paula

2010-09-01

For the past few years, the potential of transcranial direct current stimulation (tDCS) for the treatment of several pathologies has been investigated. Knowledge of the current density distribution is an important factor in optimizing such applications of tDCS. For this goal, we used the finite element method to solve the Laplace equation in a spherical head model in order to investigate the three dimensional distribution of the current density and the variation of its intensity with depth using different electrodes montages: the traditional one with two sponge electrodes and new electrode montages: with sponge and EEG electrodes and with EEG electrodes varying the numbers of electrodes. The simulation results confirm the effectiveness of the mixed system which may allow the use of tDCS and EEG recording concomitantly and may help to optimize this neuronal stimulation technique. The numerical results were used in a promising application of tDCS in epilepsy.

Dielectric elastomers with novel highly-conducting electrodes

NASA Astrophysics Data System (ADS)

Böse, Holger; Uhl, Detlev

2013-04-01

Beside the characteristics of the elastomer material itself, the performance of dielectric elastomers in actuator, sensor as well as generator applications depends also on the properties of the electrode material. Various electrode materials based on metallic particles dispersed in a silicone matrix were manufactured and investigated. Anisotropic particles such as silver-coated copper flakes and silver-coated glass flakes were used for the preparation of the electrodes. The concentration of the metallic particles and the thickness of the electrode layers were varied. Specific conductivities derived from resistance measurements reached about 100 S/cm and surmount those of the reference materials based on graphite and carbon black by up to three orders of magnitude. The high conductivities of the new electrode materials can be maintained even at very large stretch deformations up to 200 %.

Metal/Metal Oxide Differential Electrode pH Sensors

NASA Technical Reports Server (NTRS)

West, William; Buehler, Martin; Keymeulen, Didier

2007-01-01

Solid-state electrochemical sensors for measuring the degrees of acidity or alkalinity (in terms of pH values) of liquid solutions are being developed. These sensors are intended to supplant older electrochemical pH sensors that include glass electrode structures and reference solutions. The older sensors are fragile and subject to drift. The present developmental solid-state sensors are more rugged and are expected to be usable in harsh environments. The present sensors are based on a differential-electrode measurement principle. Each sensor includes two electrodes, made of different materials, in equilibrium with the solution of interest.

Development of concept for concurrent biocide generation and water system purification. [with application to Skylab water tanks

NASA Technical Reports Server (NTRS)

1974-01-01

An attempt was made to construct an electrochemical system, using iodine, for water purification in Skylab. Data cover measurements of iodine production rates, effect of electrode size and geometry on iodine production rates, and feasibility of using stainless steels as reference electrodes.

Free Radical Damage and Noise-Induced Hearing Loss: in vivo in situ Sensing

DTIC Science & Technology

2008-07-01

e.g. imploding, locally nucleating bubbles23-26 ), leading to cellular damage? While ROS can kill cells, they are also part of the apoptotic cascade...reverse side. Electrodes are gold on Kaptonill substrates. Reference electrodes (Ir/IrxOy) are electrodeposited from IrC13 solution. Working

21 CFR 172.133 - Dimethyl dicarbonate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... titration Reference electrode Glass electrode reagents Acetone, analytical-grade Solution of 1 N... sample (W) and dissolve in 100 mL acetone. Add accurately 25 mL of the 1 N diisobutylamine solution by... the diisobutylamine solution, always use the same pipette and wait for a further three drops to fall...

Magnesia-stabilised zirconia solid electrolyte assisted electrochemical investigation of iron ions in a SiO2-CaO-MgO-Al2O3 molten slag at 1723 K.

PubMed

Gao, Yunming; Yang, Chuanghuang; Zhang, Canlei; Qin, Qingwei; Chen, George Z

2017-06-21

Production of metallic iron through molten oxide electrolysis using inert electrodes is an alternative route for fast ironmaking without CO 2 emissions. The fact that many inorganic oxides melt at ultrahigh temperatures (>1500 K) challenges conventional electro-analytical techniques used in aqueous, organic and molten salt electrolytes. However, in order to design a feasible and effective electrolytic process, it is necessary to best understand the electrochemical properties of iron ions in molten oxide electrolytes. In this work, a magnesia-stabilised zirconia (MSZ) tube with a closed end was used to construct an integrated three-electrode cell with a "MSZ|Pt|O 2 (air)" assembly functioning as the solid electrolyte, the reference electrode and also the counter electrode. Electrochemical reduction of iron ions was systematically investigated on an iridium (Ir) wire working electrode in a SiO 2 -CaO-MgO-Al 2 O 3 molten slag at 1723 K by cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and potentiostatic electrolysis (PE). The results show that the electroreduction of the Fe 2+ ion to Fe on the Ir electrode in the molten slag follows a single two-electron transfer step, and the rate of the process is diffusion controlled. The peak current on the obtained CVs is proportional to the concentration of the Fe 2+ ion in the molten slag and the square root of scan rate. The diffusion coefficient of Fe 2+ ions in the molten slag containing 5 wt% FeO at 1723 K was derived to be (3.43 ± 0.06) × 10 -6 cm 2 s -1 from CP analysis. However, a couple of subsequent processes, i.e. alloy formation on the Ir electrode surface and interdiffusion, were found to affect the kinetics of iron deposition. An ECC mechanism is proposed to account for the CV observations. The findings from this work confirm that zirconia-based solid electrolytes can play an important role in electrochemical fundamental research in high temperature molten slag electrolytes.

Morphology and conductivity of Au films on polydimethylsiloxane using (3-mercaptopropyl)trimethoxysilane (MPTMS) as an adhesion promoter

NASA Astrophysics Data System (ADS)

Osmani, Bekim; Deyhle, Hans; Weiss, Florian M.; Töpper, Tino; Karapetkova, Maria; Leung, Vanessa; Müller, Bert

2016-04-01

Dielectric elastomer actuators (DEA) are often referred to as artificial muscles due to their high specific continuous power, which is comparable to that of human skeletal muscles, and because of their millisecond response time. We intend to use nanometer-thin DEA as medical implant actuators and sensors to be operated at voltages as low as a few tens of volts. The conductivity of the electrode and the impact of its stiffness on the stacked structure are key to the design and operation of future devices. The stiffness of sputtered Au electrodes on polydimethylsiloxane (PDMS) was characterized using AFM nanoindentation techniques. 2500 nanoindentations were performed on 10 x 10 μm2 regions at loads of 100 to 400 nN using a spherical tip with a radius of (522 +/- 2) nm. Stiffness maps based on the Hertz model were calculated using the Nanosurf Flex-ANA system. The low adhesion of Au to PDMS has been reported in the literature and leads to the formation of Au-nanoclusters. The size of the nanoclusters was (25 +/- 10) nm and can be explained by the low surface energy of PDMS leading to a Volmer-Weber growth mode. Therefore, we propose (3-mercaptopropyl)trimethoxysilane (MPTMS) as a molecular adhesive to promote the adhesion between the PDMS and Au electrode. A beneficial side effect of these self-assembling monolayers is the significant improvement of the electrode's conductivity as determined by four-point probe measurements. Therefore, the application of a soft adhesive layer for building a dielectric elastomer actuator appears promising.

Single-Use Disposable Electrochemical Label-Free Immunosensor for Detection of Glycated Hemoglobin (HbA1c) Using Differential Pulse Voltammetry (DPV).

PubMed

Molazemhosseini, Alireza; Magagnin, Luca; Vena, Pasquale; Liu, Chung-Chiun

2016-07-01

A single-use disposable in vitro electrochemical immunosensor for the detection of HbA1c in undiluted human serum using differential pulse voltammetry (DPV) was developed. A three-electrode configuration electrochemical biosensor consisted of 10-nm-thin gold film working and counter electrodes and a thick-film printed Ag/AgCl reference electrode was fabricated on a polyethylene terephthalate (PET) substrate. Micro-fabrication techniques including sputtering vapor deposition and thick-film printing were used to fabricate the biosensor. This was a roll-to-roll cost-effective manufacturing process making the single-use disposable in vitro HbA1c biosensor a reality. Self-assembled monolayers of 3-Mercaptopropionic acid (MPA) were employed to covalently immobilize anti-HbA1c on the surface of gold electrodes. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) confirmed the excellent coverage of MPA-SAM and the upward orientation of carboxylic groups. The hindering effect of HbA1c on the ferricyanide/ferrocyanide electron transfer reaction was exploited as the HbA1c detection mechanism. The biosensor showed a linear range of 7.5-20 µg/mL of HbA1c in 0.1 M PBS. Using undiluted human serum as the test medium, the biosensor presented an excellent linear behavior (R² = 0.999) in the range of 0.1-0.25 mg/mL of HbA1c. The potential application of this biosensor for in vitro measurement of HbA1c for diabetic management was demonstrated.

Single-Use Disposable Electrochemical Label-Free Immunosensor for Detection of Glycated Hemoglobin (HbA1c) Using Differential Pulse Voltammetry (DPV)

PubMed Central

Molazemhosseini, Alireza; Magagnin, Luca; Vena, Pasquale; Liu, Chung-Chiun

2016-01-01

A single-use disposable in vitro electrochemical immunosensor for the detection of HbA1c in undiluted human serum using differential pulse voltammetry (DPV) was developed. A three-electrode configuration electrochemical biosensor consisted of 10-nm-thin gold film working and counter electrodes and a thick-film printed Ag/AgCl reference electrode was fabricated on a polyethylene terephthalate (PET) substrate. Micro-fabrication techniques including sputtering vapor deposition and thick-film printing were used to fabricate the biosensor. This was a roll-to-roll cost-effective manufacturing process making the single-use disposable in vitro HbA1c biosensor a reality. Self-assembled monolayers of 3-Mercaptopropionic acid (MPA) were employed to covalently immobilize anti-HbA1c on the surface of gold electrodes. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) confirmed the excellent coverage of MPA-SAM and the upward orientation of carboxylic groups. The hindering effect of HbA1c on the ferricyanide/ferrocyanide electron transfer reaction was exploited as the HbA1c detection mechanism. The biosensor showed a linear range of 7.5–20 µg/mL of HbA1c in 0.1 M PBS. Using undiluted human serum as the test medium, the biosensor presented an excellent linear behavior (R2 = 0.999) in the range of 0.1–0.25 mg/mL of HbA1c. The potential application of this biosensor for in vitro measurement of HbA1c for diabetic management was demonstrated. PMID:27376299

N-Doped graphene/PEDOT composite films as counter electrodes in DSSCs: Unveiling the mechanism of electrocatalytic activity enhancement

NASA Astrophysics Data System (ADS)

Paterakis, Georgios; Raptis, Dimitrios; Ploumistos, Alexandros; Belekoukia, Meltiani; Sygellou, Lamprini; Ramasamy, Madeshwaran Sekkarapatti; Lianos, Panagiotis; Tasis, Dimitrios

2017-11-01

A composite film was obtained by layer deposition of N-doped graphene and poly(3,4-ethylenedioxythiophene) (PEDOT) and was used as Pt-free counter electrode for dye-sensitized solar cells. N-doping of graphene was achieved by annealing mixtures of graphene oxide with urea. Various parameters concerning the treatment of graphene oxide-urea mixtures were monitored in order to optimize the electrocatalytic activity in the final solar cell device. These include the mass ratio of components, the annealing temperature, the starting concentration of the mixture in aqueous solution and the spinning rate for film formation. PEDOT was applied by electrodeposition. The homogeneity of PEDOT coverage onto either untreated or thermally annealed graphene oxide-urea film was assessed by imaging (AFM/SEM) and surface techniques (XPS). It was found that PEDOT was deposited in the form of island structures onto untreated graphene oxide-urea film. On the contrary, the annealed film was homogeneously covered by the polymer, acquiring morphology of decreased roughness. An apparent chemical interaction between PEDOT and N-doped graphene flakes was revealed by XPS data, involving potential grafting of PEDOT chains onto graphitic lattice through Csbnd C bonding. In addition, diffusion of nitrogen-containing fragments within the PEDOT layer was found to take place during electrodeposition process, resulting in enhanced interfacial interactions between components. The solar cell with the optimized N-doped graphene/PEDOT composite counter electrode exhibited a power conversion efficiency (η) of 7.1%, comparable within experimental error to that obtained by using a reference Pt counter electrode, which showed a value of 7.0%.

Enhanced Monitoring of Nanosecond Electric Pulse-Evoked Membrane Conductance Changes in Whole-Cell Patch Clamp Experiments.

PubMed

Yoon, Jihwan; Leblanc, Normand; Zaklit, Josette; Vernier, P Thomas; Chatterjee, Indira; Craviso, Gale L

2016-10-01

Patch clamp electrophysiology serves as a powerful method for studying changes in plasma membrane ion conductance induced by externally applied high-intensity nanosecond electric pulses (NEPs). This paper describes an enhanced monitoring technique that minimizes the length of time between pulse exposure and data recording in a patch-clamped excitable cell. Whole-cell membrane currents were continuously recorded up to 11 ms before and resumed 8 ms after delivery of a 5-ns, 6 MV/m pulse by a pair of tungsten rod electrodes to a patched adrenal chromaffin cell maintained at a holding potential of -70 mV. This timing was achieved by two sets of relay switches. One set was used to disconnect the patch pipette electrode from the pre-amplifier and connect it to a battery to maintain membrane potential at -70 mV, and also to disconnect the reference electrode from the amplifier. The other set was used to disconnect the electrodes from the pulse generator until the time of NEP/sham exposure. The sequence and timing of both sets of relays were computer-controlled. Using this procedure, we observed that a 5-ns pulse induced an instantaneous inward current that decayed exponentially over the course of several minutes, that a second pulse induced a similar response, and that the current was carried, at least in part, by Na + . This approach for characterizing ion conductance changes in an excitable cell in response to NEPs will yield information essential for assessing the potential use of NEP stimulation for therapeutic applications.

New method for characterizing electron mediators in microbial systems using a thin-layer twin-working electrode cell.

PubMed

Hassan, Md Mahamudul; Cheng, Ka Yu; Ho, Goen; Cord-Ruwisch, Ralf

2017-01-15

Microbial biofilms are significant ecosystems where the existence of redox gradients drive electron transfer often via soluble electron mediators. This study describes the use of two interfacing working electrodes (WEs) to simulate redox gradients within close proximity (250µm) for the detection and quantification of electron mediators. By using a common counter and reference electrode, the potentials of the two WEs were independently controlled to maintain a suitable "voltage window", which enabled simultaneous oxidation and reduction of electron mediators as evidenced by the concurrent anodic and cathodic currents, respectively. To validate the method, the electrochemical properties of different mediators (hexacyanoferrate, HCF, riboflavin, RF) were characterized by stepwise shifting the "voltage window" (ranging between 25 and 200mV) within a range of potentials after steady equilibrium current of both WEs was established. The resulting differences in electrical currents between the two WEs were recorded across a defined potential spectrum (between -1V and +0.5V vs. Ag/AgCl). Results indicated that the technique enabled identification (by the distinct peak locations at the potential scale) and quantification (by the peak of current) of the mediators for individual species as well as in an aqueous mixture. It enabled a precise determination of mid-potentials of the externally added mediators (HCF, RF) and mediators produced by pyocyanin-producing Pseudomonas aeruginosa (WACC 91) culture. The twin working electrode described is particularly suitable for studying mediator-dependent microbial electron transfer processes or simulating redox gradients as they exist in microbial biofilms. Copyright © 2016 Elsevier B.V. All rights reserved.

Nondestructive evaluation of epoxy-coated reinforcing bars in concrete using bi-electrode half-cell potential techniques.

DOT National Transportation Integrated Search

2006-01-01

This study evaluated two half-cell mapping methods for nondestructive evaluation of epoxy-coated rebar (ECR) in concrete: the semi-fixed bi-electrode and the moving bi-electrode methods. These methods were expected to provide early detection of corro...

Complex magnetohydrodynamic low-Reynolds-number flows.

PubMed

Xiang, Yu; Bau, Haim H

2003-07-01

The interaction between electric currents and a magnetic field is used to produce body (Lorentz) forces in electrolyte solutions. By appropriate patterning of the electrodes, one can conveniently control the direction and magnitude of the electric currents and induce spatially and temporally complicated flow patterns. This capability is useful, not only for fundamental flow studies, but also for inducing fluid flow and stirring in minute devices in which the incorporation of moving components may be difficult. This paper focuses on a theoretical and experimental study of magnetohydrodynamic flows in a conduit with a rectangular cross section. The conduit is equipped with individually controlled electrodes uniformly spaced at a pitch L. The electrodes are aligned transversely to the conduit's axis. The entire device is subjected to a uniform magnetic field. The electrodes are divided into two groups A and C in such a way that there is an electrode of group C between any two electrodes of group A. We denote the various A and C electrodes with subscripts, i.e., A(i) and C(i), where i=0,+/-1,+/-2, .... When positive and negative potentials are, respectively, applied to the even and odd numbered A electrodes, opposing electric currents are induced on the right and left hand sides of each A electrode. These currents generate transverse forces that drive cellular convection in the conduit. We refer to the resulting flow pattern as A. When electrodes of group C are activated, a similar flow pattern results, albeit shifted in space. We refer to this flow pattern as C. By alternating periodically between patterns A and C, one induces Lagrangian chaos. Such chaotic advection may be beneficial for stirring fluids, particularly in microfluidic devices. Since the flow patterns A and C are shifted in space, they also provide a mechanism for Lagrangian drift that allows net migration of passive tracers along the conduit's length.

Long life reference electrode

DOEpatents

Yonco, R.M.; Nagy, Z.

1987-07-30

An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservoir and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved. 2 figs.

Long life reference electrode

DOEpatents

Yonco, R.M.; Nagy, Z.

1989-04-04

An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservoir and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved. 2 figs.

Long life reference electrode

DOEpatents

Yonco, Robert M.; Nagy, Zoltan

1989-01-01

An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservior and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved.

Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

DOEpatents

Jankowski, A.F.; Makowiecki, D.M.; Rambach, G.D.; Randich, E.

1998-05-19

The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated. 8 figs.

Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

DOEpatents

Jankowski, Alan F.; Makowiecki, Daniel M.; Rambach, Glenn D.; Randich, Erik

1999-01-01

The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated.

Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

DOEpatents

Jankowski, Alan F.; Makowiecki, Daniel M.; Rambach, Glenn D.; Randich, Erik

1998-01-01

The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated.

Method of fabrication of electrodes and electrolytes

DOEpatents

Jankowski, Alan F.; Morse, Jeffrey D.

2004-01-06

Fuel cell stacks contain an electrolyte layer surrounded on top and bottom by an electrode layer. Porous electrodes are prepared which enable fuel and oxidant to easily flow to the respective electrode-electrolyte interface without the need for high temperatures or pressures to assist the flow. Rigid, inert microspheres in combination with thin-film metal deposition techniques are used to fabricate porous anodes, cathodes, and electrolytes. Microshperes contained in a liquid are randomly dispersed onto a host structure and dried such that the microsperes remain in position. A thin-film deposition technique is subsequently employed to deposit a metal layer onto the microsperes. After such metal layer deposition, the microspheres are removed leaving voids, i.e. pores, in the metal layer, thus forming a porous electrode. Successive repetitions of the fabrication process result in the formation of a continuous fuel cell stack. Such stacks may produce power outputs ranging from about 0.1 Watt to about 50 Watts.

Domestic and Industrial Water Disinfection Using Boron-Doped Diamond Electrodes

NASA Astrophysics Data System (ADS)

Rychen, Philippe; Provent, Christophe; Pupunat, Laurent; Hermant, Nicolas

This chapter first describes main properties and manufacturing process (production using HF-CVD, quality-control measurements, etc.) of diamond electrodes and more specifically boron-doped diamond (BDD) electrodes. Their exceptional properties make such electrodes particularly suited for many disinfection applications as thanks to their wide working potential window and their high anodic potential, they allow generating a mixture of powerful oxidizing species mainly based on active oxygen and peroxides. Such mixture of disinfecting agents is far more efficient than conventional chemical or physical known techniques. Their efficiency was tested against numerous microorganisms and then proved to be greater than conventional methods. All bacteria and viruses tested up to date were inactivated 3-5 times faster with a treatment based on with BDD electrodes and the DiaCellⓇ technology than with other techniques. Several applications, either industrial or private (wellness and home use), are discussed with a focus on the dedicated products and the main technology advantages.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, Garimella R.; Barranger, John P.

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, G. R.; Barranger, J. P.

1986-05-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, Garimella R.; Barranger, John P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, G. R.; Barranger, J. P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Cyclic performance tests of Sn/MWCNT composite lithium ion battery anodes at different temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tocoglu, U., E-mail: utocoglu@sakarya.edu.tr; Cevher, O.; Akbulut, H.

In this study tin-multi walled carbon nanotube (Sn-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25 °C, 35 °C, 50 °C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Tin was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Sn-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry testmore » were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures.« less

The edge transient-current technique (E-TCT) with high energy hadron beam

NASA Astrophysics Data System (ADS)

Gorišek, Andrej; Cindro, Vladimir; Kramberger, Gregor; Mandić, Igor; Mikuž, Marko; Muškinja, Miha; Zavrtanik, Marko

2016-09-01

We propose a novel way to investigate the properties of silicon and CVD diamond detectors for High Energy Physics experiments complementary to the already well-established E-TCT technique using laser beam. In the proposed setup the beam of high energy hadrons (MIPs) is used instead of laser beam. MIPs incident on the detector in the direction parallel to the readout electrode plane and perpendicular to the edge of the detector. Such experiment could prove very useful to study CVD diamond detectors that are almost inaccessible for the E-TCT measurements with laser due to large band-gap as well as to verify and complement the E-TCT measurements of silicon. The method proposed is being tested at CERN in a beam of 120 GeV hadrons using a reference telescope with track resolution at the DUT of few μm. The preliminary results of the measurements are presented.

Determination of mercury in ambient water samples by anodic stripping voltammetry on screen-printed gold electrodes.

PubMed

Bernalte, E; Marín Sánchez, C; Pinilla Gil, E

2011-03-09

The applicability of commercial screen-printed gold electrodes (SPGEs) for the determination of Hg(II) in ambient water samples by square wave anodic stripping voltammetry has been demonstrated. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved mercury in the low ng mL(-1) range (detection limit 1.1 ng mL(-1)), useful for pollution monitoring or screening purposes. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material (recoveries 90.0-110%) and the NCS ZC 76303 Mercury in Water Certified Reference Material (recoveries 82.5-90.6%). Waste water samples from industrial origin and fortified rain water samples were assayed for mercury by the proposed method and by a reference ICP-MS method, with good agreement. Screen printing technology thus opens a useful way for the construction of reliable electrochemical sensors for decentralized or even field Hg(II) testing. Copyright © 2011 Elsevier B.V. All rights reserved.

Linear-sweep voltammetry of a soluble redox couple in a cylindrical electrode

NASA Technical Reports Server (NTRS)

Weidner, John W.

1991-01-01

An approach is described for using the linear sweep voltammetry (LSV) technique to study the kinetics of flooded porous electrodes by assuming a porous electrode as a collection of identical noninterconnected cylindrical pores that are filled with electrolyte. This assumption makes possible to study the behavior of this ideal electrode as that of a single pore. Alternatively, for an electrode of a given pore-size distribution, it is possible to predict the performance of different pore sizes and then combine the performance values.

Wearable Platform for Real-time Monitoring of Sodium in Sweat.

PubMed

McCaul, Margaret; Porter, Adam; Barrett, Ruairi; White, Paddy; Stroiescu, Florien; Wallace, Gordon; Diamond, Dermot

2018-06-19

A fully integrated and wearable platform for harvesting and analysing sweat sodium concentration in real time during exercise has been developed and tested. The platform was largely produced using 3D printing, which greatly simplifies fabrication and operation compared to previous versions generated with traditional production techniques. The 3D printed platform doubles the capacity of the sample storage reservoir to about 1.3 ml, reduces the assembly time and provides simple and precise component alignment and contact of the integrated solid-state ion-selective and reference electrodes with the sorbent material. The sampling flowrate in the device can be controlled by introducing threads to enhance wicking of sweat from the skin, across the electrodes to the storage area. The platform was characterised in the lab and in exercise trials over a period of about 60 minutes continuous monitoring. Sweat sodium concentration was found to rise initially to approximately 17 mM and decline gradually over the period of the trial to about 11-12 mM. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast cholesterol detection using flow injection microfluidic device with functionalized carbon nanotubes based electrochemical sensor.

PubMed

Wisitsoraat, A; Sritongkham, P; Karuwan, C; Phokharatkul, D; Maturos, T; Tuantranont, A

2010-12-15

This work reports a new cholesterol detection scheme using functionalized carbon nanotube (CNT) electrode in a polydimethylsiloxane/glass based flow injection microfluidic chip. CNTs working, silver reference and platinum counter electrode layers were fabricated on the chip by sputtering and low temperature chemical vapor deposition methods. Cholesterol oxidase prepared in polyvinyl alcohol solution was immobilized on CNTs by in-channel flow technique. Cholesterol analysis based on flow injection chronoamperometric measurement was performed in 150-μm-wide and 150-μm-deep microchannels. Fast and sensitive real-time detection was achieved with high throughput of more than 60 samples per hour and small sample volume of 15 μl. The cholesterol sensor had a linear detection range between 50 and 400 mg/dl. In addition, low cross-sensitivities toward glucose, ascorbic acid, acetaminophen and uric acid were confirmed. The proposed system is promising for clinical diagnostics of cholesterol with high speed real-time detection capability, very low sample consumption, high sensitivity, low interference and good stability. Copyright © 2010 Elsevier B.V. All rights reserved.

Machining of AISI D2 Tool Steel with Multiple Hole Electrodes by EDM Process

NASA Astrophysics Data System (ADS)

Prasad Prathipati, R.; Devuri, Venkateswarlu; Cheepu, Muralimohan; Gudimetla, Kondaiah; Uzwal Kiran, R.

2018-03-01

In recent years, with the increasing of technology the demand for machining processes is increasing for the newly developed materials. The conventional machining processes are not adequate to meet the accuracy of the machining of these materials. The non-conventional machining processes of electrical discharge machining is one of the most efficient machining processes is being widely used to machining of high accuracy products of various industries. The optimum selection of process parameters is very important in machining processes as that of an electrical discharge machining as they determine surface quality and dimensional precision of the obtained parts, even though time consumption rate is higher for machining of large dimension features. In this work, D2 high carbon and chromium tool steel has been machined using electrical discharge machining with the multiple hole electrode technique. The D2 steel has several applications such as forming dies, extrusion dies and thread rolling. But the machining of this tool steel is very hard because of it shard alloyed elements of V, Cr and Mo which enhance its strength and wear properties. However, the machining is possible by using electrical discharge machining process and the present study implemented a new technique to reduce the machining time using a multiple hole copper electrode. In this technique, while machining with multiple holes electrode, fin like projections are obtained, which can be removed easily by chipping. Then the finishing is done by using solid electrode. The machining time is reduced to around 50% while using multiple hole electrode technique for electrical discharge machining.

Validation of a technique for accurate fine-wire electrode placement into posterior gluteus medius using real-time ultrasound guidance.

PubMed

Hodges, P W; Kippers, V; Richardson, C A

1997-01-01

Fine-wire electromyography is primarily utilised for the recording of activity of the deep musculature, however, due to the location of these muscles, accurate electrode placement is difficult. Real-time ultrasound imaging (RTUI) of muscle tissue has been used for the guidance of the needle insertion for the placement of electrodes into the muscles of the abdominal wall. The validity of RTUI guidance of needle insertion into the deep muscles has not been determined. A cadaveric study was conducted to evaluate the accuracy with which RTUI can be used to guide fine-wire electrode placement using the posterior fibres of gluteus medius (PGM) as an example. Pilot studies revealed that the ultrasound resolution of cadaveric tissue is markedly reduced making it impossible to directly evaluate the technique, therefore, three studies were conducted. An initial study involved the demarcation of the anatomical boundaries of PGM using RTUI to define a technique based on an anatomical landmark that was consisent with the in vivo RTUI guided needle placement technique. This anatomical landmark was then used as the guide for the cadaveric needle insertion. Once the needle was positioned 0.05 ml of dye was introduced and the specimen dissected. The dye was accurately placed in PGM in 100% of the specimens. Finally, fine-wire electrodes were inserted into the PGM of five volunteers and manoeuvres performed indicating the accuracy of placement. This study supports the use of ultrasound imaging for the accurate guidance of needle insertion for fine-wire and needle EMG electrodes.

2014 NEPP Tasks Update for Ceramic and Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2014-01-01

Presentation describes recent development in research on MnO2, wet, and polymer tantalum capacitors. Low-voltage failures in multilayer ceramic capacitors and techniques to reveal precious metal electrode (PME) and base metal electrode (BME) capacitors with cracks are discussed. A voltage breakdown technique is suggested to select high quality low-voltage BME ceramic capacitors.

CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes

NASA Astrophysics Data System (ADS)

Chervin, Christopher N.; Parker, Joseph F.; Nelson, Eric S.; Rolison, Debra R.; Long, Jeffrey W.

2016-04-01

The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode—a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte.

Oxygen sensor for monitoring gas mixtures containing hydrocarbons

DOEpatents

Ruka, Roswell J.; Basel, Richard A.

1996-01-01

A gas sensor measures O.sub.2 content of a reformable monitored gas containing hydrocarbons H.sub.2 O and/or CO.sub.2, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system.

Oxygen sensor for monitoring gas mixtures containing hydrocarbons

DOEpatents

Ruka, R.J.; Basel, R.A.

1996-03-12

A gas sensor measures O{sub 2} content of a reformable monitored gas containing hydrocarbons, H{sub 2}O and/or CO{sub 2}, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system. 4 figs.

Novel H+-Ion Sensor Based on a Gated Lateral BJT Pair

PubMed Central

Yuan, Heng; Zhang, Jixing; Cao, Chuangui; Zhang, Gangyuan; Zhang, Shaoda

2015-01-01

An H+-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair that can operate without the classical reference electrode is proposed. The device is a special type of ion-sensitive field-effect transistor (ISFET). Classical ISFETs have the advantage of miniaturization, but  they are difficult to fabricate by a single fabrication process because of the bulky and brittle reference electrode materials. Moreover, the reference electrodes need to be separated from the sensor device in some cases. The proposed device is composed of two gated lateral BJT components, one of which had a silicide layer while the other was without the layer. The two components were operated under the metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode, which can be controlled by emitter voltage and base current. Buffer solutions with different pH values were used as the sensing targets to verify the characteristics of the proposed device. Owing to their different sensitivities, both components could simultaneously detect the H+-ion concentration and function as a reference to each other. Per the experimental results, the sensitivity of the proposed device was found to be approximately 0.175 μA/pH. This experiment demonstrates enormous potential to lower the cost of the ISFET-based sensor technology. PMID:26703625

Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

NASA Technical Reports Server (NTRS)

Nawaz, Anuscheh; Lau, Matthew

2011-01-01

The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

Past, present and future of spike sorting techniques

PubMed Central

Rey, Hernan Gonzalo; Pedreira, Carlos; Quian Quiroga, Rodrigo

2015-01-01

Spike sorting is a crucial step to extract information from extracellular recordings. With new recording opportunities provided by the development of new electrodes that allow monitoring hundreds of neurons simultaneously, the scenario for the new generation of algorithms is both exciting and challenging. However, this will require a new approach to the problem and the development of a common reference framework to quickly assess the performance of new algorithms. In this work, we review the basic concepts of spike sorting, including the requirements for different applications, together with the problems faced by presently available algorithms. We conclude by proposing a roadmap stressing the crucial points to be addressed to support the neuroscientific research of the near future. PMID:25931392

Screen-Printed Electrodes Modified with “Green” Metals for Electrochemical Stripping Analysis of Toxic Elements

PubMed Central

Economou, Anastasios

2018-01-01

This work reviews the field of screen-printed electrodes (SPEs) modified with “green” metals for electrochemical stripping analysis of toxic elements. Electrochemical stripping analysis has been established as a useful trace analysis technique offering many advantages compared to competing optical techniques. Although mercury has been the preferred electrode material for stripping analysis, the toxicity of mercury and the associated legal requirements in its use and disposal have prompted research towards the development of “green” metals as alternative electrode materials. When combined with the screen-printing technology, such environment-friendly metals can lead to disposable sensors for trace metal analysis with excellent operational characteristics. This review focuses on SPEs modified with Au, Bi, Sb, and Sn for stripping analysis of toxic elements. Different modification approaches (electroplating, bulk modification, use of metal precursors, microengineering techniques) are considered and representative applications are described. A developing related field, namely biosensing based on stripping analysis of metallic nanoprobe labels, is also briefly mentioned. PMID:29596391

Screen-Printed Electrodes Modified with "Green" Metals for Electrochemical Stripping Analysis of Toxic Elements.

