Showing papers by "Gerald Urban published in 1990"
TL;DR: In this article, a 3-electrode miniaturized electrochemical cell with an outer diameter of 200 μm was produced by means of standard wet and dry etching procedures, which consists of a 100 nm thick titanium or Palladium sandwich layer on glass substrates isolated by a 3 μm silicon nitride film.
Abstract: Glucose monitoring is at present the most widespread application of the GOD/H 2 O 2 system. This paper deals with a new technique for immobilizing onto electrochemical thin-film electrode cells based on this detection principle. The thin-film structure consists of a 100 nm thick titanium—platinum or —palladium sandwich layer on glass substrates isolated by a 3 μm silicon nitride film. A three-electrode miniaturized electrochemical cell with an outer diameter of 200 μm was produced by means of standard wet and dry etching procedures. The Ag/AgCl reference electrode was produced by depositing and structuring a 1 μm thick silver film which was subsequently chlorinated by FeCl 3 . The Pt or Pd surface was oxidized electrochemically in dilute aqueous oxidizing solutions. The modified surface was derivatized with amino-organic silylating agents. The covalent coupling of glucose oxidase was carried out by introducing a substituted bifunctional 1,4-benzoquinone group between the silylated electrode surface and the enzyme. A sulfonated polymer was used to protect the enzyme layer and to modify the diffusion characteristics of the electrode.
62 citations
TL;DR: In this paper, high-sensitive and fast temperature sensors with sensitive areas of 0.14 × 0.1 mm 2 have been arranged in arrays with interdistances of 1.4 mm consisting of thin films of amorphous germanium (a-Ge) to yield a high temperature coefficient of resistance of 2%/K at room temperature.
Abstract: Highly sensitive and fast temperature sensors with sensitive areas of 0.14 × 0.1 mm 2 have been arranged in arrays with interdistances of 0.4 mm consisting of thin films of amorphous germanium (a-Ge) to yield a high temperature coefficient of resistance of 2%/K at room temperature. The sensors are passivated by a 3-μm-thick silicon nitride layer and can be placed on glass, alumina and polymer substrates. The sensor noise limits the temperature resolution of 0.1 mK whereas the 90% response time is typically 3 ms. The electrical resistance of the sensor is in the range of 10 5 ohm. A measurement current of 1 μA causes selfheating of the sensor on glass substrates of less than 0.3 mK in water. This corresponds to a measured heat resistance of 3 × 10 3 K/W. Temperature distribution measurements in the cortex of rabbits and enzyme-calorimetric determinations have been accomplished with these devices.
51 citations
TL;DR: In this paper, the authors used advanced thin-film technology employing 1,4-arenequinones substituted with at least two halogens in para positions as new agents for the immobilization of enzymes.
32 citations
TL;DR: In this paper, the electrical conductivity, density and refractive index of tetraethylgermanium in a stream of argon were determined over the range of r.f. power from 10 to 100 W.
26 citations
Patent•
04 Apr 1990
TL;DR: In this article, reactants containing amino, mercapto or hydroxy groups such as proteins, peptides, ligands, coenzymes or enzymes are immobilized on a conductive support by coupling the reactant to the support with a compound having the following formula (I or (IA): STR1## wherein X is a halogen and R1, R2 are the same or different and are X, R, COR, COOR, wherein R is C1 -C8 alkyl, COOH, CNS, N3 or CN.
Abstract: Reactants containing amino, mercapto or hydroxy groups such as proteins, peptides, ligands, coenzymes or enzymes are immobilized on a support containing amino, mercapto or hydroxy groups by coupling the reactant to the support with a compound having the following formula (I) or (IA): ##STR1## wherein X is a halogen and R1, R2 are the same or different and are X, R, COR, COOR, wherein R is C1 -C8 alkyl, COOH, CNS, N3 or CN. The support may be first reacted with the compound to produce a derivatized support which is then reacted the reactant or the reactant may be first reacted with the compound and the resultant product then reacted with the support. An electrochemical biosensor can be prepared by using a conductive support.
24 citations
Patent•
04 Apr 1990
TL;DR: In a micro-multi-electrode arrangement for electrochemical measurement and the generation of electroactive species, where the electrodes (1, 2, 3) are arranged on a carrier (5), there are an inner electrode and at least two other electrodes with the inner electrode circuited as the reference electrode and the other electrodes at least partly surrounding the inner electrodes in the projection on the carrier as discussed by the authors.
Abstract: In a micro-multi-electrode arrangement for electrochemical measurement and the generation of electroactive species, where the electrodes (1, 2, 3) are arranged on a carrier (5), there are an inner electrode (1) and at least two other electrodes (2, 3) with the inner electrode (1) circuited as the reference electrode and the other electrodes (2, 3) at least partly surrounding the inner electrode (1) in the projection on the carrier (5).
18 citations
TL;DR: A thin-film multiple-electrode probe for measuring DC potentials at eight sites with interdistances of 1 mm was constructed for the investigation of slow potential changes in deep regions of the human brain during surgery.
Abstract: A thin-film multiple-electrode probe for measuring DC potentials at eight sites with interdistances of 1 mm was constructed for the investigation of slow potential changes in deep regions of the human brain during surgery. The thin-film electrodes had to be placed on curved cylinder-shaped surgical instruments with dimensions of 2-mm diameter and 33-cm length used with the Freiburg stereotactic equipment. Several technological steps had to be introduced for solving the problems encountered. Structuring of the metal layers on curved substrates was accomplished by using flexible masks. Special feed-through technologies had to be invented in order to obtain reliable connections between the thin-film sensors and the copper wires inside the stereotactic instrument. Thin-film Ag-AgCl electrodes had to be formed in order to obtain satisfying recordings of slow potential changes below 10 Hz. Slow potential changes were recorded form different depths in interdistances of only 1 mm with the new miniaturized thin-film Ag-AgCl electrodes, and bipolar recordings with an electrode interdistance of only 3 mm clearly showed the appearance of Bereitschafts potentials. >
13 citations
TL;DR: In this article, a thin-film potassium and sodium selective sensors based on neutral carrier membranes and a way to produce them were presented, which offers cheap and simple mass production for disposable miniaturized probes.
