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Electrochemical measurement of endogenously produced nitric oxide in brain slices using Nafion/o-phenylenediamine modified carbon fiber microelectrodes

Ferreira, Nuno R.; Ledo, Ana; Frade, João G.; Gerhardt, Greg A.; Laranjinha, João; Barbosa, Rui M.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
27.26%
The role of nitric oxide (NO) as a regulatory diffusible molecule in the brain requires the evaluation of its concentration dynamics. In this work, we have developed microelectrodes suitable for real time electrochemical measurements of NO in vitro. Nafion and o-phenylenediamine were used to modify the surface of carbon fiber microelectrodes (8 [mu]m diameter; [approximate]100 [mu]m tip length). Coating with Nafion was done at 170 °C and the o-phenylenediamine solution was electropolimerized on the carbon surface. NO peak potential (+0.78 ± 0.03 V versus Ag/AgCl) was determined by square wave voltammetry with NO solutions prepared from the-generating compound diethylenetriamine/nitric oxide (DETA/NO). Microelectrodes were calibrated by amperometry at a potential of +0.90 V versus Ag/AgCl. They showed good sensitivity (954 ± 217 pA/[mu]M; n = 6) and linearity to NO in the concentration range of 100-1000 nM. They were also characterized in terms of detection limit (6 ± 2 nM, n = 4), response time at 50% (1 s), and selectivity against interferents, such as nitrite (780 ± 84:1, n = 6), ascorbic acid (750 ± 187:1, n = 6) or dopamine (18 ± 2:1, n = 6). Injections of 1 mM l-glutamate, 1 mM l-arginine...

Métodos para fabricação de microeletrodos visando a detecção em microambientes; Methods for fabrication of microelectrodes towards detection in microenvironments

PAIXÃO, Thiago R. L. C.; BERTOTTI, Mauro
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
POR
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37.19%
Analysis at microenvironments, like single cells or in minute volumes (nL), is an area of great interest for analytical and biological sciences. Measurements at these experimental conditions demand analytical tools (microelectrodes) capable of monitoring with rapid response, good resolution and minimal perturbation of the system. The major drawbacks in producing these microscopic electrodes have been largely overcome, principally due to the development of new fabrication methods. In this review, these procedures are described with emphasis to those devoted to the construction of microelectrodes for application in microenvironments. Examples of our efforts to use these devices as effective electrochemical sensors are also addressed.; FAPESP; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); CNPq

Fabricação de microeletrodos para aplicações em microscopia eletroquímica de varredura; Fabrication of microelectrodes for applications in scanning electrochemical microscopy

Castro, Pollyana Souza
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/08/2011 PT
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37.19%
No presente trabalho, microeletrodos de platina foram fabricados e empregados juntamente com a técnica de Microscopia Eletroquímica de Varredura (Scanning Electrochemical Microscopy - SECM) para a obtenção de informações a respeito da erosão ácida do esmalte dentário. Em uma etapa inicial do projeto, um procedimento de fabricação de microeletrodos utilizando o equipamento Micropipette Puller foi desenvolvido. A selagem e o polimento da área ativa dos dispositivos foram consideradas etapas críticas do processo de construção. Uma bomba a vácuo foi empregada durante a fabricação dos dispositivos, o que aumentou a eficiência da selagem do vidro sobre a microfibra. Os parâmetros do equipamento necessários à fabricação dos dispositivos foram otimizados e desta forma obteve-se uma metodologia reprodutível e eficiente. Assim, microeletrodos de diversos materiais e dimensões foram construídos e avaliados quanto à utilização em SECM. Uma metodologia alternativa para a redução no tamanho da ponta de prova foi proposta. Um polimento cuidadoso na ponta de prova foi feito e através de comparações entre Curvas de Aproximação teóricas e experimentais, chegou-se a microeletrodos com RG (razão raio do vidro e raio do microeletrodo) próximos de 15. Em uma segunda etapa do projeto...