PubMed

Economou, Anastasios

2018-03-29

This work reviews the field of screen-printed electrodes (SPEs) modified with "green" metals for electrochemical stripping analysis of toxic elements. Electrochemical stripping analysis has been established as a useful trace analysis technique offering many advantages compared to competing optical techniques. Although mercury has been the preferred electrode material for stripping analysis, the toxicity of mercury and the associated legal requirements in its use and disposal have prompted research towards the development of "green" metals as alternative electrode materials. When combined with the screen-printing technology, such environment-friendly metals can lead to disposable sensors for trace metal analysis with excellent operational characteristics. This review focuses on SPEs modified with Au, Bi, Sb, and Sn for stripping analysis of toxic elements. Different modification approaches (electroplating, bulk modification, use of metal precursors, microengineering techniques) are considered and representative applications are described. A developing related field, namely biosensing based on stripping analysis of metallic nanoprobe labels, is also briefly mentioned.

Flexible Mixed-Potential-Type (MPT) NO₂ Sensor Based on An Ultra-Thin Ceramic Film.

PubMed

You, Rui; Jing, Gaoshan; Yu, Hongyan; Cui, Tianhong

2017-07-29

A novel flexible mixed-potential-type (MPT) sensor was designed and fabricated for NO₂ detection from 0 to 500 ppm at 200 °C. An ultra-thin Y₂O₃-doped ZrO₂ (YSZ) ceramic film 20 µm thick was sandwiched between a heating electrode and reference/sensing electrodes. The heating electrode was fabricated by a conventional lift-off process, while the porous reference and the sensing electrodes were fabricated by a two-step patterning method using shadow masks. The sensor's sensitivity is achieved as 58.4 mV/decade at the working temperature of 200 °C, as well as a detection limit of 26.7 ppm and small response time of less than 10 s at 200 ppm. Additionally, the flexible MPT sensor demonstrates superior mechanical stability after bending over 50 times due to the mechanical stability of the YSZ ceramic film. This simply structured, but highly reliable flexible MPT NO₂ sensor may lead to wide application in the automobile industry for vehicle emission systems to reduce NO₂ emissions and improve fuel efficiency.

Flexible Mixed-Potential-Type (MPT) NO2 Sensor Based on An Ultra-Thin Ceramic Film

PubMed Central

You, Rui; Jing, Gaoshan; Yu, Hongyan; Cui, Tianhong

2017-01-01

A novel flexible mixed-potential-type (MPT) sensor was designed and fabricated for NO2 detection from 0 to 500 ppm at 200 °C. An ultra-thin Y2O3-doped ZrO2 (YSZ) ceramic film 20 µm thick was sandwiched between a heating electrode and reference/sensing electrodes. The heating electrode was fabricated by a conventional lift-off process, while the porous reference and the sensing electrodes were fabricated by a two-step patterning method using shadow masks. The sensor’s sensitivity is achieved as 58.4 mV/decade at the working temperature of 200 °C, as well as a detection limit of 26.7 ppm and small response time of less than 10 s at 200 ppm. Additionally, the flexible MPT sensor demonstrates superior mechanical stability after bending over 50 times due to the mechanical stability of the YSZ ceramic film. This simply structured, but highly reliable flexible MPT NO2 sensor may lead to wide application in the automobile industry for vehicle emission systems to reduce NO2 emissions and improve fuel efficiency. PMID:28758933

Carbon deposition behaviour in metal-infiltrated gadolinia doped ceria electrodes for simulated biogas upgrading in solid oxide electrolysis cells

NASA Astrophysics Data System (ADS)

Duboviks, V.; Lomberg, M.; Maher, R. C.; Cohen, L. F.; Brandon, N. P.; Offer, G. J.

2015-10-01

One of the attractive applications for reversible Solid Oxide Cells (SOCs) is to convert CO2 into CO via high temperature electrolysis, which is particularly important for biogas upgrading. To improve biogas utility, the CO2 component can be converted into fuel via electrolysis. A significant issue for SOC operation on biogas is carbon-induced catalyst deactivation. Nickel is widely used in SOC electrodes for reasons of cost and performance, but it has a low tolerance to carbon deposition. Two different modes of carbon formation on Ni-based electrodes are proposed in the present work based on ex-situ Raman measurements which are in agreement with previous studies. While copper is known to be resistant towards carbon formation, two significant issues have prevented its application in SOC electrodes - namely its relatively low melting temperature, inhibiting high temperature sintering, and low catalytic activity for hydrogen oxidation. In this study, the electrodes were prepared through a low temperature metal infiltration technique. Since the metal infiltration technique avoids high sintering temperatures, Cu-Ce0.9Gd0.1O2-δ (Cu-CGO) electrodes were fabricated and tested as an alternative to Ni-CGO electrodes. We demonstrate that the performance of Cu-CGO electrodes is equivalent to Ni-CGO electrodes, whilst carbon formation is fully suppressed when operated on biogas mixture.

Electro-hydrodynamic force field and flow patterns generated by a DC corona discharge in the air

NASA Astrophysics Data System (ADS)

Monrolin, Nicolas; Plouraboue, Franck; Praud, Olivier

2016-11-01

Ionic wind refers to the electro-convection of ionised air between high voltage electrodes. Microscopic ion-neutral collisions are responsible for momentum transfer from accelerated ions, subjected to the electric field, to the neutral gas molecules resulting in a macroscopic airflow acceleration. In the past decades it has been investigated for various purposes from food drying through aerodynamic flow control and eventually laptop cooling. One consequence of air acceleration between the electrodes is thrust generation, often referred to as the Biefeld-Brown effect or electro-hydrodynamic thrust. In this experimental study, the ionic wind velocity field is measured with the PIV method. From computing the acceleration of the air we work out the electrostatic force field for various electrodes configurations. This enables an original direct evaluation of the force distribution as well as the influence of electrodes shape and position. Thrust computation based on the flow acceleration are compared with digital scale measurements. Complex flow features are highlighted such as vortex shedding, indicating that aerodynamic effects may play a significant role. Furthermore, the aerodynamic drag force exerted on the electrodes is quantified by choosing an appropriate control volume. Authors thank Region Midi-Pyrenee and CNES Launcher Directorate for financial support.

Method of making a layered composite electrode/electrolyte

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2005-01-25

An electrode/electrolyte structure is prepared by a plurality of methods. An unsintered (possibly bisque fired) moderately catalytic electronically-conductive or homogeneous mixed ionic electronic conductive electrode material is deposited on a layer composed of a sintered or unsintered ionically-conductive electrolyte material prior to being sintered. A layer of particulate electrode material is deposited on an unsintered ("green") layer of electrolyte material and the electrode and electrolyte layers are sintered simultaneously, sometimes referred to as "co-firing," under conditions suitable to fully densify the electrolyte while the electrode retains porosity. Or, the layer of particulate electrode material is deposited on a previously sintered layer of electrolyte, and then sintered. Subsequently, a catalytic material is added to the electrode structure by infiltration of an electrolcatalyst precursor (e.g., a metal salt such as a transition metal nitrate). This may be followed by low temperature firing to convert the precursor to catalyst. The invention allows for an electrode with high electronic conductivity and sufficient catalytic activity to achieve high power density in an ionic (electrochemical) device such as fuel cells and electrolytic gas separation systems.

Facile synthesis of nitrogen-doped reduced graphene oxide as an efficient counter electrode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Liguo; Wang, Ping; Yang, Yulin; Luo, Ruidong; Li, Jinqi; Gu, Xiaohu; Zhan, Zhaoshun; Dong, Yongli; Song, Weina; Fan, Ruiqing

2018-04-01

A nitrogen-doped reduced graphene oxide (N-RGO) nanosheet was synthesized by a simple hydrothermal method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electrode microscopy. After being deposited as counter electrode film for dye-sensitized solar cells (DSSCs), it is found that the synthesized N-RGO nanosheet has smaller charge-transfer resistance and better electrocatalytic activity towards reduction of triiodide than the reduced graphene oxide (RGO) nanosheet. Consequently, the DSSCs based on the N-RGO counter electrode achieve an energy conversion efficiency of 4.26%, which is higher than that of the RGO counter electrode (2.85%) prepared under the same conditions, and comparable to the value (5.21%) obtained with the Pt counter electrode as a reference. This N-RGO counter electrode offers the advantages of not only saving the cost of Pt itself but also simplifying the process of counter electrode preparation. Therefore, an inexpensive N-RGO nanosheet is a promising counter electrode material to replace noble metal Pt. [Figure not available: see fulltext.

A Gas-Sensor-Based Urea Enzyme Electrode: Its Construction and Use in the Undergraduate Laboratory.

ERIC Educational Resources Information Center

Riechel, Thomas L.

1984-01-01

Describes an undergraduate experiment for the potentiometric determination of urea based on the physical entrapment of urease on the tip of an ammonia gas sensor. An advantage of this technique is the ease with which the ammonia electrode can be converted to a urea electrode. (JN)

Reversibly immobilized biological materials in monolayer films on electrodes

DOEpatents

Weaver, P.F.; Frank, A.J.

1993-05-04

Methods and techniques are described for reversibly binding charged biological particles in a fluid medium to an electrode surface. The methods are useful in a variety of applications. The biological materials may include microbes, proteins, and viruses. The electrode surface may consist of reversibly electroactive materials such as polyvinylferrocene, silicon-linked ferrocene or quinone.

Reversibly immobilized biological materials in monolayer films on electrodes

DOEpatents

Weaver, Paul F.; Frank, Arthur J.

1993-01-01

Methods and techniques are described for reversibly binding charged biological particles in a fluid medium to an electrode surface. The methods are useful in a variety of applications. The biological materials may include microbes, proteins, and viruses. The electrode surface may consist of reversibly electroactive materials such as polyvinylferrocene, silicon-linked ferrocene or quinone.

Prototype for Automatable, Dielectrophoretically-Accessed Intracellular Membrane–Potential Measurements by Metal Electrodes

PubMed Central

Sukhorukov, Vladimir L.; Zimmermann, Dirk

2013-01-01

Abstract Functional access to membrane proteins, for example, ion channels, of individual cells is an important prerequisite in drug discovery studies. The highly sophisticated patch-clamp method is widely used for electrogenic membrane proteins, but is demanding for the operator, and its automation remains challenging. The dielectrophoretically-accessed, intracellular membrane–potential measurement (DAIMM) method is a new technique showing high potential for automation of electrophysiological data recording in the whole-cell configuration. A cell suspension is brought between a mm-scaled planar electrode and a μm-scaled tip electrode, placed opposite to each other. Due to the asymmetric electrode configuration, the application of alternating electric fields (1–5 MHz) provokes a dielectrophoretic force acting on the target cell. As a consequence, the cell is accelerated and pierced by the tip electrode, hence functioning as the internal (working) electrode. We used the light-gated cation channel Channelrhodopsin-2 as a reporter protein expressed in HEK293 cells to characterize the DAIMM method in comparison with the patch-clamp technique. PMID:22994967

Electrochemically active biofilms: facts and fiction. A review

PubMed Central

Babauta, Jerome; Renslow, Ryan; Lewandowski, Zbigniew; Beyenal, Haluk

2014-01-01

This review examines the electrochemical techniques used to study extracellular electron transfer in the electrochemically active biofilms that are used in microbial fuel cells and other bioelectrochemical systems. Electrochemically active biofilms are defined as biofilms that exchange electrons with conductive surfaces: electrodes. Following the electrochemical conventions, and recognizing that electrodes can be considered reactants in these bioelectrochemical processes, biofilms that deliver electrons to the biofilm electrode are called anodic, ie electrode-reducing, biofilms, while biofilms that accept electrons from the biofilm electrode are called cathodic, ie electrode-oxidizing, biofilms. How to grow these electrochemically active biofilms in bioelec-trochemical systems is discussed and also the critical choices made in the experimental setup that affect the experimental results. The reactor configurations used in bioelectrochemical systems research are also described and the authors demonstrate how to use selected voltammetric techniques to study extracellular electron transfer in bioelectrochemical systems. Finally, some critical concerns with the proposed electron transfer mechanisms in bioelectrochemical systems are addressed together with the prospects of bioelectrochemical systems as energy-converting and energy-harvesting devices. PMID:22856464

Chromophore Poling in Thin Films of Organic Glasses. 2. Two-Electrode Corona Discharge Setup

NASA Astrophysics Data System (ADS)

Vilitis, O.; Muzikante, I.; Rutkis, M.; Vembris, A.

2012-01-01

In Part 1 of the article we provided description of the corona discharge physics and overview of the methods used for corona poling in thin organic films. Subsequent sections describe comparatively simple technical methods for poling the organic nonlinear optical polymers using a two-electrode (point-to-plate or wire-to-plate) technique. The polarization build-up was studied by the DC positive corona method for poling the nonlinear optical (NLO) polymers. The experimental setup provides the corona discharge current from 0.5 μA up to 3 μA by applying 3 kV - 12 kV voltage to the corona electrode and makes possible selection among the types of corona electrodes (needle, multi-needle, wire, etc.). The results of experimental testing of the poling setup show that at fixed optimal operational parameters of poling - the sample orientation temperature and the discharge current - the corona charging of polymeric materials can successfully be performed applying the two-electrode technique. To study the dynamics of both poling and charge transport processes the three-electrode charging system - a corona triode - should be applied.

Microcurrent therapeutic technique for treatment of radiation toxicity

DOEpatents

Lennox, Arlene; Funder, Sandra

2000-01-01

The present technique provides a method of remediating the toxicities associated with radiation therapy. A conductive gel is applied to the affected bodily area. A sinusoidally pulsed biphasic DC current is then applied to the affected bodily area using at least one electrode. The electrode is manipulated using active tactile manipulation by for a predetermined time and the frequency of the sinusoidally pulsed biphasic DC current is decreased during the course of the treatment. The method also includes applying a spiked pulsed biphasic DC current to the affected bodily area using at least one electrode. This electrode is also manipulated using active tactile manipulation by for a predetermined time and the frequency of the spiked pulsed biphasic DC current is also decreased during the course of the treatment.

Investigation of subdural electrode displacement in invasive epilepsy surgery workup using neuronavigation and intraoperative MRI.

PubMed

Sommer, Bjoern; Rampp, Stefan; Doerfler, Arnd; Stefan, Hermann; Hamer, Hajo M; Buchfelder, Michael; Roessler, Karl

2018-06-19

One of the main obstacles of electrode implantation in epilepsy surgery is the electrode shift between implantation and the day of explantation. We evaluated this possible electrode displacement using intraoperative MRI (iopMRI) data and CT/MRI reconstruction. Thirteen patients (nine female, four male, median age 26 ± 9.4 years) suffering from drug-resistant epilepsy were examined. After implantation, the position of subdural electrodes was evaluated by 3.0 T-MRI and thin-slice CCT for 3D reconstruction. Localization of electrodes was performed with the volume-rendering technique. Post-implantation and pre-explantation 1.5 T-iopMRI scans were coregistered with the 3D reconstructions to determine the extent of electrode dislocation. Intraoperative MRI at the time of explantation revealed a relevant electrode shift in one patient (8%) of 10 mm. Median electrode displacement was 1.7 ± 2.6 mm with a coregistration error of 1.9 ± 0.7 mm. The median accuracy of the neuronavigation system was 2.2 ± 0.9 mm. Six of twelve patients undergoing resective surgery were seizure free (Engel class 1A, median follow-up 37.5 ± 11.8 months). Comparison of pre-explantation and post-implantation iopMRI scans with CT/MRI data using the volume-rendering technique resulted in an accurate placement of electrodes. In one patient with a considerable electrode dislocation, the surgical approach and extent was changed due to the detected electrode shift. ECoG: electrocorticography; EZ: epileptogenic zone; iEEG: invasive EEG; iopMRI: intraoperative MRI; MEG: magnetoencephalography; PET: positron emission tomography; SPECT: single photon emission computed tomography; 3D: three-dimensional.

Development of a portable wireless system for bipolar concentric ECG recording

NASA Astrophysics Data System (ADS)

Prats-Boluda, G.; Ye-Lin, Y.; Bueno Barrachina, J. M.; Senent, E.; Rodriguez de Sanabria, R.; Garcia-Casado, J.

2015-07-01

Cardiovascular diseases (CVDs) remain the biggest cause of deaths worldwide. ECG monitoring is a key tool for early diagnosis of CVDs. Conventional monitors use monopolar electrodes resulting in poor spatial resolution surface recordings and requiring extensive wiring. High-spatial resolution surface electrocardiographic recordings provide valuable information for the diagnosis of a wide range of cardiac abnormalities, including infarction and arrhythmia. The aim of this work was to develop and test a wireless recording system for acquiring high spatial resolution ECG signals, based on a flexible tripolar concentric electrode (TCE) without cable wiring or external reference electrode which would make more comnfortable its use in clinical practice. For this, a portable, wireless sensor node for analogue conditioning, digitalization and transmission of a bipolar concentric ECG signal (BC-ECG) using a TCE and a Mason-likar Lead-I ECG (ML-Lead-I ECG) signal was developed. Experimental results from a total of 32 healthy volunteers showed that the ECG fiducial points in the BC-ECG signals, recorded with external and internal reference electrode, are consistent with those of simultaneous ML-Lead-I ECG. No statistically significant difference was found in either signal amplitude or morphology, regardless of the reference electrode used, being the signal-to-noise similar to that of ML-Lead-I ECG. Furthermore, it has been observed that BC-ECG signals contain information that could not available in conventional records, specially related to atria activity. The proposed wireless sensor node provides non-invasive high-local resolution ECG signals using only a TCE without additional wiring, which would have great potential in medical diagnosis of diseases such as atrial or ventricular fibrillations or arrhythmias that currently require invasive diagnostic procedures (catheterization).

Assessing Granger Causality in Electrophysiological Data: Removing the Adverse Effects of Common Signals via Bipolar Derivations.

PubMed

Trongnetrpunya, Amy; Nandi, Bijurika; Kang, Daesung; Kocsis, Bernat; Schroeder, Charles E; Ding, Mingzhou

2015-01-01

Multielectrode voltage data are usually recorded against a common reference. Such data are frequently used without further treatment to assess patterns of functional connectivity between neuronal populations and between brain areas. It is important to note from the outset that such an approach is valid only when the reference electrode is nearly electrically silent. In practice, however, the reference electrode is generally not electrically silent, thereby adding a common signal to the recorded data. Volume conduction further complicates the problem. In this study we demonstrate the adverse effects of common signals on the estimation of Granger causality, which is a statistical measure used to infer synaptic transmission and information flow in neural circuits from multielectrode data. We further test the hypothesis that the problem can be overcome by utilizing bipolar derivations where the difference between two nearby electrodes is taken and treated as a representation of local neural activity. Simulated data generated by a neuronal network model where the connectivity pattern is known were considered first. This was followed by analyzing data from three experimental preparations where a priori predictions regarding the patterns of causal interactions can be made: (1) laminar recordings from the hippocampus of an anesthetized rat during theta rhythm, (2) laminar recordings from V4 of an awake-behaving macaque monkey during alpha rhythm, and (3) ECoG recordings from electrode arrays implanted in the middle temporal lobe and prefrontal cortex of an epilepsy patient during fixation. For both simulation and experimental analysis the results show that bipolar derivations yield the expected connectivity patterns whereas the untreated data (referred to as unipolar signals) do not. In addition, current source density signals, where applicable, yield results that are close to the expected connectivity patterns, whereas the commonly practiced average re-reference method leads to erroneous results.

Extremely high resolution 3D electrical resistivity tomography to depict archaeological subsurface structures

NASA Astrophysics Data System (ADS)

Al-Saadi, Osamah; Schmidt, Volkmar; Becken, Michael; Fritsch, Thomas

2017-04-01

Electrical resistivity tomography (ERT) methods have been increasingly used in various shallow depth archaeological prospections in the last few decades. These non-invasive techniques are very useful in saving time, costs, and efforts. Both 2D and 3D ERT techniques are used to obtain detailed images of subsurface anomalies. In two surveyed areas near Nonnweiler (Germany), we present the results of the full 3D setup with a roll-along technique and of the quasi-3D setup (parallel and orthogonal profiles in dipole-dipole configuration). In area A, a dipole-dipole array with 96 electrodes in a uniform rectangular survey grid has been used in full 3D to investigate a presumed Roman building. A roll-along technique has been utilized to cover a large part of the archaeological site with an electrode spacing of 1 meter and with 0.5 meter for a more detailed image. Additional dense parallel 2D profiles have been carried out in dipole-dipole array with 0.25 meter electrode spacing and 0.25 meter between adjacent profiles in both direction for higher- resolution subsurface images. We have designed a new field procedure, which used an electrode array fixed in a frame. This facilitates efficient field operation, which comprised 2376 electrode positions. With the quasi 3D imaging, we confirmed the full 3D inversion model but at a much better resolution. In area B, dense parallel 2D profiles were directly used to survey the second target with also 0.25 meter electrode spacing and profiles separation respectively. The same field measurement design has been utilized and comprised 9648 electrode positions in total. The quasi-3D inversion results clearly revealed the main structures of the Roman construction. These ERT inversion results coincided well with the archaeological excavation, which has been done in some parts of this area. The ERT result successfully images parts from the walls and also smaller internal structures of the Roman building.

Extended electrode technique. [gas metal arc welding of metal plates

NASA Technical Reports Server (NTRS)

Schaper, V. D.; Pollack, A.

1972-01-01

The extended electrode technique is a unique welding process which utilizes manual gas-metal-arc (GMAW) semi-automatic equipment and close, square butt joints to effectively produce a weld. The technique takes advantage of the resistance heating of the electode extension to effect the root pass. Weldments as large as 72-X30-X2-inch have been fabricated with this technique under normal shipyard welding conditions. Mechanical properties and explosion bulge tests indicate that satisfactory results are obtained with this process. Potential savings of approximately 50 percent can be achieved in flat welding and repair of heavy structural steel members.

Second Plateau Voltage in Nickel-cadmium Cells

NASA Technical Reports Server (NTRS)

Vasanth, K. L.

1984-01-01

Sealed nickel cadmium cells having large number of cycles on them are discharged using Hg/HgO reference electrode. The negative electrode exhibits the second plateau. A SEM of negative plates of such cells show a number of large crystals of cadmium hydroxide. The large crystals on the negative plates disappear after continuous overcharging in flooded cells.

Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments

ERIC Educational Resources Information Center

Jin, Hao; Qin, Yiheng; Pan, Si; Alam, Arif U.; Dong, Shurong; Ghosh, Raja; Deen, M. Jamal

2018-01-01

pH determination is an essential experiment in many chemistry laboratories. It requires a potentiometric instrument with extremely low input bias current to accurately measure the voltage between a pH sensing electrode and a reference electrode. In this technology report, we propose an open-source potentiometric instrument for pH determination…

Solid state potentiometric gaseous oxide sensor

NASA Technical Reports Server (NTRS)

Wachsman, Eric D. (Inventor); Azad, Abdul Majeed (Inventor)

2003-01-01

A solid state electrochemical cell (10a) for measuring the concentration of a component of a gas mixture (12) includes first semiconductor electrode (14) and second semiconductor electrode (16) formed from first and second semiconductor materials, respectively. The materials are selected so as to undergo a change in resistivity upon contacting a gas component, such as CO or NO. An electrolyte (18) is provided in contact with the first and second semiconductor electrodes. A reference cell can be included in contact with the electrolyte. Preferably, a voltage response of the first semiconductor electrode is opposite in slope direction to that of the second semiconductor electrode to produce a voltage response equal to the sum of the absolute values of the control system uses measured pollutant concentrations to direct adjustment of engine combustion conditions.

Hybrid graphene electrodes for supercapacitors of high energy density

NASA Astrophysics Data System (ADS)

Zhang, Feifei; Tang, Jie; Shinya, Norio; Qin, Lu-Chang

2013-10-01

We describe a process of co-reduction to reduce dispersed graphene oxide (GO) and single-walled carbon nanotubes (SWNTs) simultaneously for preparation of hybrid electrodes for graphene supercapacitors. The SWNTs are in between the inter-layer space of graphene sheets as a spacer to prevent effectively restacking of graphene that often limits seriously the electrochemical performance of graphene supercapacitors. The SWNTs also act as conductive binders to improve the electrical conduction of the electrode. A high specific capacitance of 261 F g-1 for a single electrode and specific energy density of 123 W h kg-1 measured in the two-electrode configuration have been obtained in ionic liquid (EMI-TFSI). For interpretation of color in Fig. 6, the reader is referred to the web version of this article.

White organic light-emitting diodes with 4 nm metal electrode

NASA Astrophysics Data System (ADS)

Lenk, Simone; Schwab, Tobias; Schubert, Sylvio; Müller-Meskamp, Lars; Leo, Karl; Gather, Malte C.; Reineke, Sebastian

2015-10-01

We investigate metal layers with a thickness of only a few nanometers as anode replacement for indium tin oxide (ITO) in white organic light-emitting diodes (OLEDs). The ultrathin metal electrodes prove to be an excellent alternative that can, with regard to the angular dependence and efficiency of the OLED devices, outperform the ITO reference. Furthermore, unlike ITO, the thin composite metal electrodes are readily compatible with demanding architectures (e.g., top-emission or transparent OLEDs, device unit stacking, etc.) and flexible substrates. Here, we compare the sheet resistance of both types of electrodes on polyethylene terephthalate for different bending radii. The electrical performance of ITO breaks down at a radius of 10 mm, while the metal electrode remains intact even at radii smaller than 1 mm.

Chromium-doped Raney nickel catalyst for hydrogen electrodes in alkaline fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenjo, T.

Raney nickel is a relatively inexpensive and highly active nonnoble metal catalyst for hydrogen electrodes in alkaline fuel cells. Mund et al. (1977) have found that its catalytic activity is increased by doping involving transition metals, such a titanum, iron, and molybdenum. The present investigation is concerned with the preparation of hydrogen electrodes catalyzed with chromium-doped Raney nickel and the measurement of their polarization characteristics. On the basis of the obtained results, it is concluded that chromium is a good dopant for Raney nickel which is employed for hydrogen electrodes. Chromium improves and stabilizes the polarization characteristics of Raney nickelmore » electrodes. It is found that chromium-doped Raney nickel is more active than the titanium-doped catalyst. 6 references.« less

Surgical implications of perimodiolar cochlear implant electrode design: avoiding intracochlear damage and scala vestibuli insertion.

PubMed

Briggs, R J; Tykocinski, M; Saunders, E; Hellier, W; Dahm, M; Pyman, B; Clark, G M

2001-09-01

To review the mechanisms and nature of intracochlear damage associated with cochlear implant electrode array insertion, in particular, the various perimodiolar electrode designs. Make recommendations regarding surgical techniques for the Nucleus Contour electrode to ensure correct position and minimal insertion trauma. The potential advantages of increased modiolar proximity of intracochlear multichannel electrode arrays are a reduction in stimulation thresholds, an increase in dynamic range and more localized neural excitation. This may improve speech perception and reduce power consumption. These advantages may be negated if increased intracochlear damage results from the method used to position the electrodes close to the modiolus. A review of the University of Melbourne Department of Otolaryngology experience with temporal bone safety studies using the Nucleus standard straight electrode array and a variety of perimodiolar electrode array designs; comparison with temporal bone insertion studies from other centres and postmortem histopathology studies reported in the literature. Review of our initial clinical experience using the Nucleus Contour electrode array. The nature of intracochlear damage resulting from electrode insertion trauma ranges from minor, localized, spiral ligament tear to diffuse organ of Corti disruption and osseous spiral lamina fracture. The type of damage depends on the mechanical characteristics of the electrode array, the stiffness, curvature and size of the electrode in relation to the scala, and the surgical technique. The narrow, flexible, straight arrays are the least traumatic. Pre-curved or stiffer arrays are associated with an incidence of basilar membrane perforation. The cochleostomy must be correctly sited in relation to the round window to ensure scala tympani insertion. A cochleostomy anterior to the round window rather than inferior may lead to scala media or scala vestibuli insertion. Proximity of electrodes to the modiolus can be achieved without intracochlear damage provided the electrode array is a free fit within the scala, of appropriate size and shape, and accurate scala tympani insertion is performed.

Fabrication and characterization of microsieve electrode array (µSEA) enabling cell positioning on 3D electrodes

NASA Astrophysics Data System (ADS)

Schurink, B.; Tiggelaar, R. M.; Gardeniers, J. G. E.; Luttge, R.

2017-01-01

Here the fabrication and characterization of a novel microelectrode array for electrophysiology applications is described, termed a micro sieve electrode array (µSEA). This silicon based µSEA device allows for hydrodynamic parallel positioning of single cells on 3D electrodes realized on the walls of inverted pyramidal shaped pores. To realize the µSEA, a previously realized silicon sieving structure is provided with a patterned boron doped poly-silicon, connecting the contact electrodes with the 3D sensing electrodes in the pores. A LPCVD silicon-rich silicon nitride layer was used as insulation. The selective opening of this insulation layer at the ends of the wiring lines allows to generate well-defined contact and sensing electrodes according to the layout used in commercial microelectrode array readers. The main challenge lays in the simultaneously selective etching of material at both the planar surface (contact electrode) as well as in the sieving structure containing the (3D) pores (sensing electrodes). For the generation of 3D electrodes in the pores a self-aligning technique was developed using the pore geometry to our advantage. This technique, based on sacrificial layer etching, allows for the fine tuning of the sensing electrode surface area and thus supports the positioning and coupling of single cells on the electrode surface in relation to the cell size. Furthermore, a self-aligning silicide is formed on the sensing electrodes to favour the electrical properties. Experiments were performed to demonstrate the working principle of the µSEA using different types of neuronal cells. Capture efficiency in the pores was  >70% with a 70% survival rate of the cell maintained for up to 14 DIV. The TiSi2-boron-doped-poly-silicon sensing electrodes of the µSEA were characterized, which indicated noise levels of  <15 µV and impedance values of 360 kΩ. These findings potentially allow for future electrophysiological measurements using the µSEA.

Brief review: Preparation techniques of biomass based activated carbon monolith electrode for supercapacitor applications

NASA Astrophysics Data System (ADS)

Taer, Erman; Taslim, Rika

2018-02-01

The synthesis of activated carbon monolith electrode made from a biomass material using the hydrolytic pressure or the pelletization technique of pre-carbonized materials is one of standard reported methods. Several steps such as pre-carbonization, milling, chemical activation, hydraulic press, carbonization, physical activation, polishing and washing need to be accomplished in the production of electrodes by this method. This is relatively a long process that need to be simplified. In this paper we present the standard method and proceed with the introduction to several alternative methods in the synthesis of activated carbon monolith electrodes. The alternative methods were emphasized on the selection of suitable biomass materials. All of carbon electrodes prepared by different methods will be analyzed for physical and electrochemical properties. The density, degree of crystallinity, surface morphology are examples for physical study and specific capacitance was an electrochemical properties that has been analysed. This alternative method has offered a specific capacitance in the range of 10 to 171 F/g.