Abstract: Thin-film potassium and sodium selective sensors based on neutral carrier membranes and a way to produce them were presented. The sensor construction offers cheap and simple mass production for disposable miniaturized probes. The main attributes of these sensors are good reproducibility in combination with a very short conditioning time after storage under dry conditions. Depending on the detailed construction the sensor potentials remain stable up to several days. The technological processes used enable integration of different sensors and are fully compatible with standard thin-film technology.
9 citations
TL;DR: In this paper, a thin-film microelectrode array was used to investigate the electro-oxidation of dopamine, DOPAC and ascorbic acid in various concentrations.
Abstract: In the in vivo investigation of neuronal activity, one important point is connected with the determination of extracellular levels of neurotransmitters. A newly designed thin-film microelectrode array was used to investigate the electro-oxidation of dopamine, DOPAC and ascorbic acid in various concentrations. The thin-film microelectrode consisted of a Ag/AgCl reference electrode in the middle of the array, circularly surrounded by an annular space gold working electrode. The counter electrode was another gold ring concentric to the working electrode. Thin-film photolithographic techniques were used for the preparation of this electrode array. With this electrode it is possible to determine the concentration of dopamine in the range between 5 and 100 μmol/l in the presence of ascorbic acid and DOPAC. The electroactive species can be distinguished by different half-wave potentials, e.g. dopamine is oxidized in a potential range between 150 and 200 mV/(Ag/AgCl) and DOPAC in a potential range between 500 and 650 mV/(Ag/AgCl). Some other substances like homovanillic acid, uric acid or serotonine are also oxidizable at the electrode.
6 citations
6 citations
Patent•
04 Apr 1990
TL;DR: In this article, a process for the immobilization of proteins, peptides, ligands, coenzymes, redox mediators, etc., on a substrate with amino, mercapto or hydroxy groups is described.
Abstract: A process is described for the immobilization of proteins, peptides, ligands, coenzymes, redox mediators, etc., on a substrate with amino, mercapto or hydroxy groups. The substrate is reacted with a compound of general formula (I) or (IA) in which X is a halogen and R1 and R2, which may be the same of different, are X, R, COR, COOR (R being a C1-C8 alkyl group), COOH, CNS, N3 or CN, and optionally dried. The peptides, proteins, coenzymes, etc., to be immobilized are then reacted with the free halogen in the ortho or para position relative to the C=0 group in the compound of general formula (I) or (IA).
Journal Article•
TL;DR: A temperature sensor array was designed in order to study local temperature variations and temperature gradients in biological samples and inserted in the optical cortex of rabbits inorder to study temperature changes during normal brain activity as well as under artificial ventilation conditions.
Abstract: A temperature sensor array was designed in order to study local temperature variations and temperature gradients in biological samples The sensor probe was inserted in the optical cortex of rabbits in order to study temperature changes during normal brain activity as well as under artificial ventilation conditions Temperature sensitive areas of 014 mm x 01 mm are arranged in a row with interdistances of 04 mm yielding high spatial resolution A temperature resolution of 01 mK and a 90% response time of maximum 3 milliseconds was obtained utilizing the high temperature dependence of 2%/K of the conductivity of vacuum evaporated germanium films The sensor is passivated by a 1 micron thick PECVD-silicon nitride layer and can be placed on glass-, alumina- and polymer substrates For brain tissue studies, in order to minimize tissue damage the temperature sensors were placed on a 01 mm thick needle-shaped glass substrate A sensor element mounted on a glass substrate and immersed in water showed a self heating of less than 5 mK due to the applied measurement current of 21 microA
Journal Article•
01 Jan 1990
TL;DR: In this article, a biosensors based on covalently immobilized enzymes have been constructed using advanced thin film technology and employing tetrahalogene 1,2- or 1,4 benzoquinones as new immobilizing agents.
Abstract: Electrochemical biosensors based on covalently immobilized enzymes have been constructed using advanced thin film technology and employing tetrahalogene 1,2- or 1,4 benzoquinones as new immobilizing agents. For special applications, thin film electrodes were combined with permeation selective, deriva-tized polypyrrole layers as sensory modifying devices.
Patent•
04 Apr 1990
TL;DR: In this paper, a Verfahren zum Immobilisieren von Proteinen, Peptiden, Liganden, Coenzymen, Redoxmediatoren od.dgl.
Abstract: Bei einem Verfahren zum Immobilisieren von Proteinen, Peptiden, Liganden, Coenzymen, Redoxmediatoren od.dgl. an einem Trager, welcher Amino-, Mercapto- oder Hydroxydgruppen aufweist, wird ein Trager mit einer Verbindung der allgemeinen Formel (I) oder (IA), in welchen X Halogen bedeutet und R1, R2 gleich oder ungleich sind und X, R, COR, COOR, worin R C1-C8 Alkyl bedeutet, COOH, CNS, N3 oder CN bedeuten, umgesetzt und gewunschtenfalls getrocknet, worauf die zu immobilisierenden Peptide, Proteine, Coenzyme od.dgl. mit dem zur C=O Gruppe ortho- oder parastandigen, freien Halogen der Verbindung der allgemeinen Formel (I) oder (IA) umgesetzt werden.