Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-11-22
1997-09-23
Bell, Bruce F.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204403, 204416, 204418, 204409, 422 681, 422 8201, 422 8202, 422 8203, 422 98, G01N 2726
Patent
active
056700318
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/DE 94/00598 published May 21, 1994.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention, in general, relates to an electrochemical sensor, and, more particularly, to an electrochemical sensor of the kind provided with a plurality of interdigitated micro-electrodes supported by a substrate.
Electrochemical sensors having interdigitated (i.e. interposed in the manner of fingers) micro-electrodes are usable in chemical analytics and process controls in various fields such as biotechnology, environmental protection and public health. They have small diffusion lengths for electrochemically active molecules, since the distances between individual finger-like electrode areas lie in the range of .mu.m or sub-.mu.m.
2. Description of the Prior Art
Electrochemical sensors with miniaturized planar electrodes with geometries in excess of 2 .mu.m have hitherto been known. They are fabricated by thin-film technologies and are used as transductors for detecting chemical and biological substances.
Electrode geometries between 20 and 100 .mu.m provide detection characteristics like those attainable with conventional thin-wire electrodes (vide M. Suda et al., Proceedings Second World Congress on Biosensors, Geneva, Switzerland 1992, p. 400; N. F. Sheppard, Jr. et al., Anal. Chem. 1993, 65, 1199-1202).
Arrangements comprising two parallel thin metallic film strips 5 .mu.m wide, for measuring conductivity are known from L. D. Watson (Biosensors 3, 1987/88, 101-115).
For defining voltage profiles, T. Matsue et al. (Anal. Chem. 62, 1990, 407-409) are using an arrangement of sixteen electrodes 1 mm long and 0.1 mm wide.
An arrangement of spherical electrodes of micrometer dimensions in the insulation of a metallic surface has been described by B. Ross et al. (Sensors & Actuators B7, 1992, 758-762). Because of the electrical parallel interconnection of the micro-electrodes a measurement signal is generated only in voltammetric and chronoamperometric measurements.
I. Fritsch-Faules et al. (Anal. Chem. 64, 1992, 1118-1127) are using an arrangement of electrodes 4 .mu.m wide and spaced 8 .mu.m from each other, to define concentration profiles of redox centers in polymeric films.
An electrochemical sensor having a pair of interdigitated micro-electrodes is known from O. Niwa et al. (Anal. Chem. 62, 1990, 447-452). Amplification effects by electrochemical recyclization of reversible redox molecules was first shown with such sensors of structural widths between 0.75 and 10 .mu.m.
All of the described electrodes were used in stationary measuring processes.
SUMMARY OF THE INVENTION
It is a task of the invention to provide an electrochemical sensor which makes electrochemical detection of molecules possible at a higher detection sensitivity and which offers enhanced possibilities of use for detecting chemical reaction processes.
This task is solved, in general, by an electrochemical sensor provided with two or more pairs of interdigitated micro-electrodes of structural widths less than 1 .mu.m. The micro-electrodes are arranged as an array on a substrate. The individual pairs may be energized independently of each other with electric potentials, and the measurement effects at the individual electrodes can be drained or derived independently. In the present context, measurement effects are understood to be, in particular, amperometric, potentiometric or impedimetric effects. The preferred planar substrate used is glass, sapphire, silicon or polymers, with the electrodes being applied by planar technology. The fine geometry structuring of the electrodes results in spaces (e.g. distances of about 700 nm) between the interdigitated micro-electrodes, i.e. electrodes arranged in a finger-like pattern, which are small relative to the distances traveled by the molecules to be detected, in the measuring time. Thus, it becomes possible electrochemically to capture the same molecule several times, as, for example, for repeatedly oxidizing and reducing it before it diffuses out of the range of th
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Sensors and Actuators, vol. 15 No. 4, Dec. 1988, Lausanne, pp. 337-345 Sinclair Yee, et al. "Miniature Liquid Junction Reference Electrode with Micromachined Silicon Activity".
Analytical Chemistry, vol. 62, 1990, Columbus, OH; pp. 407-409 Tomokazu Matsue et al. "Multichannel Electrochemical Detection System for Flow Analysis" No month available.
Analytical Chemistry, vol. 64, 1992, Columbus, OH., pp. 1118-1127, I. Fritsch-Faules, et al. "Use of Microelectrode Arrays to Determine Concentration Profiles of Redox Centers in Polymer Films" No month available.
Analytical Chemistry, vol. 62, 1990, Columbus, OH., pp. 447-452; Osamu Niwa et al. "Electrochemical Behavior of Reversible Redox Species at Interdigitated Array Electrodes with Different Geometries: Consideration of Redox Cycling and Collection Efficiency" No month available.
Sensors and Actuators, B7, 1992; pp. 758-762; B. Ross et al. No month available.
Hintsche Rainer
Paeschke Manfred
Schnakenberg Uwe
Wollenberger Ulla
Bell Bruce F.
Fraunhofer-Gesellschaft zur angewandten Forschung e.V.
Hormann Karl
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