Operando analysis of lithium profiles in Li-ion batteries using nuclear microanalysis

NASA Astrophysics Data System (ADS)

Surblé, S.; Paireau, C.; Martin, J.-F.; Tarnopolskiy, V.; Gauthier, M.; Khodja, H.; Daniel, L.; Patoux, S.

2018-07-01

A wide variety of analytical methods are used for studying the behavior of lithium-ion batteries and particularly the lithium ion distribution in the electrodes. However, the development of in situ/operando techniques proved powerful to understand the mechanisms responsible for the lithium trapping and then the aging phenomenon. Herein, we report the design of an electrochemical cell to profile operando lithium concentration in LiFePO4 electrodes using Ion Beam Analysis techniques. The specificity of the cell resides in its ability to not only provide qualitative information about the elements present but above all to measure quantitatively their content in the electrode at different states of charge of the battery. The nuclear methods give direct information about the degradation of the electrolyte and particularly reveal inhomogeneous distributions of lithium and fluorine along the entire thickness of the electrode. Higher concentrations of fluorine is detected near the electrode/electrolyte interface while a depletion of lithium is observed near the current collector at high states of charge.

Deep Brain Stimulation of Heschl Gyrus: Implantation Technique, Intraoperative Localization, and Effects of Stimulation.

PubMed

Donovan, Chris; Sweet, Jennifer; Eccher, Matthew; Megerian, Cliff; Semaan, Maroun; Murray, Gail; Miller, Jonathan

2015-12-01

Tinnitus is a source of considerable morbidity, and neuromodulation has been shown to be a potential treatment option. However, the location of the primary auditory cortex within Heschl gyrus in the temporal operculum presents challenges for targeting and electrode implantation. To determine whether anatomic targeting with intraoperative verification using evoked potentials can be used to implant electrodes directly into the Heschl gyrus (HG). Nine patients undergoing stereo-electroencephalogram evaluation for epilepsy were enrolled. HG was directly targeted on volumetric magnetic resonance imaging, and framed stereotaxy was used to implant an electrode parallel to the axis of the gyrus by using an oblique anterolateral-posteromedial trajectory. Intraoperative evoked potentials from auditory stimuli were recorded from multiple electrode contacts. Postoperatively, stimulation of each electrode was performed and participants were asked to describe the percept. Audiometric analysis was performed for 2 participants during subthreshold stimulation. Sounds presented to the contralateral and ipsilateral ears produced evoked potentials in HG electrodes in all participants intraoperatively. Stimulation produced a reproducible sensation of sound in all participants with perceived volume proportional to amplitude. Four participants reported distinct sounds when different electrodes were stimulated, with more medial contacts producing tones perceived as higher in pitch. Stimulation was not associated with adverse audiometric effects. There were no complications of electrode implantation. Direct anatomic targeting with physiological verification can be used to implant electrodes directly into primary auditory cortex. If deep brain stimulation proves effective for intractable tinnitus, this technique may be useful to assist with electrode implantation. DBS, deep brain stimulatorEEG, electroencephalographyHG, Heschl gyrus.

Inkjet printing of carbon black electrodes for dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Schlatter, Samuel; Rosset, Samuel; Shea, Herbert

2017-04-01

Inkjet printing is an appealing technique to print electrodes for Dielectric Elastomer Actuators (DEAs). Here we present the preparation and ink-jet printing of a carbon black electrode mixture and characterise its properties. Carbon black has been used extensively in the past because it is very compliant; however, it has a high resistance and can be very dirty to work with. In this paper we show that carbon black remains an appropriate electrode material, and when inkjet printed can be used to fabricate devices meeting today's demanding requirements. DEAs are becoming thinner to decrease actuation voltages and are shrinking in size to match the scale of the devices in the biomedical field, tuneable optics, and microfluidics. Inkjet printing addresses both of these problems. Firstly, Inkjet printing is a non-contact technique and can print on very thin freestanding membranes. Secondly, the high precision of inkjet printers makes it possible to print complex electrode geometries in the millimetre scale. We demonstrate the advantages of inkjet printing and carbon black electrodes by conducting a full characterisation of the printed electrodes. The printed carbon black electrodes have resistances as low as 13kΩ/□, an elastic modulus of approximately 1MPa, and a cyclic resistance swing which increases by 7% over 1500 cycles at 50% stretch. We also demonstrate a DEA with printed carbon black electrodes with a diametral stretch of 8.8% at an electric field of approximately 94V/μm. Finally a qualitative test is conducted to show that the printed carbon black electrode is extremely hardwearing.

Accuracy of frame-based stereotactic depth electrode implantation during craniotomy for subdural grid placement.

PubMed

Munyon, Charles N; Koubeissi, Mohamad Z; Syed, Tanvir U; Lüders, Hans O; Miller, Jonathan P

2013-01-01

Frame-based stereotaxy and open craniotomy may seem mutually exclusive, but invasive electrophysiological monitoring can require broad sampling of the cortex and precise targeting of deeper structures. The purpose of this study is to describe simultaneous frame-based insertion of depth electrodes and craniotomy for placement of subdural grids through a single surgical field and to determine the accuracy of depth electrodes placed using this technique. A total of 6 patients with intractable epilepsy underwent placement of a stereotactic frame with the center of the planned cranial flap equidistant from the fixation posts. After volumetric imaging, craniotomy for placement of subdural grids was performed. Depth electrodes were placed using frame-based stereotaxy. Postoperative CT determined the accuracy of electrode placement. A total of 31 depth electrodes were placed. Mean distance of distal electrode contact from the target was 1.0 ± 0.15 mm. Error was correlated to distance to target, with an additional 0.35 mm error for each centimeter (r = 0.635, p < 0.001); when corrected, there was no difference in accuracy based on target structure or method of placement (prior to craniotomy vs. through grid, p = 0.23). The described technique for craniotomy through a stereotactic frame allows placement of subdural grids and depth electrodes without sacrificing the accuracy of a frame or requiring staged procedures.

Development of in vivo impedance spectroscopy techniques for measurement of micropore formation following microneedle insertion

PubMed Central

Brogden, Nicole K.; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J.; Stinchcomb, Audra L.

2013-01-01

Microneedles provide a minimally invasive means to enhance skin permeability by creating micron-scale channels (micropores) that provide a drug delivery pathway. Adequate formation of the micropores is critical to the success of this unique drug delivery technique. The objective of these studies was to develop sensitive and reproducible impedance spectroscopy techniques to monitor micropore formation in animal models and human subjects. Hairless guinea pigs, a Yucatan miniature pig, and human volunteers were treated with 100 microneedle insertions per site following an overnight pre-hydration period. Repeated measurements were made pre- and post-microneedle treatment using dry and gel Ag/AgCl electrodes applied with light vs. direct pressure to hold the electrode to the skin surface. Impedance measurements dropped significantly post-microneedle application at all sites (p < 0.05, irrespective of electrode type or gel application), confirming micropore formation. In the Yucatan pig and human subjects, gel electrodes with direct pressure yielded the lowest variability (demonstrated by lower %RSD), whereas dry electrodes with direct pressure were superior in the guinea pigs. These studies confirm that impedance measurements are suitable for use in both clinical and animal research environments to monitor formation of new micropores that will allow for drug delivery through the impermeable skin layers. PMID:23589356

Development of in vivo impedance spectroscopy techniques for measurement of micropore formation following microneedle insertion.

PubMed

Brogden, Nicole K; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J; Stinchcomb, Audra L

2013-06-01

Microneedles (MNs) provide a minimally invasive means to enhance skin permeability by creating micron-scale channels (micropores) that provide a drug delivery pathway. Adequate formation of the micropores is critical to the success of this unique drug delivery technique. The objective of the current work was to develop sensitive and reproducible impedance spectroscopy techniques to monitor micropore formation in animal models and human subjects. Hairless guinea pigs, a Yucatan miniature pig, and human volunteers were treated with 100 MN insertions per site following an overnight prehydration period. Repeated measurements were made pre- and post-MN treatment using dry and gel Ag/AgCl electrodes applied with light verses direct pressure to hold the electrode to the skin surface. Impedance measurements dropped significantly post-MN application at all sites (p < 0.05, irrespective of electrode type or gel application), confirming micropore formation. In the Yucatan pig and human subjects, gel electrodes with direct pressure yielded the lowest variability (demonstrated by lower %relative standard deviation), whereas dry electrodes with direct pressure were superior in the guinea pigs. These studies confirm that impedance measurements are suitable for use in both clinical and animal research environments to monitor the formation of new micropores that will allow for drug delivery through the impermeable skin layers. Copyright © 2013 Wiley Periodicals, Inc.

Characterization of activated titanium solid reference electrodes for corrosion testing of steel in concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castro, P.; Maldonado, L.; Saguees, A.A.

1996-08-01

Small bars of Ti activated with mixed-metal oxide (commercially produced for permanent impressed-current anodes in cathodic protection) were used as embedded reference electrodes (RE) in concrete. Their electrochemical behavior was evaluated through measurements and analyses of potential, electrochemical impedance spectroscopy (EIS), cyclic polarization (CP), and galvanostatic tests in buffer solutions of pH 4, 7, and 10, saturated calcium hydroxide, simulated concrete pore solution (SPS) with pH = 13.5, and various concrete mixes with and without pozzolanic additions as cement replacement. Effects of deaeration and sodium chloride additions were evaluated. The potential of the activated Ti rod (ATR) electrodes resembled themore » expected dependence for the system Ir{sub 2}O{sub 3} + H{sub 2}O = 2IrO{sub 2} + 2H{sup +} + 2e{sup {minus}} in aqueous solutions. The ATR electrode presented generally good stability with time in concrete for up to 900 days. Anomalous behavior was found in two concrete mixes with the highest pozzolanic content. Results from EIS tests revealed a constant phase element (CPE) behavior, which agreed with results of CP tests that showed a very large apparent interfacial capacitance. The apparent capacitance was on the order of 10{sup {minus}2} F/cm{sup 2}, resulting in very low impedance, which is advantageous when using ATR electrodes to conduct EIS or polarization resistance tests. Galvanostatic application of 0.075 {mu}A/cm{sup 2} caused little variation of potential with time, indicating the presence of a finite polarization resistance. Little short-term susceptibility of the ATR electrode potential to NaCl additions was found. The ATR electrode potential also showed little short-term sensitivity to variations in oxygen partial pressure.« less

Dose measurement in heterogeneous phantoms with an extrapolation chamber

NASA Astrophysics Data System (ADS)

Deblois, Francois

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water(TM) and bone-equivalent material was used for determining absolute dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x-rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The air gaps used were between 2 and 3 mm and the sensitive air volume of the extrapolation chamber was remotely controlled through the motion of the motorized piston with a precision of +/-0.0025 mm. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain dose data for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC from 0.7 to ˜2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water(TM) PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). The collecting electrode material in comparison with the polarizing electrode material has a larger effect on the electrode correction factor; the thickness of thin electrodes, on the other hand, has a negligible effect on dose determination. The uncalibrated hybrid PEEC is an accurate and absolute device for measuring the dose directly in bone material in conjunction with appropriate correction factors determined with Monte Carlo techniques.

A solid-state thin-film Ag/AgCl reference electrode coated with graphene oxide and its use in a pH sensor.

PubMed

Kim, Tae Yong; Hong, Sung A; Yang, Sung

2015-03-17

In this study, we describe a novel solid-state thin-film Ag/AgCl reference electrode (SSRE) that was coated with a protective layer of graphene oxide (GO). This layer was prepared by drop casting a solution of GO on the Ag/AgCl thin film. The potential differences exhibited by the SSRE were less than 2 mV for 26 days. The cyclic voltammograms of the SSRE were almost similar to those of a commercial reference electrode, while the diffusion coefficient of Fe(CN)63- as calculated from the cathodic peaks of the SSRE was 6.48 × 10-6 cm2/s. The SSRE was used in conjunction with a laboratory-made working electrode to determine its suitability for practical use. The average pH sensitivity of this combined sensor was 58.5 mV/pH in the acid-to-base direction; the correlation coefficient was greater than 0.99. In addition, an integrated pH sensor that included the SSRE was packaged in a secure digital (SD) card and tested. The average sensitivity of the chip was 56.8 mV/pH, with the correlation coefficient being greater than 0.99. In addition, a pH sensing test was also performed by using a laboratory-made potentiometer, which showed a sensitivity of 55.4 mV/pH, with the correlation coefficient being greater than 0.99.

A review of electrode materials for electrochemical supercapacitors.

PubMed

Wang, Guoping; Zhang, Lei; Zhang, Jiujun

2012-01-21

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

Preliminary flight prototype silver ion monitoring system

NASA Technical Reports Server (NTRS)

Brady, J.

1974-01-01

The design, fabrication, and testing of a preliminary flight prototype silver ion monitoring system based on potentiometric principles and utilizing a solid-state silver sulfide electrode paired with a pressurized double-junction reference electrode housing a replaceable electrolyte reservoir is described. The design provides automatic electronic calibration utilizing saturated silver bromide solution as a silver ion standard. The problem of loss of silver ion from recirculating fluid, its cause, and corrective procedures are reported. The instability of the silver sulfide electrode is discussed as well as difficulties met in implementing the autocalibration procedure.

Electrochemical sensor for monitoring electrochemical potentials of fuel cell components

DOEpatents

Kunz, Harold R.; Breault, Richard D.

1993-01-01

An electrochemical sensor comprised of wires, a sheath, and a conduit can be utilized to monitor fuel cell component electric potentials during fuel cell shut down or steady state. The electrochemical sensor contacts an electrolyte reservoir plate such that the conduit wicks electrolyte through capillary action to the wires to provide water necessary for the electrolysis reaction which occurs thereon. A voltage is applied across the wires of the electrochemical sensor until hydrogen evolution occurs at the surface of one of the wires, thereby forming a hydrogen reference electrode. The voltage of the fuel cell component is then determined with relation to the hydrogen reference electrode.

An Electrochemical Experiment Using an Optically Transparent Thin Layer Electrode

ERIC Educational Resources Information Center

DeAngelis, Thomas P.; Heineman, William R.

1976-01-01

Describes a unified experiment in which an optically transparent thin layer electrode is used to illustrate the techniques of thin layer electrochemistry, cyclic voltammetry, controlled potential coulometry, and spectroelectrochemistry. (MLH)

Requirements for optimization of electrodes and electrolyte for the iron/chromium Redox flow cell

NASA Technical Reports Server (NTRS)

Jalan, V.; Stark, H.; Giner, J.

1981-01-01

Improved catalyzation techniques that included a pretreatment of carbon substrate and provided normalized carbon surface for uniform gold deposition were developed. This permits efficient use of different batches of carbon felt materials which initially vary significantly in their physical and surface chemical properties, as well as their electrochemical behavior. Further modification of gold impregnation technique gave the best performing electrodes. In addition to the linear sweep voltammetry, cyclic voltammetry was used to determine the effects of different activation procedures on the Cr(3)/Cr(2) Redox and H2 evolution reactions. The roles of carbon, gold and lead in the overall Redox cycle are identified. The behavior of the electrodes at both normal battery operating potentials and more extreme potentials is discussed preparing efficient and stable electrodes for the energy storage battery is implicated.

Ruthenium oxide ion selective thin-film electrodes for engine oil acidity monitoring

NASA Astrophysics Data System (ADS)

Maurya, D. K.; Sardarinejad, A.; Alameh, K.

2015-06-01

We demonstrate the concept of a low-cost, rugged, miniaturized ion selective electrode (ISE) comprising a thin film RuO2 on platinum sensing electrode deposited using RF magnetron sputtered in conjunction with an integrated Ag/AgCl and Ag reference electrodes for engine oil acidity monitoring. Model oil samples are produced by adding nitric acid into fresh fully synthetic engine oil and used for sensor evaluation. Experimental results show a linear potential-versus-acid-concentration response for nitric acid concentration between 0 (fresh oil) to 400 ppm, which demonstrate the accuracy of the RuO2 sensor in real-time operation, making it attractive for use in cars and industrial engines.

Electrochemical sensor having suspended element counter electrode and deflection method for current sensing

DOEpatents

Thundat, Thomas G.; Brown, Gilbert M.

2010-05-18

An electrochemical suspended element-based sensor system includes a solution cell for holding an electrolyte comprising solution including at least one electrochemically reducible or oxidizable species. A working electrode (WE), reference electrode (RE) and a counter electrode (CE) are disposed in the solution. The CE includes an asymmetric suspended element, wherein one side of the suspended element includes a metal or a highly doped semiconductor surface. The suspended element bends when current associated with reduction or oxidation of the electrochemically reducible or oxidizable species at the WE passes through the suspended element. At least one measurement system measures the bending of the suspended element or a parameter which is a function of the bending.

Investigation on Electrochemical Properties of Polythiophene Nanocomposite with Graphite Derivatives as Supercapacitor Material on Breath Figure-Decorated PMMA Electrode

NASA Astrophysics Data System (ADS)

Azimi, Mona; Abbaspour, Mohsen; Fazli, Ali; Setoodeh, Hamideh; Pourabbas, Behzad

2018-03-01

Breath figures have been formed by the direct breath figure method on polymethyl methacrylate electrode sand hexagonal oriented holes with 0.5- to 10- μm2 surface area have been created. Deposition of materials on the electrodes has been performed by the spray-coating method. polythiophene (PTh) nanoparticles, polythiophene-graphene oxide (PTh-GO) and polythiophene-reduced graphene oxide (PTh-G) nanocomposites were synthesized by emulsion polymerization, while characterization of synthetic materials have been carried out by Fourier transform infrared, Χ-ray diffraction, transmission electron microscopy, UV-Vis spectroscopy and field emission scanning electron microscopy techniques. Also, the electrochemical properties of the designed electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques. Specific capacitance of porous electrodes coated by PTh nanoparticles, PTh-GO and PTh-G nanocomposites were calculated from cyclic voltammetry curves at 5 mV/s scan rate, andthe values are 3.5 F/g, 16.39 F/g, and 28.68 F/g, respectively. Also, the energy density of each electrode at 5 mV/s scan rate has been calculated and the results show that incorporation of GO and G nanolayers with PTh nanoparticles enhances the electrochemical properties of electrodes.

A PDMS-Based Conical-Well Microelectrode Array for Surface Stimulation and Recording of Neural Tissues

PubMed Central

Guo, Liang; Meacham, Kathleen W.; Hochman, Shawn

2012-01-01

A method for fabricating polydimethylsiloxane (PDMS)-based microelectrode arrays (MEAs) featuring novel conical-well microelectrodes is described. The fabrication technique is reliable and efficient, and facilitates controllability over both the depth and the slope of the conical wells. Because of the high PDMS elasticity (as compared to other MEA substrate materials), this type of compliant MEA is promising for acute and chronic implantation in applications that benefit from conformable device contact with biological tissue surfaces and from minimal tissue damage. The primary advantage of the conical-well microelectrodes—when compared to planar electrodes—is that they provide an improved contact on tissue surface, which potentially provides isolation of the electrode microenvironment for better electrical interfacing. The raised wells increase the uniformity of current density distributions at both the electrode and tissue surfaces, and they also protect the electrode material from mechanical damage (e.g. from rubbing against the tissue). Using this technique, electrodes have been fabricated with diameters as small as 10µm and arrays have been fabricated with center-to-center electrode spacings of 60µm. Experimental results are presented, describing electrode-profile characterization, electrode-impedance measurement, and MEA-performance evaluation on fiber bundle recruitment in spinal cord white matter. PMID:20550983

Reliability of high-strain ionomeric polymer transducers fabricated using the novel direct assembly process

NASA Astrophysics Data System (ADS)

Akle, Barbar; Nawshin, Saila; Leo, Donald

2006-03-01

Ionomeric polymer transducers have received considerable attention in the past several years. These actuators, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typically, ionic polymer actuators are composed of Nafion-117 membranes with platinum electrodes and are saturated with water diluents. Recently the authors have developed a novel fabrication technique named the Direct Assembly Process (DAP), which allowed good control on electrode morphology and composition. The DAP consists of spraying two high surface area metal-ionomer electrodes on a Nafion membrane. A single- walled carbon nanotubes (SWNT) and ruthenium dioxide (RuO II) hybrid electrode was sprayed on a Formamide hydrated Nafion-117 membrane using the DAP method. This transducer was shown to generate 9.4% peak-peak strain under the application of +/-2V at a strain rate of 1%/sec. Furthermore using the DAP one is capable of incorporating several types of diluents in ionomeric polymer transducers. Transducers with ionic liquid diluents are demonstrated to operate in air for long periods of time. In this work we will present a reliability study of transducers fabricated using the DAP. Each transducer is tested under a frequency range of 0.2Hz to 1Hz, and a potential of +/-1V to +/-3V. Water hydrated transducers dehydrates and stop moving within 5 minutes while operating in air under +/-2V. Transducers with Formamide diluents operate for 20,000 cycles under +/-1.5V and 0.5Hz (around 11hrs), while they degrade in less than 3000 cycles under +/-2V and 0.5Hz. Ionic liquid based transducers are demonstrated to operate in air for over 400,000 with little loss in performance, and over 1 million cycle with a loss of only 43%. Actuators with several electrode compositions are fabricated and a correlation between the reliability of ionic liquid-ionic polymer transducers and maximum strain will be presented. This correlation will be used to assess the adhesion between the high surface area electrodes and the Nafion membrane. SEM images of tested transducers will be presented.

Nanoscale visualization of redox activity at lithium-ion battery cathodes.

PubMed

Takahashi, Yasufumi; Kumatani, Akichika; Munakata, Hirokazu; Inomata, Hirotaka; Ito, Komachi; Ino, Kosuke; Shiku, Hitoshi; Unwin, Patrick R; Korchev, Yuri E; Kanamura, Kiyoshi; Matsue, Tomokazu

2014-11-17

Intercalation and deintercalation of lithium ions at electrode surfaces are central to the operation of lithium-ion batteries. Yet, on the most important composite cathode surfaces, this is a rather complex process involving spatially heterogeneous reactions that have proved difficult to resolve with existing techniques. Here we report a scanning electrochemical cell microscope based approach to define a mobile electrochemical cell that is used to quantitatively visualize electrochemical phenomena at the battery cathode material LiFePO4, with resolution of ~100 nm. The technique measures electrode topography and different electrochemical properties simultaneously, and the information can be combined with complementary microscopic techniques to reveal new perspectives on structure and activity. These electrodes exhibit highly spatially heterogeneous electrochemistry at the nanoscale, both within secondary particles and at individual primary nanoparticles, which is highly dependent on the local structure and composition.

Automated detection and labeling of high-density EEG electrodes from structural MR images.

PubMed

Marino, Marco; Liu, Quanying; Brem, Silvia; Wenderoth, Nicole; Mantini, Dante

2016-10-01

Accurate knowledge about the positions of electrodes in electroencephalography (EEG) is very important for precise source localizations. Direct detection of electrodes from magnetic resonance (MR) images is particularly interesting, as it is possible to avoid errors of co-registration between electrode and head coordinate systems. In this study, we propose an automated MR-based method for electrode detection and labeling, particularly tailored to high-density montages. Anatomical MR images were processed to create an electrode-enhanced image in individual space. Image processing included intensity non-uniformity correction, background noise and goggles artifact removal. Next, we defined a search volume around the head where electrode positions were detected. Electrodes were identified as local maxima in the search volume and registered to the Montreal Neurological Institute standard space using an affine transformation. This allowed the matching of the detected points with the specific EEG montage template, as well as their labeling. Matching and labeling were performed by the coherent point drift method. Our method was assessed on 8 MR images collected in subjects wearing a 256-channel EEG net, using the displacement with respect to manually selected electrodes as performance metric. Average displacement achieved by our method was significantly lower compared to alternative techniques, such as the photogrammetry technique. The maximum displacement was for more than 99% of the electrodes lower than 1 cm, which is typically considered an acceptable upper limit for errors in electrode positioning. Our method showed robustness and reliability, even in suboptimal conditions, such as in the case of net rotation, imprecisely gathered wires, electrode detachment from the head, and MR image ghosting. We showed that our method provides objective, repeatable and precise estimates of EEG electrode coordinates. We hope our work will contribute to a more widespread use of high-density EEG as a brain-imaging tool.

Automated detection and labeling of high-density EEG electrodes from structural MR images

NASA Astrophysics Data System (ADS)

Marino, Marco; Liu, Quanying; Brem, Silvia; Wenderoth, Nicole; Mantini, Dante

2016-10-01

Objective. Accurate knowledge about the positions of electrodes in electroencephalography (EEG) is very important for precise source localizations. Direct detection of electrodes from magnetic resonance (MR) images is particularly interesting, as it is possible to avoid errors of co-registration between electrode and head coordinate systems. In this study, we propose an automated MR-based method for electrode detection and labeling, particularly tailored to high-density montages. Approach. Anatomical MR images were processed to create an electrode-enhanced image in individual space. Image processing included intensity non-uniformity correction, background noise and goggles artifact removal. Next, we defined a search volume around the head where electrode positions were detected. Electrodes were identified as local maxima in the search volume and registered to the Montreal Neurological Institute standard space using an affine transformation. This allowed the matching of the detected points with the specific EEG montage template, as well as their labeling. Matching and labeling were performed by the coherent point drift method. Our method was assessed on 8 MR images collected in subjects wearing a 256-channel EEG net, using the displacement with respect to manually selected electrodes as performance metric. Main results. Average displacement achieved by our method was significantly lower compared to alternative techniques, such as the photogrammetry technique. The maximum displacement was for more than 99% of the electrodes lower than 1 cm, which is typically considered an acceptable upper limit for errors in electrode positioning. Our method showed robustness and reliability, even in suboptimal conditions, such as in the case of net rotation, imprecisely gathered wires, electrode detachment from the head, and MR image ghosting. Significance. We showed that our method provides objective, repeatable and precise estimates of EEG electrode coordinates. We hope our work will contribute to a more widespread use of high-density EEG as a brain-imaging tool.

Examining of the segmented electrode use from the viewpoint of the electrolyte volatilizing in molten carbonate fuel cell

NASA Astrophysics Data System (ADS)

Sugiura, Kimihiko; Yamauchi, Makoto; Soga, Masatsugu; Tanimoto, Kazumi

Molten carbonate fuel cells (MCFCs) have entered the pre-commercialization phase, and have been experimentally demonstrated in real world applications, including beer brewery, etc. However, though MCFCs have a high potential and an enough operating experience as an energy supply system, they are not explosively widespread. One of these reasons is cost of cell components. Because the thickness of both electrodes is 0.8 mm and both electrodes are made of porous plates of 1 m 2 of the electrode area, they are often broken by a thermal stress in the sintering process of an electrode and by a worker's carelessness at the cell assembly process. Generally, because these cracking electrodes can potentially cause electrolyte leakage and gas crossover, they are not used to a MCFC stack and are disposed of. Therefore, it made the cost of MCFC be raised. The performance of a cell that uses a mosaic electrode has been evaluated. However, the causal relation between the cracking of an electrode and an electrolyte-leakage has not been yet confirmed. If this causal relationship is elucidated, a cracking electrode or a mosaic electrode can be used to MCFC, such that the cost of MCFC systems would consequently decrease. Therefore, we studied the causal relation between the cracking of an electrode and electrolyte leakage and gas crossover using a visualization technique. In the case of an anode electrode where the centre section of a cell has crack of about 1 mm, the electrolyte leakage from this crack could not be observed by the visualization technique. Moreover, the gas crossover could not be also observed by the visualization technique, and nitrogen in the anode exhaust gas was not detected by a gas chromatography. However, the electrolyte leakage observed from the wet-seal section though the gap between the separator and the electrode was always 1 mm or less. Therefore, electrolyte leakage hardly occurs, even if a cracked anode electrode is installed into the centre section of the cell. On the other hand, although the volatile substance gushes from the wet seal section, the electrolyte leakage/volatilization phenomenon does not occur at the centre of the cell or at the gap between each segmented cathode. The volatile substance in the cathode gas-distributor-channel is composed of the electrolyte mist and the electrolyte volatile substance, and the rate of release is about 2.5 times that of anode side. Although the segmented electrode can be applied to the anode in a MCFC, it cannot be applied to a cathode from the viewpoint of the electrolyte leakage/volatilization.

Disposable inkjet-printed electrochemical platform for detection of clinically relevant HER-2 breast cancer biomarker.

PubMed

Carvajal, Susanita; Fera, Samantha N; Jones, Abby L; Baldo, Thaisa A; Mosa, Islam M; Rusling, James F; Krause, Colleen E

2018-05-01

Rapidly fabricated, disposable sensor platforms hold tremendous promise for point-of-care detection. Here, we present an inexpensive (< $0.25) fully inkjet printed electrochemical sensor with integrated counter, reference, and working electrodes that is easily scalable for commercial fabrication. The electrochemical sensor platform featured an inkjet printed gold working 8-electrode array (WEA) and counter electrode (CE), along with an inkjet -printed silver electrode that was chlorinated with bleach to produce a Ag/AgCl quasi-reference electrode (RE). As proof of concept, the electrochemical sensor was successfully applied for detection of clinically relevant breast cancer biomarker Human Epidermal Growth Factor Receptor 2 (HER-2). Capture antibodies were bound to a chemically modified surface on the WEA and placed into a microfluidic device. A full sandwich immunoassay was constructed following a simultaneous injection of target protein, biotinylated antibody, and polymerized horseradish peroxide labels into the microfluidic device housing the WEA. With an ultra fast assay time, of only 15mins a clinically relevant limit of detection of 12pgmL -1 was achieved. Excellent reproducibility and sensitivity were observed through recovery assays preformed in human serum with recoveries ranging from 76% to 103%. These easily fabricated and scalable electrochemical sensor platforms can be readily adapted for multiplex detection following this rapid assay protocol for cancer diagnostics. Copyright © 2018 Elsevier B.V. All rights reserved.

Binaural Pitch Fusion in Bilateral Cochlear Implant Users.

PubMed

Reiss, Lina A J; Fowler, Jennifer R; Hartling, Curtis L; Oh, Yonghee

Binaural pitch fusion is the fusion of stimuli that evoke different pitches between the ears into a single auditory image. Individuals who use hearing aids or bimodal cochlear implants (CIs) experience abnormally broad binaural pitch fusion, such that sounds differing in pitch by as much as 3-4 octaves are fused across ears, leading to spectral averaging and speech perception interference. The goal of this study was to determine if adult bilateral CI users also experience broad binaural pitch fusion. Stimuli were pulse trains delivered to individual electrodes. Fusion ranges were measured using simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus to find the range that fused with the reference stimulus. Bilateral CI listeners had binaural pitch fusion ranges varying from 0 to 12 mm (average 6.1 ± 3.9 mm), where 12 mm indicates fusion over all electrodes in the array. No significant correlations of fusion range were observed with any subject factors related to age, hearing loss history, or hearing device history, or with any electrode factors including interaural electrode pitch mismatch, pitch match bandwidth, or within-ear electrode discrimination abilities. Bilateral CI listeners have abnormally broad fusion, similar to hearing aid and bimodal CI listeners. This broad fusion may explain the variability of binaural benefits for speech perception in quiet and in noise in bilateral CI users.