Avaliação da corrosividade do biodiesel para diferentes metais empregando microeletrodos clássicos e arranjos de microeletrodos; Evaluation of biodiesel corrosiveness for diferent metals using classic microelectrodes and arrangements of microelectrodes

Arenas, Beatriz Eugenia Sanabria
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/09/2014 PT
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37.36%
Um dos principais problemas no emprego do biodiesel como combustível de automóveis é a corrosão que ele pode provocar nos motores, devido à facilidade com que pode degradar. A natureza corrosiva do biodiesel é relacionada com a presença de água, ácidos graxos livres, ions metálicos, impurezas, a incidência da luz, a temperatura e a presença de insaturações na cadeia de alquil ésteres. Na atualidade existem poucos trabalhos na literatura sobre a corrosão dos metais em contato com biodiesel e a maioria deles têm um enfoque mais qualitativo que quantitativo. O maior desafio para avaliar a corrosividade do biodiesel mediante técnicas eletroquímicas é sua baixa condutividade. A espectroscopia de impedância eletroquímica (EIE) é uma técnica sensível que tem sido empregada para estudar meios resistivos como o etanol, por muitos anos. No entanto, os experimentos são difíceis assim como a análise dos resultados, principalmente pelo desenvolvimento da queda ôhmica no meio, devido à alta resistividade do meio ao fluxo da corrente elétrica. Os microeletrodos têm sido empregados em várias pesquisas em eletroquímica e têm apresentado algumas vantagens com respeito aos eletrodos de tamanhos convencionais. O principal benefício é a redução da queda ôhmica em meios resistivos...

Arrays of gold microelectrodes made from split integrated circuit chips

Nascimento, V. B.; Augelli, M. A.; Pedrotti, J. J.; Gutz, IGR; Angnes, L.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 335-339
ENG
Relevância na Pesquisa
37.09%
A simple and inexpensive way to fabricate arrays of gold microelectrodes is proposed. Integrated circuit chips are sawed through their middle, normal to the longest axis, leading to destruction of the silicon circuit and rupture of the gold wires that interconnect it with the external terminals. Polishing the resulting rough surface converts the tips of the wires embedded in the chip halves into arrays of gold microdisks of about 25 mu m diameter. The number of active microelectrodes (MEs), of an array depends on the number of pins in the chip, n, being typically (n/2)-4. These MEs can be used individually or externally interconnected in any combination. X-ray images of the chips and micrographs of the resulting surface of the polished arrays have revealed variable distances between neighbor MEs, which are, however, larger than 10 times the radius of the disks. This feature of the MEs prevents diffusional cross-talk between electrodes. The use of these microdisk electrodes for analytical purposes exhibits sigmoidal voltammograms, and chronoamperometric experiments confirm the nonlinear i vs. t(1/2) plots, typical for processes where radial diffusion prevails. Satisfactory uniformity was observed for the response of each electrode of an array...

Amperometric differential determination of ascorbic acid in beverages and vitamin C tablets using a flow cell containing an array of gold microelectrodes modified with palladium

Matos, R. C.; Augelli, M. A.; Pedrotti, J. J.; Lago, C. L.; Angnes, L.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 887-890
ENG
Relevância na Pesquisa
36.94%
A simple and attractive method for quantification of ascorbic acid (AA) in beers, soda, natural juices and commercial vitamin C tablets was achieved by combining Bow injection analysis and amperometric detection. An array of gold microelectrodes electrochemically modified by deposition of palladium was employed as working electrode which was almost unaffected by fouling effects. Ascorbic acid was quantified in beverages and vitamin tablets using amperometric differential measurements. This method is based on three steps involving the flow injection of: 1) the sample plus a standard addition of AA, 2) the pure sample, and 3) the enzymatically-treated sample. The enzymatic treatment was carried out with Cucumis sativus tissue, which is a rich source of ascorbate oxidase, at pH 7. The calibration plots for freshly prepared ascorbic acid standards were very linear in the concentration range of 0.18-1.8 mg L-1 with a relative standard deviation (RSD) < 1%, while for real samples the deviations were between 2.7% to 8.9%.

