Search results for "Microelectrode"

Oil-in-Water fL Droplets by Interfacial Spontaneous Fragmentation and Their Electrical Characterization

2019

Inkjet printing is here employed for the first time as a method to produce femtoliter-scale oil droplets dispersed in water. In particular, picoliter-scale fluorinated oil (FC40) droplets are printed in the presence of perfluoro-1-octanol surfactant at a velocity higher than 5 m/s. Femtoliter-scale oil droplets in water are spontaneously formed through a fragmentation process at the water/air interface using minute amounts of nonionic surfactant (down to 0.003% v/v of Tween 80). This fragmentation occurs by a Plateau-Rayleigh mechanism at a moderately high Weber number (10(1)). A microfluidic chip with integrated microelectrodes allows droplets characterization in terms of number and diamet…

Formation and Rupture of Schottky Nanocontacts on ZnO Nanocolumns

2007

In this paper, the electrical transport and mechanical properties of Pt/ZnO Schottky nanocontacts have been studied simultaneously during the formation and rupture of the nanocontacts. By combining multidimensional conducting scanning force spectroscopy with appropriated data processing, the physical relevant parameters (the ideality factor, the Schottky barrier height, and the rupture voltage) are obtained. It has been found that the transport curves strongly depend on the loading force. For loading forces higher than a threshold value, the transport characteristics are similar to those of large-area Schottky contact, while below this threshold deviations from strictly thermionic emission …

Simulation of pH-controlled dissolution of aluminium based on a modified Scanning Electrochemical Microscope experiment to mimic localized trenching …

2011

Abstract Some constituent intermetallic (IMPs) particles at the surface of aluminium alloys are considered as preferential sites for the initiation of structural corrosion resulting in localized trenching around the particles and the surrounding Al matrix. In this work, a modified scanning electrochemical microscope (SECM) experiment was used to induce such phenomena via a local alcalinisation on 200 nm thick aluminium coatings promoting their local dissolution in an aerated 0.1 M NaCl electrolyte. The local alcalinisation was induced by the oxygen reduction reaction on the tip of a SECM which mimics the surface of an isolated IMP. From a phenomenological point of view, reproducible cylindr…

Electrogeneration of Diiodoaurate in Dimethylsulfoxide on Gold Substrate and Localized Patterning

2016

International audience; A localized etching of gold surface by scanning electrochemical microscope technique is presented where a dimethylsulfoxide-based electrolyte charged with iodine is used. The electrogenerated triiodide ion at the platinum ultramicroelectrode tip (feedback mode) acts as an oxidant for gold surface. The effects of electrode diameter and the bias time have been investigated. The approach curve method was used to hold the electrode tip close to the gold surface. A scanning electron microscope is used to observe the etched gold surfaces where disk-shaped dots are generated. The diameter of these holes depends directly on the Pt electrode diameter and the bias time.

Influence of growth, measuring conditions, and cell types on oxygen tensions in multicell tumor spheroids determined by microelectrodes

1981

Polarographic and voltammetric methods for the determination of elements

1978

Measurements of the correlations between current, voltage and time, when microelectrodes are used, yield qualitative and quantitative information on the elemental composition of the solution investigated, if the method of measurement is properly chosen. Instrumental development today makes it possible, even at electrodes which make measurement difficult, such as the classical dropping mercury electrode, to obtain more reliable information on detection limits and number of elements detectable, by taking into account the functional interdependence of interference parameters and signal generation. Simultaneous determination of several components is possible, especially with non-linear a. c. po…

Local H2-Clearance and PO2-Measurements in Microareas of the Brain Tissue in Rats

1969

Lubbers [5], as well as others, measured the oxygen partial pressure of the exposed cerebral cortex by means of small platinum microelectrodes. They registered low pO2 values between 1 and 3 mmHg in certain areas of the cortex, despite the fact that the EEG was of normal pattern. In order to decide whether these low pO2 values are a result of low rCBF, or high local oxygen consumption of brain tissue, we developed a new method. Using the same platinum needle, we measured both local pO2 values and H2-clearance curves in microareas of the brain tissue. Cater and Silver [2], Lubbers [4, 5], and others used glass-insulated platinum microelectrodes to measure local pO2. Further, Aukland, Bower a…

Problems Involved in the Measurement of Microcirculation by Means of Microelectrodes

1973

Until now, the interpretation of local wash-out curves, measured by means of microelectrodes and using hydrogen as diffusible indicator, is an unsettled problem. It has been shown, that even the simultaneous measurement by means of a surface-multiwire-Pt-microelectrode at the isolated and hemoglobin-free perfused rat liver yields different wash-out curves (4). These differences occur with regard to the height of the curves as well as to the moment, when the maximum of the indicator’s concentration is seen by the microelectrode. Fig.1 represents four simultaneously recorded curves. The difference in sensitivity of each micro-electrode has been compensated by a computer. The fast curve corres…

EFFECT OF MICROENCAPSULATION ON OXYGEN DISTRIBUTION IN ISLETS ORGANS

1994

In islet transplantation, limitation of oxygen supply may restrict graft function, particularly when encapsulated tissue is used. Therefore, oxygen tensions (PO2) in isolated islet organs (Brockmann bodies) of Osphronemus gorami were measured. In a thermostatically (37 degrees C) controlled measuring chamber, PO2 values were recorded at subsequent microelectrode positions on a radial track toward the center of the organ. In 2 independent groups, we studied the effect of fluid convection (n = 12) and microencapsulation (n = 12). In both groups, sigmoidal PO2 profiles were found, which permit differentiation in an oxygen-depleted zone surrounding the surface, a steep decline inside the tissue…

A method for rapid implantation of multielectrode systems.

1991

The implantation of several chronic electrodes at the same time was needed for the studies in which both evoked slow potential and multiple unit neural activity of different brain sites were recorded during classical conditioning in freely moving cats. The recording electrodes were made of 25-75 microns insulated stainless steel or nichrome wires which were inserted into a thin hypodermic needle of a fixed, calibrated length. The fast implantation system described here is based on the use of a stereotaxic frame as a stand for a drill and as a support for an electrode holder with which the electrodes were implanted through precision holes drilled directly according to the coordinates of the …