Novel PVC-membrane electrode for flow injection potentiometric determination of Biperiden in pharmaceutical preparations.

PubMed

Khaled, Elmorsy; El-Sabbagh, Inas A; El-Kholy, N G; Ghahni, E Y Abdel

2011-12-15

The construction and performance characteristics of Biperiden (BP) polyvinyl chloride (PVC) electrodes are described. Different methods for electrode fabrication are tested including; incorporation of BP-ion pairs (BP-IPs), incorporation of ion pairing agents, or soaking the plain electrode in BP-ion pairs suspension solution. Electrode matrices were optimized referring to the effect of modifier content and nature, plasticizer and the method of modification. The proposed electrodes work satisfactorily in the BP concentration range from 10(-5) to 10(-2)mol L(-1), with fast response time (7s) and adequate operational lifetime (28 days). The electrode potential is pH independent within the range 2.0-7.0, with good selectivity towards BP in presence of various interfering species. The developed electrodes have been applied for potentiometric determination of BP in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. FIA offers the advantages of accuracy and automation feasibility with high sampling frequency. The dissolution profile for Akineton tablets (2mg BP/tablet) was studied using the proposed electrode in comparison with the official methods. Copyright © 2011 Elsevier B.V. All rights reserved.

The Trans-Cis Isomerisation of Bis(dioxolene)bis(pyridine)Ruthenium Complexes

DTIC Science & Technology

1992-03-03

and counter electrodes, and a AgCl/Ag quasi-reference electrode with ferrocene (Fc) as an internal standard. The Fc/Fc + couple lies at + 0.425 V vs...species which isomerise in chloroform at from 500C (actual temperature depending upon the phosphine ) to the all * ccc-Ru(CO) 2CI2(PR 3)2 species which

A novel intra-operative, high-resolution atrial mapping approach.

PubMed

Yaksh, Ameeta; van der Does, Lisette J M E; Kik, Charles; Knops, Paul; Oei, Frans B S; van de Woestijne, Pieter C; Bekkers, Jos A; Bogers, Ad J J C; Allessie, Maurits A; de Groot, Natasja M S

2015-12-01

A new technique is demonstrated for extensive high-resolution intra-operative atrial mapping that will facilitate the localization of atrial fibrillation (AF) sources and identification of the substrate perpetuating AF. Prior to the start of extra-corporal circulation, a 8 × 24-electrode array (2-mm inter-electrode distance) is placed subsequently on all the right and left epicardial atrial sites, including Bachmann's bundle, for recording of unipolar electrograms during sinus rhythm and (induced) AF. AF is induced by high-frequency pacing at the right atrial free wall. A pacemaker wire stitched to the right atrium serves as a reference signal. The indifferent pole is connected to a steal wire fixed to subcutaneous tissue. Electrograms are recorded by a computerized mapping system and, after amplification (gain 1000), filtering (bandwidth 0.5-400 Hz), sampling (1 kHz) and analogue to digital conversion (16 bits), automatically stored on hard disk. During the mapping procedure, real-time visualization secures electrogram quality. Analysis will be performed offline. This technique was performed in 168 patients of 18 years and older, with coronary and/or structural heart disease, with or without AF, electively scheduled for cardiac surgery and a ventricular ejection fraction above 40 %. The mean duration of the entire mapping procedure including preparation time was 9 ± 2 min. Complications related to the mapping procedure during or after cardiac surgery were not observed. We introduce the first epicardial atrial mapping approach with a high resolution of ≥1728 recording sites which can be performed in a procedure time of only 9±2 mins. This mapping technique can potentially identify areas responsible for initiation and persistence of AF and hopefully can individualize both diagnosis and therapy of AF.

Continuous piecewise-linear, reduced-order electrochemical model for lithium-ion batteries in real-time applications

NASA Astrophysics Data System (ADS)

Farag, Mohammed; Fleckenstein, Matthias; Habibi, Saeid

2017-02-01

Model-order reduction and minimization of the CPU run-time while maintaining the model accuracy are critical requirements for real-time implementation of lithium-ion electrochemical battery models. In this paper, an isothermal, continuous, piecewise-linear, electrode-average model is developed by using an optimal knot placement technique. The proposed model reduces the univariate nonlinear function of the electrode's open circuit potential dependence on the state of charge to continuous piecewise regions. The parameterization experiments were chosen to provide a trade-off between extensive experimental characterization techniques and purely identifying all parameters using optimization techniques. The model is then parameterized in each continuous, piecewise-linear, region. Applying the proposed technique cuts down the CPU run-time by around 20%, compared to the reduced-order, electrode-average model. Finally, the model validation against real-time driving profiles (FTP-72, WLTP) demonstrates the ability of the model to predict the cell voltage accurately with less than 2% error.

Design and Manufacturing of Desalination System Powered by Solar Energy Using CDI Technique

NASA Astrophysics Data System (ADS)

Rostami, Mohammad Sajjad; Khashehchi, Morteza; Pipelzadeh, Ehsan

2017-11-01

Capacitive deionization (CDI) is an emerging energy efficient, low pressure and low capital intensive desalination process where ions are separated by a pure electrostatic force imposed by a small bias potential as low as 1 V That funded by an external Renewable (Solar) power supply to materials with high specific surface area. The main objective of this configuration is to separate the cation and anions on oppositely charged electrodes. One of the key parameters for commercial realization of CDI is the salt adsorption capacity of the electrodes. State-of-the-art electrode materials are based on porous activated carbon particles or carbon aerogels. Various electrode materials have been developed in the past, which have suffered from instability and lack of performance. Preliminary experimental results using carbon black, graphite powder, graphene ∖ graphite ∖ PTFE (Active ∖ Conductive ∖ binder) show that the graphene reduced via urea method is a suitable method to develop CDI electrode materials. Although some progress has been made, production of efficient and stable carbon based electrode materials for large scale desalination has not been fully realized. A new desalination technique using capacitive deionization.

Low resistivity contacts to YBa2Cu3O(7-x) superconductors

NASA Technical Reports Server (NTRS)

Hsi, Chi-Shiung; Haertling, Gene H.

1991-01-01

Silver, gold, platinum, and palladium metals were investigated as electroding materials for the YBa2Cu3O(7-x) superconductors. Painting, embedding, and melting techniques were used to apply the electrodes. Contact resistivities were determined by: (1) type of electrode; (2) firing conditions; and (3) application method. Electrodes fired for long times exhibited lower contact resistivities than those fired for short times. Low-resistivity contacts were found for silver and gold electrodes. Silver, which made good ohmic contact to the YBa2Cu3O(7-x) superconductor with low contact resistivities was found to be the best electroding material among the materials evaluated in this investigation.

Amperometric Immunosensors for screening of Polycyclic Aromatic Hydrocarbons in water

NASA Astrophysics Data System (ADS)

Ahmad, A.; Paschero, A.; Moore, E.

2011-08-01

An amperometric immunosensor with low limit detection was developed for the screening of polycyclic aromatic hydrocarbons (PAHs) in water. The system was based on detecting the specific substance using an immunological reaction by measuring the chemical responses to specific antibodies. An integrated biochip with a three electrode system was fabricated. Gold was used as the working electrode with platinum was used as the counter electrode. A modified Ag/AgCl reference electrode was employed to enhance the stability of the immunosensors. Indirect competition enzyme-linked immunosorbent assay (ELISA) was carried out within the electrode using alkaline phosphatase (AP) as the labelled-enzyme. The system shows acceptable reproducibility and good stability. The immunosensor exhibited a wide linear response to PAHs. A limit of detection for this sensor was in the range of 1 to 10 ng ml-1 in aqueous sample.

Electric ventilation: indications for and technical aspects of diaphragm pacing stimulation surgical implantation.

PubMed

Tedde, Miguel Lia; Onders, Raymond P; Teixeira, Manoel Jacobsen; Lage, Silvia Gelas; Ballester, Gerson; Brotto, Mario Wilson Iersolino; Okumura, Erica Mie; Jatene, Fabio Biscegli

2012-01-01

Patients with high cervical spinal cord injury are usually dependent on mechanical ventilation support, which, albeit life saving, is associated with complications and decreased life expectancy because of respiratory infections. Diaphragm pacing stimulation (DPS), sometimes referred to as electric ventilation, induces inhalation by stimulating the inspiratory muscles. Our objective was to highlight the indications for and some aspects of the surgical technique employed in the laparoscopic insertion of the DPS electrodes, as well as to describe five cases of tetraplegic patients submitted to the technique. Patient selection involved transcutaneous phrenic nerve studies in order to determine whether the phrenic nerves were preserved. The surgical approach was traditional laparoscopy, with four ports. The initial step was electrical mapping in order to locate the "motor points" (the points at which stimulation would cause maximal contraction of the diaphragm). If the diaphragm mapping was successful, four electrodes were implanted into the abdominal surface of the diaphragm, two on each side, to stimulate the branches of the phrenic nerve. Of the five patients, three could breathe using DPS alone for more than 24 h, one could do so for more than 6 h, and one could not do so at all. Although a longer follow-up period is needed in order to reach definitive conclusions, the initial results have been promising. At this writing, most of our patients have been able to remain ventilator-free for long periods of time.

Facile fabrication of novel silver-polypyrrole-multiwall carbon nanotubes nanocomposite for replacement of platinum in dye-sensitized solar cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafique, Shaista; Sharif, Rehana; Ghani, Sheeba

This paper demonstrates the facile synthesis of high performance silver-polypyrrole-multiwall carbon nanotubes (Ag-PPy-FMWCNTS) nanocomposites via electrodeposition method on stainless steel substrate and its application as a low cost counter electrode (CE) for the precious platinum (Pt) free DSSC. The nanocomposites were characterized by variety of techniques such as Fourier transforms infrared (FTIR), X-ray diffraction, Scanning electron microscope (SEM), cyclic voltammetry (CV) and Four probe technique respectively. The cyclic voltammetry and Tafel polymerization measurements of Ag-PPy-FMWCNTS nanocomposites CE reveal the favorable electrocatalytic activity and low charge transfer resistance R{sub ct}(2.50 Ω cm{sup 2}) for I{sub 3}{sup −}/I{sup −} redox solution. Themore » four probe studies showed the large electrical conductivity (226S cm{sup −1}) of Ag-PPy-FMWCNTS nanocomposite. The DSSC assembled with Ag-PPy-FMWCNTS nanocomposites CE display the considerable short circuit current density (13.95 mA cm{sup −2}) and acceptable solar to electrical conversion efficiency of 7.6%, which is higher to the efficiency of DSSC with thermally decomposed Pt reference electrode 7.1%. The excellent conversion efficiency, rapid charge transfer in combination with low cost and simple fabrication method of Ag-PPy-FMWCNTS nanocomposites can be exploited as an efficient and potential candidate to replace the Pt CE for large scale production of DSSC.« less

Intraoperative laryngeal electromyography in children with vocal fold immobility: a simplified technique.

PubMed

Scott, Andrew R; Chong, Peter Siao Tick; Randolph, Gregory W; Hartnick, Christopher J

2008-01-01

The primary objective of this study was to determine whether a simplified technique for intraoperative laryngeal electromyography was feasible using standard nerve integrity monitoring electrodes and audiovisual digital recording equipment. Our secondary objective was to determine if laryngeal electromyography data provided any additional information that significantly influenced patient management. Between February 2006 and February 2007, 10 children referred to our institution with vocal fold immobility underwent intraoperative laryngeal electromyography of the thyroarytenoid muscles. A retrospective chart review of these 10 patients was performed after institutional review board approval. Standard nerve integrity monitoring electrodes can be used to perform intraoperative laryngeal electromyography of the thyroarytenoid muscles in children. In 5 of 10 cases reviewed, data from laryngeal electromyography recordings meaningfully influenced the care of children with vocal fold immobility and affected clinical decision-making, sometimes altering management strategies. In the remaining 5 children, data supported clinical impressions but did not alter treatment plans. Two children with idiopathic bilateral vocal fold paralysis initially presented with a lack of electrical activity on one or both sides but went on to develop motor unit action potentials that preceded recovery of motion in both vocal folds. Our findings suggest that standard nerve monitoring equipment can be used to perform intraoperative laryngeal electromyography and that electromyographic data can assist clinicians in the management of complex patients. Additionally, there may be a role for the use of serial intraoperative measurements in predicting recovery from vocal fold paralysis in the pediatric age group.

A simultaneous multichannel monophasic action potential electrode array for in vivo epicardial repolarization mapping.

PubMed

Sahakian, A V; Peterson, M S; Shkurovich, S; Hamer, M; Votapka, T; Ji, T; Swiryn, S

2001-03-01

While the recording of extracellular monophasic action potentials (MAPs) from single epicardial or endocardial sites has been performed for over a century, we are unaware of any previous successful attempt to record MAPs simultaneously from a large number of sites in vivo. We report here the design and validation of an array of MAP electrodes which records both depolarization and repolarization simultaneously at up to 16 epicardial sites in a square array on the heart in vivo. The array consists of 16 sintered Ag-AgCl electrodes mounted in a common housing with individual suspensions allowing each electrode to exert a controlled pressure on the epicardial surface. The electrodes are arranged in a square array, with each quadrant of four having an additional recessed sintered Ag-AgCl reference electrode at its center. A saline-soaked sponge establishes ionic contact between the reference electrodes and the tissue. The array was tested on six anesthetized open-chested pigs. Simultaneous diagnostic-quality MAP recordings were obtained from up to 13 out of 16 ventricular sites. Ventricular MAPs had amplitudes of 10-40 mV with uniform morphologies and stable baselines for up to 30 min. MAP duration at 90% repolarization was measured and shown to vary as expected with cycle length during sustained pacing. The relationship between MAP duration and effective refractory period was also confirmed. The ability of the array to detect local differences in repolarization was tested in two ways. Placement of the array straddling the atrioventricular (AV) junction yielded simultaneous atrial or ventricular recordings at corresponding sites during 1:1 and 2:1 AV conduction. Localized ischemia via constriction of a coronary artery branch resulted in shortening of the repolarization phase at the ischemic, but not the nonischemic, sites. In conclusion, these results indicate that the simultaneous multichannel MAP electrode array is a viable method for in vivo epicardial repolarization mapping. The array has the potential to be expanded to increase the number of sites and spatial resolution.

Optimizing Nanoelectrode Arrays for Scalable Intracellular Electrophysiology.

PubMed

Abbott, Jeffrey; Ye, Tianyang; Ham, Donhee; Park, Hongkun

2018-03-20

Electrode technology for electrophysiology has a long history of innovation, with some decisive steps including the development of the voltage-clamp measurement technique by Hodgkin and Huxley in the 1940s and the invention of the patch clamp electrode by Neher and Sakmann in the 1970s. The high-precision intracellular recording enabled by the patch clamp electrode has since been a gold standard in studying the fundamental cellular processes underlying the electrical activities of neurons and other excitable cells. One logical next step would then be to parallelize these intracellular electrodes, since simultaneous intracellular recording from a large number of cells will benefit the study of complex neuronal networks and will increase the throughput of electrophysiological screening from basic neurobiology laboratories to the pharmaceutical industry. Patch clamp electrodes, however, are not built for parallelization; as for now, only ∼10 patch measurements in parallel are possible. It has long been envisioned that nanoscale electrodes may help meet this challenge. First, nanoscale electrodes were shown to enable intracellular access. Second, because their size scale is within the normal reach of the standard top-down fabrication, the nanoelectrodes can be scaled into a large array for parallelization. Third, such a nanoelectrode array can be monolithically integrated with complementary metal-oxide semiconductor (CMOS) electronics to facilitate the large array operation and the recording of the signals from a massive number of cells. These are some of the central ideas that have motivated the research activity into nanoelectrode electrophysiology, and these past years have seen fruitful developments. This Account aims to synthesize these findings so as to provide a useful reference. Summing up from the recent studies, we will first elucidate the morphology and associated electrical properties of the interface between a nanoelectrode and a cellular membrane, clarifying how the nanoelectrode attains intracellular access. This understanding will be translated into a circuit model for the nanobio interface, which we will then use to lay out the strategies for improving the interface. The intracellular interface of the nanoelectrode is currently inferior to that of the patch clamp electrode; reaching this benchmark will be an exciting challenge that involves optimization of electrode geometries, materials, chemical modifications, electroporation protocols, and recording/stimulation electronics, as we describe in the Account. Another important theme of this Account, beyond the optimization of the individual nanoelectrode-cell interface, is the scalability of the nanoscale electrodes. We will discuss this theme using a recent development from our groups as an example, where an array of ca. 1000 nanoelectrode pixels fabricated on a CMOS integrated circuit chip performs parallel intracellular recording from a few hundreds of cardiomyocytes, which marks a new milestone in electrophysiology.

A fine pointed glucose oxidase immobilized electrode for low-invasive amperometric glucose monitoring.

PubMed

Li, Jiang; Koinkar, Pankaj; Fuchiwaki, Yusuke; Yasuzawa, Mikito

2016-12-15

A low invasive type glucose sensor, which has a sensing region at the tip of a fine pointed electrode, was developed for continuous glucose monitoring. Platinum-iridium alloy electrode with a surface area of 0.045mm(2) was settled at the middle of pointed PEEK (Polyetheretherketone) tubing and was employed as sensing electrode. Electrodeposition of glucose oxidase in the presence of surfactant, Triton X-100, was performed for high-density enzyme immobilization followed by the electropolymerization of o-phenylenediamine for the formation of functional entrapping and permselective polymer membrane. Ag/AgCl film was coated on the surface of PEEK tubing as reference electrode. Amperometric responses of the prepared sensors to glucose were measured at a potential of 0.60V (vs. Ag/AgCl). The prepared electrode showed the sensitivity of 2.55μA/cm(2) mM with high linearity of 0.9986, within the glucose concentration range up to 21mM. The detection limit (S/N=3) was determined to be 0.11mM. The glucose sensor properties were evaluated in phosphate buffer solution and in vivo monitoring by the implantation of the sensors in rabbit, while conventional needle type sensors as a reference were used. The results showed that change in output current of the proposed sensor fluctuated similar with one in output current of the conventional needle type sensors, which was also in similar accordance with actual blood sugar level measured by commercially glucose meter. One-point calibration method was used to calibrate the sensor output current. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced control of electrochemical response in metallic materials in neural stimulation electrode applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, K.G.; Steen, W.M.; Manna, I.

New means have been investigated for the production of electrode devices (stimulation electrodes) which could be implanted in the human body in order to control pain, activate paralysed limbs or provide electrode arrays for cochlear implants for the deaf or for the relief of tinitus. To achieve this ion implantation and laser materials processing techniques were employed. Ir was ion implanted in Ti-6Al-4V alloy and the surface subsequently enriched in the noble metal by dissolution in sulphuric acid. For laser materials processing techniques, investigation has been carried out on the laser cladding and laser alloying of Ir in Ti wire.more » A particular aim has been the determination of conditions required for the formation of a two phase Ir, Ir-rich, and Ti-rich microstructure which would enable subsequent removal of the non-noble phase to leave a highly porous noble metal with large real surface area and hence improved charge carrying capacity compared with conventional non porous electrodes. Evaluation of the materials produced has been carried out using repetitive cyclic voltammetry, amongst other techniques. For laser alloyed Ir on Ti wire, it has been found that differences in the melting point and density of the materials makes control of the cladding or alloying process difficult. Investigation of laser process parameters for the control of alloying and cladding in this system was carried out and a set of conditions for the successful production of two phase Ir-rich and Ti-rich components in a coating layer with strong metallurgical bonding to the Ti alloy substrate was derived. The laser processed material displays excellent potential for further development in providing stimulation electrodes with the current carrying capacity of Ir but in a form which is malleable and hence capable of formation into smaller electrodes with improved spatial resolution compared with presently employed electrodes.« less

Optimum electrode configuration selection for electrical resistance change based damage detection in composites using an effective independence measure

NASA Astrophysics Data System (ADS)

Escalona, Luis; Díaz-Montiel, Paulina; Venkataraman, Satchi

2016-04-01

Laminated carbon fiber reinforced polymer (CFRP) composite materials are increasingly used in aerospace structures due to their superior mechanical properties and reduced weight. Assessing the health and integrity of these structures requires non-destructive evaluation (NDE) techniques to detect and measure interlaminar delamination and intralaminar matrix cracking damage. The electrical resistance change (ERC) based NDE technique uses the inherent changes in conductive properties of the composite to characterize internal damage. Several works that have explored the ERC technique have been limited to thin cross-ply laminates with simple linear or circular electrode arrangements. This paper investigates a method of optimum selection of electrode configurations for delamination detection in thick cross-ply laminates using ERC. Inverse identification of damage requires numerical optimization of the measured response with a model predicted response. Here, the electrical voltage field in the CFRP composite laminate is calculated using finite element analysis (FEA) models for different specified delamination size and locations, and location of ground and current electrodes. Reducing the number of sensor locations and measurements is needed to reduce hardware requirements, and computational effort needed for inverse identification. This paper explores the use of effective independence (EI) measure originally proposed for sensor location optimization in experimental vibration modal analysis. The EI measure is used for selecting the minimum set of resistance measurements among all possible combinations of selecting a pair of electrodes among the n electrodes. To enable use of EI to ERC required, it is proposed in this research a singular value decomposition SVD to obtain a spectral representation of the resistance measurements in the laminate. The effectiveness of EI measure in eliminating redundant electrode pairs is demonstrated by performing inverse identification of damage using the full set of resistance measurements and the reduced set of measurements. The investigation shows that the EI measure is effective for optimally selecting the electrode pairs needed for resistance measurements in ERC based damage detection.

Fabrication of a Miniature Multi-Parameter Sensor Chip for Water Quality Assessment.

PubMed

Zhou, Bo; Bian, Chao; Tong, Jianhua; Xia, Shanhong

2017-01-14

Water contamination is a main inducement of human diseases. It is an important step to monitor the water quality in the water distribution system. Due to the features of large size, high cost, and complicated structure of traditional water determination sensors and devices, it is difficult to realize real-time water monitoring on a large scale. In this paper, we present a multi-parameter sensor chip, which is miniature, low-cost, and robust, to detect the pH, conductivity, and temperature of water simultaneously. The sensor chip was fabricated using micro-electro-mechanical system (MEMS) techniques. Iridium oxide film was electrodeposited as the pH-sensing material. The atomic ratio of Ir(III) to Ir(IV) is about 1.38 according to the X-ray photoelectron spectroscopy (XPS) analysis. The pH sensing electrode showed super-Nernstian response (-67.60 mV/pH) and good linearity (R² = 0.9997), in the range of pH 2.22 to pH 11.81. KCl-agar and epoxy were used as the electrolyte layer and liquid junction for the solid-state reference electrode, respectively, and its potential stability in deionized water was 56 h. The conductivity cell exhibited a linear determination range from 21.43 μ S / cm to 1.99 mS / cm , and the electrode constant was 1.566 cm -1 . Sensitivity of the temperature sensor was 5.46 Ω / ° C . The results indicate that the developed sensor chip has potential application in water quality measurements.

Vertically grown zinc oxide nanorods functionalized with ferric oxide for in vivo and non-enzymatic glucose detection

NASA Astrophysics Data System (ADS)

Marie, Mohammed; Manoharan, Anishkumar; Kuchuk, Andrian; Ang, Simon; Manasreh, M. O.

2018-03-01

An enzyme-free glucose sensor based on vertically grown zinc oxide nanorods (NRs) functionalized with ferric oxide (Fe2O3) is investigated. The well-aligned and high density ZnO NRs were synthesized on an FTO/glass substrate by a sol-gel and hydrothermal growth method. A dip-coating technique was utilized to modify the surface of the as-grown ZnO NRs with Fe2O3. The immobilized surface was coated with a layer of nafion membrane. The fabricated glucose sensor was characterized amperometrically at room temperature using three electrodes stationed in the phosphate buffer solution, where ZnO NRs/Fe2O3/nafion membrane was the sensing or working electrode, and platinum plate and silver/silver chloride were used as the counter and reference electrodes, respectively. The proposed non-enzymatic and modified glucose sensor exhibited a high sensitivity in the order of 0.052 μA cm-2 (mg/dL)-1, a lower detection limit of around 0.95 mmol L-1, a sharp and fast response time of ˜1 s, and a linear response to changes in glucose concentrations from 100-400 mg dL-1. The linear amperometric response of the sensor covers the physiological and clinical interest of glucose levels for diabetic patients. The device continues to function accurately after multiple measurements with a good reproducibility. The proposed glucose sensor is expected to be used clinically for in vivo monitoring of glucose.

Simultaneous determination of potassium and total fluoride in toothpastes using a SIA system with two potentiometric detectors.

PubMed

Pérez-Olmos, R; Soto, J C; Zárate, N; Díez, I

2008-05-12

A sequential injection analysis (SIA) system has been developed for the first time to quantify potassium and total fluoride in toothpastes and gels used to prevent both dentinal hypersensitivity and dental caries. To enable this simultaneous determination, potentiometric detection, using a conventional fluoride electrode and a tubular potassium selective electrode, formed by a PVC membrane containing valinomycin as ionophore, was carried out. A manifold that uses a three-way solenoid valve was designed. The former under binary sampling conditions, provides reproducible mixing ratios of two solutions. This fact facilitates that the system automatically generates, on-line, the calibration curves required by the analytical procedure. The calibration ranged from 1.0 x 10(-4) to 1.0 x 10(-3) mol L(-1) for both potassium and total fluoride determinations. The R.S.D. (11 readings) resulted to be less than 1.5% for both determinations. Off-line studies related to the dissolution of the solid samples, the transformation of monofluorophosphate in fluoride, the elimination of organic matrix interference onto the plastic membrane of the potassium electrode, and the selection of the most adequate TISAB solution for fluoride determination, were also considered. A sampling rate of 18 samples h(-1) for both determinations was attained, their precisions and accuracies being statistically indistinguishable from those achieved by atomic emission spectroscopy (for potassium determination) and by a conventional batch potentiometry (for total fluoride determination) adopted as reference techniques.

An equivalent network representation of a clamped bimorph piezoelectric micromachined ultrasonic transducer with circular and annular electrodes using matrix manipulation techniques.

PubMed

Sammoura, Firas; Smyth, Katherine; Kim, Sang-Gook

2013-09-01

An electric circuit model for a clamped circular bimorph piezoelectric micromachined ultrasonic transducer (pMUT) was developed for the first time. The pMUT consisted of two piezoelectric layers sandwiched between three thin electrodes. The top and bottom electrodes were separated into central and annular electrodes by a small gap. While the middle electrode was grounded, the central and annular electrodes were biased with two independent voltage sources. The strain mismatch between the piezoelectric layers caused the plate to vibrate and transmit a pressure wave, whereas the received echo generated electric charges resulting from plate deformation. The clamped pMUT plate was separated into a circular and an annular plate, and the respective electromechanical transformation matrices were derived. The force and velocity vectors were properly selected using Hamilton's principle and the necessary boundary conditions were invoked. The electromechanical transformation matrix for the clamped circular pMUT was deduced using simple matrix manipulation techniques. The pMUT performance under three biasing schemes was elaborated: 1) central electrode only, 2) central and annular electrodes with voltages of the same magnitude and polarity, and 3) central and annular electrodes with voltages of the same magnitude and opposite polarity. The circuit parameters of the pMUT were extracted for each biasing scheme, including the transformer ratio, the clamped electric impedance, and the open-circuit mechanical impedance. Each pMUT scheme was characterized under different acoustic loadings using the theoretically developed model, which was verified with finite element modeling (FEM) simulation. The electrode size was optimized to maximize the electromechanical transformer ratio. As such, the developed model could provide more insight into the design, optimization, and characterization of pMUTs and allow for performance comparison with their cMUT counterparts.

Insertion characteristics and placement of the Mid-Scala electrode array in human temporal bones using detailed cone beam computed tomography.

PubMed

Dietz, Aarno; Gazibegovic, Dzemal; Tervaniemi, Jyrki; Vartiainen, Veli-Matti; Löppönen, Heikki

2016-12-01

The aim of this study was to evaluate the insertion results and placement of the new Advanced Bionics HiFocus Mid-Scala (HFms) electrode array, inserted through the round window membrane, in eight fresh human temporal bones using cone beam computed tomography (CBCT). Pre- and post-insertion CBCT scans were registered to create a 3D reconstruction of the cochlea with the array inserted. With an image fusion technique both the bony edges of the cochlea and the electrode array in situ could accurately be determined, thus enabling to identify the exact position of the electrode array within the scala tympani. Vertical and horizontal scalar location was measured at four points along the cochlea base at an angular insertion depth of 90°, 180° and 270° and at electrode 16, the most basal electrode. Smooth insertion through the round window membrane was possible in all temporal bones. The imaging results showed that there were no dislocations from the scala tympani into the scala vestibule. The HFms electrode was positioned in the middle of the scala along the whole electrode array in three out of the eight bones and in 62 % of the individual locations measured along the base of the cochlea. In only one cochlea a close proximity of the electrode with the basilar membrane was observed, indicating possible contact with the basilar membrane. The results and assessments presented in this study appear to be highly accurate. Although a further validation including histopathology is needed, the image fusion technique described in this study represents currently the most accurate method for intracochlear electrode assessment obtainable with CBCT.

Frequency response of electrochemical cells

NASA Technical Reports Server (NTRS)

Thomas, Daniel L.

1989-01-01

Impedance concepts can be applied to the analysis of battery electrodes, yielding information about the structure of the electrode and the processes occurring in the electrode. Structural parameters such as the specific area (surface area per gram of electrode) can be estimated. Electrode variables such as surface overpotential, ohmic losses, and diffusion limitations may be studied. Nickel and cadmium electrodes were studied by measuring the ac impedance as a function of frequency, and the specific areas that were determined were well within the range of specific areas determined from BET measurements. Impedance spectra were measured for the nickel and cadmium electrodes, and for a 20 A-hr NiCd battery as functions of the state of charge. More work is needed to determine the feasibility of using frequency response as a nondestructive testing technique for batteries.

Active Laplacian electrode for the data-acquisition system of EHG

NASA Astrophysics Data System (ADS)

Li, G.; Wang, Y.; Lin, L.; Jiang, W.; Wang, L. L.; C-Y Lu, Stephen; Besio, Walter G.

2005-01-01

EHG (electrohysterogram) is the recording of uterine electromyogram with external electrodes located on the abdomen of pregnant woman. Derived from the electrical activity generated at the muscle fiber lever, it provides complementary information from the muscle, and appears to be a very promising technique for clinical or physiologic investigation of uterine activity, compared with current monitoring which can't give us complementary phase information of uterine activity. In this article we have shown the disadvantages of the conventional electrodes for EHG data-acquisition system and put forward a new type of electrode that is called active Laplacian electrode. It integrates concentric rings electrode with a bioelectricity preamplifier and is capable of acquiring localized information. We can localise the EHG signals source more easily by using this new electrode.

Laser patterning of platinum electrodes for safe neurostimulation

NASA Astrophysics Data System (ADS)

Green, R. A.; Matteucci, P. B.; Dodds, C. W. D.; Palmer, J.; Dueck, W. F.; Hassarati, R. T.; Byrnes-Preston, P. J.; Lovell, N. H.; Suaning, G. J.