Avaliação da corrosividade do etanol combustível utilizando arranjo de microeletrodos; Corrosion evaluation in ethanol fuel using microelectrodes array

Camila Molena de Assis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/03/2012 PT
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37.19%
Neste trabalho foi estudada a corrosão do metal cobre em meio alcoólico utilizando um arranjo de microeletrodos construídos por fotolitografia. Foi avaliada a influência da área do arranjo de microeletrodos na queda ôhmica e no comportamento da resistência do meio eletrolítico. Os resultados obtidos foram plotados, analisados e comparados com metodologias teóricas obtendo uma boa concordância. Conclui-se que a resistência do meio aumenta, a medida que diminui-se o diâmetro do microeletrodo quando considerado um eletrodo unitário, no entanto, a resistência diminui com o diâmetro do microeletrodo quando considerado num arranjo. Em relação à queda ôhmica, esta diminui com a diminuição do diâmetro e através da compensação da queda ôhmica observa-se que as compensações tiveram menor efeito nos microeletrodos de menor área.; This work presents an investigation on the corrosion of cooper metal, using a microelectrode array building using lithography technique. The influence of microelectrode array area was investigated on the ohmic drop and resistance of ethanol. The results were then compared with existing theoretical methodologies and good agreements were found. It was concluded that resistance of ethanol increases with decreases single microelectrodes diameter and decreases with decreases array microelectrodes diameter. The ohmic drop decreases with diameter decreases and the ohmic drop compensation had the smallest effect on microelectrodes with smaller area.

Assessement of Candida utilis growth by voltammetric reduction of acids using microelectrodes

Rodrigues, Astride; Geraldo, M. Dulce; Bento, M. Fátima; Cássio, Fernanda
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /05/2004 ENG
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36.94%
A voltammetric method for the evaluation of the microbial growth using platinum microelectrodes is proposed. This new method is based on the electrochemical reduction of acids produced by the yeast Candida utilis in liquid medium containing glucose as carbon and energy source and ammonium ions as nitrogen source. Current intensities, from linear sweep and square wave voltammetry, were compared with the corresponding values of absorbance at 640 nm (A640nm) resulting from the light scattering of cell suspensions. The equivalence between turbidimetry and electrochemical measurements was checked in experiments performed in growing cultures and in cell suspensions prepared from the dilution of cell cultures. The growth curves defined by either current intensities (IP or IL) or A640nm measurements were similar and displayed characteristic growth phases in a closed system. Exponential growth rates estimated both from turbidimetry and voltammetric techniques were the same.; POCTI/QUI/39525/2001.

Glass pipette-carbon fiber microelectrodes for evoked potential recordings

Moraes,M.F.D.; Garcia-Cairasco,N.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/1997 EN
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37.09%
Current methods for recording field potentials with tungsten electrodes make it virtually impossible to use the same recording electrode also as a lesioning electrode, for example for histological confirmation of the recorded site, because the lesioning procedure usually wears off the tungsten tip. Therefore, the electrode would have to be replaced after each lesioning procedure, which is a very high cost solution to the problem. We present here a low cost, easy to make, high quality glass pipette-carbon fiber microelectrode that shows resistive, signal/noise and electrochemical coupling advantages over tungsten electrodes. Also, currently used carbon fiber microelectrodes often show problems with electrical continuity, especially regarding electrochemical applications using a carbon-powder/resin mixture, with consequent low performance, besides the inconvenience of handling such a mixture. We propose here a new method for manufacturing glass pipette-carbon fiber microelectrodes with several advantages when recording intracerebral field potentials

In situ monitoring of electroactive species by using voltammetry at microelectrodes

Daniele,Salvatore; Baldo,M. Antonietta; Bragato,Carlo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2002 EN
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36.94%
Mercury coated platinum microelectrodes were employed for the in situ determination, in soils and porewater of sediments, of redox key species of environmental interest. Sand samples were considered as soil model for the in situ detection of oxygen. Direct measurements of sulphide were performed in anoxic sediments collected in the Lagoon of Venice. An investigation on the interaction among heavy metals, sulphide and solid particles in pore-water extracted from the sediments was also performed. For the quantification of the various electroactive species examined, calibrantioless procedures were employed.

Electrochemical properties of Na+- and K+-selective glass microelectrodes.

