Device for gas-sensoring electrodes

Details Device for gas-sensoring electrodes Device for gas-sensoring electrodes

1999-06-07

2001-12-04

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing gas sample

C204S432000, C204S431000, C204S424000, C204S426000, C338S034000, C073S023200, C422S098000, C422S083000

Reexamination Certificate

active

06325979

ABSTRACT:

FIELD OF THE INVENTION
The present invention is based on a sensing element, in particular for an electrochemical measurement sensor for determining gas concentrations.
BACKGROUND INFORMATION
The use of planar electrode arrangements for chemical sensors is known. The gas concentrations are ascertained by determining changes in capacitance and/or conductivity in a gas-sensitive material. Also known is the three-dimensional configuration of electrode arrangements, which further increases the sensitivity of chemical sensors (Lin et al., Sensors and Actuators 5 (1991), 223 to 226). According to Lin et al., the manufacture of three-dimensional electrode arrangements is accomplished by first sputtering a metallic film onto a silicon substrate and then patterning a photoresist applied upon patterning of the photoresist, the resulting trenches are filled by electroplating, yielding a three-dimensional electrode structure as an inverse resist structure. After removal of the photoresist, the trenches, i.e, the electrode interstices, are filled with a gas-sensitive substance.
SUMMARY
The sensing element has, the advantage that the three-dimensional structure of the electrode arrangement can be used as a retaining structure for catalytically active layers and/or protective layers, and locally as a wall catalyst. Because the gas-sensitive material introduced into the trenches does not fill them up completely, it is on the one hand possible to cover over the gas-sensitive material with catalyst layers and/or protective layers, and/or on the other hand to use regions of the three-dimensional electrode arrangement which are not covered by gas-sensitive material or other layers as a wall catalyst. In the embodiments according to the present invention in which the gas-sensitive material is covered over with protective layers and/or catalytically active layers, the three-dimensional structure of the electrode arrangement acts as a retaining structure for those layers, and guarantees a stable configuration for the sensing element. In the embodiments according to the present invention in which the inner walls, i.e. the walls forming the trenches, of the three-dimensional electrode arrangement are not completely covered by the aforesaid layers which cover the gas-sensitive material, the inner walls can be used as a wall catalyst. The use of catalytic layers covering the gas-sensitive material and/or the use of the inner walls of the three-dimensional electrode arrangement as a wall catalyst is advantageous, and after “particular” in particular if the gas-sensitive material does not exhibit complete selectivity for the gas to be measured. In such a case it is particularly desirable to subject the gas mixture being investigated to catalysis, the gas to be detected being catalytically converted in such a way that it is detected by the gas-sensitive layer and determined as selectively as possible. According to the present invention, improved selectivity of the gas measurement in the gas-sensitive material can be achieved by using a catalytically active layer and/or by wall catalysis. The use of additional catalytically active layers can be dispensed with, since the conversion into the specific gas to be detected is accomplished by inner-wall catalysis.
The present invention also provides that the height h of the gas-sensitive layer introduced into the trenches, or the depth T of the trenches, can vary, although in every region of the trench the height h is to be substantially less than depth T of the trenches.


REFERENCES:
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patent: 5538620 (1996-07-01), Nikolskaja
patent: 5560810 (1996-10-01), Capetanopolous et al.
patent: 5698771 (1997-12-01), Shields et al.
patent: 5841021 (1998-11-01), De Castro et al.
patent: 0 488 352 A (1992-06-01), None
patent: 0 529 668 A (1993-03-01), None

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