2014-10-01

Objective. Laser surface modification of platinum (Pt) electrodes was investigated for use in neuroprosthetics. Surface modification was applied to increase the surface area of the electrode and improve its ability to transfer charge within safe electrochemical stimulation limits. Approach. Electrode arrays were laser micromachined to produce Pt electrodes with smooth surfaces, which were then modified with four laser patterning techniques to produce surface structures which were nanosecond patterned, square profile, triangular profile and roughened on the micron scale through structured laser interference patterning (SLIP). Improvements in charge transfer were shown through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and biphasic stimulation at clinically relevant levels. A new method was investigated and validated which enabled the assessment of in vivo electrochemically safe charge injection limits. Main results. All of the modified surfaces provided electrical advantage over the smooth Pt. The SLIP surface provided the greatest benefit both in vitro and in vivo, and this surface was the only type which had injection limits above the threshold for neural stimulation, at a level shown to produce a response in the feline visual cortex when using an electrode array implanted in the suprachoroidal space of the eye. This surface was found to be stable when stimulated with more than 150 million clinically relevant pulses in physiological saline. Significance. Critical to the assessment of implant devices is accurate determination of safe usage limits in an in vivo environment. Laser patterning, in particular SLIP, is a superior technique for improving the performance of implant electrodes without altering the interfacial electrode chemistry through coating. Future work will require chronic in vivo assessment of these electrode patterns.

A new biosensor for noninvasive determination of fetal RHD status in maternal blood of RhD negative pregnant women.

PubMed

Dündar Yenilmez, Ebru; Kökbaş, Umut; Kartlaşmış, Kezban; Kayrın, Levent; Tuli, Abdullah

2018-01-01

Prenatal detection of the fetal RHD status can be useful in the management of RhD incompatibility to identify fetuses at risk of hemolytic disease. Hemolytic disease causes morbidity and mortality of the fetus in the neonatal period. The routine use of antenatal and postnatal anti-D prophylaxis has reduced the incidence of hemolytic disease of the fetus and newborn. This study describe the detection of fetal RhD antigens in blood of RhD negative pregnant women using a nanopolymer coated electrochemical biosensor for medical diagnosis. Cell free fetal DNA in maternal plasma was also used to genotyping fetal RHD status using multiplex real-time PCR. Twenty-six RhD negative pregnant women in different gestational ages were included in the study. RhD positive fetal antibodies detected with a developed biosensor in maternal blood of RhD negative mothers. The electrochemical measurements were performed on a PalmSens potentiostat, and corundum ceramic based screen printed gold electrode combined with the reference Ag/AgCl electrode, and the auxiliary Au/Pd (98/2%) electrode. Fetal RHD genotyping performed using fluorescence-based multiplex real-time PCR exons 5 and 7 of the RHD gene. The fetal RHD status of 26 RhD negative cases were detected 21 as RhD positive and 5 as RhD negative with electrochemical biosensor. Fetal RHD status confirmed with extracted fetal DNA in maternal plasma using multiplex real-time PCR RHD genotyping and by serological test after delivery. The new method for fetal RhD detection in early pregnancy is useful and can be carry out rapidly in clinical diagnosis. Using automated biosensors are reproducible, quick and results can be generated within a few minutes compared to noninvasive fetal RHD genotyping from maternal plasma with real-time PCR-based techniques. We suggest the biosensor techniques could become an alternative part of fetal RHD genotyping from maternal plasma as a prenatal screening in the management of RhD incompatibility.

Composite nuclear fuel fabrication methodology for gas fast reactors

NASA Astrophysics Data System (ADS)

Vasudevamurthy, Gokul

An advanced fuel form for use in Gas Fast Reactors (GFR) was investigated. Criteria for the fuel includes operation at high temperature (˜1400°C) and high burnup (˜150 MWD/MTHM) with effective retention of fission products even during transient temperatures exceeding 1600°C. The GFR fuel is expected to contain up to 20% transuranics for a closed fuel cycle. Earlier evaluations of reference fuels for the GFR have included ceramic-ceramic (cercer) dispersion type composite fuels of mixed carbide or nitride microspheres coated with SiC in a SiC matrix. Studies have indicated that ZrC is a potential replacement for SiC on account of its higher melting point, increased fission product corrosion resistance and better chemical stability. The present work investigated natural uranium carbide microspheres in a ZrC matrix instead of SiC. Known issues of minor actinide volatility during traditional fabrication procedures necessitated the investigation of still high temperature but more rapid fabrication techniques to minimize these anticipated losses. In this regard, fabrication of ZrC matrix by combustion synthesis from zirconium and graphite powders was studied. Criteria were established to obtain sufficient matrix density with UC microsphere volume fractions up to 30%. Tests involving production of microspheres by spark erosion method (similar to electrodischarge machining) showed the inability of the method to produce UC microspheres in the desired range of 300 to 1200 mum. A rotating electrode device was developed using a minimum current of 80A and rotating at speeds up to 1500 rpm to fabricate microspheres between 355 and 1200 mum. Using the ZrC process knowledge, UC electrodes were fabricated and studied for use in the rotating electrode device to produce UC microspheres. Fabrication of the cercer composite form was studied using microsphere volume fractions of 10%, 20%, and 30%. The macrostructure of the composite and individual components at various stages were characterized to understand the required fabrication techniques and at the same time meet the necessary GFR fuel characteristics.

On-chip collection of particles and cells by AC electroosmotic pumping and dielectrophoresis using asymmetric microelectrodes.

PubMed

Melvin, Elizabeth M; Moore, Brandon R; Gilchrist, Kristin H; Grego, Sonia; Velev, Orlin D

2011-09-01

The recent development of microfluidic "lab on a chip" devices requiring sample sizes <100 μL has given rise to the need to concentrate dilute samples and trap analytes, especially for surface-based detection techniques. We demonstrate a particle collection device capable of concentrating micron-sized particles in a predetermined area by combining AC electroosmosis (ACEO) and dielectrophoresis (DEP). The planar asymmetric electrode pattern uses ACEO pumping to induce equal, quadrilateral flow directed towards a stagnant region in the center of the device. A number of system parameters affecting particle collection efficiency were investigated including electrode and gap width, chamber height, applied potential and frequency, and number of repeating electrode pairs and electrode geometry. The robustness of the on-chip collection design was evaluated against varying electrolyte concentrations, particle types, and particle sizes. These devices are amenable to integration with a variety of detection techniques such as optical evanescent waveguide sensing.

Vacuum-free laminated top electrode with conductive tapes for scalable manufacturing of efficient perovskite solar cells

DOE PAGES

Shao, Yuchuan; Wang, Qi; Dong, Qingfeng; ...

2015-06-25

The efficiency of organometal trihalide perovskites (OTP) solar cells have reached that parity of single crystal silicon, and its nature abundant raw material and solution-process capability promise a bright future for commercialization. However, the vacuum based techniques for metal electrode deposition and additional encapsulation layer increase the cost of the perovskite solar cells dramatically and impede their commercialization process. Here, we report a vacuum-free low temperature lamination technique to fabricate the top electrode by commercial conductive tapes (C-tape). The simple fabrication method yields good quality contact and high efficiency device of 12.7%. The C-tapes also encapsulated the devices effectively, resultingmore » in greatly improved device stability. As a result, the combination of lamination of electrodes and encapsulation layers into a single step significantly reduce the cost of device fabrication.« less

Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements

NASA Astrophysics Data System (ADS)

Almuhammadi, Khaled; Selvakumaran, Lakshmi; Alfano, Marco; Yang, Yang; Bera, Tushar Kanti; Lubineau, Gilles

2015-12-01

Electrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.

In-line monitoring of Li-ion battery electrode porosity and areal loading using active thermal scanning - modeling and initial experiment

DOE PAGES

Rupnowski, Przemyslaw; Ulsh, Michael J.; Sopori, Bhushan; ...

2017-08-18

This work focuses on a new technique called active thermal scanning for in-line monitoring of porosity and areal loading of Li-ion battery electrodes. In this technique a moving battery electrode is subjected to thermal excitation and the induced temperature rise is monitored using an infra-red camera. Static and dynamic experiments with speeds up to 1.5 m min -1 are performed on both cathodes and anodes and a combined micro- and macro-scale finite element thermal model of the system is developed. It is shown experimentally and through simulations that during thermal scanning the temperature profile generated in an electrode depends onmore » both coating porosity (or area loading) and thickness. Here, it is concluded that by inverting this relation the porosity (or areal loading) can be determined, if thermal response and thickness are simultaneously measured.« less

In-line monitoring of Li-ion battery electrode porosity and areal loading using active thermal scanning - modeling and initial experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rupnowski, Przemyslaw; Ulsh, Michael J.; Sopori, Bhushan

This work focuses on a new technique called active thermal scanning for in-line monitoring of porosity and areal loading of Li-ion battery electrodes. In this technique a moving battery electrode is subjected to thermal excitation and the induced temperature rise is monitored using an infra-red camera. Static and dynamic experiments with speeds up to 1.5 m min -1 are performed on both cathodes and anodes and a combined micro- and macro-scale finite element thermal model of the system is developed. It is shown experimentally and through simulations that during thermal scanning the temperature profile generated in an electrode depends onmore » both coating porosity (or area loading) and thickness. Here, it is concluded that by inverting this relation the porosity (or areal loading) can be determined, if thermal response and thickness are simultaneously measured.« less

In-line monitoring of Li-ion battery electrode porosity and areal loading using active thermal scanning - modeling and initial experiment

NASA Astrophysics Data System (ADS)

Rupnowski, Przemyslaw; Ulsh, Michael; Sopori, Bhushan; Green, Brian G.; Wood, David L.; Li, Jianlin; Sheng, Yangping

2018-01-01

This work focuses on a new technique called active thermal scanning for in-line monitoring of porosity and areal loading of Li-ion battery electrodes. In this technique a moving battery electrode is subjected to thermal excitation and the induced temperature rise is monitored using an infra-red camera. Static and dynamic experiments with speeds up to 1.5 m min-1 are performed on both cathodes and anodes and a combined micro- and macro-scale finite element thermal model of the system is developed. It is shown experimentally and through simulations that during thermal scanning the temperature profile generated in an electrode depends on both coating porosity (or area loading) and thickness. It is concluded that by inverting this relation the porosity (or areal loading) can be determined, if thermal response and thickness are simultaneously measured.

Wearable polyimide-PDMS electrodes for intrabody communication

NASA Astrophysics Data System (ADS)

Moon, Jin-Hee; Baek, Dong Hyun; Choi, Yoon Young; Lee, Kwang Ho; Kim, Hee Chan; Lee, Sang-Hoon

2010-02-01

In this paper, we introduce a novel wearable electrode for an intra-body area network (I-BAN) by employing the advantages of polyimide (PI) which is a well-known substrate material for flexible electrodes and polydimethylsiloxane (PDMS) which is a biocompatible and representative soft-lithography adaptable material. Electrodes were patterned onto thin and flexible PI substrates and encapsulated in PDMS to enhance skin compatibility. For this purpose, we developed an electrode fabrication process on thin PI substrates and a PDMS encapsulation technique by bonding two PDMS layers on the front and back surfaces of the PI electrode. The mechanical property and communication performance of electrodes were characterized through spectrum analysis to optimize the role as an I-BAN electrode. Skin-compatibility and cyto-toxicity tests using human mesenchymal stem cells (hMSCs) were carried out to demonstrate the non-toxicity of the electrode after continuous wearing. Sinusoidal signals of 45 MHz were successfully transmitted with high fidelity between electrodes separated by 30 cm.

A multi-pad electrode based functional electrical stimulation system for restoration of grasp

PubMed Central

2012-01-01

Background Functional electrical stimulation (FES) applied via transcutaneous electrodes is a common rehabilitation technique for assisting grasp in patients with central nervous system lesions. To improve the stimulation effectiveness of conventional FES, we introduce multi-pad electrodes and a new stimulation paradigm. Methods The new FES system comprises an electrode composed of small pads that can be activated individually. This electrode allows the targeting of motoneurons that activate synergistic muscles and produce a functional movement. The new stimulation paradigm allows asynchronous activation of motoneurons and provides controlled spatial distribution of the electrical charge that is delivered to the motoneurons. We developed an automated technique for the determination of the preferred electrode based on a cost function that considers the required movement of the fingers and the stabilization of the wrist joint. The data used within the cost function come from a sensorized garment that is easy to implement and does not require calibration. The design of the system also includes the possibility for fine-tuning and adaptation with a manually controllable interface. Results The device was tested on three stroke patients. The results show that the multi-pad electrodes provide the desired level of selectivity and can be used for generating a functional grasp. The results also show that the procedure, when performed on a specific user, results in the preferred electrode configuration characteristics for that patient. The findings from this study are of importance for the application of transcutaneous stimulation in the clinical and home environments. PMID:23009589

Indirect determination of sulfite using a polyphenol oxidase biosensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film.

PubMed

Sartori, Elen Romão; Vicentini, Fernando Campanhã; Fatibello-Filho, Orlando

2011-12-15

The modification of a glassy carbon electrode with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film for the development of a biosensor is proposed. This approach provides an efficient method used to immobilize polyphenol oxidase (PPO) obtained from the crude extract of sweet potato (Ipomoea batatas (L.) Lam.). The principle of the analytical method is based on the inhibitory effect of sulfite on the activity of PPO, in the reduction reaction of o-quinone to catechol and/or the reaction of o-quinone with sulfite. Under the optimum experimental conditions using the differential pulse voltammetry technique, the analytical curve obtained was linear in the concentration of sulfite in the range from 0.5 to 22 μmol L(-1) with a detection limit of 0.4 μmol L(-1). The biosensor was applied for the determination of sulfite in white and red wine samples with results in close agreement with those results obtained using a reference iodometric method (at a 95% confidence level). Copyright © 2011 Elsevier B.V. All rights reserved.

Preparation and Characterization of Cu-Ga-Se Thin Films Synthesized by Electrodeposition: Effect of Complexing Agent and Supporting Electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, John A; Deutsch, Todd G; Fernandez, A. M.

CuGaSe2 (CGS) is a semiconductor that has potential use as a photo electrode for solar water splitting. Its wide band gap and high absorption coefficient make it an ideal candidate for the top absorber in tandem structures. CGS can be synthesized by several techniques, being electrodeposition the most advantageous from a technical standpoint. Many reports show that electrodeposition of these films for producing the desired precursor atomic composition can be aided by using a complexing agent. However, the use of supporting electrolyte and the type of the electrolyte to improve the atomic composition in the films has never been reported.more » Using cyclic voltammetry, with complexing agents and deposition potentials between -0.5 and -0.9 V vs. Ag/AgCl reference electrode atomic ratios close to the ideal values ([Cu]/[Ga] = 1 and [Se]/[Cu + Ga] = 1), based on atomic composition and morphology analysis are reported in this work. From the X-ray diffraction (XRD), the as-deposited films exhibit poor crystallinity; however, the XRD patterns evidence the formation CuGaSe2 after annealing of the samples.« less

Transcranial direct current stimulation in obsessive-compulsive disorder: emerging clinical evidence and considerations for optimal montage of electrodes.

PubMed

Senço, Natasha M; Huang, Yu; D'Urso, Giordano; Parra, Lucas C; Bikson, Marom; Mantovani, Antonio; Shavitt, Roseli G; Hoexter, Marcelo Q; Miguel, Eurípedes C; Brunoni, André R

2015-07-01

Neuromodulation techniques for obsessive-compulsive disorder (OCD) treatment have expanded with greater understanding of the brain circuits involved. Transcranial direct current stimulation (tDCS) might be a potential new treatment for OCD, although the optimal montage is unclear. To perform a systematic review on meta-analyses of repetitive transcranianal magnetic stimulation (rTMS) and deep brain stimulation (DBS) trials for OCD, aiming to identify brain stimulation targets for future tDCS trials and to support the empirical evidence with computer head modeling analysis. Systematic reviews of rTMS and DBS trials on OCD in Pubmed/MEDLINE were searched. For the tDCS computational analysis, we employed head models with the goal of optimally targeting current delivery to structures of interest. Only three references matched our eligibility criteria. We simulated four different electrodes montages and analyzed current direction and intensity. Although DBS, rTMS and tDCS are not directly comparable and our theoretical model, based on DBS and rTMS targets, needs empirical validation, we found that the tDCS montage with the cathode over the pre-supplementary motor area and extra-cephalic anode seems to activate most of the areas related to OCD.

Facile fabrication of hollow mesosphere of crystalline SnO2 nanoparticles and synthesis of SnO2@SWCNTs@Reduced Graphene Oxide nanocomposite as efficient Pt-Free counter electrode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Khan, Muhammad Wasim; Yao, Jixin; Zhang, Kang; Zuo, Xueqin; Yang, Qun; Tang, Huaibao; Ur Rehman, Khalid Mehmood; Li, Guang; Wu, Mingzai; Zhu, Kerong; Zhang, Haijun

2018-06-01

In this research, SnO2@SWCNTs@Reduced Graphene Oxide based nanocomposite was synthesized by a one step hydrothermal method and reported new cost effective platinum-free counter-electrodes (CEs) in dye-sensitized solar cells (DSSCs). The CEs were formed by using the nanocomposites with the help of a pipette using a doctor-blade technique. The efficiency of this nanocomposite revealed significant elctrocatalytic properties upon falling the triiodide, possessing to synergistic effect of SnO2 nano particles and improved conductivity when SWCNTs dispersed on graphene sheet. Therefore, the power conversion efficiency (PCE) of prepared SnO2@SWCNTs@RGO nanocomposite CE attained of (6.1%) in DSSCs which is equivalent to the value (6.2%) which attained to the value (6.2%) with pure Pt CE as a reference. SnO2@SWCNTs@RGO nanocomposite CEs give more stable catalytic activities for triiodide reduction than SnO2 and SWCNTs CEs in the cyclic voltammetry (CV) analysis. Furthermore, to the subsistence of graphene oxide, the nanocomposite acquired both higher stability and efficiency in the nanocomposite.

Validated electrochemical and chromatographic quantifications of some antibiotic residues in pharmaceutical industrial waste water.

PubMed

Ibrahim, Heba K; Abdel-Moety, Mona M; Abdel-Gawad, Sherif A; Al-Ghobashy, Medhat A; Kawy, Mohamed Abdel

2017-03-01

Realistic implementation of ion selective electrodes (ISEs) into environmental monitoring programs has always been a challenging task. This could be largely attributed to difficulties in validation of ISE assay results. In this study, the electrochemical response of amoxicillin trihydrate (AMX), ciprofloxacin hydrochloride (CPLX), trimethoprim (TMP), and norfloxacin (NFLX) was studied by the fabrication of sensitive membrane electrodes belonging to two types of ISEs, which are polyvinyl chloride (PVC) membrane electrodes and glassy carbon (GC) electrodes. Linear response for the membrane electrodes was in the concentration range of 10 -5 -10 -2  mol/L. For the PVC membrane electrodes, Nernstian slopes of 55.1, 56.5, 56.5, and 54.0 mV/decade were achieved over a pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. On the other hand, for GC electrodes, Nernstian slopes of 59.1, 58.2, 57.0, and 58.2 mV/decade were achieved over pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. In addition to assay validation to international industry standards, the fabricated electrodes were also cross-validated relative to conventional separation techniques; high performance liquid chromatography (HPLC), and thin layer chromatography (TLC)-densitometry. The HPLC assay was applied in concentration range of 0.5-10.0 μg/mL, for all target analytes. The TLC-densitometry was adopted over a concentration range of 0.3-1.0 μg/band, for AMX, and 0.1-0.9 μg/band, for CPLX, NFLX, and TMP. The proposed techniques were successfully applied for quantification of the selected drugs either in pure form or waste water samples obtained from pharmaceutical plants. The actual waste water samples were subjected to solid phase extraction (SPE) for pretreatment prior to the application of chromatographic techniques (HPLC and TLC-densitometry). On the other hand, the fabricated electrodes were successfully applied for quantification of the antibiotic residues in actual waste water samples without any pretreatment. This finding assures the suitability of the fabricated ISEs for environmental analysis.

Large-Area Cross-Aligned Silver Nanowire Electrodes for Flexible, Transparent, and Force-Sensitive Mechanochromic Touch Screens.

PubMed

Cho, Seungse; Kang, Saewon; Pandya, Ashish; Shanker, Ravi; Khan, Ziyauddin; Lee, Youngsu; Park, Jonghwa; Craig, Stephen L; Ko, Hyunhyub

2017-04-25

Silver nanowire (AgNW) networks are considered to be promising structures for use as flexible transparent electrodes for various optoelectronic devices. One important application of AgNW transparent electrodes is the flexible touch screens. However, the performances of flexible touch screens are still limited by the large surface roughness and low electrical to optical conductivity ratio of random network AgNW electrodes. In addition, although the perception of writing force on the touch screen enables a variety of different functions, the current technology still relies on the complicated capacitive force touch sensors. This paper demonstrates a simple and high-throughput bar-coating assembly technique for the fabrication of large-area (>20 × 20 cm 2 ), highly cross-aligned AgNW networks for transparent electrodes with the sheet resistance of 21.0 Ω sq -1 at 95.0% of optical transmittance, which compares favorably with that of random AgNW networks (sheet resistance of 21.0 Ω sq -1 at 90.4% of optical transmittance). As a proof of concept demonstration, we fabricate flexible, transparent, and force-sensitive touch screens using cross-aligned AgNW electrodes integrated with mechanochromic spiropyran-polydimethylsiloxane composite film. Our force-sensitive touch screens enable the precise monitoring of dynamic writings, tracing and drawing of underneath pictures, and perception of handwriting patterns with locally different writing forces. The suggested technique provides a robust and powerful platform for the controllable assembly of nanowires beyond the scale of conventional fabrication techniques, which can find diverse applications in multifunctional flexible electronic and optoelectronic devices.

MRI-Guided Regional Personalized Electrical Stimulation in Multisession and Home Treatments

PubMed Central

Cancelli, Andrea; Cottone, Carlo; Giordani, Alessandro; Asta, Giampiero; Lupoi, Domenico; Pizzella, Vittorio; Tecchio, Franca

2018-01-01

The shape and position of the electrodes is a key factor for the efficacy of transcranial electrical stimulations (tES). We have recently introduced the Regional Personalized Electrode (RePE), a tES electrode fitting the personal cortical folding, that has been able to differentiate the stimulation of close by regions, in particular the primary sensory (S1) and motor (M1) cortices, and to personalize tES onto such an extended cortical district. However, neuronavigation on individual brain was compulsory for the correct montage. Here, we aimed at developing and testing a neuronavigation-free procedure for easy and quick positioning RePE, enabling multisession RePE-tES at home. We used off-line individual MRI to shape RePE via an ad-hoc computerized procedure, while an ad-hoc developed Adjustable Helmet Frame (AHF) was used to properly position it in multisession treatments, even at home. We used neuronavigation to test the RePE shape and position obtained by the new computerized procedure and the re-positioning obtained via the AHF. Using Finite Element Method (FEM) model, we also estimated the intra-cerebral current distribution induced by transcranial direct current stimulation (tDCS) comparing RePE vs. non-RePE with fixed reference. Additionally, we tested, using FEM, various shapes, and positions of the reference electrode taking into account possible small displacements of RePE, to test feasibility of RePE-tES sessions at home. The new RePE neuronavigation-free positioning relies on brain MRI space distances, and produced a mean displacement of 3.5 ± 0.8 mm, and the re-positioning of 4.8 ± 1.1 mm. Higher electric field in S1 than in M1 was best obtained with the occipital reference electrode, a montage that proved to feature low sensitivity to typical RePE millimetric displacements. Additionally, a new tES accessory was developed to enable repositioning the electrodes over the scalp also at home, with a precision which is acceptable according to the modeling-estimated intracerebral currents. Altogether, we provide here a procedure to simplify and make easily applicable RePE-tDCS, which enables efficacious personalized treatments. PMID:29867308

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage.

PubMed

Guan, Cao; Wang, John

2016-10-01

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage

PubMed Central

2016-01-01

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution‐based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed. PMID:27840793

Hydrometallurgical treatment of nickel-metal hydride battery electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyman, J.W.; Palmer, G.R.

1995-12-31

Nickel-metal hydride (Ni-MH) battery electrodes have been developed as a substitute for cadmium-containing negative electrodes. Use of NI-MH electrodes offers enhanced electrochemical properties in many instances as well as reduced environmental toxicity. Rechargeable batteries using NI-MH electrodes are also strong candidates for electric vehicles. During the production and secondary reclamation of these battery types, recycling procedures will be needed to prevent environmental impact caused by these wastes as well as to recover the value inherent in the scrap. The US Bureau of Mines (USBM) is investigating hydrometallurgical technology that separates and recovers purified metallic components from Ni-MH battery scrap ofmore » two types, AB{sub 2} and AB{sub 5}. An investigation of acid dissolution and metal recovery techniques has determined several processing alternatives that may be used to promote the successful recycling of much of the battery fabrication scrap and eventual secondary scrap. The metals recovered are Ni, Co, and rare earth metals. Although recovery techniques have been identified in principal, their applicability to mixed battery waste stream and economic attractiveness remain to be demonstrated.« less

Functionalization of indium-tin-oxide electrodes by laser-nanostructured gold thin films for biosensing applications

NASA Astrophysics Data System (ADS)

Grochowska, Katarzyna; Siuzdak, Katarzyna; Karczewski, Jakub; Śliwiński, Gerard

2015-12-01

The production and properties of the indium-tin-oxide (ITO) electrodes functionalized by Au nanoparticle (NP) arrays of a relatively large area formed by pulsed laser nanostructuring of thin gold films are reported and discussed. The SEM inspection of modified electrodes reveals the presence of the nearly spherical and disc-shaped particles of dimensions in the range of 40-120 nm. The NP-array geometry can be controlled by selection of the laser processing conditions. It is shown that particle size and packing density of the array are important factors which determine the electrode performance. In the case of NP-modified electrodes the peak current corresponding to the glucose direct oxidation process shows rise with increasing glucose concentration markedly higher comparing to the reference Au disc electrode. The detection limit reaches 12 μM and linear response of the sensor is observed from 0.1 to 47 mM that covers the normal physiological range of the blood sugar detection.

Impedances of electrochemically impregnated nickel electrodes as functions of potential, KOH concentration, and impregnation method

NASA Technical Reports Server (NTRS)

Reid, Margaret A.

1989-01-01

Impedances of fifteen electrodes form each of the four U.S. manufactures were measured at 0.200 V vs. the Hg/HgO reference electrode. This corresponds to a voltage of 1.145 for a Ni/H2 cell. Measurements were also made of a representative sample of these at 0.44 V. At the higher voltage, the impedances were small and very similar, but at the lower voltage there were major differences between manufacturers. Electrodes from the same manufacturers showed only small differences. The impedances of electrodes from two manufacturers were considerably different in 26 percent KOH from those in 31 percent KOH. These preliminary results seen to correlate with the limited data from earlier life testing of cells from these manufacturers. The impedances of cells being tested for Space Station Freedom are being followed, and more impendance measurements of electrodes are being performed as functions of manufacturer, voltage, electrolyte concentration, and cycle history in hopes of finding better correlations of impedance with life.

Vertically aligned single-walled carbon nanotubes as low-cost and high electrocatalytic counter electrode for dye-sensitized solar cells.

PubMed

Dong, Pei; Pint, Cary L; Hainey, Mel; Mirri, Francesca; Zhan, Yongjie; Zhang, Jing; Pasquali, Matteo; Hauge, Robert H; Verduzco, Rafael; Jiang, Mian; Lin, Hong; Lou, Jun

2011-08-01

A novel dye-sensitized solar cell (DSSC) structure using vertically aligned single-walled carbon nanotubes (VASWCNTs) as the counter electrode has been developed. In this design, the VASWCNTs serve as a stable high surface area and highly active electrocatalytic counter-electrode that could be a promising alternative to the conventional Pt analogue. Utilizing a scalable dry transfer approach to form a VASWCNTs conductive electrode, the DSSCs with various lengths of VASWCNTs were studied. VASWCNTs-DSSC with 34 μm original length was found to be the optimal choice in the present study. The highest conversion efficiencies of VASWCNTs-DSSC achieved 5.5%, which rivals that of the reference Pt DSSC. From the electrochemical impedance spectroscopy analysis, it shows that the new DSSC offers lower interface resistance between the electrolyte and the counter electrode. This reproducible work emphasizes the promise of VASWCNTs as efficient and stable counter electrode materials in DSSC device design, especially taking into account the low-cost merit of this promising material.

Transparent Ti-In-Sn-O multicomponent anodes for highly efficient phosphorescent organic light emitting diodes

NASA Astrophysics Data System (ADS)

Lim, Jong-Wook; Jun Kang, Seong; Lee, Sunghun; Kim, Jang-Joo; Kim, Han-Ki

2012-07-01

We report on transparent Ti-In-Sn-O (TITO) multicomponent anodes prepared by co-sputtering anatase TiO2-x and ITO targets to produce highly efficient phosphorescent organic light emitting diodes (OLEDs). In spite of the incorporation of low cost TiO2, the crystalline TITO electrode annealed at temperature of 600 °C showed a sheet resistance of 18.06 Ω/sq, an optical transmittance of 87.96% at a wavelength of 550 nm, and a work function of 4.71 eV comparable to conventional ITO electrode. Both the quantum (21.69%) and power efficiencies (90.92 lm/W) of the phosphorescent OLED fabricated on the TITO anode were higher than those of the OLED with the reference ITO anode due to the high transparency of the TITO electrodes. This indicates that the TITO electrode is a promising indium-saving electrode that can replace high-cost ITO electrodes in the manufacture of low-cost, highly efficient phosphorescent OLEDs.

Manganese oxide-based materials as electrochemical supercapacitor electrodes.

PubMed

Wei, Weifeng; Cui, Xinwei; Chen, Weixing; Ivey, Douglas G

2011-03-01

Electrochemical supercapacitors (ECs), characteristic of high power and reasonably high energy densities, have become a versatile solution to various emerging energy applications. This critical review describes some materials science aspects on manganese oxide-based materials for these applications, primarily including the strategic design and fabrication of these electrode materials. Nanostructurization, chemical modification and incorporation with high surface area, conductive nanoarchitectures are the three major strategies in the development of high-performance manganese oxide-based electrodes for EC applications. Numerous works reviewed herein have shown enhanced electrochemical performance in the manganese oxide-based electrode materials. However, many fundamental questions remain unanswered, particularly with respect to characterization and understanding of electron transfer and atomic transport of the electrochemical interface processes within the manganese oxide-based electrodes. In order to fully exploit the potential of manganese oxide-based electrode materials, an unambiguous appreciation of these basic questions and optimization of synthesis parameters and material properties are critical for the further development of EC devices (233 references).

Determination of selected elements in whole coal and in coal ash from the eight argonne premium coal samples by atomic absorption spectrometry, atomic emission spectrometry, and ion-selective electrode

USGS Publications Warehouse

Doughten, M.W.; Gillison, J.R.

1990-01-01

Methods for the determination of 24 elements in whole coal and coal ash by inductively coupled argon plasma-atomic emission spectrometry, flame, graphite furnace, and cold vapor atomic absorption spectrometry, and by ion-selective electrode are described. Coal ashes were analyzed in triplicate to determine the precision of the methods. Results of the analyses of NBS Standard Reference Materials 1633, 1633a, 1632a, and 1635 are reported. Accuracy of the methods is determined by comparison of the analysis of standard reference materials to their certified values as well as other values in the literature.

AAO-CNTs electrode on microfluidic flow injection system for rapid iodide sensing.