Lee, C O
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1979 EN
Relevância na Pesquisa
27.5%
Electrochemical properties of Na+-selective glass microelectrodes were studied and compared with those of K+-selective glass microelectrodes. The selectivity of Na+-selective glass microelectrodes depended on the ion concentration of test solutions. With aging, resistance of Na+-selective microelectrodes increased and their selectivity for Na over K decreased. Na+-selective microelectrodes potential measured in NaCl solution remained constant with aging, while the potential measured in KCl solution decreased and became more positive. The changes in resistance and potential of Na+-selective microelectrodes may be due to the effects of the less mobile cation, i.e., H+ or K+ on the Na ion exchange in the Na-sensing region. The results indicate that Na+-selective microelectrodes must be used as soon after filling as possible. The selectivity of Na+-selective microelectrodes increased with increase of the sensitive exposed-tip length, whereas their response time became slow due to a large recessed volume, indicating requirement of an optimum exposed-tip length for intracellular applications. The changes in the properties of Na+-selective glass microelectrodes with aging contrasted with those of K+-selective glass microelectrodes in which resistance decreased and K+-selectivity increased. The K+-selective microelectrodes required aging before use for a high selectivity and low resistance. The K+-selective microelectrodes with low resistance after sufficient aging can be used without insulation to measure K+ and Na+ activities in aqueous solutions. The different properties between Na+- and K+-selective microelectrodes are understandable...

An Array of Microactuated Microelectrodes for Monitoring Single-Neuronal Activity in Rodents

Muthuswamy, Jit; Okandan, Murat; Gilletti, Aaron; Baker, Michael S.; Jain, Tilak
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/2005 EN
Relevância na Pesquisa
27.36%
Arrays of microelectrodes used for monitoring single-and multi-neuronal action potentials often fail to record from the same population of neurons over a period of time for several technical and biological reasons. We report here a novel Neural Probe chip with a 3-channel microactuated microelectrode array that will enable precise repositioning of the individual microelectrodes within the brain tissue after implantation. Thermal microactuators and associated microelectrodes in the Neural Probe chip are microfabricated using the Sandia’s Ultraplanar Multi-level MEMS Technology (SUMMiTV) process, a 5-layer polysilicon microma-chining technology of the Sandia National labs, Albuquerque, NM. The Neural Probe chip enables precise bi-directional positioning of the microelectrodes in the brain with a step resolution in the order of 8.8μm. The thermal microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation in either direction was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multi-unit activity. Single unit recordings were obtained from the somatosensory cortex of adult rats over a period of three days demonstrating the feasibility of this technology. Further optimization of the microelectrode insulation and chip packaging will be necessary before this technology can be validated in chronic experiments.

Magnetron sputtered diamond-like carbon microelectrodes for on-chip measurement of quantal catecholamine release from cells

Gao, Yuanfang; Chen, Xiaohui; Gupta, Sanju; Gillis, Kevin D.; Gangopadhyay, Shubhra
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2008 EN
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27.36%
Carbon electrodes are widely used in electrochemistry due to their low cost, wide potential window, and low and stable background noise. Carbon-fiber electrodes (CFE) are commonly used to electrochemically measure “quantal” catecholamine release via exocytosis from individual cells, but it is difficult to integrate CFEs into lab-on-a-chip devices. Here we report the development of nitrogen doped diamond-like carbon (DLC:N) microelectrodes on a chip to monitor quantal release of catecholamines from cells. Advantages of DLC:N microelectrodes are that they are batch producible at low cost, and are harder and more durable than graphite films. The DLC:N microelectrodes were prepared by a magnetron sputtering process with nitrogen doping. The 30 μm by 40 μm DLC:N microelectrodes were patterned onto microscope glass slides by photolithography and lift-off technology. The properties of the DLC:N microelectrodes were characterized by AFM, Raman spectroscopy and cyclic voltammetry. Quantal catecholamine release was recorded amperometrically from bovine adrenal chromaffin cells on the DLC:N microelectrodes. Amperometric spikes due to quantal release of catecholamines were similar in amplitude and area as those recorded using CFEs and the background current and noise levels of microchip DLC:N electrodes were also comparable to CFEs. Therefore...

Long-Term Neural Recordings Using MEMS Based Movable Microelectrodes in the Brain

Jackson, Nathan; Sridharan, Arati; Anand, Sindhu; Baker, Michael; Okandan, Murat; Muthuswamy, Jit
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 18/06/2010 EN
Relevância na Pesquisa
27.32%
One of the critical requirements of the emerging class of neural prosthetic devices is to maintain good quality neural recordings over long time periods. We report here a novel MEMS (Micro Electro Mechanical Systems) based technology that can move microelectrodes in the event of deterioration in neural signal to sample a new set of neurons. Microscale electro-thermal actuators are used to controllably move microelectrodes post-implantation in steps of approximately 9 μm. In this study, a total of 12 movable microelectrode chips were individually implanted in adult rats. Two of the twelve movable microelectrode chips were not moved over a period of 3 weeks and were treated as control experiments. During the first 3 weeks of implantation, moving the microelectrodes led to an improvement in the average signal to noise ratio (SNR) from 14.61 ± 5.21 dB before movement to 18.13 ± 4.99 dB after movement across all microelectrodes and all days. However, the average root-mean-square values of noise amplitudes were similar at 2.98 ± 1.22 μV and 3.01 ± 1.16 μV before and after microelectrode movement. Beyond 3 weeks, the primary observed failure mode was biological rejection of the PMMA (dental cement) based skull mount resulting in the device loosening and eventually falling from the skull. Additionally...

Highly Doped Polycrystalline Silicon Microelectrodes Reduce Noise in Neuronal Recordings In Vivo

Saha, Rajarshi; Jackson, Nathan; Patel, Chetan; Muthuswamy, Jit
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.36%
The aims of this study are to 1) experimentally validate for the first time the nonlinear current-potential characteristics of bulk doped polycrystalline silicon in the small amplitude voltage regimes (0–200 μV) and 2) test if noise amplitudes (0–15 μV) from single neuronal electrical recordings get selectively attenuated in doped polycrystalline silicon microelectrodes due to the above property. In highly doped polycrystalline silicon, bulk resistances of several hundred kilo-ohms were experimentally measured for voltages typical of noise amplitudes and 9–10 kΩ for voltages typical of neural signal amplitudes (>150–200 μV). Acute multiunit measurements and noise measurements were made in n = 6 and n = 8 anesthetized adult rats, respectively, using polycrystalline silicon and tungsten microelectrodes. There was no significant difference in the peak-to-peak amplitudes of action potentials recorded from either microelectrode (p > 0.10). However, noise power in the recordings from tungsten microelectrodes (26.36 ± 10.13 pW) was significantly higher (p < 0.001) than the corresponding value in polycrystalline silicon microelectrodes (7.49 ± 2.66 pW). We conclude that polycrystalline silicon microelectrodes result in selective attenuation of noise power in electrical recordings compared to tungsten microelectrodes. This reduction in noise compared to tungsten microelectrodes is likely due to the exponentially higher bulk resistances offered by highly doped bulk polycrystalline silicon in the range of voltages corresponding to noise in multiunit measurements.

Electrical Characterization of 3D Au Microelectrodes for Use in Retinal Prostheses

Lee, Sangmin; Ahn, Jae Hyun; Seo, Jong-Mo; Chung, Hum; Cho, Dong-Il “Dan”
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 17/06/2015 EN
Relevância na Pesquisa
27.45%
In order to provide high-quality visual information to patients who have implanted retinal prosthetic devices, the number of microelectrodes should be large. As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range. In order to improve the trade-off envelope between the number of microelectrodes and the current injection characteristics, a 3D microelectrode structure can be used as an alternative. In this paper, the electrical characteristics of 2D and 3D Au microelectrodes were investigated. In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated. Interface impedances were measured and similar dynamic ranges were obtained for both 2D and 3D Au microelectrodes. These results indicate that more electrodes can be implemented in the same area if 3D designs are used. Furthermore, the 3D Au microelectrodes showed substantially enhanced electrical durability characteristics against over-injected stimulation currents, withstanding electrical currents that are much larger than the limit measured for 2D microelectrodes of similar area. This enhanced electrical durability property of 3D Au microelectrodes is a new finding in microelectrode research...

Neutral carrier Na+- and Ca2+-selective microelectrodes for intracellular application.