PubMed

Phokharatkul, Ditsayut; Karuwan, Chanpen; Lomas, Tanom; Nacapricha, Duangjai; Wisitsoraat, Anurat; Tuantranont, Adisorn

2011-06-15

In this work, carbon nanotubes (CNTs) nanoarrays in anodized aluminum oxide (AAO-CNTs) nanopore is integrated on a microfluidic flow injection system for in-channel electrochemical detection of iodide. The device was fabricated from PDMS (polydimethylsiloxane) microchannel bonded on glass substrates that contains three-electrode electrochemical system, including AAO-CNTs as a working electrode, silver as a reference electrode and platinum as an auxiliary electrode. Aluminum, stainless steel catalyst, silver and platinum layers were sputtered on the glass substrate through shadow masks. Aluminum layer was then anodized by two-step anodization process to form nanopore template. CNTs were then grown in AAO template by thermal chemical vapor deposition. The amperometric detection of iodide was performed in 500-μm-wide and 100-μm-deep microchannels on the microfluidic chip. The influences of flow rate, injection volume and detection potential on the current response were optimized. From experimental results, AAO-CNTs electrode on chip offers higher sensitivity and wider dynamic range than CNTs electrode with no AAO template. Copyright © 2011 Elsevier B.V. All rights reserved.

Visualization and mechanisms of splashing erosion of electrodes in a DC air arc

NASA Astrophysics Data System (ADS)

Wu, Yi; Cui, Yufei; Rong, Mingzhe; Murphy, Anthony B.; Yang, Fei; Sun, Hao; Niu, Chunping; Fan, Shaodi

2017-11-01

The splashing erosion of electrodes in a DC atmospheric-pressure air arc has been investigated by visualization of the electrode surface and the sputtered droplets, and tracking of the droplet trajectories, using image processing techniques. A particle tracking velocimetry algorithm has been introduced to measure the sputtering velocity distribution. Erosion of both tungsten-copper and tungsten-ceria electrodes is studied; in both cases electrode erosion is found to be dominated by droplet splashing rather than metal evaporation. Erosion is directly influenced by both melting and the formation of plasma jets, and can be reduced by the tuning of the plasma jet and electrode material. The results provide an understanding of the mechanisms that lead to the long lifetime of tungsten-copper electrodes, and may provide a path for the design of the electrode system subjected to electric arc to minimize erosion.

Novel laboratory methods for determining the fine scale electrical resistivity structure of core

NASA Astrophysics Data System (ADS)

Haslam, E. P.; Gunn, D. A.; Jackson, P. D.; Lovell, M. A.; Aydin, A.; Prance, R. J.; Watson, P.

2014-12-01

High-resolution electrical resistivity measurements are made on saturated rocks using novel laboratory instrumentation and multiple electrical voltage measurements involving in principle a four-point electrode measurement but with a single, moving electrode. Flat, rectangular core samples are scanned by varying the electrode position over a range of hundreds of millimetres with an accuracy of a tenth of a millimetre. Two approaches are tested involving a contact electrode and a non-contact electrode arrangement. The first galvanic method uses balanced cycle switching of a floating direct current (DC) source to minimise charge polarisation effects masking the resistivity distribution related to fine scale structure. These contacting electrode measurements are made with high common mode noise rejection via differential amplification with respect to a reference point within the current flow path. A computer based multifunction data acquisition system logs the current through the sample and voltages along equipotentials from which the resistivity measurements are derived. Multiple measurements are combined to create images of the surface resistivity structure, with variable spatial resolution controlled by the electrode spacing. Fine scale sedimentary features and open fractures in saturated rocks are interpreted from the measurements with reference to established relationships between electrical resistivity and porosity. Our results successfully characterise grainfall lamination and sandflow cross-stratification in a brine saturated, dune bedded core sample representative of a southern North Sea reservoir sandstone, studied using the system in constant current, variable voltage mode. In contrast, in a low porosity marble, identification of open fracture porosity against a background very low matrix porosity is achieved using the constant voltage, variable current mode. This new system is limited by the diameter of the electrode that for practical reasons can only be reduced to between 0.5 and 0.75 mm. Improvements to this resolution may be achieved by further reducing the electrode footprint to 0.1 mm × 0.1 mm using a novel high-impedance, non-contact potential probe. Initial results with this non-contact electric potential sensor indicate the possibility for generating images with grain-scale resolution.

Bacteria detection instrument and method

NASA Technical Reports Server (NTRS)

Renner, W.; Fealey, R. D. (Inventor)

1972-01-01

A method and apparatus for screening a sample fluid for bacterial presence are disclosed wherein the fluid sample is mixed with culture media of sufficient quantity to permit bacterial growth in order to obtain a test solution. The concentration of oxygen dissolved in the test solution is then monitored using the potential difference between a reference electrode and a noble metal electrode which are in contact with the test solution. The change in oxygen concentration which occurs during a period of time as indicated by the electrode potential difference is compared with a detection criterion which exceeds the change which would occur absent bacteria.

A cochlear implant phantom for evaluating CT acquisition parameters

NASA Astrophysics Data System (ADS)

Chakravorti, Srijata; Bussey, Brian J.; Zhao, Yiyuan; Dawant, Benoit M.; Labadie, Robert F.; Noble, Jack H.

2017-03-01

Cochlear Implants (CIs) are surgically implantable neural prosthetic devices used to treat profound hearing loss. Recent literature indicates that there is a correlation between the positioning of the electrode array within the cochlea and the ultimate hearing outcome of the patient, indicating that further studies aimed at better understanding the relationship between electrode position and outcomes could have significant implications for future surgical techniques, array design, and processor programming methods. Post-implantation high resolution CT imaging is the best modality for localizing electrodes and provides the resolution necessary to visually identify electrode position, albeit with an unknown degree of accuracy depending on image acquisition parameters, like the HU range of reconstruction, radiation dose, and resolution of the image. In this paper, we report on the development of a phantom that will both permit studying which CT acquisition parameters are best for accurately identifying electrode position and serve as a ground truth for evaluating how different electrode localization methods perform when using different CT scanners and acquisition parameters. We conclude based on our tests that image resolution and HU range of reconstruction strongly affect how accurately the true position of the electrode array can be found by both experts and automatic analysis techniques. The results presented in this paper demonstrate that our phantom is a versatile tool for assessing how CT acquisition parameters affect the localization of CIs.

Composite substrate for bipolar electrodes

DOEpatents

Tekkanat, Bora; Bolstad, James J.

1992-12-22

Substrates for electrode systems, particularly those to be used for bipolar electrodes in zinc-bromine batteries, are disclosed. The substrates preferably include carbon-black as a conductive filler in a polymeric matrix, with reinforcing materials such as glass fibers. Warpage of the zinc-bromine electrodes which was experienced in the prior art and which was believed to be caused by physical expansion of the electrodes due to bromine absorption by the carbon-black, is substantially eliminated when new substrate fabrication techniques are employed. In the pesent invention, substrates are prepared using a lamination process known as glass mat reinforced thermoplastics technology or, in an alternate embodiment, the substrate is made using a slurry process.

Advanced electrodes for AMTEC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fiebig, Brad; Schuller, Michael; Hudson, Patricia

1999-01-01

Texas A&M University has begun an investigation of materials and fabrication methods which will improve AMTEC electrode performance. The study currently involves gathering data on materials which meet the basic requirements of operating in an AMTEC cell, and sorting out candidates possessing characteristics conducive to efficient AMTEC operation. An initial assessment has shown Iridium as a promising metal electrode candidate. Sodium-containing double-oxides, with melting temperatures above AMTEC operating temperatures, including NaNbO{sub 3} and Na{sub 2}Ti{sub 3}O{sub 7}, have been identified as possible electrode dopants, to enhance the sodium conductivity of an electrode. Photo-deposition and Evaporative-deposition will be investigated further asmore » electrode fabrication techniques. {copyright} {ital 1999 American Institute of Physics.}« less

Technical tips: Electrode application and preventing skin breakdown techniques.

PubMed

Berlin, Fira; Carlile, Jennifer A; de Burgo, Maria I; Rochon, Adrienne; Wagner, Esperanza E; Sellers, Martha C; Worrell, Amanda R; Andal, E Lauren C; Woods, Latina R

2011-09-01

The recording electrodes including their precise location, their ability to record during movements that can be intense during a convulsive seizure, and their capability to record for several days without causing skin breakdown are an integral part of long-term EEG recording. Many of the facets of EEG technology have changed dramatically with the introduction of digital EEG. But the electrode and the electrode/skin interface have not had many dramatic changes. The technologist still looks for ways to ensure correct electrode placement, good recording capabilities, and a patient with healthy skin when the electrodes are removed. This Technical Tips features ideas and experiences from several technologists. These technologists express suggestions and opinions which are accepted in Technical Tips.

Current density distributions and sputter marks in electron cyclotron resonance ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panitzsch, Lauri; Peleikis, Thies; Boettcher, Stephan

2013-01-15

Most electron cyclotron resonance ion sources use hexapolar magnetic fields for the radial confinement of the plasma. The geometry of this magnetic structure is then-induced by charged particles-mapped onto the inner side of the plasma electrode via sputtering and deposition. The resulting structures usually show two different patterns: a sharp triangular one in the central region which in some cases is even sputtered deep into the material (referred to as thin groove or sharp structure), and a blurred but still triangular-like one in the surroundings (referred to as broad halo). Therefore, both patterns seem to have different sources. To investigatemore » their origins we replaced the standard plasma electrode by a custom-built plasma electrode acting as a planar, multi-segment current-detector. For different biased disc voltages, detector positions, and source biases (referred to the detector) we measured the electrical current density distributions in the plane of the plasma electrode. The results show a strong and sharply confined electron population with triangular shape surrounded by less intense and spatially less confined ions. Observed sputter- and deposition marks are related to the analysis of the results. Our measurements suggest that the two different patterns (thin and broad) indeed originate from different particle populations. The thin structures seem to be caused by the hot electron population while the broad marks seem to stem from the medium to highly charged ions. In this paper we present our measurements together with theoretical considerations and substantiate the conclusions drawn above. The validity of these results is also discussed.« less

Ag2O:SiO2:V2O5 Glass System:. a Novel Reference Electrode for SO2 Gas Sensor

NASA Astrophysics Data System (ADS)

Singh, K.; Lad, A.; Bhoga, S. S.

2002-12-01

Ag2O:SiO2:V2O5 glass system with 0.5≤ y ≥ 0.66 for fixed n = 9 is synthesized, structurally and electrically characterized with a view to have high glass transition temperature (Tg ≈ 500°C) which can be used as solid reference electrode in electrochemical SOx gas sensor application. 10Ag2O:40SiO2:50V2O5 glass having Tg ≈ 502°C exhibits maximum bulk and electronic conductivity 3.67*10-3 and 4.47*10-2 S/cm, respectively at 450°C. The increase in conductivity is understood to be due to a mixed former effect. A few galvanic SOx sensors fabricated utilizing optimized glass as reference and Ag+ conducting solid electrolyte responds to change in PSOx according to 2 electron cell reaction.

Critical evaluation of the stability of highly concentrated LiTFSI - Acetonitrile electrolytes vs. graphite, lithium metal and LiFePO4 electrodes

NASA Astrophysics Data System (ADS)

Nilsson, Viktor; Younesi, Reza; Brandell, Daniel; Edström, Kristina; Johansson, Patrik

2018-04-01

Highly concentrated LiTFSI - acetonitrile electrolytes have recently been shown to stabilize graphite electrodes in lithium-ion batteries (LIBs) much better than comparable more dilute systems. Here we revisit this system in order to optimise the salt concentration vs. both graphite and lithium metal electrodes with respect to electrochemical stability. However, we observe an instability regardless of concentration, making lithium metal unsuitable as a counter electrode, and this also affects evaluation of e.g. graphite electrodes. While the highly concentrated electrolytes have much improved electrochemical stabilities, their reductive decomposition below ca. 1.2 V vs. Li+/Li° still makes them less practical vs. graphite electrodes, and the oxidative reaction with Al at ca. 4.1 V vs. Li+/Li° makes them problematic for high voltage LIB cells. The former originates in an insufficiently stable solid electrolyte interphase (SEI) dissolving and continuously reforming - causing self-discharge, as observed by paused galvanostatic cycling, while the latter is likely caused by aluminium current collector corrosion. Yet, we show that medium voltage LiFePO4 positive electrodes can successfully be used as counter and reference electrodes.

A fracture mechanics study of the phase separating planar electrodes: Phase field modeling and analytical results

NASA Astrophysics Data System (ADS)

Haftbaradaran, H.; Maddahian, A.; Mossaiby, F.

2017-05-01

It is well known that phase separation could severely intensify mechanical degradation and expedite capacity fading in lithium-ion battery electrodes during electrochemical cycling. Experiments have frequently revealed that such degradation effects could be substantially mitigated via reducing the electrode feature size to the nanoscale. The purpose of this work is to present a fracture mechanics study of the phase separating planar electrodes. To this end, a phase field model is utilized to predict how phase separation affects evolution of the solute distribution and stress profile in a planar electrode. Behavior of the preexisting flaws in the electrode in response to the diffusion induced stresses is then examined via computing the time dependent stress intensity factor arising at the tip of flaws during both the insertion and extraction half-cycles. Further, adopting a sharp-interphase approximation of the system, a critical electrode thickness is derived below which the phase separating electrode becomes flaw tolerant. Numerical results of the phase field model are also compared against analytical predictions of the sharp-interphase model. The results are further discussed with reference to the available experiments in the literature. Finally, some of the limitations of the model are cautioned.

Phase field modeling of microstructure evolution and concomitant effective conductivity change in solid oxide fuel cell electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Yinkai; Cheng, Tian -Le; Wen, You -Hai

Microstructure evolution plays an important role in the performance degradation of SOFC electrodes. In this work, we propose a much improved phase field model to simulate the microstructure evolution in the electrodes of solid oxide fuel cell. We demonstrate that the tunability of the interfacial energy in this model has been significantly enhanced. Parameters are set to fit for the interfacial energies of a typical Ni-YSZ anode, an LSM-YSZ cathode and an artificial reference electrode, respectively. The contact angles at various triple junctions and the microstructure evolutions in two dimensions are calibrated to verify the model. As a demonstration ofmore » the capabilities of the model, three dimensional microstructure evolutions are simulated applying the model to the three different electrodes. The time evolutions of grain size and triple phase boundary density are analyzed. In addition, a recently proposed bound charge successive approximation algorithm is employed to calculate the effective conductivity of the electrodes during microstructure evolution. Furthermore, the effective conductivity of all electrodes are found to decrease during the microstructure evolution, which is attributed to the increased tortuosity and the loss of percolated volume fraction of the electrode phase.« less

Phase field modeling of microstructure evolution and concomitant effective conductivity change in solid oxide fuel cell electrodes

DOE PAGES

Lei, Yinkai; Cheng, Tian -Le; Wen, You -Hai

2017-02-13

Microstructure evolution plays an important role in the performance degradation of SOFC electrodes. In this work, we propose a much improved phase field model to simulate the microstructure evolution in the electrodes of solid oxide fuel cell. We demonstrate that the tunability of the interfacial energy in this model has been significantly enhanced. Parameters are set to fit for the interfacial energies of a typical Ni-YSZ anode, an LSM-YSZ cathode and an artificial reference electrode, respectively. The contact angles at various triple junctions and the microstructure evolutions in two dimensions are calibrated to verify the model. As a demonstration ofmore » the capabilities of the model, three dimensional microstructure evolutions are simulated applying the model to the three different electrodes. The time evolutions of grain size and triple phase boundary density are analyzed. In addition, a recently proposed bound charge successive approximation algorithm is employed to calculate the effective conductivity of the electrodes during microstructure evolution. Furthermore, the effective conductivity of all electrodes are found to decrease during the microstructure evolution, which is attributed to the increased tortuosity and the loss of percolated volume fraction of the electrode phase.« less

Detection of cephradine through the electrochemical study of the degradation product of cephradine

NASA Astrophysics Data System (ADS)

Jiang, Qingfeng; Ying, Yibin; Wang, Jianping; Ye, Zunzhong; Li, Yanbin

2005-11-01

The degradation product of cephradine(CEP), a broad spectrum antibiotic, with NaOH was studied in solution by Cyclic Voltammetry and Differential Pulse Voltammetry at a three electrode system (Gold working electrode, Hg/HgCl reference electrode and Platinum counter electrode). Our experiment was based on that the R-SH in degradation product could cause a deoxidization peak at gold working electrode. The response was optimized with respect to accumulation time, ionic strength, drug concentration, reproducibility and other variables. We found that the degradation product of CEP in Na2HPO4-NaH2PO4 buffer could cause a sensitive deoxidization peak at -0.68V. A linear dependence of peak currents on the concentration was observed in the range of 10-7 - 10-6 mol/L, with a detection limit of 0.5*10-7mol/L. This method can achieve satisfactory results in the application of detecting human-made CEP.

Electrochemical preparation of composite polyaniline coating and its application in the determination of bisphenol A, 4-n-nonylphenol, 4-tert-octylphenol using direct solid phase microextraction coupled with high performance liquid chromatography.

PubMed

Huang, Minjia; Jiang, Guibin; Cai, Yaqi

2005-11-01

For SPME-HPLC, metal wires with better mechanical strength are preferred over the fused silica fibers. In this article, a novel composite polyaniline (CPANI) doped with PEG and polydimethylsiloxane coating (CPANI fiber) was prepared on a stainless steel wire by a three-electrode system: the fiber was used as the work electrode, a calomel electrode and a platinum electrode were used as the reference and the counter electrodes, respectively. To evaluate the new CPANI coating, the coating was used to extract three kinds of phenols (bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol) in water samples by direct-SPME mode and then desorbed in commercial SPME-HPLC interface to separation. The extraction procedure was also optimized. Five real water samples were investigated. Good recoveries were gained when environmental samples were analyzed.

Electrochemical detection device. [for use in microbiology

NASA Technical Reports Server (NTRS)

Young, R. N.; Wilkins, J. R. (Inventor)

1979-01-01

A standard pH reference electrode and a platinum cathodic electrode are positioned in a container with suitable nutrient medium for microbial growth plus the sample to be tested. The two electrodes are connected to electronic circuitry including an up/down counter whicn counts up for the first 80 minutes after a test has initiated. Then the potential between the two electrodes is tracked by the electronic circuitry and after there is a change of 10 mv a signal is sent to the up/down counter to cause it to reverse its count. When there is a additional 20 mv change in the potential between the two electrodes another signal is sent to the up/down counter, signalling it to stop. The resulting count on the counter is equal to the length of time for the inoculum to begin the production of measurable amounts of H2 after inoculation.

Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mistry, Aashutosh N.; Smith, Kandler; Mukherjee, Partha P.

Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically andmore » transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure-transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.« less

Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes

DOE PAGES

Mistry, Aashutosh N.; Smith, Kandler; Mukherjee, Partha P.

2018-01-12

Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically andmore » transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure-transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.« less

Linear conduction in N-type organic field effect transistors with nanometric channel lengths and graphene as electrodes

NASA Astrophysics Data System (ADS)

Chianese, F.; Candini, A.; Affronte, M.; Mishra, N.; Coletti, C.; Cassinese, A.

2018-05-01

In this work, we test graphene electrodes in nanometric channel n-type Organic Field Effect Transistors (OFETs) based on thermally evaporated thin films of the perylene-3,4,9,10-tetracarboxylic acid diimide derivative. By a thorough comparison with short channel transistors made with reference gold electrodes, we found that the output characteristics of the graphene-based devices respond linearly to the applied bias, in contrast with the supralinear trend of gold-based transistors. Moreover, short channel effects are considerably suppressed in graphene electrode devices. More specifically, current on/off ratios independent of the channel length (L) and enhanced response for high longitudinal biases are demonstrated for L down to ˜140 nm. These results are rationalized taking into account the morphological and electronic characteristics of graphene, showing that the use of graphene electrodes may help to overcome the problem of Space Charge Limited Current in short channel OFETs.

High-channel-count, high-density microelectrode array for closed-loop investigation of neuronal networks.

PubMed

Tsai, David; John, Esha; Chari, Tarun; Yuste, Rafael; Shepard, Kenneth

2015-01-01

We present a system for large-scale electrophysiological recording and stimulation of neural tissue with a planar topology. The recording system has 65,536 electrodes arranged in a 256 × 256 grid, with 25.5 μm pitch, and covering an area approximately 42.6 mm(2). The recording chain has 8.66 μV rms input-referred noise over a 100 ~ 10k Hz bandwidth while providing up to 66 dB of voltage gain. When recording from all electrodes in the array, it is capable of 10-kHz sampling per electrode. All electrodes can also perform patterned electrical microstimulation. The system produces ~ 1 GB/s of data when recording from the full array. To handle, store, and perform nearly real-time analyses of this large data stream, we developed a framework based around Xilinx FPGAs, Intel x86 CPUs and the NVIDIA Streaming Multiprocessors to interface with the electrode array.

A calibration-free electrode compensation method

PubMed Central

Rossant, Cyrille; Fontaine, Bertrand; Magnusson, Anna K.

2012-01-01

In a single-electrode current-clamp recording, the measured potential includes both the response of the membrane and that of the measuring electrode. The electrode response is traditionally removed using bridge balance, where the response of an ideal resistor representing the electrode is subtracted from the measurement. Because the electrode is not an ideal resistor, this procedure produces capacitive transients in response to fast or discontinuous currents. More sophisticated methods exist, but they all require a preliminary calibration phase, to estimate the properties of the electrode. If these properties change after calibration, the measurements are corrupted. We propose a compensation method that does not require preliminary calibration. Measurements are compensated offline by fitting a model of the neuron and electrode to the trace and subtracting the predicted electrode response. The error criterion is designed to avoid the distortion of compensated traces by spikes. The technique allows electrode properties to be tracked over time and can be extended to arbitrary models of electrode and neuron. We demonstrate the method using biophysical models and whole cell recordings in cortical and brain-stem neurons. PMID:22896724

Calligraphic Poling of Ferroelectric Material

NASA Technical Reports Server (NTRS)

Mohageg, Makan; Strekalov, Dmitry; Savchenkov, Anatoliy; Matsko, Adrey; Maleki, Lute; Iltchenko, Vladimir

2007-01-01

Calligraphic poling is a technique for generating an arbitrary, possibly complex pattern of localized reversal in the direction of permanent polarization in a wafer of LiNbO3 or other ferroelectric material. The technique is so named because it involves a writing process in which a sharp electrode tip is moved across a surface of the wafer to expose the wafer to a polarizing electric field in the desired pattern. The technique is implemented by use of an apparatus, denoted a calligraphic poling machine (CPM), that includes the electrode and other components as described in more detail below.

Effect of radiofrequency energy emitted from monopolar "Bovie" instruments on cardiac implantable electronic devices.

PubMed

Robinson, Thomas N; Varosy, Paul D; Guillaume, Girard; Dunning, James E; Townsend, Nicole T; Jones, Edward L; Paniccia, Alessandro; Stiegmann, Greg V; Weyer, Christopher; Rozner, Marc A

2014-09-01

The monopolar "Bovie" instrument emits radiofrequency energy that can disrupt the function of other implanted electronic devices through a phenomenon termed electromagnetic interference. The purpose of this study was to quantify the electromagnetic interference occurring on cardiac implantable devices (CIEDs) resulting from monopolar instrument use in common, modifiable clinical scenarios. Three anesthetized pigs underwent CIED placement (1 pacemaker and 2 defibrillators). Electromagnetic interference was quantified when changing the monopolar instrument parameters of generator power, generator mode, surgical technique, orientation of active electrode cord, pathway of current vector, and proximity of active electrode to the CIED. Monopolar instrument parameters that decreased the electromagnetic interference occurring on the CIED included decreasing generator power from 60 W to 30 W (p < 0.001), using cut mode rather than coag mode (p < 0.001), using desiccation technique rather than fulguration technique (p < 0.001), orienting the active electrode cord from the feet rather than across the chest wall (p < 0.001), and avoiding the current vector from crossing the CIED system (p < 0.001). Increasing the distance between the active electrode tool and the CIED system decreased electromagnetic interference occurring on the CIED in a dose-response fashion up to a distance of 10 cm (ANOVA, p < 0.001), after which the magnitude of electromagnetic interference remained constant. Electromagnetic interference occurring on CIEDs resulting from monopolar instruments is minimized by decreasing generator power, using cut mode, using desiccation technique, orienting the active electrode cord from the feet, avoiding the current vector for crossing the CIED system, and increasing the distance between the active electrode and the CIED. Surgeons and operating room staff can minimize electromagnetic interference on CIEDs during monopolar instrument use by accounting for these modifiable clinical factors. Copyright © 2014 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

A Palladium-Tin Modified Microband Electrode Array for Nitrate Determination

PubMed Central

Fu, Yexiang; Bian, Chao; Kuang, Jian; Wang, Jinfen; Tong, Jianhua; Xia, Shanhong

2015-01-01

A microband electrode array modified with palladium-tin bimetallic composite has been developed for nitrate determination. The microband electrode array was fabricated by Micro Electro-Mechanical System (MEMS) technique. Palladium and tin were electrodeposited successively on the electrode, forming a double-layer structure. The effect of the Pd-Sn composite was investigated and its enhancement of catalytic activity and lifetime was revealed. The Pd-Sn modified electrode showed good linearity (R2 = 0.998) from 1 mg/L to 20 mg/L for nitrate determination with a sensitivity of 398 μA/(mg∙L−1∙cm2). The electrode exhibited a satisfying analytical performance after 60 days of storage, indicating a long lifetime. Good repeatability was also displayed by the Pd-Sn modified electrodes. The results provided an option for nitrate determination in water. PMID:26389904

Methods and systems for in-situ electroplating of electrodes

DOEpatents

Zappi, Guillermo Daniel; Zarnoch, Kenneth Paul; Huntley, Christian Andrew; Swalla, Dana Ray

2015-06-02

The present techniques provide electrochemical devices having enhanced electrodes with surfaces that facilitate operation, such as by formation of a porous nickel layer on an operative surface, particularly of the cathode. The porous metal layer increases the surface area of the electrode, which may result in increasing the efficiency of the electrochemical devices. The formation of the porous metal layer is performed in situ, that is, after the assembly of the electrodes into an electrochemical device. The in situ process offers a number of advantages, including the ability to protect the porous metal layer on the electrode surface from damage during assembly of the electrochemical device. The enhanced electrode and the method for its processing may be used in any number of electrochemical devices, and is particularly well suited for electrodes in an electrolyzer useful for splitting water into hydrogen and oxygen.

Mirror Langmuir probe: a technique for real-time measurement of magnetized plasma conditions using a single Langmuir electrode.

PubMed

LaBombard, B; Lyons, L

2007-07-01

A new method for the real-time evaluation of the conditions in a magnetized plasma is described. The technique employs an electronic "mirror Langmuir probe" (MLP), constructed from bipolar rf transistors and associated high-bandwidth electronics. Utilizing a three-state bias wave form and active feedback control, the mirror probe's I-V characteristic is continuously adjusted to be a scaled replica of the "actual" Langmuir electrode immersed in a plasma. Real-time high-bandwidth measurements of the plasma's electron temperature, ion saturation current, and floating potential can thereby be obtained using only a single electrode. Initial tests of a prototype MLP system are reported, proving the concept. Fast-switching metal-oxide-semiconductor field-effect transistors produce the required three-state voltage bias wave form, completing a full cycle in under 1 mus. Real-time outputs of electron temperature, ion saturation current, and floating potential are demonstrated, which accurately track an independent computation of these values from digitally stored I-V characteristics. The MLP technique represents a significant improvement over existing real-time methods, eliminating the need for multiple electrodes and sampling all three plasma parameters at a single spatial location.

Utilizing neuronavigation for virtual electrode representation and safe resection following SEEG; a technical report.

PubMed

Brandmeir, Nicholas; Sather, Michael

2018-02-20

One of the most effective treatments for epilepsy is resection, but it remains underutilized. Efforts must be made to increase the ease, safety, and efficacy of epilepsy resection to improve utilization. Studies have shown an improved risk profile of stereoelectroencephalography (SEEG) over subdural grids (SDG) for invasive monitoring. One limitation to increased adoption of SEEG at epilepsy centers is the theoretical difficulty of planning a delayed resection once electrodes are removed. Our objective was to develop and present a technique using readily available neuronavigation technology to guide a cortical, non-lesional epilepsy resection with co-registration of imaging during invasive monitoring to imaging in an explanted patient, allowing for virtual visualization of electrodes. An example case taking advantage of the technique described above as an adjunct for an anatomically guided resection is presented with technical details and images. Intraoperative neuronavigation was successfully used to virtually represent previously removed SEEG electrodes and accuracy could be easily verified by examining scars on the scalp, bone, dura and pia. The simple technique presented can be a useful adjunct to resection following SEEG. This may help increase the adoption of SEEG, even when resection is planned.

Polarity effects and apparent ion recombination in microionization chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Jessica R., E-mail: miller@humonc.wisc.edu; Hooten, Brian D.; Micka, John A.

Purpose: Microchambers demonstrate anomalous voltage-dependent polarity effects. Existing polarity and ion recombination correction factors do not account for these effects. As a result, many commercial microchamber models do not meet the specification of a reference-class ionization chamber as defined by the American Association of Physicists in Medicine. The purpose of this investigation is to determine the cause of these voltage-dependent polarity effects. Methods: A series of microchamber prototypes were produced to isolate the source of the voltage-dependent polarity effects. Parameters including ionization-chamber collecting-volume size, stem and cable irradiation, chamber assembly, contaminants, high-Z materials, and individual chamber components were investigated. Measurementsmore » were performed with electrodes coated with graphite to isolate electrode conductivity. Chamber response was measured as the potential bias of the guard electrode was altered with respect to the collecting electrode, through the integration of additional power supplies. Ionization chamber models were also simulated using COMSOL Multiphysics software to investigate the effect of a potential difference between electrodes on electric field lines and collecting volume definition. Results: Investigations with microchamber prototypes demonstrated that the significant source of the voltage-dependent polarity effects was a potential difference between the guard and collecting electrodes of the chambers. The voltage-dependent polarity effects for each prototype were primarily isolated to either the guard or collecting electrode. Polarity effects were reduced by coating the isolated electrode with a conductive layer of graphite. Polarity effects were increased by introducing a potential difference between the electrodes. COMSOL simulations further demonstrated that for a given potential difference between electrodes, the collecting volume of the chamber changed as the applied voltage was altered, producing voltage-dependent polarity effects in the chamber response. Ionization chamber measurements and COMSOL simulations demonstrated an inverse relationship between the chamber collecting volume size and the severity of voltage-dependent polarity effects on chamber response. The effect of a given potential difference on chamber polarity effects was roughly ten times greater for microchambers as compared to Farmer-type chambers. Stem and cable irradiations, chamber assembly, contaminants, and high-Z materials were not found to be a significant source of the voltage-dependent polarity effects. Conclusions: A potential difference between the guard and collecting electrodes was found to be the primary source of the voltage-dependent polarity effects demonstrated by microchambers. For a given potential difference between electrodes, the relative change in the collecting volume is smaller for larger-volume chambers, illustrating why these polarity effects are not seen in larger-volume chambers with similar guard and collecting electrode designs. Thus, for small-volume chambers, it is necessary to reduce the potential difference between the guard and collecting electrodes in order to reduce polarity effects for reference dosimetry measurements.« less

Beyond the double banana: improved recognition of temporal lobe seizures in long-term EEG.

PubMed

Rosenzweig, Ivana; Fogarasi, András; Johnsen, Birger; Alving, Jørgen; Fabricius, Martin Ejler; Scherg, Michael; Neufeld, Miri Y; Pressler, Ronit; Kjaer, Troels W; van Emde Boas, Walter; Beniczky, Sándor

2014-02-01

To investigate whether extending the 10-20 array with 6 electrodes in the inferior temporal chain and constructing computed montages increases the diagnostic value of ictal EEG activity originating in the temporal lobe. In addition, the accuracy of computer-assisted spectral source analysis was investigated. Forty EEG samples were reviewed by 7 EEG experts in various montages (longitudinal and transversal bipolar, common average, source derivation, source montage, current source density, and reference-free montages) using 2 electrode arrays (10-20 and the extended one). Spectral source analysis used source montage to calculate density spectral array, defining the earliest oscillatory onset. From this, phase maps were calculated for localization. The reference standard was the decision of the multidisciplinary epilepsy surgery team on the seizure onset zone. Clinical performance was compared with the double banana (longitudinal bipolar montage, 10-20 array). Adding the inferior temporal electrode chain, computed montages (reference free, common average, and source derivation), and voltage maps significantly increased the sensitivity. Phase maps had the highest sensitivity and identified ictal activity at earlier time-point than visual inspection. There was no significant difference concerning specificity. The findings advocate for the use of these digital EEG technology-derived analysis methods in clinical practice.