Dagostino, M; Lee, C O
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1982 EN
Relevância na Pesquisa
27.43%
Na+- and Ca2+-selective microelectrodes were made with Simon's neutral carrier ETH 227 and ETH 1001, respectively, and their properties were studied for intracellular application. The kNaK (selectivity coefficient for Na+ with respect to K+) values of the Na+-selective microelectrodes were in the range of 0.01-0.02, which is comparable to those of recessed-tip Na+-selective glass microelectrodes. The kNaMg values of the microelectrodes were approximately 0.005 so that the interference by intracellular Mg2+ levels could be negligible. The kNaCa values were approximately 2 and the Na+-selective microelectrodes were more selective to Ca2+ than Na+. This indicates that their intracellular application requires special care to handle Ca2+ interference under certain conditions. The kNaK, kNaMg, and kNaCa values did not depend significantly on the methods used for their determination or on the ion activity levels tested. The Nicolsky equation described well the microelectrode potentials in the mixed solutions of NaCl (1-100 mM) and KCl. Potential and resistance of the microelectrodes were stable for a long period and their response time was fast. The results indicate that the Na+-selective microlectrodes are suitable for measurements of intracellular Na ion activities. Ca2+-selective microelectrode potentials at Ca2+ concentrations lower than 10(-4) M changed significantly for the first 2-3 h and then became fairly stable. The rate of the potential change was dependent on the column length of the Ca2+-selective liquid filled. Potentials of the microelectrodes varied from 10-20 mV for Ca2+ between 10(-7) and 10(-6) M concentrations...

Electrostatic Microactuators for Precise Positioning of Neural Microelectrodes

Muthuswamy, Jit; Okandan, Murat; Jain, Tilak; Gilletti, Aaron
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2005 EN
Relevância na Pesquisa
27.4%
Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V™ (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 μm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation...

Noves tecnologies de capa prima en la fabricació de microelèctrodes implantables per interfases neuroelectròniques

Haro Marmolejo, Carmen de
Fonte: Bellaterra : Universitat Autònoma de Barcelona, Publicador: Bellaterra : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis Formato: application/pdf; application/pdf; application/pdf
Publicado em //2004 CAT; CAT
Relevância na Pesquisa
37.32%
Consultable des del TDX; A portada: Programa de Ciències de Materials; Títol obtingut de la portada digitalitzada; Els materials biocompatibles tenen un camp d'aplicació molt important entre els dispositius biomèdics, entre els quals es vol destacar el seu ús en el camp dels implants. Aquests implants poden realitzar funcions estructurals o com actuadors, com es el cas dels microelèctrodes implantables, treballant en modes d'estimulació o de registre. En el present treball s'ha investigat l'ús de materials biocompatibles amb tecnologia en capa prima per la fabricació de microelèctrodes implantables de tipus cuff o envolvents de forma semi-automatitzada. S'ha estudiat la realització d'aquests interfases neuroelectròniques amb poliimida i platí. El disseny i definició de les estructures que formen el microelèctrode s'han optimitzat per l'encapsulació final del dispositiu realitzada amb silicona. S'han determinat el mecanisme i la cinètica de corrosió del platí durant els processos d'estimulació neural i la viabilitat d'augmentar el temps de vida dels dispositius mitjançant la deposició electroquímica de material transductor. Com alternatives a l'ús de la poliimida i del platí en la realització de microelèctrodes implantables s'han estudiat diferents materials dielèctrics compatibles amb tecnologia de capa prima...

Study of Molecules with Multiple Redox Centers Using Differential Staircase Voltammetry at Spherical Electrodes and Microelectrodes

López-Tenés,Manuela; Serna,Carmen; Moreno,Marién M.; Molina,Ángela
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
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36.94%
The study of the reversible reduction/oxidation molecules containing multiple interacting or noninteracting redox centers has been carried out using the multipotential step technique Differential Staircase Voltammetry (DSCV). Methods to obtain the formal potentials and other characteristic parameters of the process are proposed for any interaction degree between the centers, when using spherical electrodes of any size (from planar to ultramicrospherical electrodes) and, in particular, the advantages of microelectrodes are discussed. The theoretical predictions have been tested with two experimental systems: ethyl viologen in acetonitrile and pyrazine in aqueous acid media, finding an excellent agreement between the theory and experiments. Therefore, the formal potentials for these systems have been evaluated using DSCV.