A novel method of fabricating carbon nanotubes-polydimethylsiloxane composite electrodes for electrocardiography.

PubMed

Liu, Benyan; Chen, Yingmin; Luo, Zhangyuan; Zhang, Wenzan; Tu, Quan; Jin, Xun

2015-01-01

Polymer-based flexible electrodes are receiving much attention in medical applications due to their good wearing comfort. The current fabrication methods of such electrodes are not widely applied. In this study, polydimethylsiloxane (PDMS) and conductive additives of carbon nanotubes (CNTs) were employed to fabricate composite electrodes for electrocardiography (ECG). A three-step dispersion process consisting of ultrasonication, stirring, and in situ polymerization was developed to yield homogenous CNTs-PDMS mixtures. The CNTs-PDMS mixtures were used to fabricate CNTs-PDMS composite electrodes by replica technology. The influence of ultrasonication time and CNT concentration on polymer electrode performance was evaluated by impedance and ECG measurements. The signal amplitude of the electrodes prepared using an ultrasonication time of 12 h and CNT content of 5 wt% was comparable to that of commercial Ag/AgCl electrodes. The polymer electrodes were easily fabricated by conventional manufacturing techniques, indicating a potential advantage of reduced cost for mass production.

Comparative study of organic transistors with different graphene electrodes fabricated using a simple patterning method

NASA Astrophysics Data System (ADS)

Kang, Narae; Smith, Christian W.; Ishigami, Masa; Khondaker, Saiful I.

2017-12-01

The performance of organic field-effect transistors (OFETs) can be greatly limited due to the inefficient charge injection caused by the large interfacial barrier at the metal/organic semiconductor interface. To improve this, two-dimensional graphene films have been suggested as alternative electrode materials; however, a comparative study of OFET performances using different types of graphene electrodes has not been systematically investigated. Here, we present a comparative study on the performance of pentacene OFETs using chemical vapor deposition (CVD) grown graphene and reduced graphene oxide (RGO) as electrodes. The large area electrodes were patterned using a simple and environmentally benign patterning technique. Although both the CVD graphene and RGO electrodes showed enhanced device performance compared to metal electrodes, we found the maximum performance enhancement from CVD grown graphene electrodes. Our study suggests that, in addition to the strong π-π interaction at the graphene/organic interface, the higher conductivity of the electrodes also plays an important role in the performance of OFETs.

Electrostatic-Force-Assisted Dispensing Printing to Construct High-Aspect-Ratio of 0.79 Electrodes on a Textured Surface with Improved Adhesion and Contact Resistivity

PubMed Central

Shin, Dong-Youn; Yoo, Sung-Soo; Song, Hee-eun; Tak, Hyowon; Byun, Doyoung

2015-01-01

As a novel route to construct fine and abnormally high-aspect-ratio electrodes with excellent adhesion and reduced contact resistivity on a textured surface, an electrostatic-force-assisted dispensing printing technique is reported and compared with conventional dispensing and electrohydrodynamic jet printing techniques. The electrostatic force applied between a silver paste and the textured surface of a crystalline silicon solar cell wafer significantly improves the physical adhesion of the electrodes, whereas those fabricated using a conventional dispensing printing technique peel off with a silver paste containing 2 wt% of a fluorosurfactant. Moreover, the contact resistivity and dimensionless deviation of total resistance are significantly reduced from 2.19 ± 1.53 mΩ·cm2 to 0.98 ± 0.92 mΩ·cm2 and from 0.10 to 0.03, respectively. By utilizing electrodes with an abnormally high-aspect-ratio of 0.79 (the measured thickness and width are 30.4 μm and 38.3 μm, respectively), the cell efficiency is 17.2% on a polycrystalline silicon solar cell with an emitter sheet resistance of 60 Ω/sq. This cell efficiency is considerably higher than previously reported values obtained using a conventional electrohydrodynamic jet printing technique, by +0.48–3.5%p. PMID:26576857

A microelectromechanical accelerometer fabricated using printed circuit processing techniques

NASA Astrophysics Data System (ADS)

Rogers, J. E.; Ramadoss, R.; Ozmun, P. M.; Dean, R. N.

2008-01-01

A microelectromechanical systems (MEMS) capacitive-type accelerometer fabricated using printed circuit processing techniques is presented. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams is defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height is determined by the distance between the bottom electrode and the Kapton film. For an applied external acceleration (normal to the proof mass), the proof mass deflects toward or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air-gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm × 6.4 mm is reported. The measured resonant frequency is 375 Hz and the Q-factor in air is 0.52.

Combining operando synchrotron X-ray tomographic microscopy and scanning X-ray diffraction to study lithium ion batteries

PubMed Central

Pietsch, Patrick; Hess, Michael; Ludwig, Wolfgang; Eller, Jens; Wood, Vanessa

2016-01-01

We present an operando study of a lithium ion battery combining scanning X-ray diffraction (SXRD) and synchrotron radiation X-ray tomographic microscopy (SRXTM) simultaneously for the first time. This combination of techniques facilitates the investigation of dynamic processes in lithium ion batteries containing amorphous and/or weakly attenuating active materials. While amorphous materials pose a challenge for diffraction techniques, weakly attenuating material systems pose a challenge for attenuation-contrast tomography. Furthermore, combining SXRD and SRXTM can be used to correlate processes occurring at the atomic level in the crystal lattices of the active materials with those at the scale of electrode microstructure. To demonstrate the benefits of this approach, we investigate a silicon powder electrode in lithium metal half-cell configuration. Combining SXRD and SRXTM, we are able to (i) quantify the dissolution of the metallic lithium electrode and the expansion of the silicon electrode, (ii) better understand the formation of the Li15Si4 phase, and (iii) non-invasively probe kinetic limitations within the silicon electrode. A simple model based on the 1D diffusion equation allows us to qualitatively understand the observed kinetics and demonstrates why high-capacity electrodes are more prone to inhomogeneous lithiation reactions. PMID:27324109

Combining operando synchrotron X-ray tomographic microscopy and scanning X-ray diffraction to study lithium ion batteries

NASA Astrophysics Data System (ADS)

Pietsch, Patrick; Hess, Michael; Ludwig, Wolfgang; Eller, Jens; Wood, Vanessa

2016-06-01

We present an operando study of a lithium ion battery combining scanning X-ray diffraction (SXRD) and synchrotron radiation X-ray tomographic microscopy (SRXTM) simultaneously for the first time. This combination of techniques facilitates the investigation of dynamic processes in lithium ion batteries containing amorphous and/or weakly attenuating active materials. While amorphous materials pose a challenge for diffraction techniques, weakly attenuating material systems pose a challenge for attenuation-contrast tomography. Furthermore, combining SXRD and SRXTM can be used to correlate processes occurring at the atomic level in the crystal lattices of the active materials with those at the scale of electrode microstructure. To demonstrate the benefits of this approach, we investigate a silicon powder electrode in lithium metal half-cell configuration. Combining SXRD and SRXTM, we are able to (i) quantify the dissolution of the metallic lithium electrode and the expansion of the silicon electrode, (ii) better understand the formation of the Li15Si4 phase, and (iii) non-invasively probe kinetic limitations within the silicon electrode. A simple model based on the 1D diffusion equation allows us to qualitatively understand the observed kinetics and demonstrates why high-capacity electrodes are more prone to inhomogeneous lithiation reactions.

Scalable Dry Printing Manufacturing to Enable Long-Life and High Energy Lithium-Ion Batteries

DOE PAGES

Liu, Jin; Ludwig, Brandon; Liu, Yangtao; ...

2017-08-22

Slurry casting method dominates the electrode manufacture of lithium-ion batteries. The entire procedure is similar to the newspaper printing that includes premixing of cast materials into solvents homogeneously, and continuously transferring and drying the slurry mixture onto the current collector. As a market approaching US $80 billion by 2024, the optimization of manufacture process is crucial and attractive. However, the organic solvent remains irreplaceable in the wet method for making slurries, even though it is capital-intensive and toxic. In this paper, an advanced powder printing technique is demonstrated that is completely solvent-free and dry. Through removing the solvent and relatedmore » procedures, this method is anticipated to statistically save 20% of the cost at a remarkably shortened production cycle (from hours to minutes). The dry printed electrodes outperform commercial slurry cast ones in 650 cycles (80% capacity retention in 500 cycles), and thick electrodes are successfully fabricated to increase the energy density. Furthermore, microscopy techniques are utilized to characterize the difference of electrode microstructure between dry and wet methods, and distinguish dry printing's advantages on controlling the microstructure. Finally, this study proves a practical fabrication method for lithium-ion electrodes with lowered cost and favorable performance, and allows more advanced electrode designs potentially.« less

Electrophoretic deposition of thermites onto micro-engineered electrodes prepared by direct-ink writing.

PubMed

Sullivan, K T; Zhu, C; Tanaka, D J; Kuntz, J D; Duoss, E B; Gash, A E

2013-02-14

This work combines electrophoretic deposition (EPD) with direct-ink writing (DIW) to prepare thin films of Al/CuO thermites onto patterned two- and three-dimensional silver electrodes. DIW was used to write the electrodes using a silver nanoparticle ink, and EPD was performed in a subsequent step to deposit the thermite onto the conductive electrodes. Unlike conventional lithographic techniques, DIW is a low-cost and versatile alternative to print fine-featured electrodes, and adds the benefit of printing self-supported three-dimensional structures. EPD provides a method for depositing the composite thermite only onto the conductive electrodes, and with controlled thicknesses, which provides fine spatial and mass control, respectively. EPD has previously been shown to produce well-mixed thermite composites which can pack to reasonably high densities without the need for any postprocessing. Homogeneous mixing is particularly important in reactive composities, where good mixing can enhance the reaction kinetics by decreasing the transport distance between the components. Several two- and three-dimensional designs were investigated to highlight the versatility of using DIW and EPD together. In addition to energetic applications, we anticipate that this combination of techniques will have a variety of other applications, which would benefit from the controlled placement of a thin film of one material onto a conductive architecture of a second material.

Scalable Dry Printing Manufacturing to Enable Long-Life and High Energy Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jin; Ludwig, Brandon; Liu, Yangtao

Slurry casting method dominates the electrode manufacture of lithium-ion batteries. The entire procedure is similar to the newspaper printing that includes premixing of cast materials into solvents homogeneously, and continuously transferring and drying the slurry mixture onto the current collector. As a market approaching US $80 billion by 2024, the optimization of manufacture process is crucial and attractive. However, the organic solvent remains irreplaceable in the wet method for making slurries, even though it is capital-intensive and toxic. In this paper, an advanced powder printing technique is demonstrated that is completely solvent-free and dry. Through removing the solvent and relatedmore » procedures, this method is anticipated to statistically save 20% of the cost at a remarkably shortened production cycle (from hours to minutes). The dry printed electrodes outperform commercial slurry cast ones in 650 cycles (80% capacity retention in 500 cycles), and thick electrodes are successfully fabricated to increase the energy density. Furthermore, microscopy techniques are utilized to characterize the difference of electrode microstructure between dry and wet methods, and distinguish dry printing's advantages on controlling the microstructure. Finally, this study proves a practical fabrication method for lithium-ion electrodes with lowered cost and favorable performance, and allows more advanced electrode designs potentially.« less

Automatic localization of cochlear implant electrodes in CTs with a limited intensity range

NASA Astrophysics Data System (ADS)

Zhao, Yiyuan; Dawant, Benoit M.; Noble, Jack H.

2017-02-01

Cochlear implants (CIs) are neural prosthetics for treating severe-to-profound hearing loss. Our group has developed an image-guided cochlear implant programming (IGCIP) system that uses image analysis techniques to recommend patientspecific CI processor settings to improve hearing outcomes. One crucial step in IGCIP is the localization of CI electrodes in post-implantation CTs. Manual localization of electrodes requires time and expertise. To automate this process, our group has proposed automatic techniques that have been validated on CTs acquired with scanners that produce images with an extended range of intensity values. However, there are many clinical CTs acquired with a limited intensity range. This limitation complicates the electrode localization process. In this work, we present a pre-processing step for CTs with a limited intensity range and extend the methods we proposed for full intensity range CTs to localize CI electrodes in CTs with limited intensity range. We evaluate our method on CTs of 20 subjects implanted with CI arrays produced by different manufacturers. Our method achieves a mean localization error of 0.21mm. This indicates our method is robust for automatic localization of CI electrodes in different types of CTs, which represents a crucial step for translating IGCIP from research laboratory to clinical use.

A biofilm microreactor system for simultaneous electrochemical and nuclear magnetic resonance techniques.

PubMed

Renslow, R S; Babauta, J T; Majors, P D; Mehta, H S; Ewing, R J; Ewing, T W; Mueller, K T; Beyenal, H

2014-01-01

Nuclear magnetic resonance (NMR) techniques are ideally suited for the study of biofilms and for probing their microenvironments because these techniques allow for noninvasive interrogation and in situ monitoring with high resolution. By combining NMR with simultaneous electrochemical techniques, it is possible to sustain and study live biofilms respiring on electrodes. Here, we describe a biofilm microreactor system, including a reusable and a disposable reactor, that allows for simultaneous electrochemical and NMR techniques (EC-NMR) at the microscale. Microreactors were designed with custom radio frequency resonator coils, which allowed for NMR measurements of biofilms growing on polarized gold electrodes. For an example application of this system we grew Geobacter sulfurreducens biofilms on electrodes. EC-NMR was used to investigate growth medium flow velocities and depth-resolved acetate concentration inside the biofilm. As a novel contribution we used Monte Carlo error analysis to estimate the standard deviations of the acetate concentration measurements. Overall, we found that the disposable EC-NMR microreactor provided a 9.7 times better signal-to-noise ratio over the reusable reactor. The EC-NMR biofilm microreactor system can ultimately be used to correlate extracellular electron transfer rates with metabolic reactions and explore extracellular electron transfer mechanisms.

Place-pitch manipulations with cochlear implants

PubMed Central

Macherey, Olivier; Carlyon, Robert P.

2012-01-01

Pitch can be conveyed to cochlear implant (CI) listeners via both place of excitation and temporal cues. The transmission of place cues may be hampered by several factors including limitations on the insertion depth and number of implanted electrodes, and the broad current spread produced by monopolar stimulation. The following series of experiments investigate several methods to partially overcome these limitations. Experiment 1 compares two recently published techniques that aim to activate more apical fibers than produced by monopolar or bipolar stimulation of the most apical contacts. The first technique (phantom stimulation) manipulates the current spread by simultaneously stimulating two electrodes with opposite-polarity pulses of different amplitudes. The second technique manipulates the neural spread of excitation by using asymmetric pulses and exploiting the polarity-sensitive properties of auditory nerve fibers. The two techniques yielded similar results and were shown to produce lower place pitch percepts than stimulation of monopolar and bipolar symmetric pulses. Furthermore, combining these two techniques may be advantageous in a clinical setting. Experiment 2 proposes a novel method to create place pitches intermediate to those produced by physical electrodes by using charge-balanced asymmetric pulses in bipolar mode with different degrees of asymmetry. PMID:22423718

Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion.

PubMed

Greene, Nathaniel T; Mattingly, Jameson K; Banakis Hartl, Renee M; Tollin, Daniel J; Cass, Stephen P

2016-12-01

Cochlear implant (CI) electrode insertion into the round window induces pressure transients in the cochlear fluid comparable to high-intensity sound transients. Many patients receiving a CI have some remaining functional hearing at low frequencies; thus, devices and surgical techniques have been developed to use this residual hearing. To maintain functional acoustic hearing, it is important to retain function of any hair cells and auditory nerve fibers innervating the basilar membrane; however, in a subset of patients, residual low-frequency hearing is lost after CI insertion. Here, we test the hypothesis that transient intracochlear pressure spikes are generated during CI electrode insertion, which could cause damage and compromise residual hearing. Human cadaveric temporal bones were prepared with an extended facial recess. Pressures in the scala vestibuli and tympani were measured with fiber-optic pressure sensors inserted into the cochlea near the oval and round windows, whereas CI electrodes (five styles from two manufacturers) were inserted into the cochlea via a round window approach. Pressures in the scala tympani tended to be larger in magnitude than pressures in the scala vestibuli, consistent with electrode insertion into the scala tympani. CI electrode insertion produced a range of pressure transients in the cochlea that could occur alone or as part of a train of spikes with equivalent peak sound pressure levels in excess of 170 dB sound pressure level. Instances of pressure transients varied with electrode styles. Results suggest electrode design, insertion mechanism, and surgical technique affect the magnitude and rate of intracochlear pressure transients during CI electrode insertion. Pressure transients showed intensities similar to those elicited by high-level sounds and thus could cause damage to the basilar membrane and/or hair cells.

Intracochlear pressure transients during cochlear implant electrode insertion

PubMed Central

Greene, Nathaniel T.; Mattingly, Jameson K.; Banakis Hartl, Renee M.; Tollin, Daniel J.; Cass, Stephen P.

2016-01-01

Hypothesis Cochlear implant (CI) electrode insertion into the round window induces pressure transients in the cochlear fluid comparable to high intensity sound transients. Background Many patients receiving a CI have some remaining functional hearing at low frequencies, thus devices and surgical techniques have been developed to utilize this residual hearing. To maintain functional acoustic hearing, it is important to retain function of any hair cells and auditory nerve fibers innervating the basilar membrane; however, in a subset of patients, residual low frequency hearing is lost following CI insertion. Here, we test the hypothesis that transient intracochlear pressure spikes are generated during CI electrode insertion, which could cause damage and compromise residual hearing. Methods Human cadaveric temporal bones were prepared with an extended facial recess. Pressures in the scala vestibuli (PSV) and tympani (PST) were measured with fiber-optic pressure sensors inserted into the cochlea near the oval and round windows while CI electrodes (five styles from two manufacturers) were inserted into the cochlea via a round window approach. Results PST tended to be larger in magnitude than PSV, consistent with electrode insertion into the scala tympani. CI electrode insertion produced a range of pressure transients in the cochlea that could occur alone or as part of a train of spikes with equivalent peak sound pressure levels in excess of 170dB SPL. Instances of pressure transients varied with electrode styles. Conclusions Results suggest electrode design, insertion mechanism, and surgical technique affect the magnitude and rate of intracochlear pressure transients during CI electrode insertion. Pressure transients showed intensities similar to those elicited by high level sounds and thus could cause damage to the basilar membrane and/or hair cells. PMID:27753703

Electrocatalytic oxidation of Epinephrine and Norepinephrine at metal oxide doped phthalocyanine/MWCNT composite sensor

PubMed Central

Mphuthi, Ntsoaki G.; Adekunle, Abolanle S.; Ebenso, Eno E.

2016-01-01

Glassy carbon electrode (GCE) was modified with metal oxides (MO = Fe3O4, ZnO) nanoparticles doped phthalocyanine (Pc) and functionalized MWCNTs, and the electrocatalytic properties were studied. Successful synthesis of the metal oxide nanoparticles and the MO/Pc/MWCNT composite were confirmed using FTIR, Raman and SEM techniques. The electrodes were characterized using cyclic voltammetry (CV) technique. The electrocatalytic behaviour of the electrode towards epinephrine (EP) and norepinephrine (NE) oxidation was investigated using CV and DPV. Result showed that GCE-MWCNT/Fe3O4/2,3-Nc, GCE-MWCNT/Fe3O429H,31H-Pc, GCE-MWCNT/ZnO/2,3-Nc and GCE-MWCNT/ZnO/29H,31H-Pc electrodes gave enhanced EP and NE current response. Stability study indicated that the four GCE-MWCNT/MO/Pc modified electrodes were stable against electrode fouling effect with the percentage NE current drop of 5.56–5.88% after 20 scans. GCE-MWCNT/Fe3O4/29H,31H-Pc gave the lowest limit of detection (4.6 μM) towards EP while MWCNT/ZnO/29H,31H-Pc gave the lowest limit of detection (1.7 μM) towards NE. The limit of detection and sensitivity of the electrodes compared well with literature. Electrocatalytic oxidation of EP and NE on GCE-MWCNT/MO/Pc electrodes was diffusion controlled with some adsorption of electro-oxidation reaction intermediates products. The electrodes were found to be electrochemically stable, reusable and can be used for the analysis of EP and NE in real life samples. PMID:27245690

TiN coated aluminum electrodes for DC high voltage electron guns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamun, Md Abdullah A.; Elmustafa, Abdelmageed A.; Taus, Rhys

Preparing electrodes made of metals like stainless steel, for use inside DC high voltage electron guns, is a labor-intensive and time-consuming process. In this paper, the authors report the exceptional high voltage performance of aluminum electrodes coated with hard titanium nitride (TiN). The aluminum electrodes were comparatively easy to manufacture and required only hours of mechanical polishing using silicon carbide paper, prior to coating with TiN by a commercial vendor. The high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, was compared to that of bare aluminum electrodes, and electrodes manufactured from titanium alloymore » (Ti-6AI-4V). Following gas conditioning, each TiN-coated aluminum electrode reached -225 kV bias voltage while generating less than 100 pA of field emission (<10 pA) using a 40 mm cathode/anode gap, corresponding to field strength of 13.7 MV/m. Smaller gaps were studied to evaluate electrode performance at higher field strength with the best performing TiN-coated aluminum electrode reaching ~22.5 MV/m with field emission less than 100 pA. These results were comparable to those obtained from our best-performing electrodes manufactured from stainless steel, titanium alloy and niobium, as reported in references cited below. The TiN coating provided a very smooth surface and with mechanical properties of the coating (hardness and modulus) superior to those of stainless steel, titanium-alloy, and niobium electrodes. These features likely contributed to the improved high voltage performance of the TiN-coated aluminum electrodes.« less

TiN coated aluminum electrodes for DC high voltage electron guns

DOE PAGES

Mamun, Md Abdullah A.; Elmustafa, Abdelmageed A.; Taus, Rhys; ...

2015-05-01

Preparing electrodes made of metals like stainless steel, for use inside DC high voltage electron guns, is a labor-intensive and time-consuming process. In this paper, the authors report the exceptional high voltage performance of aluminum electrodes coated with hard titanium nitride (TiN). The aluminum electrodes were comparatively easy to manufacture and required only hours of mechanical polishing using silicon carbide paper, prior to coating with TiN by a commercial vendor. The high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, was compared to that of bare aluminum electrodes, and electrodes manufactured from titanium alloymore » (Ti-6AI-4V). Following gas conditioning, each TiN-coated aluminum electrode reached -225 kV bias voltage while generating less than 100 pA of field emission (<10 pA) using a 40 mm cathode/anode gap, corresponding to field strength of 13.7 MV/m. Smaller gaps were studied to evaluate electrode performance at higher field strength with the best performing TiN-coated aluminum electrode reaching ~22.5 MV/m with field emission less than 100 pA. These results were comparable to those obtained from our best-performing electrodes manufactured from stainless steel, titanium alloy and niobium, as reported in references cited below. The TiN coating provided a very smooth surface and with mechanical properties of the coating (hardness and modulus) superior to those of stainless steel, titanium-alloy, and niobium electrodes. These features likely contributed to the improved high voltage performance of the TiN-coated aluminum electrodes.« less

Design, fabrication and skin-electrode contact analysis of polymer microneedle-based ECG electrodes

NASA Astrophysics Data System (ADS)

O'Mahony, Conor; Grygoryev, Konstantin; Ciarlone, Antonio; Giannoni, Giuseppe; Kenthao, Anan; Galvin, Paul

2016-08-01

Microneedle-based ‘dry’ electrodes have immense potential for use in diagnostic procedures such as electrocardiography (ECG) analysis, as they eliminate several of the drawbacks associated with the conventional ‘wet’ electrodes currently used for physiological signal recording. To be commercially successful in such a competitive market, it is essential that dry electrodes are manufacturable in high volumes and at low cost. In addition, the topographical nature of these emerging devices means that electrode performance is likely to be highly dependent on the quality of the skin-electrode contact. This paper presents a low-cost, wafer-level micromoulding technology for the fabrication of polymeric ECG electrodes that use microneedle structures to make a direct electrical contact to the body. The double-sided moulding process can be used to eliminate post-process via creation and wafer dicing steps. In addition, measurement techniques have been developed to characterize the skin-electrode contact force. We perform the first analysis of signal-to-noise ratio dependency on contact force, and show that although microneedle-based electrodes can outperform conventional gel electrodes, the quality of ECG recordings is significantly dependent on temporal and mechanical aspects of the skin-electrode interface.

Characterizing nonlinearity in invasive EEG recordings from temporal lobe epilepsy

NASA Astrophysics Data System (ADS)

Casdagli, M. C.; Iasemidis, L. D.; Sackellares, J. C.; Roper, S. N.; Gilmore, R. L.; Savit, R. S.

Invasive electroencephalographic (EEG) recordings from depth and subdural electrodes, performed in eight patients with temporal lobe epilepsy, are analyzed using a variety of nonlinear techniques. A surrogate data technique is used to find strong evidence for nonlinearities in epileptogenic regions of the brain. Most of these nonlinearities are characterized as “spiking” by a wavelet analysis. A small fraction of the nonlinearities are characterized as “recurrent” by a nonlinear prediction algorithm. Recurrent activity is found to occur in spatio-temporal patterns related to the location of the epileptogenic focus. Residual delay maps, used to characterize “lag-one nonlinearity”, are remarkably stationary for a given electrode, and exhibit striking variations among electrodes. The clinical and theoretical implications of these results are discussed.

Sensor Level Functional Connectivity Topography Comparison Between Different References Based EEG and MEG.

PubMed

Huang, Yunzhi; Zhang, Junpeng; Cui, Yuan; Yang, Gang; Liu, Qi; Yin, Guangfu

2018-01-01

Sensor-level functional connectivity topography (sFCT) contributes significantly to our understanding of brain networks. sFCT can be constructed using either electroencephalography (EEG) or magnetoencephalography (MEG). Here, we compared sFCT within the EEG modality and between EEG and MEG modalities. We first used simulations to look at how different EEG references-including the Reference Electrode Standardization Technique (REST), average reference (AR), linked mastoids (LM), and left mastoid references (LR)-affect EEG-based sFCT. The results showed that REST decreased the reference effects on scalp EEG recordings, making REST-based sFCT closer to the ground truth (sFCT based on ideal recordings). For the inter-modality simulation comparisons, we compared each type of EEG-sFCT with MEG-sFCT using three metrics to quantize the differences: Relative Error (RE), Overlap Rate (OR), and Hamming Distance (HD). When two sFCTs are similar, RE and HD are low, while OR is high. Results showed that among all reference schemes, EEG-and MEG-sFCT were most similar when the EEG was REST-based and the EEG and MEG were recorded simultaneously. Next, we analyzed simultaneously recorded MEG and EEG data from publicly available face-recognition experiments using a similar procedure as in the simulations. The results showed (1) if MEG-sFCT is the standard, REST-and LM-based sFCT provided results closer to this standard in the terms of HD; (2) REST-based sFCT and MEG-sFCT had the highest similarity in terms of RE; (3) REST-based sFCT had the most overlapping edges with MEG-sFCT in terms of OR. This study thus provides new insights into the effect of different reference schemes on sFCT and the similarity between MEG and EEG in terms of sFCT.

Trace level voltammetric determination of heavy metals and total mercury in tea matrices (Camellia sinensis).

PubMed

Melucci, Dora; Locatelli, Marcello; Locatelli, Clinio

2013-12-01

An analytical procedure regarding the voltammetric determination of mercury(II), copper(II), lead(II), cadmium(II) and zinc(II) by square wave anodic stripping voltammetry (SWASV) in matrices involved in food chain is proposed. In particular, tea leaves were analyzed as real samples. The digestion of each matrix was carried out using a concentrated HCl-HNO3-H2SO4 acidic attack mixture; 0.01 mol L(-1) EDTA-Na2+ 0.15 mol L(-1) NaCl + 0.5 mol L(-1) HCl was employed as the supporting electrolyte. The voltammetric measurements were carried out using a conventional three electrode cell, employing, as working electrodes, a gold electrode (GE) and a stationary hanging mercury drop electrode (HMDE). The analytical procedure has been verified on the standard reference materials Spinach Leaves NIST-SRM 1570a, Tomato Leaves NIST-SRM 1573a and Apple Leaves NIST-SRM 1515. For all the elements, the precision as repeatability, expressed as relative standard deviation (sr) was of the order of 3-5%, while the trueness, expressed as relative error (e) was of the order of 3-7%. Once set up on the standard reference materials, the analytical procedure was applied to commercial tea leaves samples. A critical comparison with spectroscopic measurements is also discussed.

A modified ion-selective electrode method for measurement of chloride in sweat.

PubMed

Finley, P R; Dye, J A; Lichti, D A; Byers, J M; Williams, R J

1978-06-01

A modified method of analysis of sweat chloride concentration with an ion-selective electrode is presented. The original method of sweat chloride analysis proposed by the Orion Research Corporation (Cambridge, Massachusetts 02139) is inadequate because it produces erratic and misleading results. The modified method was compared with the reference quantitative method of Gibson and Cooke. In the modified method, individual electrode pads are cut and placed in the electrodes rather than using the pads supplied by the company; pilocarpine nitrate (2,000 mg/l) is used in place of pilocarpine HCl (640 mg/l); sodium bicarbonate as the weak electrolyte is used instead of K2SO4. A 10-minute period for sweat accumulation is employed rather than a zero-time collection as in the original Orion method. The modification has been studied for reproducibility in individuals, reproducibility between right and left arm in individuals; it has been compared extensively with the quantitative method of Gibson and Cooke, both in normal individuals and in patients with cystic fibrosis. There is excellent agreement between the modified method and the quantitative reference method. There appears to be a slight bias toward higher concentrations of chloride from the right arm compared with the left arm, but this difference is not medically significant.

Microfabricated FSCV-Compatible Microelectrode Array for Real-time Monitoring of Heterogeneous Dopamine Release

PubMed Central

Zachek, Matthew K.; Park, Jinwoo; Takmakov, Pavel; Wightman, R. Mark; McCarty, Gregory S.

2010-01-01

Fast scan cyclic voltammetry (FSCV) has been used previously to detect neurotransmitter release and reuptake in vivo. An advantage that FSCV has over other electrochemical techniques is its ability to distinguish neurotransmitters of interest (i.e. monoamines) from their metabolites using their respective characteristic cyclic voltammogram. While much has been learned with this technique, it has generally only been used in a single working electrode arrangement. Additionally, traditional electrode fabrication techniques tend to be difficult and somewhat irreproducible. Described in this report is a fabrication method for a FSCV compatible microelectrode array (FSCV-MEA) that is capable of functioning in vivo. The microfabrication techniques employed here allow for better reproducibility than traditional fabrication methods of carbon fiber microelectrodes, and enable batch fabrication of electrode arrays. The reproducibility and electrochemical qualities of the probes were assessed along with cross talk in vitro. Heterogeneous release of electrically stimulated dopamine was observed in real-time in the striatum of an anesthetized rat using the FSCV-MEA. The heterogeneous effects of pharmacology on the striatum was also observed and shown to be consistent across multiple animals. PMID:20464031

Surface mapping of spike potential fields: experienced EEGers vs. computerized analysis.

PubMed

Koszer, S; Moshé, S L; Legatt, A D; Shinnar, S; Goldensohn, E S

1996-03-01

An EEG epileptiform spike focus recorded with scalp electrodes is clinically localized by visual estimation of the point of maximal voltage and the distribution of its surrounding voltages. We compared such estimated voltage maps, drawn by experienced electroencephalographers (EEGers), with a computerized spline interpolation technique employed in the commercially available software package FOCUS. Twenty-two spikes were recorded from 15 patients during long-term continuous EEG monitoring. Maps of voltage distribution from the 28 electrodes surrounding the points of maximum change in slope (the spike maximum) were constructed by the EEGer. The same points of maximum spike and voltage distributions at the 29 electrodes were mapped by computerized spline interpolation and a comparison between the two methods was made. The findings indicate that the computerized spline mapping techniques employed in FOCUS construct voltage maps with similar maxima and distributions as the maps created by experienced EEGers. The dynamics of spike activity, including correlations, are better visualized using the computerized technique than by manual interpretation alone. Its use as a technique for spike localization is accurate and adds information of potential clinical value.

A novel method of placing right ventricular leads in patients with persistent left superior vena cava using a conventional j stylet.

PubMed

Mora, Guillermo

2014-03-01

Locating pacemaker electrodes can become complicated by congenital abnormalities such as persistent left superior vena cava (LSVC). To evaluate a technique for the implanting of ventricular electrode in patients with persistent LSVC. The study was carried out from June 2001 to June 2010 involving all patients who were admitted to the Hospital Universitario Mayor, Instituto de Corazon de Bogota and Hospital Universitario Clinica San Rafael (Bogota-Colombia) for implanting pacemakers or cardiac defibrillators. LSVC was diagnosed by fluoroscopic observation (anterior-posterior view) of the course of the stylet. Four steps were followed: 1) Move the electrode with a straight stylet to the right atrium. 2) Change the straight stylet by a conventional J stylet and push the electrode to the lateral or anterolateral wall of the right atrium. 3) Remove the guide 3-5 cm and 4) Push the electrode which crosses the tricuspid valve into the right ventricle and finally deploy the active fixation mechanism. A total of 1198 patients were admitted for pacemaker or cardiac defibrillator implant during the 9-year study period, 1114 received a left subclavian venous approach. There were 573 males and 541 females. Persistent LSVC was found in five patients (0.45%) Fluoroscopy time for implanting the ventricular electrode ranged from 60 to 250 seconds, 40 to 92 minutes being taken to complete the whole procedure. We present a simple and rapid technique for electrode placement in patients with LSVC using usual J guide and active fixation electrodes with high success.

Electrolytic treatment of colorectal liver tumour deposits in a rat model: a technique with potential for patients with unresectable liver tumours.

PubMed

Wemyss-Holden, S A; Robertson, G S; Hall, P D; Dennison, A R; Maddern, G J

2000-01-01

Patients with unresectable malignant liver tumours have a poor prognosis. A technique is needed which improves long-term survival. Previous studies in the rat have shown that electrolysis is a safe, predictable and reproducible method for creating areas of necrosis in the normal rat liver. This study examined the effects of electrolysis on colorectal liver 'metastases' in the rat. Tumours of colorectal origin were implanted into the livers of Wistar-WAG rats. Two weeks after implantation the tumours were treated with electrolysis. A direct current generator, connected to 2 platinum intrahepatic electrodes was used to examine the effects of various electrode configurations on the extent of tumour necrosis. Significant (p<0.001) tumour ablation was achieved with all electrode configurations. Tumour necrosis was more complete (p<0.05) with the electrodes positioned on either side of the tumour than with both electrodes placed in the centre of the tumour. Liver enzymes (AST and ALT) were significantly (p<0.001) elevated after treatment, but returned towards normal by 2 days. This study has shown that colorectal liver 'metastasis' can be ablated by electrolysis in a rat model. Two separate mechanisms of tumour ablation were observed: With the electrodes directly in or adjacent to the tumour, necrosis resulted from the action of cytotoxic electrode products, whereas by positioning the electrodes proximal to the tumour, necrosis was induced by a 'secondary' ischaemic effect. The findings confirm the view that electrolysis has great potential for treating patients with unresectable malignant liver tumours.

Molybdenum oxide electrodes for thermoelectric generators

DOEpatents

Schmatz, Duane J.

1989-01-01

The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a thin film comprising molybdenum oxide as an electrode deposited by physical deposition techniques onto solid electrolyte. The invention is also directed to the method of making same.

Assessing a novel polymer-wick based electrode for EEG neurophysiological research.

PubMed

Pasion, Rita; Paiva, Tiago O; Pedrosa, Paulo; Gaspar, Hugo; Vasconcelos, Beatriz; Martins, Ana C; Amaral, Maria H; Nóbrega, João M; Páscoa, Ricardo; Fonseca, Carlos; Barbosa, Fernando

2016-07-15

The EEG technique has decades of valid applications in clinical and experimental neurophysiology. EEG equipment and data analysis methods have been characterized by remarkable developments, but the skin-to-electrode signal transfer remains a challenge for EEG recording. A novel quasi-dry system - the polymer wick-based electrode - was developed to overcome the limitations of conventional dry and wet silver/silver-chloride (Ag/AgCl) electrodes for EEG recording. Nine participants completed an auditory oddball protocol with simultaneous EEG acquisition using both the conventional Ag/AgCl and the wick electrodes. Wick system successfully recorded the expected P300 modulation. Standard ERP analysis, residual random noise analysis, and single-trial analysis of the P300 wave were performed in order to compare signal acquired by both electrodes. It was found that the novel wick electrode performed similarly to the conventional Ag/AgCl electrodes. The developed wick electrode appears to be a reliable alternative for EEG research, representing a promising halfway alternative between wet and dry electrodes. Copyright © 2016 Elsevier B.V. All rights reserved.

Active Electrodes for Wearable EEG Acquisition: Review and Electronics Design Methodology.

PubMed

Xu, Jiawei; Mitra, Srinjoy; Van Hoof, Chris; Yazicioglu, Refet Firat; Makinwa, Kofi A A

2017-01-01

Active electrodes (AEs), i.e., electrodes with built-in readout circuitry, are increasingly being implemented in wearable healthcare and lifestyle applications due to AEs' robustness to environmental interference. An AE locally amplifies and buffers μV-level EEG signals before driving any cabling. The low output impedance of an AE mitigates cable motion artifacts, thus enabling the use of high-impedance dry electrodes for greater user comfort. However, developing a wearable EEG system, with medical grade signal quality on noise, electrode offset tolerance, common-mode rejection ratio, input impedance, and power dissipation, remains a challenging task. This paper reviews state-of-the-art bio-amplifier architectures and low-power analog circuits design techniques intended for wearable EEG acquisition, with a special focus on an AE system interfaced with dry electrodes.

Improved lifetime high voltage switch electrode

NASA Astrophysics Data System (ADS)

Halverson, W.

1985-06-01

In this Phase 1 Small Business Innovation Research (SBIR) program, preliminary tests of ion implantation to increase the lifetime of spark switch electrodes have indicated that a 185 keV carbon ion implant into a tungsten-copper composite has reduced electrode erosion by a factor of two to four. Apparently, the thin layer of tungsten carbide (WC) has better thermal properties than pure tungsten; the WC may have penetrated into the unimplanted body of the electrode by liquid and/or solid phase diffusion during erosion testing. These encouraging results should provide the basis for a Phase 2 SBIR program to investigate further the physical and chemical effects of ion implantation on spark gap electrodes and to optimize the technique for applications.

Composite substrate for bipolar electrodes

DOEpatents

Tekkanat, B.; Bolstad, J.J.

1992-12-22

Substrates for electrode systems, particularly those to be used for bipolar electrodes in zinc-bromine batteries, are disclosed. The substrates preferably include carbon-black as a conductive filler in a polymeric matrix, with reinforcing materials such as glass fibers. Warpage of the zinc-bromine electrodes which was experienced in the prior art and which was believed to be caused by physical expansion of the electrodes due to bromine absorption by the carbon-black, is substantially eliminated when new substrate fabrication techniques are employed. In the present invention, substrates are prepared using a lamination process known as glass mat reinforced thermoplastics technology or, in an alternate embodiment, the substrate is made using a slurry process. 4 figs.

Preparation of AN Electrode Modified with a Thermostable Enzyme BACILLUS Subtilis COTA by Electrodeposition

NASA Astrophysics Data System (ADS)

Watanabe, Toshio; Yamada, Yohei; Motonaka, Junko; Yabutani, Tomoki; Sakuraba, Haruhiko; Yasuzawa, Mikito

In this study, electrodeposition of thermostable enzyme Bacillus subtilis CotA, which is a laccase and has a bilirubin oxidase (BOD) activity, was investigated. The electrodeposition was operated in a mixture of Bacillus subtilis CotA in the PBS (pH 8.0) and TritonX-100 under applying potential (1100 mV vs. Ag/AgCl for 5 min.). The current response was measured by linear sweep voltammetry technique (LSV). The thermostable enzyme Bacillus subtilis CotA electrodeposited electrode was compared with a mesophile BOD electrodeposited electrode. As a result, the Bacillus subtilis CotA modified electrode showed better sensitivity and long-term stability than the mesophile BOD modified electrode.

Enhancement of the efficiency of dye-sensitized solar cell with multi-wall carbon nanotubes/polypyrrole composite counter electrodes prepared by electrophoresis/electrochemical polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Jun; Niu, Hai-jun; Wen, Hai-lin

2013-03-15

Graphical abstract: The overall energy conversion efficiency of the DSSC employing the MWCNT/PPy CE reached 3.78%. Compared with a reference DSSC using single MWCNT film CE with efficiency of 2.68%, the energy conversion efficiency was increased by 41.04%. Highlights: ► MWCNT/PPy composite film prepared by electrodeposition layer by layer was used as counter electrode in DSSC. ► The overall energy conversion efficiency of the DSSC was 3.78% by employing the composite film. ► The energy conversion efficiency increased by 41.04% compared with efficiency of 2.68% by using the single MWCNT film. ► We analyzed the mechanism and influence factor ofmore » electron transfer in the composite electrode by EIS. - Abstract: For the purpose of replacing the precious Pt counter electrode in dye-sensitized solar cells (DSSCs) with higher energy conversion efficiency, multi-wall carbon nanotube (MWCNT)/polypyrrole (PPy) double layers film counter electrode (CE) was fabricated by electrophoresis and cyclic voltammetry (CV) layer by layer. Atom force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscope (TEM) demonstrated the morphologies of the composite electrode and Raman spectroscopy verified the PPy had come into being. The overall energy conversion efficiency of the DSSC employing the MWCNT/PPy CE reached 3.78%. Compared with a reference DSSC using single MWCNT film CE with efficiency of 2.68%, the energy conversion efficiency was increased by 41.04%. The result of impedance showed that the charge transfer resistance R{sub ct} of the MWCNT/PPy CE had the lowest value compared to that of MWCNT or PPy electrode. These results indicate that the composite film with high conductivity, high active surface area, and good catalytic properties for I{sub 3}{sup −} reduction can potentially be used as the CE in a high-performance DSSC.« less

Zr/ZrO2 sensors for in situ measurement of pH in high-temperature and -pressure aqueous solutions.

PubMed

Zhang, R H; Zhang, X T; Hu, S M

2008-04-15

The aim of this study is to develop new pH sensors that can be used to test and monitor hydrogen ion activity in hydrothermal conditions. A Zr/ZrO2 oxidation electrode is fabricated for in situ pH measurement of high-temperature aqueous solutions. This sensor responds rapidly and precisely to pH over a wide range of temperature and pressure. The Zr/ZrO2 electrode was made by oxidizing zirconium metal wire with Na2CO3 melt, which produced a thin film of ZrO2 on its surface. Thus, an oxidation-reduction electrode was produced. The Zr/ZrO2 electrode has a good electrochemical stability over a wide range of pH in high-temperature aqueous solutions when used with a Ag/AgCl reference electrode. Measurements of the Zr/ZrO2 sensor potential against a Ag/AgCl reference electrode is shown to vary linearly with pH between temperatures 20 and 200 degrees C. The slope of the potential versus pH at high temperature is slightly below the theoretical value indicated by the Nernst equation; such deviation is attributed to the fact that the sensor is not strictly at equilibrium with the solution to be tested in a short period of time. The Zr/ZrO2 sensor can be calibrated over the conditions that exist in the natural deep-seawater. Our studies showed that the Zr/ZrO2 electrode is a suitable pH sensor for the hydrothermal systems at midocean ridge or other geothermal systems with the high-temperature environment. Yttria-stabilized zirconia sensors have also been used to investigate the pH of hydrothermal fluids in hot springs vents at midocean ridge. These sensors, however, are not sensitive below 200 degrees C. Zr/ZrO2 sensors have wider temperature range and can be severed as good alternative sensors for measuring the pH of hydrothermal fluids.

Measurement of absorbed dose with a bone-equivalent extrapolation chamber.

PubMed

DeBlois, François; Abdel-Rahman, Wamied; Seuntjens, Jan P; Podgorsak, Ervin B

2002-03-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to approximately 2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams.

Past, present and future of spike sorting techniques.

PubMed

Rey, Hernan Gonzalo; Pedreira, Carlos; Quian Quiroga, Rodrigo

2015-10-01

Spike sorting is a crucial step to extract information from extracellular recordings. With new recording opportunities provided by the development of new electrodes that allow monitoring hundreds of neurons simultaneously, the scenario for the new generation of algorithms is both exciting and challenging. However, this will require a new approach to the problem and the development of a common reference framework to quickly assess the performance of new algorithms. In this work, we review the basic concepts of spike sorting, including the requirements for different applications, together with the problems faced by presently available algorithms. We conclude by proposing a roadmap stressing the crucial points to be addressed to support the neuroscientific research of the near future. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Application of gas diffusion electrodes in bioelectrochemical syntheses and energy conversion.

PubMed

Horst, Angelika E W; Mangold, Klaus-Michael; Holtmann, Dirk

2016-02-01

Combining the advantages of biological components (e.g., reaction specificity, self-replication) and electrochemical techniques in bioelectrochemical systems offers the opportunity to develop novel efficient and sustainable processes for the production of a number of valuable products. The choice of electrode material has a great impact on the performance of bioelectrochemical systems. In addition to the redox process at the electrodes, interactions of biocatalysts with electrodes (e.g., enzyme denaturation or biofouling) need to be considered. In recent years, gas diffusion electrodes (GDEs) have proved to be very attractive electrodes for bioelectrochemical purposes. GDEs are porous electrodes, that posses a large three-phase boundary surface. At this interface, a solid catalyst supports the electrochemical reaction between gaseous and liquid phase. This mini-review discusses the application of GDEs in microbial and enzymatic fuel cells, for microbial electrolysis, in biosensors and for electroenzymatic synthesis reactions. © 2015 Wiley Periodicals, Inc.

Electrode behavior RE-visited: Monitoring potential windows, capacity loss, and impedance changes in Li 1.03 (Ni 0.5Co 0.2Mn 0.3) 0.97O 2/silicon-graphite full cells

DOE PAGES

Klett, Matilda; Gilbert, James A.; Trask, Stephen E.; ...

2016-03-04

Here, the capacity and power performance of lithium-ion battery cells evolve over time. The mechanisms leading to these changes can often be identified through knowledge of electrode potentials, which contain information about electrochemical processes at the electrode-electrolyte interfaces. In this study we monitor electrode potentials within full cells containing a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2–based (NCM523) positive electrode, a silicon-graphite negative electrode, and an LiPF6-bearing electrolyte, with and without fluoroethylene carbonate (FEC) or vinylene carbonate (VC) additives. The electrode potentials are monitored with a Li-metal reference electrode (RE) positioned besides the electrode stack; changes in these potentials aremore » used to examine electrode state-of-charge (SOC) shifts, material utilization, and loss of electrochemically active material. Electrode impedances are obtained with a Li xSn RE located within the stack; the data display the effect of cell voltage and electrode SOC changes on the measured values after formation cycling and after aging. Our measurements confirm the beneficial effect of FEC and VC electrolyte additives in reducing full cell capacity loss and impedance rise after cycling in a 3.0–4.2 V range. Comparisons with data from a full cell containing a graphite-based negative highlight the consequences of including silicon in the electrode. Our observations on electrode potentials, capacity, and impedance changes on cycling are crucial to designing long-lasting, silicon-bearing, lithium-ion cells.« less

Internal Reflection Spectra of Surface Compounds and Adsorbed Molecules

NASA Astrophysics Data System (ADS)

Zolotarev, V. M.; Lygin, V. I.; Tarasevich, B. N.

1981-01-01

The application of attenuated total reflection (ATR) spectroscopy in surface studies of inorganic adsorbents and catalysts, polymers, and optically transparent electrodes is discussed. The basic principles of ATR spectroscopy as applied to surface phenomena are considered, with special reference to thin films, industrial adsorbents and catalysts, and polymer degradation processes. 276 references.

Improved plaque materials for aerospace nickel-cadmium cells

NASA Technical Reports Server (NTRS)

Luksha, E.; Gordy, D. J.

1971-01-01

Improved cadmium electrode substrates with precisely controlled microstructures for possible use in aerospace nickel-cadmium cells were prepared. The preparative technique was a powder metallurgical process in which a fugitive pore-former and a nickel powder were blended, then isostatically compacted, and subsequently sintered. Cadmium electrodes prepared from such substrates were cycle tested using an accelerated tortuous test regime. It was discovered that plaques of 60% or 80% porosity prepared with a 25 micron pore-former were better than state-of-the-art electrodes in terms of efficienty and/or mechanical strength. The 60% structures were particularly outstanding in this respect in that they had efficiencies only 5-10 percentage points lower than state-of-the-art electrodes and vastly superior mechanical properties. This added strength was observed to eliminate cracking and physical degradation of the electrodes during processing and cycling. The cadmium electrodes prepared from the 80% porous substrates proved to be the best electrodes made during the course of the work from the point of view of highest efficiency. Three-point bend tests were used to measure mechanical properties of the plaques produced and also as a general characterization tool. In addition, the BET surface areas of selected specimens was determined. The SEM was used for judging microscopic uniformity and quantitatively determining the induced pore size and various other fine structures in the substrates. The technique of X-ray radiography was used to follow the bulk uniformity of the substrates at various stages of their processing.

Metal Oxides and Ion-Exchanging Surfaces as pH Sensors in Liquids: State-of-the-Art and Outlook

PubMed Central

Kurzweil, Peter

2009-01-01

Novel applications of online pH determinations at temperatures from -35 °C to 130 °C in technical and biological media, which are all but ideal aqueous solutions, require new approaches to pH monitoring. The glass electrode, introduced nearly hundred years ago, and chemical sensors based on field effect transistors (ISFET) show specific drawbacks with respect to handling and long-time stability. Proton sensitive metal oxides seem to be a promising and alternative to the state-of-the-art measuring methods, and might overcome some problems of classical hydrogen electrodes and reference electrodes. PMID:22408563

Characterization of reaction kinetics in a porous electrode

NASA Technical Reports Server (NTRS)

Fedkiw, Peter S.

1990-01-01

A continuum-model approach, analogous to porous electrode theory, was applied to a thin-layer cell of rectangular and cylindrical geometry. A reversible redox couple is assumed, and the local reaction current density is related to the potential through the formula of Hubbard and Anson for a uniformily accessible thin-layer cell. The placement of the reference electrode is also accounted for in the analysis. Primary emphasis is placed on the effect of the solution-phase ohmic potential drop on the voltammogram characteristics. Correlation equations for the peak-potential displacement from E(sup 0 prime) and the peak current are presented in terms of two dimensionless parameters.

The synthesis of multifunctional porous honey comb-like La2O3 thin film for supercapacitor and gas sensor applications.

PubMed

Yadav, A A; Lokhande, A C; Pujari, R B; Kim, J H; Lokhande, C D

2016-12-15

The porous honey comb-like La 2 O 3 thin films have been synthesized using one step spray pyrolysis method. The influence of sprayed solution quantity on properties of La 2 O 3 thin films is studied using X-ray diffraction, Fourier transform spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, optical absorption and Brunauer-Emmett-Teller techniques. Morphology of La 2 O 3 electrode is controlled with sprayed solution quantity. The supercapacitive properties of La 2 O 3 thin film electrode are investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance techniques. The La 2 O 3 film electrode exhibited the specific capacitance of the 166Fg -1 with 85% stability for the 3000 cycles. The La 2 O 3 film electrode exhibited sensitivity of 68 at 523K for 500ppm CO 2 gas concentration. The possible CO 2 sensing mechanism is discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Advances in radio frequency tumor ablation therapy: technical considerations, strategies for increasing coagulation necrosis volume, and preliminary clinical results

NASA Astrophysics Data System (ADS)

Goldberg, S. Nahum; Gazelle, G. Scott

1998-04-01

Radiofrequency (RF) tumor ablation has been demonstrated as a reliable method for creating thermally induced coagulation necrosis using either a percutaneous approach with image- guidance or direct surgical application of thin electrodes into treated tissues. Early clinical trials with this technology have studied the treatment of hepatic, cerebral, and bony malignancies. The extent of coagulation necrosis induced with conventional monopolar radiofrequency electrodes is dependent on overall energy deposition, the duration of RF application, and RF electrode tip length and gauge. This article will discuss these technical considerations with the goal of defining optimal parameters for RF ablation. Strategies to further increase induced coagulation necrosis including: multiprobe and bipolar arrays, and internally-cooled RF electrodes, with or without pulsed-RF or cluster technique will be presented. The development and laboratory results for many of these radiofrequency techniques, initial clinical results, and potential biophysical limitations to RF induced coagulation, such as perfusion mediated tissue cooling (vascular flow) will likewise be discussed.

Glucose Fuel Cells with a MicroChannel Fabricated on Flexible Polyimide Film

NASA Astrophysics Data System (ADS)

Sano, Ryohei; Fukushi, Yudai; Sasaki, Tsubasa; Mogi, Hiroshi; Koide, Syohei; Ikoma, Ryuta; Akatsuka, Wataru; Tsujimura, Seiya; Nishioka, Yasushiro

2013-12-01

In this work, a glucose fuel cell was fabricated using microfabrication processes assigned for microelectromechanical systems. The fuel cell was equipped with a microchannel to flow an aqueous solution of glucose. The cell was fabricated on a flexible polyimide substrate, and its porous carbon-coated aluminum (Al) electrodes of 2.8 mm in width and 11 mm in length were formed using photolithography and screen printing techniques. Porous carbon was deposited by screen printing of carbon black ink on the Al electrode surfaces in order to increase the effective electrode surface area and to absorb more enzymes on the electrode surfaces. The microchannel with a depth of 200 μm was fabricated using a hot embossing technique. A maximum power of 0.45 μW at 0.5 V that corresponds to a power density of 1.45 μW/cm2 was realized by introducing a 200 mM concentrated glucose solution at room temperature.

In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors

NASA Astrophysics Data System (ADS)

Griffin, John M.; Forse, Alexander C.; Tsai, Wan-Yu; Taberna, Pierre-Louis; Simon, Patrice; Grey, Clare P.

2015-08-01

Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results show that charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

On-chip collection of particles and cells by AC electroosmotic pumping and dielectrophoresis using asymmetric microelectrodes

PubMed Central

Melvin, Elizabeth M.; Moore, Brandon R.; Gilchrist, Kristin H.; Grego, Sonia; Velev, Orlin D.

2011-01-01

The recent development of microfluidic “lab on a chip” devices requiring sample sizes <100 μL has given rise to the need to concentrate dilute samples and trap analytes, especially for surface-based detection techniques. We demonstrate a particle collection device capable of concentrating micron-sized particles in a predetermined area by combining AC electroosmosis (ACEO) and dielectrophoresis (DEP). The planar asymmetric electrode pattern uses ACEO pumping to induce equal, quadrilateral flow directed towards a stagnant region in the center of the device. A number of system parameters affecting particle collection efficiency were investigated including electrode and gap width, chamber height, applied potential and frequency, and number of repeating electrode pairs and electrode geometry. The robustness of the on-chip collection design was evaluated against varying electrolyte concentrations, particle types, and particle sizes. These devices are amenable to integration with a variety of detection techniques such as optical evanescent waveguide sensing. PMID:22662040

Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures

NASA Astrophysics Data System (ADS)

Hu, Yang; Jiang, Yiliang; Jensen, Jens Oluf; Cleemann, Lars N.; Li, Qingfeng

2018-01-01

Phosphoric acid is the common electrolyte for high-temperature polymer electrolyte fuel cells (HT-PEMFCs) that have advantages such as enhanced CO tolerance and simplified heat and water management. The currently used rotating disk electrode technique is limited to tests in dilute solutions at low temperatures and hence is not suitable for catalyst evaluation for HT-PEMFCs. In this study, we have designed and constructed a half-cell setup to measure the intrinsic activities of catalysts towards the oxygen reduction reaction (ORR) in conditions close to HT-PEMFC cathodes. By optimization of the hydrophobic characteristics of electrodes and the catalyst layer thickness, ORR activities of typical Pt/C catalysts are successfully measured in concentrated phosphoric acid at temperatures above 100 °C. In terms of mass-specific activities, the catalyst exhibits about two times higher activity in the half-cell electrode than that observed in fuel cells, indicating the feasibility of the technique as well as the potential for further improvement of fuel cell electrode performance.

Synthesis of a fine neurological electrode by plasma polymerization processing.

PubMed

Cannon, J G; Dillon, R O; Bunshah, R F; Crandall, P H; Dymond, A M

1980-05-01

This research is part of a continuing program for the development of a coaxial depth electrode for research and diagnostic studies of neurological diseases. The requirements for this electrode include (1) strength and resistance to buckling sufficient to ensure self-forced penetration of brain tissue to a depth of 6 cm; (2) biocompatibility of the materials employed; (3) resistance to brittle fracture; and (4) a total diameter of less than 200 micrometer to minimize tissue damage. Earlier synthesis efforts using chemical vapor deposition techniques have been successful, although the process yield was 40% and an outer insulating layer had yet to be deposited. Plasma polymerization processes have been employed to realize an increase in the yield and provide an outer insulating layer. The starting material is W-26 at.% Re wire, nominally 125 micrometer in diameter. Hexamethyldisilazane(CH3)3SiNHSi(CH3)3 is used to deposit the insulating layers. The paper describes factors influencing the choice of materials, deposition techniques, and properties of electrodes.

iElectrodes: A Comprehensive Open-Source Toolbox for Depth and Subdural Grid Electrode Localization.

PubMed

Blenkmann, Alejandro O; Phillips, Holly N; Princich, Juan P; Rowe, James B; Bekinschtein, Tristan A; Muravchik, Carlos H; Kochen, Silvia

2017-01-01

The localization of intracranial electrodes is a fundamental step in the analysis of invasive electroencephalography (EEG) recordings in research and clinical practice. The conclusions reached from the analysis of these recordings rely on the accuracy of electrode localization in relationship to brain anatomy. However, currently available techniques for localizing electrodes from magnetic resonance (MR) and/or computerized tomography (CT) images are time consuming and/or limited to particular electrode types or shapes. Here we present iElectrodes, an open-source toolbox that provides robust and accurate semi-automatic localization of both subdural grids and depth electrodes. Using pre- and post-implantation images, the method takes 2-3 min to localize the coordinates in each electrode array and automatically number the electrodes. The proposed pre-processing pipeline allows one to work in a normalized space and to automatically obtain anatomical labels of the localized electrodes without neuroimaging experts. We validated the method with data from 22 patients implanted with a total of 1,242 electrodes. We show that localization distances were within 0.56 mm of those achieved by experienced manual evaluators. iElectrodes provided additional advantages in terms of robustness (even with severe perioperative cerebral distortions), speed (less than half the operator time compared to expert manual localization), simplicity, utility across multiple electrode types (surface and depth electrodes) and all brain regions.

iElectrodes: A Comprehensive Open-Source Toolbox for Depth and Subdural Grid Electrode Localization

PubMed Central

Blenkmann, Alejandro O.; Phillips, Holly N.; Princich, Juan P.; Rowe, James B.; Bekinschtein, Tristan A.; Muravchik, Carlos H.; Kochen, Silvia

2017-01-01

The localization of intracranial electrodes is a fundamental step in the analysis of invasive electroencephalography (EEG) recordings in research and clinical practice. The conclusions reached from the analysis of these recordings rely on the accuracy of electrode localization in relationship to brain anatomy. However, currently available techniques for localizing electrodes from magnetic resonance (MR) and/or computerized tomography (CT) images are time consuming and/or limited to particular electrode types or shapes. Here we present iElectrodes, an open-source toolbox that provides robust and accurate semi-automatic localization of both subdural grids and depth electrodes. Using pre- and post-implantation images, the method takes 2–3 min to localize the coordinates in each electrode array and automatically number the electrodes. The proposed pre-processing pipeline allows one to work in a normalized space and to automatically obtain anatomical labels of the localized electrodes without neuroimaging experts. We validated the method with data from 22 patients implanted with a total of 1,242 electrodes. We show that localization distances were within 0.56 mm of those achieved by experienced manual evaluators. iElectrodes provided additional advantages in terms of robustness (even with severe perioperative cerebral distortions), speed (less than half the operator time compared to expert manual localization), simplicity, utility across multiple electrode types (surface and depth electrodes) and all brain regions. PMID:28303098

Excess Heat in Molten Salts of (LiCl - KCl) + (LiD + LiF) at the Titanium Electrode during Electrolysis

NASA Astrophysics Data System (ADS)

Tsvetkov, S. A.; Filatov, E. S.; Khokhlov, V. A.

2005-12-01

The electrochemical cell and a technique for precision calorimetric measurements has been developed. Experiments with molten salts containing lithium deuteride were carried out. Calorimetric measurements made on the titanium electrode during experiments. Measurements were made in an inert atmosphere of helium and in an atmosphere of deuterium at various density of an electrolysis current. Excess heat was obtained on the titanium electrode in a deuterium atmosphere during electrolysis. An x-ray diffraction analysis was made on the used titanium electrode. The analysis of the results obtained is discussed.

Numerical Modeling of Electrode Degradation During Resistance Spot Welding Using CuCrZr Electrodes

NASA Astrophysics Data System (ADS)

Gauthier, Elise; Carron, Denis; Rogeon, Philippe; Pilvin, Philippe; Pouvreau, Cédric; Lety, Thomas; Primaux, François

2014-05-01

Resistance spot welding is a technique widely used by the automotive industry to assemble thin steel sheets. The cyclic thermo-mechanical loading associated with the accumulation of weld spots progressively deteriorates the electrodes. This study addresses the development of a comprehensive multi-physical model that describes the sequential deterioration. Welding tests achieved on uncoated and Zn-coated steel sheets are analyzed. Finite element analysis is performed using an electrical-thermal-metallurgical model. A numerical experimental design is carried out to highlight the main process parameters and boundary conditions which affect electrode degradation.

Ion Monitoring

DOEpatents

Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore

2003-11-18

The apparatus and method provide a technique for significantly reducing capacitance effects in detector electrodes arising due to movement of the instrument relative to the item/location being monitored in ion detection based techniques. The capacitance variations are rendered less significant by placing an electrically conducting element between the detector electrodes and the monitored location/item. Improved sensitivity and reduced noise signals arise as a result. The technique also provides apparatus and method suitable for monitoring elongate items which are unsuited to complete enclosure in one go within a chamber. The items are monitored part by part as the pass through the instrument, so increasing the range of items or locations which can be successfully monitored.